WO2023037699A1 - Pressure sensor - Google Patents

Abstract

Provided is a pressure sensor having high electrostatic resistance. This pressure sensor comprises a substrate and a covering member. The substrate has a diaphragm, and a support part that surrounds the diaphragm as seen from the thickness direction of the diaphragm. The covering member covers one surface of the diaphragm such that a measurement space is formed between the covering member and the diaphragm, the covering member being joined to the support part of the substrate. The diaphragm flexes due to pressure applied to the one surface of the diaphragm. A communication orifice that allows the measurement space and the exterior to communicate with one another is formed in the covering member. The covering member is grounded.

Description

pressure sensor

The present invention relates to a pressure sensor formed using MEMS (Micro Electro Mechanical Systems) technology.

Conventionally, for example, the one described in Patent Document 1 is known as this type of pressure sensor. The pressure sensor described in Patent Document 1 includes a sensor portion having a diaphragm, and a rigid cover disposed over the sensor portion and forming a cavity between the sensor portion and the diaphragm. The sensor portion has electronic circuitry for calculating the pressure applied to the diaphragm based on a signal corresponding to the amount of strain in the diaphragm.

JP 2010-203857 A

However, in the pressure sensor described in Patent Literature 1, when a current caused by static electricity or the like flows through the rigid cover, the current flows into the electronic circuit provided in the sensor section, causing detection failure of the pressure sensor. There is a risk.

Accordingly, an object of the present invention is to solve the above problems and to provide a pressure sensor with high resistance to static electricity.

In order to achieve the above object, the pressure sensor according to the present invention comprises:
a diaphragm and a base material having a support portion surrounding the diaphragm when viewed from the thickness direction of the diaphragm;
a covering member that covers one surface of the diaphragm so as to form a measurement space between itself and the diaphragm, and that is joined to a supporting portion of the base material;
with
the diaphragm flexes due to pressure applied to one side of the diaphragm;
A communication hole is formed in the covering member to communicate the measurement space with the outside,
the covering member is grounded;
is configured as

According to the present invention, a pressure sensor with high resistance to static electricity can be realized.

1 is a plan view of a pressure sensor according to a first embodiment of the invention; FIG. FIG. 2 is a cross-sectional view taken along line II-II of the pressure sensor in FIG. 1; FIG. 2 is a cross-sectional view taken along line III-III of the pressure sensor of FIG. 1; FIG. 3 is an enlarged view of a region Z1 in FIG. 2; FIG. 3 is a cross-sectional view showing an example of a mounted state of the pressure sensor of FIG. 2; FIG. 2 is a cross-sectional view of a pressure sensor according to a second embodiment of the invention, corresponding to line II-II in FIG. 1; FIG. 3 is an enlarged view corresponding to a region Z1 of a modification of the pressure sensor of FIG. 2; FIG. 3 is an enlarged view corresponding to a region Z1 of a modification of the pressure sensor of FIG. 2; FIG. 3 is an enlarged view corresponding to a region Z1 of a modification of the pressure sensor of FIG. 2; FIG. 7 is a cross-sectional view showing an example of a method of forming a covering member in the pressure sensor of FIG. 6; FIG. 11 is a cross-sectional view showing a step following FIG. 10; FIG. 12 is a cross-sectional view showing a step following FIG. 11; FIG. 13 is a cross-sectional view showing a step following FIG. 12; FIG. 14 is a cross-sectional view showing a step following FIG. 13; FIG. 15 is a cross-sectional view showing a step following FIG. 14; FIG. 2 is a plan view showing a modification of the pressure sensor of FIG. 1;

A pressure sensor according to an aspect of the present invention comprises
a diaphragm and a base material having a support portion surrounding the diaphragm when viewed from the thickness direction of the diaphragm;
a covering member that covers one surface of the diaphragm so as to form a measurement space between itself and the diaphragm, and that is joined to a supporting portion of the base material;
with
the diaphragm flexes due to pressure applied to one side of the diaphragm;
A communication hole is formed in the covering member to communicate the measurement space with the outside,
The covering member is grounded.

According to this configuration, the covering member is grounded. As a result, when the base material has an electronic circuit for calculating the pressure applied to one side of the diaphragm, it is possible to suppress current caused by static electricity or the like from flowing into the electronic circuit. Therefore, a pressure sensor with high resistance to static electricity can be realized.

The base material may have a first layer and a second layer having the diaphragm and the support. The second layer may be laminated to the first layer so as to form a reference space between the first layer and the opposite side of the diaphragm. The first layer may have a ground portion that is grounded. The covering member may be electrically connected to the ground portion of the first layer.

According to this configuration, since the covering member is electrically connected to the ground portion of the first layer, a grounded covering member can be realized. Therefore, a pressure sensor with high resistance to static electricity can be realized.

The covering member may have a facing surface that forms the measurement space and faces the diaphragm. The covering member may have a convex portion projecting toward the diaphragm in an overlapping region of the facing surface that overlaps with the diaphragm when viewed in the thickness direction of the diaphragm.

When water enters the measurement space, water droplets formed by the water can contact both the facing surface of the covering member and the diaphragm at the same time. When the water droplet is in contact with both the facing surface of the covering member and the diaphragm and becomes smaller due to evaporation, the diaphragm is drawn toward the facing surface of the covering member by the surface tension of the water droplet. When the water droplet becomes smaller, the diaphragm contacts the opposing surface of the covering member. In this case, the diaphragm may adhere to the facing surface of the covering member after the water droplets have disappeared. A sticking diaphragm causes the pressure sensor to fail to detect.

On the other hand, according to this configuration, the covering member has a convex portion in the overlapping region of the facing surfaces. Therefore, when the diaphragm is drawn toward the facing surface of the covering member, the diaphragm contacts the convex portion before the facing surface of the covering member and is no longer drawn. That is, the contact area between the diaphragm and the covering member is smaller than in a configuration in which the covering member does not have a convex portion. This prevents the diaphragm from sticking to the covering member. Therefore, it is possible to reduce the possibility of detection failure of the pressure sensor.

The convex portion may be formed around the opening of the communication hole formed in the facing surface of the covering member.

The above-mentioned water droplets tend to accumulate in the measurement space near the opening of the communication hole, which is the infiltration path of water. According to this configuration, the projection is formed around the opening of the communication hole on the facing surface of the covering member. This can prevent the diaphragm from sticking to the covering member. Therefore, it is possible to reduce the possibility of detection failure of the pressure sensor.

The covering member may have a plurality of protrusions. The plurality of protrusions may be formed in a grid pattern over the entire overlapping region of the covering member.

According to this configuration, a plurality of protrusions are formed in the entire overlapping region of the covering member. As a result, it is possible to suppress adhesion of the diaphragm to the covering member in the entire overlapping region of the covering member. Therefore, it is possible to reduce the possibility of detection failure of the pressure sensor.

The convex portion may have a tapered shape in which the width of the convex portion decreases toward the diaphragm when viewed from a direction perpendicular to the thickness direction of the diaphragm.

According to this configuration, since the width of the tip of the protrusion is narrow, the contact area between the protrusion and the diaphragm is small. Therefore, sticking of the diaphragm to the protrusion is suppressed compared to a configuration that does not have a tapered shape in which the width of the protrusion decreases toward the diaphragm. Therefore, it is possible to reduce the possibility of detection failure of the pressure sensor.

The tip of the convex portion may be a curved surface.

When viewed from the direction perpendicular to the thickness direction of the diaphragm, if the protrusion tapers toward the diaphragm and has a sharp tip, stress is applied to the tip of the protrusion when the protrusion and the diaphragm come into contact with each other. may concentrate. Concentration of stress on the tip of the protrusion increases the possibility of breakage of the protrusion. According to this configuration, since the tip of the protrusion is a curved surface, it is possible to suppress concentration of stress on the tip of the protrusion. Therefore, it is possible to realize a protrusion that is less likely to be damaged by contact with the diaphragm.

The covering member may have a facing surface that forms the measurement space and faces the diaphragm. The opening of the communicating hole formed in the facing surface may not overlap the diaphragm when viewed from the thickness direction of the diaphragm.

According to this configuration, the opening of the communicating hole formed in the facing surface of the covering member does not overlap with the diaphragm when viewed from the thickness direction of the diaphragm. Therefore, it is possible to reduce the possibility that foreign matter that has passed through the communication hole together with the fluid will reach one side of the diaphragm. Therefore, detection failure of the pressure sensor due to adhesion of foreign matter to the diaphragm can be suppressed.

The covering member may have a facing surface that forms the measurement space and faces the diaphragm, and an upper surface that is opposite to the facing surface. The shortest distance between the opening of the communicating hole formed in the top surface and the center of the top surface is shorter than the shortest distance between the opening of the communicating hole formed in the top surface and the edge of the top surface. may

For example, after the pressure sensor is mounted on the base substrate, it is sealed with resin except for a part of the upper surface of the covering member. According to this configuration, the shortest distance between the opening of the communicating hole formed in the upper surface of the covering member and the center of the upper surface is the shortest distance between the opening of the communicating hole formed in the upper surface and the edge of the upper surface. shorter than distance. That is, on the upper surface of the covering member, the opening of the communication hole is separated from the edge of the upper surface. As a result, when the uncured resin flows from the edge of the upper surface of the covering member toward the center of the upper surface, it is possible to reduce the possibility that the resin will block the communication holes or adhere to the diaphragm. . Therefore, detection failure of the pressure sensor can be suppressed.

The covering member may be thicker than the base material in the thickness direction of the diaphragm.

For example, when the pressure sensor is mounted on a housing, stress may deform it so that the covering member side becomes convex along the thickness direction of the diaphragm. The magnitude of this deformation increases as the upper surface of the covering member is approached in the thickness direction of the diaphragm. According to this configuration, the covering member is thicker than the base material in the thickness direction of the diaphragm. Therefore, the distance between the upper surface of the covering member and the diaphragm can be increased compared to a configuration in which the covering member is thinner than the base material. As a result, the stress acting on the diaphragm can be relaxed when the pressure sensor is deformed into a convex shape, so that the deflection of the diaphragm can be reduced. Therefore, it is possible to suppress characteristic fluctuations of the pressure sensor caused by stress.

The covering member may be thinner than the base material in the thickness direction of the diaphragm.

In the pressure sensor, stress is generated by the shrinkage of the resin as it hardens. The stress is smaller in the portion between the central portion of the pressure sensor and the top surface of the covering member than in the portion between the central portion of the pressure sensor and the bottom surface of the base member in the thickness direction of the diaphragm. According to this configuration, the covering member is thinner than the base material in the thickness direction of the diaphragm. Therefore, the diaphragm is arranged in the portion between the central portion of the pressure sensor and the upper surface of the covering member in the thickness direction. As a result, the stress applied to the diaphragm due to shrinkage of the resin can be reduced, so that the deflection of the diaphragm can be reduced. Therefore, the characteristic fluctuation of the pressure sensor caused by the stress can be suppressed.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that these embodiments do not limit the present invention. Also, in the drawings, substantially the same members are denoted by the same reference numerals, and descriptions thereof are omitted.

Hereinafter, for convenience of explanation, terms indicating directions such as “upper layer”, “lower layer”, “upper surface”, and “lower surface” are used, but these terms limit the usage conditions of the pressure sensor according to the present invention. not a thing

<First Embodiment>
A pressure sensor according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 4. FIG. 1 is a plan view of a pressure sensor according to a first embodiment of the present invention; FIG. FIG. 2 is a cross-sectional view of the pressure sensor of FIG. 1 taken along line II-II. FIG. 3 is a cross-sectional view of the pressure sensor of FIG. 1 taken along line III-III. FIG. 4 is an enlarged view of area Z1 in FIG. 2 to 4 are cross-sectional views along the thickness direction of the diaphragm 51, which will be described later.

The pressure sensor 1 according to the first embodiment detects the pressure applied to one side of the diaphragm based on the electrostatic capacitance generated between the diaphragm and an electrode remote from the diaphragm. That is, the pressure sensor 1 according to the first embodiment is a capacitive pressure sensor.

As shown in FIG. 2 , the pressure sensor 1 includes a base material 2 and a covering member 7 joined to the base material 2 .

The base material 2 has a multilayer structure. In this embodiment, the base material 2 has a lower layer 3, a middle layer 4, an upper layer 5, and insulating layers 61,62. The middle layer 4 is an example of the "first layer" of the present disclosure. The upper layer 5 is an example of the "second layer" of the present disclosure. The lower layer 3 and the upper layer 5 are made of silicon (Si), for example. The intermediate layer 4 is made of, for example, polysilicon (Poly-Si). The insulating layers 61 and 62 are made of silicon oxide (SiO2), for example.

The lower layer 3 has a bottom surface 3a which is one surface. The bottom surface 3 a of the lower layer 3 constitutes the bottom surface of the substrate 2 . An insulating layer 61 is laminated on the surface of the lower layer 3 opposite to the bottom surface 3a. The intermediate layer 4 is laminated on the surface of the insulating layer 61 opposite to the surface in contact with the lower layer 3 . The middle layer 4 has a ground portion 41 and a fixed electrode portion 43 (see FIG. 3) that generates capacitance between the diaphragm 51 and the ground portion 41 . In this embodiment, as shown in FIG. 3 , the fixed electrode portion 43 is electrically connected to the lower layer 3 through holes 611 formed in the insulating layer 61 .

As shown in FIG. 2 , a ground electrode 42 is superimposed on the ground portion 41 . The ground electrode 42 is made of, for example, aluminum (Al), titanium (Ti), or the like. As shown in FIG. 5, the ground electrode 42 is grounded, for example, by being connected via a wire 14 to a ground electrode (not shown) of the base substrate B on which the pressure sensor 1 is mounted. As a result, the ground portion 41 of the intermediate layer 4 connected to the ground electrode 42 is also grounded.

As shown in FIG. 3, an insulating layer 62 is laminated on the surface of the intermediate layer 4 opposite to the surface in contact with the insulating layer 61 . A hole is formed in the insulating layer 62 in a portion overlapping the fixed electrode portion 43 of the intermediate layer 4 . The hole corresponds to the reference space 10 described later. The upper layer 5 is laminated on the surface of the insulating layer 62 opposite to the surface in contact with the intermediate layer 4 . The upper layer 5 has an upper surface 5 a opposite to the surface that contacts the insulating layer 62 . As shown in FIG. 2 , the ground portion 41 and the ground electrode 42 communicate with the outside of the base material 2 . A ground electrode 42 is spaced from the top layer 5 .

Each layer constituting the base material 2 is airtightly joined. This bonding is, for example, normal temperature bonding, adhesive fixation, or the like. As shown in FIG. 3, the reference space 10 is formed by airtightly closing a hole formed in the insulating layer 62 with layers stacked above and below the insulating layer 62 . In this embodiment, the reference space 10 is in a vacuum state of 10 Pa or less, for example.

The upper layer 5 has a diaphragm 51 that overlaps the reference space 10 and a support portion 52 that surrounds the diaphragm 51 when viewed from above in the stacking direction of the layers of the base material 2 . A region of the upper surface 5 a of the upper layer 5 that corresponds to the diaphragm 51 constitutes an upper surface 51 a of the diaphragm 51 . The upper surface 51a is an example of "one side" of the diaphragm in the present invention. Diaphragm 51 has an upper surface 51a and an opposite lower surface 51b. The lower surface 51b is an example of the "other surface" of the diaphragm in the present invention.

The diaphragm 51 is a portion of the upper layer 5 that bends in response to pressure applied to the upper surface 51a. In other words, the diaphragm 51 is the portion of the upper layer 5 that is not bonded to the insulating layer 62 . A broken line shown in FIG. 3 is a line obtained by extending a boundary line between the diaphragm 51 and the support portion 52 in the upper layer 5 in the stacking direction of each layer of the base material 2 . In this embodiment, the diaphragm 51 and the support portion 52 are integrally formed.

In the example shown in FIG. 1, the upper layer 5 has two diaphragms 51. In this embodiment, each diaphragm 51 is rectangular in plan view, but may be circular, elliptical, polygonal, or the like, for example. Also, the number of diaphragms 51 may be one or three or more. Here, the thickness direction of the diaphragm 51 coincides with the stacking direction of each layer of the base material 2 .

As shown in FIG. 3 , the upper surface 5 a of the upper layer 5 is provided with a covering member 7 that covers the upper surface 51 a of the diaphragm 51 so as to form the measurement space 11 between itself and the diaphragm 51 . The covering member 7 is joined to a region of the upper surface 5 a of the upper layer 5 corresponding to the support portion 52 via the insulating layer 63 . As used herein, "joining" includes both contacting and joining two or more objects and joining two or more objects through another object.

The insulating layer 63 is made of, for example, silicon oxide (SiO2). The covering member 7 is made of silicon (Si), for example. The bonding between the upper layer 5, the insulating layer 63, and the covering member 7 is, for example, normal temperature bonding, adhesive fixation, or the like.

As shown in FIG. 2, the covering member 7 forms the measurement space 11 and has a facing surface 7a facing the upper surface 51a of the diaphragm 51. As shown in FIG. Furthermore, the covering member 7 has an upper surface 7b opposite to the facing surface 7a. The upper surface 7 b of the covering member 7 constitutes the upper surface of the pressure sensor 1 .

In this embodiment, the distance between the upper surface 5a of the upper layer 5 and the facing surface 7a of the covering member 7, that is, the height of the measurement space 11 is 2 μm.

As shown in FIG. 1, the upper surface 7b of the covering member 7 has, for example, a rotationally symmetrical shape in plan view. In this specification, "rotational symmetry" means that when the upper surface 7b of the covering member 7 is rotated around the virtual center point C, the relative position and shape with respect to the virtual center point C match before and after the rotation. means. In this embodiment, the upper surface 7b of the covering member 7 is rectangular in plan view. The virtual center point C is an example of the "center of the upper surface" in the present invention.

As shown in FIG. 2, the covering member 7 is formed with a communication hole 8 that penetrates between the facing surface 7a and the upper surface 7b and communicates the measurement space 11 with the outside of the covering member 7. As shown in FIG. An opening 81 of the communication hole 8 is formed in the facing surface 7a of the covering member 7. As shown in FIG. An opening 82 of the communication hole 8 is formed in the upper surface 7b of the covering member 7. As shown in FIG. The cross section of the communication hole 8 is, for example, circular with a diameter of 20 μm or more. Although one communication hole 8 is formed in this embodiment, two or more communication holes 8 may be formed.

The communication hole 8 extends in the thickness direction of the diaphragm 51 . That is, as shown in FIG. 1, the opening 81 formed in the facing surface 7a of the covering member 7 and the opening 82 formed in the upper surface 7b of the covering member 7 match each other in plan view. In addition, the communication hole 8 is not limited to the shape described above, and may extend in other directions or may be bent. In other words, the openings 81 and 82 do not have to match in plan view.

As shown in FIGS. 1 and 3, the facing surface 7a of the covering member 7 has an overlapping region 7c that overlaps the diaphragm 51 in plan view. A region of the facing surface 7a of the covering member 7 excluding the overlapping region 7c constitutes a non-overlapping region 7d. As shown in FIGS. 1 and 2, in the facing surface 7a of the covering member 7, the openings 81 are formed in the non-overlapping regions 7d. That is, the opening 81 formed in the facing surface 7a of the covering member 7 does not overlap the diaphragm 51 in plan view.

As shown in FIG. 1, the upper surface 7b of the covering member 7 has an edge 7e. The shortest distance between the opening 82 formed in the upper surface 7b of the covering member 7 and the virtual center point C is shorter than the shortest distance between the opening 82 and the edge 7e. For example, when the virtual center point C is outside the opening 82 in plan view, the shortest distance L1 (not shown) between the edge of the opening 82 and the virtual center point C is the edge of the opening 82 and the edge 7e. is shorter than the shortest distance L2 (see FIG. 1) between Note that when the virtual center point C overlaps the opening 82 in plan view, the shortest distance L1 is zero. In the present embodiment, the center point of the opening 82 and the virtual center point C match in plan view. That is, the shortest distance L1 is zero. Therefore, the shortest distance L1 is not shown.

As shown in FIGS. 1 and 2 , a ground electrode 71 electrically connected to the covering member 7 is arranged on the upper surface 7 b of the covering member 7 . In this embodiment, the ground electrode 71 is arranged on the edge 7e of the upper surface 7b of the covering member 7. As shown in FIG. The ground electrode 71 is made of, for example, aluminum (Al), titanium (Ti), or the like.

The ground electrode 71 is connected via a wire 9 to the ground electrode 42 arranged on the base material 2 . Since the ground electrode 42 of the base material 2 is grounded, the ground electrode 71 is also grounded. Thereby, the covering member 7 is grounded. That is, the covering member 7 is connected to the ground potential.

As shown in FIG. 3 , at least one convex portion 72 projecting toward the diaphragm 51 in the thickness direction of the diaphragm 51 is formed in the overlap region 7c of the facing surface 7a of the covering member 7 . In the example shown in FIG. 1, a plurality of protrusions 72 are formed in a grid pattern over the entire overlapping region 7c. In this embodiment, the plurality of protrusions 72 are aligned parallel to each of the short and long sides of the rectangular edge 7e when viewed from the thickness direction of the diaphragm 51 . That is, the plurality of protrusions 72 are aligned in two orthogonal directions. In the present embodiment, the convex portion 72 is also formed on the facing surface 7a of the covering member 7 around the opening 81 of the communication hole 8 (see FIG. 2).

As shown in FIG. 4, the projection 72 has a tapered shape in which the width decreases toward the diaphragm 51 (downward in FIG. 4) when viewed from the direction orthogonal to the thickness direction of the diaphragm 51. A tip portion 73 of the convex portion 72 is a curved surface. In this embodiment, the height of each protrusion 72 with respect to the facing surface 7a of the covering member 7 is 1 μm.

As shown in FIG. 2, the thickness D1 of the covering member 7 is thicker than the thickness D2 of the base material 2. In the example shown in FIG. 2, the thickness D1 of the covering member 7 refers to the thickness from the upper surface 7b of the covering member 7 to the surface of the covering member 7 in contact with the insulating layer 63 . The thickness D2 of the base material 2 refers to the thickness from the upper surface 5a of the upper layer 5 to the bottom surface 3a of the lower layer 3 . The ratio of the thickness D1 of the covering member 7 to the thickness D2 of the base material 2 is preferably 1.4 to 1.6 times. In this embodiment, the thickness D1 of the covering member 7 is 600 μm, and the thickness D2 of the substrate 2 is 400 μm. That is, the ratio of the thickness D1 of the covering member 7 to the thickness D2 of the base material 2 is 1.5 times.

FIG. 5 is a cross-sectional view showing an example of the mounting state of the pressure sensor of FIG. In the example shown in FIG. 5, the pressure sensor 1 is mounted on the base substrate B via the bottom surface 3a of the lower layer 3. As shown in FIG. The pressure sensor 1 is electrically connected to an electronic circuit (not shown) provided on the base substrate B via external electrodes (not shown) arranged on the bottom surface 3a of the lower layer 3, for example. The pressure sensor 1 is sealed with a resin M except for a portion of the upper surface 7b of the covering member 7. As shown in FIG. Specifically, the ground electrode 71 and the wire 9 are sealed while the opening 82 of the communication hole 8 is not sealed. Since the opening 82 of the communication hole 8 is not blocked by the resin M, the fluid can enter and exit the measurement space 11 through the communication hole 8 .

The diaphragm 51 bends according to the pressure applied to the upper surface 51a of the diaphragm 51 by the fluid (for example, gas) entering and exiting the measurement space 11 . When the diaphragm 51 bends, the distance between the diaphragm 51 and the fixed electrode portion 43 (see FIG. 3) of the middle layer 4 changes, increasing or decreasing the capacitance generated therebetween. An electrical signal corresponding to the capacitance is output from the diaphragm 51 and the fixed electrode portion 43 of the intermediate layer 4 and transmitted to the electronic circuit, whereby the pressure applied to the upper surface 51a of the diaphragm 51 is calculated. In this way, the pressure sensor 1 functions as an absolute pressure sensor that detects pressure with reference to vacuum.

When the pressure in the reference space 10 is the atmospheric pressure, the pressure sensor 1 functions as a gauge pressure sensor that indicates the pressure when the atmospheric pressure is 0. Moreover, when the pressure in the reference space 10 is an arbitrary pressure, the pressure sensor 1 functions as a differential pressure sensor that indicates the differential pressure with respect to the arbitrary pressure.

According to the pressure sensor 1 according to the first embodiment, the covering member 7 is grounded. As a result, when the base material 2 has an electronic circuit for calculating the pressure applied to the upper surface 51a of the diaphragm 51, it is possible to suppress the current caused by static electricity or the like from flowing into the electronic circuit. Therefore, the pressure sensor 1 with high resistance to static electricity can be realized.

Further, according to the pressure sensor 1 according to the first embodiment, the covering member 7 is electrically connected to the ground portion 41 of the middle layer 4, so that the covering member 7 can be grounded. Therefore, the pressure sensor 1 with high resistance to static electricity can be realized.

In the case of a capacitive pressure sensor, a reference space 10 is formed between the middle layer 4 and the upper layer 5 . The middle layer 4 faces the diaphragm 51 of the upper layer 5 with the reference space 10 interposed therebetween, and has a fixed electrode portion 43 that generates a capacitance with the diaphragm 51 . When the pressure sensor 1 is provided with the ground portion 41 electrically connected to the covering member 7, the ground portion 41 and the fixed electrode portion 43 can be formed at the same time by arranging the ground portion 41 in the middle layer 4. FIG. Therefore, in the manufacturing process of the pressure sensor 1, an additional process for providing the ground portion 41 is unnecessary. Therefore, the grounded covering member 7 can be realized more easily than the configuration in which the ground portion 41 is arranged in a layer having no conductor among the layers constituting the base material 2 .

When water enters the measurement space 11, water droplets formed by the water can contact both the facing surface 7a of the covering member 7 and the diaphragm 51 at the same time. When the water droplets contact both the facing surface 7a of the covering member 7 and the diaphragm 51 and become smaller due to evaporation, the diaphragm 51 is drawn toward the facing surface 7a of the covering member 7 by the surface tension of the water droplets. When the water droplet becomes even smaller, the diaphragm 51 comes into contact with the facing surface 7a of the covering member 7. As shown in FIG. In this case, the diaphragm 51 may adhere to the facing surface 7a of the covering member 7 after the water droplets have disappeared. Sticking of the diaphragm 51 causes detection failure of the pressure sensor 1 .

On the other hand, according to the pressure sensor 1 according to the first embodiment, the covering member 7 has the convex portion 72 in the overlapping region 7c of the facing surface 7a. Therefore, when the diaphragm 51 is drawn toward the facing surface 7a of the covering member 7, the diaphragm 51 contacts the convex portion 72 before the facing surface 7a of the covering member 7, and is no longer drawn. In other words, the contact area between the diaphragm 51 and the covering member 7 becomes smaller compared to the configuration in which the covering member 7 does not have the convex portion 72 . This prevents the diaphragm 51 from sticking to the covering member 7 . Therefore, the possibility of detection failure of the pressure sensor 1 can be reduced.

The water droplets described above tend to accumulate in the measurement space 11 near the opening 81 of the communication hole 8, which is the water entry path. According to the pressure sensor 1 according to the first embodiment, on the facing surface 7a of the covering member 7, the convex portion 72 is formed on the peripheral portion 7f of the opening 81 of the communication hole 8. As shown in FIG. As a result, sticking of the diaphragm 51 to the covering member 7 can be suppressed. Therefore, the possibility of detection failure of the pressure sensor 1 can be reduced.

According to the pressure sensor 1 according to the first embodiment, a plurality of protrusions 72 are formed in the entire overlapping region 7c of the covering member 7. As a result, adhesion of the diaphragm 51 to the covering member 7 can be suppressed in the entire overlapping region 7 c of the covering member 7 . Therefore, the possibility of detection failure of the pressure sensor 1 can be reduced.

According to the pressure sensor 1 according to the first embodiment, since the tip portion 73 of the projection 72 has a narrow width, the contact area between the projection 72 and the diaphragm 51 is small. Therefore, as compared with a configuration in which the protrusion 72 does not have a tapered shape in which the width of the protrusion 72 decreases toward the diaphragm 51 , sticking of the diaphragm 51 to the protrusion 72 is suppressed. Therefore, the possibility of detection failure of the pressure sensor 1 can be reduced.

When viewed from the direction orthogonal to the thickness direction of the diaphragm 51 , when the convex portion 72 tapers toward the diaphragm 51 and the distal end portion 73 has a sharp shape, when the convex portion 72 and the diaphragm 51 contact each other, the convex portion 72 and the diaphragm 51 contact each other. Stress may concentrate on the tip portion 73 of the portion 72 . When the stress concentrates on the tip portion 73 of the protrusion 72, the possibility of the protrusion 72 being damaged increases.

According to the pressure sensor 1 according to the first embodiment, since the tip portion 73 of the convex portion 72 has a curved surface, concentration of stress on the tip portion 73 of the convex portion 72 can be suppressed. Therefore, it is possible to realize the convex portion 72 that is less likely to be damaged by contact with the diaphragm 51 .

Further, according to the pressure sensor 1 according to the first embodiment, the opening 81 of the communication hole 8 formed in the facing surface 7a of the covering member 7 does not overlap the diaphragm 51 when viewed from the thickness direction of the diaphragm 51 . Therefore, it is possible to reduce the possibility that foreign matter that has passed through the communication hole 8 together with the fluid will reach the upper surface 51 a of the diaphragm 51 . Therefore, detection failure of the pressure sensor 1 due to adhesion of foreign matter to the diaphragm 51 can be suppressed.

Further, according to the pressure sensor 1 according to the first embodiment, the shortest distance between the opening 82 of the communicating hole 8 formed in the upper surface 7b of the covering member 7 and the center C of the upper surface 7b is It is shorter than the shortest distance between the edge 7e of the upper surface 7b. That is, on the upper surface 7b of the covering member 7, the opening 82 of the communication hole 8 is separated from the edge 7e of the upper surface 7b. As a result, when the uncured resin M flows from the edge 7e of the upper surface 7b of the covering member 7 toward the imaginary center point C of the upper surface 7b, the resin M blocks the communication hole 8 or the diaphragm 51. It is possible to reduce the possibility of sticking. Therefore, detection failure of the pressure sensor 1 can be suppressed.

For example, when the pressure sensor 1 is mounted on a housing, stress may deform the diaphragm 51 so that the covering member 7 side becomes convex along the thickness direction. The magnitude of this deformation increases as the upper surface 7 b of the covering member 7 is approached in the thickness direction of the diaphragm 51 .

According to the pressure sensor 1 according to the first embodiment, the covering member 7 is thicker than the base material 2 in the thickness direction of the diaphragm 51 . Therefore, the distance between the upper surface 7 b of the covering member 7 and the diaphragm 51 can be increased compared to the configuration in which the covering member 7 is thinner than the base material 2 . As a result, the stress acting on the diaphragm 51 can be relaxed when the pressure sensor 1 is deformed into a convex shape, so that the deflection of the diaphragm 51 can be reduced. Therefore, the characteristic fluctuation of the pressure sensor 1 caused by stress can be suppressed.

<Second embodiment>
A pressure sensor 1A according to a second embodiment of the present invention will be described with reference to FIG. FIG. 6 is a cross-sectional view of the pressure sensor according to the second embodiment of the invention, corresponding to line II-II in FIG.

The pressure sensor 1A according to the second embodiment differs from the pressure sensor 1 according to the first embodiment in that the thickness D1 of the covering member 7 is thinner than the thickness D2 of the base material 2. The ratio of the thickness D1 of the covering member 7 to the thickness D2 of the base material 2 is preferably 0.1 to 0.3 times. In this embodiment, the thickness D1 of the covering member 7 is 80 μm, and the thickness D2 of the substrate 2 is 400 μm. That is, the ratio of the thickness D1 of the covering member 7 to the thickness D2 of the base material 2 is 0.2 times.

In the pressure sensor 1A, stress is generated by shrinkage of the resin M as it cures. The stress in the thickness direction of the diaphragm 51 is greater in the portion between the central portion of the pressure sensor 1A and the bottom surface 3a of the lower layer 3 than in the portion between the central portion of the pressure sensor 1A and the bottom surface 3a of the lower layer 3 . According to the pressure sensor 1</b>A according to the second embodiment, the covering member 7 is thinner than the base material 2 in the thickness direction of the diaphragm 51 . Therefore, the diaphragm 51 is arranged in the portion between the central portion of the pressure sensor 1A and the upper surface 7b of the covering member 7 in the thickness direction. As a result, the stress applied to the diaphragm 51 due to the contraction of the resin M can be reduced, so that the deflection of the diaphragm 51 can be reduced. Therefore, the characteristic fluctuation of the pressure sensor 1A caused by the stress can be suppressed.

<Modification>
Modifications of the pressure sensor 1 will be described with reference to FIGS. 7 to 9. FIG. 7 to 9 are enlarged views corresponding to the region Z1 of the modified example of the pressure sensor of FIG.

In the pressure sensor 1, each projection 72 may have a shape other than the shape shown in FIG. 4 when viewed from the direction perpendicular to the thickness direction of the diaphragm 51. For example, in the modified example of the pressure sensor 1 shown in FIG. 7, the width of the convex portion 72 decreases toward the tip portion 73 of the convex portion 72 when viewed from the direction orthogonal to the thickness direction of the diaphragm 51. It is a trapezoid. That is, the tip portion 73 of the convex portion 72 is not a curved surface but a flat surface parallel or substantially parallel to the facing surface 7 a of the covering member 7 .

The convex portion 72 shown in FIG. 8 has a rectangular shape with a constant width when viewed from the direction orthogonal to the thickness direction of the diaphragm 51 . That is, the width of the protrusion 72 does not decrease toward the tip 73 of the protrusion 72 .

A plurality of convex portions 72 shown in FIG. 9 are formed in a continuous wave shape when viewed from a direction perpendicular to the thickness direction of the diaphragm 51 .

The sticking of the diaphragm 51 to the covering member 7 can also be suppressed by the protrusions 72 shown in FIGS. Therefore, the possibility of detection failure of the pressure sensor 1 can be reduced.

<Method for Forming Covering Member 7>
Next, an example of a method of forming the covering member 7 in the pressure sensor 1A according to the present invention will be described with reference to FIGS. 10 to 14. FIG. 10 to 14 are cross-sectional views showing an example of a method of forming the covering member in the pressure sensor of FIG. 6. FIG.

In this forming method, an SOI (silicon on insulator) substrate 12 is used. As shown in FIG. 10, the SOI substrate 12 has a Si support layer 121, a SiO2 layer 122 and a surface Si layer 123. As shown in FIG. The SiO2 layer 122 is laminated on one side of the Si support layer 121 . A surface Si layer 123 is laminated on the surface of the SiO2 layer 122 opposite to the surface in contact with the Si support layer 121 . A portion of the surface Si layer 123 constitutes the covering member 7 . 10 to 14, for convenience of explanation, the SOI substrate 12 is shown in the direction opposite to the stacking direction described above, that is, the surface Si layer 123 stacked last is shown at the bottom in each figure.

First, as shown in FIG. 10, the additional SiO2 layer 13 is formed on the surface of the surface Si layer 123 opposite to the surface in contact with the SiO2 layer 122 . A portion of the additional SiO2 layer 13 constitutes the insulating layer 63 .

Next, as shown in FIG. 11, the insulating layer 63 is formed by removing the portion of the additional SiO2 layer 13 that does not constitute the insulating layer 63 . The removal is performed, for example, by etching.

Next, as shown in FIG. 12, the portion of the surface Si layer 123 that does not constitute the covering member 7 is removed. The removal is performed, for example, by etching. As a result, the covering member 7 having the projections 72 is formed.

Next, as shown in FIG. 13, the SOI substrate 12 and the additional SiO2 layer 13 (that is, the insulating layer 63) are placed on the side opposite to the surface that contacts the surface Si layer 123 (that is, the covering member 7) of the additional SiO2 layer 13. is joined to the upper surface 5a of the upper layer 5 of the base material 2 via the surface of . The bonding is, for example, normal temperature bonding, adhesive fixation, or the like.

Next, as shown in FIG. 14, the Si support layer 121 and the SiO2 layer 122 are removed. Finally, the surface Si layer 123 (that is, the covering member 7) is etched, for example, to form the communication holes 8. As shown in FIG.

Finally, as shown in FIG. 15, a ground electrode 71 is patterned on the upper surface 7b of the covering member 7. Then, as shown in FIG.

Although the method of forming the covering member 7 in the pressure sensor 1A has been described above, the covering member 7 in the pressure sensor 1 can be formed by further increasing the thickness of the surface Si layer 123 in this forming method.

It should be noted that the present invention is not limited to the above-described embodiments, and can be implemented in various other aspects. For example, in the description above, the pressure sensors 1 and 1A are capacitive pressure sensors, but the present invention is not limited to this. For example, the pressure sensors 1, 1A may be piezoresistive pressure sensors. In this case, the diaphragm 51 is provided with a plurality of piezoresistive elements forming an electronic circuit. An electric signal corresponding to the deflection of the diaphragm 51 is output from the electronic circuit, and the pressure applied to the upper surface 51a of the diaphragm 51 is calculated based on the electric signal.

Also, in the above description, the ground electrode 71 of the covering member 7 and the ground electrode 42 of the base material 2 are connected by the wire 9, but the present invention is not limited to this. For example, the ground electrode 71 of the covering member 7 and the ground electrode 42 of the base material 2 may be connected by a conductive part other than the wire 9 . The ground electrode 71 of the covering member 7 and the ground electrode 42 of the base material 2 may be indirectly connected as long as they are electrically connected. As long as the covering member 7 and the ground portion 41 of the base material 2 are electrically connected, at least one of the ground electrode 71 and the ground electrode 42 may not be provided. As long as the covering member 7 is grounded, the grounding portion 41 of the middle layer 4 may not be provided. For example, the covering member 7 may be grounded by being electrically connected to a grounded member that is provided separately from the pressure sensors 1 and 1A without going through the base material 2 .

The number, arrangement, and shape of the protrusions 72 are not limited to the above as long as they can suppress the movement of the diaphragm 51 drawn toward the facing surface 7a of the covering member 7. For example, in plan view, a plurality of linear ribs may extend parallel to each other.

Also, in the above description, the plurality of protrusions 72 are aligned in two orthogonal directions, but the present invention is not limited to this. In this specification, the term “lattice” means that a plurality of protrusions 72 are aligned in two directions on the facing surface 7a of the covering member 7 and the two directions intersect. For example, as in the example shown in FIG. 16, the two directions in which the plurality of protrusions 72 are aligned need not be orthogonal.

Also, although the covering member 7 is assumed to be grounded in the above description, it does not have to be grounded.

By appropriately combining any of the various embodiments described above, the respective effects can be achieved.

Although the present invention has been fully described in connection with preferred embodiments and with reference to the accompanying drawings, various variations and modifications will be apparent to those skilled in the art. Such variations and modifications are to be included therein insofar as they do not depart from the scope of the invention as set forth in the appended claims.

The pressure sensor according to the present invention is highly resistant to static electricity and is useful for various pressure sensors.

Reference Signs List 1, 1A Pressure sensor 2 Base material 4 Middle layer 41 Ground part 5 Upper layer 51 Diaphragm 51a Upper surface 51b Lower surface 52 Supporting part 7 Covering member 7a Opposing surface 7b Upper surface 7c Overlapping area 7e Edge 7f Surrounding part 72 Protruding part 73 Tip part 8 Communication hole 81 aperture 82 aperture 10 reference space 11 measurement space C virtual center point

Claims (11)

a diaphragm and a base material having a support portion surrounding the diaphragm when viewed from the thickness direction of the diaphragm;
a covering member that covers one surface of the diaphragm so as to form a measurement space between itself and the diaphragm, and that is joined to a supporting portion of the base material;
with
the diaphragm flexes due to pressure applied to one side of the diaphragm;
A communication hole is formed in the covering member to communicate the measurement space with the outside,
the covering member is grounded;
pressure sensor. The base material has a first layer and a second layer having the diaphragm and the support,
the second layer is laminated to the first layer so as to form a reference space between the first layer and the other side opposite to one side of the diaphragm;
The first layer has a ground portion that is grounded,
The covering member is electrically connected to the ground portion of the first layer,
A pressure sensor according to claim 1 . The covering member forms the measurement space and has a facing surface facing the diaphragm,
The covering member has a convex portion projecting toward the diaphragm in an overlap region overlapping the diaphragm when viewed from the thickness direction of the diaphragm on the facing surface.
The pressure sensor according to claim 1 or 2. The pressure sensor according to claim 3, wherein the convex portion is formed around the opening of the communication hole formed in the facing surface of the covering member. The covering member has a plurality of the convex portions,
The plurality of protrusions are formed in a grid pattern over the entire overlapping region of the covering member,
The pressure sensor according to claim 3 or 4. The pressure according to any one of claims 3 to 5, wherein the protrusion has a tapered shape in which the width of the protrusion decreases toward the diaphragm when viewed from a direction perpendicular to the thickness direction of the diaphragm. sensor. The pressure sensor according to any one of claims 3 to 6, wherein the tip of the convex portion has a curved surface. The covering member forms the measurement space and has a facing surface facing the diaphragm,
The opening of the communication hole formed in the facing surface does not overlap with the diaphragm when viewed from the thickness direction of the diaphragm.
The pressure sensor according to any one of claims 1-7. The covering member has a facing surface that forms the measurement space and faces the diaphragm, and an upper surface that is opposite to the facing surface,
The shortest distance between the opening of the communication hole formed in the top surface and the center of the top surface is shorter than the shortest distance between the opening of the communication hole formed in the top surface and the edge of the top surface. ,
The pressure sensor according to any one of claims 1-8. The pressure sensor according to any one of claims 1 to 9, wherein the covering member is thicker than the base material in the thickness direction of the diaphragm. The pressure sensor according to any one of claims 1 to 9, wherein the covering member is thinner than the base material in the thickness direction of the diaphragm.

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