Membrane element and vibration power generation device

Abstract

The MEMS element includes a base, an insulating layer fixed to one face of the base, a first upper layer having at least a portion fixed to the insulating layer, and a second upper layer disposed so as to surround a periphery of the first upper layer and separated from the first upper layer by a slit, the first upper layer having a protruding portion protruding toward the second upper layer at a predetermined portion.

Description

TECHNICAL FIELD

[0001] The present application relates to a MEMS element and a vibration power generation device. BACKGROUND

[0002] A MEMS element is known which uses an SOI (Silicon On Insulator) substrate, and forms a fixed portion having a fixed comb tooth and a movable portion having a movable comb tooth on an insulating layer such as a silicon oxide layer formed on a silicon substrate. The fixed portion and the movable portion are each fixed at least in part to the insulating layer. A lead portion connected to an electrode terminal is formed in the fixed portion. There is also a structure in which a peripheral fixed pattern is formed around the fixed portion including the lead portion.

[0003] The fixed portion, the movable portion, and the peripheral fixed pattern are separated by a narrow slit formed by etching, and are electrically insulated. When the slit is formed by etching, the fixed portion site fixed to the insulating layer is undercut, and therefore, for example, at a site where the width of the fixed portion site such as the lead portion is narrow, the bonding strength is insufficient, the insulating layer is lifted, or the fixed portion site is broken by a slight impact.

[0004] Therefore, there is a need to address the reduction in strength of the insulating layer due to undercutting.

[0005] Although not corresponding to the lead portion, but to the method of forming the slit between the fixed portion and the movable portion, a method is known in which, after the slit is formed, a protective film is formed on the side surface of the fixed portion, and the insulating layer is removed. Thereby, undercutting of the insulating layer under the fixed portion is prevented, and the bonding strength of the insulating layer under the fixed portion is ensured. The method is shown below.

[0006] First, a photoresist is applied to the entire surface of the fixed portion and the movable portion including the slit portion, and the photoresist is patterned, and the photoresist except for the peripheral side surface of the fixed portion is removed by RIE (Reactive Ion Etching) or the like. Next, ashing is performed by oxygen plasma or the like, and the photoresist remains only on the side surface of the fixed portion opposite the movable portion. Thereafter, if wet etching using an etching solution is performed, the remaining photoresist becomes a protective film against etching, and prevents etching of the portion where the protective film is formed, and undercutting of the lower portion of the fixed portion and the insulating layer can be prevented (for example, refer to Patent Document 1).

[0007] PRIOR ART DOCUMENTS

[0008] PATENT DOCUMENTS

[0009] Patent Document 1: Japanese Patent Application Publication No. 2005-323039

[0010] Patent Document 2: Japanese Patent Application Publication No. 2018-88780 SUMMARY

[0011] Problem to be Solved by the Invention

[0012] In the method described in Patent Literature 1, since the processing procedure is long and complicated, the productivity is poor and the cost is high.

[0013] Solution to the Problem

[0014] The MEMS element of the first aspect of the present application includes a base, an insulating layer fixed to one face of the base, a first upper layer having at least a portion fixed to the insulating layer, and a second upper layer disposed so as to surround a periphery of the first upper layer and separated from the first upper layer by a slit, the first upper layer having a protruding portion protruding toward the second upper layer, the protruding portion being fixed to the insulating layer.

[0015] According to the second aspect of the present application, in the MEMS element of the first aspect, it is preferable that the first upper layer include a lead portion, and the protruding portion be provided to the lead portion.

[0016] According to the third aspect of the present application, in the MEMS element of the first or second aspect, it is preferable that the insulating layer of a region corresponding to the slit be removed, and the base be exposed from at least a portion of the region corresponding to the slit in a thickness direction of the insulating layer.

[0017] According to the fourth aspect of the present application, in the MEMS element of any one of the first to third aspects, it is preferable that the second upper layer be fixed to the insulating layer.

[0018] According to the fifth aspect of the present application, in the MEMS element of any one of the first to fourth aspects, it is preferable that the base, the first upper layer, and the second upper layer be formed of silicon.

[0019] According to the sixth aspect of the present application, in the MEMS element of any one of the first to fifth aspects, it is preferable that the insulating layer be formed of an inorganic insulating material.

[0020] According to the seventh aspect of the present application, in the MEMS element of any one of the first to sixth aspects, it is preferable that the first upper layer have a plurality of fixed comb teeth, and the insulating layer of a region corresponding between the adjacent formed fixed comb teeth be removed.

[0021] The vibration power generation device of the eighth aspect of the present application includes the MEMS element of the seventh aspect, a movable portion having a plurality of movable comb teeth engaged with the fixed comb teeth of the first upper layer, an elastic support portion elastically supporting the movable portion, and an output portion outputting power generated by movement of electric charges generated by relative movement of the fixed comb teeth and the movable comb teeth.

[0022] Inventive Effects

[0023] According to the present application, reduction in the fixing strength of the first upper layer can be suppressed, and productivity can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a plan view of a vibration power generation device in which a MEMS element is sealed in a vacuum package, as viewed through an upper cover.

[0025] Figure 2 is Figure 1 is a II-II cross-sectional view of the vibration power generation device illustrated in

[0026] Figure 3 (A) of Figure 1 is a plan view of the MEMS element illustrated in Figure 3 (B) of Figure 3 is a plan view of the MEMS element illustrated in (A) of

[0027] Figure 4 (A) to (D) of Figure 3 are views illustrating an example of a manufacturing method of the MEMS element illustrated in

[0028] Figure 5 (A) to (D) of Figure 4 are views illustrating an example of a manufacturing method of the MEMS element illustrated in

[0029] Figure 6 is Figure 1 is an enlarged view of the region VI of

[0030] Figure 7 (A) of Figure 6 is a VIIA-VIIA cross-sectional view of Figure 7 (B) of Figure 7 is a cross-sectional view of a comparative example of a structure of a region corresponding to (A). DETAILED DESCRIPTION

[0031] Hereinafter, a mode for carrying out the present application will be described with reference to the accompanying drawings.

[0032] Figure 1 is a plan view of a vibration power generation device 1 in which a MEMS element 10 is sealed in a vacuum package, as viewed through an upper cover 3, Figure 2 is Figure 1 is a II-II cross-sectional view of

[0033] The housing 2 and the upper cover 3 constitute a vacuum package, and the MEMS element 10 is housed in the vacuum package. In Figure 1In a plan view, the illustration of the upper cover 3 provided on the upper surface side (z-axis positive direction side) is omitted in order to clearly show the planar structure of the MEMS element 10.

[0034] In addition, in the present embodiment, the x-axis direction, the y-axis direction, and the z-axis direction are the directions shown in each drawing.

[0035] The MEMS element 10 has four fixed electrode portions (first upper layer) 11, a fixed electrode outer peripheral portion (second upper layer) 35 surrounding the periphery of each fixed electrode portion 11, a movable electrode portion (movable portion) 12, and an elastic support portion 13 elastically supporting the movable electrode portion 12. As shown in Figure 2 The base 7 of the MEMS element 10 is fixed to the case 2 by die bonding. The case 2 is formed of, for example, an electrically insulating material (for example, ceramic). An upper cover 3 for vacuum sealing the inside of the case 2 is seam-welded to the upper end of the case 2.

[0036] As shown in Figure 2 The MEMS element 10 is configured to include the base 7 composed of Si, the device layer 9 composed of a Si active layer, and the insulating layer 8 formed of an inorganic insulating material such as SiO2, which bonds the base 7 and the device layer 9. That is, the MEMS element 10 is configured in a three-layer structure in which the base 7, the insulating layer 8, and the device layer 9 composed of a Si active layer are stacked in the z-axis direction. The MEMS element 10 of this structure is generally formed using an SOI (Silicon On Insulator) substrate by a general MEMS processing technique.

[0037] The device layer 9 has the four fixed electrode portions 11, the fixed electrode outer peripheral portion 35, the movable electrode portion 12, and the elastic support portion 13. The fixed electrode portion 11 has a plurality of fixed comb teeth 110, a fixed comb tooth linking portion 111 linking the plurality of fixed comb teeth 110, and a lead portion 112. The fixed comb teeth 110 extend in the x-axis direction and are arranged at predetermined intervals in the y-axis direction. The fixed comb tooth linking portion 111 extends in the y-axis direction and links the plurality of fixed comb teeth 110 arranged in the y-axis direction. The lead portion 112 extends in a direction orthogonal to the fixed comb tooth linking portion 111, that is, in the x-axis direction. A terminal portion of a rectangular shape is formed at the leading end portion of the lead portion 112. An electrode pad 113 is formed by providing a conductive metal such as aluminum on the upper surface of the terminal portion.

[0038] A protruding portion 15 (refer to Figure 6 ) protruding toward the fixed electrode outer peripheral portion 35 is provided at a predetermined position of the side surface of the lead portion 112 extending in the x-axis direction (refer to region VI). The protruding portion 15 provided to the lead portion 112 will be described later.

[0039] A slit 16 is provided between the fixed electrode outer peripheral portion 35 and the lead portion 112 and the fixed comb tooth connecting portion 111 of each fixed electrode portion 11, and the fixed electrode outer peripheral portion 35 and the lead portion 112 and the fixed comb tooth connecting portion 111 of each fixed electrode portion 11 are physically separated from the fixed electrode outer peripheral portion 35. Thus, the fixed electrode outer peripheral portion 35 is electrically insulated from each fixed electrode portion 11. The lead portion 112 and the fixed comb tooth connecting portion 111 of each fixed electrode portion 11 are supported by the base 7 via the insulating layer 8. The fixed comb teeth 110 of each fixed electrode portion 11 extend over regions corresponding to the rectangular-shaped opening portions 7a (see FIG. 6) provided in the base 7. Figure 2 , Figure 3 (A), Figure 3 (B).

[0040] The movable electrode portion 12 has a plurality of movable comb teeth 120, a central band portion 121, and movable comb tooth connecting portions 122 connecting the plurality of movable comb teeth 120. The movable comb tooth connecting portions 122 extend from the center of the central band portion 121 in the x-axis direction to the positive y-axis direction and the negative y-axis direction, respectively. Each movable comb tooth 120 extends from each movable comb tooth connecting portion 122 extending in the positive y-axis direction and the negative y-axis direction to the positive x-axis direction and the negative x-axis direction, and is arranged at a predetermined interval in the y-axis direction.

[0041] As shown in FIG. 1, hammers 105a and 105b are fixed to the upper surface on the positive z-axis direction side and the lower surface on the negative z-axis direction side of the central band portion 121, respectively, by adhesion or the like. Figure 2

[0042] The two fixed electrode portions 11 on the positive y-axis direction side of the central band portion 121 are arranged in line symmetry with respect to the center line of the x-axis direction of the central band portion 121. In addition, the other two fixed electrode portions 11 on the negative y-axis direction side of the central band portion 121 are arranged in line symmetry with respect to the center line of the x-axis direction of the central band portion 121.

[0043] The plurality of fixed comb teeth 110 extending in the x-axis direction from the fixed comb tooth connecting portion 111 and the movable comb teeth 120 extending in the x-axis direction from each movable comb tooth connecting portion 122 are arranged so as to mesh with each other with a gap in the y-axis direction.

[0044] ​The movable electrode portion 12 is mechanically and electrically connected to the vibration restricting portion 150 fixed to the base 7 via the elastic support portion 13. The vibration restricting portion 150 is provided with one each in the positive direction and the negative direction of the x-axis of the central band portion 121, i.e., one pair. The pair of vibration restricting portions 150 are formed in the same shape and are arranged in line symmetry with respect to the center axes in the x-axis and y-axis directions of the central band portion 121.

[0045] The movable electrode portion 12 supported by the elastic support portion 13 vibrates in the x-axis direction due to external vibration, and one side surface 121a of the central band portion 121 of the movable electrode portion 12 collides with the protrusion 151 of the vibration restricting portion 150. At this time, if the position of the protrusion 151 of the vibration restricting portion 150 with which the movable portion collides in the y-axis direction is offset from the center axis passing through the center of gravity of the central band portion 121 including the hammers 105a, 105b in the y-axis direction, a moment is generated in the central band portion 121 of the movable electrode portion 12. If a moment is generated in the central band portion 121 of the movable electrode portion 12, the elastic support portion 13 is deformed, and the central band portion 121 is abnormally vibrated. Therefore, the center line of the abutting portion of the vibration restricting portion 150 with which the central band portion 121 of the movable electrode portion 12 collides in the y-axis direction needs to be coaxial with the center line of the central band portion 121 of the movable electrode portion 12 extending in the x-axis direction.

[0046] The electrode pad 114 is connected to the vibration restricting portion 150. A terminal portion of a rectangular shape is integrally formed in the vibration restricting portion 150, and the electrode pad 114 is formed by providing a conductive metal such as aluminum on the upper surface of the terminal portion.

[0047] The electrode pads 113, 114 are connected to the electrodes 21a, 21b provided to the housing 2 via the metal wires 22, respectively.

[0048] An electret is formed in the fixed electrode portion 11 and the movable electrode portion 12. In the case where an electret is formed in only one of the fixed electrode portion 11 and the movable electrode portion 12, a charge of the opposite polarity is generated in the other, and thus an electret can be formed in only one of the fixed electrode portion 11 and the movable electrode portion 12.

[0049] In the present embodiment, the movable electrode portion 12 is configured to vibrate in the x-axis direction, and when the movable electrode portion 12 vibrates in the x-axis direction, the movable comb teeth 120 of the movable electrode portion 12 change the amount of insertion with respect to the fixed comb teeth 110 of the fixed electrode portion 11 and generate a movement of a charge to generate electricity.

[0050] Figure 3 (A) of FIG. 1 is a view showing the MEMS element 10 before the hammers 105a, 105b are fixed.

[0051] As described above, the MEMS element 10 is formed by a general MEMS processing technique using an SOI (Silicon On Insulator) substrate. The SOI substrate is composed of a three-layer structure in which a base 7, an insulating layer 8, and a device layer 9 composed of a Si active layer are stacked in the z-axis direction. As shown in Figure 2 , the device layer 9 is supported by the base 7 via the insulating layer 8. The fixed electrode portion 11, the fixed electrode outer peripheral portion 35, the movable electrode portion 12, the elastic support portion 13, and the vibration restricting portion 150 are formed of the Si active layer.

[0052] In Figure 3 (A), the fixed electrode portion 11, the movable electrode portion 12, the elastic support portion 13, and the vibration restricting portion 150 on the base 7 are represented by hatching. The movable electrode portion 12 is elastically supported by four elastic support portions 13. Each elastic support portion 13 has three beams 13a to 13c capable of elastically deforming. The movable electrode portion 12 is disposed on a region corresponding to an opening portion 7a (refer to Figure 3 (B)) provided in the base 7. The movable electrode portion 12 is connected to the vibration restricting portion 150 via the beams 13a to 13c of the elastic support portion 13. The vibration restricting portion 150 is fixed to the base 7 via the insulating layer 8. Thus, the movable electrode portion 12 is supported on the base 7 via the four elastic support portions 13 and the vibration restricting portion 150.

[0053] The vibration restricting portion 150 also functions as a restricting portion that restricts the range of vibration of the movable electrode portion 12 in the x-axis direction. The vibration of the movable electrode portion 12 in the x-axis direction is restricted by the movable electrode portion 12 colliding with the protrusions 151 of each vibration restricting portion 150.

[0054] Figure 3 (B) is a plan view that represents a state in which the fixed electrode portion and the movable electrode portion are removed from the MEMS element illustrated in Figure 3 (A).

[0055] Figure 3 The hatched region 11C of (B) represents the pattern of the junction of the fixed comb finger junction portion 111 and the lead portion 112 of each fixed electrode portion 11 to the insulating layer 8. Figure 3 The hatched region 11A of (B) represents the pattern of the junction of the end portion of the beam 13a of the elastic support portion 13 to the insulating layer 8. Figure 4 The hatched region 11B of (B) represents the pattern of the junction of the vibration restricting portion 150 to the insulating layer 8.

[0056] Next, a manufacturing method of the MEMS element 10 will be described.

[0057] Figure 3 (A) to (D) of FIG. 10 are plan views that represent the manufacturing process of the MEMS element 10.Figure 5 The figure illustrates an example of a method for manufacturing a MEMS device. Figure 4 (A) to (D) indicate the following Figure 4 A diagram illustrating an example of a method for manufacturing MEMS components.

[0058] In addition, Figure 5 and Figure 3 In the middle, it schematically indicates along Figure 4 The cross section of the single-dotted dashed line CC of (A).

[0059] Figure 4 (A) is a cross-sectional view showing the SOI substrate forming the MEMS device 10. The SOI substrate is composed of a Si substrate layer 301, a SiO2 insulating layer 302, and a Si active layer device layer 303. Figure 4 In the first step shown in (B), a nitride film (SiN film) 304 is formed on the surface of device layer 303. Figure 4 In the second step shown in (C), the nitride film 304 is patterned to form a nitride film pattern 304a for protecting the portions of the electrode pads 113 and 114.

[0060] exist Figure 4 In the third step shown in (D), a mask pattern for forming the fixed electrode portion 11, the movable electrode portion 12, the elastic support portion 13, and the vibration limiting portion 150 is formed and disposed on the device layer 303, and the device layer 303 is etched. The etching process is performed by DRIE (Deep Reactive Ion Etching) or the like until the insulating layer 302 is reached. Figure 3 In (D), the part indicated by symbol B1 corresponds to the fixed electrode part 11, the part indicated by symbol B2 corresponds to the movable electrode part 12, and the part indicated by symbol B3 corresponds to the vibration limiting part 150.

[0061] Along Figure 5 In the cross-section of the dashed line CC in (A), the fixed electrode section 11, shown by symbol B1, includes an electrode pad 113 and a fixed comb tooth connecting section 111; the movable electrode section 12, shown by symbol B2, includes a movable comb tooth connecting section 122 and a central belt section 121; and the section shown by symbol B3 includes a vibration limiting section 150 and an electrode pad 114. The electrode pad 114 is not shown in the diagram.

[0062] Additionally, a fixed electrode outer periphery 35 is formed on the outer side of the electrode pad 113 in the negative x-axis direction, between the electrode pad 113 and the fixed comb tooth connection portion 111. A slit 16 is formed between the outer side of the electrode pad 113 and the electrode pad 113, between the electrode pad 113 and the fixed electrode outer periphery 35, and between the fixed electrode outer periphery 35 and the fixed comb tooth connection portion 111.

[0063] exist Figure 5 In the fourth step shown in (A), a mask pattern for forming the opening 7a in the base 7 is formed on the lower surface of the substrate 301, and the substrate 301 is processed using DRIE. Thus, the opening 7a is formed in the substrate 301, and the substrate 301 becomes the base 7 having the opening 7a. Figure 5 In the fifth step shown in (B), the insulating layer 302 of SiO2 exposed from the opening 7a of the substrate 301 is removed by using strong hydrofluoric acid.

[0064] In addition, Figure 5 In (B), only a portion of the fixed comb tooth connection 111 of the fixed electrode part 11 is shown, and only a portion of the movable comb tooth connection 122 and the central belt part 121 of the movable electrode part 12 are shown. The movable comb tooth connection 122 and the central belt part 121 are... Figure 3 The diagram in (B) shows the state of floating from the basal layer 301, but as Figure 5 As shown in (B), the movable electrode 12 is held by a vibration limiting part 150 fixed to a portion of the insulating layer 8, which is indicated by the shaded area 11B, and an elastic support part 13 connected to the vibration limiting part 150.

[0065] exist Figure 5 In the sixth step shown in (C), a silicon oxide film 305 is formed on the surfaces of the substrate layer 301 and the device layer 303 by thermal oxidation. At this time, a silicon oxide film 305 is also formed on the side surface of the fixed electrode portion 11 within the slit 16 and on the side surface of the outer periphery 35 of the fixed electrode. Figure 5 In the sixth step shown in (D), the nitride film pattern 304a is removed, and an aluminum electrode 113a is deposited in the removed area to form an electrode pad 113. Additionally, electrode pads 114 are also formed at this time, but since the electrode pads 114 are formed in... Figure 5 Outside the range of (D), therefore in Figure 1 (D) is not illustrated.

[0066] The MEMS element 10 is formed through the above processing steps. Then, an electret is formed on at least one of the fixed comb teeth 110 and the movable comb teeth 120 by a known electret forming method (for example, see Japanese Patent No. 5627130).

[0067] The vibration power generation device 1 is a very small structure body processed by MEMS technology, Figure 6 The package 2 shown has a size of several cm in length and width and a height of several mm or so.

[0068] Figure 1 is Figure 7 is an enlarged view of the region VI of Figure 6 (A) of Figure 7 is a cross-sectional view taken along the line VIIA-VIIA of Figure 7 (B) of Figure 4 is a cross-sectional view of a comparative structure showing a region corresponding to (A) of

[0069] A protruding portion 15 is formed in the lead portion 112 of the fixed electrode portion 11, and the protruding portion 15 protrudes toward the fixed electrode outer peripheral portion 35 at a predetermined position in the extension direction of the lead portion 112, i.e., the x-axis direction.

[0070] As shown in (D) of Figure 7 (D), the lead portion 112 and the fixed electrode outer peripheral portion 35 are separated by the slit 16 formed at the same time as the process of forming the fixed electrode portion 11 and the movable electrode portion 12 by processing the device layer 303 by DRIE. It is also possible to perform the process of forming the fixed electrode portion 11 and the movable electrode portion 12 and the process of forming the slit 16 between the fixed electrode portion 11 and the movable electrode portion 12 by different processes.

[0071] In the process of forming the slit 16 based on DRIE, the device layer 303 as a whole is removed in the thickness direction (z-axis direction), and in addition, the insulating layer 302 is also removed as a whole in the thickness direction. At this time, the lead portion 112 and the lower portion of the fixed electrode outer peripheral portion 35 on the side of the slit 16, i.e., the side of the insulating layer 302, are undercut.

[0072] Figure 7 (B) of shows a comparative example in which the protruding portion 15 is not formed in the lead portion 112. In the comparative example, the width of the lead portion 112, in other words, the length in the y-direction, is small, and therefore the lower portion of the lead portion 112 is undercut, and as a result, the portion of the lead portion 112 fixed to the insulating layer 302 almost disappears. Therefore, the lead portion 112 is lifted from the insulating layer 302, or the joint with the insulating layer 302 is broken due to a small impact, and the lead portion 112 is adsorbed or brought into contact with the fixed electrode outer peripheral portion 35 due to adhesion. That is, the lead portion 112 is in conduction with the fixed electrode outer peripheral portion 35, and electrical insulation cannot be ensured.

[0073] In contrast, in the structure of the present embodiment in which the protruding portion 15 is formed in the lead portion 112, as shown in Figure 1As shown in (A), the total width of the lead portion 112 and the protruding portion 15 becomes large. Therefore, even if the lead portion 112 and the lower portion of the protruding portion 15 are undercut, the area of the joint with the insulating layer 302 can be sufficiently ensured. Therefore, the strength of the joint between the lead portion 112 including the protruding portion 15 and the insulating layer 302 is improved, and the contact between the lead portion 112 and the fixed electrode peripheral portion 35 can be prevented, and thus, the electrical insulation between the lead portion 112 and the fixed electrode peripheral portion 35 can be ensured.

[0074] According to the above-described embodiment, the following effects are exerted.

[0075] The MEMS element 10 includes a base 7, an insulating layer 8 fixed to one face of the base 7, a fixed electrode portion (first upper layer) 11 having at least a portion fixed to the base 7 and having a lead portion 112 connected to a fixed comb tooth connecting portion 111, and a fixed electrode peripheral portion (second upper layer) 35 disposed so as to surround the periphery of the lead portion 112 and disposed separately from the lead portion 112 by a slit 16, the lead portion 112 having a protruding portion 15 protruding toward the fixed electrode peripheral portion 35 at a predetermined portion, the protruding portion 15 being fixed to the insulating layer 8. With this structure, the width of the predetermined portion of the lead portion 112 provided with the protruding portion 15 becomes large. Therefore, even if the lead portion 112 and the protruding portion 15 are undercut when the slit 16 is formed by etching, the insulating layer required for the fixation of the fixed electrode portion 11 remains. Therefore, the strength of the fixed electrode portion 11 can be ensured, and thus, the electrical insulation between the lead portion 112 and the fixed electrode peripheral portion 35 can be ensured.

[0076] The MEMS element 10 of the present embodiment can be manufactured by forming the protruding portion 15 protruding toward the fixed electrode peripheral portion 35 at the predetermined portion of the lead portion 112, and the manufacturing method is completely the same as in the case where the protruding portion 15 is not formed in the lead portion 112. Therefore, compared to the method of forming a protective film at the portion where undercutting is prevented, the productivity can be improved.

[0077] (Modified example)

[0078] In the above-described embodiment, a structure in which one protruding portion 15 is formed in each lead portion 112 is exemplified. However, a plurality of protruding portions 15 can be formed at predetermined intervals along the length direction of each lead portion 112.

[0079] Furthermore, in the above embodiment, a structure is illustrated where the protrusion 15 protrudes toward the central strip portion 121 of the movable electrode portion 12. However, the protrusion 15 may also protrude toward the opposite side of the central strip portion 121 of the movable electrode portion 12. Additionally, when multiple protrusions 15 are formed in the lead portion 112, a protrusion 15 protruding toward the central strip portion 121 and a protrusion 15 protruding toward the opposite side of the central strip portion 121 may be provided in a single lead portion 112.

[0080] (Other implementation methods)

[0081] In the above embodiment, a structure in which the protrusion 15 is formed on the lead portion 112 of the fixed electrode portion 11 is illustrated. However, the protrusion 15 may also be formed on the fixed comb tooth connection portion 111. Figure 1 The diagram illustrates an example of a formation location where a protrusion 15 is formed in the fixed comb tooth connection portion 111. (Figure 15A shows a formation location where the protrusion 15 is formed in the fixed comb tooth connection portion 111.) Figure 3 In this diagram, the forming position 15A is shown only for one fixed electrode portion 11, but it is naturally formed on each fixed electrode portion 11. Furthermore, multiple forming positions 15A may be provided for each fixed comb tooth connecting portion 111. The reason for forming the protrusion 15 on the fixed comb tooth connecting portion 111 will be explained below.

[0082] Fixed comb tooth connecting part 111 ​ The region 11C1, which extends linearly along the y-direction in the shaded area 11C shown in (B), is bonded to the insulating layer 8. As described in Japanese Patent Application Publication No. 2018-88780 published as Patent Document 2, in a vibration power generation device, it is advantageous to reduce the resonant Q value of the movable electrode portion 12 and make the resonant frequency more gradual; in other words, it is advantageous to have a structure capable of resonating over a wide frequency band for external vibrations. Therefore, it is necessary to reduce the parasitic capacitance generated between the base 7 and the fixed electrode portion 11.

[0083] Therefore, the width (length in the x-axis direction) of the joint between the fixed comb tooth connection 111 and the insulating layer 8, which is represented by the shaded area 11C1, must be reduced. However, the smaller the width of the fixed comb tooth connection 111 fixed to the insulating layer 8, the lower the bonding strength between the fixed comb tooth connection 111 and the insulating layer 8 will be due to the undercut generated at the joint between the fixed comb tooth connection 111 and the insulating layer 8 during the DRIE machining that forms the slit 16. Therefore, instead of adopting a structure that increases parasitic capacitance by not increasing the width of the fixed comb tooth connection 111, if a protrusion 15 is formed locally at a predetermined location of the fixed comb tooth connection 111, that is, locally, and the bonding width between the fixed comb tooth connection 111 and the insulating layer 8 is increased by using the protrusion 15, the necessary bonding strength can be ensured without increasing the parasitic capacitance even if the fixed comb tooth connection 111 is undercut.

[0084] In addition, the fixed comb tooth 110 side of the fixed comb tooth connecting portion 111 is positioned on the opening portion 7a formed in the base 7, and thus the fixed electrode outer peripheral portion 35 cannot be provided around the fixed comb tooth 110 side of the fixed comb tooth connecting portion 111. However, the fixed electrode outer peripheral portion 35 is provided in all regions of the fixed comb tooth connecting portion 111 provided on the base, and there is no region that does not cover around the fixed comb tooth connecting portion 111. In this specification, in this case, if the fixed electrode outer peripheral portion 35 is provided in all regions of the fixed comb tooth connecting portion 111 provided on the base, the fixed electrode outer peripheral portion 35 includes a structure provided around the fixed comb tooth connecting portion 111.

[0085] In the above-described embodiment, the MEMS element 10 is exemplified as being formed using an SOI substrate, but the MEMS element 10 can be formed using a silicon substrate instead of the SOI substrate. In addition, a glass, a metal, an aluminum oxide, or the like can be used instead of the silicon substrate.

[0086] In the above-described embodiment, the MEMS element 10 is exemplified as being used as a vibration power generation device. However, the MEMS element can be used as a vibration actuator that vibrates a movable electrode portion by applying a driving voltage from the outside.

[0087] In addition, as described in Patent Literature 1 (Japanese Patent Application Publication No. 2005-323039), it is also possible to apply to a micro resonator having a structure in which a movable electrode and a fixed electrode are separated by a slit. The micro resonator described in Patent Literature 1 has a function as a filter that extracts only a specific frequency in a vibration generated between a fixed comb tooth electrode on one side and a movable comb tooth electrode.

[0088] Further, the structure of the MEMS element 10 of the present embodiment can be applied to various sensors.

[0089] The above describes various embodiments and modified examples, but the present application is not limited to these. The above-described various embodiments and modified examples can be combined or appropriately changed, and other modes considered within the scope of the technical idea of the present application are also included in the scope of the present application.

[0090] The disclosure of the following priority basis application is hereby incorporated by reference.

[0091] Japanese Patent Application Publication No. 2019-187152 (filed on October 10, 2019)

[0092] Explanation of Symbols

[0093] 1 - vibration power generation device; 7 - base; 8 - insulating layer; 10 - MEMS element; 11 - fixed electrode portion (first upper layer); 12 - movable electrode portion (movable portion); 13 - elastic support portion; 15 - protruding portion; 16 - slit; 35 - fixed electrode outer peripheral portion (second upper layer); 111 - fixed comb tooth connecting portion; 112 - lead portion.

Claims

1. A MEMS element, characterized by, Possessing: a base; an insulating layer fixed to one face of the base; a first upper layer of which at least a part is fixed to the insulating layer; and a second upper layer disposed so as to surround the periphery of the first upper layer and configured separately from the first upper layer through a slit, the first upper layer has a protruding portion protruding toward the second upper layer side at a predetermined portion, the insulating layer of a region corresponding to the slit is removed, the entire face of the base side of the protruding portion is fixed to the insulating layer, the base, the first upper layer, and the second upper layer are formed of silicon.

2. The MEMS element according to claim 1, characterized in that the first upper layer includes a lead portion, the protruding portion is provided to the lead portion.

3. The MEMS element according to claim 1, characterized in that the base is exposed from at least a part of the region corresponding to the slit in the thickness direction of the insulating layer.

4. The MEMS element according to claim 1, characterized in that the second upper layer is fixed to the insulating layer.

5. The MEMS element according to claim 1, characterized in that the insulating layer is formed of an inorganic insulating material.

6. The MEMS element according to any one of claims 1 to 5, characterized in that the first upper layer has a plurality of fixed comb teeth, and the insulating layer of a region corresponding between the adjacent formed fixed comb teeth is removed. Possessing:

7. A vibration power generation device characterized by comprising: the MEMS element according to claim 6; a movable portion having a plurality of movable comb teeth engaged with the fixed comb teeth of the first upper layer; an elastic support portion elastically supporting the movable portion; and an output portion outputting power generated by movement of electric charges generated by relative movement of the fixed comb teeth and the movable comb teeth. ​ ​

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