Electrostatic capacitance type sensor

Abstract

An electrostatic capacitance sensor (1) includes: a top layer (70) having a boss portion (72) that receives a force acting in at least one of a first direction and a second direction intersecting the first direction; a diaphragm layer (50) laminated with the top layer (70) in a third direction intersecting the first and second directions, and deformed based on the force acting on the boss portion (72); and an electrode layer (30) laminated with the diaphragm layer (50) in the third direction, having an electrode (33) for forming an electrostatic capacitance that changes based on the force acting on the boss portion (72), and a first hole portion (SL1) that is open in the third direction is formed in a region of the diaphragm layer (50) overlapping the boss portion (72).

Description

Technical Field

[0001] This invention relates to electrostatic capacitive sensors. Background Technology

[0002] MEMS devices, fabricated using MEMS (Micro Electro Mechanical Systems) technology, are becoming increasingly common. Examples of MEMS devices include capacitive sensors that detect inertia, pressure, and other phenomena based on changes in electrostatic capacitance.

[0003] For example, Patent Document 1 discloses a mechanical quantity MEMS sensor having a first silicon layer and a second silicon layer bonded to the first silicon layer via a silicon oxide film. The first silicon layer has protrusions that are subjected to applied force and a diaphragm that elastically deforms according to the application of force to the protrusions. The mechanical quantity MEMS sensor detects the mechanical quantity applied to the protrusions based on the change in electrostatic capacitance formed by the second silicon layer.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 5714648 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] In the mechanical quantity MEMS sensor described in Patent Document 1, the flexibility of the diaphragm needs to be improved to enhance detection sensitivity. However, if the flexibility of the diaphragm is improved by thinning the diaphragm wall, the detection sensitivity may not be sufficiently improved due to thickness processing deviations.

[0009] The present invention was made in view of the following circumstances, and the object of the present invention is to provide an electrostatic capacitive sensor that can achieve improved detection sensitivity.

[0010] Solution for solving the problem

[0011] An electrostatic capacitive sensor according to one embodiment of the present invention comprises: a top layer having a boss portion that receives a force acting in at least one of a first direction and a second direction intersecting the first direction; a diaphragm layer that is stacked on the top layer in a third direction intersecting the first and second directions and deformable based on the force acting on the boss portion; and an electrode layer that is stacked on the diaphragm layer in the third direction and has an electrode for forming an electrostatic capacitance that varies based on the force acting on the boss portion, wherein a first hole portion opening in the third direction is formed in a region of the diaphragm layer overlapping the boss portion.

[0012] The effects of the invention

[0013] According to the present invention, an electrostatic capacitive sensor capable of improving detection sensitivity can be provided. Attached Figure Description

[0014] Figure 1 This is a cross-sectional view of the electrostatic capacitive sensor according to the first embodiment.

[0015] Figure 2 This is a top view of the first embodiment.

[0016] Figure 3 This is a top view of the diaphragm layer in the first embodiment.

[0017] Figure 4 This is a top view of the electrode layer in the first embodiment.

[0018] Figure 5 This is a top view of the electrode layer in the first embodiment.

[0019] Figure 6 This is a cross-sectional view of the electrostatic capacitive sensor according to the second embodiment.

[0020] Figure 7 This is a cross-sectional view of the electrostatic capacitive sensor according to the third embodiment.

[0021] Figure 8 This is a cross-sectional view of the electrostatic capacitive sensor according to the fourth embodiment.

[0022] Figure 9 This is a cross-sectional view of a modified example of the electrostatic capacitive sensor according to the first embodiment. Detailed Implementation

[0023] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The drawings in this embodiment are illustrative, and the dimensions and shapes of the parts are schematic. The technical scope of the present invention should not be limited to this embodiment.

[0024] <First Embodiment>

[0025] First, refer to Figures 1 to 5 The structure of the electrostatic capacitive sensor 1 according to the first embodiment of the present invention will be described. Figure 1 This is a cross-sectional view of the electrostatic capacitive sensor according to the first embodiment. Figure 2 This is a top view of the first embodiment. Figure 3 This is a top view of the diaphragm layer in the first embodiment. Figure 4 This is a top view of the electrode layer in the first embodiment. Figure 5 This is a top view of the electrode layer in the first embodiment.

[0026] The following describes the structure of the electrostatic capacitive sensor 1. In the various figures, to clarify the relationship between the figures and aid in understanding the positional relationships of the components, an orthogonal coordinate system consisting of the X-axis, Y-axis, and Z-axis is sometimes used for convenience. Directions parallel to the X-axis, Y-axis, and Z-axis are designated as the X-axis direction, Y-axis direction, and Z-axis direction, respectively. The surface defined by the X-axis and Y-axis is designated as the XY plane. Furthermore, for convenience, the positive Z-axis direction (the direction of the arrow) is designated as "up" or "above," and the negative Z-axis direction (opposite to the arrow) is designated as "down" or "below," but the orientation of the electrostatic capacitive sensor 1 is not limited to this.

[0027] The electrostatic capacitive sensor 1 is a device manufactured using MEMS technology. The electrostatic capacitive sensor 1 comprises a bottom layer 10, a bonding layer 20, an electrode layer 30, a diaphragm layer 50, an etch barrier layer 60, and a top layer 70. The electrostatic capacitive sensor 1 is a tactile sensor that detects forces in the X, Y, and Z axes by detecting changes in the electrostatic capacitance formed by the electrode layer 30. The bottom layer 10, bonding layer 20, electrode layer 30, diaphragm layer 50, etch barrier layer 60, and top layer 70 are sequentially stacked along the Z-axis. The electrode layer 30 is bonded to the bottom layer 10 via the bonding layer 20. The diaphragm layer 50 is directly bonded to the electrode layer 30. The top layer 70 is bonded to the diaphragm layer 50 via the etch barrier layer 60. The bonding between the electrode layer 30 and the diaphragm layer 50 is a direct bonding of single-crystal silicon. Movable spaces are formed between the bottom layer 10 and the electrode layer 30, and between the electrode layer 30 and the diaphragm layer 50, allowing the electrode 33 (described later) to move.

[0028] The bottom layer 10 is equivalent to the support substrate of the electrostatic capacitive sensor 1. The bottom layer 10 has a glass substrate 11, an internal electrode 12, a through electrode 13, an external electrode 14, and an insulating film 15.

[0029] The glass substrate 11 has an upper surface 11A disposed on the side opposite to the electrode layer 30 and a lower surface 11B disposed on the side opposite to the upper surface 11A. The glass substrate 11 is a flat substrate, with the upper surface 11A and the lower surface 11B extending along the XY plane. The upper surface 11A and the lower surface 11B correspond to a pair of main surfaces of the glass substrate 11. The glass substrate 11 is formed of glass with silicon oxide (e.g., SiO2) as its main component. Here, the main component in the glass refers to the component that accounts for more than 50% by mass of the total components constituting the glass. As an example, the glass substrate 11 is formed of silicate glass with SiO2 as its main component.

[0030] The internal electrode 12 is electrically connected to the electrode layer 30, or forms an electrostatic capacitance between it and the electrode layer 30. The internal electrode 12 is disposed on the upper surface 11A of the glass substrate 11. The internal electrode 12 is, for example, a single-layer structure made of aluminum (Al), but is not limited thereto. The internal electrode 12 may also contain layers made of gold (Au), silver (Ag), copper (Cu), titanium (Ti), germanium (Ge), molybdenum (Mo), aluminum (Al), silicon (Si), or alloys thereof. The internal electrode 12 may also be a multilayer structure containing two or more conductive layers.

[0031] The through electrode 13 electrically connects the internal electrode 12 to the external electrode 14. The through electrode 13 is configured to penetrate the glass substrate 11 along the Z-axis direction. The through electrode 13 is made of silicon (Si), for example, but is not limited to this. The through electrode 13 may also be made of gold (Au), silver (Ag), copper (Cu), titanium (Ti), germanium (Ge), molybdenum (Mo), aluminum (Al), silicon (Si), or alloys thereof.

[0032] The external electrode 14 is used to electrically connect the electrostatic capacitive sensor 1 to an external circuit. The external electrode 14 is disposed on the lower surface 11B of the glass substrate 11. The external electrode 14 may be a single-layer structure made of aluminum (Al), but is not limited thereto. The external electrode 14 may also contain layers made of gold (Au), silver (Ag), copper (Cu), titanium (Ti), germanium (Ge), molybdenum (Mo), aluminum (Al), silicon (Si), or alloys thereof. The external electrode 14 may also be a multilayer structure containing two or more conductive layers.

[0033] The insulating film 15 suppresses short circuits in the external electrode 14. The insulating film 15 is disposed on the lower surface 11B of the glass substrate 11. The insulating film 15 covers the end of the external electrode 14, partially exposing the external electrode 14. The insulating film 15 is made of an insulating material. The insulating film 15 may also function as a buffer material that absorbs impacts from the outside and suppresses damage to the glass substrate 11.

[0034] The bonding layer 20 bonds and electrically connects the bottom layer 10 to the electrode layer 30. The bonding layer 20 forms a movable space on the negative Z-axis side with respect to the electrode 33 of the electrode layer 30 (described later). That is, the thickness of the bonding layer 20 in the Z-axis direction (hereinafter simply referred to as "thickness") corresponds to the movable range on the negative Z-axis side of the electrode 33. The bonding layer 20 is, for example, made of an Al-Ge-Ti eutectic alloy containing aluminum, germanium, and titanium, but is not limited thereto. The bonding layer 20 may also be made of an Al-Si eutectic alloy containing aluminum and silicon, an Au-Sn eutectic alloy containing gold and tin, or an Au-Si eutectic alloy containing gold and silicon, etc.

[0035] The bonding layer 20 has bonding portions 21 and 22. Bonding portion 21 partially grounds the electrode layer 30. Bonding portion 21 bonds the outer edge 35 of the electrode layer 30 (described later) to the glass substrate of the bottom layer 10. Bonding portion 21 is electrically connected to the internal electrode 12, which is connected to the ground electrode. Bonding portion 22 electrically connects the electrode 33 of the electrode layer 30 to an external circuit. Bonding portion 22 bonds the outer edge 35 of the electrode layer 30 (described later) to the glass substrate of the bottom layer 10. Bonding portion 22 is electrically connected to the internal electrode 12, which is connected to the external circuit.

[0036] When viewed from above along the Z-axis (hereinafter referred to as "top view"), the joint 21 is frame-shaped along the outer edge of the electrostatic capacitive sensor 1. In the top view, the joint 22 is located in the area surrounded by the joint 21. The joint 21 acts as a sealing frame that seals the movable space of the electrode 33, described later.

[0037] The electrode layer 30 forms an electrostatic capacitance that changes based on the force acting on the electrostatic capacitive sensor 1. The electrode layer 30 is made of a silicon substrate 31. The silicon substrate 31 is formed, for example, from a single crystal of p-type silicon (Si). The silicon substrate 31 may contain boron (B) or the like as a p-type dopant. The resistivity of the silicon (Si) used in the silicon substrate 31 is, for example, about 10 mΩ·cm.

[0038] The electrode layer 30 has a force-receiving portion 32, a plurality of electrodes 33, and an outer edge portion 35. A cavity 40 is formed on the diaphragm layer 50 side of the plurality of electrodes 33 in the electrode layer 30. That is, the silicon substrate 31 is provided with a concave shape at the electrode 33 that opens toward the diaphragm layer 50 side. The cavity 40 forms a movable space in the positive Z-axis direction with respect to the electrodes 33 of the electrode layer 30. That is, the depth of the cavity 40 in the Z-axis direction (hereinafter simply referred to as "depth") corresponds to the movable range in the positive Z-axis direction of the electrode 33. In addition, the cavity 40 also corresponds to the movable range in the negative Z-axis direction with respect to the diaphragm portion 53 of the diaphragm layer 50, which will be described later.

[0039] The force-receiving part 32 receives the force acting on the boss part 72 of the top layer 70 (described later), causing the electrode 33 to shift. For example... Figure 4 As shown, in a top view, the force-bearing part 32 is located in the center of the electrode layer 30. Figure 1 As shown, the force-receiving part 32 is directly connected to the transmission part 52 of the membrane layer 50 described later, and is separated from the bottom layer 10.

[0040] Multiple electrodes 33 form an electrostatic capacitance that varies based on the force acting on the protrusion 72 of the top layer 70 (described later). Each of the multiple electrodes 33 is configured to be displaceable in the X-axis, Y-axis, or Z-axis direction based on the force acting on the protrusion 72 of the top layer 70. The electrostatic capacitance formed by the electrodes 33 varies due to the displacement of the electrodes 33 based on the force acting on the protrusion 72 of the top layer 70. Figure 4As shown, the electrodes 33 are, for example, comb-shaped electrodes arranged in the X-axis or Y-axis direction. The electrostatic capacitance formed by the electrodes 33 is formed between the electrodes 33. Multiple electrodes 33 are connected to the force-receiving portion 32 and the outer edge portion 35, and are disposed between the force-receiving portion 32 and the outer edge portion 35 in the XY plane direction. Figure 1 As shown, multiple electrodes 33 are separated from the bottom layer 10 and the membrane layer 50.

[0041] Furthermore, electrode 33 can also be a plate-shaped electrode having a main surface along the XY plane. In addition, the electrostatic capacitance formed by electrode 33 can also be formed between electrode 33 and the internal electrode 12 of the bottom layer 10, and can also be formed between electrode 33 and the membrane layer 50.

[0042] The outer edge 35 holds the electrode 33. For example... Figure 4 As shown, when viewed from above, the outer edge 35 is frame-shaped along the outer edge of the electrostatic capacitive sensor 1. Figure 1 As shown, the outer edge 35 is bonded to the bottom layer 10 via the bonding layer 20, and is directly bonded to the outer edge 55 of the membrane layer 50 described later.

[0043] A hole SL4 is formed at the outer edge 35. For example... Figure 1 As shown, the hole SL4 penetrates the silicon substrate 31 along the Z-axis direction. Figure 5 As shown, the aperture SL4 is formed as a slit. Additionally, as... Figure 1 and Figure 5 As shown, the hole SL4 electrically separates the portion of electrode layer 30 connected to electrode 33 from the portion of electrode layer 30 connected to ground. Hole SL4 is an example of the fourth hole.

[0044] The diaphragm layer 50 deforms based on the force acting on the electrostatic capacitive sensor 1. Furthermore, the diaphragm layer 50 isolates the cavity 40 from the external air. The diaphragm layer 50 is made of a silicon substrate 51. The silicon substrate 51 is formed, for example, from a single crystal of p-type silicon (Si). The silicon substrate 51 may contain boron (B) or the like as a p-type dopant. The resistivity of the silicon (Si) used in the silicon substrate 51 is, for example, about 10 mΩ·cm.

[0045] The diaphragm layer 50 has a transfer portion 52, a diaphragm portion 53, and an outer edge portion 55. The thickness of the transfer portion 52, the diaphragm portion 53, and the outer edge portion 55 of the diaphragm layer 50 is approximately equal.

[0046] The transmission section 52 receives the force acting on the boss portion 72 of the top layer 70 (described later) and transmits it to the force-receiving portion 32 of the electrode layer 30. For example... Figure 3 As shown, in a top view, the transfer portion 52 is located in the center of the diaphragm layer 50, and is the area in the diaphragm layer 50 that overlaps with the boss portion 72. Figure 1As shown, the transfer portion 52 is directly bonded to the force-receiving portion 32 of the electrode layer 30, and is bonded to the boss portion 72 of the top layer 70 (described later) via the etching barrier layer 60.

[0047] A hole SL1 is formed in the transfer section 52. For example... Figure 1 As shown, the hole SL1 penetrates the silicon substrate 51 along the Z-axis direction. Figure 3 As shown, the aperture SL1 is formed as a slit. Additionally, as... Figure 3 As shown, in top view, the hole portion SL1 is frame-shaped inside the boss portion 72 of the top layer 70, which will be described later. The portion of the transmission portion 52 surrounded by the hole portion SL1 is connected to the portion of the transmission portion 52 located outside the hole portion SL1 by the boss portion 72. The hole portion SL1 corresponds to an example of the first hole portion.

[0048] Furthermore, the aperture SL1 is not limited to penetrating the silicon substrate 51 along the Z-axis direction; it can open to at least one side of the silicon substrate 51 in the positive Z-axis direction and the negative Z-axis direction. Additionally, in plan view, the aperture SL1 may be, for example, a rectangular frame shape, but is not limited to this. The aperture SL1 may also be a polygonal frame shape, a circular frame shape, an elliptical frame shape, or a frame shape composed of combinations thereof. Furthermore, the aperture SL1 may not be a frame shape but rather a plurality of slits separated from each other. As an example, in plan view, slit-shaped aperture SL1 extending along the X-axis direction and slit-shaped aperture SL1 extending along the Y-axis direction may be formed separately in the transfer section 52. Furthermore, in plan view, the aperture SL1 is not limited to being formed as a slit shape; for example, it may be formed as a dot. As an example, a plurality of dot-shaped aperture SL1 arranged along the X-axis direction and a plurality of dot-shaped aperture SL1 arranged along the Y-axis direction may be formed in the transfer section 52.

[0049] The diaphragm portion 53 deforms based on the force acting on the boss portion 72 of the top layer 70, which will be described later. For example... Figure 1 As shown, the diaphragm portion 53 is configured in a membrane shape, capable of flexing and deforming. For example... Figure 3 As shown, the diaphragm portion 53 connects the boss portion 72 of the top layer 70 (described later) to the outer edge portion 75, covering the gap between the boss portion 72 and the outer edge portion 75. Figure 1 As shown, the diaphragm portion 53 is joined to the boss portion 72 and the outer edge portion 75 of the top layer 70 (described later) via the etch barrier layer 60, and is separated from the electrode layer 30 through the cavity 40.

[0050] The outer edge 55 retains the diaphragm portion 53. For example... Figure 3 As shown, when viewed from above, the outer edge 55 is frame-shaped along the outer edge of the electrostatic capacitive sensor 1. Figure 1 As shown, the outer edge 55 is bonded to the outer edge 75 of the top layer 70 (described later) via the etch barrier layer 60, and is directly bonded to the outer edge 35 of the electrode layer 30.

[0051] A hole SL3 is formed at the outer edge 55. For example... Figure 1 As shown, hole SL3 penetrates the silicon substrate 31 along the Z-axis. A portion of hole SL3 is connected to hole SL4. Figure 3 As shown, the aperture SL3 is formed as a slit. Additionally, as... Figure 3 As shown, when viewed from above, the hole SL3 is formed in a frame shape. Additionally, as... Figure 1 and Figure 3 As shown, the aperture SL3 electrically separates the portion of the diaphragm layer 50 connected to the electrode 33 from the portion of the diaphragm layer 50 connected to ground. The aperture SL3 is an example of the third aperture.

[0052] like Figure 9 As shown in the modified example, at least a portion of the plurality of holes SL3 can be formed as a part of a frame-shaped outer edge 55 extending through the XY plane, thereby opening the cavity 40 to the outside air. That is, when viewed from above, at least a portion of the plurality of holes SL3 can also have the frame-shaped outer edge 55 circumferentially truncated. When the cavity 40 is opened to the outside air using the holes SL3, the vacuum level inside the electrostatic capacitive sensor 1 is approximately equal to the vacuum level outside the electrostatic capacitive sensor 1. When the vacuum level inside the electrostatic capacitive sensor 1 is approximately equal to the vacuum level outside, no pressure is applied to the boss portion 72 or the diaphragm portion 53 due to the difference in vacuum level. Therefore, the detected electrostatic capacitance value is also equal in places with different external air pressures (e.g., high and low places). That is, the variation in the detection accuracy of the electrostatic capacitive sensor 1 caused by the external environment can be suppressed, and the force acting on the boss portion 72 can be detected with high accuracy. Furthermore, the opening for the cavity 40 to be open to the outside air is not limited to being formed on the outer edge 55, but may also be formed on the outer edge 75, outer edge 35, outer edge 75 or joints 21, 22.

[0053] The etch barrier layer 60 is provided to block the etching of the silicon substrate 51 of the separator layer 50 or the etching of the silicon substrate 71 of the top layer 70 (described later). For example, when etching the silicon substrate 51 to form holes SL1 and SL3, the etch barrier layer 60 hinders the progress of the etching process in the Z-axis direction. Additionally, for example, when etching the silicon substrate 71 to form the gap between the boss portion 72 and the outer edge portion 75 of the top layer 70 (described later), the etch barrier layer 60 hinders the progress of the etching process in the Z-axis direction. Specifically, when the silicon substrate 51 and silicon substrate 71 are bonded via the etch barrier layer 60, and the silicon substrate 51 or silicon substrate 71 is etched using deep reactive ion etching (DRIE), the silicon oxide of the etch barrier layer 60 does not react with the silicon-reactive etching agent. Therefore, when the silicon substrate 51 or silicon substrate 71 is penetrated, the progress of the etching process in the Z-axis direction is hindered.

[0054] Furthermore, the etch barrier layer 60 electrically insulates the diaphragm layer 50 from the top layer 70. By electrically insulating the diaphragm layer 50 from the top layer 70, the reliability of the capacitive sensor 1 can be improved. This is because the top layer 70 is the point of contact between the capacitive sensor 1 and the outside, so charge may flow into the top layer 70 from the outside. However, by using the etch barrier layer 60 to electrically insulate the top layer 70 from the diaphragm layer 50, the charge flowing into the top layer 70 can be blocked from flowing into the diaphragm layer 50 and the electrode layer 30, and the adhesion and melting of the electrode 33 due to the inflow of charge can be suppressed. The etch barrier layer 60 is provided on approximately the entire surface of the capacitive sensor 1 in the XY plane direction. The etch barrier layer 60 is made of silicon oxide. The etch barrier layer 60 can be provided, for example, by thermal oxidation of the silicon substrate 51 or the silicon substrate 71, but is not limited to this, and can also be provided by sputtering, CVD (Chemical Vapor Deposition), etc.

[0055] The top layer 70 constitutes the detection surface for detecting the force acting on the electrostatic capacitive sensor 1. The top layer 70 is composed of a silicon substrate 71. The silicon substrate 71 is formed, for example, from a single crystal of p-type silicon (Si). The silicon substrate 71 may contain boron (B) or the like as a p-type dopant. The resistivity of the silicon (Si) used in the silicon substrate 71 is, for example, about 10 mΩ·cm.

[0056] Furthermore, the top layer 70 is a layer provided for displacing the electrode 33 based on the force acting on the boss 72, and does not need to be electrically connected to the separator layer 50 or the electrode layer 30. Therefore, the silicon (Si) used in the silicon substrate 71 can also be high-resistivity silicon (Si) with a resistivity of, for example, 1 kΩ·cm or higher. As a result, the parasitic capacitance formed between the top layer 70 and the separator layer 50 can be suppressed. Therefore, the detection sensitivity of the electrostatic capacitive sensor 1 can be improved.

[0057] The top layer 70 has a boss 72 and an outer edge 75. The thickness of the boss 72 and the outer edge 75 of the top layer is approximately equal.

[0058] The boss portion 72 receives forces acting in at least one of the X-axis and Y-axis directions. For example, when the boss portion 72 receives a force F in the positive X-axis direction, with fulcrum P as the fulcrum, the force-receiving portion 32 receives a force in the negative X-axis direction, and the electrode 33 shifts in the negative X-axis direction by a displacement D. The position of the fulcrum P is determined by the thickness of the boss portion 72, the thickness of the transmission portion 52, the thickness of the force-receiving portion 32, and the depth of the hole portion SL1, etc. Figure 2 As shown, when viewed from above, the boss 72 is located in the center of the top layer 70.

[0059] The outer edge 75 connects the region located outside the aperture SL3 when viewed from above with the region located inside the aperture SL3. For example... Figure 2 As shown, in a top view, the outer edge 75 is frame-shaped along the outer edge of the electrostatic capacitive sensor 1. The outer edge 75 is spaced apart from the boss 72 in the XY plane direction. The gap between the boss 72 and the outer edge 75 is frame-shaped. That is, the outer edge 75 is separated from the boss 72 in all directions in the XY plane.

[0060] Furthermore, the outer edge 75 is not limited to being separated from the boss 72 in all directions. The outer edge 75 may also be connected to the boss 72 in at least a portion of the XY plane. For example, the outer edge 75 may be connected to the boss 72 using a thin-walled connecting portion with a thickness smaller than that of the boss 72 and the outer edge 75. Alternatively, for example, the outer edge 75 may be connected to the boss 72 using a beam-like connecting portion extending in a predetermined direction within the XY plane. However, from the viewpoint of improving the mobility of the boss 72, it is desirable that the outer edge 75 be separated from the boss 72 in all directions.

[0061] As described above, the electrostatic capacitive sensor 1 of this embodiment includes a top layer 70, a diaphragm layer 50, and an electrode layer 30, which are stacked sequentially in the Z-axis direction. The top layer 70 has a boss portion 72 that receives a force acting in at least one of the X-axis and Y-axis directions. The diaphragm layer 50 deforms based on the force acting on the boss portion 72. The electrode layer 30 has an electrode 33 for forming an electrostatic capacitance that varies based on the force acting on the boss portion 72. A hole SL1 opening in the Z-axis direction is formed in the region of the diaphragm layer 50 that overlaps with the boss portion 72.

[0062] As a result, the flexibility of the diaphragm layer 50 is improved, thus increasing the mobility of the boss portion 72 when a force F is applied, and consequently increasing the displacement D of the electrode 33. Therefore, the change in electrostatic capacitance formed by the electrode 33 increases, improving the detection accuracy of the electrostatic capacitive sensor 1.

[0063] As one of the above-mentioned technical solutions, the hole SL1 is formed into a slit shape.

[0064] Therefore, compared with the case where the pores SL1 are formed as dots, the flexibility of the membrane layer 50 can be further improved.

[0065] As one of the above-mentioned technical solutions, the hole SL1 is formed in a frame shape.

[0066] This improves the flexibility of the membrane layer 50 in the X-axis direction, the Y-axis direction, and the Z-axis direction.

[0067] As one of the above technical solutions, the electrostatic capacitive sensor 1 also includes an etch barrier layer 60 disposed between the top layer 70 and the diaphragm layer 50, wherein the top layer 70 and the diaphragm layer 50 are made of silicon, and the etch barrier layer 60 is made of silicon oxide.

[0068] Therefore, for example, after bonding the silicon substrate 71 of the top layer 70 to the silicon substrate 51 of the separator layer 50 via the etch barrier layer 60, when etching the silicon substrate 71 to form the boss portion 72 and the outer edge portion 75, the silicon substrate 51 can be prevented from being removed by the etching process. Conversely, when etching the silicon substrate 51 to form the holes SL1 and SL3, the silicon substrate 71 can be prevented from being removed by the etching process. In addition, by using the etch barrier layer 60 to electrically insulate the separator layer 50 from the top layer 70, the inflow of charge from the outside through the top layer 70 into the separator layer 50 and the electrode layer 30 can be suppressed. As a result, adhesion and melting in the electrodes 33 of the electrode layer 30 can be suppressed, thereby improving the reliability of the electrostatic capacitive sensor 1.

[0069] As one of the above technical solutions, the electrode layer 30 is composed of a silicon substrate 31, the separator layer 50 is composed of a silicon substrate 51, and the electrode layer 30 and the separator layer 50 are directly bonded to each other.

[0070] Therefore, the diaphragm layer 50 and the electrode layer 30 can be electrically connected without using through electrodes or the like, which have high manufacturing costs.

[0071] As one of the above technical solutions, a hole SL3 is formed in the diaphragm layer 50 that penetrates the silicon substrate 51 along the Z-axis direction, and a hole SL4 is formed in the electrode layer 30 that penetrates the silicon substrate 31 along the Z-axis direction and communicates with the hole SL3.

[0072] Therefore, the membrane layer 50 can be divided into multiple parts using the pores SL3, allowing each part of the membrane layer 50 to have a different potential. Similarly, the electrode layer 30 can be divided into multiple parts using the pores SL4, allowing each part of the electrode layer 30 to have a different potential.

[0073] As one of the above-mentioned technical solutions, the pore SL3 can be formed as a frame that partially surrounds the diaphragm layer 50.

[0074] Therefore, the portion of the diaphragm layer 50 surrounded by the pore SL3 and the portion located outside the pore SL3 can be made to have different potentials. For example, when the portion of the diaphragm layer 50 surrounded by the pore SL3 is bonded to the portion of the electrode layer 30 connected to the electrode 33, it is possible to electrically connect the portion of the diaphragm layer 50 surrounded by the pore SL3 to the electrode 33 while simultaneously grounding the portion of the diaphragm layer 50 located outside the pore SL3.

[0075] As one of the above technical solutions, the pore SL3 penetrates the outer edge 55 of the diaphragm layer 50 in the XY plane direction, so that the cavity 40 is open to the external gas.

[0076] Therefore, the vacuum level inside the capacitive sensor 1 is approximately equal to the vacuum level outside the capacitive sensor 1, so no pressure is applied to the boss portion 72 or the diaphragm portion 53 due to the difference in vacuum level. Thus, the detected electrostatic capacitance value is also equal in locations with different external air pressures (e.g., high and low locations). That is, variations in the detection accuracy of the capacitive sensor 1 caused by the external environment can be suppressed, and the force acting on the boss portion 72 can be detected with high precision.

[0077] As one of the above technical solutions, a cavity 40 is formed on the diaphragm layer 50 side of the electrode layer 30.

[0078] Therefore, the distance from the fulcrum P to the electrode 33 can be adjusted by utilizing the depth of the cavity 40, thus increasing the displacement D of the electrode 33. Consequently, the change in electrostatic capacitance formed by the electrode 33 increases, thereby improving the detection accuracy of the electrostatic capacitive sensor 1.

[0079] As one of the above technical solutions, electrode 33 is a comb electrode.

[0080] Therefore, compared with the case where electrode 33 is a flat plate electrode, the detection accuracy of electrostatic capacitive sensor 1 can be improved.

[0081] Other embodiments will be described below. Furthermore, structures that are the same as or similar to those shown in the first embodiment will be labeled with the same or similar reference numerals, and their descriptions will be omitted where appropriate. Additionally, the same effects achieved by the same structures will not be mentioned repeatedly.

[0082] <Second Implementation>

[0083] Next, refer to Figure 6 The structure of the electrostatic capacitive sensor 2 according to the second embodiment will be described. Figure 6 This is a cross-sectional view of the electrostatic capacitive sensor 2 according to the second embodiment.

[0084] A hole SL2 is formed on the boss portion 272 of the top layer 270. A hole SL5 is formed on the outer edge portion 275 of the top layer 270. Hole SL2 opens in the Z-axis direction and communicates with hole SL1. Hole SL5 opens in the Z-axis direction and communicates with hole SL3. Holes SL2 and SL5 are bottomed holes that open toward the membrane layer 50. Hole SL2 is formed as a slit extending in the X-axis and Y-axis directions, and forms a frame shape along hole SL1 when viewed from above. Hole SL5 is formed as a slit extending in the X-axis and Y-axis directions, and forms a frame shape along hole SL3 when viewed from above. Hole SL2 corresponds to an example of the second hole, and hole SL5 corresponds to an example of the fifth hole.

[0085] The boss portion 272 has a leaf spring portion LS1. The leaf spring portion LS1 is located outside the hole portion SL2 in the XY plane direction. The leaf spring portion LS1 is a plate-like portion located between the outer side of the boss portion 272 and the hole portion SL2 in the XY plane direction. When a force is applied to the boss portion 272 in the X-axis direction, the leaf spring portion LS1, which has a main surface extending in the YZ plane direction, bends and deforms in the X-axis direction, providing a restoring force to the boss portion 272 and the electrode 33. The thickness of the leaf spring portion LS1, which has a main surface extending in the YZ plane direction, in the X-axis direction is smaller than the thickness of the diaphragm layer 50 in the Z-axis direction. In addition, when a force is applied to the boss portion 272 in the Y-axis direction, the leaf spring portion LS1, which has a main surface extending in the ZX plane direction, bends and deforms in the Y-axis direction, providing a restoring force to the boss portion 272 and the electrode 33. The thickness of the leaf spring portion LS1, which has a main surface extending along the ZX plane, in the Y-axis direction is smaller than the thickness of the diaphragm layer 50 in the Z-axis direction.

[0086] As explained above, in the electrostatic capacitive sensor 2 of this embodiment, a hole SL2 is formed in the boss portion 272, and the hole SL2 communicates with the hole SL1. This increases the flexibility of the top layer 270, thus improving the mobility of the boss portion 272 when force is applied, and increasing the displacement of the electrode 33. Consequently, the change in electrostatic capacitance formed by the electrode 33 increases, improving the detection accuracy of the electrostatic capacitive sensor 2.

[0087] As one of the above-mentioned technical solutions, the hole SL2 is formed into a slit shape.

[0088] Therefore, compared with the case where the pores SL2 are formed as dots, the flexibility of the top layer 270 can be further improved.

[0089] As one of the above-mentioned technical solutions, the hole SL2 is formed in a frame shape.

[0090] This improves the flexibility of the top layer 270 in the X-axis direction, Y-axis direction, and Z-axis direction.

[0091] As one of the above technical solutions, the thickness of the leaf spring portion LS1 in the direction of bending deformation is smaller than the thickness of the diaphragm layer 50.

[0092] This allows for a further improvement in the flexibility of the top 270 layer.

[0093] <Third Implementation>

[0094] Next, refer to Figure 7 The structure of the electrostatic capacitive sensor 3 according to the third embodiment will be described. Figure 7 This is a cross-sectional view of the electrostatic capacitive sensor 3 according to the third embodiment.

[0095] A cavity 340 is formed on the electrode layer 330 side of the diaphragm layer 350 of the electrostatic capacitive sensor 3. The diaphragm layer 350 is provided with a concave shape at the diaphragm portion 353, opening towards the electrode layer 330 side. In the diaphragm layer 350, the thickness of the diaphragm portion 353 is smaller than the thickness of the transmission portion 52 and the outer edge portion 55. In the electrode layer 330 of the electrostatic capacitive sensor 3, the thickness of the force-receiving portion 32, the thickness of the electrode 333, and the thickness of the outer edge portion 35 are approximately equal to each other.

[0096] <Fourth Implementation>

[0097] Next, refer to Figure 8 The structure of the electrostatic capacitive sensor 4 in the fourth embodiment will be described. Figure 8 This is a cross-sectional view of the electrostatic capacitive sensor 4 according to the fourth embodiment.

[0098] In the electrostatic capacitive sensor 4, the ends of the electrode layer 430, the diaphragm layer 450, and the etch barrier layer 460 in the XY plane direction are located further inward than the ends of the bottom layer 10 and the top layer 470 in the XY plane direction. A recess RC5 with the same depth as the hole SL5 is formed on the outer edge 475 of the top layer 470. The recess RC5 opens outward in the XY plane direction and in the negative Z-axis direction.

[0099] Therefore, when the electrostatic capacitive sensor 4 is monolithically processed by cutting the substrate of multiple interconnected electrostatic capacitive sensors 4, the cutting depth is small, thus suppressing the generation of defective products. Furthermore, when using laser cutting to monolithize the electrostatic capacitive sensor 4, the cutting speed can be increased, thereby reducing cutting costs.

[0100] The following describes some or all of the embodiments of the present invention. However, the present invention is not limited to the following descriptions.

[0101] <1>

[0102] An electrostatic capacitive sensor, wherein,

[0103] This electrostatic capacitive sensor features:

[0104] The top layer has a boss portion that receives forces acting in at least one of a first direction and a second direction intersecting the first direction;

[0105] A diaphragm layer, which is stacked on the top layer in a third direction intersecting the first and second directions, deforms based on the force acting on the boss; and

[0106] An electrode layer, which is stacked with a diaphragm layer in the third direction, has electrodes for forming electrodes that vary based on the electrostatic capacitance acting on the boss portion.

[0107] A first hole with an opening in the third direction is formed in the region of the membrane layer that overlaps with the boss portion.

[0108] <2>

[0109] According to the electrostatic capacitive sensor described in <1>, wherein,

[0110] A second hole is formed in the top boss portion, which opens in the third direction.

[0111] The second hole is connected to the first hole.

[0112] <3>

[0113] According to the electrostatic capacitive sensor described in <2>, wherein,

[0114] The first and second holes are formed as slits extending along the first or second direction.

[0115] <4>

[0116] According to the electrostatic capacitive sensor described in <3>, wherein...

[0117] When viewed from the third direction, the first and second holes form a frame shape.

[0118] <5>

[0119] According to any one of <2> to <4>, the electrostatic capacitive sensor, wherein,

[0120] The boss portion has a leaf spring portion located outside the second hole portion.

[0121] The thickness of the leaf spring portion in the direction of bending deformation based on the force acting on the boss portion is smaller than the thickness of the diaphragm layer in the third direction.

[0122] <6>

[0123] According to any one of <1> to <5>, the electrostatic capacitive sensor, wherein,

[0124] This electrostatic capacitive sensor also features an etching barrier layer disposed between the top layer and the diaphragm layer.

[0125] The top layer and the separator layer are made of silicon.

[0126] The etch barrier layer is made of silicon oxide.

[0127] <7>

[0128] According to the electrostatic capacitive sensor described in <6>, wherein,

[0129] The electrode layer is made of silicon.

[0130] The membrane layer and the electrode layer are directly bonded to each other.

[0131] <8>

[0132] According to the electrostatic capacitive sensor described in <7>, wherein...

[0133] A third pore is formed in the diaphragm layer, extending through the diaphragm layer in the third direction.

[0134] A fourth hole is formed in the electrode layer, which penetrates the electrode layer and communicates with the third hole.

[0135] <9>

[0136] According to the electrostatic capacitive sensor described in <8>, wherein,

[0137] The third pore is formed as a local frame surrounding the diaphragm layer.

[0138] <10>

[0139] According to the electrostatic capacitive sensor described in <8> or <9>, wherein,

[0140] The diaphragm layer has an outer edge portion that is frame-shaped when viewed from a third direction along the diaphragm layer.

[0141] The third hole extends through the outer edge of the diaphragm layer in a direction along the surface including the first and second directions, so that the cavity formed between the electrode layer and the diaphragm layer is open to the outside air.

[0142] <11>

[0143] According to any one of <1> to <10>, the electrostatic capacitive sensor, wherein,

[0144] A cavity is formed on the diaphragm layer side of the electrode layer.

[0145] <12>

[0146] According to any one of <1> to <11>, the electrostatic capacitive sensor, wherein,

[0147] The electrode is a comb electrode.

[0148] <13>

[0149] According to any one of <1> to <12>, the electrostatic capacitive sensor, wherein,

[0150] The top layer also has a frame-shaped outer edge when viewed from a third direction along the top layer.

[0151] A third pore is formed in the diaphragm layer, extending through the diaphragm layer in the third direction.

[0152] A bottomed fifth hole, which communicates with the third hole, is formed on the outer edge of the top layer, and a recess with the same size as the fifth hole in the third direction and which opens on the outer edge.

[0153] As explained above, according to a technical solution of the present invention, an electrostatic capacitive sensor capable of improving detection sensitivity can be provided.

[0154] Furthermore, the embodiments described above are intended to facilitate understanding of the present invention and are not intended to limit the scope of the invention. The present invention can be modified / improved without departing from its spirit, and the present invention also includes its equivalents. That is, embodiments obtained by those skilled in the art through appropriate design modifications to the embodiments, as long as they possess the features of the present invention, are also included within the scope of the present invention. For example, the elements, their configurations, materials, conditions, shapes, dimensions, etc., of each embodiment are not limited to the illustrated contents and can be appropriately modified. In addition, the elements of each embodiment can be combined within a technically feasible range, and the technology formed by combining them, as long as it contains the features of the present invention, is also included within the scope of the present invention.

[0155] Explanation of reference numerals in the attached figures

[0156] 1. Electrostatic capacitive sensor; 10. Bottom layer; 11. Glass substrate; 20. Bonding layer; 30. Electrode layer; 31. Silicon substrate; 32. Force-receiving part; 33. Electrode; 35. Outer edge; 40. Cavity; 50. Diaphragm layer; 51. Silicon substrate; 52. Transmission part; 53. Diaphragm part; 55. Outer edge; 60. Etching barrier layer; 70. Top layer; 71. Silicon substrate; 72. Boss part; 75. Outer edge; SL1~SL5. Hole part; F, Force; P, Fulcrum; D, Displacement.

Claims

1. An electrostatic capacitive sensor, wherein, This electrostatic capacitive sensor features: The top layer has a boss portion that receives forces acting in at least one of a first direction and a second direction intersecting the first direction; A diaphragm layer, which is stacked on the top layer in a third direction intersecting the first and second directions, deforms based on the force acting on the boss portion; as well as An electrode layer, which is stacked with the diaphragm layer in the third direction, has electrodes forming an electrostatic capacitance that varies based on the force acting on the boss portion. A first hole is formed in the region of the diaphragm layer that overlaps with the boss portion, opening in the third direction.

2. The electrostatic capacitive sensor according to claim 1, wherein, The boss portion of the top layer has a second hole that opens in the third direction. The second hole is connected to the first hole.

3. The electrostatic capacitive sensor according to claim 2, wherein, The first hole and the second hole are formed as slits extending along the first direction or the second direction.

4. The electrostatic capacitive sensor according to claim 3, wherein, When viewed from the third direction, the first hole and the second hole are formed in a frame shape.

5. The electrostatic capacitive sensor according to any one of claims 2 to 4, wherein, The boss portion has a leaf spring portion located outside the second hole portion. The thickness of the leaf spring portion in the direction of bending deformation based on the force acting on the boss portion is smaller than the thickness of the diaphragm layer in the third direction.

6. The electrostatic capacitive sensor according to any one of claims 1 to 5, wherein, The electrostatic capacitive sensor also includes an etch barrier layer disposed between the top layer and the diaphragm layer. The top layer and the diaphragm layer are made of silicon. The etch barrier layer is made of silicon oxide.

7. The electrostatic capacitive sensor according to claim 6, wherein, The electrode layer is made of silicon. The diaphragm layer and the electrode layer are directly bonded to each other.

8. The electrostatic capacitive sensor according to claim 7, wherein, A third hole is formed in the diaphragm layer, extending through the diaphragm layer along the third direction. A fourth hole is formed in the electrode layer, which penetrates the electrode layer and communicates with the third hole.

9. The electrostatic capacitive sensor according to claim 8, wherein, The third hole is formed as a frame that partially surrounds the diaphragm layer.

10. The electrostatic capacitive sensor according to claim 8 or 9, wherein, The diaphragm layer has an outer edge portion that is frame-shaped when viewed from the third direction along the diaphragm layer. The third hole extends through the outer edge of the diaphragm layer in a direction along the surface including the first direction and the second direction, so that the cavity formed between the electrode layer and the diaphragm layer is open to the outside air.

11. The electrostatic capacitive sensor according to any one of claims 1 to 10, wherein, A cavity is formed on the diaphragm layer side of the electrode layer.

12. The electrostatic capacitive sensor according to any one of claims 1 to 11, wherein, The electrode is a comb electrode.

13. The electrostatic capacitive sensor according to any one of claims 1 to 12, wherein, The top layer also has an outer edge portion that is frame-shaped when viewed from the third direction along the top layer. A third hole is formed in the diaphragm layer, extending through the diaphragm layer along the third direction. A bottomed fifth hole, communicating with the third hole, is formed on the outer edge of the top layer, and a recess with the same size as the fifth hole in the third direction and open on the outer edge.

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