MEMS device and manufacturing method therefor

Abstract

A Microelectromechanical systems (MEMS) device (1) is configured by laminating, in order, a first lid substrate (40), a first device substrate (10) made of single-crystal silicon, a second device substrate (20) made of single-crystal silicon, and a second lid substrate (30) having a handle member and a silicon oxide film. The MEMS device detects capacitance formed by the first device substrate (10). The first device substrate (10) has a movable part (12) which is separate from the first lid substrate (40) and the second device substrate (20) and configured to be movable. The first device substrate (10) and the second device substrate (20) are bonded through direct bonding of the single-crystal silicon of each substrate. The second device substrate (20) and the second lid substrate (30) are bonded via a silicon oxide film of the second lid substrate (30). The side of the handle member of the second lid substrate (30) facing the second device substrate (20) is provided in a planar shape. On the side of the second device substrate (20) facing the second lid substrate (30), a cavity is formed in at least part of the region corresponding to the movable part (12).

Description

MEMS device and manufacturing method thereof

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

[0002] Micro Electro Mechanical Systems (MEMS) devices manufactured using MEMS technology are becoming widespread. MEMS devices are used, for example, in inertial sensors that detect acceleration and angular velocity based on changes in capacitance. To improve the performance of MEMS devices, multi-layered MEMS structures have been proposed.

[0003] For example, Patent Document 1 discloses a MEMS device in which an upper cover, a silicon film made of single-crystal silicon, a silicon substrate made of single-crystal silicon, and a lower cover are stacked in this order. The silicon film and the silicon substrate are bonded via a silicon oxide layer, and the silicon substrate and the lower cover are bonded via a silicon oxide layer. A cavity is formed on the side of the lower cover facing the silicon substrate.

[0004] International Publication No. 2023 / 032304

[0005] However, in the MEMS device described in Patent Document 1, the silicon substrate and the lower cover are laminated by a bonding technique, and misalignment when bonding the silicon substrate and the lower cover may result in a decrease in reliability.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a MEMS device and a manufacturing method thereof that can improve reliability.

[0007] A MEMS device according to one aspect of the present invention is a MEMS device which detects the capacitance formed by a first device substrate, which is stacked in this order: a first lid substrate; a first device substrate made of single crystal silicon; a second device substrate made of single crystal silicon; and a second lid substrate having a handle member and a silicon oxide film; the first device substrate has a movable part which is configured to be movable and spaced apart from the first lid substrate and the second device substrate; the first device substrate and the second device substrate are bonded by direct bonding of the single crystal silicon to each other; the second device substrate and the second lid substrate are bonded via the silicon oxide film of the second lid substrate; the side of the handle member of the second lid substrate facing the second device substrate is flat; and a cavity is formed in at least a part of the area corresponding to the movable part on the side of the second device substrate facing the second lid substrate.

[0008] According to another aspect of the present invention, there is provided a MEMS device in which a first lid substrate, a first device substrate made of single crystal silicon, a second device substrate made of single crystal silicon, and a second lid substrate having a handle member and a silicon oxide film are stacked in this order, and which detects capacitance formed by the first device substrate, wherein the first device substrate has a movable portion configured to be movable and spaced apart from the first lid substrate and the second device substrate, the first device substrate and the second device substrate are bonded by direct bonding of the single crystal silicon together, and the second The device substrate and the second lid substrate are bonded via a silicon oxide film of the second lid substrate, and the second device substrate has a first convex portion and a second convex portion protruding toward the second lid substrate, the tip of the first convex portion is bonded to the silicon oxide film of the second lid substrate, and the tip of the second convex portion is spaced apart from the second lid substrate, and when the direction in which the first lid substrate, the first device substrate, the second device substrate, and the second lid substrate are stacked is defined as the height direction and the direction intersecting the height direction is defined as the width direction, the height of the second convex portion is equal to the height of the first convex portion and the width of the second convex portion is smaller than the width of the first convex portion.

[0009] Another aspect of the present invention relates to a method for manufacturing a MEMS device that detects capacitance formed by a first device substrate, the method including: preparing a first lid substrate; preparing a first device substrate made of single crystal silicon; preparing a second device substrate made of single crystal silicon; preparing a second lid substrate having a handle member and a silicon oxide film; and stacking the first lid substrate, the first device substrate, the second device substrate, and the second lid substrate in this order, wherein the first device substrate includes forming a movable portion that is configured to be movable and spaced apart from the first lid substrate and the second device substrate; preparing the second device substrate includes forming a cavity in at least a part of a region corresponding to the movable portion on the side facing the second lid substrate; and stacking includes bonding the first device substrate and the second device substrate by direct bonding of the single crystal silicon together, and bonding the second device substrate and the second lid substrate via the silicon oxide film of the second lid substrate.

[0010] According to the present invention, it is possible to provide a MEMS device and a manufacturing method thereof that can improve reliability.

[0011] FIG. 1 is a cross-sectional view of a MEMS device according to a first embodiment; FIG. 2 is a flowchart showing a manufacturing method for a MEMS device according to a first embodiment; FIG. 3 is a cross-sectional view showing a manufacturing process for a MEMS device according to a first embodiment; FIG. 4 is a cross-sectional view showing a manufacturing process for a MEMS device according to a first embodiment; FIG. 5 is a cross-sectional view showing a manufacturing process for a MEMS device according to a first embodiment; FIG. 6 is a cross-sectional view showing a manufacturing process for a MEMS device according to a first embodiment; FIG. 7 is a cross-sectional view of a MEMS device according to a second embodiment; FIG. 8 is an enlarged cross-sectional view of a MEMS device according to a second embodiment; FIG. 9 is a cross-sectional view showing a manufacturing method for a MEMS device according to a second embodiment; FIG. 10 is a cross-sectional view showing a manufacturing method for a MEMS device according to a third embodiment;

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The drawings of the present embodiment are merely examples, and the dimensions and shapes of each part are schematic, so the technical scope of the present invention should not be interpreted as being limited to the embodiment.

[0013] First Embodiment First, the configuration of a MEMS device 1 according to a first embodiment of the present invention will be described with reference to Fig. 1. Fig. 1 is a cross-sectional view of the MEMS device according to the first embodiment.

[0014] The components of the MEMS device 1 will be described below. For the sake of clarity and understanding of the positional relationships between the various components, each drawing may be accompanied by a Cartesian coordinate system consisting of an X-axis, a Y-axis, and a Z-axis. The directions parallel to the X-axis, the Y-axis, and the Z-axis are referred to as the X-axis, the Y-axis, and the Z-axis, respectively. The plane defined by the X-axis and the Y-axis is referred to as the XY plane. For the sake of convenience, the positive Z-axis direction (the direction of the arrow) will be referred to as the top or upper side, and the negative Z-axis direction (the direction opposite to the arrow) will be referred to as the bottom or lower side. However, the orientation of the MEMS device 1 is not limited to this. In the following description, the Z-axis direction will be referred to as the height direction and depth direction, and the Z-axis direction will be referred to as the width direction.

[0015] The MEMS device 1 is a device manufactured using MEMS technology. The MEMS device 1 includes a first device substrate 10, a second device substrate 20, a first lid substrate 40, and a second lid substrate 30. The MEMS device 1 is a capacitance-type sensor that detects inertial forces (e.g., acceleration and angular velocity) and pressure in the X-axis, Y-axis, and Z-axis directions by detecting the capacitance formed by the first device substrate 10. 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 in the Z-axis direction. The first lid substrate 40 is anodically bonded to the first device substrate 10, 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 lid substrate 30. The first lid substrate 40 and the second lid substrate 30 form a package structure that defines a movable space within which the first device substrate 10 and the second device substrate 20 can move.

[0016] The first device substrate 10 is provided by a silicon substrate F10. The silicon substrate F10 is formed of single crystal silicon. The silicon substrate F10 is formed of, for example, a p-type silicon (Si) semiconductor. The silicon substrate F10 may contain boron (B) or the like as a p-type dopant. The resistance value of the silicon (Si) used in the silicon substrate F10 is, for example, about 10 mΩ·cm.

[0017] 1 , the first device substrate 10 includes movable portions 12A, 12B, and 12C, bonding portions 14B and 14C, support portions 18A and 18B, and a peripheral portion 19. The movable portions 12A, 12B, and 12C, bonding portions 14B and 14C, support portions 18A and 18B, and peripheral portion 19 are formed by patterning a silicon substrate F10 through a removal process. The removal process is performed by dry etching known as deep reactive ion etching (DRIE), for example. The removal process may also be performed by other techniques such as wet etching and laser etching.

[0018] A movable space 11A is provided between the first lid substrate 40 and the movable portions 12A, 12B, and 12C. A movable space 11B is provided between the second device substrate 20 and the movable portions 12A, 12B, and 12C. In other words, the movable portions 12A, 12B, and 12C 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. Portions of the silicon substrate F10 around the movable portions 12A, 12B, and 12C are separated from other portions by slits penetrating in the Z-axis direction. This allows the movable portions 12A, 12B, and 12C to be movable.

[0019] The cavities in the first device substrate 10 that define the movable spaces 11A and 11B are formed, for example, by locally thermally oxidizing the silicon substrate F10 and removing the thermally oxidized region. However, the method for forming the cavities in the first device substrate 10 is not limited to the above, and may be formed by dry etching, wet etching, laser etching, or other techniques for the silicon substrate F10.

[0020] The movable portion 12A serves as an electrode and weight for detecting inertial forces and pressures in the Z-axis direction. The movable portion 12A forms a capacitance with the first lid substrate 40, and also forms a capacitance with the second device substrate 20. When the MEMS device 1 is subjected to an inertial force or pressure in the Z-axis direction, the movable portion 12A is displaced in the Z-axis direction, and the gap between the movable spaces 11A and 11B in the Z-axis direction changes. Based on the change in the gap between the movable spaces 11A and 11B, the capacitance formed between the movable portion 12A and the first lid substrate 40 and the capacitance formed between the movable portion 12A and the second device substrate 20 change. By detecting these changes in both capacitances, the inertial force in the Z-axis direction applied to the MEMS device 1 can be detected.

[0021] The movable portion 12B serves as an electrode and weight for detecting inertial force and pressure in the X-axis direction. Multiple movable portions 12B are arranged at intervals in the X-axis direction, and electrostatic capacitance is formed between the movable portions 12B. When the MEMS device 1 is subjected to inertial force and pressure in the X-axis direction, the movable portions 12B are displaced in the X-axis direction. At this time, adjacent movable portions 12B are displaced with different eases, and the distance between adjacent movable portions 12B changes. Based on this change in distance, the electrostatic capacitance formed by the movable portions 12B changes. By detecting this change in electrostatic capacitance, the inertial force and pressure in the X-axis direction applied to the MEMS device 1 can be detected.

[0022] The movable portion 12C serves as an electrode and weight for detecting inertial force and pressure in the Y-axis direction. Multiple movable portions 12C are arranged at intervals in the Y-axis direction, and electrostatic capacitance is formed between the movable portions 12C. When the MEMS device 1 is subjected to inertial force and pressure in the Y-axis direction, the movable portions 12C are displaced in the Y-axis direction. At this time, adjacent movable portions 12C are displaced with different ease, and the distance between adjacent movable portions 12C changes. The electrostatic capacitance formed by the movable portions 12C changes based on this change in distance. By detecting this change in electrostatic capacitance, the inertial force and pressure in the Y-axis direction applied to the MEMS device 1 can be detected.

[0023] The bonding portion 14B is bonded to the second device substrate 20 and connects the movable portion 12B to the second device substrate 20. The bonding portion 14C is bonded to the second device substrate 20 and connects the movable portion 12C to the second device substrate 20. The bonding portion 14B is bonded to a bonding portion 24B of the second device substrate 20 (described later), and the bonding portion 14C is bonded to a bonding portion 24C of the second device substrate 20 (described later). The bonding between the bonding portion 14B and the bonding portion 24B and the bonding between the bonding portion 14C and the bonding portion 24C are direct bonding between the single crystal silicon substrates (silicon substrate F10 and silicon substrate F20). The bonding portions 14B and 14C are separated from the first lid substrate 40 by the movable space 11A. This prevents stress from the first lid substrate 40 from being transmitted to the movable portions 12B and 12C via the bonding portions 14B and 14C.

[0024] The support portion 18A supports the movable portion 12A of the first device substrate 10. The support portion 18A is bonded to the first lid substrate 40, and is bonded to the support portion 28A of the second device substrate 20 (described later). The bond between the support portion 18A and the support portion 28A is a direct bond between the single crystal silicon substrates F10 and F20. The support portion 18A and the support portion 28A are sandwiched between the first lid substrate 40 and the second lid substrate 30. The support portion 18A is separated from the movable portions 12B and 12C, the bonding portions 14B and 14C, the support portion 18B, the peripheral portion 19, etc. by a slit that penetrates the silicon substrate F10 in the Z-axis direction.

[0025] The support portion 18B supports the movable portions 12B and 12C of the first device substrate 10. The support portion 18B is bonded to the first lid substrate 40 and to a support portion 28B of the second device substrate 20 (described later). The bond between the support portion 18B and the support portion 28B is a direct bond between the single crystal silicon substrates F10 and F20. The support portion 18B and the support portion 28B are sandwiched between the first lid substrate 40 and the second lid substrate 30. The support portion 18B is bonded to an electrode provided on the first device substrate 10 side of the first lid substrate 40, thereby providing electrical continuity between the first lid substrate 40 and the first device substrate 10. The support portion 18B is separated from the movable portion 12A, the support portion 18A, the peripheral portion 19, and the like by a slit penetrating the silicon substrate F10 in the Z-axis direction.

[0026] The peripheral portion 19 is provided in a frame shape along the outer edge of the first device substrate 10. When viewed in a plan view in the Z-axis direction (hereinafter simply referred to as "plan view"), the peripheral portion 19 surrounds the movable portions 12A, 12B, and 12C, the bonding portions 14B and 14C, and the support portions 18A and 18B. The peripheral portion 19 is bonded to an insulating portion of the first lid substrate 40 and is bonded to a peripheral portion 29 of the second device substrate 20 (described later). The bonding between the peripheral portion 19 and the first lid substrate 40 is, for example, anodic bonding between the single crystal silicon (silicon substrate F10) of the first device substrate 10 and the silicon oxide (glass substrate Q11) of the first lid substrate 40. The bonding between the peripheral portion 19 and the peripheral portion 29 is direct bonding between the single crystal silicon (silicon substrate F10 and silicon substrate F20). The peripheral portion 19 is separated from the movable portions 12A, 12B, and 12C, the bonding portions 14B and 14C, and the support portions 18A and 18B by slits that penetrate the silicon substrate F10 in the Z-axis direction.

[0027] The second device substrate 20 is provided by a silicon substrate F20. The silicon substrate F20 is formed of single crystal silicon. The silicon substrate F20 is formed of, for example, a p-type silicon (Si) semiconductor. The silicon substrate F20 may contain boron (B) or the like as a p-type dopant. The resistance value of the silicon (Si) used in the silicon substrate F20 is, for example, about 10 mΩ·cm.

[0028] The second device substrate 20 includes bonding portions 24B and 24C, support portions 28A and 28B, and a peripheral portion 29. The bonding portions 24B and 24C, support portions 28A and 28B, and peripheral portion 29 are formed by patterning the silicon substrate F20 through a removal process. The removal process is performed by, for example, DRIE, but is not limited to this, and may be performed by other techniques such as wet etching or laser etching. The second device substrate 20 is separated from the second lid substrate 30 in areas corresponding to the movable portions 12A, 12B, and 12C and the bonding portions 14B and 14C.

[0029] A movable space 21 is provided between the second lid substrate 30 and areas of the second device substrate 20 corresponding to the movable portions 12A, 12B, 12C and the bonding portions 14B, 14C. In other words, the areas of the second device substrate 20 corresponding to the movable portions 12A, 12B, 12C and the bonding portions 14B, 14C are spaced apart 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 movable space 21 prevents stress from the second lid substrate 30 from being transmitted to the movable portions 12A, 12B, 12C.

[0030] The cavity of the second device substrate 20 constituting the movable space 21 is formed in at least a portion of the region corresponding to the movable portions 12A, 12B, and 12C 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 using vertical anisotropic reactive ion etching. The depth of the cavity in the Z-axis direction is, for example, 1 μm to 50 μm, preferably 10 μm to 40 μm. However, the method for forming the cavity of the second device substrate 20 is not limited to the above, and may be performed using techniques 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 technique of locally thermally oxidizing the silicon substrate F20 and removing the thermally oxidized region. However, it is preferable that the cavity of the second device substrate 20 be formed by vertical anisotropic etching such that the angle between the bottom surface and the side surface is close to 90 degrees.

[0031] Bonding portion 24B is bonded to bonding portion 14B of the first device substrate 10. Bonding portion 24C is bonded to bonding portion 14C of the first device substrate 10. A movable space 21 exists between bonding portions 24B, 24C and the second lid substrate 30, and bonding portions 24B, 24C are spaced apart from the second lid substrate 30. Bonding portion 24B is separated from bonding portion 24C, support portion 28A, and peripheral portion 29 by slits. Bonding portion 24C is separated from bonding portion 24B, support portion 28A, and peripheral portion 29 by slits. Bonding portion 24B is connected to support portion 28B. Bonding portion 24C is connected to support portion 28B.

[0032] The support portion 28A supports an electrode portion that functions as an electrode that forms capacitance with the movable portion 12A on the second device substrate 20. The support portion 28B supports the joint portions 24B and 24C. The support portion 28A is separated from the support portion 28B, the joint portions 24B and 24C, and the peripheral portion 29 by slits. The support portion 28B is separated from the support portion 28A and the peripheral portion 29 by slits.

[0033] The support portion 28A has a first protrusion PR2 that protrudes toward the second lid substrate 30. The support portion 28B has a first protrusion PR1 that protrudes toward the second lid substrate 30. The tips of the first protrusions PR1 and PR2 are directly bonded to a silicon oxide film P11 of the second lid substrate 30, which will be described later. The height of the first protrusions PR1 and PR2 in the Z-axis direction corresponds to the depth in the Z-axis direction of the cavity in the second device substrate 20 that constitutes the movable space 21, and is, for example, 1 μm or more and 50 μm or less, and preferably 10 μm or more and 40 μm or less. At the corners on the tip side of the first protrusions PR1 and PR2, the planar tip surface and the planar side surface are connected so as to form a right angle or an obtuse angle.

[0034] The peripheral portion 29 is provided in a frame shape along the outer edge of the second device substrate 20. In a plan view, the peripheral portion 29 surrounds the bonding portions 24B, 24C and the support portions 28A, 28B. The peripheral portion 29 is bonded to the peripheral portion 19 of the first device substrate 10 and is bonded 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. The peripheral portion 29 is separated from the bonding portions 24B, 24C and the support portions 28A, 28B by a slit penetrating the silicon substrate F20 in the Z-axis direction.

[0035] In a cross section L1 of the XY plane that crosses the cavity of the second device substrate 20 that constitutes the movable space 21, the area ratio of the area of ​​the internal space to the area of ​​the MEMS device 1 is 20% or more, preferably 40% or more, more preferably 60% or more, for example 50% or more. Conversely, in the cross section L1, the area ratio of the area of ​​the silicon substrate F20 of the second device substrate 20 to the area of ​​the MEMS device 1 is 80% or less, preferably 40% or less, more preferably 40% or less, for example 50% or less. Note that the cross section L1 is an XY cross section that crosses the first protrusions PR1 and PR2.

[0036] In a cross section L2 of the XY plane that crosses the portion of the second device substrate 20 on the first device substrate 10 side of the cavity that forms the movable space 21, the area ratio of the area of ​​the internal space to the area of ​​the MEMS device 1 is 20% or more, preferably 40% or more, and more preferably 60% or more. Conversely, in the cross section L2, the area ratio of the area of ​​the silicon substrate F20 of the second device substrate 20 to the area of ​​the MEMS device 1 is 80% or less, preferably 40% or less, and more preferably 40% or less. Note that the cross section L2 is an XY cross section that crosses the bonding portions 24B, 24C and the support portions 28A, 28B, and is an XY cross section that crosses a slit that penetrates the silicon substrate F20 in the X-axis direction.

[0037] The first lid substrate 40 is provided in a flat plate shape. The first lid substrate 40 is formed of a silicon substrate Q10 and a glass substrate Q11. The silicon substrate Q10 is formed of, for example, a p-type silicon (Si) semiconductor. The resistance value of the silicon (Si) used in the silicon substrate Q10 is, for example, about 10 mΩ·cm. The glass substrate Q11 is formed of a silicon oxide (for example, SiO ２ The glass substrate Q11 is formed of glass containing SiO as a main component. Here, the main component of the glass refers to a component that accounts for 50 mass % or more of all components that make up the glass. As an example, the glass substrate Q11 is formed of glass containing SiO ２ The first lid substrate 40 is formed of silicate glass containing silicon as a main component. The silicon substrate Q10 is provided in multiple regions spaced apart in the XY plane. The glass substrate Q11 electrically insulates the multiple silicon substrates Q10 provided in the regions spaced apart in the XY plane. Electrodes provided on the first device substrate 10 side of the first lid substrate 40 are electrically connected to external terminals provided on the opposite side from the first device substrate 10 via the silicon substrate Q10. The portion of the first lid substrate 40 that is bonded to the peripheral portion 19 of the first device substrate 10 is provided by the glass substrate Q11. The shape of the first lid substrate is not limited to a flat plate, and a cavity may be formed on the side of the first lid substrate 40 facing the first device substrate 10.

[0038] The second lid substrate 30 is formed of a silicon substrate P10 and a silicon oxide film P11. The silicon substrate P10 is formed in a flat plate shape, and the side of the silicon substrate P10 facing the second device substrate 20 is formed in a planar shape. The silicon oxide film P11 is formed on the surface of the second lid substrate 30 that is bonded to the second device substrate 20. In other words, the silicon substrate P10 of the second lid substrate 30 is directly bonded to the silicon substrate F20 of the second device substrate 20 via the silicon oxide film P11. The silicon substrate P10 is formed, for example, from single crystal silicon. The silicon substrate P10 corresponds to an example of a handle member in the present invention. Note that the material of the handle member is not limited to single crystal silicon, as long as the second lid substrate 30 can function as a handle substrate. The second lid substrate 30 may include a semiconductor substrate, a ceramic substrate, a glass substrate, or the like, instead of the silicon substrate P10.

[0039] Next, a method for manufacturing the MEMS device 1 according to the first embodiment will be described with reference to Fig. 2 to Fig. 6. Fig. 2 is a flowchart showing the method for manufacturing the MEMS device 1 according to the first embodiment. Fig. 3 to Fig. 6 are cross-sectional views showing the manufacturing process of the MEMS device 1 according to the first embodiment.

[0040] First, two single crystal silicon substrates F10 and F20 are prepared (S10). The flat silicon substrates F10 and F20 made of single crystal silicon are prepared, and the main surfaces of the substrates are polished to improve flatness.

[0041] Next, cavities are formed in the two single-crystal silicon substrates F10 and F20 (S20). The cavities in the silicon substrate F10 are formed, for example, by providing a patterned mask on the silicon substrate F10, locally thermally oxidizing the silicon substrate F10 through openings in the mask (LOCOS: Local Oxidation of Silicon), and removing the thermally oxidized regions. The cavities in the silicon substrate F20 are formed, for example, by vertical anisotropic reactive ion etching.

[0042] The method for forming the cavity in the silicon substrate F10 is not limited to the above, and may be wet etching, dry etching, or laser etching. The method for forming the cavity in the silicon substrate F20 is not limited to the above, but is preferably vertical anisotropic etching in which the angle between the bottom and side surfaces of the cavity is close to 90 degrees. The method for forming the cavity in the silicon substrate F20 may be, for example, laser etching or crystal anisotropic wet etching.

[0043] Next, the single-crystal silicon substrates F10 and F20 are directly bonded together (S30). As shown in FIG. 3, the side of the silicon substrate F10 on which the cavity is formed is directly bonded to the side of the silicon substrate F20 opposite to the side on which the cavity is formed. Before bonding, an etching stopper film ES is provided on the bottom surface of the cavity of the silicon substrate F10. After bonding, a slit is formed through the silicon substrate F20 to define the outer shapes of each part of the second device substrate 20, such as the bonding portions 24B and 24C, the support portions 28A and 28B, and the peripheral portion 29. The slit in the silicon substrate F20 is formed, for example, by DRIE from the cavity side of the silicon substrate F20. The DRIE etching species are stopped by the etching stopper film ES provided on the silicon substrate F10 and do not reach the silicon substrate F10. The formation of the slits in the silicon substrate F20 may be performed before the formation of the cavity in the silicon substrate F20, or may be performed after the formation of the cavity in the silicon substrate F20 and before the direct bonding of the silicon substrates F10 and F20. Furthermore, the formation of the cavities and the slits in the silicon substrate F20 may be performed after the direct bonding of the silicon substrates F10 and F20.

[0044] Next, the second lid substrate 30 is directly bonded to the second device substrate 20 (S40). As shown in Fig. 4, the side of the second lid substrate 30 on which the silicon oxide film P11 is provided is directly bonded to the side of the silicon substrate F20 on which the cavity is formed. At this time, the silicon oxide film P11 is provided on the entire surface of the silicon substrate P10.

[0045] Next, the first device substrate 10 is removed (S50). The single-crystal silicon substrate F10 is removed by DRIE up to the position where the etching stopper film ES was formed, forming a slit penetrating the silicon substrate F10 in the Z-axis direction. This forms the outer shapes of each part of the first device substrate 10, such as the movable portions 12A, 12B, and 12C, the bonding portions 14B and 14C, the support portions 18A and 18B, and the peripheral portion 19. At this time, a cavity is formed on the silicon substrate F10 opposite the silicon substrate F2. This cavity may be formed before or after the slit formation. For example, the cavity is formed by removing a thermally oxidized region of the silicon substrate F10 that has been locally thermally oxidized. However, this is not limited to this, and the cavity may also be formed by wet etching, dry etching, or laser etching.

[0046] Next, the silicon oxide film P11 of the second lid substrate 30 is removed (S60). As shown in FIG. 5, an etching gas HF that removes silicon oxide without reacting with silicon is supplied through a slit formed in the first device substrate 10 to remove the etching stopper film ES and the silicon oxide film P11. The etching gas HF is, for example, gas-phase hydrofluoric acid gas. The portion of the silicon oxide film P11 sandwiched between the silicon substrates P10 and F20 is side-etched from the sides but is not completely removed, connecting the silicon substrates P10 and F20.

[0047] Finally, the first lid substrate 40 is anodically bonded to the first device substrate 10 (S70). As shown in Fig. 6, the etching gas HF is degassed, and the glass substrate Q11 of the first lid substrate 40 is bonded to the side of the silicon substrate F10 opposite to the silicon substrate F20.

[0048] As described above, the first lid substrate 40, the first device substrate 10 made of single crystal silicon, the second device substrate 20 made of single crystal silicon, and the second lid substrate 30 having a silicon substrate P10 and a silicon oxide film P11 are stacked in this order in the MEMS device 1. A cavity is formed on the second device substrate 20 facing the second lid substrate 30, and the second device substrate 20 side of the second lid substrate 30 is provided in a flat shape.

[0049] As described above, the manufacturing method of the MEMS device 1 includes preparing the first lid substrate 40, preparing the first device substrate 10 made of single crystal silicon, preparing the second device substrate 20 made of single crystal silicon, preparing the second lid substrate 30 having a silicon substrate P10 and a silicon oxide film P11, and stacking the first lid substrate 40, the first device substrate 10, the second device substrate 20, and the second lid substrate 30 in this order. Preparing the second device substrate 20 includes forming a cavity on the side facing the second lid substrate 30, and stacking includes bonding the first device substrate 10 and the second device substrate 20 by direct bonding of the single crystal silicon to each other, and bonding the second device substrate 20 and the second lid substrate 30 via the silicon oxide film P11 of the second lid substrate 30.

[0050] According to this, alignment adjustment is not required when directly bonding the second device substrate 20 and the second lid substrate 30, so there is no decrease in reliability due to misalignment between the second device substrate 20 and the second lid substrate 30, and it is possible to improve the reliability of the MEMS device 1. Furthermore, because it is possible to design without taking into consideration the alignment margin between the second device substrate 20 and the second lid substrate 30, it is possible to increase the density and miniaturize the MEMS structure, and it is possible to improve the performance of the MEMS device 1.

[0051] Furthermore, because the first device substrate 10 and the second device substrate 20 are stacked by directly bonding single-crystal silicon together, warping of the MEMS structure is suppressed compared to when the MEMS structure is formed using polycrystalline silicon, which has a higher stress than single-crystal silicon. This allows for improved performance of the MEMS device 1. Furthermore, because the MEMS structure has a two-layer structure consisting of the first device substrate 10 and the second device substrate 20, the design flexibility of the MEMS structure is improved compared to when the MEMS structure is a single-layer structure. Furthermore, by miniaturizing and densifying the MEMS structure, the performance of the MEMS device 1 can be improved. Furthermore, because the first device substrate 10 and the second device substrate 20 are formed using single-crystal silicon, they can be formed thicker than when they are formed using polycrystalline silicon, allowing for improved performance of the MEMS device 1. Furthermore, the first device substrate 10 and the second device substrate 20 can be bonded together with a gap formed between them, and the second device substrate 20 and the second lid substrate 30 can be bonded together with a gap formed between them. Therefore, the etching gas HF can be supplied through the slits formed in the first device substrate 10 and the second device substrate 20 without providing a plurality of through holes in the first device substrate 10 and the second device substrate 20 for supplying the etching gas HF that removes the etching stopper film ES and the silicon oxide film P11. Therefore, the MEMS structure can be made smaller and denser by the amount that the plurality of through holes for supplying the etching gas HF can be omitted, and the performance of the MEMS device 1 can be improved.

[0052] As one aspect of the above, in a cross section L1 of the second device substrate 20 that crosses the cavity, the area ratio of the area of ​​the internal space to the area of ​​the MEMS device 1 is 50% or more.

[0053] This allows the internal space of the MEMS device 1 to be enlarged, thereby diluting outgassing generated in the internal space of the MEMS device 1 and leak gas that has entered the internal space of the MEMS device 1 from the outside, thereby suppressing fluctuations in the degree of vacuum in the internal space of the MEMS device 1. Therefore, the reliability of the MEMS device 1 can be improved.

[0054] As one aspect of the above, in a cross section L2 that cuts across the portion of the second device substrate 20 on the first device substrate 10 side of the cavity, the area ratio of the area of ​​the internal space to the area of ​​the MEMS device 1 is 20% or more.

[0055] This allows the internal space of the MEMS device 1 to be enlarged, thereby diluting outgassing generated in the internal space of the MEMS device 1 and leak gas that has entered the internal space of the MEMS device 1 from the outside, thereby suppressing fluctuations in the degree of vacuum in the internal space of the MEMS device 1. Therefore, the reliability of the MEMS device 1 can be improved.

[0056] Other embodiments will be described below. Components that are the same as or similar to those in the first embodiment are denoted by the same or similar reference numerals, and descriptions thereof will be omitted as appropriate. Furthermore, similar effects resulting from similar components will not be mentioned in detail.

[0057] Second Embodiment Next, the configuration of a MEMS device 2 according to a second embodiment of the present invention will be described with reference to Fig. 7 and Fig. 8. Fig. 7 is a cross-sectional view of the MEMS device 2 according to the second embodiment. Fig. 8 is an enlarged cross-sectional view of the MEMS device 2 according to the second embodiment.

[0058] 7, the second device substrate 220 has a second protrusion PR3 that protrudes from the joint 24C toward the second lid substrate 30. The tip of the second protrusion PR3 is spaced apart from the second lid substrate 30 and faces the second lid substrate 30 with a gap therebetween. At the corner on the tip side of the second protrusion PR3, the flat tip surface and the flat side surface are connected so as to form a right angle or an obtuse angle.

[0059] 8 , when the dimension of the second protrusion PR3 in the Z-axis direction is defined as height H2 and the dimension of the first protrusion PR2 in the Z-axis direction is defined as height H1, height H2 is equal to height H1 (H1=H2). When the dimension of the second protrusion PR3 in the X-axis direction is defined as width W2 and the dimension of the first protrusion PR2 in the X-axis direction is defined as width W1, width W2 is smaller than width W1 (W2<W1). When the distance in the X-axis direction between the end of the first protrusion PR2 on the negative X-axis side of the surface facing the silicon substrate P10 and the end of the silicon oxide film P11 on the negative X-axis side of the surface joined to the first protrusion PR2 is defined as distance D1, twice the distance D1 is equal to or greater than width W2 but smaller than width W1 (W2≦D1×2<W1), preferably greater than width W2 but smaller than width W1 (W2<D1×2<W1).

[0060] The distance in the X-axis direction between the end of the first protrusion PR2 on the surface facing the silicon substrate P10, which is on the positive side of the X-axis, and the end of the silicon oxide film P11 on the surface joined to the first protrusion PR2, which is on the positive side of the X-axis, is also D1. The distance D1 may be equal to or greater than the width W2 (W2≦D1).

[0061] Next, a method for manufacturing the MEMS device 2 according to the second embodiment will be described with reference to FIGS.

[0062] 9 , when the second lid substrate 30 is directly bonded to the second device substrate 220 (S40), the tip of the second protrusion PR3 is directly bonded to the silicon oxide film P11 of the second lid substrate 30. Therefore, the bonding portion 24C is fixed to the second lid substrate 30.

[0063] 10 , when the silicon oxide film P11 of the second lid substrate 30 is removed (S60), the etching gas HF performs a side etch on the silicon oxide film P11 sandwiched between the first protrusion PR2 and the silicon substrate P10 from the side, but the first protrusion PR2 and the second lid substrate 30 are not separated and remain connected by the silicon oxide film P11. Meanwhile, the side etch by the etching gas HF penetrates the silicon oxide film P11 sandwiched between the second protrusion PR3 and the silicon substrate P10 in the X-axis direction, removing the silicon oxide film P11 bonded to the tip of the second protrusion PR3. This separates the second protrusion PR3 from the second lid substrate 30.

[0064] As described above, in the MEMS device 2, the tips of the first protrusions PR1 and PR2 are joined to the silicon oxide film P11 of the second lid substrate 30, and the tip of the second protrusion PR3 is spaced apart from the second lid substrate 30.

[0065] According to this, the second protrusion PR3 can prevent the second device substrate 20 from sticking to the second lid substrate 30 when the second device substrate 20 is displaced toward the second lid substrate 30 .

[0066] Furthermore, in the manufacturing method of the MEMS device 2, before the silicon oxide film P11 is removed, the tip of the second convex portion PR3 is joined to the silicon oxide film P11, and the second convex portion PR3 is separated from the second lid substrate 30 by the removal processing of the silicon oxide film P11.

[0067] According to this, before the removal processing of the silicon oxide film P11, displacement of the second device substrate 20 can be suppressed via the second protrusion PR3 fixed to the second lid substrate 30. Therefore, damage to the MEMS device 2 caused by excessive displacement of the second device substrate 20 due to the impact of a drop during manufacturing can be suppressed, and the reliability of the MEMS device 2 is improved.

[0068] In one aspect of the above, the height H2 of the second convex portion PR3 is equal to the height H1 of the first convex portion PR2, and the width W2 of the second convex portion PR3 is smaller than the width W1 of the first convex portion PR2.

[0069] This allows the second protrusion PR3 to be designed so that the second protrusion PR3 is bonded to the silicon oxide film P11 before the silicon oxide film P11 is removed, and so that the second protrusion PR3 is separated from the second lid substrate 30 after the silicon oxide film P11 is removed. Therefore, in the manufacturing process of the MEMS device 2, excessive displacement of the second device substrate 20 can be suppressed, and damage to the MEMS device 2 can be suppressed.

[0070] As one aspect of the above, the relationship W2≦D1×2 holds.

[0071] According to this, the second protrusion PR3 is separated from the silicon oxide film P11 of the second lid substrate 30 by removing the silicon oxide film P11. Therefore, in the completed MEMS device 2, the displacement of the first device substrate 10 is less likely to be restricted by the second protrusion PR3, and it is possible to suppress a decrease in the detection accuracy of the MEMS device 2 caused by the second protrusion PR3. <Third Embodiment> Next, the configuration of a MEMS device 3 according to a third embodiment of the present invention will be described with reference to FIG. 11. FIG. 11 is a cross-sectional view of the MEMS device 3 according to the third embodiment.

[0072] In the MEMS device 3, the first device substrate 310 and the second device substrate 320 are configured to be rotatable around a rotation axis R1 extending in the Y-axis direction. The second device substrate 320 has two second protrusions PR31, PR32 arranged on either side of the rotation axis R1 in the X-axis direction. The movable portion 312 of the first device substrate 10 has a closest point CP closest to the first lid substrate 40 on the opposite side of the rotation axis R1 from the second protrusion PR31. The second protrusion PR31 is located on the negative X-axis and negative Z-axis sides of the rotation axis R1. The closest point CP is located on the positive X-axis and positive Z-axis sides of the rotation axis R1. The second protrusion PR32 is located on the positive X-axis and negative Z-axis sides of the rotation axis R1.

[0073] The distance in the X-axis direction between the closest point CP and the rotation axis R1 is defined as distance L1, and the distance in the Z-axis direction between the closest point CP and the first lid substrate 40 is defined as distance G1. Furthermore, the distance in the X-axis direction between the second protrusion PR31 and the rotation axis R1 is defined as distance L2, and the distance in the Z-axis direction between the second protrusion PR31 and the second lid substrate 30 is defined as distance G2. Here, the relationship G1×L2<G2×L1 holds. According to this, when the first device substrate 310 and the second device substrate 320 rotate around the rotation axis R1, the closest point CP contacts the first lid substrate 40 before the second protrusion PR31 contacts the second lid substrate 30. In other words, within the movable range of the movable portion 312 capable of detecting capacitance, the rotation of the first device substrate 310 and the second device substrate 320 around the rotation axis R1 is not obstructed by the second protrusion PR31. Therefore, it is possible to suppress a reduction in the detection range of the MEMS device 3 caused by the second protrusion portion PR31.

[0074] Some or all of the embodiments of the present invention will be described below, but the present invention is not limited to the following descriptions.

[0075] <1> A MEMS device comprising a first lid substrate, a first device substrate made of single crystal silicon, a second device substrate made of single crystal silicon, and a second lid substrate having a handle member and a silicon oxide film stacked in this order, the MEMS device detecting capacitance formed by the first device substrate, wherein the first device substrate has a movable part configured to be movable apart from the first lid substrate and the second device substrate, the first device substrate and the second device substrate are bonded by direct bonding of the single crystal silicon to each other, and the second device substrate and the second lid substrate are bonded via the silicon oxide film of the second lid substrate, the side of the handle member of the second lid substrate facing the second device substrate is flat, and a cavity is formed in at least a part of a region of the second device substrate facing the second lid substrate that corresponds to the movable part.

[0076] <2> The MEMS device according to <1>, wherein the second device substrate has a first convex portion and a second convex portion protruding toward the second lid substrate, a tip of the first convex portion is bonded to a silicon oxide film of the second lid substrate, and a tip of the second convex portion is spaced apart from the second lid substrate.

[0077] <3> The MEMS device according to <2>, wherein, when the direction in which the first lid substrate, the first device substrate, the second device substrate, and the second lid substrate are stacked is defined as a height direction and a direction intersecting the height direction is defined as a width direction, the height of the second convex portion is equal to the height of the first convex portion, and the width of the second convex portion is smaller than the width of the first convex portion.

[0078] <4> The MEMS device according to <2> or <3>, wherein when a direction intersecting a direction in which the first lid substrate, the first device substrate, the second device substrate, and the second lid substrate are stacked is defined as a width direction, the dimension in the width direction between an end of a surface of the first convex portion facing the handle member and an end of a surface of the silicon oxide film joined to the first convex portion is defined as D1, and the dimension in the width direction of the surface of the second convex portion facing the handle member is defined as W2, the relationship W2≦D1×2 holds.

[0079] <5> The MEMS device according to any one of <2> to <4>, wherein, when the direction in which the first lid substrate, the first device substrate, the second device substrate, and the second lid substrate are stacked is defined as the height direction and the direction intersecting the height direction is defined as the width direction, the first device substrate and the second device substrate are configured to be rotatable about a rotation axis extending in a direction intersecting the height direction and the width direction, and the movable portion has a closest part closest to the first lid substrate on the opposite side of the rotation axis from the second convex portion, with the rotation axis being sandwiched between them, and when the distance in the width direction between the closest part and the rotation axis is defined as L1, the distance in the height direction between the closest part and the first lid substrate is defined as G1, the distance in the width direction between the second convex portion and the rotation axis is defined as L2, and the distance in the height direction between the second convex portion and the second lid substrate is defined as G2, a relationship of G1×L2<G2×L1 holds.

[0080] <6> The MEMS device according to any one of <2> to <5>, wherein, when the direction in which the first lid substrate, the first device substrate, the second device substrate, and the second lid substrate are stacked is defined as the height direction, in a cross section intersecting the height direction and traversing the cavity, the area ratio of the internal space to the area of ​​the MEMS device is 50% or more.

[0081] <7> The MEMS device according to any one of <2> to <6>, wherein, when the direction in which the first lid substrate, the first device substrate, the second device substrate, and the second lid substrate are stacked is defined as the height direction, in a cross section intersecting the height direction and crossing a portion of the second device substrate on the first device substrate side with respect to the cavity, the area ratio of the internal space to the area of ​​the MEMS device is 20% or more.

[0082] <8> The MEMS device according to any one of <1> to <7>, wherein the height of the cavity is 1 μm or more and 50 μm or less when the direction in which the first lid substrate, the first device substrate, the second device substrate, and the second lid substrate are stacked is defined as the height direction.

[0083] <9> A MEMS device comprising a first lid substrate, a first device substrate made of single crystal silicon, a second device substrate made of single crystal silicon, and the second lid substrate having a handle member and a silicon oxide film, stacked in this order, for detecting capacitance formed by the first device substrate, wherein the first device substrate has a movable portion configured to be movable apart from the first lid substrate and the second device substrate, the first device substrate and the second device substrate are bonded by direct bonding of the single crystal silicon to each other, the second device substrate and the second lid substrate are bonded via the silicon oxide film of the second lid substrate, the second device substrate has a first convex portion and a second convex portion protruding toward the second lid substrate, a tip of the first convex portion is bonded to the silicon oxide film of the second lid substrate, and a tip of the second convex portion is spaced apart from the second lid substrate, wherein the height direction is the direction in which the first lid substrate, the first device substrate, the second device substrate, and the second lid substrate are stacked, and the width direction is the direction intersecting the height direction, the height of the second convex portion is equal to the height of the first convex portion, The width of the second protrusion is smaller than the width of the first protrusion.

[0084] <10> A method for manufacturing a MEMS device that detects capacitance formed by a first device substrate, the method including: preparing a first lid substrate; preparing a first device substrate made of single crystal silicon; preparing a second device substrate made of single crystal silicon; preparing a second lid substrate having a handle member and a silicon oxide film; and stacking the first lid substrate, the first device substrate, the second device substrate, and the second lid substrate in this order, wherein the first device substrate includes forming a movable portion that is configured to be movable apart from the first lid substrate and the second device substrate; preparing the second device substrate includes forming a cavity in at least a part of a region corresponding to the movable portion on a side facing the second lid substrate; and stacking the first and second device substrates includes bonding the first and second device substrates by direct bonding of the single crystal silicon together; and bonding the second device substrate and the second lid substrate via the silicon oxide film of the second lid substrate.

[0085] <11> The method for manufacturing a MEMS device according to <10>, further comprising removing a portion of the silicon oxide film of the second lid substrate, wherein preparing the second device substrate comprises forming a first convex portion and a second convex portion protruding toward the second lid substrate, wherein bonding the second device substrate and the second lid substrate comprises bonding a tip of the first convex portion and a tip of the second convex portion to the silicon oxide film of the second lid substrate, and wherein removing a portion of the silicon oxide film of the second lid substrate comprises removing the silicon oxide film bonded to the tip of the second convex portion.

[0086] 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 such as an acceleration sensor or a gyro sensor, or a pressure sensor.

[0087] As described above, according to one aspect of the present invention, it is possible to provide a MEMS device and a manufacturing method thereof that can improve reliability.

[0088] The above-described embodiments are intended to facilitate understanding of the present invention and are not intended to limit the scope of the present invention. The present invention may be modified or improved without departing from its spirit, and such modifications and improvements are also included within the scope of the present invention. In other words, designs modified by those skilled in the art as appropriate are also encompassed within the scope of the present invention as long as they incorporate the characteristics of the present invention. For example, the elements of the embodiments, as well as their arrangement, materials, conditions, shapes, sizes, etc., are not limited to those exemplified and can be modified as appropriate. Furthermore, the elements of the embodiments can be combined to the extent technically possible, and such combinations are also encompassed within the scope of the present invention as long as they incorporate the characteristics of the present invention.

[0089] DESCRIPTION OF SYMBOLS 1...MEMS device 10...first device substrate 11A, 11B...movable space 12A, 12B, 12C...movable portion 14B, 14C...joint portion 18A, 18B...support portion 19...periphery portion 20...second device substrate 21...movable space 24B, 24C...joint portion 28A, 28B...support portion 29...periphery portion 40...first lid substrate 30...second lid substrate PR1, PR2...first convex portion PR3...second convex portion P10, Q10, F10, F20...silicon substrate P11...silicon oxide film Q11...glass substrate

Claims

1. A MEMS device comprising a first lid substrate, a first device substrate made of single crystal silicon, a second device substrate made of single crystal silicon, and a second lid substrate having a handle member and a silicon oxide film, stacked in this order, and detecting capacitance formed by the first device substrate, wherein the first device substrate has a movable part configured to be movable at a distance from the first lid substrate and the second device substrate, the first device substrate and the second device substrate are bonded by direct bonding of the single crystal silicon to each other, and the second device substrate and the second lid substrate are bonded via the silicon oxide film of the second lid substrate, the side of the handle member of the second lid substrate facing the second device substrate is flat, and a cavity is formed in at least a part of a region of the second device substrate facing the second lid substrate that corresponds to the movable part.

2. The MEMS device according to claim 1, wherein the second device substrate has a first convex portion and a second convex portion protruding toward the second lid substrate, the tip of the first convex portion being bonded to the silicon oxide film of the second lid substrate, and the tip of the second convex portion being spaced apart from the second lid substrate.

3. The MEMS device according to claim 2, wherein, when the direction in which the first lid substrate, the first device substrate, the second device substrate, and the second lid substrate are stacked is defined as the height direction and the direction intersecting with the height direction is defined as the width direction, the height of the second convex portion is equal to the height of the first convex portion, and the width of the second convex portion is smaller than the width of the first convex portion.

4. A MEMS device according to claim 2 or 3, wherein, when a direction intersecting the direction in which the first lid substrate, the first device substrate, the second device substrate and the second lid substrate are stacked is taken as the width direction, the dimension in the width direction between the end of the surface of the first convex portion facing the handle member and the end of the surface of the silicon oxide film joined to the first convex portion is taken as D1, and the dimension in the width direction of the surface of the second convex portion facing the handle member is taken as W2, the relationship W2≦D1×2 holds.

5. A MEMS device according to any one of claims 2 to 4, wherein, when the direction in which the first lid substrate, the first device substrate, the second device substrate and the second lid substrate are stacked is defined as a height direction and a direction intersecting the height direction is defined as a width direction, the first device substrate and the second device substrate are configured to be rotatable about a rotation axis extending in a direction intersecting the height direction and the width direction, and the movable portion has a closest part closest to the first lid substrate on the opposite side of the rotation axis from the second convex portion, and when the distance in the width direction between the closest part and the rotation axis is L1, the distance in the height direction between the closest part and the first lid substrate is G1, the distance in the width direction between the second convex portion and the rotation axis is L2, and the distance in the height direction between the second convex portion and the second lid substrate is G2, the relationship G1 x L2 < G2 x L1 holds.

6. A MEMS device according to any one of claims 2 to 5, wherein, when the direction in which the first lid substrate, the first device substrate, the second device substrate and the second lid substrate are stacked is defined as the height direction, in a cross section that intersects with the height direction and cuts across the cavity, the area ratio of the internal space to the area of ​​the MEMS device is 50% or more.

7. A MEMS device according to any one of claims 2 to 6, wherein, when the direction in which the first lid substrate, the first device substrate, the second device substrate and the second lid substrate are stacked is defined as the height direction, in a cross section that intersects with the height direction and that cuts across the portion of the second device substrate on the first device substrate side with respect to the cavity, the area ratio of the internal space to the area of ​​the MEMS device is 20% or more.

8. A MEMS device according to any one of claims 1 to 7, wherein, when the direction in which the first lid substrate, the first device substrate, the second device substrate and the second lid substrate are stacked is taken as the height direction, the height of the cavity is 1 μm or more and 50 μm or less.

9. A MEMS device comprising a first lid substrate, a first device substrate made of single crystal silicon, a second device substrate made of single crystal silicon, and a second lid substrate having a handle member and a silicon oxide film, stacked in this order, for detecting capacitance formed by the first device substrate, wherein the first device substrate has a movable portion configured to be movable at a distance from the first lid substrate and the second device substrate, the first device substrate and the second device substrate are bonded by direct bonding of single crystal silicon to each other, the second device substrate and the second lid substrate are bonded via the silicon oxide film of the second lid substrate, the second device substrate has a first convex portion and a second convex portion protruding toward the second lid substrate, the tip of the first convex portion is bonded to the silicon oxide film of the second lid substrate, and the tip of the second convex portion is spaced apart from the second lid substrate, and when the direction in which the first lid substrate, the first device substrate, the second device substrate, and the second lid substrate are stacked is defined as the height direction and the direction intersecting the height direction is defined as the width direction, A MEMS device, wherein a height of the second protrusion is equal to a height of the first protrusion, and a width of the second protrusion is smaller than a width of the first protrusion.

10. A method for manufacturing a MEMS device that detects capacitance formed by the first device substrate, the method comprising: preparing a first lid substrate; preparing a first device substrate made of single crystal silicon; preparing a second device substrate made of single crystal silicon; preparing a second lid substrate having a handle member and a silicon oxide film; and stacking the first lid substrate, the first device substrate, the second device substrate, and the second lid substrate in this order, wherein the first device substrate includes forming a movable portion that is configured to be movable apart from the first lid substrate and the second device substrate; preparing the second device substrate includes forming a cavity in at least a part of a region corresponding to the movable portion on the side facing the second lid substrate; and stacking the substrates includes bonding the first device substrate and the second device substrate by direct bonding of single crystal silicon together; and bonding the second device substrate and the second lid substrate via the silicon oxide film of the second lid substrate.

11. The method for manufacturing a MEMS device according to claim 10, further comprising removing a portion of the silicon oxide film of the second lid substrate, wherein preparing the second device substrate comprises forming a first convex portion and a second convex portion protruding toward the second lid substrate, wherein bonding the second device substrate and the second lid substrate comprises bonding a tip of the first convex portion and a tip of the second convex portion to the silicon oxide film of the second lid substrate, and wherein removing a portion of the silicon oxide film of the second lid substrate comprises removing the silicon oxide film bonded to the tip of the second convex portion.

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