MEMS device and method for manufacturing MEMS device

Abstract

The present invention is provided with: an upper lid (30); a device layer (10) that is disposed facing the upper lid (30) and that includes movable parts (12, 13); and a joining part (60) that joins the upper lid (30) and the device layer (10) with the space therebetween in a hermetically sealed state. The joining part (60) includes an eutectic metal layer (61), and a height adjustment layer (62) that is laminated on the eutectic metal layer (61) and adjusts the interval between the upper lid (30) and the device layer (10). The height adjustment layer (62) is made of a material having gas permeability, and includes an inner surface (62A) facing the space between the upper lid (30) and the device layer (10), and an outer surface (62B) serving as a surface opposite to the inner surface (62A). The eutectic metal layer (61) is configured to cover at least one of the inner surface (62A) and the outer surface (62B) of the height adjustment layer (62).

Description

MEMS device and method for manufacturing the same

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

[0002] 2. Description of the Related Art Devices manufactured using Micro Electro Mechanical Systems (MEMS) technology have become widespread. These devices are formed by bonding an upper substrate to a lower substrate having elements thereon, for example.

[0003] For example, Patent Document 1 discloses a configuration in which a housing is formed by opposing a base substrate (first substrate) to a cover substrate (second substrate) having a recess in the center of the surface facing the base substrate, the recess of the base substrate and the cover substrate are joined with eutectic solder, and the outer peripheries of both substrates are joined with an insulating film made of silicon nitride (SIN) or the like, thereby hermetically sealing the space between the base substrate and the cover substrate.

[0004] JP 2013-125912 A

[0005] However, in the configuration described in Patent Document 1, since the insulating film has gas permeability, there is still room for improvement in terms of ensuring airtightness of the space between the base substrate and the cover substrate.

[0006] The present invention has been made in consideration of the above circumstances, and aims to provide a MEMS device and a method for manufacturing a MEMS device that can ensure airtightness of the space between a first substrate and a second substrate.

[0007] A MEMS device according to one aspect of the present invention comprises a first substrate, a second substrate arranged opposite the first substrate and including a movable part, and a bonding portion that bonds the first substrate and the second substrate while hermetically sealing the space between them, the bonding portion including a eutectic metal layer and a first height adjustment layer laminated on the eutectic metal layer and adjusting the gap between the first substrate and the second substrate, the first height adjustment layer being made of a gas-permeable material and including an inner surface facing the space between the first substrate and the second substrate and an outer surface opposite the inner surface, and the eutectic metal layer is configured to cover at least one of the inner surface and the outer surface of the first height adjustment layer.

[0008] A method for manufacturing a MEMS device according to one aspect of the present invention includes the steps of placing a first substrate opposite a second substrate including a movable portion, and joining the first substrate and the second substrate via a joint while hermetically sealing the space between them, the joint including a eutectic metal layer and a first height adjustment layer laminated on the eutectic metal layer and adjusting the gap between the first substrate and the second substrate, the first height adjustment layer being made of a gas-permeable material and including an inner surface facing the space between the first substrate and the second substrate and an outer surface opposite the inner surface, and the eutectic metal layer being configured to cover at least one of the inner surface and the outer surface of the first height adjustment layer.

[0009] According to the present invention, the airtightness of the space between the first substrate and the second substrate can be ensured.

[0010] Fig. 1 is a perspective view showing a schematic configuration of a capacitance sensor according to a first embodiment; Fig. 2 is a cross-sectional view of a capacitance sensor according to a first embodiment; Fig. 3 is a cross-sectional view of a capacitance sensor according to a second embodiment; Fig. 4 is a cross-sectional view of a capacitance sensor according to a third embodiment; Fig. 5 is a cross-sectional view of a capacitance sensor according to a fourth embodiment;

[0011] 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.

[0012] <First Embodiment> A first embodiment of the present invention will be described below. In the following description of the drawings, identical or similar components are denoted by identical or similar reference numerals. The drawings are for illustrative purposes only, and the dimensions and shapes of each part are schematic. The technical scope of the present invention should not be interpreted as being limited to this embodiment.

[0013] First, a capacitance-type sensor 1, which is an example of a MEMS device according to a first embodiment of the present invention, will be described with reference to the drawings.

[0014] In the following description, each drawing may be accompanied by a Cartesian coordinate system consisting of X, Y, and Z axes for the purpose of clarifying the relationships between the drawings and helping to understand the positional relationships of the various components. The directions parallel to the X, Y, and Z axes are referred to as the X-axis, Y-axis, and Z-axis directions, respectively. The plane defined by the X and Y axes 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, but the orientation of the capacitance sensor 1 is not limited to this.

[0015] As shown in FIG. 1 , the capacitance sensor 1 is a device manufactured using MEMS technology and is a device for detecting acceleration in, for example, the X-axis, Y-axis, and Z-axis directions. The capacitance sensor 1 includes a bottom cover 20, a device layer 10, and an top cover 30. The bottom cover 20, the device layer 10, and the top cover 30 are stacked in this order in the Z-axis direction. Hereinafter, the stacking direction of the bottom cover 20, the device layer 10, and the top cover 30 will be referred to as the "thickness direction." The device layer 10 and the bottom cover 20 are bonded together to form a MEMS substrate 50. The top cover 30 is bonded to the device layer 10 of the MEMS substrate 50. In other words, the top cover 30 is bonded to the bottom cover 20 via the device layer 10. The bottom cover 20 and the top cover 30 face each other in the thickness direction, with the device layer 10 sandwiched between them. The bottom cover 20 and the top cover 30 form a package structure that forms a vibration space within which the device layer 10 vibrates. The top cover 30 corresponds to an example of a first substrate, and the device layer 10 corresponds to an example of a second substrate.

[0016] As shown in FIG. 2 , the device layer 10 is provided by a silicon substrate F10. The silicon substrate F10 corresponds to an example of a base material of the device layer 10. 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, approximately 10 mΩ·cm. Note that the base material of the device layer 10 is not limited to a silicon semiconductor, and is not particularly limited as long as it is a material that can be thermally oxidized.

[0017] The device layer 10 includes movable portions 12 and 13, spring portions 14 and 15, a support portion 16, and a peripheral portion 17. The device layer 10 also forms a movable space 11 between itself and the top lid 30. The movable space 11 is the range of movement of the movable portion 12 toward the top lid 30, and is a gap in the Z-axis direction between the movable portions 12 and 13 and the top lid 30, surrounded by a peripheral portion 17 in the XY plane direction. The movable portions 12 and 13, the spring portions 14 and 15, the support portion 16, and the peripheral portion 17 are formed by patterning the silicon substrate F10 through removal processing. The removal processing is performed by dry etching, such as DRIE (Deep Reactive Ion Etch). The removal processing may also be performed by other techniques, such as wet etching and laser etching.

[0018] A change in capacitance between the movable parts 12 and 13 is detected based on the distance between them and the top cover 30. The movable parts 12 and 13 correspond to electrodes, with the movable part 12 forming a capacitance with an electrode E1 (described later) of the top cover 30, and the movable part 13 forming a capacitance with an electrode E2 (described later) of the top cover 30. The movable parts 12 and 13 are held so as to be movable up and down and so as to be able to move toward or away from the electrodes E1 and E2 of the top cover 30. When the capacitance-type sensor 1 is subjected to an inertial force (e.g., acceleration or angular velocity) or pressure in the Z-axis direction, the distance in the Z-axis direction between the movable parts 12 and 13 and the top cover 30, i.e., the gap of the movable space 11, changes, and the capacitance formed between the movable part 12 and the top cover 30 changes accordingly. By detecting this change in capacitance, the capacitance-type sensor 1 detects the inertial force or pressure.

[0019] The movable portion 12 and the movable portion 13 are held by spring portions 14 and 15 around the support portion 16 and are configured to be movable up and down. Although not shown in the drawing, the movable portion 12 and the movable portion 13 may be connected in the XY plane without the spring portions 14 and 15. In this case, for example, when a clockwise rotational force is applied when viewed from the negative Y-axis direction with the Y-axis as the rotation axis, the gap between the electrode E1 and the upper surface 12A of the movable portion 12 becomes smaller, and the gap between the electrode E2 and the upper surface 13A of the movable portion 13 becomes larger. When a rotational force is applied in the opposite direction, the gap between the electrode E1 and the upper surface 12A of the movable portion 12 becomes larger, and the gap between the electrode E2 and the upper surface 13A of the movable portion 13 becomes smaller. The rotational force can be detected by the change in capacitance accompanying these gap changes. Note that, unlike the example shown in FIG. 2 , a single movable portion (e.g., the movable portion 12 and the movable portion 13 integrated in FIG. 2 ) may be connected to the peripheral portion 17. In this case, a spring portion may be interposed between the movable portion and the peripheral portion.

[0020] The movable part 12 has an upper surface 12A and a lower surface 12B, and the movable part 13 has an upper surface 13A and a lower surface 13B. The upper surfaces 12A and 13A correspond to first main surfaces of the movable parts 12 and 13, and are provided on the side facing the upper cover 30. The lower surfaces 12B and 13B correspond to second main surfaces of the movable parts 12 and 13, and are provided on the side facing the lower cover 20.

[0021] The lower lid 20 is made up of a silicon substrate P10 and a silicon oxide film P11. The silicon oxide film P11 is provided on the upper surface of the lower lid 20 that is bonded to the device layer 10. The silicon substrate P10 of the lower lid 20 is bonded to the silicon substrate F10 of the device layer 10 via the silicon oxide film P11.

[0022] The lower lid 20 has a bottom plate 22, sidewalls 23, and a fixed portion 24. The bottom plate 22 is spaced apart from the movable portions 12 and 13 in the thickness direction. The bottom plate 22 is a plate-shaped portion having a main surface extending along the XY plane. The bottom plate 22 is formed of a silicon substrate P10. The sidewalls 23 extend from the peripheral edge of the bottom plate 22 toward the upper lid 30. The sidewalls 23 are frame-shaped portions that surround the movable portions 12 and 13 in a plan view. The base ends of the sidewalls 23 that connect to the bottom plate 22 are formed of the silicon substrate P10. A silicon oxide film P11 is provided at the tip ends of the sidewalls 23, and the sidewalls 23 are joined to the peripheral portion 17 of the device layer 10 via the silicon oxide film P11. The lower cover 20 has a movable space 21 surrounded by a bottom plate 22 and a sidewall 23 on the side facing the movable portions 12 and 13 of the device layer 10. The movable space 21 is a rectangular parallelepiped opening that opens toward the movable portions 12 and 13. The fixed portion 24 extends from the bottom plate 22 toward the support portion 16 of the device layer 10. The base end of the fixed portion 24, which connects to the bottom plate 22, is formed by a silicon substrate P10. A silicon oxide film P11 is provided at the tip of the fixed portion 24, and the fixed portion 24 is joined to the support portion 16 via the silicon oxide film P11. The fixed portion 24 fixes the support portion 16. Note that, unlike the example shown in FIG. 2 , neither the support portion 16 nor the fixed portion 24 may be present, such as in an embodiment in which one movable portion is connected to the peripheral portion 17.

[0023] The top cover 30 is flat. The top cover 30 is formed, for example, from a silicon substrate Q10 and a glass substrate Q11. The silicon substrate Q10 is formed, for example, from a p-type silicon (Si) semiconductor. The resistance of the silicon (Si) used in the silicon substrate Q10 is, for example, approximately 10 mΩ·cm. The glass substrate Q11 is formed from glass primarily composed of silicon oxide (e.g., SiO2). Here, the term "main component" refers to a component that accounts for 50% or more by mass of all components constituting the glass. As an example, the glass substrate Q11 is formed from silicate glass primarily composed of SiO2. The silicon substrate Q10 is provided in multiple regions spaced apart from one another in the XY plane. The glass substrate Q11 electrically insulates the multiple silicon substrates Q10 provided in regions spaced apart from one another in the XY plane.

[0024] Electrodes E1 and E2 are provided on the underside of the top cover 30. Electrode E1 forms a capacitance with the movable portion 12, and electrode E2 forms a capacitance with the movable portion 13. Electrode E1 is provided opposite the movable portion 12 in the Z-axis direction, and electrode E2 is provided opposite the movable portion 13 in the Z-axis direction. Electrodes E1 and E2 are provided across the silicon substrate Q10 and the glass substrate Q11. Electrodes E1 and E2 are formed of, for example, aluminum (Al), aluminum-copper alloy (AlCu), titanium (Ti), or titanium-tungsten alloy (TiW).

[0025] Terminals T1, T2, and T3 are provided on the top surface of the upper lid 30. Terminal T1 is electrically connected to electrode E1 via a silicon substrate Q10. Terminal T2 is electrically connected to electrode E2 via the silicon substrate Q10. Terminal T3 is electrically connected to movable parts 12 and 13 via the silicon substrate Q10. Terminals T1, T2, and T3 are electrically insulated from one another by a glass substrate Q11. Terminals T1, T2, and T3 are formed of, for example, aluminum (Al), aluminum-copper alloy (AlCu), titanium (Ti), or titanium-tungsten alloy (TiW).

[0026] The material of the top cover 30 is not limited to the silicon substrate Q10 and the glass substrate Q11. The top cover 30 may include a silicon oxide film instead of the glass substrate Q11, or may further include a silicon oxide film in addition to the silicon substrate Q10 and the glass substrate Q11. The top cover 30 may also be formed using a compound semiconductor substrate, a glass substrate, a ceramic substrate, a resin substrate, or a substrate combining these. Furthermore, through-hole electrodes may be provided that penetrate the top cover 30 in the Z-axis direction to electrically connect the terminal T1 and the electrode E1, and to electrically connect the terminal T2 and the electrode E2. Such through-hole electrodes may be formed, for example, by filling through-holes with polycrystalline silicon (Poly-Si), copper (Cu), gold (Au), or the like.

[0027] A bonding portion 60 is provided between the top lid 30 and the device layer 10. The bonding portion 60 bonds the top lid 30 and the device layer 10 while hermetically sealing the space between them. The space between the top lid 30 and the device layer 10 is, for example, set to a vacuum atmosphere. The bonding portion 60 includes, for example, a eutectic metal layer 61 and a height adjustment layer 62 laminated on the eutectic metal layer 61. The eutectic metal layer 61 is made of a eutectic metal, which is, for example, a mixture of Al and Ge crystals, and has low airtight permeability. Alternatively, the eutectic metal layer 61 may be composed of a combination of one or more metals, such as Al, Au, Ge, Sn, and In. Specifically, the eutectic metal layer 61 may be composed of Al and Si, Au and SiGe, Au and Ge, AuSn and Au, or AuIn and Au. The height adjustment layer 62 is an example of a first height adjustment layer. The height adjustment layer 62 is made of a material different from the material contained in the eutectic metal layer, such as SiO2 or SiN. The height adjustment layer 62 is gas permeable and serves to prevent diffusion of the eutectic metal from the eutectic metal layer 61 to the device layer 10. Furthermore, providing the height adjustment layer 62 reduces the thickness of the eutectic metal layer 61, thereby preventing diffusion of the eutectic metal from the eutectic metal layer 61. Furthermore, the height adjustment layer 62 does not deform during the eutectic bonding process between the top lid 30 and the device layer 10, thereby increasing the gap between the top lid 30 and the device layer 10 and thereby increasing the dynamic range of the capacitance-type sensor 1. The height adjustment layer 62 includes an inner surface 62A facing the space between the top lid 30 and the device layer 10 and an outer surface 62B opposite the inner surface 62A. The eutectic metal layer 61 is configured to cover at least one of the inner surface 62A and the outer surface 62B of the height adjustment layer 62. In this embodiment, the eutectic metal layer 61 is configured to cover the outer surface 62B of the height adjustment layer 62.

[0028] As described above, in the capacitance-type sensor 1 according to this embodiment, the eutectic metal layer 61 is configured to cover the outer surface 62B of the height adjustment layer 62. This ensures airtightness of the space between the top cover 30 and the device layer 10.

[0029] Second Embodiment Next, a capacitance-type sensor 1 as an example of a MEMS device according to a second embodiment of the present invention will be described with reference to the drawings.

[0030] 3 , the eutectic metal layer 61 of the bonding portion 60α according to this embodiment is configured to cover both the inner surface 62A and the outer surface 62B of the height adjustment layer 62. The eutectic metal layer 61 is configured, for example, to cover the entire periphery of the height adjustment layer 62. This allows the eutectic metal layer 61 to have a symmetrical structure with respect to the height direction of the capacitance-type sensor 1 during the eutectic bonding process between the top cover 30 and the device layer 10. This prevents the eutectic metal from spreading over a wide area compared to when the eutectic metal layer 61 has an asymmetrical structure with respect to the height direction of the capacitance-type sensor 1. As a result, electrical shorts in the capacitance-type sensor 1 caused by eutectic metal diffusing from the eutectic metal layer 61 are prevented, ensuring reliable operation of the capacitance-type sensor 1.

[0031] As described above, in the capacitance-type sensor 1 according to this embodiment, the eutectic metal layer 61 is configured to cover both the inner surface 62A and the outer surface 62B of the height adjustment layer 62. This further ensures airtightness of the space between the top cover 30 and the device layer 10.

[0032] Third Embodiment Next, a capacitance-type sensor 1 as an example of a MEMS device according to a third embodiment of the present invention will be described with reference to the drawings.

[0033] As shown in FIG. 4 , the bonding portion 60β according to this embodiment includes, for example, a eutectic metal layer 61, a height adjustment layer 62 stacked on the eutectic metal layer 61, and a height control layer 63 arranged parallel to the height adjustment layer 62 and adjusting the gap between the top lid 30 and the device layer 10. The height control layer 63 includes, for example, a contact layer 64 and a height adjustment layer 65 stacked on the contact layer 64 and adjusting the gap between the top lid 30 and the device layer 10. The contact layer 64 includes a portion of the material contained in the eutectic metal layer 61. The thickness of the contact layer 64 is smaller than the thickness of the eutectic metal layer 61 prior to the eutectic bonding process for bonding the top lid 30 and the device layer 10. This allows the application of a high load required in the eutectic bonding process to be concentrated on the eutectic metal layer 61. As a result, the diffusion of each metal in the eutectic metal layer 61 is promoted, and the eutectic metal layer 61 reliably ensures the airtightness of the space between the top lid 30 and the device layer 10. Furthermore, by using the same material for the contact layer 64 and a portion of the eutectic metal layer 61, material contamination is suppressed. Furthermore, because the contact layer 64 has a higher melting point than the eutectic metal layer 61, the gap between the top cover 30 and the device layer 10 is stably and accurately controlled in a high-temperature environment during the eutectic bonding process. The height adjustment layer 65 is an example of a second height adjustment layer and is made of a material different from the material contained in the eutectic metal layer 61, such as SiO or SiN. By using a material not contained in the eutectic metal layer 61 for the height adjustment layer 65, interdiffusion of a portion of the height adjustment layer 65 with the eutectic metal layer 61 during the eutectic bonding process is suppressed, thereby improving the yield of the capacitance-type sensor 1. Furthermore, by using a Si-based material, which is the material of the device layer 10, for the height adjustment layer 65, it is easy to ensure adhesion with the device layer 10 and also suppress melting of the eutectic metal from the eutectic metal layer 61. This further ensures airtightness of the space between the upper cover 30 and the device layer 10. The materials and manufacturing processes of the height control layer 65 and the height adjustment layer 62 are not particularly limited, and for example, the height adjustment layer 65 and the height adjustment layer 62 may be produced using the same material at the same time.

[0034] As described above, in the capacitance-type sensor 1 according to this embodiment, the joint 60β further includes a height control layer 63 that is provided in parallel with the height adjustment layer 62 and adjusts the gap between the top lid 30 and the device layer 10. Therefore, the application of a high load required in the eutectic bonding process between the top lid 30 and the device layer 10 can be concentrated on the eutectic metal layer 61, promoting the diffusion of each metal in the eutectic metal layer 61. This further ensures the airtightness of the space between the top lid 30 and the device layer 10.

[0035] Fourth Embodiment Next, a capacitance-type sensor 1 as an example of a MEMS device according to a fourth embodiment of the present invention will be described with reference to the drawings.

[0036] As shown in FIG. 5 , the capacitance-type sensor 1 according to this embodiment further includes a wiring layer 66 made of a eutectic metal between the top cover 30 and the device layer 10. The wiring layer 66 includes a wiring portion extending along the height direction of the capacitance-type sensor 1 and a wiring portion extending along a plane intersecting the height direction of the capacitance-type sensor 1. By providing the wiring layer 66 made of a eutectic metal between the top cover 30 and the device layer 10, an increase in electrical resistance due to contact resistance between the top cover 30 and the device layer 10 is suppressed. Furthermore, by further including a height control layer 63 that adjusts the gap between the top cover 30 and the device layer 10, the application of a high load required in the eutectic bonding process between the top cover 30 and the device layer 10 can be concentrated on the eutectic metal layer 61, thereby suitably controlling the eutectic state of the wiring layer 66 during the eutectic bonding process between the top cover 30 and the device layer 10. This allows for highly reliable wiring between the top cover 30 and the device layer 10.

[0037] As described above, the capacitance-type sensor 1 according to this embodiment further includes a wiring layer 66 made of a eutectic metal between the top cover 30 and the device layer 10. This makes it possible to suppress an increase in electrical resistance due to contact resistance between the top cover 30 and the device layer 10.

[0038] 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.

[0039] <1> A MEMS device comprising: a first substrate; a second substrate disposed opposite the first substrate and including a movable portion; and a bonding portion that bonds the first substrate and the second substrate while hermetically sealing a space between them, wherein the bonding portion includes: a eutectic metal layer; and a first height adjustment layer that is laminated on the eutectic metal layer and adjusts the gap between the first substrate and the second substrate, wherein the first height adjustment layer is made of a gas-permeable material and includes an inner surface that faces the space between the first substrate and the second substrate and an outer surface that is the surface opposite the inner surface, and the eutectic metal layer is configured to cover at least one of the inner surface and the outer surface of the first height adjustment layer.

[0040] <2> The MEMS device according to <1>, wherein the eutectic metal layer is configured to cover both the inner surface and the outer surface of the first height adjustment layer.

[0041] <3> The MEMS device according to <1> or <2>, wherein the first height adjustment layer is made of a material different from a material contained in the eutectic metal layer.

[0042] <4> The MEMS device according to <3>, wherein the first height adjustment layer is made of SiO 2 or SiN.

[0043] <5> The MEMS device according to any one of <1> to <4>, wherein the junction further includes a height control layer provided in parallel with the first height adjustment layer and adjusting the gap between the first substrate and the second substrate, and the height control layer includes: a contact layer; and a second height adjustment layer stacked on the contact layer and adjusting the gap between the first substrate and the second substrate.

[0044] <6> The MEMS device according to <5>, wherein the contact layer contains a part of a material contained in the eutectic metal layer.

[0045] <7> The MEMS device according to <5> or <6>, wherein the second height adjustment layer is made of a material different from a material contained in the eutectic metal layer.

[0046] <8> The MEMS device according to claim 7, wherein the second height adjustment layer is made of SiO2 or SiN.

[0047] <9> The MEMS device according to any one of <1> to <8>, further comprising a wiring layer made of a eutectic metal between the first substrate and the second substrate.

[0048] <10> A method for manufacturing a MEMS device, comprising: a step of placing a first substrate opposite a second substrate including a movable portion; and a step of bonding the first substrate and the second substrate via a bonding portion while hermetically sealing a space between the first substrate and the second substrate, wherein the bonding portion comprises: a eutectic metal layer; and a first height adjustment layer laminated on the eutectic metal layer and adjusting the gap between the first substrate and the second substrate, wherein the first height adjustment layer is made of a gas-permeable material and includes an inner surface facing the space between the first substrate and the second substrate and an outer surface opposite the inner surface, and the eutectic metal layer is configured to cover at least one of the inner surface and the outer surface of the first height adjustment layer.

[0049] <11> The method for manufacturing a MEMS device according to <10>, wherein the bonding portion further includes a height control layer provided in parallel with the first height adjustment layer and adjusting the gap between the first substrate and the second substrate, the height control layer including: a contact layer; and a second height adjustment layer stacked on the contact layer and adjusting the gap between the first substrate and the second substrate, and the thickness of the contact layer is smaller than the thickness of the eutectic metal layer before bonding the first substrate and the second substrate.

[0050] As described above, according to one aspect of the present invention, it is possible to provide a MEMS device and a method for manufacturing a MEMS device that can ensure airtightness of the space between the first substrate and the second substrate.

[0051] 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 equivalents 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 and their arrangements, materials, conditions, shapes, sizes, etc. of the embodiments are not limited to those illustrated and can be modified as appropriate. Furthermore, the embodiments are merely examples, and partial substitutions or combinations of the configurations shown in different embodiments are naturally possible. These are also encompassed within the scope of the present invention as long as they incorporate the characteristics of the present invention.

[0052] 1...capacitive sensor, 10...device layer (an example of a second substrate), 12, 13...movable part, 20...lower cover, 30...upper cover (an example of a first substrate), 50...MEMS substrate, 60, 60α, 60β...joint, 61...eutectic metal layer, 62...height adjustment layer (an example of a first height adjustment layer), 62A...inner surface, 62B...outer surface, 63...height control layer, 64...contact layer, 65...height adjustment layer (an example of a second height adjustment layer), 66...wiring layer.

Claims

1. A MEMS device comprising: a first substrate; a second substrate arranged opposite the first substrate and including a movable portion; and a bonding portion that bonds the first substrate and the second substrate while hermetically sealing the space between them, wherein the bonding portion includes a eutectic metal layer and a first height adjustment layer that is laminated on the eutectic metal layer and adjusts the gap between the first substrate and the second substrate, wherein the first height adjustment layer is made of a gas permeable material and includes an inner side facing the space between the first substrate and the second substrate and an outer side opposite the inner side, and the eutectic metal layer is configured to cover at least one of the inner side and the outer side of the first height adjustment layer.

2. The MEMS device according to claim 1, wherein the eutectic metal layer is configured to cover both the inner and outer surfaces of the first height adjustment layer.

3. The MEMS device according to claim 1 or 2, wherein the first height adjustment layer is made of a material different from a material contained in the eutectic metal layer.

4. The MEMS device according to claim 3, wherein the first height adjustment layer is made of SiO2 or SiN.

5. A MEMS device as described in any one of claims 1 to 4, wherein the junction further includes a height control layer arranged in parallel with the first height adjustment layer and adjusting the gap between the first substrate and the second substrate, and the first height control layer includes: a contact layer; and a second height adjustment layer stacked on the contact layer and adjusting the gap between the first substrate and the second substrate.

6. The MEMS device according to claim 5, wherein the contact layer includes a portion of the material contained in the eutectic metal layer.

7. The MEMS device according to claim 5 or 6, wherein the second height adjustment layer is made of a material different from a material contained in the eutectic metal layer.

8. The MEMS device according to claim 7, wherein the second height adjustment layer is made of SiO2 or SiN.

9. The MEMS device according to claim 1, further comprising a wiring layer made of a eutectic metal between the first substrate and the second substrate.

10. A method for manufacturing a MEMS device, comprising: a step of placing a first substrate opposite a second substrate including a movable part; and a step of bonding the first substrate and the second substrate via a bonding part while hermetically sealing the space between them, wherein the bonding part comprises: a eutectic metal layer; and a first height adjustment layer laminated on the eutectic metal layer and adjusting the gap between the first substrate and the second substrate, wherein the first height adjustment layer is made of a gas permeable material and includes an inner side facing the space between the first substrate and the second substrate and an outer side opposite the inner side, and the eutectic metal layer is configured to cover at least one of the inner side and the outer side of the first height adjustment layer.

11. A method for manufacturing a MEMS device as described in claim 10, wherein the bonding portion further includes a height control layer arranged in parallel to the first height adjustment layer and adjusting the gap between the first substrate and the second substrate, the height control layer including: a contact layer; and a second height adjustment layer stacked on the contact layer and adjusting the gap between the first substrate and the second substrate, and the thickness of the contact layer is smaller than the thickness of the eutectic metal layer prior to bonding the first substrate and the second substrate.

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