MEMS device

Abstract

To improve sensitivity in a MEMS device.SOLUTION: A MEMS device comprises: a substrate in which a cavity is disposed; and a MEMS electrode that is disposed within the cavity and spaced apart from a bottom surface of the cavity. The MEMS electrode includes: a movable electrode finger that is relatively movable with respect to the substrate; a fixed electrode finger disposed at an interval from the movable electrode finger so as to face the movable electrode finger; a beam portion that is cantilevered on the substrate and connects the fixed electrode finger to the substrate; and an electrode portion configured to, when voltage is applied, deform the beam portion by electrostatic force, and make an interval between the movable electrode finger and the fixed electrode finger narrower than the interval formed before the deformation of the beam portion. The electrode portion includes: a first electrode finger connected to the beam portion; and a second electrode finger disposed at an interval from the first electrode finger so as to face the first electrode finger, disposed toward the fixed electrode finger with respect to the first electrode finger, and fixed to the substrate.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to MEMS devices. [Background technology]

[0002] Patent Document 1 discloses a capacitive MEMS (Micro Electro Mechanical System) sensor having fixed and movable electrodes that face each other and mesh with each other like comb teeth. The fixed and movable electrodes described in Patent Document 1 are formed by etching a semiconductor substrate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2023-020325

[0004] [overview] In general, in a capacitance-type MEMS sensor, the narrower the gap between the movable electrode and the fixed electrode, the higher the sensitivity. However, since there is a limit to the aspect ratio of etching, the deeper the etching, the wider the gap between the movable electrode and the fixed electrode. In other words, when etching the gap between the movable electrode and the fixed electrode to a predetermined depth, it is difficult to make the gap between the fixed electrode and the movable electrode narrower than a certain gap. Patent Document 1 does not describe the gap between the fixed electrode and the movable electrode, and there is room for improvement in terms of improving sensitivity.

[0005] The present disclosure aims to improve the sensitivity of MEMS devices.

[0006] One aspect of the present disclosure is A substrate having a first main surface and a second main surface opposite to the first main surface, and a cavity recessed from the first main surface side to the second main surface side is disposed therein; a MEMS electrode disposed within the cavity and spaced apart from a bottom surface of the cavity toward the first principal surface; Equipped with The MEMS electrode is a movable electrode finger extending in a first direction and connected to the substrate so as to be movable relative to the substrate; fixed electrode fingers extending in the first direction and arranged at intervals from the movable electrode fingers so as to face the movable electrode fingers in a second direction intersecting the first direction; a beam portion that is cantilevered on the substrate and connects the fixed electrode finger to the substrate; an electrode section configured such that, when a voltage is applied, the beam section is deformed by electrostatic force, and a gap between the movable electrode finger and the fixed electrode finger in the second direction becomes narrower than a gap before the beam section is deformed; Equipped with The electrode portion is a first electrode finger extending in the first direction and connected to the beam portion; a second electrode finger extending in the first direction, arranged at a distance from the first electrode finger so as to face the first electrode finger in the second direction, arranged on the fixed electrode finger side relative to the first electrode finger in the second direction, and fixed to the substrate; The present invention provides a MEMS device comprising: [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a plan view of an acceleration sensor according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Diagram 3] FIG. 3 is a plan view of the acceleration sensor of FIG. 1 with a voltage applied thereto. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. [Diagram 5] FIG. 5 is a plan view of an acceleration sensor according to a modified example of the embodiment of the present disclosure.

[0008] [Detailed Description] Hereinafter, a MEMS device according to an embodiment of the present disclosure will be described with reference to the accompanying drawings. Note that the following description is essentially merely illustrative and is not intended to limit the present disclosure, its applications, or its uses. Also, the drawings are schematic, and the ratios of dimensions, etc. differ from the actual ones.

[0009] [Accelerometer] Fig. 1 is a plan view that shows a schematic diagram of an acceleration sensor 1 according to an embodiment of the present disclosure. Fig. 2 is a cross-sectional view taken along line II-II in Fig. 1. The acceleration sensor 1 according to this embodiment is a capacitance type acceleration sensor manufactured using semiconductor microfabrication technology. The acceleration sensor 1 according to this embodiment is an example of a MEMS (Micro Electro Mechanical System) device according to the present disclosure.

[0010] In the following description, for convenience, among the directions along each side of the acceleration sensor 1 in the plan view shown in FIG. 1, the left-right direction in FIG. 1 is referred to as the X direction, the up-down direction in FIG. 1 is referred to as the Y direction, and the thickness direction of the acceleration sensor 1 in the cross-sectional view shown in FIG. 2 (the up-down direction in FIG. 2) is referred to as the Z direction. In particular, the right side in FIG. 1 may be referred to as the +X direction, the left side as the -X direction, the upper side as the +Y direction, and the lower side as the -Y direction. In FIG. 2, the upper side may be referred to as the +Z direction, and the lower side as the -Z direction. In this embodiment, the X direction, the Y direction, and the Z direction are mutually orthogonal. The X direction according to this embodiment is an example of a second direction according to the present disclosure. The Y direction according to this embodiment is an example of a first direction according to the present disclosure.

[0011] 1 and 2, the acceleration sensor 1 includes a substrate 10 and a MEMS electrode 20 provided in the substrate 10. As shown in FIG.

[0012] The substrate 10 has a rectangular shape in plan view. The substrate 10 has a first main surface 10a located on the +Z side and a second main surface 10b located on the -Z side and facing the first main surface 10a. The substrate 10 is a conductive silicon (Si) substrate. The substrate 10 of this embodiment is made of only a single silicon layer. The first main surface 10a and the second main surface 10b are planar extending in the X direction and the Y direction. The first main surface 10a and the second main surface 10b extend in parallel. An insulating layer 11 is disposed on the first main surface 10a of the substrate 10. The substrate 10 has a cavity 12 formed therein that is rectangular in plan view and recessed from the first main surface 10a toward the -Z side.

[0013] The substrate 10 has four inner wall surfaces 13A-13D that define the cavity 12 in the X and Y directions. In the following description, when there is no need to particularly distinguish between the four inner wall surfaces 13A-13D, one of the four inner wall surfaces 13A-13D may be simply referred to as inner wall surface 13.

[0014] The inner wall surface 13A is a flat surface extending in the X and Z directions, and defines the −Y side of the cavity 12.

[0015] The inner wall surface 13B is a flat surface extending in the Y and Z directions, and defines the +X side of the cavity 12.

[0016] The inner wall surface 13C is a flat surface extending in the X and Z directions, and defines the +Y side of the cavity 12.

[0017] The inner wall surface 13D is a flat surface extending in the Y and Z directions, and defines the −X side of the cavity 12.

[0018] The MEMS electrode 20 includes a movable electrode 30 and a fixed electrode 40. The movable electrode 30 and the fixed electrode 40 are disposed within the cavity 12.

[0019] The movable electrode 30 is spaced from the bottom surface 12a of the cavity 12 on the +Z side. The movable electrode 30 includes movable electrode fingers 31 extending in the Y direction, a base 32 to which +Y side ends of the movable electrode fingers 31 are connected, and two spring portions 33A and 33B that connect the base 32 to the substrate 10. In the following description, when there is no need to particularly distinguish between the spring portions 33A and 33B, one of the two spring portions 33A and 33B may be simply referred to as the spring portion 33.

[0020] The movable electrode finger 31 includes a conductive silicon (Si) layer. The movable electrode finger 31 is connected to the substrate 10 so as to be movable in the X direction relative to the substrate 10. The movable electrode finger 31 is connected to the substrate 10 via a base portion 32 and spring portions 33A and 33B. The movable electrode finger 31 of this embodiment is indirectly supported by the inner wall surface 13B and the inner wall surface 13D via the base portion 32 and the spring portions 33A and 33B.

[0021] The base 32 includes a conductive silicon (Si) layer. The base 32 functions as a proof mass of the acceleration sensor 1. The base 32 is connected to the substrate 10 so as to be movable in the X direction relative to the substrate 10. Specifically, the base 32 is connected to the substrate 10 via spring portions 33A and 33B. The base 32 is indirectly supported by the inner wall surfaces 13B and 13D via the spring portions 33A and 33B.

[0022] The spring portion 33 includes a conductive silicon (Si) layer. The spring portion 33 is cantilevered on the inner wall surface 13 of the substrate 10 extending in the Y and Z directions. Specifically, the spring portion 33A is cantilevered on the inner wall surface 13D of the substrate 10, and the spring portion 33B is cantilevered on the inner wall surface 13B of the substrate 10. The spring portion 33 protrudes into the cavity 12 from the inner wall surface 13 of the substrate 10 extending in the Y and Z directions. The spring portions 33A and 33B are disposed on the -X side and +X side of the base portion 32, respectively. The spring portion 33 is configured to be expandable and contractable in the X direction. When acceleration in the X direction acts on the base portion 32, the spring portions 33A and 33B are elastically deformed, and the movable electrode finger 31 is displaced in the X direction.

[0023] The movable electrode 30 has an isolation joint 34 that crosses the spring portion 33 in the Y and Z directions and divides it in the X direction. The isolation joint 34 mechanically connects both sides of the spring portion 33 divided in the X direction by the isolation joint 34, while electrically insulating them. The isolation joint 34 electrically insulates the movable electrode finger 31 from the substrate 10. The isolation joint 34 in this embodiment is made of silicon oxide (SiO2).

[0024] The fixed electrode 40 is spaced from the bottom surface 12a of the cavity 12 on the +Z side. The fixed electrode 40 includes two fixed electrode fingers 41A, 41B extending in the Y direction, and two beam portions 42A, 42B connecting the two fixed electrode fingers 41A, 41B to the substrate 10, respectively. In the following description, when there is no need to particularly distinguish between the two fixed electrode fingers 41A, 41B, one of the two fixed electrode fingers 41A, 41B may be simply referred to as the fixed electrode finger 41. Similarly, in the following description, when there is no need to particularly distinguish between the two beam portions 42A, 42B, one of the two beam portions 42A, 42B may be simply referred to as the beam portion 42.

[0025] The fixed electrode finger 41 includes a conductive silicon (Si) layer. The two fixed electrode fingers 41A, 41B extend in the Y direction and are arranged side by side in the X direction. The two fixed electrode fingers 41A, 41B are arranged with the movable electrode finger 31 sandwiched between them in the X direction. The fixed electrode finger 41 is arranged facing the movable electrode finger 31 in the X direction. The fixed electrode finger 41 is arranged with a gap G1 between it and the movable electrode finger 31 in the X direction. The fixed electrode finger 41 in this embodiment is indirectly supported by the inner wall surface 13A via the beam portion 42.

[0026] The beam portion 42 connects the fixed electrode finger 41 to the inner wall surface 13A of the substrate 10. The beam portion 42 is cantilevered on the inner wall surface 13A of the substrate 10. The beam portion 42 extends from the inner wall surface 13A of the substrate 10, which extends in the X and Z directions, into the cavity 12. The beam portion 42 includes a first end portion 42a connected to the substrate 10 and a second end portion 42b connected to the +Y side end portion of the fixed electrode finger 41. The beam portion 42 includes a first beam 43 extending from the first end portion 42a toward the +Y side in a plan view, and a second beam 44 extending from the +Y side end portion of the first beam 43 toward the movable electrode finger 31 in the X direction. That is, the beam portion 42 of this embodiment is substantially L-shaped in a plan view.

[0027] The first beam 43 includes a conductive silicon (Si) layer. The first beam 43 is arranged alongside the fixed electrode finger 41 in the X direction. Specifically, in the beam portion 42A, the first beam 43 is arranged on the -X side of the fixed electrode finger 41A, and in the beam portion 42B, the first beam 43 is arranged on the +X side of the fixed electrode finger 41B. The first beam 43 of this embodiment extends linearly from the first end portion 42a towards the +Y side.

[0028] The second beam 44 includes a conductive silicon (Si) layer. The second beam 44 extends linearly in the X direction so as to connect the +Y side end of the first beam 43 and the +Y side end of the fixed electrode finger 41.

[0029] Beam portion 42 has an isolation joint 45 that crosses first beam 43 in the X and Z directions and divides it in the Y direction. Isolation joint 45 mechanically connects both sides of beam portion 42 divided in the Y direction by isolation joint 45, while electrically insulating them. Fixed electrode finger 41 and substrate 10 are electrically insulated by isolation joint 45. Isolation joint 45 in this embodiment is made of silicon oxide (SiO2).

[0030] The MEMS electrode 20 includes two electrode portions 50A, 50B configured such that, when a voltage is applied, the beam portion 42 is deformed by electrostatic force, and the distance between the movable electrode fingers 31 and the fixed electrode fingers 41 in the X direction becomes narrower than before the deformation of the beam portion 42. In the following description, when there is no need to particularly distinguish between the two electrode portions 50A, 50B, one of the two electrode portions 50A, 50B may be simply referred to as the electrode portion 50.

[0031] The electrode unit 50 includes a first electrode finger 51 extending in the Y direction, and a second electrode finger 52 extending in the Y direction and arranged at a distance from the first electrode finger 51 so as to face the first electrode finger 51 in the X direction. The electrode unit 50A is arranged to be sandwiched between the fixed electrode finger 41A and the first beam 43 of the beam unit 42A in the X direction. The electrode unit 50B is arranged to be sandwiched between the fixed electrode finger 41B and the first beam 43 of the beam unit 42B in the X direction.

[0032] The first electrode finger 51 includes a conductive silicon (Si) layer. The first electrode finger 51 is connected to the beam portion 42. In detail, the +Y side end of the first electrode finger 51 is connected to the second beam 44 of the beam portion 42. The first electrode finger 51 extends linearly from the second beam 44 toward the -Y side. The first electrode finger 51 is arranged side by side with the first beam 43 in the X direction. The first electrode finger 51 is electrically connected to the fixed electrode finger 41.

[0033] The second electrode finger 52 includes a conductive silicon (Si) layer. The second electrode finger 52 is fixed to the substrate 10. In detail, the second electrode finger 52 is supported by an inner wall surface 13A of the substrate 10. The second electrode finger extends linearly from the inner wall surface 13A of the substrate 10 toward the +Y side. The second electrode finger 52 is arranged side by side with the first electrode finger 51 in the X direction. The second electrode finger 52 is arranged on the fixed electrode finger 41 side with respect to the first electrode finger 51 in the X direction. In other words, the second electrode finger 52 is arranged between the first electrode finger 51 and the fixed electrode finger 41 in the X direction.

[0034] The electrode unit 50 has an isolation joint 53 that crosses the second electrode finger 52 in the X and Z directions and divides it in the Y direction. The isolation joint 53 mechanically connects both sides of the second electrode finger 52 that are divided in the X direction by the isolation joint 53, while electrically insulating them. The isolation joint 53 electrically insulates the second electrode finger 52 from the substrate 10. The isolation joint 53 in this embodiment is made of silicon oxide (SiO2).

[0035] When different voltages are applied to the first electrode finger 51 and the second electrode finger 52, an electrostatic force acts on the first electrode finger 51 and the second electrode finger 52, attracting each other. As a result, the beam portion 42 is deformed so as to displace the first electrode finger 51 closer to the second electrode finger 52. Due to this deformation of the beam portion 42, the fixed electrode finger 41 is displaced closer to the movable electrode finger 31.

[0036] In this embodiment, a distance L1 between the first electrode finger 51 and the second electrode finger 52 in the X direction is shorter than a distance L2 between the second electrode finger 52 and the fixed electrode finger 41 in the X direction.

[0037] The acceleration sensor 1 includes a restricting portion 60 supported by the substrate 10. When the beam portion 42 of the fixed electrode 40 is deformed by electrostatic force and the fixed electrode fingers 41 are displaced toward the movable electrode fingers 31 by a predetermined distance or more, the restricting portion 60 comes into contact with the fixed electrode fingers 41 to restrict the displacement of the fixed electrode fingers 41. In this way, the restricting portion 60 maintains the distance between the movable electrode fingers 31 and the fixed electrode fingers 41 at a predetermined distance (shown in FIG. 3).

[0038] The restricting portion 60 includes a main body 61 extending in the Y direction, and two protruding portions 62A, 62B protruding from the main body 61 on both sides in the X direction. When there is no need to particularly distinguish between the two protruding portions 62A, 62B, one of the two protruding portions 62A, 62B may be simply referred to as a protruding portion 62.

[0039] The main body 61 includes a conductive silicon (Si) layer. The main body 61 is supported on an inner wall surface 13A of the substrate 10. The main body 61 protrudes into the cavity 12 from the inner wall surface 13A of the substrate 10, which extends in the X direction and the Z direction.

[0040] The protrusion 62 includes a conductive silicon (Si) layer. The protrusion 62A protrudes from the +Y side end of the main body 61 to the -X side, and the protrusion 62B protrudes from the +Y side end of the main body 61 to the +X side.

[0041] The restricting portion 60 has an isolation joint 63 that crosses the protruding portion 62 in the Y and Z directions and divides it in the X direction. The isolation joint 63 mechanically connects both sides of the protruding portion 62 divided in the X direction by the isolation joint 63, while electrically insulating them. The isolation joint 63 electrically insulates the portion of the protruding portion 62 facing the fixed electrode finger 41 from the substrate 10. The isolation joint 63 in this embodiment is made of silicon oxide (SiO2).

[0042] In this embodiment, a distance L3 between the fixed electrode finger 41 and the restriction portion 60 in the X direction is shorter than a distance L1 between the first electrode finger 51 and the second electrode finger 52 in the X direction.

[0043] The acceleration sensor 1 includes electrode pads 70 to 73 for inputting and outputting electrical signals (voltage) to and from the MEMS electrode 20, and an electrode pad 74 for inputting an electrical signal to the substrate 10. The electrode pads 70 to 74 are disposed on the insulating layer 11.

[0044] The electrode pad 70 is electrically connected to the movable electrode 30 via a wiring layer 80. The wiring layer 80 is electrically insulated from the substrate 10 by an insulating layer 11. An output voltage is output from the electrode pad 70 in accordance with changes in the electrostatic capacitance of a first capacitor C1 and a second capacitor C2, which will be described later.

[0045] The electrode pad 71 is electrically connected to the fixed electrode finger 41A via the wiring layer 81. A first input voltage, which is an AC voltage, is applied to the electrode pad 71. As a result, the first input voltage is applied to the fixed electrode finger 41A, the beam portion 42A, and the first electrode finger 51 of the electrode portion 50A. The electrode pad 71 in this embodiment is electrically connected to the ground potential, and the first input voltage is 0 [V]. The wiring layer 81 is electrically insulated from the substrate 10 by the insulating layer 11.

[0046] The electrode pad 72 is electrically connected to the fixed electrode finger 41B via the wiring layer 82. A second input voltage, which is an AC voltage, is applied to the electrode pad 72. As a result, the second input voltage is applied to the fixed electrode finger 41B, the beam portion 42B, and the first electrode finger 51 of the electrode portion 50B. The second input voltage in this embodiment is a power supply voltage (V DD The wiring layer 82 is electrically insulated from the substrate 10 by the insulating layer 11.

[0047] The electrode pad 73 is electrically connected to the second electrode finger 52 of the electrode unit 50A via the wiring layer 83, and is electrically connected to the second electrode finger 52 of the electrode unit 50B via the wiring layer 84. A third input voltage, which is an AC voltage, is applied to the electrode pad 73. As a result, the third input voltage is applied to the second electrode finger 52 of the electrode unit 50A and the second electrode finger 52 of the electrode unit 50B. The electrode pad 73 of this embodiment is electrically connected to an intermediate potential between the potential of the electrode pad 71 and the potential of the electrode pad 72, and the third input voltage is V DD / 2[V].

[0048] The electrode pads 74 are electrically connected to the substrate 10 via a wiring layer 85 .

[0049] Clock signals of opposite phases are applied to the two fixed electrode fingers 41A, 41B. Furthermore, a clock signal synchronized with the clock signal applied to the two fixed electrode fingers 41A, 41B is applied to the second electrode fingers 52 of each of the two electrode portions 50A, 50B.

[0050] [Accelerometer 1 with voltage applied] Fig. 3 is a schematic plan view of the acceleration sensor 1 in a state in which a voltage is applied. Fig. 4 is a cross-sectional view taken along line IV-IV in Fig. 3. Figs. 3 and 4 show the acceleration sensor 1 in a state in which a first input voltage is applied to the fixed electrode fingers 41A, the beam portion 42A, and the first electrode fingers 51 of the electrode portion 50A, a second input voltage is applied to the fixed electrode fingers 41B, the beam portion 42B, and the first electrode fingers 51 of the electrode portion 50B, and a third input voltage is applied to the second electrode fingers 52 of each of the two electrode portions 50A and 50B.

[0051] In the state shown in FIG. 3, a first input voltage is applied to the first electrode finger 51 of the electrode unit 50A, and a third input voltage is applied to the second electrode finger 52 of the electrode unit 50A. In the electrode unit 50A, different voltages are applied to the first electrode finger 51 and the second electrode finger 52, so that an electrostatic force that attracts each other acts on the first electrode finger 51 and the second electrode finger 52. Due to this electrostatic force, the beam portion 42A is deformed so that the first electrode finger 51 of the electrode unit 50A is displaced to the +X side. In detail, the first beam 43 of the beam portion 42A is deformed so as to be curved from the first end portion 42a toward the +Y side toward the fixed electrode finger 41A side, that is, the +X side. Due to this deformation of the first beam 43 of the beam portion 42A, the fixed electrode finger 41A is displaced to the +X side so as to approach the movable electrode finger 31.

[0052] In the state shown in FIG. 3, a second input voltage is applied to the first electrode finger 51 of the electrode unit 50B, and a third input voltage is applied to the second electrode finger 52 of the electrode unit 50B. In the electrode unit 50B, different voltages are applied to the first electrode finger 51 and the second electrode finger 52, so that an electrostatic force that attracts each other acts on the first electrode finger 51 and the second electrode finger 52. Due to this electrostatic force, the beam portion 42B is deformed so that the first electrode finger 51 of the electrode unit 50B is displaced to the -X side. In detail, the first beam 43 of the beam portion 42B is deformed so as to be curved from the first end portion 42a toward the +Y side toward the fixed electrode finger 41B side, that is, the -X side. Due to this deformation of the first beam 43 of the beam portion 42B, the fixed electrode finger 41B is displaced to the -X side so as to approach the movable electrode finger 31.

[0053] 3, a gap G2 between movable electrode finger 31 and fixed electrode finger 41 when a voltage is applied is narrower than a gap G1 (shown in FIG. 1) between movable electrode finger 31 and fixed electrode finger 41 before beam portion 42 is deformed. Furthermore, since displacement of fixed electrode finger 41 by more than a predetermined distance is restricted by restricting portion 60, gap G2 between movable electrode finger 31 and fixed electrode finger 41 is maintained at a predetermined gap. In this embodiment, the aspect ratio of the space between movable electrode finger 31 and fixed electrode finger 41 when a voltage is applied, that is, the ratio D / G2 of the depth D (shown in FIG. 4) of movable electrode finger 31 and fixed electrode finger 41 to gap G2 in the X direction between movable electrode finger 31 and fixed electrode finger 41, that is, the dimension in the Z direction, is, for example, 100 or more.

[0054] In the acceleration sensor 1 of this embodiment, a first capacitor C1 is formed by the movable electrode finger 31 and the fixed electrode finger 41A arranged adjacent to the movable electrode finger 31 on the -X side. A second capacitor C2 is formed by the movable electrode finger 31 and the fixed electrode finger 41B arranged adjacent to the movable electrode finger 31 on the +X side.

[0055] When acceleration in the X direction acts on the acceleration sensor 1, the movable electrode finger 31 moves in the X direction relative to the fixed electrode 40. The acceleration sensor 1 is configured to be able to detect acceleration by extracting, as an electric signal, from the electrode pad 70, a change in electrostatic capacitance in each of the first capacitor C1 and the second capacitor C2 that accompanies the displacement of the movable electrode 30 in the X direction when acceleration acts.

[0056] [effect] When etching between the movable electrode fingers 31 and the fixed electrode fingers 41, the aspect ratio of the etching is limited, so the interval between the movable electrode fingers 31 and the fixed electrode fingers 41 becomes wider according to the depth of the etching. In other words, when etching between the movable electrode fingers 31 and the fixed electrode fingers 41 to a predetermined depth, it is difficult to make the interval between the fixed electrode fingers 41 and the movable electrode fingers 31 narrower than a certain interval. In contrast, according to this configuration, when different voltages are applied to the first electrode fingers 51 and the second electrode fingers 52 of the electrode unit 50, an electrostatic force that attracts the first electrode fingers 51 and the second electrode fingers 52 acts on them. This electrostatic force causes the beam portion 42 to deform so that the first electrode fingers 51 are displaced closer to the second electrode fingers 52. This deformation of beam portion 42 displaces fixed electrode finger 41 so as to approach movable electrode finger 31, and the gap G2 between movable electrode finger 31 and fixed electrode finger 41 when a voltage is applied can be made narrower than the gap G1 before beam portion 42 is deformed. This makes it possible to make gap G2 between movable electrode finger 31 and fixed electrode finger 41 narrower than gap G1 formed between fixed electrode finger 41 and movable electrode finger 31 by etching to form fixed electrode finger 41 and movable electrode finger 31. As a result, the gap between fixed electrode finger 41 and movable electrode finger 31 can be narrowed regardless of the limit of the aspect ratio of etching, thereby improving the sensitivity of acceleration sensor 1.

[0057] According to the acceleration sensor 1 of this embodiment, the displacement of the fixed electrode fingers 41 in the X direction is restricted by the restricting portion 60, so that the gap G2 between the movable electrode fingers 31 and the fixed electrode fingers 41 can be maintained at a predetermined gap regardless of manufacturing errors or temperature changes.

[0058] According to the acceleration sensor 1 of this embodiment, the distance L3 between the fixed electrode finger 41 and the restricting portion 60 in the X direction is shorter than the distance L1 between the first electrode finger 51 and the second electrode finger 52 in the X direction. As a result, when the displacement of the fixed electrode finger 41 in the X direction is restricted by the restricting portion 60, the first electrode finger 51 and the second electrode finger 52 do not come into contact with each other. In other words, when the displacement of the fixed electrode finger 41 in the X direction is restricted by the restricting portion 60, the first electrode finger 51 and the second electrode finger 52 are arranged with a gap between them. As a result, it is possible to restrict a current from flowing between the first electrode finger 51 and the second electrode finger 52, and to restrict a decrease in sensitivity in the acceleration sensor 1.

[0059] (Modification) FIG. 5 is a schematic plan view of an acceleration sensor 1 according to a modified example of this embodiment.

[0060] In this modification, the spring portion 33 is cantilevered on the inner wall surface 13A of the substrate 10. As a result, the movable electrode finger 31 is indirectly supported on the inner wall surface 13A of the substrate 10 via the base portion 32 and the spring portions 33A and 33B. The isolation joint 34 of this modification crosses the spring portion 33 in the X and Z directions and divides it in the Y direction. The isolation joint 34 mechanically connects both sides of the spring portion 33 divided in the Y direction by the isolation joint 34, while electrically insulating them.

[0061] In this modified example, the movable electrode finger 31, the fixed electrode finger 41, the first electrode finger 51, the second electrode finger 52, and the restricting portion 60 are directly or indirectly supported by an anchor region R arranged on inner wall surface 13A of the four inner wall surfaces 13A to 13D.

[0062] In the acceleration sensor 1 according to this modification, the fixed electrode fingers 41, the movable electrode fingers 31, the first electrode fingers 51, and the second electrode fingers 52 are directly or indirectly supported by the anchor regions R arranged on the inner wall surface 13A. Therefore, the packaging stress that may occur in the substrate 10 is transmitted to the MEMS electrode 20 via the anchor regions R. As a result, when the MEMS electrode 20 is supported at multiple points by the multiple inner wall surfaces 13A to 13D, it is easier to minimize the distortion that may occur in the MEMS electrode 20 compared to when the packaging stress is transmitted to the MEMS electrode 20 from the multiple points. As a result, it is easier to stabilize the detection by the acceleration sensor 1.

[0063] (Other variations) The MEMS device according to the present disclosure is not limited to the configurations of the above-described embodiments, and various modifications are possible.

[0064] In the above embodiment, the acceleration sensor 1 has been described as an example of the MEMS device, but the present disclosure can be applied to various MEMS devices having MEMS electrodes. For example, the MEMS device according to the present disclosure may be a MEMS oscillator or an acceleration sensor.

[0065] In the above embodiment, the acceleration sensor 1 has the restricting portion 60, but the present invention is not limited to this.

[0066] In the above embodiment, the distance L3 between the fixed electrode finger 41 and the restricting portion 60 in the X direction is shorter than the distance L1 between the first electrode finger 51 and the second electrode finger 52 in the X direction, but is not limited to this. In other words, the distance L3 between the fixed electrode finger 41 and the restricting portion 60 in the X direction may be longer than the distance L1 between the first electrode finger 51 and the second electrode finger 52 in the X direction.

[0067] The shape and structure of the beam portion 42 are not limited to those exemplified in the above embodiment. The shape and structure of the beam portion 42 can be changed as long as the beam portion 42 has a function of being deformed by an electrostatic force acting between the first electrode finger 51 and the second electrode finger 52 of the electrode portion 50, and the gap G2 between the movable electrode finger 31 and the fixed electrode finger 41 after the deformation becomes narrower than the gap G1 between the movable electrode finger 31 and the fixed electrode finger 41 before the deformation.

[0068] The arrangement, shape, and structure of the electrode section 50 are not limited to those exemplified in the above embodiment. The arrangement, shape, and structure of the electrode section 50 can be changed as long as the electrode section 50 has a function of deforming the beam section 42 by electrostatic force to make the gap G2 between the movable electrode finger 31 and the fixed electrode finger 41 after the beam section 42 is deformed narrower than the gap G1 between the movable electrode finger 31 and the fixed electrode finger 41 before the beam section 42 is deformed. For example, in the above embodiment, the electrode section 50 has a pair of the first electrode finger 51 and the second electrode finger 52, but is not limited thereto, and may have multiple pairs of the first electrode finger 51 and the second electrode finger 52 that are interdigitated and opposed to each other in a comb-like manner.

[0069] In the above embodiment, the distance L1 in the X direction between the first electrode finger 51 and the second electrode finger 52 is shorter than the distance L2 in the X direction between the second electrode finger 52 and the fixed electrode finger 41, but is not limited to this. In other words, the distance L1 in the X direction between the first electrode finger 51 and the second electrode finger 52 may be longer than the distance L2 in the X direction between the second electrode finger 52 and the fixed electrode finger 41.

[0070] In the above embodiment, the substrate 10 is described as being composed of only a single silicon layer, but the substrate according to the present disclosure may have other layers such as a silicon oxide (SiO2) layer or a silicon carbide (SiC) layer in addition to the silicon layer. For example, the substrate according to the present disclosure may be a silicon on insulator (SOI) substrate.

[0071] [Note] The MEMS device according to the present disclosure provides the following aspects.

[0072] [Aspect 1] A substrate having a first main surface and a second main surface opposite to the first main surface, and a cavity recessed from the first main surface side to the second main surface side is disposed therein; a MEMS electrode disposed within the cavity and spaced apart from a bottom surface of the cavity toward the first principal surface; Equipped with The MEMS electrode is a movable electrode finger extending in a first direction and connected to the substrate so as to be movable relative to the substrate; fixed electrode fingers extending in the first direction and arranged at intervals from the movable electrode fingers so as to face the movable electrode fingers in a second direction intersecting the first direction; a beam portion that is cantilevered on the substrate and connects the fixed electrode finger to the substrate; an electrode section configured such that, when a voltage is applied, the beam section is deformed by electrostatic force, and a gap between the movable electrode finger and the fixed electrode finger in the second direction becomes narrower than a gap before the deformation of the beam section; Equipped with The electrode portion is a first electrode finger extending in the first direction and connected to the beam portion; a second electrode finger extending in the first direction, arranged at a distance from the first electrode finger so as to face the first electrode finger in the second direction, arranged on the fixed electrode finger side relative to the first electrode finger in the second direction, and fixed to the substrate; The present invention provides a MEMS device comprising:

[0073] When etching between the movable electrode fingers and the fixed electrode fingers, the aspect ratio of the etching is limited, so the interval between the movable electrode fingers and the fixed electrode fingers becomes wider depending on the depth of the etching. In other words, when etching between the movable electrode fingers and the fixed electrode fingers to a predetermined depth, it is difficult to narrow the interval between the fixed electrode fingers and the movable electrode fingers below a certain interval. In contrast, according to the MEMS device of the first aspect, when different voltages are applied to the first electrode finger and the second electrode finger of the electrode unit, an electrostatic force that attracts the first electrode finger and the second electrode finger acts on the first electrode finger and the second electrode finger. Due to this electrostatic force, the beam portion is deformed so that the first electrode finger is displaced closer to the second electrode finger. Due to this deformation of the beam portion, the fixed electrode finger is displaced closer to the movable electrode finger, and the interval between the movable electrode finger and the fixed electrode finger in a state in which a voltage is applied can be made narrower than the interval before the beam portion is deformed. As a result, the interval between the movable electrode finger and the fixed electrode finger can be made narrower than the interval formed between the fixed electrode finger and the movable electrode finger by etching for forming the fixed electrode finger and the movable electrode finger. As a result, the distance between the fixed electrode fingers and the movable electrode fingers can be narrowed regardless of the limit of the aspect ratio of etching, thereby improving the sensitivity of the MEMS device.

[0074] [Aspect 2] The MEMS device according to aspect 1 is provided, wherein the substrate has a restricting portion that restricts displacement of the fixed electrode fingers by coming into contact with the fixed electrode fingers when the fixed electrode fingers are displaced toward the movable electrode fingers by a predetermined distance or more.

[0075] [Aspect 3] In the MEMS device according to aspect 2, a distance between the fixed electrode finger and the restricting portion in the second direction is shorter than a distance between the first electrode finger and the second electrode finger in the second direction.

[0076] [Aspect 4] the substrate has a plurality of inner wall surfaces defining the cavity; Provided is a MEMS device described in any one of aspects 1 to 3, wherein the fixed electrode finger, the movable electrode finger, the first electrode finger, and the second electrode finger are directly or indirectly supported by an anchor region arranged on any one of the multiple inner wall surfaces. [Explanation of symbols]

[0077] 1. Acceleration sensor (MEMS device) 10 Substrate 10a First main surface 10b Second main surface 11 Insulating layer 12 Cavity 12a Bottom 13 Inner wall surface 20 MEMS electrodes 30 Movable electrode 31 Movable electrode finger 32 Base 33 Spring section 34 Isolation joint 40 Fixed electrode 41 Fixed electrode finger 42 Beam section 42a First end 42b Second end 43 1st beam 44 2nd beam 45 Isolation joint 50 Electrode section 51 1st electrode finger 52 2nd electrode finger 53 Isolation joint 60 Regulatory Department 61 Main unit 62 Protrusion 63 Isolation joint 70 Electrode Pads 71 Electrode Pads 72 Electrode Pads 73 Electrode Pads 74 Electrode Pads 80 wiring layer 81 Wiring layer 82 wiring layer 83 Wiring layer 84 Wiring layer 85 Wiring layer

Claims

1. a substrate having a first main surface and a second main surface opposite to the first main surface, and a cavity recessed from the first main surface side to the second main surface side; a MEMS electrode disposed in the cavity and spaced apart from a bottom surface of the cavity toward the first principal surface; Equipped with The MEMS electrode is a movable electrode finger extending in a first direction and connected to the substrate so as to be movable relative to the substrate; fixed electrode fingers extending in the first direction and arranged at intervals from the movable electrode fingers so as to face the movable electrode fingers in a second direction intersecting the first direction; a beam portion that is cantilevered on the substrate and connects the fixed electrode finger to the substrate; an electrode section configured such that, when a voltage is applied, the beam section is deformed by electrostatic force, and a gap between the movable electrode finger and the fixed electrode finger in the second direction becomes narrower than a gap before the beam section is deformed; Equipped with The electrode portion is a first electrode finger extending in the first direction and connected to the beam portion; a second electrode finger extending in the first direction, arranged at a distance from the first electrode finger so as to face the first electrode finger in the second direction, arranged on the fixed electrode finger side relative to the first electrode finger in the second direction, and fixed to the substrate; A MEMS device comprising:

2. The MEMS device according to claim 1 , wherein the substrate has a restricting portion that restricts displacement of the fixed electrode fingers by coming into contact with the fixed electrode fingers when the fixed electrode fingers are displaced toward the movable electrode fingers by a predetermined distance or more.

3. The MEMS device according to claim 2 , wherein a distance between the fixed electrode finger and the restricting portion in the second direction is shorter than a distance between the first electrode finger and the second electrode finger in the second direction.

4. the substrate has a plurality of inner wall surfaces defining the cavity; The MEMS device according to claim 1 , wherein the fixed electrode finger, the movable electrode finger, the first electrode finger, and the second electrode finger are directly or indirectly supported by an anchor region arranged on any one of the plurality of inner wall surfaces.

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