MEMS device

Abstract

This MEMS device (1) comprises a first lid substrate (40), device substrates (10, 20), and a second lid substrate (30) laminated in this order, and detects the capacitance formed by the device substrates (10, 20), wherein: the first lid substrate (40) includes a conductive part (Q10), and an insulating part (Q11) that electrically insulates the conductive part (Q10); the first lid substrate (40) includes a first metal layer (E1) and a second metal layer (E2) provided on the surface facing the device substrates (10, 20); the first metal layer (E1) is provided from the conductive part (Q10) to the insulating part (Q11); and the second metal layer (E2) is provided in at least a part of a region covering a boundary part (QB) between the conductive part (Q10) and the insulating part (Q11), at the device substrate (10, 20) side of the first metal layer (E1).

Description

MEMS device

[0001] The present invention relates to a MEMS device.

[0002] MEMS (Micro Electro Mechanical Systems) devices manufactured using MEMS technology are widespread. MEMS devices are applied, for example, to inertial sensors that detect acceleration and angular velocity based on changes in capacitance. For the purpose of improving the performance of MEMS devices, a structure in which MEMS structures are multilayered has been proposed.

[0003] For example, Patent Document 1 discloses a physical quantity sensor including a first substrate and a second substrate bonded to face the first substrate, an airtight chamber being formed between the first substrate and the second substrate, a sensing unit that outputs a sensor signal corresponding to a physical quantity being disposed in the airtight chamber, and a first substrate pad portion of the first substrate and a second substrate pad portion of the second substrate being metallically bonded.

[0004] Japanese Patent Application Laid-Open No. 2014-232090

[0005] However, in the physical quantity sensor described in Patent Document 1, if the thickness of the first substrate pad portion is small, disconnection may occur due to a step on the surface of the first substrate, resulting in a conduction failure. If the thickness of the first substrate pad portion is large, the manufacturing error of the sensor signal output from the sensing unit may increase due to variations in the gap in the thickness direction of the airtight chamber. Thus, the reliability may be impaired depending on the thickness of the first substrate pad portion.

[0006] The present invention has been made in view of such circumstances, and an object of the present invention is to provide a MEMS device capable of improving reliability.

[0007] A MEMS device according to one aspect of the present invention is a MEMS device in which a first cover substrate, a device substrate, and a second cover substrate are stacked in this order, and the capacitance formed by the device substrate is detected, wherein the first cover substrate has a conductive portion and an insulating portion that electrically insulates the conductive portion, and the first cover substrate has a first metal layer and a second metal layer provided on the surface facing the device substrate, the first metal layer is provided extending from the conductive portion to the insulating portion, and the second metal layer is provided on the device substrate side of the first metal layer, in at least a part of the region covering the boundary between the conductive portion and the insulating portion.

[0008] Another embodiment of the present invention is a MEMS device in which a first lid substrate, a device substrate, and a second lid substrate are stacked in this order, and the MEMS device detects the capacitance formed by the device substrate, wherein the device substrate has a movable portion configured to move away from the first lid substrate and a support portion that abuts the first lid substrate and supports the movable portion, the first lid substrate has a first metal layer and a second metal layer provided on the surface facing the device substrate, the first metal layer abuts a part of the support portion, and the second metal layer is provided on the device substrate side of the first metal layer and abuts a part of the support portion.

[0009] According to the present invention, it is possible to provide a MEMS device that can improve reliability.

[0010] This is a cross-sectional view of the MEMS device according to the first embodiment. This is an enlarged cross-sectional view of the MEMS device according to the first embodiment. This is a cross-sectional view of the MEMS device according to the second embodiment. This is an enlarged third embodiment.

[0011] Embodiments of the present invention will be described below with reference to the drawings. The drawings of this embodiment are illustrative, and the dimensions and shapes of each part are schematic; the technical scope of the present invention should not be limited to this embodiment.

[0012] <First Embodiment> First, the configuration of the MEMS device 1 according to the first embodiment of the present invention will be described with reference to Figures 1 and 2. Figure 1 is a cross-sectional view of the MEMS device 1 according to the first embodiment. Figure 2 is an enlarged cross-sectional view of the MEMS device 1 according to the first embodiment.

[0013] The following describes the various components of the MEMS device 1. Each drawing may, for convenience, include a Cartesian coordinate system consisting of the X, Y, and Z axes to clarify the relationships between the drawings and to help understand the positional relationships of each component. The directions parallel to the X, Y, and Z axes are referred to as the X-axis direction, Y-axis direction, and Z-axis direction, respectively. The plane defined by the X and Y axes is referred to as the XY plane. For convenience, the positive Z-axis direction (direction of the arrow) is described as up or upward, and the negative Z-axis direction (opposite direction of the arrow) is described as down or downward; however, the orientation of the MEMS device 1 is not limited to these. In the following description, the Z-axis direction is referred to as the thickness direction, height direction, and depth direction, and the X-axis direction is referred to as the width direction.

[0014] MEMS device 1 is a device manufactured using MEMS technology. MEMS device 1 comprises a first device substrate 10, a second device substrate 20, a first cover substrate 40, a second cover substrate 30, and a bonding member 50. MEMS device 1 is a capacitive sensor that detects, for example, inertial forces (e.g., acceleration and angular velocity) and pressure in the X, Y, and Z axis directions by detecting the capacitance formed by the first device substrate 10. The first cover substrate 40, the first device substrate 10, the second device substrate 20, and the second cover substrate 30 are stacked in this order in the Z axis direction. The first cover substrate 40 is bonded to the first device substrate 10 by the bonding member 50, the first device substrate 10 is directly bonded to the second device substrate 20, and the second device substrate 20 is directly bonded to the second cover substrate 30. The first lid substrate 40 and the second lid substrate 30 constitute a package structure that forms a movable space inside which the first device substrate 10 and the second device substrate 20 move. The first device substrate 10 and the second device substrate 20 are collectively referred to simply as "device substrates".

[0015] The first device substrate 10 is provided by a silicon substrate F10. The silicon substrate F10 is formed from a silicon single crystal. The silicon substrate F10 is formed from, for example, a p-type silicon (Si) semiconductor. The silicon substrate F10 may contain boron (B) as a p-type dopant. The resistance of the silicon (Si) used in the silicon substrate F10 is, for example, about 10 mΩ·cm.

[0016] As shown in Figure 1, the first device substrate 10 includes movable parts 12A and 12B, bonding parts 14B and 14C, support parts 17 and 18, and peripheral parts 19. The movable parts 12A and 12B, bonding parts 14B and 14C, support parts 17 and 18, and peripheral parts 19 are formed by patterning the silicon substrate F10 by a removal process. This removal process is carried out, for example, by dry etching called deep reactive ion etching (DRIE). This removal process may also be carried out by other methods such as wet etching and laser etching.

[0017] A movable space 11A is provided between the first lid substrate 40 and the movable parts 12A and 12B. A movable space 11B is provided between the second device substrate 20 and the movable parts 12A and 12B. In other words, the movable parts 12A and 12B are separated from both the first lid substrate 40 and the second device substrate 20. The movable space 11A is formed by a cavity formed on the side of the first device substrate 10 facing the first lid substrate 40. The movable space 11B is formed by a cavity formed on the side of the first device substrate 10 facing the second device substrate 20. A portion of the silicon substrate F10 around the movable parts 12A and 12B is separated from the rest by a slit that penetrates in the Z-axis direction. As a result, the movable parts 12A and 12B are configured to be movable.

[0018] The cavities of the first device substrate 10 that constitute the movable spaces 11A and 11B are formed, for example, by locally thermally oxidizing the silicon substrate F10 (LOCOS: Local Oxidation of Silicon) and removing the thermally oxidized region. However, the method for forming the cavities of the first device substrate 10 is not limited to the above, and may be carried out by methods such as dry etching, wet etching, or laser etching of the silicon substrate F10.

[0019] The movable part 12A is an electrode and weight for detecting inertial force and pressure in the Z-axis direction. The movable part 12A forms a capacitance with the first lid substrate 40. The movable part 12A may also form a capacitance with the second device substrate 20. When the MEMS device 1 is subjected to inertial force and pressure in the Z-axis direction, the movable part 12A is displaced in the Z-axis direction, and the gap in the movable spaces 11A and 11B in the Z-axis direction changes. Based on the change in the gap in the movable spaces 11A and 11B, the capacitance formed between the movable part 12A and the first lid substrate 40 changes. Also, if a capacitance is formed between the movable part 12A and the second device substrate 20, the capacitance formed between the movable part 12A and the second device substrate 20 also changes. By detecting the change in capacitance formed by the movable part 12A, the inertial force in the Z-axis direction that the MEMS device 1 is subjected to can be detected.

[0020] The movable part 12B is an electrode and weight for detecting inertial force and pressure in the X-axis direction. Multiple movable parts 12B are arranged at intervals in the X-axis direction, forming capacitance between them. When the MEMS device 1 is subjected to inertial force or pressure in the X-axis direction, the movable parts 12B are displaced in the X-axis direction. At this time, the ease with which adjacent movable parts 12B are displaced differs, and the distance between adjacent movable parts 12B changes. Based on this change in distance, the capacitance formed by the movable parts 12B changes. By detecting this change in capacitance, the inertial force and pressure in the X-axis direction that the MEMS device 1 is subjected to can be detected.

[0021] Although not shown in the diagram, the MEMS device 1 further includes a movable part (hereinafter referred to as the "Y-axis movable part") which is both an electrode and a weight for detecting inertial force and pressure in the Y-axis direction. Multiple Y-axis movable parts are arranged at intervals in the Y-axis direction, forming capacitance between them. The MEMS device 1 detects the inertial force and pressure in the Y-axis direction acting on the MEMS device 1 by detecting the change in capacitance formed by the Y-axis movable parts that have been displaced in the Y-axis direction.

[0022] Joint 14B is joined to the second device substrate 20 and connects the movable part 12B to the second device substrate 20. Joint 14C is joined to the second device substrate 20 and connects the Y-axis movable part to the second device substrate 20. Joint 14B is joined to joint 24B of the second device substrate 20, which will be described later, and joint 14C is joined to joint 24C of the second device substrate 20, which will be described later. The joining of joint 14B to joint 24B and joint 14C to joint 24C is a direct joining of single-crystal silicon (silicon substrate F10 and silicon substrate F20). Joints 14B and 14C are separated from the first lid substrate 40 by the movable space 11A. This suppresses the propagation of stress from the first lid substrate 40 to the movable parts 12B and 12C via joints 14B and 14C.

[0023] The support portion 18 abuts against the first lid substrate 40 and supports the movable portion 12A of the first device substrate 10. The support portion 18 is joined to the support portion 28 of the second device substrate 20, which will be described later. The joining of the support portion 18 and the support portion 28 is a direct joining of single-crystal silicon (silicon substrate F10 and silicon substrate F20). The support portion 18 and the support portion 28 are sandwiched between the first lid substrate 40 and the second lid substrate 30. The support portion 18 has a protrusion 18p that projects toward the first lid substrate 40. The width of the protrusion 18p in the X-axis direction decreases as it approaches the first lid substrate 40.

[0024] The support portion 17 abuts against the first lid substrate 40 and supports the movable portion 12B of the first device substrate 10. The support portion 17 is joined to the support portion 27 of the second device substrate 20, which will be described later. The joining of the support portion 18 and the support portion 28 is a direct joining of single-crystal silicon (silicon substrate F10 and silicon substrate F20). The support portion 17 has a protrusion 17p that projects toward the first lid substrate 40. The width of the protrusion 17p in the X-axis direction decreases as it approaches the first lid substrate 40.

[0025] The protrusions 18p and 17p are formed, for example, by locally thermally oxidizing the silicon substrate F10 (LOCOS: Local Oxidation of Silicon) and removing the thermally oxidized region. Specifically, the silicon substrate F10 is thermally oxidized with a mask containing a silicon nitride film placed in the region that will be the contact surface of the protrusions 18p and 17p, and the thermally oxidized region and the mask are removed. This forms the protrusions 18p and 17p having sides with continuously changing inclination.

[0026] The heights of the protrusions 18p and 17p are greater than the respective thicknesses of the first metal layer E1 and the second metal layer E2, as described later. Preferably, the heights of the protrusions 18p and 17p are 10 times or more the thickness of the first metal layer E1, more preferably 20 times or more the thickness of the first metal layer E1, and even more preferably 50 times or more the thickness of the first metal layer E1. Preferably, the heights of the protrusions 18p and 17p are 500 times or less the thickness of the first metal layer E1, more preferably 250 times or less the thickness of the first metal layer E1, and even more preferably 100 times or less the thickness of the first metal layer E1. Preferably, the heights of the protrusions 18p and 17p are 2 times or more the thickness of the second metal layer E2, more preferably 5 times or more the thickness of the second metal layer E2, and even more preferably 10 times or more the thickness of the second metal layer E2. The heights of the protrusions 18p and 17p are preferably 100 times or less the thickness of the second metal layer E2, more preferably 50 times or less the thickness of the second metal layer E2, and even more preferably 25 times or less the thickness of the second metal layer E2. The heights of the protrusions 18p and 17p are, for example, greater than the sum of the thicknesses of the first metal layer E1 and the second metal layer E2, but may be equal to or less than the sum of the thicknesses of the first metal layer E1 and the second metal layer E2.

[0027] The heights of the protrusions 18p and 17p are specified, for example, as the dimension in the Z-axis direction from the upper surface of the movable parts 12A and 12B facing the first lid substrate 40 to the contact surface of the protrusions 18p and 17p that abuts the first metal layer E1. The heights of the protrusions 18p and 17p correspond to the size of the spacing in the Z-axis direction of the movable space 11A. The thickness of the first metal layer E1 is specified as the dimension in the Z-axis direction of the portion of the first metal layer E1 that does not abut the protrusions 18p and 17p, for example, the portion facing the movable part 12A. The thickness of the second metal layer E2 is specified as the dimension in the Z-axis direction of the portion of the second metal layer E2 that faces the first device substrate 10 with a gap between them, for example, the portion provided in the region covering the boundary portion QB described later.

[0028] The peripheral portion 19 is provided in a frame shape along the outer edge of the first device substrate 10. When viewed in plan in the Z-axis direction (hereinafter simply referred to as "plan view"), the peripheral portion 19 surrounds the movable portions 12A, 12B, joining portions 14B, 14C and support portions 18, 17 of the first device substrate 10. The peripheral portion 19 is joined to the glass substrate portion Q11 of the first lid substrate 40, which will be described later, and is joined to the peripheral portion 29 of the second device substrate 20, which will be described later. The joining of the peripheral portion 19 and the peripheral portion 29 is a direct joining of single-crystal silicon (silicon substrate F10 and silicon substrate F20).

[0029] The second device substrate 20 is provided by a silicon substrate F20. The silicon substrate F20 is formed from a silicon single crystal. The silicon substrate F20 is formed from, for example, a p-type silicon (Si) semiconductor. The silicon substrate F20 may contain boron (B) as a p-type dopant. The resistance of the silicon (Si) used in the silicon substrate F20 is, for example, about 10 mΩ·cm.

[0030] The second device substrate 20 comprises bonding portions 24B and 24C, support portions 28 and 27, and a peripheral portion 29. The bonding portions 24B and 24C, support portions 28 and 27, and peripheral portion 29 are formed by patterning the silicon substrate F20 by a material removal process. This material removal process is carried out by, for example, DRI (Dry Removal Etching), but is not limited to this, and may be carried out by other methods such as wet etching or laser etching.

[0031] A movable space 21 is provided between the regions of the second device substrate 20 corresponding to the movable parts 12A, 12B and the joint parts 14B, 14C, and the second lid substrate 30. In other words, the regions of the second device substrate 20 corresponding to the movable parts 12A, 12B and the joint parts 14B, 14C are separated from the second lid substrate 30. The movable space 21 is formed by a cavity formed on the side of the second device substrate 20 facing the second lid substrate 30. The depth of the cavity is, for example, 1 μm to 50 μm, and preferably 10 μm to 40 μm. The movable space 21 suppresses the propagation of stress from the second lid substrate 30 to the movable parts 12A, 12B.

[0032] The cavity of the second device substrate 20 that constitutes the movable space 21 is formed in at least a portion of the region corresponding to the movable parts 12A and 12B on the side of the second device substrate 20 facing the second lid substrate 30. The cavity is formed, for example, by removing the silicon substrate F20 by perpendicular anisotropic reactive ion etching. However, the method of forming the cavity of the second device substrate 20 is not limited to the above, and may be carried out by methods such as wet etching or laser etching of the silicon substrate F20. The cavity of the second device substrate 20 may also be formed by a method of locally thermally oxidizing the silicon substrate F20 and removing the thermally oxidized region.

[0033] Joint portion 24B is joined to joint portion 14B of the first device substrate 10. Joint portion 24C is joined to joint portion 14C of the first device substrate 10. A movable space 21 exists between the joint portions 24B, 24C and the second lid substrate 30, and the joint portions 24B, 24C are separated from the second lid substrate 30.

[0034] Support portion 28 supports joint portions 24B, 24C, etc. Support portion 28 is directly bonded to the silicon oxide film P11 of the second lid substrate 30, which will be described later. Support portion 27 supports joint portions 24B, etc. Support portion 27 is spaced apart from the second lid substrate 30.

[0035] The peripheral portion 29 is provided in a frame shape along the outer edge of the second device substrate 20. When viewed from above, the peripheral portion 29 surrounds the bonding portions 24B, 24C and the support portions 28, 27. The peripheral portion 29 is bonded to the peripheral portion 19 of the first device substrate 10 and to the second lid substrate 30. The bonding between the peripheral portion 29 and the second lid substrate 30 is, for example, a direct bonding between the single-crystal silicon (silicon substrate F20) of the peripheral portion 29 and the silicon oxide (silicon oxide film P11, described later) of the second lid substrate 30.

[0036] The first cover substrate 40 has a composite substrate QP, a first metal layer E1, a second metal layer E2, and an external terminal TT.

[0037] The composite substrate QP is provided in a flat plate shape. The composite substrate QP is formed by a silicon substrate portion Q10 and a glass substrate portion Q11 combined in the XY plane. The silicon substrate portion Q10 is formed of, for example, a p-type silicon (Si) semiconductor. The resistance value of the silicon (Si) used in the silicon substrate portion Q10 is, for example, about 10 mΩ·cm. The glass substrate portion Q11 is made of silicon oxide (for example, SiO ２ It is formed from silicate glass whose main component is ). Here, the main component in glass refers to the component that accounts for 50% or more by mass of all components constituting the glass. The silicon substrate portion Q10 is provided in multiple regions that are spaced apart from each other in the XY plane direction. The silicon substrate portion Q10 is provided so as to penetrate the composite substrate QP in the Z axis direction. The silicon substrate portion Q10 electrically connects the first metal layer E1 provided on the Z-axis negative side surface of the first device substrate 10 and the external terminal TT provided on the positive axis negative side surface of the first device substrate 10. The glass substrate portion Q11 electrically insulates the multiple silicon substrate portions Q10 from each other. The silicon substrate portion Q10 is an example of a "conductive portion", and the glass substrate portion Q11 is an example of an "insulating portion".

[0038] The composite substrate QP has a boundary portion QB between the silicon substrate portion Q10 and the glass substrate portion Q11 on the surface facing the first device substrate 10. The surface of the glass substrate portion Q11 facing the first device substrate 10 protrudes towards the first device substrate 10 compared to the surface of the silicon substrate portion Q10 facing the first device substrate 10. That is, a step is formed at the boundary portion QB of the composite substrate QP. Such a step is formed by polishing the composite substrate QP. Since the abrasion resistance of the glass substrate portion Q11 is higher than that of the silicon substrate portion Q10, the polishing speed of the silicon substrate portion Q10 is greater than that of the glass substrate portion Q11. Therefore, a step is formed at the boundary portion QB due to the difference in processing speed.

[0039] The shape of the composite substrate QP is not limited to a flat plate; a cavity may be formed on the side of the composite substrate QP facing the first device substrate 10. Furthermore, the materials of the conductive and insulating parts of the composite substrate QP are not limited to those described above. The conductive part may be, for example, an n-type silicon semiconductor, or a compound semiconductor or oxide semiconductor other than a silicon semiconductor. The insulating part may be, for example, a silicon oxide, silicon nitride, silicon oxynitride, or an insulator other than a silicon compound.

[0040] A first metal layer E1 and a second metal layer E2 are provided on the surface of the first lid substrate 40 facing the first device substrate 10.

[0041] The first metal layer E1 is an internal wiring that electrically connects the silicon substrate portion Q10 of the first lid substrate 40 and the silicon substrate F10 of the first device substrate 10. Also, the first metal layer E1 is an electrode that forms a capacitance with the movable portion 12A. The first metal layer E1 is provided across the silicon substrate portion Q10 and the glass substrate portion Q11 so as to cross the boundary portion QB. The first metal layer E1 covers the silicon substrate portion Q10, whereby the first metal layer E1 and the silicon substrate portion Q10 are electrically connected. The first metal layer E1 abuts on the surface of the tip of the convex portion 18p of the support portion 18 (hereinafter referred to as the "abutment surface"), whereby the first metal layer E1 and the support portion 18 are electrically connected. Also, the first metal layer E1 abuts on the abutment surface of the convex portion 17p of the support portion 17, whereby the first metal layer E1 and the support portion 17 are electrically connected.

[0042] The thickness of the first metal layer E1 is, for example, smaller than the height of the step of the boundary portion QB, but may be equal to or greater than the height of the step of the boundary portion QB. The thickness of the first metal layer E1 is, for example, 10 nm or more and 100 nm or less. The first metal layer E1 has, for example, a single-layer structure mainly composed of aluminum (Al), but may have a multilayer structure including a layer mainly composed of aluminum (Al) and a layer mainly composed of titanium (Ti). The first metal layer E1 may have a single-layer structure or a multilayer structure including a layer mainly composed of a metal other than aluminum and titanium. The first metal layer E1 may contain, for example, gold (Au), silver (Ag), copper (Cu), lead (Pb), tin (Sn), zinc (Zn), platinum (Pt), palladium (Pd), indium (In), germanium (Ge), silicon (Si), etc.

[0043] The second metal layer E2 reinforces the electrical connection between the first metal layer E1 on the silicon substrate portion Q10 and the first metal layer E1 on the glass substrate portion Q11 in the region covering the boundary portion QB. The second metal layer E2 is provided across the silicon substrate portion Q10 and the glass substrate portion Q11 so as to cross the boundary portion QB. The second metal layer E2 is provided in at least a part of the region covering the boundary portion QB, but it is desirable that the second metal layer E2 is provided in the entire region covering the boundary portion QB.

[0044] The sum of the thicknesses of the first metal layer E1 and the second metal layer E2 is greater than the height of the step at the boundary QB. It is desirable that the thickness of the second metal layer E2 is greater than the height of the step at the boundary QB. The thickness of the second metal layer E2 is greater than the thickness of the first metal layer E1, preferably at least twice the thickness of the first metal layer E1, more preferably at least five times the thickness of the first metal layer E1, and even more preferably at least ten times the thickness of the first metal layer E1. The thickness of the second metal layer E2 is, for example, 100 nm to 2000 nm. The second metal layer E2 is a multilayer structure including, for example, a layer mainly composed of aluminum and a layer mainly composed of titanium, but it may also be a single-layer structure mainly composed of aluminum. The second metal layer E2 may be a single-layer or multilayer structure including a layer mainly composed of a metal other than aluminum and titanium. The second metal layer E2 may contain, for example, gold (Au), silver (Ag), copper (Cu), lead (Pb), tin (Sn), zinc (Zn), platinum (Pt), palladium (Pd), indium (In), germanium (Ge), silicon (Si), etc.

[0045] The second metal layer E2 may be provided over substantially the entire region facing the movable part 12A in order to improve the detection accuracy of the change in capacitance formed by the movable part 12A. Alternatively, the second metal layer E2 may be provided in a part of the region facing the movable parts 12A and 12B as an obstacle to prevent the movable parts 12A and 12B from sticking to the first lid substrate 40. When the second metal layer E2 is provided as an obstacle to prevent the movable part 12B from sticking, the second metal layer E2 may be provided directly on the glass substrate portion Q11 of the composite substrate QP without going through the first metal layer E1.

[0046] The external terminal TT is a terminal for electrically connecting the MEMS device 1 to an external circuit. The external terminal TT is provided on the side of the first cover substrate 40 opposite to the side facing the first device substrate 10. The external terminal TT is provided on the silicon substrate portion Q10 of the composite substrate QP. The external terminal TT is electrically connected to the first device substrate 10 via the silicon substrate portion Q10 and the first metal layer E1.

[0047] The joining member 50 joins the first device substrate 10 and the first lid substrate 40. Specifically, the joining member 50 joins the silicon substrate F10 of the first device substrate 10 and the glass substrate portion Q11 of the first lid substrate 40. The joining member 50 is provided in a frame shape so as to surround the movable space 11A.

[0048] The joining member 50 has a silicon oxide film 51 and a eutectic alloy layer 52. The silicon oxide film 51 is provided between the silicon substrate F10 and the eutectic alloy layer 52. The silicon oxide film 51 suppresses the diffusion of the metal elements constituting the eutectic alloy layer 52 into the silicon substrate F10 and improves the joining strength of the joining member 50. The silicon oxide film 51 is provided by a silicon oxide (for example, SiO ２ ). The eutectic alloy layer 52 eutectically joins the silicon oxide film 51 and the glass substrate portion Q11. The eutectic alloy layer 52 contains at least one of the metal materials constituting the first metal layer E1 and the second metal layer E2. The eutectic alloy layer 52 is provided by, for example, a eutectic alloy of the aluminum-germanium-titanium (Al-Ge-Ti) system.

[0049] The second lid substrate 30 is provided by a silicon substrate P10 and a silicon oxide film P11. The silicon substrate P10 is provided in a flat plate shape, and the side of the silicon substrate P10 facing the second device substrate 20 is provided in a planar shape. The silicon oxide film P11 is provided on the surface of the second lid substrate 30 that joins the second device substrate 20. That is, the silicon substrate P10 of the second lid substrate 30 is directly joined to the silicon substrate F20 of the second device substrate 20 via the silicon oxide film P11. The silicon substrate P10 is formed of, for example, a single crystal of silicon. The silicon substrate P10 corresponds to an example of a handle substrate. Note that the handle substrate is not limited to a single crystal silicon substrate and may be a semiconductor substrate, a ceramic substrate, a glass substrate, or the like.

[0050] As described above, in the MEMS device 1, the first lid substrate 40, the first device substrate 10, the second device substrate 20, and the second lid substrate 30 are stacked in this order. The first lid substrate 40 has a first metal layer E1 and a second metal layer E2 provided on the surface facing the first device substrate 10. The first metal layer E1 is provided extending from the silicon substrate portion Q10 to the glass substrate portion Q11 so as to extend beyond the boundary portion QB, and the second metal layer E2 is provided on the first device substrate 10 side of the first metal layer E1 and in at least a part of the region that covers the boundary portion QB.

[0051] According to this, the electrical connection of the first metal layer E1 at the step in the boundary QB can be reinforced by the second metal layer E2, thereby suppressing the occurrence of electrical connection failures due to step breaks caused by the step in the boundary QB. Furthermore, since the first metal layer E1 can be made thinner without worrying about step breaks at the boundary QB, variations in the indentation depth of the support parts 18 and 17 into the first metal layer E1 can be reduced. As a result, the manufacturing error in the distance between the movable part 12A of the first device substrate 10 and the first metal layer E1 of the first lid substrate 40 can be reduced, and the manufacturing error in capacitance in the Z-axis direction can be reduced. Therefore, the reliability of the MEMS device 1 can be improved.

[0052] In one embodiment described above, the thickness of the second metal layer E2 is greater than the thickness of the first metal layer E1.

[0053] According to this, it is possible to more efficiently suppress the occurrence of electrical connection failures caused by step breaks resulting from the step difference in the boundary QB.

[0054] In one embodiment described above, the thickness of the first metal layer E1 is smaller than the step difference of the boundary QB.

[0055] According to this, variations in the indentation depth of the support parts 18 and 17 into the first metal layer E1 can be further reduced, and manufacturing errors in capacitance in the Z-axis direction can be reduced.

[0056] In one embodiment described above, the support portions 18 and 17 have protrusions 18p and 17p formed by partially thermally oxidizing a silicon substrate F10, which is a single-crystal silicon substrate, and removing the thermally oxidized region.

[0057] According to this, the heights of the protrusions 18p and 17p can be set with high precision, thereby reducing the manufacturing error in the distance between the movable part 12A of the first device substrate 10 and the first metal layer E1 of the first lid substrate 40, and thus reducing the manufacturing error in capacitance in the Z-axis direction.

[0058] In one embodiment described above, the height of the protrusions 18p and 17p of the support parts 18 and 17 is 10 to 100 times the thickness of the first metal layer E1.

[0059] According to this, by making the height of the protrusions 18p and 17p 10 times or more the thickness of the first metal layer E1, unwanted contact between the first device substrate 10 and the second metal layer E2 can be suppressed. In addition, by widening the range of motion of the movable part 12A in the Z-axis direction, the detection range of capacitance changes can be widened. By making the height of the protrusions 18p and 17p 100 times or less the thickness of the first metal layer E1, the height increase of the MEMS device 1 can be suppressed. Furthermore, by limiting the range of motion of the movable parts 12A and 12B in the Z-axis direction, damage due to excessive displacement of the movable parts 12A and 12B when the MEMS device 1 is subjected to impact such as dropping can be suppressed.

[0060] In one embodiment described above, the MEMS device 1 includes a first device substrate 10 and a second device substrate 20.

[0061] According to this, since the MEMS structure is a two-layer structure consisting of a first device substrate 10 and a second device substrate 20, the design freedom of the MEMS structure can be improved compared to the case where the MEMS structure is a single-layer structure, and the performance of the MEMS device 1 can be improved by miniaturizing and increasing the density of the MEMS structure.

[0062] In one embodiment described above, the joining member 50 includes a eutectic alloy layer 52 containing at least one of the metallic materials that constitute the first metal layer E1 and the second metal layer E2.

[0063] According to this, at least a portion of the process of providing the first metal layer E1 and the second metal layer E2 can be shared with at least a portion of the process of providing the eutectic alloy layer 52. Therefore, the manufacturing process of the MEMS device 1 can be streamlined.

[0064] Other embodiments are described below. Components identical or similar to those shown in the first embodiment are denoted by the same or similar reference numerals, and their descriptions are omitted as appropriate. Furthermore, similar effects and benefits from similar components are not mentioned sequentially.

[0065] <Second Embodiment> Next, the configuration of the MEMS device 2 according to the second embodiment of the present invention will be described with reference to Figures 3 and 4. Figure 3 is a cross-sectional view of the MEMS device 2 according to the second embodiment. Figure 4 is an enlarged cross-sectional view of the MEMS device 2 according to the second embodiment.

[0066] The second metal layer E2 is provided in a part of the region between the protrusions 18p and 17p of the support parts 18 and 17 and the first metal layer E1, and is in contact with a part of the contact surface of the support parts 18 and 17. The protrusions 18p and 17p are in contact with the second metal layer E2 while also in contact with the first metal layer E1. As a result, the protrusions 18p and 17p are positioned by contacting the first metal layer E1, and by providing the first metal layer E1 thinly, the manufacturing error in the distance between the movable part 12A of the first device substrate 10 and the first metal layer E1 of the first lid substrate 40 can be reduced, and the manufacturing error in capacitance in the Z-axis direction can be reduced.

[0067] As shown in Figure 4, a slit is provided in the convex portion 18p of the support portion 18 from the contact surface, and the second metal layer E2 penetrates into the interior of the slit. A slit is similarly provided in the convex portion 17p of the support portion 17. This makes it possible to reduce contact resistance by increasing the area of ​​the portion that provides electrical connection between the first device substrate 10 and the first lid substrate 40.

[0068] Of the contact surfaces of the support portion 18, the area of ​​the region that contacts the second metal layer E2 is smaller than the area of ​​the region that contacts the first metal layer E1. As a result, the support portions 18 and 17 can be brought into contact with the first metal layer E1 without their positions being restricted by the second metal layer E2. Therefore, the manufacturing error in the distance between the movable portion 12A of the first device substrate 10 and the first metal layer E1 of the first lid substrate 40 can be further reduced.

[0069] The second metal layer E2 is in contact with at least a portion of the outer edge of the contact surface of the support parts 18 and 17. As a result, stress concentrates in the portion of the first metal layer E1 that is in contact with the outer edge of the contact surface, making it prone to disconnection. However, by reinforcing the mechanical strength of this portion with the second metal layer E2, the occurrence of electrical connection failures can be suppressed. It is preferable that the second metal layer E2 is in contact with the entire outer edge of the contact surface of the support parts 18 and 17.

[0070] <Third Embodiment> Next, the configuration of the MEMS device 3 according to the third embodiment of the present invention will be described with reference to Figure 5. Figure 5 is an enlarged cross-sectional view of the MEMS device 3 according to the third embodiment.

[0071] The second metal layer E2 of the MEMS device 3 is provided in multiple island-like or linear shapes between the support portion 18 and the first metal layer E1. The same applies between the support portion 17 and the first metal layer E1. This arrangement allows the support portions 18 and 17 to contact parts of the second metal layer E2, which is provided in multiple island-like or linear shapes. Therefore, it is possible to suppress the occurrence of electrical connection failures caused by misalignment. The multiple island-like regions or multiple linear regions in the second metal layer E2 may be spaced apart from each other or may be continuous with each other.

[0072] The embodiments of the present invention are not particularly limited and can be appropriately applied to any sensor that detects changes in capacitance, such as an inertial sensor like an acceleration sensor or a gyroscope, or a pressure sensor.

[0073] As described above, according to one aspect of the present invention, a MEMS device capable of improving reliability can be provided.

[0074] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit its interpretation. The present invention can be modified or improved without departing from its spirit, and such modifications are also included. That is, any design changes made to each embodiment by a person skilled in the art are also included within the scope of the present invention, as long as they retain the features of the present invention. For example, the elements of each embodiment, their arrangement, materials, conditions, shapes, sizes, etc., are not limited to those exemplified and can be modified as appropriate. Furthermore, the elements of each embodiment can be combined to the extent that it is technically possible, and any combination thereof is also included within the scope of the present invention, as long as it retains the features of the present invention.

[0075] 1…MEMS device 10…First device substrate 11A, 11B…Movable space 12A, 12B…Movable part 14B, 14C…Joint part 18, 17…Support part 18p, 17p…Protrusion part 19…Peripheral part 20…Second device substrate 21…Movable space 24B, 24C…Joint part 28, 27…Support part 29…Peripheral part 40…First lid substrate 30…Second lid substrate 50…Joint member 51…Silicon oxide film 52…Eutectic alloy layer E1…First metal layer E2…Second metal layer P10, F10, F20…Silicon substrate P11…Silicon oxide film Q10…Silicon substrate part Q11…Glass substrate part

Claims

1. A MEMS device comprising a first cover substrate, a device substrate, and a second cover substrate stacked in this order, wherein the capacitance formed by the device substrate is detected, the first cover substrate having a conductive portion and an insulating portion that electrically insulates the conductive portion, the first cover substrate having a first metal layer and a second metal layer provided on the surface facing the device substrate, the first metal layer extending from the conductive portion to the insulating portion, and the second metal layer being provided on the device substrate side of the first metal layer, in at least a portion of the region covering the boundary between the conductive portion and the insulating portion.

2. The MEMS device according to claim 1, wherein the device substrate has a movable portion configured to move away from the first lid substrate and a support portion that abuts against the first lid substrate and supports the movable portion, the first metal layer abuts against a part of the support portion, and the second metal layer is provided on the device substrate side of the first metal layer and abuts against a part of the support portion.

3. A MEMS device in which a first lid substrate, a device substrate, and a second lid substrate are stacked in this order, and the capacitance formed by the device substrate is detected, wherein the device substrate has a movable portion configured to move away from the first lid substrate and a support portion that abuts against the first lid substrate and supports the movable portion, the first lid substrate has a first metal layer and a second metal layer provided on the surface facing the device substrate, the first metal layer abuts against a part of the support portion, and the second metal layer is provided on the device substrate side of the first metal layer and abuts against a part of the support portion.

4. The MEMS device according to claim 2 or 3, wherein the area of ​​the region of the support portion that contacts the second metal layer is smaller than the area of ​​the region of the support portion that contacts the first metal layer.

5. The MEMS device according to any one of claims 2 to 4, wherein the second metal layer is provided in a plurality of island-like or linear manner between the support portion and the first metal layer.

6. The MEMS device according to any one of claims 2 to 5, wherein the support portion has a contact surface that contacts the first lid substrate, and the second metal layer contacts at least a portion of the outer edge of the contact surface.

7. The MEMS device according to any one of claims 1 to 6, wherein the thickness of the second metal layer is greater than the thickness of the first metal layer.

8. The MEMS device according to any one of claims 1 to 7, wherein the first lid substrate has a conductive portion and an insulating portion that electrically insulates the conductive portion, and the thickness of the first metal layer is less than the step difference at the boundary between the conductive portion and the insulating portion.

9. The MEMS device according to any one of claims 1 to 8, wherein the thickness of the first metal layer is 10 nm or more and 100 nm or less.

10. The MEMS device according to any one of claims 1 to 9, wherein the thickness of the second metal layer is 100 nm or more and 2000 nm or less.

11. The MEMS device according to any one of claims 1 to 10, wherein the first lid substrate has a conductive portion and an insulating portion that electrically insulates the conductive portion, and the conductive portion is made of silicon.

12. The MEMS device according to any one of claims 1 to 11, wherein the first lid substrate has a conductive portion and an insulating portion that electrically insulates the conductive portion, and the insulating portion is made of silicate glass.

13. The MEMS device according to any one of claims 1 to 12, wherein the first metal layer is a single-layer structure mainly composed of aluminum, or a multilayer structure including a layer mainly composed of aluminum and a layer mainly composed of titanium.

14. The MEMS device according to any one of claims 1 to 13, wherein the second metal layer is a single-layer structure mainly composed of aluminum, or a multilayer structure including a layer mainly composed of aluminum and a layer mainly composed of titanium.

15. The MEMS device according to any one of claims 1 to 14, wherein the device substrate has a movable portion configured to move and a support portion that supports the movable portion, the device substrate has a single-crystal silicon substrate, and the support portion has a protrusion formed by partially thermally oxidizing the single-crystal silicon substrate and removing the thermally oxidized region.

16. The MEMS device according to any one of claims 1 to 15, wherein the device substrate has a movable part configured to move and a support part that supports the movable part, and the height of the protrusion of the support part is 10 times or more and 100 times or less the thickness of the first metal layer.

17. The MEMS device according to any one of claims 1 to 16, wherein the device substrate comprises a first device substrate provided on the side of the first lid substrate and a second device substrate provided between the first device substrate and the second lid substrate, the device substrate comprises a movable portion configured to be movable and a support portion that supports the movable portion, the movable portion of the first device substrate is spaced apart from both the first lid substrate and the second device substrate, and the support portion of the first device substrate is joined to the second device substrate and in contact with the first lid substrate.

18. A MEMS device according to any one of claims 1 to 17, further comprising a bonding member for bonding the first lid substrate and the device substrate, wherein the bonding member includes a eutectic alloy layer containing at least one of the metal materials constituting the first metal layer and the second metal layer.

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