JP7503271B2 - Skin-attachable electronic device and method for manufacturing same - Google Patents

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority to U.S. Patent Application No. 16/223,541, filed December 18, 2018, and Korean Patent Application No. 10-2019-0079400, filed July 2, 2019, the entire contents of which are incorporated herein by reference.

The embodiment relates to an invention relating to an electronic device that can be attached to the skin, and more specifically, to an electronic device including a semiconductor circuit unit composed of a semiconductor element (including, for example, an active layer) and circuit components (including, for example, electrodes and/or interconnects, etc.), and a flexible patch that can be attached to the skin and is used as a substrate on which the semiconductor circuit unit is integrated, and a method for manufacturing the same. In particular, the flexible patch used as the substrate for the circuit has multiple through holes and has high breathability and strong adhesion.

As industrial and economic development makes people's lives more affluent, many modern people have a desire to go beyond simply living a healthy life to maintaining a youthful and beautiful face and body. To satisfy this desire, there is growing interest in skin-conformable electronic sensing technology (such as skin sensors) that allows people to continuously monitor their health conditions, especially their skin conditions.

In general, to obtain information about the skin, such as changes and conditions of the skin, a skin sensor is attached to the skin of a subject. However, the skin is the outermost organ of the body with the largest area, and performs various biological actions based on pores, such as sweat, sebum secretion, and volatile organic emissions, which are essential for maintaining homeostasis of the human body. The skin sensor to be attached to the skin must be manufactured taking into account the biological characteristics of the skin mentioned above.

Therefore, a high-quality skin sensor that monitors long-term health or skin conditions must have both adhesiveness and breathability as essential requirements.

Conventional skin sensors are manufactured using polymer substrates such as PI or PET, which have low permeability, and problems have been raised that when attached to the skin, they block the pores of the skin, disrupt the physiological activity of the skin, and induce inflammation and irritation. If a chemical adhesive is additionally used to strongly attach the skin sensor to the skin, the inflammation may become even worse. Infected skin loses its protective function against viruses, which can lead to secondary infections and complications. In addition, due to the elastic modulus of the polymer substrate, which is about 1,000 times larger than the skin, there is a problem that the adhesion force to the skin is very low, making it impossible to attach the sensor to the skin for a long time, or even if it is reattached, the adhesion efficiency is very low.

To overcome this, attempts have been made to develop skin sensors that have a microstructure like an octopus's suction cup or a lizard's sole, attached to a base of an elastomer such as PDMS, which has similar mechanical properties to skin. However, these microstructures are non-penetrating structures that exist only on the surface. This means that the manufacturing process is complicated and miniaturization is difficult.

In addition, when manufacturing such an elastic polymer-based skin sensor, there is a limitation in that it is difficult to integrate the circuit elements of the skin sensor on the elastic polymer because it is deformable and more flexible than the silicon substrates that are commonly used.

According to one aspect of the present invention, it is possible to provide an electronic device that includes a semiconductor circuit unit composed of circuit components and a flexible patch that can be attached to the skin and is used as a substrate on which the semiconductor circuit unit is integrated.

It is also possible to provide a method for manufacturing the electronic device.

An electronic device that can be attached to the skin according to one aspect of the present invention includes a semiconductor circuit unit - the semiconductor circuit unit includes a circuit element including one or more of an electrode and an interconnect; and an insulating layer, and a semiconductor element including an active layer; and a flexible patch configured to be attached to the skin, the flexible patch including a plurality of through holes, the insulating layer including a plurality of through holes corresponding to the plurality of through holes of the flexible patch.

In one embodiment, the plurality of through holes may include circular through holes, and the spacing between the plurality of through holes may be less than 60 μm.

In one embodiment, the plurality of through holes may further include dumbbell-shaped through holes.

In one embodiment, the plurality of through holes may include a combination of a first through hole having a first diameter and a second through hole having a second diameter, where the first diameter is greater than the second diameter, and the second through holes may be located around the first through hole.

In one embodiment, the flexible patch may be positioned on the active layer such that the multiple through holes of the flexible patch and the multiple through holes of the insulating layer match in a plane.

In one embodiment, the active layer may be made of a material including AlN or GaN.

In one embodiment, the circuit element may include a first electrode and a second electrode located opposite the first electrode. Here, the first electrode includes one or more first bars, the second electrode includes one or more second bars, the first bars extend toward the second electrode with a zigzag shape in the plane of the first bar, and the second bars extend toward the first electrode with a zigzag shape in the plane of the second bar.

In one embodiment, the zigzag shape of the first or second bar may include a hinge pattern located at a point where the extension direction of the bar changes.

In one embodiment, the flexible patch may include a first flexible layer having a first elastic modulus and a second flexible layer having a second elastic modulus, where the first elastic modulus may be lower than the second elastic modulus.

In one embodiment, the thickness _t1 of the first flexible layer and the thickness _t2 of the second flexible layer are determined according to the following mathematical formula:

[Mathematical formula]

In the above formula, t is the thickness of the flexible patch, _E1 is the elastic modulus of the first flexible layer, _E2 is the elastic modulus of the second flexible layer, R is the curvature of the flexible patch attached to the skin, _γdSkin is the dispersion component of the contact surface of the skin, _γdPatch is the dispersion component of the contact surface of the patch, _γpSkin is the polar component of the contact surface of the skin, and _γpPatch is the polar component of the contact surface of the patch.

A method for manufacturing an electronic device that can be attached to the skin according to another aspect of the present invention may include the steps of forming a sacrificial layer on a first substrate; forming a semiconductor circuit unit including a semiconductor element and a circuit element on the sacrificial layer; attaching a flexible patch including a plurality of through holes onto the semiconductor circuit; and etching the sacrificial layer to manufacture an electronic device including the semiconductor circuit unit and the flexible patch.

In one embodiment, the step of forming the semiconductor circuit unit may include the steps of forming a circuit element on the sacrificial layer, the circuit element including one or more of an electrode and an interconnect; forming an insulating layer on the circuit element, the insulating layer being formed to have a plurality of through holes corresponding to the plurality of through holes of the flexible patch; and forming an active layer on the insulating layer.

In one embodiment, the step of forming the active layer may include the steps of: forming an active layer on a second substrate; forming a stressor layer on the active layer; placing tape on the stressor layer; peeling the active layer and stressor layer from the second substrate using the tape; transferring the peeled active layer and stressor layer onto the insulating layer - the peeled active layer is transferred onto the insulating layer; and peeling the stressor layer from the active layer using the tape.

In one embodiment, the stressor layer comprises a plurality of layers,
The step of forming the stressor layer may include the steps of forming a first stressor layer on the active layer by evaporation; forming a second stressor layer on the first stressor layer by sputtering deposition; and forming a third stressor layer on the second stressor layer by sputtering deposition.

In one embodiment, the second stressor layer may be made of a material containing Al, and the third stressor layer may be made of a material containing Ni.

In one embodiment, the first stressor layer may be made of a material containing Ni or AgNi.

In one embodiment, the bonding step may further include a step of applying pressure between the flexible patch and the semiconductor circuit unit.

In one embodiment, the method for manufacturing an electronic device that can be attached to the skin may further include a step of subjecting the semiconductor circuit unit and the flexible patch to a plasma treatment before bonding.

In one embodiment, the bonding step may include placing the flexible patch on the active layer such that the multiple through holes of the flexible patch and the multiple through holes of the insulating layer match in a plane.

In one embodiment, the sacrificial layer may be made of any one of Ni, Cr, Al, and combinations thereof.

In one embodiment, the step of forming the semiconductor circuit unit includes the steps of: forming an active layer on the sacrificial layer; forming an insulating layer on the active layer; and forming circuit elements on the insulating layer, the circuit elements may include one or more of electrodes and interconnects.

According to another aspect of the present invention, a method for manufacturing an electronic device that can be attached to the skin may include the steps of forming a sacrificial layer on a first substrate; forming a semiconductor circuit unit including a circuit element and a semiconductor element on the sacrificial layer; forming a flexible patch layer on the semiconductor circuit unit; contacting a mold including grooves for forming a plurality of through holes with the flexible patch layer - the mold portion excluding the grooves penetrates the flexible patch layer; and etching the sacrificial layer to manufacture the electronic device.

In one embodiment, forming the semiconductor circuit unit on the sacrificial layer may include forming a circuit element on the sacrificial layer, the circuit element including one or more of an electrode and an interconnect; forming an insulating layer on the circuit element, the insulating layer including a plurality of through holes corresponding to the plurality of through holes of the flexible patch layer formed by the mold; and forming an active layer on the insulating layer.

In one embodiment, forming the semiconductor circuit unit on the sacrificial layer may include forming an active layer on the sacrificial layer; forming an insulating layer on the active layer, the insulating layer including a plurality of through holes corresponding to the plurality of through holes of the flexible patch layer formed by the mold; and forming a circuit element on the insulating layer, the circuit element including one or more of an electrode and an interconnect.

In one embodiment, the method for manufacturing a skin-attachable electronic device may further include forming a polyamide layer on the sacrificial layer before forming the active layer; and removing the polyamide layer after contacting the mold with the flexible patch layer.

In one embodiment, forming the active layer may include forming the active layer on the polyamide layer using a transfer structure.

In one embodiment, the method for manufacturing a skin-attachable electronic device may further include a step of patterning the active layer such that the width of the active layer is smaller than the width of the through-hole formed by the mold.

In one embodiment, the step of contacting the mold containing the plurality of grooves with the flexible patch layer may include the step of heating the flexible patch layer.

In one embodiment, the surface of the mold may be formed with grooves that can form multiple circular through holes and multiple dumbbell-shaped through holes, as well as combinations thereof.

In one embodiment, the surface of the mold may be formed with grooves that can form multiple circular through holes and multiple dumbbell-shaped through holes.

In one embodiment, the method for manufacturing a skin-attachable electronic device may further include forming one or more alignment keys for alignment of the through-die, where the alignment keys are configured to have a height, and the die further includes one or more key holes corresponding to the plane of the alignment keys.

In one embodiment, the width of the groove forming the through hole may be less than 60 μm.

In one embodiment, the step of forming the flexible patch layer may include the steps of: forming a third flexible layer having a third elastic modulus on the semiconductor circuit unit; and forming a fourth flexible layer having a fourth elastic modulus on the third flexible layer, where the fourth elastic modulus has a value lower than the third elastic modulus.

In one aspect of the present invention, a method for manufacturing an electronic device can be used to manufacture an electronic device by attaching a semiconductor circuit unit including various circuit elements and semiconductor elements such as electrodes and interconnects onto a flexible patch configured to be attached to the skin.

In particular, electronic devices can be manufactured in which circuit elements and semiconductor elements are arranged on a flexible patch. The patch that is attached to the skin surface must be flexible. The present invention can solve problems that arise when directly integrating circuit elements and/or semiconductor elements on a flexible patch through a reverse process that integrates the semiconductor circuit in reverse order.

Such flexible patches for electronic devices can have high breathability and strong adhesion by including multiple through holes. This means that even when the electronic device is attached to the skin, it does not affect the skin condition.

The multiple through holes may also be configured to have different sizes to maximize the functionality of the semiconductor circuit disposed on the flexible patch.

In one embodiment, when the semiconductor element of the electronic device includes a piezoelectric material, the electronic device can be used as a skin sensor that can be attached to the skin to obtain deformation and/or elasticity information of the skin. The piezoelectric material that senses deformation is placed on a relatively large through hole, allowing the skin sensor to more efficiently obtain skin deformation information due to the physiological behavior of the skin.

In another embodiment, if the semiconductor elements of the electronic device are configured to respond to light, the electronic device can be used as an optical sensor or image sensor for the skin surface.

In yet another embodiment, if the semiconductor element of the electronic device is configured to respond to moisture, the electronic device can be used as a moisture sensor to measure moisture loss in the skin.

In order to more clearly describe the technical solutions of the embodiments of the present invention or the prior art, the drawings necessary for the description of the embodiments are briefly introduced below. The same drawing numbers are used to identify similar elements shown in one or more drawings. It should be understood that the drawings below are merely illustrative for the purpose of describing the embodiments of the present specification, and are not illustrative for the purpose of limiting the present invention. In addition, for clarity of description, some elements may be shown in the drawings below with various modifications such as exaggeration and omission.
FIG. 1 is a schematic diagram of an electronic device attached to a subject's skin in accordance with an embodiment of the present invention. FIG. 1 is a schematic diagram of an electronic device attached to a subject's skin in accordance with an embodiment of the present invention. FIG. 1 is a schematic diagram of an electronic device attached to a subject's skin in accordance with an embodiment of the present invention. 1A to 1C are diagrams illustrating the operation principle of a skin sensor according to an embodiment of the present invention. 1A to 1C are diagrams illustrating the operation principle of a skin sensor according to an embodiment of the present invention. 1A to 1C are diagrams illustrating the operation principle of a skin sensor according to an embodiment of the present invention. 1 is a graph showing skin deformation rate over time as measured by a skin sensor according to one embodiment of the present invention. 1A to 1C are conceptual diagrams illustrating a manufacturing process of a skin sensor according to a first embodiment of the present invention. 1A to 1C are conceptual diagrams illustrating a manufacturing process of a skin sensor according to a first embodiment of the present invention. 2 is a cross-sectional view showing a preparation process of a semiconductor structure in which an active layer is formed during the manufacturing process of a skin sensor 1 according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view showing a preparation process of a semiconductor structure in which an active layer is formed during the manufacturing process of a skin sensor 1 according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view showing a preparation process of a semiconductor structure in which an active layer is formed during the manufacturing process of a skin sensor 1 according to a first embodiment of the present invention. FIG. FIG. 1 is a diagram illustrating an electrode and/or interconnect structure configured to have auxetic properties in accordance with one embodiment of the present invention. FIG. 1 is a diagram illustrating an electrode and/or interconnect structure configured to have auxetic properties in accordance with one embodiment of the present invention. FIG. 1 is a diagram illustrating an electrode and/or interconnect structure configured to have auxetic properties in accordance with one embodiment of the present invention. FIG. 1 is a diagram illustrating an electrode and/or interconnect structure configured to have auxetic properties in accordance with one embodiment of the present invention. FIG. 1 is a diagram illustrating an electrode and/or interconnect structure configured to have auxetic properties in accordance with one embodiment of the present invention. 1 is a diagram illustrating a transfer structure according to one embodiment of the present invention. FIG. 2A-2C are schematic diagrams illustrating a manufacturing process for a flexible patch 30 according to one embodiment of the present invention. FIG. 2 is a diagram illustrating a flexible patch formed by a mold according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a flexible patch formed by a mold according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a flexible patch formed by a mold according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a flexible patch formed by a mold according to an embodiment of the present invention. FIG. 2 is a diagram for explaining the application of a flexible patch to be attached to the skin according to one embodiment of the present invention. FIG. 2 is a diagram for explaining the application of a flexible patch to be attached to the skin according to one embodiment of the present invention. FIG. 2 is a diagram for explaining the application of a flexible patch to be attached to the skin according to one embodiment of the present invention. FIG. 2 is a diagram for explaining the application of a flexible patch to be attached to the skin according to one embodiment of the present invention. 10A to 10C are conceptual diagrams illustrating a manufacturing process of a skin sensor according to a second embodiment of the present invention. 10A to 10C are conceptual diagrams illustrating a manufacturing process of a skin sensor according to a second embodiment of the present invention. 13A to 13C are conceptual diagrams illustrating a manufacturing process of a skin sensor according to a third embodiment of the present invention. 13A to 13C are conceptual diagrams illustrating a manufacturing process of a skin sensor according to a third embodiment of the present invention. 13A to 13C are conceptual diagrams illustrating a manufacturing process of a skin sensor according to a third embodiment of the present invention. 13A to 13C are conceptual diagrams illustrating a manufacturing process of a skin sensor according to a third embodiment of the present invention. 13A to 13C are conceptual diagrams illustrating a manufacturing process of a skin sensor according to a third embodiment of the present invention. 13A to 13C are conceptual diagrams illustrating a manufacturing process of a skin sensor according to a third embodiment of the present invention. 13A to 13C are conceptual diagrams illustrating a manufacturing process of a skin sensor according to a third embodiment of the present invention. 13A to 13C are conceptual diagrams illustrating a manufacturing process of a skin sensor according to a third embodiment of the present invention. 13A to 13C are conceptual diagrams illustrating a manufacturing process of a skin sensor according to a fourth embodiment of the present invention. 13A to 13C are conceptual diagrams illustrating a manufacturing process of a skin sensor according to a fourth embodiment of the present invention. 13A to 13C are conceptual diagrams illustrating a manufacturing process of a skin sensor according to a fourth embodiment of the present invention. 13A to 13C are conceptual diagrams illustrating a manufacturing process of a skin sensor according to a fourth embodiment of the present invention. 13A to 13C are conceptual diagrams illustrating a manufacturing process of a skin sensor according to a fourth embodiment of the present invention. 13A to 13C are conceptual diagrams illustrating a manufacturing process of a skin sensor according to a fourth embodiment of the present invention. 13A to 13C are conceptual diagrams illustrating a manufacturing process of a skin sensor according to a fourth embodiment of the present invention. 13A to 13C are conceptual diagrams illustrating a manufacturing process of a skin sensor according to a fourth embodiment of the present invention. 13A to 13C are conceptual diagrams illustrating a manufacturing process of a skin sensor according to a fourth embodiment of the present invention. 13A to 13C are conceptual diagrams illustrating a manufacturing process of a skin sensor according to a fourth embodiment of the present invention. 13A to 13C are conceptual diagrams illustrating a manufacturing process of a skin sensor according to a fourth embodiment of the present invention.

Terms such as first, second, and third are used to describe various parts, components, regions, layers, and/or sections, and the present invention is not limited thereto. These terms are used only to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Thus, a first part, component, region, layer, or section described below may be referred to as a second part, component, region, layer, or section within the scope of the present invention.

The terminology used herein is merely for the purpose of referring to particular embodiments and is not intended to limit the present invention. The singular expressions used herein include the plural expressions unless the context clearly dictates otherwise. The term "comprises" as used in the specification does not mean to embody certain features, regions, integers, steps, operations, elements and/or components and does not mean to exclude the presence or addition of other features, regions, integers, steps, operations, elements and/or components.

Additionally, relative spatial terms such as "below," "above," and the like may be used to more easily describe the relationship of one part depicted in the drawings to another. Such terms are intended to include other meanings and operations of the device in use as well as the intended meaning in the drawings. For example, if the device in the drawings were turned over, a part described as being "below" another part would be described as being "above" the other part. Thus, the exemplary term "below" includes both an orientation of up and down. The device could be rotated 90 degrees or at other angles and the relative spatial terms would be interpreted accordingly.

All terms, including technical and scientific terms, used herein have the same meaning as commonly understood by a person of ordinary skill in the art to which the present invention belongs, unless otherwise defined. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with the relevant technical literature and the currently disclosed contents, and should not be interpreted in an ideal or overly formal sense unless expressly defined in the present specification. In the present specification, the electronic device that can be attached to the skin includes a substrate that can be attached to the skin; and a semiconductor circuit unit integrated on the substrate. The semiconductor circuit unit includes an active layer; a semiconductor element including an insulating layer, and circuit connection components such as electrodes and/or interconnectors, and operates as a circuit that performs the function of the electronic device. The electronic device may be configured to operate by itself or to operate by being electrically connected to an external device. In one embodiment, the electronic device that can be attached to the skin may be a skin sensor that can obtain information on the skin of the target to which the electronic device is attached. However, the description related to the electronic device that can be attached to the skin of the present invention is not limited to a skin sensor. According to an embodiment of the present invention, an electronic device (e.g., a light emitter) that operates in a function other than a sensor and the electronic device can be manufactured.

The following describes in detail an embodiment of the present invention with reference to the drawings.

Figures 1a to 1c are schematic diagrams illustrating an electronic device attached to a subject's skin according to an embodiment of the present invention.

Referring to FIG. 1a, an electronic device 1 according to an embodiment of the present invention is attached to the skin of a subject.

In one embodiment, the electronic device 1 includes a semiconductor circuit unit 10 that operates to perform the function of a sensor, and a flexible patch 30 that can be attached to the skin and serves as a substrate on which the semiconductor circuit unit 10 is integrated.

The semiconductor circuit unit 10 is composed of a semiconductor element including a semiconductor material, and circuit components such as electrodes and/or interconnection components (e.g., interconnects, etc.).

The function of the semiconductor circuit unit 10 depends on the semiconductor element and/or circuit components. In one embodiment, when the active layer of the semiconductor circuit unit 10 is made of a piezoelectric material, the semiconductor circuit unit 10 operates as a piezoelectric element circuit in which the characteristics of the current change according to the change in shape of the active layer, and the electronic device 1 including the semiconductor circuit unit 10 can operate as a skin deformation sensor that obtains deformation information and even elasticity information of the skin. In this way, when the electronic device 1 includes components made of a piezoelectric material, the semiconductor circuit unit 10 operates as a change-sensing structure. This will be described in more detail later with reference to Figures 2 and 3.

Alternatively, if the semiconductor circuit unit 10 includes a material that responds to changes in light, the electronic device 1 can operate as a skin optical sensor or a skin image sensor.

Alternatively, if the semiconductor circuit unit 10 includes a material that responds to changes in moisture, the electronic device 1 can operate as a skin moisture sensor.

Alternatively, if the semiconductor circuit unit 10 contains a material capable of emitting light, the electronic device 1 can operate as a light-emitting skin massager.

For clarity of explanation, the present invention will be described below by taking as an example a semiconductor circuit unit 10 as a sensor circuit unit that can sense deformation of the skin by including a piezoelectric material (hereinafter, the semiconductor circuit unit 10 may also be referred to as a sensor unit circuit 10), and by taking as an example an electronic device 1 as a skin sensor including the sensor unit circuit 10 (hereinafter, the electronic device 1 may also be referred to as a skin sensor 1).

According to an embodiment of the present invention, a skin sensor 1 that can be attached to the skin can be manufactured. The skin sensor 1 may be configured to be attached to the skin to obtain information about the skin.

The skin sensor 1 according to one embodiment includes a flexible patch 30 having a plurality of air permeable through holes H formed therein, and a sensor circuit unit 10 attached to the flexible patch 30.

The flexible patch 30 is a substrate on which the semiconductor circuit unit 10 is integrated, and at least one surface is configured to have a viscosity that allows it to be attached to the skin. The flexible patch 30 also includes multiple through holes, and is configured to have high breathability and strong adhesion. This will be described in more detail later with reference to Figures 2 and 3.

The skin sensor 1 is provided in a free standing manner on the breathable through-hole H. In one embodiment, as shown in FIG. 1a, the active layer of the skin sensor unit 10 is configured as a free standing structure located on the through-hole. Since the active layer, which is a piezoelectric material, is suspended in a free standing manner on the through-hole for skin breathability, the change in the through-hole due to skin deformation can be efficiently measured. That is, the active layer of the skin sensor 1 can be effectively bent by the skin deformation induced by mechanical stress.

The skin sensor 1 includes a sensor circuit unit 10 disposed on a flexible patch 30, the sensor circuit unit 10 including circuit components (e.g., electrodes 111 and/or interconnects 112), an insulating layer 113, and an active layer 115.

In some embodiments, the sensor circuit unit 10 includes circuit components (e.g., electrodes 111 and/or interconnects 112) disposed on the flexible patch 30, an insulating layer 113 disposed on the circuit components, and an active layer 115 disposed on the insulating layer 113, as shown in Figures 1b to 1c. The components 111, 112, 113, and 115 disposed on the flexible patch 30 may be configured to have through holes corresponding to at least one of the through holes of the flexible patch 30. This allows the electronic device 1 to have strong adhesion and ensure high breathability.

In some other embodiments, the sensor circuit unit 10 includes an active layer 115 disposed on the flexible patch 30, an insulating layer 113 disposed on the active layer 115, and circuit components disposed on the insulating layer 113. The operating principle of such a skin sensor 1 will be described in more detail below with reference to FIG. 2.

The skin sensor 1 may include one or more semiconductor circuit units 10. The semiconductor circuit units 10 may be configured to perform the same function or may be configured to perform different individual functions.

Such a skin sensor 1 is configured to minimize the effect on the recipient's skin even when attached for a long period of time, while obtaining various information about the recipient's skin (e.g., skin elasticity information, skin deformation information, etc.) with the semiconductor circuit attached to the skin via a flexible patch.

Figures 2a to 2c are diagrams for explaining the operating principle of the skin sensor 1 according to one embodiment of the present invention.

Referring to Figs. 2a to 2c, a skin sensor 1 according to an embodiment of the present invention may be detachably attached to the skin Ts, Td. The skin includes a stratum corneum Ts and a dermis Td. The skin sensor 1 is in close contact with the surface of the stratum corneum Ts. Mechanical changes in the skin cause changes in the through-holes H. Therefore, if the changes in the through-holes H can be measured, information about the mechanical changes in the skin can be obtained.

Mechanical changes in the skin may be analyzed based on the mechanism of the skin membrane. The skin is composed of a stratum corneum up to about 20 μm, and an epidermis layer and a dermis layer up to about 2 mm. As a result, when the dermis layer is used as a substrate, the stratum corneum has a thin film structure at a ratio of about 1/100 of the dermis layer. Therefore, when the skin dries, a volume contraction of the stratum corneum, which is in a relatively thin film form, is induced.

When dryness occurs, initially the moisture content of the stratum corneum decreases and it shrinks, but the dermis is relatively resistant to drying, so the dermis pulls on the stratum corneum, generating tensile stress. However, as dryness continues, the elastic modulus of the stratum corneum increases and cracks occur in the stratum corneum Ts, causing a loss of its protective function. When cracks occur, the tensile stress decreases and the layer begins to sag.

The skin sensor 1 may be attached in a self-supporting manner over the through-hole H and configured to sense changes in the skin by sensing changes in pressure applied to the change-sensing structure in response to changes in the size of the through-hole H in contact with the skin.

In this specification, the skin change rate can be defined as the following Equation 1, where the initial length of the skin in a predetermined area is L0 and the length after t hours is Lt.
[Mathematical Formula 1]
Rate of change (%) = change in length (Lt-L0)/initial length L0 x 100
That is, by calculating the change in length of the change-sensing structure (i.e., the active layer 115), the skin change rate can be provided as a quantitative value.

Situation (a) in FIG. 2a shows the case where there is no skin change and no pressure is applied. In situation (a) in FIG. 2, the through hole may have a length of d3.

Situation (b) in FIG. 2b shows a case where a substance containing moisture is released from the skin over time. In situation (b) in FIG. 2b, when a substance containing moisture is released from the skin over time and the stratum corneum dries first, tensile stresses F5 and F6 are generated in the stratum corneum. This increases the size of the through-holes, and tensile stress is applied to the portion of the active layer 115 located on the through-holes. The through-holes may have a length of d4. d4 is longer than d3. The portion of the active layer 115 located on the through-holes changes in response to the change in the through-holes, causing a change in current. In this case, it can be determined that the subject has experienced skin tightness.

Situation (c) in FIG. 2c shows the case where dryness continues to occur. When dryness continues to occur, cracks C occur in the stratum corneum, and the size of the through-holes decreases compared to situation (b). This reduces the tensile stress applied to the portion of the active layer 115 located on the through-holes, which may have a length of d5 in this case. d5 is shorter than d4.

In this manner, the amount of skin change can be measured by the pressure applied to the active layer 115 portion placed on the through-hole.

Figure 3 is a graph showing the skin deformation rate over time measured by a skin sensor according to one embodiment of the present invention.

The situation (a) in Figure 2a corresponds to the start of exposure in the graph of Figure 3. When the skin starts to dry, the tensile stress increases due to the drying of the stratum corneum, resulting in a sustained increase in skin deformation, as shown in situation (b) in Figure 2b.

Then, in situation (c) of Figure 2c where the stratum corneum is formed, the tensile stress decreases again as cracks form in the stratum corneum, causing the deformation to return to the same or equivalent state as the initial state.

In the skin sensor 1 attached to the skin surface, the sensor circuit unit 10 that functions as a sensor is located on the flexible patch 30. In other words, the flexible patch 30 is used as a substrate on which circuits are integrated. Unlike commonly used circuit boards, the flexible patch 30 is soft and sticky. Therefore, there is a problem in that it is difficult to manufacture the skin sensor 1 according to the present invention by simply sequentially integrating circuit components on a substrate.

First Example
4a and 4b are schematic conceptual diagrams illustrating a manufacturing process of a skin sensor according to a first embodiment of the present invention.

Referring to FIG. 4a and FIG. 4b, the method for manufacturing the skin sensor 1 according to the first embodiment of the present invention includes the steps of forming a sacrificial layer 105 on a substrate 101 (S401); forming a sensor circuit unit 10 on the sacrificial layer 105 (S410), which includes forming an electrode 111 and/or an interconnect 112 on the sacrificial layer 105 (S411); forming an insulating layer 113 on the electrode and/or interconnect (S413); and forming an active layer 115 on the insulating layer 113 (S415); bonding the sensor circuit unit 10 (i.e., the active layer 115) and the flexible patch 30 (S430); and etching the sacrificial layer 105 to manufacture the skin sensor 1 (S450).

The substrate 101 (or referred to as the first substrate) is used to stack the internal layers of the sensor circuit unit 10. That is, the substrate 101 is a substrate used to form components of the sensor circuit unit 10, such as the electrodes 111 and/or the interconnects 112, the active layer 115, etc. In one example, the substrate 101 is made of silicon (Si), and a sacrificial layer 105 may be formed on the substrate 101 (S401).

Meanwhile, the sacrificial layer 105 is made of a material (e.g., a metal) that is resistant to organic solvents and can be photolithographed. In one embodiment, the sacrificial layer 105 may be made of a material including one or more of Cr, Al, Ni, Au, and combinations thereof.

In addition, the sacrificial layer 105 may be further configured based on one material property related to adhesion (e.g., standard oxidation potential) and/or another material property related to thermal stability (e.g., melting temperature). In this case, the sacrificial layer 105 may have strong adhesion and thermal stability sufficient to withstand various strains. In some embodiments, the sacrificial layer 105 may be made of a material including one or more of Cr, Al, Ni, and combinations thereof.

A semiconductor structure that operates as a sensor circuit unit 10 is provided on the sacrificial layer 105.

Figures 5a to 5c are cross-sectional views showing the preparation process of a semiconductor structure in which an active layer is formed during the manufacturing process of a skin sensor 1 according to the first embodiment of the present invention.

Referring to FIG. 5a, a conductive layer including electrodes 111 and/or interconnects 112 is formed on the sacrificial layer 105 (S411). The electrodes 111 and/or interconnects 112 are circuit components made of a conductive material (e.g., gold (Au), platinum (Pt)), and transmit a current change based on the active layer functioning as a piezoelectric element to operate as the skin sensor 1.

The skin sensor 1 is configured to be deformable in response to the skin surface, and is also configured to have a high durability that can withstand excessive deformation of the skin sensor 1 during the process of putting on and taking off. As a result, the electrodes 111 and/or the interconnects 112 are formed with a structure that is resistant to deformation.

Figures 6a to 6e are diagrams illustrating an electrode and/or interconnect structure configured to have auxetic properties according to one embodiment of the present invention.

In one embodiment, the electrodes 111 and/or interconnects 112 are formed on the sacrificial layer 105 in a planar structure that can realize auxetic properties (S411).

An auxetic structure generally refers to a structure whose dimensions increase in a direction perpendicular to a first direction when it is subjected to a tensile force in the first direction. For example, if an auxetic structure has a length, width, and thickness, when the auxetic structure is subjected to a tensile force in the longitudinal direction, its width increases. Also, an auxetic structure is bidirectional in that its length and width increase when it stretches in the longitudinal direction, and its width and length increase when it stretches in the lateral direction, but its thickness does not increase. Such an auxetic structure is characterized by having a negative Poisson's ratio.

In step (S411), a first electrode 111A and a second electrode 111B are formed on the sacrificial layer 105. Referring to FIG. 6a, the first electrode 111A and the second electrode 111B include one or more bars. The bar included in the first electrode 111A has a zigzag shape in plan and extends to the opposite second electrode 111B. The bar included in the second electrode 111B also has a zigzag shape in plan and extends to the opposite first electrode 111A. By including the zigzag shape bars, each of the electrodes 111A and 111B can have properties that arise from an auxetic structure (i.e., auxetic structure properties).

Referring to FIG. 6b, in one embodiment, the bar may be configured with a circular cut hinge pattern at the point where the bar changes direction. The cut hinge pattern may prevent crack propagation.

As shown in FIG. 6c, the interconnect 112 is configured to form a dumbbell-shaped hole with circular ends and a center portion connecting the circular ends, which is made of a pillar having a thickness smaller than the diameter of the ends. The interconnect 112 is also configured to form a circular hole (dumbbell-hole pattern). The interconnect 112 having such a through hole formed therein can have properties arising from the auxetic structure (i.e., auxetic structure properties).

Due to these auxetic structural characteristics, even if an external force acts on the interconnect 112 and the shape of the interconnect 112 is deformed, the occurrence of cracks at both ends is minimized. Referring to FIG. 6d, it can be seen that the locations where cracks occur are fewer when there are dumbbell-shaped through holes.

The electrodes 111 and/or interconnects 112 having such auxetic structure characteristics may be formed on the sacrificial layer 105 in a variety of ways. In one example, the electrodes 111 and/or interconnects 112 may be formed by a photolithography-based etching process using a mask (e.g., as shown in FIG. 6e) configured to form the auxetic structure after forming the conductive layer. The conductive layer areas corresponding to the dark areas in the mask of FIG. 6e become the interconnects, and the conductive layer areas corresponding to the light areas become the through holes.

5b, after forming the electrodes 111 and/or the interconnects 112, an insulating layer 113 is formed (S413). The insulating layer 113 may be an oxide layer ( _SiO2 ) formed on the surface of the silicon (Si) substrate 110. However, this is merely an example, and the insulating layer 113 may be made of an oxide material other than silicon oxide.

In one embodiment, the insulating layer 113 may include a plurality of through holes to ensure breathability. The through holes of the insulating layer 113 are formed to match the through holes of the flexible patch 30 so as not to impede the flow of air moving through the through holes of the flexible patch 30. This maximizes the breathability of the skin sensor 1. In some embodiments, the through holes of the insulating layer 113 may be formed by a photolithography-based etching process.

Referring to FIG. 5c, active layer 115 may be formed on insulating layer 113 (S415). The active layer 115 and the process of forming active layer 115 are described in more detail with reference to FIG. 7 below.

Figure 7 is a diagram illustrating a transfer structure according to one embodiment of the present invention. In one embodiment, the active layer 115 may be formed on the insulating layer 113 by being transferred using the transfer structure (S415).

Referring to FIG. 7, the transfer structure is a structure formed on a substrate 701, and includes a metal layer 710 formed on the substrate 701; an active layer 115 formed on the metal layer 710; a stressor layer 730 formed on the active layer 115; and a tape layer 750 disposed on the stressor layer 730.

The substrate 701 (also referred to as the second substrate) is a substrate used to form the transfer structure and is different from the substrate 101. The active layer 115 is formed on the substrate 701. In one example, the substrate 701 may be made of a material including silicon (Si).

In one embodiment, the active layer 115 may be formed on a metal layer 710 formed on the substrate 701. The metal layer 710 is configured to have a weak adhesive strength so that the active layer 115 can be more easily transferred. In one example, the metal layer 710 may be made of a material including gold (Au).

The active layer 115 is a layer made of a material having semiconductor properties, and performs the main function of the electronic device 1 that can be attached to the skin. When the electronic device 1 that can be attached to the skin is used as a skin sensor, in one embodiment, the active layer 115 may be made of a material containing Ga or Al that has excellent electron transport properties and can be used as a piezoelectric material. For example, the active layer 115 may be made of a material containing AlN or GaN.

The stressor layer 730 applies deformation to the material of the active layer 115 to enhance the semiconductor properties. For example, the stressor layer 730 may enhance the piezoelectric performance. The stressor layer 730 is also configured to minimize the formation of cracks during the process of transferring the active layer 115 onto the insulating layer 113. To this end, the stressor layer 730 may be formed in a multi-layer structure including multiple layers having various materials and thicknesses.

In one embodiment, the stressor layer 730 includes three layers (731-735). The first stressor layer 731 may be a high stress metal layer made of a Ni-containing material (e.g., Ni or AgNi). The second stressor layer 733 may be made of an Al-containing material. The third stressor layer 735 may be made of an Ag-containing material.

The first stressor layer 731 may be formed to have different thicknesses depending on the material. For example, if the first stressor layer 731 is made of Ni, the thickness of the first stressor layer 731 may be 50 nm. On the other hand, if the first stressor layer 731 is made of AgNi, the thickness of the first stressor layer 731 may be 70 nm.

The formation method for each stressor layer may be the same or different. In one example, the first stressor layer 731 formed on the active layer 115 may be formed by evaporation. The second stressor layer 733 formed on the first stressor layer 731 and the third stressor layer 735 formed on the second stressor layer 731 may be formed by sputtering deposition. The formation rates of each stressor layer may be different. In one example, the second stressor layer 733 may be formed at 1.8 Å ^-1 and the third stressor layer 735 may be formed at 2 Å s ^-1 . In another example, the second stressor layer 733 may be formed at 0.4 Å s ^-1 and the third stressor layer 735 may be formed at 2 Å ^{s -1} .

7 is peeled off from the substrate 701 by the tape layer 750, and the peeled active layer 115 is transferred onto the insulating layer 113. The tape layer 750 and the stressor layer 730 are then removed to form a laminate including the substrate 101, the sacrificial layer 105, the conductive layer including the electrodes 111 and/or interconnects 112; the insulating layer 113, and the active layer 115.

In one embodiment, the transfer of the active layer 115 using the transfer structure of FIG. 5 may be performed at a temperature in the range of about 165° C. In this case, the amount of tape residue on the active layer 115 is minimized.

Thus, an active layer 115 made of high performance, single crystal piezoelectric semiconductor material (AlN, GaN) may be transferred onto the insulating layer 113 using 2-dimensional material based layer transfer (2DLT).

Referring also to FIG. 4, the flexible patch 30, which is a component that is attached to the skin, is placed on the active layer 115 of the semiconductor structure, and the placed flexible patch 30 is attached to the active layer 115 (S430).

Figure 8 is a schematic diagram showing the manufacturing process of a flexible patch 30 according to one embodiment of the present invention.

Referring to FIG. 8, the method for manufacturing the flexible patch 30 includes the steps of forming a sacrificial layer on a mold having a plurality of grooves formed on one surface (S810); and forming a flexible patch layer on the sacrificial layer (S830).

For rigid materials, wet/dry etching is used to form a geometric planar structure such as a surface patterned with micro-holes as shown in FIG. 1a and FIG. 1b. However, when a relatively soft flexible material (e.g., PDMS, etc.) is used to form a geometric planar structure using a dry/wet etching method, there is a problem that the shape of the geometric planar structure such as holes is destroyed. Therefore, when a mold 810 having a number of grooves is used to form a number of holes on one surface of the flexible material, a flexible patch layer 830 can be obtained in which the shape of the holes is not destroyed.

The mold 810 is configured to have a groove formed on one surface and to have a geometric plane. The cross section of the groove forming the geometric plane of the mold 810 is formed in a concave shape toward the inside of one surface as shown in FIG. 8. When any material having flowability (including, for example, a flexible material used to form the flexible patch layer 830) is formed on the mold 810, the any material fills the groove. When the any material hardens, a structure of a height corresponding to the filled groove is formed inside the groove. The groove may be configured to have a single step or one or more steps.

The flexible patch layer 830 includes an adhesive material layer so that it can be attached to the skin. Therefore, if the flexible patch layer 830 is formed directly on the mold 810, it is difficult to separate the flexible patch layer 830 from the mold 810, and if the flexible patch layer 830 is damaged during this process, the quality of the flexible patch 30 may be reduced. To overcome this, before filling the grooves of the mold 810 with a flexible material, a sacrificial layer 820 having an anti-sticky layer function that prevents the flexible patch layer 830 from sticking to the mold 810 is formed between the mold 810 and the flexible patch layer 830 (S810). By using the sacrificial layer 820, the flexible patch layer 830 can be separated from the mold 810 without damage, and a high-quality flexible patch 30 can be obtained.

The mold 810 is configured to be resistant to etching by an etching solution, to be able to retain its shape even when a certain amount of heat is applied, and to have a certain amount of hardness. The mold 810 is also made of a non-magnetic material. In one example, it may be made of a material containing silicon (Si), but is not limited thereto, and may be made of various materials that are not removed by the material used to remove the sacrificial layer 820 described below, can retain their shape even at or above a certain temperature, and are not difficult to manufacture.

Figures 9a to 9d are diagrams illustrating the structure of a mold and multiple through holes in a flexible patch formed by the mold according to an embodiment of the present invention.

The mold 810 has a groove shape and distribution that creates holes that give the flexible patch 30 excellent properties such as breathability and application.

In one embodiment, the grooves formed in the surface of the mold 810 may be configured to form a pattern of multiple circular through holes. For example, a mold 810 having grooves with a circular frame may be used to form multiple holes in the flexible patch 30. Using the mold 810 of FIG. 9a, a flexible patch 30 including through holes having a planar surface as shown in FIG. 9b can be obtained.

In some embodiments, the grooves formed in the mold 810 may be distributed such that the spacing between the holes in the flexible patch 30 is less than 60 μm. For example, the width of the groove may be less than 60 μm. The sweat pores have various sizes depending on the location on the skin where they are located. For example, it is known that the area of the sweat pores has a diameter of 60 μm or more, with an average diameter of 80 μm. In addition, since the amount of waste that needs to be discharged and the biological functions performed by sweat, such as temperature regulation, differ depending on the location on the skin, the sweat pores are arranged at different distribution densities depending on the body part. For example, the sweat pores are distributed at a density of 60 cm ⁻² on the back, 400 cm ⁻² on the palm, and 180 cm ⁻² on the forehead.

Based on such sweat pore size and area information, the spacing between the holes in the flexible patch 30 needs to be less than 60 μm. If the spacing between the holes is 60 μm or more, the surface of the flexible patch 30 other than the holes may block the sweat pores. For this reason, a flexible patch 30 with a spacing between holes of less than 60 μm can achieve higher breathability (e.g., nearly 100% breathability). In some embodiments, the flexible patch 30 may be manufactured using a mold 10 that has a through-hole pattern with a spacing between holes of 50 μm.

The main factor for achieving high breathability is the spacing between the through holes. The size of the through holes affects both the adhesiveness and the breathability. The larger the through holes, the greater the skin area that comes into contact with air, but conversely, the less skin volume is captured. In an embodiment of the present invention, even if the through holes are small, high breathability and strong adhesiveness can be obtained by reducing the spacing between the through holes. The size of the through holes may be set in a variety of ways as long as it does not impede adhesiveness.

The grooves on the surface of the mold 810 are formed in consideration of the design of the semiconductor circuit integrated on the flexible patch 30. In some embodiments, the grooves formed on the surface of the mold 810 form a pattern of multiple circular holes, which may include a combination of one circular hole having a relatively large diameter and multiple circular holes having smaller diameters surrounding the one circular hole.

For example, when a portion of a piezoelectric element is placed on a through-hole on the flexible patch 30 and circuit components are arranged to measure and transmit a change in current due to deformation of the piezoelectric element, the portion of the piezoelectric element where the main deformation occurs may be configured to form a relatively large through-hole, and the remaining portion may be configured to form relatively small through-holes. In this case, only the small number of through-holes in which the piezoelectric elements are placed are made large in size, and the remaining through-holes, which make up the majority of the flexible patch 30, are small enough to capture the skin, so that the flexible patch still has strong adhesion.

The flexible patch 30 may also be formed to have properties that arise from the auxetic structure (i.e., auxetic structure properties). For example, the grooves of the mold 810 may be configured to form circular through-holes in the flexible patch 30, and may also be configured to form through-holes that have a dumbbell-shaped planar shape.

Specifically, when a dumbbell-shaped hole and a circular hole are formed in the flexible patch 30, in which both ends are circular and the center connecting the two circles is made of a pillar with a thickness smaller than the diameter of both ends (i.e., when a through hole in a dumbbell-hole pattern is formed), the flexible patch 30 having such a through hole may have auxetic structural characteristics. That is, the mold 810 is composed of a structure in which pillars are formed surrounding circular and/or dumbbell-shaped empty spaces. By using the mold 810 of FIG. 9c, a flexible patch 30 including a through hole having a plane of FIG. 9d can be obtained.

In one embodiment, the interval between holes may be less than 60 μm to obtain high breathability, as described above. In one example, as shown in FIG. 9c, the interval between the center of the connection part of one dumbbell through hole H _C and one end of another dumbbell through hole H _C may be 35 μm, and the interval between one end of one dumbbell through hole H _C and another circular through hole H _B may be 25 μm. In addition, the diameter of the circular through hole H _B may be 50 μm, and the internal interval of one end of the dumbbell through hole H _C may be 100 μm. However, this is merely an example, and may be variously set based on the breathability, attachment, durability, etc. of the flexible patch 30.

The sacrificial layer 820 may be formed on the mold 810 of FIG. 9a by a spin coating method.

However, when the spin-coating method is applied to form the sacrificial layer 820 on the mold 810 of FIG. 9c, the PDMS patch layer 830 cannot be separated from the mold 810 of FIG. 9c, and the flexible patch 30 having holes formed at intervals of tens of microns (e.g., 60 μm intervals) cannot be manufactured. This is because the mold 810 of FIG. 9c is configured to form circular and dumbbell-shaped through-holes, so that the contact area between the mold 810 and the PDMS patch layer 830 is increased compared to the embodiment using the mold 810 of FIG. 9a, and the intervals of the grooves in the mold 810 of FIG. 9c are narrowed, which causes uneven PMMA spin-coating.

When forming a sacrificial layer 820 on the mold 810 as shown in FIG. 9c, the sacrificial layer 820 is formed on the mold 810 of FIG. 9c using an evaporation coating method (S130). In one example, the evaporation coating method may be SAMs (self-assembled monolayers).

Through this process, a sacrificial layer 820 and a flexible patch layer 830 can be formed on a mold 810 having a geometric plane associated with auxetic structural characteristics (S810, S830). Then, after removing the portion of the flexible patch layer 830 that exceeds the groove (S850), the sacrificial layer 820 can be etched to obtain a flexible patch 30 having a geometric plane with auxetic structural characteristics.

The flexible patch 30 of FIG. 9d, manufactured using the mold 810 of FIG. 9c, induces a moisture change of about 6% when comparing the amount of change in skin moisture before and after application. In other words, there is almost no moisture loss in the skin even when the flexible patch 30 is applied.

Referring again to FIG. 8, the sacrificial layer 820 is made of a material that can be used to manufacture nano- to micro-scale semiconductor devices. In one embodiment, the sacrificial layer 820 is made of a material that includes PMMA (Poly(methyl methacrylate)). However, without being limited thereto, the sacrificial layer 820 may be made of a material that includes a polymer, etc.

In one embodiment, the sacrificial layer 820 is formed on one surface of the mold 810 having a groove by a spin coating method (S810). The sacrificial layer 820 is formed to a thickness that can prevent the mold 810 and the flexible patch layer 830 from being attached to each other and can be easily removed by the etching solution in step (S870).

The flexible patch layer 830 is made of a material that has flexibility to allow conformable contact so that the patch can be deformed according to the contours of the skin, and has adhesive properties that allow it to be attached to the skin. In one embodiment, the flexible patch layer 830 may be made of an elastic polymer that has mechanical properties similar to those of the skin. In one example, the flexible patch layer 830 may be made of a material that includes PDMS (Poly-dimethylsiloxane).

In some embodiments, the flexible patch layer 830 may be formed to have a certain thickness. If the flexible patch layer 830 is too thin, it may not be durable enough to be repeatedly applied to the skin. In one example, the flexible patch layer 830 may be formed to have a thickness of 75 μm or more.

In step S830, in which the flexible patch layer 830 is formed on the sacrificial layer 820, the flexible material (e.g., PDMS) that constitutes the flexible patch layer 830 fills the inside of the groove. The flexible material fills the groove and may even overflow from the inside of the groove. In this way, if more flexible material is supplied than the volume of the inside of the groove and the flexible material overflows outside the groove, a part of the flexible patch layer 830 may be formed at a position higher than the surface of the mold 810.

The structure including the mold 810, the sacrificial layer 820, and the flexible patch layer 830 obtained by filling or overflowing the flexible material into the grooves is similar to a structure in a state where a casting is poured into the mold before the casting is completed, for example. Hereinafter, the casting-mold structure, which is frequently used in this specification to help ordinary engineers understand, refers to a structure including the mold 810, the sacrificial layer 820, and the flexible material, in which the flexible material is filled into the grooves (or filled to overflow from the grooves) as shown in step (S830) of FIG. 8, and the hardness of the flexible material may be soft or hard.

After the flexible patch layer 830 is formed, the flexible patch layer 830 that exceeds the groove (i.e., is formed at a position higher than the surface of the mold 810) is removed (S850). In one embodiment, a plate 850 is placed against the portion of the flexible patch layer 830 that exceeds the groove of the mold 810 (i.e., the excess surface), and the plate 850 and/or the flexible patch layer 830 (i.e., the casting-mold structure) are rubbed to remove the portion that exceeds the groove.

The plate 850 acts as a plastering board to rub and remove excess flexible material. In one embodiment, the plate 850 includes a substrate 851 and a sacrificial layer 852 formed on the substrate 851. The substrate 851 may have a structure (e.g., a flat structure) suitable for performing the rubbing function, and may have durability and strength. The substrate 851 may also be made of a non-magnetic material. In one example, the substrate 851 may be made of a material containing silicon (Si).

The sacrificial layer 852 may be made of a material that can be etched by the etching solution in step (S870). In one example, the sacrificial layer 852 may include the same material as the sacrificial layer 820 (e.g., PMMA). However, without being limited thereto, the sacrificial layer 852 may be made of a material that can be etched by the etching solution in step (S870) and minimizes damage that may occur to the surface of the flexible patch layer 830 after removal in the process of rubbing against the portion of the flexible patch layer 830 that exceeds the groove.

In one embodiment, the sacrificial layer 852 may be formed on the substrate 851 by a spin coating method, but is not limited thereto and may be formed on the substrate 851 by various coating methods.

The rubbing process in step (S850) may further include additional steps to more efficiently remove the excess portion.

In one embodiment, step (S850) may include heating the contact portion between the flexible patch layer 830 and the plate 850. For example, heat of 70° C. or more may be applied to the contact portion between the flexible patch layer 830 and the plate 850 to more efficiently remove the flexible material that exceeds the mold groove.

When heat is applied to the flexible patch layer 830 or the contact portion, the strength of the contact portion is weakened (i.e., it has a soft structural state). As a result, when the plate 850 is rubbed against the flexible patch layer 830 (i.e., the casting-mold structure) (or the casting-mold structure is rubbed against the plate 850), the relative movement causes the excess flexible material to be pushed out of the area occupied by the casting-mold structure. For example, this is similar to the case where a support plate is placed on gypsum plaster and then rubbed, and the gypsum plaster under the support plate is pushed out of the area occupied by the support plate. Eventually, the excess portion gradually becomes lower in height, and the top layer of the flexible material filled in the groove becomes flush with the surface in which the groove is formed, as shown in FIG. 8.

In one embodiment, step (S850) may include a step of flipping the flexible patch layer 830 upside down so that the flexible patch layer 830 is disposed on one surface of the plate 850 during the contact process. When the flipping step is performed, the flexible patch layer 830 (i.e., the casting-mold structure) is disposed on one surface of the plate 850. In the above embodiment, the area of the plate 850 may be larger than the area of the casting-mold structure.

When the plate 850 and the casting-mold structure are rubbed together in this position, the movement of the casting-mold structure pushes the excess flexible material out of the area occupied by the casting-mold structure, further reducing the likelihood of excess flexible material remaining on the sides of the casting-mold structure.

In addition, step (S850) may further include a step of applying pressure to the contact portion between the flexible patch layer 830 and the plate 850. The pressure may be applied using a magnet as shown in FIG. 8. In one example, the casting-mold structure and the plate 850 may be placed in contact between magnets 861 and 862. This allows pressure to be applied to the contact portion due to the attractive force between magnets 861 and 862. As described above, the casting-mold structure and the plate 850 may be made of a non-magnetic material, and therefore do not affect the occurrence of the attractive force interaction between magnets 861 and 862.

This reduces the time required to remove the excess portion as a result of rubbing the casting-mold structure against the plate 850, improving the efficiency of the removal process.

After step (S850), the sacrificial layer 820 is etched using an etching solution (S870). The etching is performed while adjusting the selectivity of the etching solution so as not to etch the mold 810 and the flexible patch layer 830 while etching the sacrificial layer 820. In one embodiment, the etching solution used to etch the sacrificial layer 820 may include acetone.

In an experimental example, the casting-mold structure from which the portion of the flexible patch layer 830 that exceeds the grooves has been removed is immersed in an etching solution to remove the sacrificial layer 820 and separate the mold 810 from the casting (i.e., the flexible patch layer 830). The separated flexible patch layer 830 includes a plurality of holes formed by the grooves of the mold 810. The plurality of holes are formed in a through-shape by conforming the flexible material inside the grooves to the surface of the mold 810 in step (S850). As a result, as shown in FIG. 8, a flexible patch layer 830 including a plurality of through-holes can be obtained, and the flexible patch layer 830 including a plurality of through-holes can be used as a flexible patch 30.

The time for which the cast-mold structure is immersed in the etching solution may be set in various ways. For example, the etching time for the cast-mold structure may be determined according to the thickness of the groove (i.e., the thickness of the flexible patch 30), the thickness of the sacrificial layer 820, the cross-sectional area where the groove and the flexible patch layer 830 abut, etc.

In addition, in step (S870), the casting-mold structure in the etching solution may be subjected to ultrasonic treatment for a more efficient etching process.

The flexible patch 30 manufactured by steps (S810 to S870) can have increased adhesiveness due to the multiple holes, even though it is manufactured to a thickness of microns. In addition, the multiple holes are through-holes, so that even when the flexible patch 30 is attached to the skin, the skin at the attachment portion is not isolated from the outside air. Therefore, the flexible patch 30 is surface-treated to have a microstructure (such as an octopus's sucker or a lizard's foot) only on the surface of the patch, improving only the adhesiveness, and can have both breathability and adhesiveness, unlike conventional skin patches that have relatively poor breathability.

In addition, when the flexible patch layer 830 is separated from the mold 810 using the sacrificial layer 820, multiple holes (or hole patterns) are created in the flexible patch layer 830, and no damage such as tearing occurs during the process of separating it.

The flexible patch 30 has excellent skin adhesion and breathability, so it can be used to manufacture a variety of electronic devices that can be attached to the skin, such as skin sensors.

Furthermore, the flexible patch 30 can have stronger adhesion depending on the material properties such as the components, thickness, etc. of the flexible patch layer 830.

Figures 10a to 10d are diagrams illustrating the adhesion of a flexible patch 30 that is attached to the skin according to one embodiment of the present invention.

The through holes in the flexible patch 30 are in the micron range and are very small compared to the size of the flexible patch 30, and are omitted in FIG. 10 for clarity of explanation.

Figure 10a is a diagram to explain the principle of attaching an object to a surface.

The ability of a contact object P in contact with a surface S to be attached to the surface S is determined by the competition between structural resistance to deformation and interface interaction, which compete with each other in the aspects of reversibility and pluripotency. As shown in Fig. 10a, when a surface is deformed by an object P, the energy between the object P and the surface S can be expressed by the following mathematical equations 2-5.
[Mathematical Formula 2]
U _Total = U _Adhesion + U _Bending
[Mathematical Formula 3]
U _Adhesion = -WbR(2θ)
[Mathematical Formula 4]
U _bending = + bDθ/12R
[Mathematical Formula 5]
D = ^Et3
Here, U _Total denotes the total potential energy, U _Adhesion denotes the adhesion energy between object P and surface S, and U _Bending denotes the bending energy associated with the resistance of surface S to deformation by object P. Here, the signs of the adhesion energy and bending energy simply indicate the direction of interaction, and in other embodiments, the sign of the adhesion energy may be indicated as + and the sign of the bending energy may be indicated as -.

W is the work of adhesion (unit: Nm-1), b is the length of the object P to be attached to the surface, R is the curvature, and θ is the contact angle, which is the angle from the center of the contact between the object P and the surface S to the point where the contact ends. D is the flexural rigidity of the object P, which is determined by the Young's modulus of the object P and the thickness of the object.

To more simply explain the application of the flexible patch 30, a case in which a mono-layer flexible patch 30 is applied to the skin surface will be described with reference to Figure 10a.

10a, when the flexible patch 30 is attached to the skin surface, the surface S corresponds to the skin surface, and the object P corresponds to the flexible patch 30 including the flexible patch layer 830 having a through hole formed therein. Therefore, the bending strength D of the flexible patch 30 is determined by the elastic modulus E of the flexible patch layer 830 and the thickness t of the flexible patch layer 830.

Only when the adhesion energy is equal to or greater than the bending energy, can the patch 30 adhere to the skin surface. If the adhesion energy is less than the bending energy, the patch 30 will detach from the skin surface. The critical work of adhesion ( _Wc ) that determines whether or not the patch can adhere is determined by the following Equation 6.

[Mathematical Formula 6]

When mathematical formula 6 is summarized by _Wc , the threshold work of attachment _Wc for maintaining the attachment between the object and the surface is calculated by _Wc = D/( ^24R2 ). When the work of attachment W between the flexible patch 30 and the skin surface is equal to or greater than the threshold work of attachment _Wc , conformal contact of the flexible patch 30 with the skin surface is possible. On the other hand, when the work of attachment W between the flexible patch 30 and the skin surface is less than the threshold work of attachment _Wc , the flexible patch 30 cannot be attached to the skin surface. Therefore, in order to enable the attachment of the flexible patch 30 to the skin surface, the magnitude of the threshold work of attachment _Wc needs to be small and/or the magnitude of the work of attachment W between the flexible patch 30 and the skin surface needs to be large.

Referring to Equation 5, when the patch 30 is made of a material with a large elastic modulus (e.g., a hard material) and/or is thick, it has a high bending strength D. Therefore, when the bending strength D of the flexible patch 30 decreases and/or when the work of attaching the flexible patch 30 to the skin surface is large, the flexible patch 30 can be stably attached to the skin surface.

Therefore, when the elastic modulus E of the flexible patch 30 is low, the flexible patch 30 can be stably attached to the skin surface when the thickness of the flexible patch 30 is thin.

In addition, the greater the adhesion energy between the flexible patch 30 and the skin surface, the stronger the adhesion of the flexible patch 30. Referring to mathematical formula 2, the adhesion energy between the skin surface and the flexible patch 30 depends on the adhesion work W. The adhesion work W between the flexible patch 30 and the skin surface is expressed by the following mathematical formula 7.

[Mathematical Formula 7]

Here, _γd represents the dispersive component of the contact surface, and _γp represents the polar component of the contact surface. _γdSkin represents the dispersive component of the contact surface of the skin, _γdPatch represents the dispersive component of the contact surface of the patch 30, _γpSkin represents the polar component of the contact surface of the skin, and _γpPatch represents the polar component of the contact surface of the patch 30. The flexible patch 30 is constructed based on Equation 7.

As described above, the flexible patch 30 can be utilized for the manufacture of a skin sensor. The PDMS patch 30 can be attached to the skin, having an exemplary elastic modulus of 1 MPa, sufficient to support micro-scale microelements in the micro thickness range. Although _γd and _γp on the skin surface vary from site to site, the maximum and minimum ranges of the above variables are known as shown in Table 1 below.

By applying the data in Table 1 to Equation 7, the adhesion work W between the skin and the PDMS patch 30 can be roughly calculated as follows: 31≦W≦54 mJm ⁻² . In order for the PDMS patch 30 having an elastic modulus of 1 MPa to be able to adhere to any skin, it must be able to adhere to the skin surface (Skin Min) with the lowest adhesion work. Therefore, the PDMS patch 30 must have a value of W _c =31. Therefore, the PDMS patch 30 must be formed with a thickness of about 80 μm to satisfy the condition of the threshold adhesion work W _c . Therefore, when a single flexible patch 30 with 1 MPa is manufactured with a thickness of less than 80 μm, conformal adhesion to the skin surface is possible.

In some embodiments, a single flexible patch 30 having an elastic modulus lower than 1 MPa can have a thickness of less than 80 μm, providing stronger adhesion. In other embodiments, a single layer of a flexible patch 30 having an elastic modulus lower than 1 MPa can be conformably attached to the skin surface even if it is 80 μm or thicker. For example, the single layer attached to the skin surface can be attached to the skin even if it is 100 μm thick.

As described above, the bending strength D is related to the application ability of the flexible patch 30 and also to the shape retention ability of the flexible patch 30. Referring to the above mathematical formulas 5 and 6, when the elastic modulus E of the flexible patch 30 is low, the flexible patch 30 can be stably applied to the skin surface when the thickness of the flexible patch 30 is thin.

However, if the flexible patch 30 is formed by making the thickness of the flexible patch 30 too thin or by making the elastic modulus too low, with only consideration given to application, it becomes difficult to handle. Specifically, if the bending strength of the flexible patch 30 is too low, bending occurs in the flexible patch 30, making it difficult to handle, and it becomes difficult to maintain a constant shape of the flexible patch 30. Therefore, if the bending strength of the flexible patch 30 is too low, it is difficult to integrate other components on the flexible patch 30.

To overcome this, the flexible patch 30 may be configured so that the portion that is attached to the skin has a relatively low bending strength, and the portion where other components that are not attached to the skin and do not require high adhesion are integrated has sufficient bending strength to maintain its shape without bending. For example, the flexible patch 30 may be composed of one or more layers so that it has stronger adhesion and sufficient bending strength to support other components (including, for example, electrodes, semiconductor elements, interactions, etc.). To manufacture such a flexible patch 30, the flexible patch layer 830 formed on the sacrificial layer 820 may include one or more sublayers.

Figure 10b is a diagram illustrating a bilayer flexible patch 30 having different elastic moduli according to one embodiment of the present invention.

In one embodiment, the flexible patch 30 having a bilayer structure may include two sub-layers (first flexible layer 831 and second flexible layer 133 in FIG. 10b) with different rigidities.

Here, the first flexible layer 831 that is attached to the skin has a bending strength D1 that is lower than the bending strength D2 of the second flexible layer 832 that is not attached to the skin. For example, the first flexible layer 831 may be configured to have a low modulus of elasticity (e.g., 0.04 MPa) to enable conformable attachment to the skin surface.

On the other hand, the second flexible layer 832 is configured to be stiffer to support the semiconductor circuits and the like integrated on the flexible patch 30 while appropriately controlling the bending of the flexible patch 30 to facilitate handling.

As shown in FIG. 10b, the first flexible layer 831 has an elastic modulus _E1 of 0.04 MPa, and the second flexible layer 832 has an elastic modulus _E2 of 1 MPa, so that the first flexible layer 831 may be formed to be more flexible.

In one embodiment, the flexible patch layer 830 may include a first flexible layer 831 and a second flexible layer 832 including a pre-polymer and a curing agent. Here, the second flexible layer 832 may be configured to have a higher curing agent ratio than the first flexible layer 831. In one example, the first flexible layer 831 may have a pre-polymer to curing agent ratio of 40:1, and the second flexible layer 832 may have a pre-polymer to curing agent ratio of 10:1. The bending strength D of the first flexible layer 831 and the second flexible layer 832 is determined to be different depending on the difference in the curing agent ratio.

Due to these differences in constituent materials, the first flexible layer 831 is relatively soft and sticky compared to the second flexible layer 832, allowing the flexible patch 30 to be attached to the skin. The relatively stiff second flexible layer 832 serves as a support (e.g., a substrate) for integrating micro-scale elements when the flexible patch 30 is used to manufacture a skin sensor or the like.

In addition, the first flexible layer 831 and the second flexible layer 832 may be formed to have different thicknesses. Referring again to the above-mentioned mathematical formula 5, the bending strength D is determined depending on the elastic modulus E and the thickness.

Figure 10c is a diagram for explaining a bilayer structure flexible patch 30 having different thicknesses according to the first embodiment of the present invention, and Figure 10d is a graph showing the characteristics of the flexible patch according to the thickness of the bilayer structure according to the first embodiment of the present invention.

As shown in Fig. 10c, when the bilayer flexible patch 30 is attached to the skin surface, the attached flexible patch 30 is stretched due to the characteristics of the skin surface, which generally has a curved structure. A restoring force _Fret that tries to return to the state before being stretched is applied to the stretched flexible patch 30. The restoring force _Fret can be analyzed as shown in the following Equation 8. When the first flexible layer 831 and the second flexible layer 832 of the flexible patch 30 are made of the same material (e.g., PDMS), they can have the same tensile stress σ and tensile deformation rate ε.
[Mathematical Formula 8]
F _ret = F ₁ + F ₂ = wε(t ₁ E ₁ + t ₂ E ₂ )

Here, _{F1 and} F2 respectively represent the restoring forces applied to the first flexible layer 831 and the second flexible layer 832 attached to the skin, _{t1 and t2} respectively represent the thickness of the first flexible layer 831 and the thickness of the second flexible layer 832.

The total elastic modulus E _eq of the bilayer flexible patch 30 can be expressed by the following mathematical formula 9.

[Mathematical Formula 9]

In one example, when the flexible patch 30 is attached to the skin with an elastic modulus of 0.04 MPa and the first flexible layer 831 is formed with a thickness of 100 μm, the effective elastic modulus and flexural rigidity of the flexible patch 30, and the threshold attachment work between the flexible patch 30 and the skin surface can be obtained by the above mathematical formula 9, and the result is as shown in FIG. 10d.

The first flexible layer 831 and the second flexible layer 832 included in the bilayer structure flexible patch 30 may be formed to have a thickness and elastic modulus suitable for the function of the product (e.g., a skin sensor) in which the flexible patch 30 is utilized, by referring to Equation 9.

The above description of the bilayer flexible patch layer 830 is merely illustrative, and the flexible patch layer 830 of the present invention is not limited to a bilayer structure. In other embodiments, the flexible patch layer 830 may be formed in a monolayer or triple layer structure. In one example, the flexible patch layer 830 may be formed in a monolayer structure including only the second flexible layer 832. In another example, the flexible patch layer 830 may be formed in a triple layer structure including a stiff second flexible layer located between two soft first flexible layers. The triple layer flexible patch layer 830 may include two first flexible layers with different thicknesses. For example, the first flexible layer on the part that is attached to the skin may be formed with a thickness of 10 μm, and the first flexible layer on the opposite side may be formed with a thickness of 100 μm.

In addition, the elastic modulus of 1 MPa disclosed as the elastic modulus for supporting the microelement at the micro level is merely exemplary, and the second flexible layer 832 included in the flexible patch 30 may have other elastic moduli.

In this way, the flexible patch 30 can be manufactured using the sacrificial layer 820, and thus can have high durability without damage occurring during the process of obtaining the flexible patch layer 830 with a micron thickness.

Referring again to FIG. 4, after forming the first substrate 101, the sacrificial layer 105, and the sensor circuit unit 10, the flexible patch 30 may be bonded to the active layer 115 of the sensor circuit unit 10 (S430). The bonding may be performed by a conventional wafer bonding technique. In one embodiment, in order to bond the flexible patch 30 manufactured by the manufacturing process of FIG. 8 to the active layer 115, the semiconductor structure and the flexible patch 30 may be subjected to a plasma treatment (e.g., O2 plasma treatment) to activate the bonding surfaces of the semiconductor structure and the flexible patch 30.

In some embodiments, if the flexible patch 30 is a bilayer structure consisting of a stickier layer and a stiffer layer, the bonding surface of the flexible patch 30 may be one side of the stiffer layer. In other embodiments, if the flexible patch 30 is a triple layer structure consisting of two stickier layers and one stiffer layer, the bonding surface of the flexible patch 30 may be one side of either of the stickier layers.

Also, an insulating layer (e.g., SiO2) may be further formed on the semiconductor structure of FIG. 5d prior to the plasma treatment. In some embodiments, pressure may be further applied to the flexible patch and the semiconductor structure for bonding.

Then, the flexible patch 30 whose surface has been activated by plasma treatment is placed on the semiconductor structure, and the flexible patch 30 is bonded to the semiconductor structure (i.e., the active layer 115) (S430).

Then, the sacrificial layer 105 is removed through a process such as etching, and a skin sensor 1 is obtained that has the flexible patch 30 as a flexible attachment substrate that can be attached to the skin and includes the sensor circuit unit 10 integrated on the flexible attachment substrate (S450).

The etching is performed by adjusting the selectivity of the etching solution so as to etch the sacrificial layer 105 while not etching the components of the skin sensor 1 (including the sensor circuit unit 10 and the flexible patch 30). The etching solution used to etch the sacrificial layer 105 may contain acetone.

The bonding process (S430) may be further performed based on the arrangement between the components of the skin sensor 1 in order to maximize the breathability of the skin sensor 1.

The components of the skin sensor 1 may be arranged based on the operating principle of the skin sensor. As described above with reference to FIG. 2, in the case of manufacturing a skin sensor 1 for sensing deformation of the skin, the flexible patch 30 has through holes arranged on the active layer 115 so that a part of the active layer 115 does not come into contact with the flexible material of the flexible patch 30 (S430). In one example, as described above with reference to FIG. 2, the flexible patch is arranged on the active layer so that the multiple through holes of the flexible patch and the multiple through holes of the insulating layer match in a plane. This allows the deformation result of the active layer 115 located in the air to be maximized.

In addition, the flexible patch 30 is further arranged based on the components under the active layer 115. In one embodiment, to manufacture the skin sensor 1, the through hole H1 of the insulating layer 113 may be arranged on a part (e.g., the extension bar included in the electrodes 111A and 111B) or on the whole of the electrode 111, the active layer 115 may be arranged on the through hole H of the insulating layer 113, and the through hole H2 of the flexible patch 30 may be arranged on the active layer 115. Here, the through hole H1 of the insulating layer 113 may be arranged so that the shaded portion matches the through hole H2 of the flexible patch 30 as shown in FIG. 2b. With this arrangement structure, the skin sensor 1 can effectively obtain skin information based on the operation of the active layer 115, and the high breathability of the skin sensor 1 can be ensured.

Furthermore, in order to place the flexible patch 30 on the semiconductor structure (i.e., on the active layer 115), the flexible patch 30 may be placed on an alignment glass. The surface of the flexible patch 30 may not be flat due to its flexibility. The flatter the surface on which the flexible patch 30 is attached to the skin, the greater the adhesion of the flexible patch 30. Therefore, after placing the flexible patch 30 on the alignment glass using a ruler so that the cross section of the flexible patch 30 is flat, the flexible patch 30 can be transferred onto the semiconductor structure, and the alignment glass can be removed to manufacture a skin sensor 1 having a flexible patch 30 with a flat surface. This maximizes the adhesion of the skin sensor 1.

When the semiconductor element of the electronic device includes a piezoelectric material, the electronic device can be used as a skin sensor that can obtain deformation and/or elasticity information of the skin by being attached to the skin. The skin sensor 1 manufactured through the above-described process can operate as a sensor while attached to the skin. The piezoelectric material, whose deformation is sensed, is placed on a relatively large through hole, and the skin sensor can more efficiently obtain skin deformation information according to the physiological behavior of the skin.

In addition, the skin sensor 1 according to various embodiments of the present invention can be used to measure not only skin tension but also skin elasticity.

Second Example
11a and 11b are schematic conceptual diagrams illustrating a manufacturing process of a skin sensor according to a second embodiment of the present invention.

Referring to Figures 4 and 11, the method for manufacturing a skin sensor according to the second embodiment of the present invention is substantially similar to the method for manufacturing a skin sensor according to the first embodiment of Figure 4, so differences will be mainly described.

As shown in FIG. 4, the active layer 115 of the sensor circuit unit 10 is formed to be located closest to the flexible patch 30 among the components of the sensor circuit unit 10.

However, in other embodiments, the active layer 115 of the sensor circuit unit 10 may be formed to be located farthest from the flexible patch 30 among the components of the sensor circuit unit 10. That is, the skin sensor 1 of Figures 1b and 1c can be manufactured.

The method for manufacturing the skin sensor 1 that can be attached to the skin according to the second embodiment includes, as in the first embodiment, the step of forming a sacrificial layer 105 on the substrate 101 (S1101); the step of forming the sensor circuit unit 10 on the sacrificial layer 105 (S1110); the step of bonding the sensor circuit unit 10 and a flexible patch 30 including a through hole (S1130); and the step of etching the sacrificial layer 105 to manufacture the skin sensor 1 (S1150).

In the above embodiment, the step of forming the sensor circuit unit 10 on the sacrificial layer 105 (S1110) may include the steps of forming an active layer 115 on the sacrificial layer 105 (S1111); forming an insulating layer 113 on the active layer 115 (S1113); and forming electrodes 111 and/or interconnects 112 on the insulating layer 113 (S1115).

In this manner, the skin sensor 1 may be manufactured such that the active layer 115 is located at the top of the skin sensor 1. The skin sensor 1 manufactured according to the second embodiment has the same structure except that the positions of the circuit components (i.e., the electrodes 111 and/or the interconnects 112) and the active layer 115 are swapped. Therefore, the operating principle of the skin sensor 1 in FIG. 11 is the same as that of the skin sensor 1 in FIG. 2, and a detailed description will be omitted.

In the method for manufacturing an electronic device that can be attached to the skin according to the above-mentioned embodiment, the process for forming the semiconductor element and the process for manufacturing the flexible patch 30 including a plurality of through holes are separated. However, according to another embodiment of the present invention, the electronic device according to the first or second embodiment may be manufactured by an all-in-one process.

<Third Example>
12a to 12h are conceptual diagrams illustrating a manufacturing process of a skin sensor according to a third embodiment of the present invention.

Referring to Figures 4 and 12, the method for manufacturing a skin sensor according to the third embodiment of the present invention is substantially similar to the method for manufacturing a skin sensor according to the first embodiment of Figure 4, so the differences will be mainly described.

According to the method for manufacturing a skin sensor according to the second embodiment, a skin sensor 1 having a structure similar to that of the first embodiment can be manufactured. However, referring to FIG. 12, the method for manufacturing a skin sensor 1 according to the third embodiment of the present invention is composed of an all-in-one manufacturing process in which the process for manufacturing a flexible patch 30 and the process for manufacturing a semiconductor structure including a sensor circuit unit 10 are not separated. In other words, it is distinguished from the method for manufacturing a skin sensor 1 according to the first embodiment in which the process for manufacturing a flexible patch 30 and the process for manufacturing a semiconductor structure are separated.

Referring to Figures 12a to 12h, in the third embodiment, a method for manufacturing a skin sensor 1 that can be attached to skin includes the steps of forming a sacrificial layer 105 on a substrate 101 (S1201); forming a sensor circuit unit 10 on the sacrificial layer 105 (S1210), which includes forming electrodes 111 and/or interconnects 112 on the sacrificial layer 105 (S1211); forming an insulating layer 113 on the electrodes and/or interconnects (S1213); and forming an active layer 115 on the insulating layer 113 (S1215). It also includes a step (S1230) of forming a flexible patch layer 830 on the sensor circuit unit 10 (i.e., on the active layer 115); a step (S1240) of abutting a mold 810 against the flexible patch layer 830 to form a plurality of through holes; a step (S1250) of etching the sacrificial layer 105 to manufacture the skin sensor 1; and a step (S1270) of removing the mold 810.

In this way, the skin sensor 1 manufactured by the manufacturing method of the skin sensor 1 of the third embodiment corresponds to a monolithic electronic device in which all circuit elements and interconnections are formed on the flexible patch 30, which is a flexible attachment substrate. The manufacturing method of the skin sensor 1 of the third embodiment has the advantages of being able to produce a compact and lightweight electronic device, increasing the integration and reliability of the electronic device, and enabling mass production at low cost.

Referring to FIG. 12a, in one embodiment, the sacrificial layer 105 is formed taking into consideration photolithography, etching selectivity, thermal stability, and the like. In one example, the sacrificial layer 105 may be made of a material including one or more of Cr, Al, Ni, Au, and combinations thereof. In some embodiments, the sacrificial layer 105 may be further formed taking into consideration costs. In this case, the sacrificial layer 105 may be made of a material including one or more of Cr, Al, Ni, and combinations thereof, for example.

In step (S1210), a sensor circuit unit 10 (i.e., a polycrystalline semiconductor structure) including a polycrystalline active layer 115 is deposited on the metal sacrificial layer 105. In one embodiment, electrodes 111 and interconnects 112, an insulating layer 113, and an active layer 115 (e.g., acting as a sensing material) are sequentially formed on the sacrificial layer 105.

In one example, the polycrystalline active layer 115 may be formed by transfer using a stressor, as in the first embodiment.

In another example, the polycrystalline semiconductor material can be grown without regard to a substrate, and thus is grown directly on the sacrificial layer 105. For example, the polycrystalline active layer 115 may be directly deposited by a physical vapor deposition (PVD) method such as sputtering or evaporation, or a chemical vapor deposition (CVD) method such as low-pressure CVD or plasma-enhanced CVD. In some examples, the growth of the polycrystalline active layer 115 may be performed at a temperature of 500° C. or less.

In one example, each layer is formed such that the insulating layer 113 has through holes corresponding to the through holes of the flexible patch 30 to ensure breathability, as shown in FIG. 12c.

Steps (S1201 and S1210) are performed by etching a photolithography substrate.

Then, a flexible patch layer 830 is formed on the sensor circuit unit 10 (S1230). The flexible patch layer 830 is a flexible patch 30 without a through hole. The flexible patch layer 830 is formed directly on the sensor circuit unit 10 (S1230). The process of forming the flexible patch layer 830 and the components, structure, thickness, etc. of the flexible patch layer have been described above with reference to Figures 8 and 10, so detailed description will be omitted.

After the flexible patch layer 830 is formed, through holes may be formed in the flexible patch layer 830.

In step (S1240), the through-holes may be formed by a soft lithography process. In one example, the through-holes may be formed by a soft lithography process using a micromolding.

Specifically, in one embodiment, the mold 810 is brought into contact with the flexible patch layer 830 to form through holes (S1240). The mold 810 may be configured with a groove structure having a planar shape as shown in FIGS. 9a and 9c. The depth of the groove of the mold 810 may be greater than or equal to the thickness from the sensor circuit unit 10 (i.e., the active layer 115) to the flexible patch layer 830.

The mold 810 contacts the flexible patch layer 830 to reach the sensor circuit unit 10 (i.e., the active layer 115) to form a through hole. That is, the mold 810 is similar to pressing a stamp into a soft material. When the mold 810 contacts the flexible patch layer 830, the frame portion of the groove penetrates the flexible patch layer 830 to form a through hole in the flexible patch layer 830.

In step (S1240), a process of heating the flexible patch layer 830 may be further performed so that the frame area of the groove of the mold 810 can more easily penetrate the flexible patch layer 830.

Although FIG. 12 shows a mold 810 in which only a through hole in which the active layer 115 is disposed is shown, this is merely for clarity of explanation. Step (S1240) may use a mold 810 in which one or more through holes can be formed to enhance breathability.

In step (1240), the through holes may be formed to produce the free-standing skin sensor 1. That is, at least one of the through holes formed by the mold 810 is positioned on the zigzag bar of the electrode 111, as described with reference to FIG. 2.

In one embodiment, the through-hole is formed on a portion of the electrode 111 based on one or more key holes included in the mold 810 and one or more alignment keys included in the semiconductor structure. This allows the skin sensor 1 to have a freestanding structure. The structure of the skin sensor 1 manufactured by the manufacturing method according to the second embodiment is the same as the structure of the skin sensor 1 of the first embodiment, so that skin information can be obtained according to the same operating principle.

In the above embodiment, the mold 810 may include one or more key holes. The key holes may be through holes different from the through holes of the flexible patch 30 for breathability of the skin sensor 1, and may be configured with a different plane (e.g., a cross) as shown in FIG. 12.

In the above embodiment, one or more keys that match the keyholes of the mold 810 may be formed in the semiconductor structure prior to step S1040. In one embodiment, one or more keys having a planar shape that matches the shape of the keyhole holes may be formed in step S1211. The one or more keys may be formed of the same material and/or in the same manner as the material that forms the electrodes 111 and/or the interconnects 112.

After the mold 810 and the flexible patch layer 830 are brought into contact to form a through hole in step (S1240), the sacrificial layer 105 is etched (S1250). After removing the sacrificial layer 105, the mold 810 is removed to manufacture the skin sensor 1.

In this way, in the manufacturing method according to the second embodiment, a semiconductor circuit is formed on the substrate 101 using photography, and a biocompatible PDMS patch 30 that does not inhibit the breathability of the skin is formed directly on the semiconductor circuit using soft lithography, thereby manufacturing the skin sensor 1. This eliminates the need to fabricate the semiconductor circuit (i.e., the sensor circuit unit 10) and the flexible patch separately and then bond them together, reducing the complexity of the process and achieving a high device transfer yield.

<Fourth Example>
13a to 13k are conceptual diagrams illustrating a manufacturing process of a skin sensor according to a fourth embodiment of the present invention.

Referring to Figures 12 and 13, the method for manufacturing the skin sensor according to the fourth embodiment of the present invention is substantially similar to the method for manufacturing the skin sensor according to the third embodiment of Figure 12, so the differences from the third embodiment will be mainly described with respect to the manufacturing process.

According to the manufacturing method of the skin sensor of the fourth embodiment, a skin sensor 1 having the same structure as that of the second embodiment can be manufactured. That is, the skin sensor 1 shown in Figures 1b and 1c can be manufactured.

The method for manufacturing the skin sensor 1 according to the fourth embodiment of the present invention is an all-in-one manufacturing process in which the process for manufacturing the flexible patch 30 and the process for manufacturing the semiconductor structure including the sensor circuit unit 10 are not separated. In other words, it is different from the method for manufacturing the skin sensor 1 according to the second embodiment in which the process for manufacturing the flexible patch 30 and the process for manufacturing the semiconductor structure are separated.

In the fourth embodiment, a method for manufacturing a skin sensor 1 that can be attached to skin includes the steps of forming a sacrificial layer 105 on a substrate 101 (S1301); forming a sensor circuit unit 10 (S1310); forming a flexible patch layer 830 on the sensor circuit unit 10 (S1330); abutting a mold 810 against the flexible patch layer 830 to form a plurality of through holes (S1340); etching the sacrificial layer 105 to manufacture the skin sensor 1 (S1350); and removing the mold 810 (S1370).

On the other hand, the skin sensor 1 of the fourth embodiment has the same structure as the skin sensor 1 of the second embodiment. Therefore, in the sensor circuit unit 10 of the fourth embodiment, after forming the sacrificial layer 105, the active layer 115, the insulating layer 113, and the circuit components (electrodes 111 and/or interconnects 112) are laminated in this order (S1310). That is, step (S1310) includes a step of forming the active layer 115 (S1311); a step of forming the insulating layer 113 on the active layer 115 (S1313); and a step of forming the electrodes 111 and/or interconnects 112 on the insulating layer 113 (S1315).

According to the fourth embodiment, the skin sensor 1 can be manufactured using an active layer 115 having a single crystal structure. Single crystal materials cannot be grown directly on the metal sacrificial layer 105.

To grow a single crystal semiconductor material, a substrate identical or similar to the single crystal semiconductor and a minimum temperature of 700°C or higher are required. Therefore, instead of forming the single crystal active layer 115 directly on the metal sacrificial layer 105, a 2DLT stressor transfer using a stressor is performed to form the active layer 115 on the metal sacrificial layer 105.

Specifically, as shown in FIG. 13c, first, a polyamide layer 109 is formed on the sacrificial layer 105 (S1309), and then a process is added in which the single crystal thin film (i.e., active layer 115) detached in the 2DLT process is transferred to the polyamide layer 109 to form the active layer 115 (S1311).

In one embodiment, the polyamide layer 109 may be made of a material containing polyamide. For example, the polyamide layer 109 may be a compound containing various fillers and may be formed in an uncured structure.

In addition, step (S1311) further includes a step of patterning the active layer 115 so that the width of the active layer 115 is smaller than the width of the through hole of the flexible patch 30. The width of the active layer 115 formed in FIG. 13c is reduced by patterning as shown in FIG. 13d.

Next, as shown in FIG. 13e, an insulating layer 113 having through holes that match the through holes of the flexible patch 30 is formed. Then, as shown in FIG. 13k, through holes that penetrate the insulating layer 113 and the flexible patch 30 can be formed on the patterned active layer 115. This is because, as described above with reference to FIG. 5b, the through holes of the insulating layer 113 are formed to match the through holes of the flexible patch 30 so as not to interfere with the flow of air moving through the through holes of the flexible patch 30.

In step (S1311), the active layer 115 is transferred onto the polyamide layer 109 using a transfer structure including the active layer 115, the stressor layer 730, and the tape layer 750. The stressor layer 730 and the tape layer 750, except for the active layer 115, are then removed to position only the active layer 115 on the polyamide layer 109. The formation of the active layer 115 using the transfer structure is similar to the content described with reference to FIG. 7, so a detailed description will be omitted.

The method for manufacturing the skin sensor 1 according to the fourth embodiment further includes a step (S1360) of removing the polyamide layer 109. In one embodiment, the polyamide layer 109 is removed by plasma etching (including, for example, O2 plasma etching).

As described above, according to the embodiment of the present invention, an electronic device 1 that can be attached to the skin can be obtained. The electronic device 1 can be manufactured by a process in which the process of forming the semiconductor circuit unit 10 and the process of forming the flexible patch 30 are separate, or an electronic device 1 including the semiconductor circuit unit 10 and the flexible patch 30 can be obtained by an integrated process.

The present invention has been described above with reference to the embodiments shown in the drawings. However, these embodiments are merely illustrative, and a person having ordinary knowledge in the field should understand that various modifications are possible from the embodiments. Such modifications should be considered to be within the technical scope of protection of the present invention. Therefore, the true technical scope of protection of the present invention should be determined by the technical ideas of the appended claims.

The electronic device according to the embodiment of the present invention is formed on a flexible patch that has mechanical properties similar to those of the skin and has through holes that provide strong adhesion and high breathability. Such electronic devices can be used as various electronic devices that are attached to the skin, such as skin sensors, and can be used in a wide variety of technical fields where skin-related electronic devices can be used, such as the healthcare and beauty fields.

Claims (31)

A semiconductor circuit unit - the semiconductor circuit unit includes a circuit element including one or more of an electrode and an interconnect; and a semiconductor element including an insulating layer and an active layer;
and a flexible patch configured to be attachable to the skin, the flexible patch including a plurality of through holes;
The insulating layer includes a plurality of through holes that match at least a portion of the plurality of through holes of the flexible patch, and the interconnect includes a plurality of through holes that match the plurality of through holes of the insulating layer. The electronic device that can be attached to the skin according to claim 1, characterized in that the multiple through-holes of the flexible patch include circular through-holes, and the spacing between the multiple through-holes is less than 60 μm. The electronic device that can be attached to the skin according to claim 2, characterized in that the multiple through-holes of the flexible patch further include dumbbell-shaped through-holes. the plurality of through holes of the flexible patch includes a combination of first through holes having a first diameter and second through holes having a second diameter;
The electronic device attachable to the skin according to claim 2 , wherein the first diameter is larger than the second diameter, and the second through-hole is positioned around the first through-hole. The electronic device that can be attached to the skin according to claim 1, characterized in that the flexible patch is placed on the active layer so that at least some of the multiple through holes of the flexible patch match the planar shape of the multiple through holes of the insulating layer. The electronic device that can be attached to the skin according to claim 1, characterized in that the active layer is made of a material containing AlN or GaN. The circuit element includes a first electrode and a second electrode located opposite the first electrode;
the first electrode includes one or more first bars;
the second electrode includes one or more second bars;
2. The skin-attachable electronic device of claim 1, wherein the first bar extends toward the second electrode with a plane of the first bar having a zigzag shape, and the second bar extends toward the first electrode with a plane of the second bar having a zigzag shape. The device according to claim 7 , wherein the zigzag shape of the first bar or the second bar includes a hinge pattern located at a point where the extending direction of the bar changes. The flexible patch includes a first flexible layer having a first modulus of elasticity and a second flexible layer having a second modulus of elasticity;
The electronic device according to claim 1 , wherein the first elastic modulus is lower than the second elastic modulus. The thickness t1 of the first flexible layer and the thickness t2 of the second flexible layer are determined based on the following mathematical formula:
[Mathematical formula]

10. The electronic device attachable to the skin according to claim 9, characterized in that, in the above formula, t is the thickness of the flexible patch, _E1 is the elastic modulus of the first flexible layer, _E2 is the elastic modulus of the second flexible layer, R is the curvature of the flexible patch attached to the skin, _γdSkin is the dispersion component of the contact surface of the skin, _γdPatch is the dispersion component of the contact surface of the patch, _γpSkin is the polar component of the contact surface of the skin, and _γpPatch is the polar component of the contact surface of the patch. forming a sacrificial layer on a first substrate;
forming a semiconductor circuit unit including a semiconductor element and a circuit element on the sacrificial layer;
attaching a flexible patch including a plurality of through holes onto the semiconductor circuit unit ;
and etching the sacrificial layer to fabricate an electronic device including the semiconductor circuit unit and a flexible patch.
The step of forming the semiconductor circuit unit includes:
forming circuit elements on the sacrificial layer, the circuit elements including one or more of electrodes and interconnects;
forming an insulating layer over the circuit element, the insulating layer being formed to have a plurality of through holes matching at least a portion of the plurality of through holes of the flexible patch;
and forming an active layer on the insulating layer;
Including,
A method of manufacturing a skin-attachable electronic device, wherein the circuit element includes one or more of an electrode and an interconnect, and the interconnect has a plurality of through holes formed therein that match the plurality of through holes in the insulating layer. The step of forming the active layer includes:
forming an active layer on a second substrate;
forming a stressor layer on the active layer;
placing a tape on the stressor layer;
peeling the active layer and the stressor layer from the second substrate using the tape;
transferring the exfoliated active layer and stressor layer onto the insulating layer - the exfoliated active layer is transferred onto the insulating layer;
and peeling the stressor layer from the active layer using the tape. The stressor layer is made up of a plurality of layers,
The step of forming the stressor layer comprises:
forming a first stressor layer on the active layer by evaporating;
13. The method of claim 12, comprising: forming a second stressor layer on the first stressor layer by sputtering deposition; and forming a third stressor layer on the second stressor layer by sputtering deposition. the second stressor layer is made of a material containing Al;
The method of claim 13 , wherein the third stressor layer is made of a material including Ni. The method for manufacturing a skin-attachable electronic device according to claim 14, characterized in that the first stressor layer is made of a material containing Ni or AgNi. The method for manufacturing a skin-attachable electronic device according to claim 11, wherein the bonding step further includes a step of applying pressure between the flexible patch and the semiconductor circuit unit. The method for manufacturing a skin-attachable electronic device according to claim 11, further comprising a step of subjecting the semiconductor circuit unit and the flexible patch to a plasma treatment before bonding. The bonding step includes:
The method for manufacturing a skin-attachable electronic device according to claim 11, characterized in that the flexible patch is placed on the active layer such that at least a portion of the multiple through holes of the flexible patch match the planar shape of the multiple through holes of the insulating layer. The method for manufacturing a skin-attachable electronic device according to claim 11, characterized in that the sacrificial layer is made of any one of Ni, Cr, Al, and combinations thereof. The step of forming the semiconductor circuit unit includes:
forming an active layer on the sacrificial layer;
forming an insulating layer over the active layer;
and forming circuit elements on the insulating layer, the circuit elements including one or more of electrodes and interconnects;
12. The method of manufacturing a skin-attachable electronic device according to claim 11, comprising: forming a sacrificial layer on a first substrate;
forming a semiconductor circuit unit including a circuit element and a semiconductor element on the sacrificial layer;
forming a flexible patch layer on the semiconductor circuit unit;
contacting a mold containing grooves forming a plurality of through holes with the flexible patch layer, the mold portions excluding the grooves penetrating through said flexible patch layer;
and a method of manufacturing a skin-attachable electronics comprising the steps of: etching the sacrificial layer to produce an electronics. The step of forming the semiconductor circuit unit on the sacrificial layer includes:
forming circuit elements on the sacrificial layer, the circuit elements including one or more of electrodes and interconnects;
forming an insulating layer over the circuit elements, the insulating layer including a plurality of through holes corresponding to at least a portion of the plurality of through holes in the flexible patch layer to be formed by the mold;
and forming an active layer on the insulating layer;
22. The method of claim 21, wherein the interconnect is formed with a plurality of through holes corresponding to a plurality of through holes in the insulating layer. The step of forming the semiconductor circuit unit on the sacrificial layer includes:
forming an active layer on the sacrificial layer; forming an insulating layer on the active layer, the insulating layer including a plurality of through holes corresponding to a plurality of through holes of the flexible patch layer to be formed by the mold;
and forming a circuit element on the insulating layer, the circuit element including one or more of an electrode and an interconnect, the interconnect having a plurality of through holes formed therein corresponding to the plurality of through holes in the insulating layer;
22. A method of manufacturing a skin-attachable electronic device according to claim 21, comprising: 24. The method of claim 23, further comprising the steps of: forming a polyamide layer on the sacrificial layer before forming an active layer; and removing the polyamide layer after contacting the mold with the flexible patch layer. The step of forming the active layer includes:
25. The method of manufacturing a skin-attachable electronic device of claim 24, comprising forming the active layer on the polyamide layer using a transfer structure. 24. The method for manufacturing a skin-attachable electronic device according to claim 23, further comprising a step of patterning the active layer so that the width of the active layer is smaller than the width of the through-hole formed by the mold. The step of contacting the mold including the plurality of grooves with the flexible patch layer includes:
22. The method of manufacturing a skin-attachable electronic device of claim 21, comprising the step of heating the flexible patch layer. The method for manufacturing an electronic device that can be attached to the skin according to claim 21, characterized in that the surface of the mold is formed with grooves that can form multiple circular through holes, multiple dumbbell-shaped through holes, and combinations thereof. forming one or more alignment keys for alignment of the through-type;
The array key is configured to have a height;
22. The method of claim 21, wherein the mold further comprises one or more key holes corresponding to planes of the array keys. The method for manufacturing an electronic device that can be attached to the skin according to claim 21, characterized in that the width of the groove forming the through hole is less than 60 μm. The step of forming the flexible patch layer includes:
forming a third flexible layer having a third elastic modulus on the semiconductor circuit unit;
and forming a fourth flexible layer on the third flexible layer, the fourth flexible layer having a fourth modulus of elasticity;
22. The method of claim 21, wherein the fourth modulus of elasticity is lower than the third modulus of elasticity.

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