US20170301955A1

US20170301955A1 - Thin film battery device and method of formation

Info

Publication number: US20170301955A1
Application number: US15/338,977
Authority: US
Inventors: Byung-Sung Kwak; Lizhong Sun; Giback Park; Dimitrios Argyris; Michael Yu-Tak Young; Jeffrey L. Franklin
Original assignee: Applied Materials Inc
Current assignee: Elevated Materials Us LLC
Priority date: 2016-04-14
Filing date: 2016-10-31
Publication date: 2017-10-19
Also published as: WO2017180959A2; US20170301895A1; US20170301926A1; US20170301892A1; US20170301954A1; TW201803191A; WO2017180973A1; WO2017180941A1; US20170301893A1; WO2017180947A1; US20170301894A1; WO2017180967A2; WO2017180962A3; US20170301957A1; TW201807861A; TW201737530A; TWI796295B; TW201810768A; WO2017180975A3; WO2017180945A1

Abstract

A thin film battery may include: a contact layer, the contact layer disposed in a first plane and comprising a cathode current collector and an anode current collector pad; a device stack disposed on the cathode current collector, the device stack comprising a cathode and solid state electrolyte; an anode current collector disposed on the device stack; a thin film encapsulant, the thin film encapsulant disposed over the device stack, wherein the solid state electrolyte encapsulates the cathode.

Description

RELATED APPLICATIONS

This Application claims priority to U.S. provisional patent application 62/322,415, filed Apr. 14, 2016, entitled Volume Change Accommodating TFE Materials, and incorporated by reference herein in its entirety.

FIELD

The present embodiments relate to thin film encapsulation (TFE) technology used to protect active devices, and more particularly to encapsulating thin film battery devices.

BACKGROUND

In the fabrication of thin film batteries, patterning of device structures remains a challenge, for forming active regions of a device, or front-end, and for forming encapsulation portions of a device, or back-end.
In particular, for seamless integration into systems incorporating thin film batteries, a large benefit is the ability to form very thin batteries. To this end, reduction of non-active materials such as encapsulation material is useful, so non-active portions of a thin film battery add minimally to the overall size of the battery. Known methods of packaging energy storage devices, such as thin film batteries, include pouching, lamination, and the like. These methods add an undesirable amount of weight and volume to the device being packaged, or encapsulated. Thin film based encapsulation approaches for protecting active components of a thin film battery offer a potentially simplified manner of encapsulation, with minimum material and volume addition to the system. Notably, thin film encapsulation approaches for these types of devices, such as thin film batteries, are far more challenging for several reasons. Firstly, accommodation of volume changes taking place during battery operation is useful, in order to reduce potential stress to a thin film encapsulant during device operation. Secondly, a main function of the thin film encapsulant is to provide good oxidant permeation barrier properties. Moreover, a thin film encapsulant may be used to encapsulate device structures including a larger topography variation. At the present, robust thin film encapsulant fabrication methods and the resulting device architectures are lacking for providing robust and uniform long-term operation of these devices.
With respect to these and other considerations the present disclosure is provided.

BRIEF SUMMARY

In one embodiment, a thin film battery, may include a contact layer, where the contact layer is disposed in a first plane and comprising a cathode current collector and an anode current collector pad. The thin film battery may further include a device stack disposed on the cathode current collector, the device stack comprising a cathode and solid state electrolyte; an anode current collector disposed on the device stack. The thin film battery may also include a thin film encapsulant, where the thin film encapsulant is disposed over the device stack, wherein the solid state electrolyte encapsulates the cathode.
In another embodiment, a method of forming a thin film battery may include depositing a contact layer on a substrate and forming a device stack over the contact layer, where the device stack comprising a cathode, a solid state electrolyte and an anode current collector, wherein the solid state electrolyte encapsulates the cathode. The method may also include forming a thin film encapsulant on the substrate after the forming the device stack.
In another embodiment, a method of forming a thin film battery may include depositing a contact layer on a substrate and depositing a cathode layer on the contact layer. The method may also include patterning the contact layer and the cathode layer, wherein the substrate is exposed, and wherein the contact layer forms a cathode current collector and an anode current collector pad, and the cathode layer forms a cathode. The method may also include depositing a solid state electrolyte layer on the substrate after the patterning the contact layer and the cathode layer patterning the solid state electrolyte layer, wherein the anode current collector pad is exposed. The method may further include depositing an anode current collector layer on the substrate after the patterning the solid state electrolyte layer and patterning the anode current collector layer and the solid state electrolyte layer, wherein the cathode current collector is exposed. The method may also include depositing a polymer layer on the substrate after the patterning the anode current collector layer and the solid state electrolyte layer and patterning the polymer layer to form a patterned polymer layer, wherein the cathode current collector is exposed in a first region.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a cross-section of a thin film battery according to various embodiments of the disclosure;

FIG. 1B provides a plan view of a thin film battery according to embodiments of the disclosure;

FIG. 1C provides a plan view of a thin film battery arrangement in a substrate according to embodiments of the disclosure;

FIGS. 2A-2K illustrate a cross-sectional view of a thin film battery at various stages of assembly;

FIG. 3 illustrates a cross-section of another thin film battery according to additional embodiments of the disclosure;

FIG. 3 shows an exemplary process flow according to embodiments of the disclosure.

FIGS. 4A-4D illustrate a cross-sectional view of another thin film battery at various stages of assembly;

FIG. 4E provides a plan view of the thin film battery of FIG. 4D;

FIG. 5 illustrates a cross-section of a thin film battery according to various additional embodiments of the disclosure;

FIG. 6A-6D illustrate a cross-sectional view of another thin film battery at various stages of assembly; and

FIG. 7 illustrates an exemplary process flow.

DETAILED DESCRIPTION

The present embodiments will now be described more fully hereinafter with reference to the accompanying drawings, where some embodiments are shown. The subject matter of the present disclosure may be embodied in many different forms and are not to be construed as limited to the embodiments set forth herein. These embodiments are provided so this disclosure will be thorough and complete, and will fully convey the scope of the subject matter to those skilled in the art. In the drawings, like numbers refer to like elements throughout.
The present embodiments are related to thin film encapsulation (TFE) technology, where a thin film encapsulant is used to minimize ambient exposure of active devices. The present embodiments provide novel structures and materials combinations for thin film encapsulation.
Examples of active devices include electrochemical devices include electrochromic windows and thin film batteries wherein the active component materials are highly sensitive/reactive to moisture or other ambient materials. To this end, known electrochemical devices such as thin film batteries may be provided with encapsulation to protect the active component materials.
In various embodiments, a thin film device such as a thin film battery and techniques for forming a thin film battery are provided with a novel architecture including an encapsulant material. The thin film battery may include a layer stack composed of active layers, as well as the thin film encapsulant, where the thin film encapsulant may also constitute a multilayer structure.
In various embodiments novel combinations of thin film deposition and patterning operations are provided, for formation of an active device region, a thin film encapsulant, or a combination of active device region and thin film encapsulant. In particular, techniques are provided for forming thin film batteries, where the techniques provide an improvement in the structure, the ease of manufacturing, performance, or a combination of these factors, as compared to known thin film batteries. Various considerations may affect the design of a thin film battery. A non-exhaustive list of factors includes the ability of the battery to accommodate local volume changes within specific regions of the thin film battery taking place during operation of a battery; protection from oxidative permeation; and ability to form a device accounting for large variations in topography. Further factors include the ability to limit the non-active material in a thin film battery to an acceptable level; ability from a thin film battery having an acceptable portion of non-active material within the device regions; and the ability to manufacture a thin film battery using cost-effective techniques. In particular embodiments disclosed herein, the formation of thin film encapsulation is integrated with the formation of active device regions of a thin film battery in a novel manner enabling a more robust architecture for operation and stability of the thin film battery.
FIG. 1A illustrates a cross-section of a thin film battery 130 according to various embodiments of the disclosure. FIG. 1B provides a plan view of a variant of a thin film battery according to embodiments of the disclosure. In particular, FIG. 1A illustrates an arrangement 100 where at least one thin film battery, shown as thin film battery 130, is arranged on a substrate 102. FIG. 1C provides a plan view of a thin film battery arrangement 150 in a substrate according to embodiments of the disclosure. The arrangement of FIG. 1C may include a matrix of thin film batteries, such as thin film batteries 130.
Turning now to FIG. 1A, the substrate 102, used for supporting the thin film battery 130, may be an insulator, semiconductor, or a conductor, depending upon the targeted electrical properties of the exterior surfaces. More specifically, the substrate 102 may be made from a ceramic, metal or glass, such as, for example, aluminum oxide, silicate glass, or even aluminum or steel, depending on the application. The substrate 102 may include any number of parts or layers, including adhesion layer(s) (not shown) as an interface to layers to be formed on the substrate 102.
As shown in FIG. 1A, the thin film battery 130 may include a contact layer 104, where the contact layer 104 is disposed in a first plane (parallel to the X-Y plane of the Cartesian coordinate system shown). The contact layer 104 may be arranged in different parts and may include a cathode current collector 106 and an anode current collector pad 108. The contact layer 104 may be formed from a known metal or metal alloy used in known thin film batteries. The thin film battery 130 may further include a device stack 110, where the device stack 110 is disposed on the cathode current collector 106. As shown, the device stack 110 may include a cathode 112 and solid state electrolyte 114. For example, in embodiments where the thin film battery 130 is a lithium battery, the cathode 112 may be a LiCoO₂material containing lithium, where the lithium diffuses back and forth between the cathode 112 an anode current collector 116 during charging and discharging. During operation, the lithium may diffuse through the solid state electrolyte 114, where the solid state electrolyte 114 may be a known lithium phosphorous oxynitride (LiPON) material appropriate for conducting the lithium between the cathode 112 and an anode region 115 in the device stack 110.
While not shown in FIG. 1A as a distinct layer, according to embodiments of the disclosure, a thin film battery such as thin film battery 130, may include the anode region 115, shown in the dashed area, where the anode region 115 is disposed between the solid state electrolyte 114 and anode current collector 116. The anode region 115 may represent a region where lithium, accumulates within, or diffuses away from, as the thin film battery 130 charges and discharges. This reversible transport of material such as lithium may cause changes in dimensions in the anode region 115, where such changes may be on the order of microns, leading to distortions within the thin film battery, including in the thin film encapsulant 120. Notably, in additional embodiments as disclosed below in FIG. 4A, FIG. 5, and FIG. 6A, an anode region is understood to exist between an anode current collector and solid state electrolyte.
As shown in FIG. 1A, at least a portion of the anode current collector 116 is disposed on the device stack 110. As also shown in FIG. 1A, the thin film battery 130 may further include a thin film encapsulant, shown as thin film encapsulant 120, where the thin film encapsulant 120 is disposed over a top portion of the device stack 110. More particularly, the thin film encapsulant 120 may be disposed directly on the anode current collector 116. As shown, the thin film encapsulant 120 may encapsulate the device stack 110 on a first side (to the left in FIG. 1A) of the device stack 110. As further shown in FIG. 1A, the thin film battery 130 may be advantageously formed in a manner wherein the anode current collector 116 encapsulates the device stack 110 along a second side.
As further shown in FIG. 1A, a hallmark of the thin film battery 130 is the structure of the solid state electrolyte 114, where the solid state electrolyte 114 encapsulates the cathode 112. Advantageously, the cathode sidewalls 111 of cathode 112 may accordingly be protected by the solid state electrolyte 114 when the thin film encapsulant 120 is breached be species from outside of the thin film battery 130. Further advantageously, during cycling of the thin film battery 130, when Li species are transported from the cathode 112 toward the anode current collector 116, the Li species may become “trapped” between the solid state electrolyte 114 and the metal layer of the anode current collector 116.
As further shown in FIG. 1A, the thin film battery 130 may include a cathode contact 122 and anode contact 124, which contacts may be formed of a known metal, such as silver. The embodiments are not limited in this context. According to some embodiments of the disclosure, the thin film encapsulant 120 may be formed from at least one dyad, where a given dyad includes a polymer layer and a rigid layer, such as a rigid dielectric layer or rigid metal layer disposed adjacent the polymer layer. In various embodiments, the dyad may act as a “functional dyad” where at least one layer of the functional dyad provides a diffusion barrier to contaminants such as moisture and gas species, and at least one layer includes a soft and pliable layer for accommodating changes in dimension of an active device region in a reversible manner. Examples of a dyad include a combination of a polymer layer for a first layer, and a rigid diffusion barrier layer, such as a dielectric layer or a rigid metal layer for the second layer, or combinations of a rigid metal layer and rigid dielectric layer. In specific embodiments, the term “polymer layer” may refer to just one polymer layer or to a polymer layer stack including multiple sub-layers of different polymers, where at least one sub-layer is soft and pliable. A rigid metal layer may include Cu, Al, Pt, Au, or other metal. The embodiments are not limited in this context. In particular embodiments the polymer layer may constitute a soft and pliable polymer, or at least one polymer sub-layer of a polymer layer may be formed from a soft and pliable polymer, where a soft and pliable polymer is characterized by a relatively lower elastic modulus. Suitable polymers with low elastic modulus include silicone, hardness of ˜A40 Shore A, Young's Modulus of ˜0.9 Kpsi or ˜6.2 MPa; Parylene-C: hardness of ˜Rockwell R80, Young's Modulus of ˜400 Kpsi or ˜2.8 GPa; KMPR: Young's Modulus of ˜1015 Kpsi or ˜7.0 GPa; polyimide: hardness of D87 Shore D, Young's Modulus of ˜2500 Kpsi or ˜17.2 GPa). Other useful properties include a relatively larger elongation to break (e.g. Silicone, 100 to 210%; Parylene-C, 200%; polyimide, 72%; acrylic, 2.0 to 5.5%; epoxy, 3 to 6%), and related properties. In the example of FIG. 1A the thin film encapsulant includes three dyads, while in other embodiments a greater number or fewer number of dyads may be used to form a thin film encapsulant.
More particularly, as used herein, a “soft and pliable” material may refer to a material having an elastic (Young's) modulus less than 20 GPa, for example, while a “rigid material.” such as a rigid metal layer or rigid dielectric layer, may have an elastic modulus greater than 20 GPa. Other characteristic properties associated with a soft and pliable material include a relatively high elongation to break, such as 70% or greater for at least one polymer layer of the thin film encapsulant. In some examples, such as silicone, a soft and pliable material may have an elongation to break up to 200% or greater.
Turning now to FIG. 1B, there is shown a plan view of a variant of the thin film battery 130, showing a cathode current collector region 132 and an anode current collector region 134, where the two regions have generally circular shape. In other embodiments such regions may have other shapes, such as a rectangular shape. The area defined by the inner most line outside of cathode current collector region 132 and anode current collector region 134 defines the active device region, while various other lines represent the overlap/edges of various components/layers of the thin film encapsulant. Turning now to FIG. 1C there is shown a thin film battery arrangement 150 made from a two dimensional array of the thin film batteries 130. This array may be formed by patterning a plurality of batteries by performing a plurality of thin film deposition operations to deposit the different components of thin film batteries 130, as well as patterning operations to define individual batteries, as well as components within the individual batteries.
As further shown in FIG. 1A, and detailed in the figures to follow, in various embodiments, the structure of a TFE stack may include a plurality of layers wherein a polymer layer and a rigid dielectric layer extend in a non-planar fashion. For example, a first portion 121 may extend along the surface of the anode current collector 116 and a second portion 123 may extend along the side of the device stack 110. In this manner, material diffusing from the outside of thin film battery 130 is presented with multiple different layers to diffuse through before contacting the device stack 110, whether penetrating from the top of the thin film battery 130 or from the side of the thin film battery 130. While drawn as individual layer, the thin film encapsulant layers, such as a polymer layer, may comprise a multiple layer configuration of comparable materials, or differing materials, such as different types of polymer sub-layers within a polymer “layer” configured as a multilayer polymer stack.
As further shown in FIG. 1A, the substrate 102 may act as a base for forming the thin film battery 130. The configuration of thin film battery 130 of FIG. 1A may be deemed to be a co-planar configuration, where the substrate 102, is disposed adjacent the cathode current collector 106 in a first region, adjacent the anode current collector pad 108 in a second region, and adjacent the solid state electrolyte 114 in a third region. In other words, the cathode current collector 106 is disposed in a coplanar configuration with the anode stack 109, where the anode stack 109 includes the anode current collector pad 108 and a portion of the anode current collector 116 in electrical contact with the anode current collector pad 108.
In sum, the thin film battery 130 provides multiple ways of encapsulating components of a device stack. In addition to the encapsulation provided by solid state electrolyte 114, the thin film encapsulant 120 encapsulates a first side of the device stack 110, while the anode current collector 116 encapsulates the device stack 110 along a second side.
FIGS. 2A-2K illustrate a cross-sectional view of a thin film battery at various stages of assembly. Turning to FIG. 2A, there is shown an instance where a contact layer 104 and cathode layer 112A have been deposited in blanket form on the substrate 102. According to various embodiments, the contact layer 104 and cathode layer 112A may be deposited using known deposition techniques, including using any combination of physical vapor deposition, chemical vapor deposition, liquid deposition techniques. The layer thickness of these layers may be consistent with thicknesses for known thin film batteries. The contact layer 104 in particular may constitute a material used for known cathode current collectors in known batteries, such as Ti/Pt or other metal material.
At FIG. 2B, there is shown a subsequent instance where the contact layer 104 and cathode layer 112A have been patterned. In particular, the substrate 102 is exposed in a region 204, the contact layer 104 forms the cathode current collector 106 and the anode current collector pad 108 as described above, and the cathode layer 112A forms the cathode 112. In some embodiments, the contact layer 104 and cathode layer 112A may be patterned in separate operations. For example, the cathode layer 112A may first be patterned to remove material of the cathode layer 112A, leaving just the cathode 112 as shown. The patterning may take place using a maskless patterning process such as laser etching, or a masked process where a mask may be deposited and defined in a lithographic process, so as to provide exposed regions of the cathode layer 112A for removal in an etching process, as known in the art.
An advantage of using a maskless patterning process, such as laser etching, is the avoidance of complexity and costs associated with known masked patterning processes involving lithography and dry etching or wet etching. In this manner the complexities of lithography and etching, the consumable costs, and device effects are eliminated. In addition, laser based patterning allows device shape/design to be software recipe based, not depending upon physical masks, facilitating more rapid, flexible and simpler design changes.
In various embodiments, laser patterning may be accomplished primarily in two ways: using diffractive optics employing relatively high power to spread the laser beam over larger areas. This approach may be especially suitable for simple, easily repeated patterns not having fine pattern details. Another type of laser patterning especially useful for patterning thin film batteries according to the present embodiment is direct laser ablation using a rastering approach. Simple and advanced galvanometer based scanners may raster the laser beam to form more complex patterns, and are less limited by feature size and dimensions. To minimize patterning times, high repetition rate lasers (>1 MHz) may be used in combination with polygon mirrors to accomplish high volume production rates.
Pulse durations of picosecond and femtoseconds have been shown to be effective for thin film ablation. The use of radiation wavelengths in the ultraviolet (UV) range, green visible range, as well as infrared range may be effectively employed for patterning via laser ablation the layers of thin film batteries of the present embodiments, including polymer layers, rigid dielectric layers, and rigid metal layers. While thin film encapsulant materials are often transparent or semi-transparent, usable wavelengths may be more appropriate in the UV or green visible range. Most of the aforementioned short pulse lasers are DPSS (Diode pumped solid state) while some fiber based lasers are also contemplated for use in embodiments of the disclosure.
After patterning to form the cathode 112, a surface 208 of the contact layer 104 is exposed on the cathode current collector 106 as well as on the anode current collector pad 108. Subsequently, the contact layer 104 may be etched in a masked or maskless operation to define the region 204 where the surface 206 of substrate 102 is exposed.
Turning now to FIG. 2C, there is shown an instance after the depositing of a solid state electrolyte layer 114A on the cathode 112. The solid state electrolyte layer 114A may be formed as a blanket layer as shown, where the surface 206 of substrate 102 as well as the cathode current collector 106 and the anode current collector pad 108 are covered. Turning now to FIG. 2D there is shown a subsequent instance after patterning of the solid state electrolyte layer 114A to form the partially patterned solid state electrolyte layer 114B, and to expose the anode current collector pad 108 in the region 210 for forming an electrical contact during later processing. In different embodiments, the patterning of the solid state electrolyte layer 114A may be performed by any know patterning technique including maskless patterning or masked patterning as discussed above. At this stage of processing, the partially patterned solid state electrolyte layer 114B may encapsulate the entirety of cathode 112.
Turning now to FIG. 2E there is shown an instance where a blanket layer shown as anode current collector layer 116A has been deposited on the substrate configuration of FIG. 2D. As shown, the anode current collector layer 116A is formed on the partially patterned solid state electrolyte layer 114B and the anode current collector pad 108. The anode current collector layer 116A may be formed of a known metal or combination of metals, such as copper. In some embodiments, an additional anode or anode current collector layers may be deposited before and after the formation of the anode current collector layer 116A.
Turning now to FIG. 2F, there is shown a subsequent instance after patterning of the anode current collector layer 116A and additional patterning of the partially patterned solid state electrolyte layer 114B, wherein the cathode current collector 106 is exposed in a first region, shown as region 212. At this stage of processing the solid state electrolyte 114 and the anode current collector may be in final form for the battery to be fabricated. The solid state electrolyte 114 continues to encapsulate the cathode 112 as shown. In some embodiments, the anode current collector layer 116A and partially patterned solid state electrolyte layer 114B may be patterned in separate operations. For example, the anode current collector layer 116A may first be patterned to remove material of the anode current collector layer 116A, leaving just the anode current collector 116 as shown. The patterning may take place using a maskless patterning process such as laser etching, or a masked process where a mask may be deposited and defined in a lithographic process, so as to provide exposed regions of the anode current collector layer 116A for removal in an etching process, as known in the art. After patterning to form the anode current collector 116, the partially patterned solid state electrolyte layer 114B may be etched in a masked or maskless operation to define the region 212 where the surface 208 of cathode current collector 106 is exposed.
Turning now to FIG. 2G there is shown an instance after depositing a polymer layer or a stack of polymer layers, shown as the polymer layer 220A, on the substrate 102. More particularly, the polymer layer 220A is disposed on the anode current collector 116, on the cathode current collector 106 and along a side of the solid state electrolyte 114. The polymer layer 220A may be deposited as a blanket layer by known processes. In various embodiments, the polymer layer 220A may be a soft and pliable polymer layer or multiple layer stack where at least one layer is a soft and pliable polymer layer. The polymer layer 220A may be configured to accommodate volume changes during operation of a battery to be formed, particularly in regions of the device stack 110 (as shown in FIG. 1A). Turning now to FIG. 211 there is shown a subsequent instance after patterning the polymer layer 220A (shown in FIG. 2G) to form a patterned polymer layer 220, wherein the cathode current collector 106 is exposed in a first region 214 and the anode current collector 116 is exposed in a second region 216.
In various embodiments the polymer layer 220A may form a first part of a thin film encapsulant to be formed. Depending upon various considerations including the total thickness of the battery to be formed, the degree of protection, and robustness of the battery, a number of additional layers of a thin film encapsulant may be added. Turning now to FIG. 2I and FIG. 2J, there are shown subsequent operations where a patterned dyad process is performed after the formation of the patterned initial polymer layer as exemplified by FIG. 2H. A patterned dyad process may involve depositing a blanket dyad composed of a rigid dielectric layer and a polymer layer, followed by patterning the blanket dyad to form a patterned thin film encapsulant including a plurality of layers.
Turning in particular to FIG. 21, there is shown a subsequent instance after the depositing of a rigid dielectric layer 222A on the patterned polymer layer 220 and after the further depositing a second polymer layer 224A on the rigid dielectric layer 222A. Again, the rigid dielectric layer 222A and second polymer layer 224A may be deposited using known blanket deposition processes. The rigid dielectric layer 222A may in particular, provide resistance against diffusion of unwanted species into active regions of the thin film battery to be fabricated, where the active regions may include the cathode, solid state electrolyte, and anode, for example.
Turning now to FIG. 2J, there is shown a subsequent instance after the patterning the rigid dielectric layer 222A and the second polymer layer 224A. At this instance, the patterned rigid dielectric layer 222 and the patterned second polymer layer 224 are formed, where the cathode current collector 106 is exposed in a first inner region 218, and the surface 217 of the anode current collector 116 is exposed in a second inner region 219. As illustrated by comparison to FIG. 2H, the first inner region 218 is disposed within the first region 214, and the second inner region 219 is disposed in the second region 216.
According to various embodiments of the disclosure, a thin film encapsulant may be completed by forming a top layer composed of a rigid dielectric layer. In some embodiments, the patterned dyad process as depicted in the operations of FIG. 2I and FIG. 2J may be repeated at least one time to generate a thicker thin film encapsulant, before forming a final layer composed of a rigid dielectric layer. Turning now to FIG. 2K, there is shown a subsequent instance after performing a second patterned dyad process, forming the layer 226 and the layer 228, and after the depositing and patterning of an additional rigid dielectric layer, shown as the layer 230. The final structure of the thin film encapsulant thus formed includes three dyads, where a given dyad includes a polymer layer and rigid dielectric layer. After the formation of the thin film encapsulant, a cathode contact 122 and an anode contact 124 may be formed as shown.
FIG. 3 illustrates a cross-section of an arrangement 300 including another type of thin film battery 330, according to further embodiments of the disclosure. As shown, the thin film battery 330 may be formed using a substrate 102, formed of any material as disclosed previously with respect to FIG. 1A. In some embodiments the anode current collector pad 108, cathode current collector 106, cathode 112, and solid state electrolyte 114 may be configured as in the thin film battery 130. Notably, in the thin film battery 330 a thin film encapsulant 304 is provided, where the thin film encapsulant 304 may include fewer layers as opposed to the thin film battery 130. For example, the thin film encapsulant 304 may include just one layer, such as a polymer layer. Another hallmark of the thin film battery 330 is the provision of a thicker anode current collector, shown as anode current collector 302, where the thickness of the anode current collector 302 may be 1 μm to 10 μm, and in some examples greater than 10 μm. An advantage provided by the thin film battery 330 is a relatively simpler process for forming the thin film encapsulant 304, as well as a relatively shallower topography, along the Z-axis. In particular, in addition to the protection of the cathode 112 provided by the solid state electrolyte 114, the thicker anode current collector may provide additional encapsulation, while allowing a much thinner thin film encapsulant to be used to provide adequate encapsulation for the thin film battery 330.
While in some embodiments a thin film encapsulant such as thin film encapsulant 120 may include a plurality of layers, the embodiments are not limited in this context. In other embodiments, a thin film encapsulant of a thin film battery may be formed of a unitary layer, meaning the thin film encapsulant is composed of just one layer. In such embodiments, and as described below with respect to FIGS. 4A-4D, an improved anode current collector may be provided in the thin film battery to provide adequate encapsulation when used in conjunction with a thin film encapsulant formed of just one layer. For example in embodiments where a thin film encapsulant is formed of just one layer, the anode current collector comprises a layer thickness of at least five micrometers. FIGS. 4A-4D illustrate a cross-sectional view of another thin film battery at various stages of assembly. Turning to FIG. 4A, there is shown an instance where the cathode current collector 106, anode current collector pad 108, cathode 112 and partially patterned solid state electrolyte layer 114B have been formed in accordance with the procedures outlined above with respect to FIGS. 2A-2D. In addition, an anode current collector layer 302A has been deposited in blanket form, covering the solid state electrolyte 114 and anode current collector pad 108. The anode current collector layer 302A may be arranged as an extra thick metal layer having a thickness of at least 1 μm to 10 μm.
Turning now to FIG. 4B, there is shown a subsequent instance after patterning of the anode current collector layer 302A and additional patterning of the partially patterned solid state electrolyte layer 114B, wherein the cathode current collector 106 is exposed in a first region, shown as region 212. At this stage of processing the solid state electrolyte 114 and the anode current collector 302 may be in final form for the battery to be fabricated. The solid state electrolyte 114 continues to encapsulate the cathode 112 as shown. In some embodiments, the anode current collector layer 302A and partially patterned solid state electrolyte layer 114B may be patterned in separate operations. For example, the anode current collector layer 302A may first be patterned to remove material of the anode current collector layer 302A, leaving just the anode current collector 302 as shown. The patterning may take place using a maskless patterning process such as laser etching, or a masked process where a mask may be deposited and defined in a lithographic process, so as to provide exposed regions of the anode current collector layer 302A for removal in an etching process, as known in the art. After patterning to form the anode current collector 302, the partially patterned solid state electrolyte layer 114B may be etched in a masked or maskless operation to define the region 212 where the surface 208 of cathode current collector 106 is exposed.
Turning now to FIG. 4C there is shown an instance after depositing a polymer layer 304A on the substrate 102, or more particularly on the anode current collector 302, on the cathode current collector 106 and along a side of the solid state electrolyte 114. The polymer layer 304A may be deposited as a blanket layer by known processes. In various embodiments, the polymer layer 304A may be a soft and pliable polymer layer or multiple layer stack of at least two polymer sub-layers. The polymer layer 304A may be configured to accommodate volume changes during operation of a battery to be formed, particularly in regions of the device stack 110 (as shown in FIG. 1A).
Turning now to FIG. 4D there is shown a subsequent instance after patterning the polymer layer 304A to form a patterned polymer layer, shown as the thin film encapsulant 304. At the instance of FIG. 4d the cathode current collector 106 is exposed in a first region 402 and the anode current collector 302 is exposed in a second region 404. Subsequently, electrical contacts may be formed to the first region 402 and the second region 404, to complete the thin film battery 330. As shown in FIG. 4E, the cathode current collector 106 may include a thin interconnect strip. Notably, after the process shown in FIG. 4D, a capping layer such as a rigid dielectric or rigid metal layer may be formed on the polymer layer 304A to provide a permeation blocking layer, to provide diffusion resistance to moisture, gas species or other species.
FIG. 5 illustrates a cross-section of a thin film battery 500 according to various additional embodiments of the disclosure. The thin film battery 500 may be formed generally as described above with the same front end configuration up to FIG. 2G, where the cathode, solid state electrolyte, and anode regions are formed as previously described. Additionally, the layer 220, forming a first layer of a thin film encapsulant, may be formed as detailed above. Notably, the thin film battery 500 includes a different thin film encapsulant, shown as thin film encapsulant 502. In this embodiment, the thin film encapsulant 502 includes at least one rigid metal layer, shown as layer 530, and at least one dielectric layer in addition to the patterned polymer layer 220 (polymer) layer. The layer 530 represents a patterned rigid metal layer, after the thin film encapsulant 502 has been completed.
As shown, the thin film battery 500 has a first region 510 where the cathode current collector 106 may be contacted, as well as a second region 520 where the anode current collector 116 may be contacted. After formation of the thin film encapsulant 502, the cathode current collector 106 is exposed in a first inner region 512, the anode current collector 116 is exposed in a second inner region 522. Notably the first inner region 512 is disposed within the first region 510, and the second inner region 522 is disposed in the second region 520.
In the thin film battery 500, the thin film encapsulant 502 may include at least one dyad, where the at least one dyad is generally disposed on the rigid metal layer, and arranged wherein a first rigid dielectric layer of the at least one dyad is disposed in contact with the rigid metal layer. Advantages of this configuration include the improved permeation blocking provided by a rigid metal layer, i.e., the increased resistance to diffusion of species such as moisture or gas. In particular, by providing a rigid metal layer adjacent polymer layer 202, instead of a rigid dielectric layer, volume changes in the thin film battery 500 may more easily be accommodated in the thin film encapsulant 502. In particular, when the thin film encapsulant 502 is subjected to flexing or other mechanical force, caused by changes in volume in the anode region (see anode region 115), a rigid metal layer may deform (elastically or plastically) more readily than a rigid dielectric. This deformation may allow a rigid metal layer within the thin film encapsulant 502 to remain intact even while a rigid dielectric layer may crack, thus preserving diffusion barrier properties. This ability to remain intact may be especially useful in configurations where an underlying polymer layer, such as the layer 220, is not able to accommodate the entirety of deformations taking place in the anode region.
FIGS. 6A-6D illustrate a cross-sectional view of a thin film battery at various stages of assembly. Continuing from a processing stage shown generally at FIG. 2G, in FIG. 6A there is shown the result of an additional operation where a portion of the polymer layer 220A is removed to form a contact region 602 above the cathode current collector 106. This patterning results in the formation of the layer 220B where the opening to form the contact region 602 may be formed by laser patterning.
Turning to FIG. 6B, in a subsequent operation, a rigid metal layer 604 may be deposited by blanket deposition. The thickness of the rigid metal layer 604 may range from 1 μm to 5 μm in various embodiments. Examples of metals appropriate for use as rigid metal layer 604 include Al, Cu, Ti, Pt, Au, etc. Turning now to FIG. 6C, there is shown a subsequent operation where a portion of the rigid metal layer 604 and the layer 220B are etched in the contact region 606, so as to provide for contacting the anode current collector 116. As shown, the patterned polymer layer 220 is now formed. Turning now to FIG. 6D there is shown a subsequent operation where a dyad 608 is deposited on the structure of FIG. 6C. The dyad 608 may be made of a polymer layer and a rigid dielectric layer in some embodiments. While just one dyad is shown in FIG. 6D, in some embodiments a plurality of dyads 608 may be formed. After a targeted number of dyads is formed, resulting in the thin film encapsulant 610, etching of the thin film encapsulant 610 may be performed to form openings for contacting the cathode current collector 106 and anode current collector 116, generally as shown, for example in FIG. 5. To arrive at the thin film encapsulant 502 shown in FIG. 5, for example, two dyads may be deposited over the rigid metal layer 604, where a given dyad is composed of a rigid dielectric layer followed by a polymer layer. On top of the two dyads, layer 220B and rigid metal layer 604, a last layer formed from a rigid dielectric may be deposited.
In the above process sequence, a rigid metal layer, such as copper may be incorporated into a thin film encapsulant, while electrically isolating the rigid metal layer from the anode current collector 116.
FIG. 7 illustrates an exemplary process flow 700. At block 702, a contact layer is deposited on a substrate. In various embodiments, the contact layer may be formed from a known metal or metal alloy used in known thin film batteries. At block 704, a cathode layer is deposited on the contact layer. The cathode layer may be formed of a material such as LiCoO₂in some embodiments. At block 706 the contact layer and cathode layer are patterned, wherein the substrate is exposed. The patterning of the contact layer and cathode layer may be performed together or the contact layer may be patterned separately from patterning of the cathode layer. As a result of the patterning the contact layer may form a cathode current collector and anode current collector. The cathode layer may also form a cathode as a result of the patterning.
At block 708 a solid state electrolyte layer is deposited on the substrate after the patterning of the contact layer and the cathode layer. At block 710, the solid state electrolyte layer is patterned wherein the anode current collector pad is exposed.
At block 712, an anode current collector layer is deposited on the solid state electrolyte layer. At block 714 the anode current collector layer and solid state electrolyte layer are patterned, wherein the cathode current collector is exposed. At block 716, a thin film encapsulant is formed on the substrate after the patterning of the anode current collector layer and the solid state electrolyte layer. In some embodiments the thin film encapsulant may include a plurality of layers, such as at least one polymer layer and at least one rigid layer. In other embodiments the thin film encapsulant may be just one layer.
There are multiple advantages provided by the present embodiments, including the advantage of the provision of multiple encapsulation features to protect active regions of a thin film battery. Another advantage is the ability to reduce the topography of a thin film battery by providing encapsulation features formed within active portions of the thin film battery such as in the thin film electrolyte.
The present disclosure is not to be limited in scope by the specific embodiments described herein. Indeed, other various embodiments of and modifications to the present disclosure, in addition to those described herein, will be apparent to those of ordinary skill in the art from the foregoing description and accompanying drawings. Thus, such other embodiments and modifications are in the tended to fall within the scope of the present disclosure. Furthermore, the present disclosure has been described herein in the context of a particular implementation in a particular environment for a particular purpose, while those of ordinary skill in the art will recognize the usefulness is not limited thereto and the present disclosure may be beneficially implemented in any number of environments for any number of purposes. Thus, the claims set forth below are to be construed in view of the full breadth and spirit of the present disclosure as described herein.

Claims

What is claimed is:

1. A thin film battery, comprising:

a contact layer, the contact layer disposed in a first plane and comprising a cathode current collector and an anode current collector pad;

a device stack disposed on the cathode current collector, the device stack comprising a cathode and solid state electrolyte;

an anode current collector disposed on the device stack; and

a thin film encapsulant, the thin film encapsulant disposed over the device stack, wherein the solid state electrolyte encapsulates the cathode.

2. The thin film battery of claim 1, wherein the thin film encapsulant comprises at least one dyad, wherein a dyad of the at least one dyad comprises:

a polymer layer; and

a rigid dielectric layer disposed adjacent the polymer layer, wherein the polymer layer and the rigid dielectric layer extend in a non-planar fashion along a surface of the anode current collector and along a side of the device stack.

3. The thin film battery of claim 2 wherein the polymer layer comprises a soft and pliable polymer

4. The thin film battery of claim 3, wherein the anode current collector comprises a layer thickness of 1 μm to 10 μm.

5. The thin film battery of claim 1, wherein the cathode comprises a lithium containing material.

6. The thin film battery of claim 1 further comprising a substrate, the substrate disposed adjacent the cathode current collector in a first region and adjacent the anode current collector pad in a second region and adjacent the solid state electrolyte in a third region.

7. The thin film battery of claim 1, wherein an exposed region of the cathode current collector comprises a thin interconnect strip.

8. The thin film battery of claim 1, wherein the device stack further comprises an anode region, disposed between the solid state electrolyte and anode current collector.

9. The thin film battery of claim 1, wherein the thin film encapsulant encapsulates a first side of the device stack, wherein the anode current collector encapsulates the device stack along a second side; and wherein the anode current collector is in electrical contact with the anode current collector pad.

10. The thin film battery of claim 2, wherein the thin film encapsulant comprises:

a first polymer layer, the first polymer layer disposed on the anode current collector;

a rigid metal layer disposed on the first polymer layer; and

the at least one dyad, the at least one dyad disposed on the rigid metal layer, and arranged wherein a first rigid dielectric layer of the at least one dyad is disposed in contact with the rigid metal layer, and wherein a second polymer layer of the at least one dyad is disposed over the first rigid dielectric layer.

11. A method of forming a thin film battery, comprising:

depositing a contact layer on a substrate;

forming a device stack over the contact layer, the device stack comprising a cathode, a solid state electrolyte and an anode current collector, wherein the solid state electrolyte encapsulates the cathode; and

forming a thin film encapsulant on the substrate after the forming the device stack.

12. The method of claim 11, wherein the forming the device stack comprises:

depositing a cathode layer on the contact layer;

patterning the contact layer and the cathode layer, wherein the substrate is exposed, and wherein the contact layer forms a cathode current collector and an anode current collector pad, and the cathode layer forms the cathode;

depositing a solid state electrolyte layer on the cathode;

patterning the solid state electrolyte layer to expose the anode current collector pad;

depositing an anode current collector layer on the substrate; and

patterning the anode current collector layer and the solid state electrolyte layer, wherein the cathode current collector is exposed in a first region, wherein the patterning the contact layer and the cathode, the solid state electrolyte, and the anode current collector, comprise laser etching select portions of the contact layer and the cathode, the solid state electrolyte, and the anode current collector.

13. The method of claim 12, wherein the forming the thin film encapsulant comprises:

depositing a polymer layer on the substrate; and

and patterning the polymer layer to form a patterned polymer layer, wherein the cathode current collector is exposed in a first region and the anode current collector is exposed in a second region.

14. The method of claim 13, further comprising:

depositing a rigid dielectric layer on the patterned polymer layer; and

depositing a second polymer layer on the rigid dielectric layer; and

patterning the rigid dielectric layer and the second polymer layer, wherein the cathode current collector is exposed in a first inner region, wherein the anode current collector is exposed in a second inner region, the first inner region being disposed within the first region, and the second inner region being disposed in the second region.

15. The method of claim 14, further comprising after the patterning the rigid dielectric layer and the second polymer layer:

depositing an additional rigid dielectric layer on the second polymer layer; and

patterning the additional rigid dielectric layer, wherein the cathode is exposed in a third inner region, the third inner region being disposed within the first region, and wherein the anode current collector is exposed in a fourth inner region, the fourth inner region being disposed in the second region, wherein the patterning the polymer layer, the rigid dielectric layer, the second polymer layer, and the additional rigid dielectric layer comprise laser etching select portions of the polymer layer, the rigid dielectric layer, the second polymer layer, and the additional rigid dielectric layer.

16. The method of claim 11, wherein the anode current collector comprises a layer thickness of 1 μm to 10 μm.

17. The method of claim 12, wherein the first region of the cathode current collector comprises a thin interconnect strip.

18. The method of claim 12, wherein the patterning the contact layer and the cathode layer comprises patterning the cathode layer in a first operation and patterning the contact layer in a second operation, subsequent to the first operation.

19. A method of forming a thin film battery, comprising:

depositing a contact layer on a substrate and depositing a cathode layer on the contact layer;

patterning the contact layer and the cathode layer, wherein the substrate is exposed, and wherein the contact layer forms a cathode current collector and an anode current collector pad, and the cathode layer forms a cathode;

depositing a solid state electrolyte layer on the substrate after the patterning the contact layer and the cathode layer;

patterning the solid state electrolyte layer, wherein the anode current collector pad is exposed;

depositing an anode current collector layer on the substrate after the patterning the solid state electrolyte layer;

patterning the anode current collector layer and the solid state electrolyte layer, wherein the cathode current collector is exposed;

depositing a polymer layer on the substrate after the patterning the anode current collector layer and the solid state electrolyte layer;

and patterning the polymer layer to form a patterned polymer layer, wherein the cathode current collector is exposed in a first region.

20. The method of claim 19, further comprising:

depositing a rigid metal layer on the patterned polymer layer;

patterning the rigid metal layer to and the patterned polymer layer, wherein a patterned rigid metal layer is formed, and wherein the anode current collector layer is exposed in a second region;

depositing at least one dyad on the patterned rigid metal layer, wherein the at least one dyad comprises a rigid dielectric layer and a second polymer layer disposed on the rigid dielectric layer; and

patterning the at least one dyad, wherein the cathode current collector is exposed in a first inner region, wherein the anode current collector is exposed in a second inner region, the first inner region being disposed within the first region, and the second inner region being disposed in the second region.