MEMS device and manufacturing method therefor

Abstract

This MEMS device includes a first silicon substrate comprising a single crystal silicon, a second silicon substrate comprising a single crystal silicon, and a bonding layer that bonds the first silicon substrate and the second silicon substrate, wherein: the second silicon substrate includes a movable portion configured to be able to move away from the first silicon substrate, and a support portion that supports the movable portion; the bonding layer includes an anchor portion that bonds the support portion to the first silicon substrate; and the anchor portion is provided by a material having higher etching resistance than silicon oxide to an etchant for etching silicon oxide.

Description

MEMS device and method for manufacturing the same

[0001] The present invention relates to a MEMS device and a method for manufacturing the same.

[0002] MEMS devices manufactured using MEMS (Micro Electro Mechanical Systems) technology have become widespread. MEMS devices are applied to, for example, inertial sensors that detect acceleration and angular velocity based on changes in capacitance. Higher performance of MEMS devices through higher density, multi-layering and other approaches is being explored.

[0003] For example, Patent Document 1 discloses a MEMS device including a first silicon substrate provided with a cavity, a second silicon substrate provided with a movable portion, and a silicon oxide layer that bonds the first silicon substrate and the second silicon substrate.

[0004] U.S. Pat. No. 9,334,160

[0005] However, in the manufacturing of the MEMS device described in Patent Document 1, when removing an unnecessary portion of the silicon oxide layer, the portion bonding the first silicon substrate and the second silicon substrate is side-etched. The portion of the silicon oxide layer that bonds the first silicon substrate and the second silicon substrate is formed large to prevent it from being lost due to side etching. This may hinder the increase in density of MEMS devices in some cases.

[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 achieving higher density and a method for manufacturing the same.

[0007] A MEMS device according to one aspect of the present invention is a MEMS device having a first silicon substrate made of single crystal silicon, a second silicon substrate made of single crystal silicon, and a bonding layer that bonds the first silicon substrate and the second silicon substrate, wherein the second silicon substrate has a movable portion configured to be movable away from the first silicon substrate and a support portion that supports the movable portion, and the bonding layer has an anchor portion that bonds the support portion to the first silicon substrate, and the anchor portion is provided by a material that has higher etching resistance to an etchant that etches silicon oxide than silicon oxide.

[0008] A method for manufacturing a MEMS device according to another aspect of the present invention includes preparing a first silicon substrate made of single-crystal silicon, preparing a second silicon substrate made of single-crystal silicon, joining the first silicon substrate and the second silicon substrate with a bonding layer, providing a mask made of silicon oxide on the second silicon substrate and etching the second silicon substrate to provide a movable part and a support part, and removing the mask by etching, wherein the bonding layer has an anchor part that joins the support part to the first silicon substrate, and the anchor part is provided by a material that has higher etching resistance to an etchant that etches silicon oxide than silicon oxide.

[0009] According to the present invention, it is possible to provide a MEMS device that can achieve high density and a method for manufacturing the same.

[0010] This is a cross-sectional view of a MEMS device according to the first embodiment. This is a flowchart showing a method for manufacturing a MEMS device according to the first embodiment. This is a cross-sectional view showing the manufacturing process of a MEMS device according to the second embodiment. This is a cross-sectional view showing the manufacturing process of a MEMS device according to the second embodiment. This is a cross-sectional view showing the manufacturing process of a MEMS device according to the second embodiment. This is a cross-sectional view showing a MEMS device according to the third embodiment. This is a cross-sectional view of a MEMS device according to the fourth embodiment. This is a cross-sectional view of a MEMS device according to the fifth 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 Figure 1. Figure 1 is a cross-sectional view of the MEMS device 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 height direction, depth direction, and thickness direction.

[0014] MEMS device 1 is a device manufactured using MEMS technology. MEMS device 1 comprises a device substrate 10, a first lid substrate 30, a second lid substrate 40, a first bonding layer 50, and a second bonding layer 60. MEMS device 1 is a capacitive sensor that detects 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 device substrate 10. The first lid substrate 30, the first bonding layer 50, the device substrate 10, the second bonding layer 60, and the second lid substrate 40 are stacked in this order in the Z axis direction. The first lid substrate 30, the first bonding layer 50, the second bonding layer 60, and the second lid substrate 40 constitute a package structure that forms a movable space inside which the device substrate 10 moves.

[0015] The device substrate 10 comprises a silicon substrate F10 and a silicon oxide layer F11. 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. The silicon substrate F10 is an example of a second silicon substrate.

[0016] The silicon oxide layer F11 is provided on the second lid substrate 40 side of the silicon substrate F10. The silicon oxide layer F11 is SiO ２ It is formed of silicon oxide, which is the main component. The silicon oxide layer F11 is provided, for example, by thermal oxidation of the silicon substrate F10, but may also be provided by chemical vapor deposition (CVD).

[0017] As shown in Figure 1, the silicon substrate F10 of the device substrate 10 has movable parts 12A, 12B, support parts 17A, 17B, column part 18, and peripheral part 19. The multiple movable parts 12A, multiple movable parts 12B, support parts 17A, 17B, column part 18, and peripheral part 19 are provided by removing material from the silicon substrate F10. The removal of the silicon substrate F10 is carried out by dry etching, such as deep reactive ion etching (DRIE), but is not limited to this. The removal of the silicon substrate F10 may also be carried out by other methods such as wet etching or laser etching.

[0018] The movable parts 12A and 12B are configured to move away from the first lid substrate 30 and the second lid substrate 40. For example, movable part 12A is configured to move in the Z-axis direction, and movable part 12B is configured to move in the X-axis direction. The movable parts 12A and 12B are separated from the first lid substrate 30 by the thickness of the first bonding layer 50, and separated from the second lid substrate 40 by the thickness of the second bonding layer 60. That is, a movable space is formed between the movable parts 12A and 12B and the first lid substrate 30 by the first bonding layer 50, and a movable space is formed between the movable parts 12A and 12B and the second lid substrate 40 by the second bonding layer 60. The movable parts 12A and 12B are partially separated from the surrounding silicon substrate F10 by a slit that penetrates the silicon substrate F10 in the Z-axis direction. As a result, the movable parts 12A and 12B are configured to move.

[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 30, or with the second lid substrate 40. The movable part 12A may also form a capacitance with both the first lid substrate 30 and the second lid substrate 40. 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 capacitance formed by the movable part 12A changes. By detecting this change in capacitance, the inertial force and other forces in the Z-axis direction acting on the MEMS device 1 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. The multiple movable parts 12B are so-called comb-tooth electrodes. When the MEMS device 1 is subjected to inertial force and 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 may further include a movable part for detecting inertial force and pressure in the Y-axis direction. Such a movable part is, for example, a comb-shaped electrode composed of multiple movable parts arranged in the Y-axis direction. Similar to the movable part 12B, the inertial force and pressure in the Y-axis direction acting on the MEMS device 1 are detected by detecting changes in capacitance formed between the movable parts.

[0022] Support portion 17A supports the movable portion 12A. Support portion 17B supports the movable portion 12B. Support portions 17A and 17B are joined to the first lid substrate 30. This maintains the positions of the movable portions 12A and 12B relative to the first lid substrate 30 and the second lid substrate 40. Support portions 17A and 17B are spaced apart from the second lid substrate 40. This suppresses the transmission of stress from the second lid substrate 40 to the movable portions 12A and 12B.

[0023] The column portion 18 supports the entire device substrate 10. The column portion 18 is bonded to the first cover substrate 30 and the second cover substrate 40. This maintains the gap between the device substrate 10 and the first cover substrate 30, and the gap between the device substrate 10 and the second cover substrate 40. A silicon oxide layer F11 is provided on the side of the column portion 18 facing the second cover substrate 40. This silicon oxide layer F11 on the side of the column portion 18 facing the second cover substrate 40 has through holes that penetrate in the Z-axis direction. The silicon substrate F10 of the column portion 18 is electrically connected to the second bonding layer 60 through these through holes.

[0024] The peripheral portion 19 is a frame-shaped end along the outer edge of the device substrate 10 when viewed in plan in the Z-axis direction (hereinafter simply referred to as "plan view"). In the plan view, the peripheral portion 19 surrounds the movable parts 12A, 12B, the support parts 17A, 17B, and the column part 18. The peripheral portion 19 is bonded to the first cover substrate 30 and the second cover substrate 40. This maintains the gap between the device substrate 10 and the first cover substrate 30, and the gap between the device substrate 10 and the second cover substrate 40. A silicon oxide layer F11 is provided on the second cover substrate 40 side of the peripheral portion 19, and this silicon oxide layer F11 electrically insulates the peripheral portion 19 from the second bonding layer 60.

[0025] The first lid substrate 30 has a silicon substrate P10. The silicon substrate P10 is provided in a flat plate shape, and the side of the silicon substrate P10 facing the device substrate 10 is provided in a planar shape. The silicon substrate P10 is formed from a silicon single crystal. The resistance value of the silicon (Si) used in the silicon substrate P10 is, for example, about 10 mΩ·cm. The silicon substrate P10 is a so-called handle substrate. The silicon substrate P10 is an example of a first silicon substrate. The first lid substrate 30 may further have through electrodes penetrating the silicon substrate P10 in the Z-axis direction, or an insulating film covering the side of the silicon substrate P10 opposite to the side facing the device substrate 10.

[0026] The first bonding layer 50 bonds the device substrate 10 and the first lid substrate 30. The first bonding layer 50 has a polysilicon layer H11 and a silicon nitride layer H12. The silicon nitride layer H12 and the polysilicon layer H11 are formed on a silicon substrate F10 by chemical vapor deposition or the like. The polysilicon layer H11 is bonded to the silicon substrate P10. The bonding between the silicon substrate P10 and the polysilicon layer H11 is direct bonding. The silicon nitride layer H12 is bonded to the silicon substrate F10. The polysilicon layer H11 is made of polycrystalline silicon (polysilicon). The silicon nitride layer H12 is made of silicon nitride. The polysilicon layer H11 is an example of a silicon layer, but the silicon layer is not limited to a polysilicon layer. The silicon layer may be an amorphous silicon layer made of noncrystalline silicon (amorphous silicon). Since the silicon layer can be bonded to the silicon substrate using hydrophilic bonding, a type of direct bonding, using a silicon layer in the portion of the first bonding layer that contacts the silicon substrate P10 facilitates bonding between the first bonding layer 50 and the silicon substrate P10. The silicon nitride layer H12 is an example of an insulating layer, but the insulating layer is not limited to a silicon nitride layer. The insulating layer may be provided by an insulating material such as aluminum nitride, aluminum oxide, or silicon carbide.

[0027] Regarding etching resistance to vapor hydrofluoric acid (Vapor HF) and aqueous hydrofluoric acid (HF), which are etchants that etch silicon oxide, the first bonding layer 50 has higher etching resistance than silicon oxide. In other words, both the polysilicon layer H11 and the silicon nitride layer H12 are less susceptible to etching by vapor hydrofluoric acid and aqueous hydrofluoric acid than silicon oxide.

[0028] The first bonding layer 50 has an anchor portion AK and a peripheral bonding portion FL. The anchor portion AK bonds the support portions 17A, 17B and the column portion 18 to the silicon substrate P10. In a plan view, the anchor portion AK bonded to the support portion 17A is smaller than the support portion 17A, and the entire anchor portion AK overlaps the support portion 17A. The anchor portion AK bonded to the support portion 17A may be formed to be the same size as or larger than the support portion 17A. The same applies to the anchor portion AK bonded to the support portion 17B and the column portion 18. The peripheral bonding portion FL bonds the peripheral portion 19 of the silicon substrate F10 to the frame-shaped peripheral portion of the silicon substrate P10. In a plan view, the peripheral bonding portion FL is provided in a frame shape and seals the movable space of the movable portions 12A and 12B.

[0029] Furthermore, the structure of the first bonding layer is not limited to a two-layer structure consisting of a silicon layer and an insulating layer. The constituent material of the first bonding layer can be appropriately selected from materials that are less etchable than silicon oxide by gas-phase hydrofluoric acid or hydrofluoric acid aqueous solution. The first bonding layer may also be a single-layer structure or a multilayer structure of three or more layers. In addition, the structure of the first bonding layer may vary depending on the location. A change in structure here refers to changes such as switching between a multilayer structure and a single-layer structure depending on the location, or changes in constituent material depending on the location. For example, the layer structure of the anchor portion may differ from the layer structure of the surrounding joint portion, and the layer structure of the anchor portion joined to the movable portion may differ from the layer structure of the anchor portion joined to the column portion. Furthermore, the layer structure may change inside the surrounding joint portion or inside the anchor portion.

[0030] The second lid substrate 40 has a silicon substrate Q10 and a silicon oxide layer Q11. The silicon substrate Q10 is provided in a flat plate shape, and the side of the silicon substrate Q10 facing the device substrate 10 is provided in a planar shape. The silicon substrate Q10 is formed from, for example, a silicon single crystal. The resistance value of the silicon (Si) used in the silicon substrate Q10 is, for example, about 10 mΩ·cm. The silicon oxide layer Q11 is provided on the side of the silicon substrate Q10 facing the device substrate 10. The silicon oxide layer Q11 is SiO ２It is formed of silicon oxide, which is the main component. The thickness of the silicon oxide layer Q11 is greater than, for example, the thickness of the silicon oxide layer F11. The silicon oxide layer Q11 is formed by, for example, plasma CVD, which is easier to form in thickness than thermal oxidation, but the method of forming the silicon oxide layer Q11 is not limited to this.

[0031] The configuration of the second lid substrate is not limited to the above. The second lid substrate may, for example, have a glass substrate or a ceramic substrate. The second lid substrate may have a composite substrate in which silicon for electrical connections and glass for electrically insulating the silicon are arranged in an intricate manner.

[0032] The second bonding layer 60 bonds the device substrate 10 and the second lid substrate 40. The second bonding layer 60 is, for example, a eutectic alloy (AlGeTi) of aluminum (Al), germanium (Ge), and titanium (Ti). That is, the device substrate 10 and the second lid substrate 40 are eutectic bonded. The second bonding layer 60 electrically connects the silicon substrate Q10 and the columnar portion 18.

[0033] The composition of the second bonding layer is not limited to the above. The second bonding layer may be a eutectic alloy such as gold-tin eutectic alloy (AuSn) or gold-silicon eutectic alloy (AuSi). The second bonding layer may be provided by an organic adhesive containing epoxy, vinyl, acrylic, urethane, or silicone resins, or by a silicon-based adhesive containing water glass. The second bonding layer may be a low-melting-point glass (e.g., lead-borate or tin-phosphate). However, in order to electrically connect the silicon substrate of the device substrate and the silicon substrate of the second lid substrate, it is desirable that the second bonding layer be made of a conductive material.

[0034] Next, a method for manufacturing the MEMS device 1 according to the first embodiment will be described with reference to Figures 2 to 7. Figure 2 is a flowchart showing the method for manufacturing the MEMS device 1 according to the first embodiment. Figures 3 to 7 are cross-sectional views showing the manufacturing process of the MEMS device 1 according to the first embodiment.

[0035] First, the first and second silicon substrates are prepared (S10). From a single-crystal silicon ingot, a flat silicon substrate P10, which will be the first silicon substrate, and a flat silicon substrate F10, which will be the second silicon substrate, are cut out. The main surfaces of the silicon substrates F10 and P10 are polished to improve their flatness.

[0036] Next, the first silicon substrate and the second silicon substrate are joined (S20). Here, first, as shown in Figure 3, a first bonding layer 50 is provided on the silicon substrate F10. Specifically, a silicon nitride layer H12 is provided on the silicon substrate F10, and a polysilicon layer H11 is provided on the silicon nitride layer H12. Then, the silicon nitride layer H12 and the polysilicon layer H11 are etched to pattern the anchor portion AK and the peripheral bonding portion FL. Next, the silicon substrate F10 and the silicon substrate P10 are joined via the first bonding layer 50. Specifically, the polysilicon layer H11 and the silicon substrate P10 are joined by hydrophilic bonding.

[0037] Next, the second silicon substrate is thinned (S30). As shown in Figure 4, back grinding (BG) is performed on the side of the silicon substrate F10 opposite to the side facing the silicon substrate P10 to thin the silicon substrate F10. Chemical mechanical polishing (CMP) is also performed on the back-ground surface of the silicon substrate F10 to improve its flatness. During BG and CMP processing, pressure is applied to the silicon substrate F10 in the direction of the silicon substrate P10. At this time, the anchor portion AK supports the silicon substrate F10 and suppresses deformation, maintaining the gap between the silicon substrate F10 and the silicon substrate P10. Therefore, fluctuations in the thickness of the silicon substrate F10 due to BG and CMP processing are suppressed.

[0038] Next, the second silicon substrate is removed (S40). As shown in Figure 5, the silicon oxide layer F11 is provided on the side of the silicon substrate F10 opposite to the side facing the silicon substrate P10. A titanium (Ti) layer M11 is provided on the silicon oxide layer F11, and a germanium (Ge) layer M12 is provided on the titanium layer M11. The titanium layer M11 and the germanium layer M12 undergo a eutectic reaction with the aluminum (Al) layer in the process of bonding the second lid substrate 40 to the device substrate 10, which will be described later, to form the second bonding layer 60.

[0039] The titanium layer M11 and the germanium layer M12 are patterned by dry etching, wet etching, or lift-off etching. Through this patterning, the titanium layer M11 and the germanium layer M12 are provided in areas that overlap with the columnar portion 18 and peripheral portion 19 of the silicon substrate F10 in a plan view. The silicon oxide layer F11 is also patterned by dry etching or wet etching. Using the patterned silicon oxide layer F11 as a mask, the silicon substrate F10 is removed by dry etching. This removal process forms the movable portion 12A, 12B, the support portion 17A, 18B, the columnar portion 18, and the peripheral portion 19 of the silicon substrate F10.

[0040] Next, the mask is removed (S50). As shown in Figure 6, a portion of the silicon oxide layer F11 used as a mask is removed by etching with gaseous hydrofluoric acid or an aqueous hydrofluoric acid solution as the etchant. Specifically, the silicon oxide layer F11 on the movable parts 12A, 12B and the support parts 17A, 18B is removed, while a portion of the silicon oxide layer F11 on the column part 18 and the peripheral part 19 remains because it is covered by the titanium layer M11 and the germanium layer M12.

[0041] When etching the silicon oxide layer F11, the gaseous hydrofluoric acid or aqueous hydrofluoric acid solution, which is the etchant used to etch the silicon oxide layer F11, comes into contact with the silicon substrate F10. Furthermore, the etchant also comes into contact with the polysilicon layer H11 and the silicon nitride layer H12 through the gaps formed between the movable parts 12A, 12B, the support parts 17A, 18B, the column part 18, and the peripheral part 19. However, the polysilicon layer H11 and the silicon nitride layer H12 are made of materials with higher etching resistance to the etchant than the silicon oxide that constitutes the silicon oxide layer F11. Therefore, the silicon oxide layer F11 can be etched with almost no etching of the polysilicon layer H11 and the silicon nitride layer H12. In other words, the anchor part AK and the peripheral joint part FL provided by the polysilicon layer H11 and the silicon nitride layer H12 are less susceptible to side etching compared to the case where the anchor part and peripheral joint part have a silicon oxide layer.

[0042] Next, the second lid substrate is bonded to the device substrate (S60). As shown in Figure 7, the second lid substrate 40 is bonded to the device substrate 10 via the second bonding layer 60. The second bonding layer 60 bonds the silicon oxide layer F11 of the device substrate 10 to the silicon oxide layer Q11 of the second lid substrate 40. Since through holes are formed in the silicon oxide layer F11 near the center of the column portion 18, the second bonding layer 60 flows into the through holes. Therefore, it is electrically connected to the silicon substrate F10 through the through holes formed in the silicon oxide layer F11, and also electrically connected to the silicon substrate Q10 through the through holes formed in the silicon oxide layer Q11. The second bonding layer 60 is provided by sandwiching an aluminum (Al) layer formed on the silicon oxide layer Q11 and a germanium layer M12 and a titanium layer M11 formed on the silicon oxide layer F11 between the device substrate 10 and the second lid substrate 40, and heating and pressurizing them to form a eutectic alloy. Furthermore, the silicon substrate Q10 of the second cover substrate 40 bonded to the device substrate 10 may be subjected to BG processing or CMP processing.

[0043] As explained above, the MEMS device 1 includes a silicon substrate P10 made of single crystal silicon, a silicon substrate F10 made of single crystal silicon, and a first bonding layer 50 that bonds the silicon substrate P10 and the silicon substrate F10. The silicon substrate F10 includes movable parts 12A and 12B configured to be movable while being spaced apart from the silicon substrate P10, and support parts 17A and 17B that support the movable parts 12A and 12B. The first bonding layer 50 has an anchor part AK that bonds the support parts 17A and 17B to the silicon substrate P10, and the anchor part AK is formed of a material having higher etching resistance to an etchant for etching silicon oxide than silicon oxide.

[0044] Further, the method for manufacturing the MEMS device 1 includes: preparing silicon substrates P10 and F10 made of single crystal silicon; bonding the silicon substrate P10 and the silicon substrate F10 via the first bonding layer 50; providing a mask made of silicon oxide on the silicon substrate F10, etching the silicon substrate F10 to form the movable parts 12A, 12B and the support parts 17A, 17B; and removing the mask. The first bonding layer 50 has an anchor part AK that bonds the support parts 17A and 17B to the silicon substrate P10, and the anchor part AK is formed of a material having higher etching resistance to an etchant for etching silicon oxide than silicon oxide.

[0045] According to this configuration, since deformation of the silicon substrate F10 during BG processing or CMP processing is suppressed by the anchor part AK, the thickness accuracy of the silicon substrate F10 is improved. Since the anchor part AK is not side-etched, the anchor part AK can be designed to have a narrow width, and the support parts 17A, 17B and column parts 18 supported by the anchor part AK can also be designed to have a narrow width. Accordingly, the MEMS device 1 can be reduced in size and increased in density.

[0046] As one aspect of the above, the anchor part AK includes a silicon layer.

[0047] According to this configuration, the polysilicon layer H11 and the silicon substrate P10 can be bonded by hydrophilic bonding.

[0048] In one embodiment described above, the silicon layer is a polysilicon layer H11 made of polycrystalline silicon. The silicon layer may also be made of amorphous silicon.

[0049] According to this, the manufacturing process can be simplified compared to the case where the silicon layer is made of a single silicon crystal.

[0050] In one embodiment described above, the anchor portion AK includes an insulating layer.

[0051] According to this, the silicon substrate P10 and the silicon substrate F10 can be electrically insulated. Therefore, it is possible to suppress electrical short circuits between the movable parts 12A, 12B, support parts 17A, 17B and column part 18 of the device substrate 10 via the silicon substrate P10.

[0052] In one embodiment described above, the insulating layer is a silicon nitride layer H12 made of silicon nitride. The insulating layer may also be made of aluminum nitride, aluminum oxide, or silicon carbide.

[0053] According to this, existing semiconductor equipment can be used for forming the insulating layer.

[0054] 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.

[0055] <Second Embodiment> Next, the configuration of the MEMS device 2 according to the second embodiment of the present invention and its manufacturing method will be described with reference to Figures 8 to 10. Figure 8 is a cross-sectional view of the MEMS device 2 according to the second embodiment. Figures 9 to 10 are cross-sectional views showing the manufacturing process of the MEMS device according to the second embodiment.

[0056] As shown in Figure 8, the MEMS device 2 differs from the MEMS device 1 according to the first embodiment in that the first bonding layer 50 further has a dummy anchor portion DAK. The dummy anchor portion DAK is connected to the silicon substrate P10 of the first lid substrate 30 and is spaced apart from the silicon substrate F10 of the device substrate 10. The dummy anchor portion DAK is provided, for example, in a region that overlaps with the gap between the movable parts 12B in a plan view.

[0057] As shown in Figure 9, during the BG processing and CMP processing of the silicon substrate F10, the dummy anchor portion DAK supports the silicon substrate F10, suppressing deformation and maintaining the gap between the silicon substrate F10 and the silicon substrate P10. Then, as shown in Figure 10, the dummy anchor portion DAK is separated from the silicon substrate F10 by the removal process of the silicon substrate F10.

[0058] According to this embodiment, the deformation of the silicon substrate F10 during BG processing and CMP processing is further suppressed by the dummy anchor portion DAK, thereby further improving the thickness accuracy of the silicon substrate F10. In addition, since the dummy anchor portion DAK is separated from the silicon substrate F10, the displacement of the movable portion 12B is not easily hindered.

[0059] <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 11.

[0060] As shown in Figure 11, the MEMS device 3 differs from the MEMS device 2 according to the second embodiment in that the first bonding layer 350 electrically connects the peripheral portion 19 of the silicon substrate F10 to the silicon substrate P10, and the second bonding layer 360 electrically connects the peripheral portion 19 of the silicon substrate F10 to the silicon substrate Q10.

[0061] In the peripheral bonding portion FL of the first bonding layer 350, the silicon nitride layer H12 is omitted, and the polysilicon layer H11 is in contact with both the silicon substrate P10 and the silicon substrate F10, electrically connecting the silicon substrate P10 and the silicon substrate F10. Through holes are formed in the silicon oxide layer F11 on the peripheral portion 19. The second bonding layer 360 is in contact with the silicon substrate F10 of the peripheral portion 19 through these through holes, electrically connecting the silicon substrate F10 and the silicon substrate Q10. In other words, the silicon substrate P10 and the silicon substrate Q10 are electrically connected via the silicon substrate F10 of the peripheral portion 19.

[0062] According to this embodiment, the first cover substrate 30 can be electrically grounded by the second cover substrate 40.

[0063] Incidentally, the layer structure of the peripheral joint FL is different from the layer structure of the anchor portion AK and the dummy anchor portion DAK, and the anchor portion AK and the dummy anchor portion DAK have a polysilicon layer H11 and a silicon nitride layer H12. Therefore, the support portions 17A, 17B and the column portion 18 are electrically insulated from the silicon substrate P10, and the support portions 17A, 17B and the column portion 18 are not electrically short-circuited and are not electrically grounded. Thus, the detection of changes in capacitance formed by the movable portions 12A and 12B is not hindered by the electrically grounded silicon substrate P10.

[0064] Furthermore, at least a portion of the anchor portion AK and the dummy anchor portion DAK may be configured to electrically connect the silicon substrate P10 and the silicon substrate F10.

[0065] <Fourth Embodiment> Next, the configuration of the MEMS device 4 according to the fourth embodiment of the present invention will be described with reference to Figure 12.

[0066] As shown in Figure 12, the MEMS device 4 differs from the MEMS device 3 according to the third embodiment in that a cavity C10 is formed on the silicon substrate P10 side of the silicon substrate F10 in the movable part 412A. The cavity C10 is formed, for example, by providing a patterned mask on the silicon substrate F10, locally thermally oxidizing the silicon substrate F10 through the openings of the mask (LOCOS: Local Oxidation of Silicon), and removing the thermally oxidized region. The method for forming the cavity C10 is not limited to the above, and may be formed, for example, by perpendicular anisotropic reactive ion etching.

[0067] Because the cavity C10 is formed, the thickness of the movable portion 412A of the device substrate 410 is smaller than the thickness of the movable portion 12B, support portions 17A, 17B, column portion 18, and peripheral portion 19 of the device substrate 410. The distance in the Z-axis direction between the movable portion 412A and the silicon substrate P10 is greater than the distance in the Z-axis direction between the support portion 17A and the silicon substrate P10.

[0068] According to this embodiment, the range of motion of the movable part 412A that moves in the Z-axis direction can be increased, and the detection accuracy of the change in capacitance formed by the movable part 412A can be improved.

[0069] <Fifth Embodiment> Next, the configuration of the MEMS device 5 according to the fifth embodiment of the present invention will be described with reference to Figure 13.

[0070] As shown in Figure 13, the MEMS device 5 differs from the MEMS device 3 according to the third embodiment in that a cavity C30 is formed in the region of the silicon substrate P10 facing the movable part 12A. As a result, the distance in the Z-axis direction between the movable part 12A and the silicon substrate P10 is greater than the distance in the Z-axis direction between the support part 17A and the silicon substrate P10.

[0071] According to this embodiment, the range of motion of the movable part 12A that moves in the Z-axis direction can be increased, and the detection accuracy of the change in capacitance formed by the movable part 12A can be improved.

[0072] As shown in the fourth embodiment, a cavity may be further formed on the silicon substrate P10 side of the silicon substrate F10 in the movable part that moves in the Z-axis direction. By forming cavities on both the silicon substrate F10 side of the silicon substrate P10 and the silicon substrate P10 side of the silicon substrate F10, the range of motion of the movable part that moves in the Z-axis direction can be further expanded.

[0073] 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.

[0074] As described above, according to one aspect of the present invention, a MEMS device capable of achieving high density and a method for manufacturing the same can be provided.

[0075] 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 equivalents thereof are also included. That is, any design modifications made to each embodiment by those 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.

[0076] 1…MEMS device 10…Device substrate 12A, 12B…Movable parts 17B, 17C…Support parts 18…Column part 19…Peripheral part F10…Silicon substrate F11…Silicon oxide layer 30…First cover substrate P10…Silicon substrate 40…Second cover substrate Q10…Silicon substrate 50…First bonding layer H11…Polysilicon layer H12…Silicon nitride layer 60…Second bonding layer Q10…Silicon substrate Q11…Silicon oxide layer

Claims

1. A MEMS device comprising a first silicon substrate made of single-crystal silicon, a second silicon substrate made of single-crystal silicon, and a bonding layer that bonds the first silicon substrate and the second silicon substrate, wherein the second silicon substrate has a movable portion configured to be movable away from the first silicon substrate and a support portion that supports the movable portion, and the bonding layer has an anchor portion that bonds the support portion to the first silicon substrate, and the anchor portion is provided by a material that has higher etching resistance to an etchant that etches silicon oxide than silicon oxide.

2. The MEMS device according to claim 1, wherein the anchor portion includes a silicon layer.

3. The MEMS device according to claim 2, wherein the silicon layer is provided by polycrystalline silicon or amorphous silicon.

4. The MEMS device according to any one of claims 1 to 3, wherein the anchor portion includes an insulating layer.

5. The MEMS device according to claim 4, wherein the insulating layer is provided by silicon nitride, aluminum nitride, aluminum oxide, or silicon carbide.

6. The MEMS device according to any one of claims 1 to 5, wherein the bonding layer further comprises a dummy anchor portion, the dummy anchor portion being bonded to the first silicon substrate and spaced apart from the second silicon substrate.

7. The MEMS device according to any one of claims 1 to 6, wherein the bonding layer electrically connects the first silicon substrate and the second silicon substrate.

8. The MEMS device according to any one of claims 1 to 7, wherein a cavity is formed on the side of the second silicon substrate that is on the first silicon substrate side.

9. The MEMS device according to any one of claims 1 to 8, wherein a cavity is formed on the second silicon substrate side of the first silicon substrate.

10. A method for manufacturing a MEMS device, comprising: preparing a first silicon substrate made of single-crystal silicon; preparing a second silicon substrate made of single-crystal silicon; joining the first silicon substrate and the second silicon substrate with a bonding layer; providing a mask made of silicon oxide on the second silicon substrate and etching the second silicon substrate to provide a movable part and a support part; and removing the mask by etching, wherein the bonding layer has an anchor part for joining the support part to the first silicon substrate, and the anchor part is provided by a material that has higher etching resistance to an etchant for etching silicon oxide than silicon oxide.

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