MEMS element and vibration power generation device

Abstract

The MEMS element includes a base, a movable part, an elastic part and a fixed part. The elastic part extends in a direction intersecting the moving direction of the movable part, has a central part that bears the force of the movable part, and one end and the other end fixed to the fixed part body, and has a thin-walled part between the central part and the one end, and between the central part and the other end, respectively, with a wall thickness thinner than that of the central part, one end and the other end.

Description

Technical Field

[0001] The present invention relates to a MEMS element and a vibration power generation device. Background Art

[0002] In the past, there is a known vibration power generation device formed by processing a silicon substrate using MEMS (Micro Electro-Mechanical System) processing technology. The vibration power generation device has a structure in which the comb teeth provided on the movable electrode supported by the elastic support portion are provided on the comb teeth provided on the fixed electrode in a manner that can be inserted and removed. If an impact from the outside is applied to the vibration power generation device, the elastically supported movable electrode vibrates relative to the fixed electrode, and the comb teeth of the movable electrode are inserted and removed relative to the comb teeth of the fixed electrode, resulting in power generation.

[0003] The fixed electrode as the fixed part is subjected to the acceleration generated by the vibration from the outside on the movable electrode as the movable part by the elastic limiting component provided on the fixed electrode, thereby limiting the vibration range of the movable electrode. Therefore, the elastic limiting component of the fixed electrode needs to have a rigidity that can withstand the force generated by the acceleration of the movable electrode. However, in the existing MEMS element, if the spring constant of the elastic limiting component is increased, the stress is concentrated on the base of the elastic part of the elastic limiting component, which is easy to be damaged, and it is difficult to increase the power that can be generated.

[0004] As an example of a structure in which an elastic restricting member is provided on a fixed electrode, there is a structure in which a slit is provided inside a side portion of a fixed electrode and the side portion of the fixed electrode is provided as an elastic restricting member (for example, see Patent Document 1). Figure 5 ).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2018-88780 Summary of the invention

[0008] Problems to be solved by the invention

[0009] In Patent Document 1 Figure 5 , a structure is shown in which a slit extending along the side surface is provided inside the side surface of the fixed part against which the movable electrode collides. However, this structure has a limit in withstanding the large force generated by the vibration of the movable part.

[0010] Solutions to Solve Problems

[0011] The MEMS element of the first scheme of the present invention comprises: a base; a movable part, at least a part of which is fixed to the above-mentioned base and can move in a predetermined direction; and a fixed part, at least a part of which is fixed to the above-mentioned base and has an elastic part arranged opposite to the above-mentioned movable part and a fixed part body to which the above-mentioned elastic part is fixed, the above-mentioned elastic part extends in a direction intersecting with the moving direction of the above-mentioned movable part, and has a central part that receives the force of the above-mentioned movable part and one end and the other end fixed to the above-mentioned fixed part body, and between the above-mentioned central part and the above-mentioned one end, and between the above-mentioned central part and the above-mentioned other end, there are thin-walled parts with a wall thickness thinner than the above-mentioned central part, the above-mentioned one end, and the above-mentioned other end, respectively.

[0012] According to a second aspect of the present invention, in the MEMS element of the first aspect, it is preferable that a gently curved surface is formed between the central portion and the thin-walled portion of the elastic portion.

[0013] According to a third aspect of the present invention, in the MEMS element of the first or second aspect, preferably, a side surface of the central portion of the elastic portion facing the movable portion protrudes further toward the movable portion than the thin-walled portion.

[0014] According to a fourth aspect of the present invention, in the MEMS element of the first or second aspect, preferably, a protrusion facing the central portion of the fixed portion is formed on a side surface of the movable portion facing the fixed portion.

[0015] According to the 5th scheme of the present invention, in the MEMS element of any one of the 1st to 3rd schemes, a slit is preferably provided between the elastic part and the fixed part body, the slit extends along the elastic part and penetrates the fixed part body, and the side surface of the elastic part facing the movable part is formed into a gently curved surface in which the stress generated by the force borne by the movable part becomes roughly uniform on the surface of the central part and the surface of the thin-walled part.

[0016] According to the sixth scheme of the present invention, in the MEMS element of any one of the first to third schemes, it is preferred that the elastic portion has four beam-forming portions, a slit extending along the elastic portion is provided between the elastic portion and the fixed portion body, at least one of the side surface of the elastic portion facing the movable portion and the side surface of the elastic portion on the slit side has a parabolic structure, and the parabolic structure includes: a first beam-forming portion having a parabolic curved surface whose base is fixed to one end of the fixed portion body; a second beam-forming portion having a parabolic curved surface connected to the first beam-forming portion at the vertex side; a third beam-forming portion having a parabolic curved surface integrated with the second beam-forming portion at the base; and a fourth beam-forming portion having a parabolic curved surface connected to the third beam-forming portion at the vertex side and whose base is fixed to the other end of the fixed portion body.

[0017] According to the 7th scheme of the present invention, in the MEMS element of the 6th scheme, it is preferred that the side surface of the elastic portion facing the movable portion has the following shape, i.e., a shape formed by joining a parabolic curved surface with the center of the central portion as a base end and a parabolic curved surface with the one end as a base end at the vertex side of each parabolic curved surface between the central portion and the one end, and the side surface on the slit side of the elastic portion is formed into a straight line.

[0018] According to an eighth aspect of the present invention, in the MEMS element of the sixth or seventh aspect, the thickness w(y) of the elastic portion is preferably set to substantially satisfy the following formula: Where: w(y) is the thickness of the parabolic beam at the position y from the center of the length of the beam, w 0 is the thickness of one end of the elastic portion, |y| is the absolute value of the length from the center of the beam length of the elastic portion to the position y, and L is the total length of the beam length of the elastic portion.

[0019] According to the 9th scheme of the present invention, in the MEMS element of the 1st scheme, a slit extending along the elastic part is preferably provided between the elastic part and the fixed part body, and the slit comprises: a first slit part, which is provided corresponding to the central part of the elastic part; and a second slit part, which is connected to the first slit part and is provided on the inner side near the one end and the other end of the elastic part, and the width of the second slit part in the moving direction of the movable part is larger than the width of the first slit part.

[0020] According to the 10th scheme of the present invention, in the MEMS element of the 9th scheme, a limiting portion is preferably provided in the area of ​​the fixed portion body opposite to the first slit portion, and the front end face of the limiting portion is the final limiting front end face that ultimately limits the force of the movable portion borne via the elastic portion.

[0021] The MEMS element of the 11th scheme of the present invention comprises: a base; a movable part, at least a part of which is fixed to the base and can move in a predetermined direction; and a fixed part, which has a fixed part body at least a part of which is fixed to the base, an elastic part fixed to the fixed part body, and a slit between the elastic part and the fixed part body extending along the elastic part and penetrating the fixed part body, wherein the elastic part extends in a direction intersecting with the moving direction of the movable part and has a central part receiving the force of the movable part and one end and the other end fixed to the fixed part body. The beam structure has a first slit portion, which is arranged corresponding to the central portion of the elastic portion; and a second slit portion, which is connected to the first slit portion and is arranged on the inner side near the one end and the other end of the elastic portion, the width of the movable portion of the second slit portion in the moving direction is formed to be larger than the width of the first slit portion, and an arc-shaped curved portion is provided at a corner portion on the one end side and the other end side of the elastic portion of the second slit portion, and the curvature radius of the arc-shaped curved portion is larger than the curvature radius of a circle inscribed in the first slit portion.

[0022] According to the 12th aspect of the present invention, in the MEMS element of the 11th aspect, the elastic portion preferably has a thin-walled portion between the central portion and the one end and between the central portion and the other end, the wall thickness of which is thinner than that of the central portion, the one end and the other end.

[0023] According to a thirteenth aspect of the present invention, in the MEMS element according to any one of the first to twelfth aspects, it is preferred that the base, the fixed portion, and the movable portion are formed of silicon.

[0024] According to the 14th aspect of the present invention, in the MEMS element of the 13th aspect, the movable part preferably has a plurality of movable comb teeth and a comb tooth connecting part connecting the plurality of movable comb teeth, and the fixed part preferably has a plurality of fixed comb teeth that are inserted and removed relative to the plurality of movable comb teeth of the movable part.

[0025] According to a fifteenth aspect of the present invention, in the MEMS element according to the fourteenth aspect, it is preferable that an electret is formed on at least one of each of the movable comb teeth and the fixed comb teeth.

[0026] The vibration power generating device of the 16th scheme of the present invention comprises: the MEMS element described in any one of the 1st to 15th schemes; an elastic supporting portion, which elastically supports the above-mentioned movable portion of the above-mentioned MEMS element on the above-mentioned fixed portion; and an output portion, which outputs the electric power generated by the vibration of the above-mentioned movable portion relative to the above-mentioned fixed portion.

[0027] Effects of the Invention

[0028] According to the present invention, in a MEMS element or a vibration power generating device having a structure for limiting the displacement amount of a movable portion, it is possible to provide a MEMS element or a vibration power generating device which is unlikely to be damaged even when a large external force acts. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 (A) is a top view showing a vibration power generation device with a MEMS element sealed in a vacuum package through an upper cover. Figure 1 (B) Yes Figure 1 (A) I B -I B Line section view.

[0030] Figure 2 (A) Yes Figure 1 (A) A top view of the MEMS element shown, Figure 2 (B) means from Figure 2 (A) is a plan view of the MEMS element shown in the figure with the fixed electrode portion and the movable electrode portion removed.

[0031] Figure 3 (A) Yes Figure 1 (A) Region III A The enlarged picture of Figure 3 (B) Yes Figure 3 (A) Region III B Magnified image of .

[0032] Figure 4 This is a schematic diagram of an approximately equal beam using a parabola. Figure 4 (A) is a side view showing the shape of the elastic portion in which the stress is substantially uniform over the entire length of the side surface. Figure 4 (B) Yes Figure 4 (A) Region IV B Magnified image of .

[0033] Figure 5 yes Figure 4 Other schematic diagrams of parabolic beams are shown, which are side views of the beam.

[0034] Figure 6 This is a diagram showing the relationship between the movable portion amplitude and the acceleration applied to the vibration power generating device in the comparative example and the present embodiment.

[0035] Figure 7 This is a three-dimensional diagram showing the stress distribution generated in the elastic part through simulation. Figure 7 (A) is the structure of a comparative example, Figure 7 (B) is a diagram showing the structure of this embodiment.

[0036] Figure 8(A) is a schematic diagram of a rectangular beam fixed at both ends (hereinafter referred to as a rectangular beam). Figure 8 (B) indicates Figure 8 (A) The cross-sectional shape, Figure 8 (C) Yes Figure 8 (A) Bending stress distribution diagram, Figure 8 (D) Yes Figure 8 (A) Bending moment diagram, Figure 8 (E) indicates Figure 8 (A) Bending stress on the lower surface side surface of the beam in the x-axis direction shown in the figure.

[0037] Fig. 9 (A) is a schematic diagram of a parabolic beam with both ends fixed. Fig. 9 (B) indicates Fig. 9 (A) The cross-sectional shape, Fig. 9 (C) Yes Fig. 9 (A) Bending moment diagram, Fig. 9 (D) Yes Fig. 9 (A) Bending stress on the lower surface side surface of the beam in the x-axis direction shown in the figure.

[0038] Fig.10 It is a plan view showing a modified example of the structure of the movable part and the fixed part constituting the MEMS element. DETAILED DESCRIPTION

[0039] Hereinafter, the mode for carrying out the present invention will be described with reference to the accompanying drawings.

[0040] Figure 1 (A) is a top view showing the vibration power generating device 1 in which the MEMS element 10 is sealed in the vacuum package through the upper cover 3. Figure 1 (B) Yes Figure 1 (A) I B -I B Line section view.

[0041] The housing 2 and the upper cover 3 form a vacuum package, and the MEMS element 10 is accommodated in the vacuum package. Figure 1 In the plan view of (A), in order to clearly show the planar structure of the MEMS element 10, the upper cover 3 provided on the upper surface side (z-axis positive direction side) is omitted from illustration.

[0042] In addition, in the present embodiment, the x-axis direction, the y-axis direction, and the z-axis direction are set to the directions shown in the respective drawings.

[0043] The MEMS element 10 includes four fixed electrode portions 11, a movable electrode portion (movable portion) 12, and an elastic support portion 13 for elastically supporting the movable electrode portion 12. The base 7 of the MEMS element is fixed to the housing 2 by die bonding. The housing 2 is formed of, for example, an electrically insulating material (e.g., ceramic). An upper cover 3 for vacuum sealing the housing 2 is seam-welded at the upper end of the housing 2.

[0044] The MEMS element 10 includes: a base 7 composed of Si; a device layer 9 composed of a Si active layer; and a SiO 2 The bonding layer 8 is formed of an inorganic insulating material such as Figure 1 As shown in (B), the MEMS element 10 is composed of a three-layer structure, which is a structure in which a base 7, a bonding layer 8, and a device layer 9 composed of a Si active layer are stacked in the z direction. The MEMS element 10 composed in this way is usually formed using a SOI (Silicon On Insulator) substrate using a common MEMS processing technology.

[0045] Four fixed electrode portions 11, a movable electrode portion 12, and a fixed electrode peripheral portion 35 are formed on the device layer 9. Each fixed electrode portion 11 has a plurality of fixed comb teeth 110, a fixed comb tooth connecting portion 111 connecting 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 in the y-axis direction at predetermined intervals. The fixed comb tooth connecting portion 111 extends in the y-axis direction and connects 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 connecting portion 111, i.e., in the x-axis direction. A rectangular terminal portion is formed at the front end portion of the lead portion 112. A conductive metal such as aluminum is provided on the upper surface of the terminal portion and an electrode pad 113 is formed.

[0046] Although not shown in the figure, a gap is formed between the fixed electrode 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 peripheral portion 35 is physically separated from the lead portion 112 and the fixed comb-tooth connecting portion 111 of each fixed electrode portion 11. As a result, the fixed electrode 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 bonding layer 8. The fixed comb teeth 110 of each fixed electrode portion 11 are connected to the rectangular opening 7a (see FIG. 1 ) provided in the base 7. Figure 1 (B) Figure 2 (A) and (B)) correspond to the area.

[0047] The movable electrode portion 12 includes a plurality of movable comb teeth 120 and a central band portion 121 (see Figure 1 (B)), and a movable comb tooth connecting portion 122 connecting a plurality of movable comb teeth 120. The movable comb tooth connecting portion 122 extends from the center of the central belt portion 121 in the x-axis direction in the positive direction of the y-axis and the negative direction of the y-axis. The movable comb teeth 120 extend from each movable comb tooth connecting portion 122 extending in the positive direction of the y-axis and the negative direction of the y-axis in the positive direction of the x-axis or the negative direction of the x-axis, and are arranged in the y-axis direction at a predetermined interval.

[0048] Weights 105a and 105b are fixed by bonding or the like 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 belt portion 121 of the movable electrode portion 12. The center of gravity of each of the weights 105a and 105b is coaxial with the z-axis passing through the center of the central belt portion 121 in the x-axis direction and the y-axis direction.

[0049] The two fixed electrode portions 11 of the central belt portion 121 arranged on the positive side of the y-axis are arranged line-symmetrically with respect to the center line of the central belt portion 121 in the x-axis direction. In addition, the other two fixed electrode portions 11 of the central belt portion 121 arranged on the negative side of the y-axis are arranged line-symmetrically with respect to the center line of the central belt portion 121 in the x-axis direction.

[0050] The plurality of fixed comb teeth 110 extending from the fixed comb tooth connecting portion 111 in the x-axis direction and the movable comb teeth 120 extending from each movable comb tooth connecting portion 122 in the x-axis direction are arranged to mesh with each other with a gap therebetween in the y-axis direction.

[0051] The movable electrode portion 12 is mechanically and electrically connected to the fixing portion 150 via the elastic support portion 13, and the fixing portion 150 is fixed to the base 7 via the bonding layer 8. The fixing portion 150 is provided in one pair in the positive direction of the x-axis and in the negative direction of the x-axis of the central belt portion 121. The pair of fixing portions 150 are formed in the same shape and are arranged to be line-symmetrical with respect to the central axis of the central belt portion 121 in the x-axis direction. The center line of each fixing portion 150 in the y-axis direction is coaxial with the center line of the central belt portion 121 in the y-axis direction.

[0052] 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 (see Figure 3) collides with the fixed portion 150. At this time, if the position of the abutment portion of the fixed portion 150 that the movable portion collides with in the y-axis direction is offset from the central axis passing through the center of gravity of the central belt portion 121 including the weights 105a and 105b in the y-axis direction, a moment is generated in the central belt portion 121 of the movable electrode portion 12. If a moment is generated in the central belt portion 121 of the movable electrode portion 12, deformation occurs in the elastic support portion 13, and the central belt portion 121 cannot vibrate normally. Therefore, the center line in the y-axis direction of the abutment portion of the fixed portion 150 that the central belt portion 121 of the movable electrode portion 12 collides with needs to be coaxial with the center line of the central belt portion 121 of the movable electrode portion 12 extending in the x-axis direction.

[0053] The electrode pad 114 is connected to the fixing portion 150. A rectangular terminal portion is integrally formed on the fixing portion 150, and a conductive metal such as aluminum is provided on the upper surface of the terminal portion and the electrode pad 114 is formed.

[0054] The electrode pads 113 and 114 are connected to electrodes 21 a and 21 b provided on the housing 2 through metal wires 22 , respectively.

[0055] Electrets are formed on the fixed electrode section 11 and the movable electrode section 12. When an electret is formed on only one of the fixed electrode section 11 and the movable electrode section 12, charges of opposite polarity are generated on the other. Therefore, an electret may be formed on only one of the fixed electrode section 11 and the movable electrode section 12.

[0056] In this embodiment, the movable electrode portion 12 is configured to vibrate in the x-axis direction. When the movable electrode portion 12 vibrates in the x-axis direction, the insertion amount of the movable comb teeth 120 of the movable electrode portion 12 relative to the fixed comb teeth 110 of the fixed electrode portion 11 changes, causing the movement of charges to generate electricity.

[0057] Figure 2 (A) is a diagram showing the MEMS element 10 before the hammers 105a and 105b are fastened.

[0058] As described above, the MEMS element 10 is formed using a SOI (Silicon On Insulator) substrate using a conventional MEMS processing technology. The SOI substrate is composed of a three-layer structure, which is a structure in which a base 7, a bonding layer 8, and a device layer 9 composed of a Si active layer are stacked in the z direction. Figure 1 As shown in (B), the device layer 9 is supported by the base 7 via the bonding layer 8. The fixed electrode portion 11, the movable electrode portion 12, and the elastic support portion 13 are formed of a Si active layer.

[0059] exist Figure 2In (A), the fixed electrode portion 11, the movable electrode portion 12, the elastic support portion 13 and the fixed portion 150 on the base 7 are shown 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 that can be elastically deformed. The movable electrode portion 12 is arranged on an area corresponding to the opening portion 7a provided on the base 7. The movable electrode portion 12 is connected to the fixed portion 150 via the beams 13a to 13c of the elastic support portion 13. The fixed portion 150 is fixed to the base 7 via the bonding layer 8. Therefore, the movable electrode portion 12 is supported on the base 7 via the four elastic support portions 13 and the fixed portion 150.

[0060] The fixing portion 150 functions as a limiting portion that limits the range of vibration of the movable electrode portion 12 in the x-axis direction. Figure 3 As shown in FIG. 5A , each fixing portion 150 includes a fixing portion body 151 , an elastic portion 152 , and a slit 153 provided between the fixing portion body 151 and the elastic portion 152 .

[0061] The vibration of the movable electrode portion 12 in the x-axis direction is limited by the collision of the movable electrode portion 12 with each fixed portion 150 and the deformation of the elastic portion 152. That is, the force of the movable electrode portion 12 acts on the fixed portion 150. The fixed portion 150 needs to have the rigidity to withstand the force of the movable electrode portion 12 without damage. By adopting the fixed portion 150 of this embodiment, it is possible to prevent damage even when a larger acceleration acts on the MEMS element 10 in the x-axis direction than before, and it has a structure that can achieve miniaturization. This will be described later.

[0062] Figure 2 (B) means from Figure 2 (A) is a plan view of the MEMS element 10 shown in FIG. 1 , in which the fixed electrode portion 11 and the movable electrode portion 12 are removed. Figure 2 A hatched area 11C in (B) shows a pattern of a joining portion where the fixed comb-tooth connecting portion 111 and the lead portion 112 of each fixed electrode portion 11 are joined to the joining layer 8 . Figure 3 The hatched area 11A in (B) shows the pattern of the joint where the end of the beam 13 a of the elastic support portion 13 is joined to the joint layer 8 . Figure 3 The hatched area 11B in (B) shows the pattern of the bonding portion where the fixing portion 150 and the bonding layer 8 are bonded.

[0063] Figure 3 (A) Yes Figure 1 (A) Region III A The enlarged picture of Figure 3 (B) Yes Figure 3 (A) Region III BThe fixing portion 150 includes a fixing portion body 151, an elastic portion 152, and a slit 153 provided between the fixing portion body 151 and the elastic portion 152. The central axis of the fixing portion 150 in the y-axis direction is coaxial with the central axis of the central band portion 121 of the movable electrode portion 12 in the y-axis direction.

[0064] The elastic portion 152 extends along one side surface 121a in the x-axis direction of the central belt portion 121. The elastic portion 152 is composed of four beam components 152a to 152d, beam components 152a and 152b, and two beam component connecting portions 154 connecting beam components 152c and 152d.

[0065] Figure 4 (A) is a schematic diagram for explaining the surface shape of the elastic part 152, showing an elastic part 251 composed of a parabolic beam 252, which is a double-branched beam formed by four beam components 252a to 252d. The four beam components 252a each have a parabolic shape, and constitute a substantially equal beam that can obtain a substantially uniform stress distribution over the entire length of the double-branched beam.

[0066] The apex of the parabola of the beam component 252a is connected to the apex of the parabola of the beam component 252b by the beam component connecting portion 254. The apex of the parabola of the beam component 252c is connected to the apex of the parabola of the beam component 252d by the beam component connecting portion 254.

[0067] Figure 3 The elastic portion 152 is a substantially equal beam having four beam components 152a to 152d. Figure 4 In the shape of the parabolic beam 252, the side surface of the right region bounded by the axis of the parabola of each beam component 252a to 252d is configured as a flat beam.

[0068] In addition, the following text explains Figure 4 Beam structure.

[0069] return Figure 3 The elastic portion 152 and the central belt portion 121 have surfaces facing each other. Figure 4The beam components 252a to 252d have the same parabolic profile. The beam components 152a and 152b, and the beam components 152c and 152d are connected by the beam component connecting portion 154 on the vertex side of the parabola. In addition, the beam components 152b and 152c are connected on the opposite side of the vertex of the parabola. Hereinafter, the opposite side of the vertex of the parabola is referred to as the base side. The beam components 152a and 152d are respectively integrated with one end 151T and the other end 152T of the fixing portion main body 151 in the y-axis direction, and the elastic portion 152 functions as a double-branched beam.

[0070] The slit 153 extends in the y-axis direction parallel to the side surface 121a of the central belt portion 121 at the end of the fixed portion main body 151 against which the central belt portion 121 of the movable electrode portion 12 collides. The slit 153 forms the elastic portion 152 as a double-branched beam.

[0071] The slit 153 includes a first slit portion 153a formed in the central portion in the y-axis direction, in other words, in the region corresponding to the beam forming portion 152b and the beam forming portion 152c; and a second slit portion 153b formed in both ends in the y-axis direction, that is, in the region corresponding to the beam forming portion connecting portion 154. The two second slit portions 153b have substantially the same shape and size. The width of the first slit portion 153a in the x-axis direction defines the maximum displacement of the elastic portion 152 in the x-axis direction, and the first slit portion 153a is formed between the side surface of the beam forming portion 152b and the beam forming portion 152c on the slit 153 side and the final limiting front end surface 164 of the protruding portion 151a in the slit 153. The width of the first slit portion 153a, in other words, the length in the x-axis direction is smaller than the width of the second slit portion 153b in the x-axis direction.

[0072] The second slit portion 153 b is formed in a semicircular shape near the corner portion 171 of the fixing portion body 151 .

[0073] The center of the connection part of the beam-forming part 152b and the beam-forming part 152c in the y-axis direction is coaxial with the center of the central belt part 121 in the y-axis direction. The side surface 161 of the connection part of the beam-forming part 152b and the beam-forming part 152c protrudes in the elastic part 152 so as to be closest to the one side surface 121a of the central belt part 121. The side surface 162 of the two beam-forming part connection parts 154 is farthest from the one side surface 121a of the central belt part 121 in the elastic part 152. Therefore, the wall thickness of the beam-forming part connection part 154, that is, the length in the x-axis direction is smaller than the wall thickness of the connection part of the beam-forming part 152b and the beam-forming part 152c.

[0074] That is, the elastic portion 152 has a structure including a thick central portion, one end, and the other end, and thin portions thinner than the central portion between the central portion and the one end and between the central portion and the other end.

[0075] Next, an operation of limiting the vibration range of the movable electrode section 12 by the fixing section 150 will be described.

[0076] When the central belt portion 121 moves in the x-axis direction due to the vibration of the movable electrode portion 12, the side surface 121a of the central belt portion 121 collides with the side surface 161 of the connecting portion of the elastic portion 152 of the fixed portion 150. The elastic portion 152 of the fixed portion 150 is pushed and deformed by the side surface 121a of the central belt portion 121, and the inner side surface 163 of the elastic portion 152 facing the first slit portion 153a abuts against the final limiting front end surface 164 of the protruding portion 151a of the fixed portion body 151 facing the first slit portion 153a, and the movement of the central belt portion 121 in the x-axis direction stops at this position. That is, the final limiting front end surface 164 of the fixed portion body 151 serves as a limiting portion that limits the range of vibration of the central belt portion 121, that is, the movable electrode portion 12.

[0077] When the elastic part 152 collides with the final limiting front end surface 164, the movable electrode part 12 stops. As in the conventional structure, the width of the slit is set to a value corresponding to the maximum displacement of the movable electrode part 12, and the width of the slit is set to be the same size over the entire length of the elastic part in the y-axis direction, and if the cross-sectional shape of the elastic part is set to be a uniform rectangle over the entire length in the y-axis direction, the stress generated near the corners 171 at both ends of the slit 153 of the elastic part 152 in the y-axis direction is concentrated, and the corners 171 at both ends of the elastic part 152 in the y-axis direction are more likely to be damaged.

[0078] As a comparative example, consider the following elastic part structure: as the slit 153 formed in the fixing part 150, only the first slit part 153a is provided, and the first slit part 153a extends to both ends of the fixing part body 151 in the y-axis direction, and the cross-sectional shape is set to be a uniform rectangular shape throughout the entire length of the beam. In the structure of this comparative example, Figure 3 As shown in FIG. 5B , the curvature radius of the semicircle of the corners 171 formed at both ends of the fixing portion main body 151 in the y-axis direction of the first slit portion 153 a is equal to the radius Ra of the circle inscribed in the first slit portion 153 a .

[0079] In view of this, in the present embodiment, the elastic portion 152 is set to be a substantially equal beam, which has a greater bending rigidity, in other words, a greater spring constant, than the beam of the comparative example, and the stress is substantially equal over the entire length of the beam. Therefore, in terms of the magnitude of the elastic energy (energy to absorb impact) possessed by the elastic portion 152, the beam of the embodiment is larger than the beam of the comparative example. In addition, a second slit portion 153b having a width greater than that of the first slit portion 153a is provided on both sides of the first slit portion 153a in the y-axis direction. Therefore, the curvature radius Rb of the second slit portion 153b formed at the corners of the two end sides of the fixed portion main body 151 in the y-axis direction can be set to be larger than the curvature radius Ra of the first slit portion 153a. Therefore, the concentrated stress generated at the corners of the two end sides of the fixed portion main body 151 in the y-axis direction can be alleviated.

[0080] The width of the first slit portion 153a can be set to about 10 to 20 μm, for example. On the other hand, the width of the second slit portion 153b can be set to 50 μm or more, for example. However, the above-mentioned width dimensions are examples shown for reference only, and an optimal width dimension can be appropriately adopted.

[0081] in addition, Figure 3 The side surface of the elastic portion 152 is formed as a gently curved surface from the side surface 161 of the center portion in the y-axis direction toward the side surface 162 of the beam-forming portion connecting portion 154. Therefore, the stress distribution between the side surface 161 of the base connecting portion and the side surface 162 of the beam-forming portion connecting portion 154 can be made substantially uniform.

[0082] and, Figure 3 The illustrated fixing portion 150 has second slits 153b on both sides of the first slit 153a in the y-axis direction, so the length of the first slit 153a in the y-axis direction, in other words, the length of the final limiting front end surface 164 is shortened. This can improve the exhaust performance of the reaction gas as described below.

[0083] Typically, the slit 153 is formed by DRIE (Deep Reactive Ion Etching).

[0084] In etching using DRIE, in order to increase the reaction speed with Si as the etched material, it is important that the reaction gas after the reaction is completed has good discharge properties when it flows out from the slit. When the slit width for etching is narrow and long in the extending direction, the discharge properties of the reaction gas flowing out of the slit deteriorate, and the processing time becomes longer. In this embodiment, since the length of the first slit portion 153a in the y-axis direction, in other words, the length of the direction orthogonal to the slit width direction, is shortened, the discharge properties of the reaction gas discharged from the slit after the reaction are completed become good, and the efficiency of the processing time of the slit 153 can be achieved.

[0085] Figure 6 It is a diagram showing the relationship between the movable portion amplitude and the acceleration applied to the vibration power generating device 1 in the comparative example and the present embodiment.

[0086] Figure 6 The vertical axis is the amplitude of the movable part, and the horizontal axis is the acceleration applied to the vibration power generating device 1. The point T1 on the vertical axis is the position where the side surface 121a of the central belt portion 121 contacts the side surface 161 of the elastic portion 152 of the fixed portion 150. In addition, the point T2 on the vertical axis is the position where the inner side surface 163 of the elastic portion 152 contacts the final limiting front end surface 164 of the fixed portion body 151. When the elastic portion 152 moves from the position T1 to T2 and deforms, the impact energy acting on the MEMS element 10 is absorbed.

[0087] The movable electrode portion 12 starts to vibrate until one side surface 121a of the central band portion 121 reaches point T1. Regardless of whether the spring constant of the elastic portion 152 is large or small, the relationship between the movable portion amplitude and the acceleration applied to the vibration power generating device 1 is the same, which is represented by the relationship of the straight line Lc.

[0088] When the spring constant of the elastic portion 152 provided in the fixed portion 150 is small, the movable electrode portion 12 moves as shown in the straight line L. w As shown in FIG. 1 , the slope of the amplitude increase of the movable electrode portion 12 is small, and in this state, the side surface 121a of the central band portion 121 reaches the point T2. That is, when the spring constant of the elastic portion 152 is small, the acceleration α applied to the vibration power generating device 1 when the side surface 121a of the central band portion 121 reaches the point T2 is w In contrast, when the spring constant of the elastic portion 152 provided in the fixed portion 150 is large, the movable electrode portion 12 moves as shown in the straight line L. s As shown in FIG. 1 , even if the acceleration applied to the vibration power generating device 1 exceeds the acceleration α w , the force of the movable electrode portion 12 continues to be received. Then, when the acceleration reaches a predetermined magnitude α s That is, when the spring constant of the elastic portion 152 is large, the acceleration α applied to the vibration power generating device 1 when the side surface 121a of the central belt portion 121 reaches the point T2 is s Specific acceleration α w big.

[0089] In this way, by increasing the spring constant of the elastic portion 152 of the fixed portion 150, the energy absorbed when the movable electrode portion 12 is deformed by a distance T2-T1 after colliding with the fixed portion 150 increases, and compared with the comparative example, even when a larger acceleration acts, damage to the MEMS element 10 can be prevented. The absorbed energy will be described later.

[0090] In this embodiment, the slit 153 formed in the fixed portion 150 is composed of a first slit portion 153a with a small slit width for limiting the movement of the movable electrode portion 12, and a second slit portion 153b with a large slit width that is continuous with the first slit portion 153a and extends to the vicinity of the corner 171 of the fixed portion 150. In addition, the corner 171 side of the second slit portion 153b is formed into an arc shape with a large curvature radius. In addition, the side surface of the central band portion 121 side of the elastic portion 152 is formed into a gently curved surface from the side surface 161 of the central portion in the y-axis direction toward the side surface 162 of the beam-forming portion connecting portion 154.

[0091] Therefore, even if the acceleration acting on the MEMS element 10 from the outside increases, the elastic part 152 can make uniform the stress generated in the region from the corner 171 fixed to the fixing part body 151 and the side surface 161 of the elastic part 152 to the side surface 162 of the beam-forming part connecting part 154. Thus, the elastic part 152 can be miniaturized and an elastic part with a large spring constant can be obtained.

[0092] In addition, the elastic part 152 of the fixing part 150 is made into a rectangular beam structure like the comparative example, and the stress is substantially equal over the entire length of the beam, which is different from the beam structure with the same cross-sectional area, and the spring constant is made larger than the spring constant of the beam of the comparative example. In other words, the spring constant is set to be larger than the spring constant of the beam of the comparative example. Therefore, Figure 6 As described in the text, even if the slit width of the first slit portion 153a is made equal to the slit width of the comparative example, in other words, even if the movable range of the movable electrode portion is the same, it is possible to prevent damage to the elastic portion 152 when the MEMS element 10 falls or collides with other components when the MEMS element 10 is installed.

[0093] Reference Figure 7 , stress distribution in comparative examples and embodiments is described.

[0094] Figure 7 (A) is a three-dimensional diagram showing the stress distribution generated in the elastic part 301 based on simulation when a concentrated load f is applied to the center of the y-axis direction of the elastic part 301 which is a double-branched beam having a rectangular shape and a uniform cross-sectional area over the entire length. The elastic part 301 is formed of Si. In addition, the elastic part 301 is a beam equivalent to the elastic part of the above-mentioned comparative example.

[0095] Figure 7 (B) is a diagram for explaining the parabolic beam 252 having four beam components 252a to 252d according to the embodiment and the Figure 4 The schematic diagram of the beam is equivalent to the stereogram of the beam.

[0096] exist Figure 7 In (A) and (B), hatching A indicates a larger stress, hatching C indicates a smaller stress, and hatching B indicates an intermediate stress.

[0097] like Figure 7 As shown in FIG. 1A , a large stress is generated on the surface of the side surface in the positive direction of the x-axis and the negative direction of the x-axis of the middle portion 301m in the y-axis direction of the elastic portion 301. In addition, a large stress is also generated on the surface of the side surface in the positive direction of the x-axis and the negative direction of the x-axis on the side of one end 301ta and the other end 301tb of the elastic portion 301 in the y-axis direction.

[0098] On the other hand, the stress generated on the surface between the middle portion 301m in the y-axis direction and one end 301ta of the elastic portion 301 and between the middle portion 301m in the y-axis direction and the other end 301tb of the elastic portion 301 is small.

[0099] It can be seen from this that in the rectangular beam, the stress generated in the region between the middle portion 301m in the y-axis direction and one end 301ta and the other end 301tb in the y-axis direction is small, so there is room for reducing the rigidity of this region.

[0100] Here, Figure 4 The approximately equal beams are described in detail.

[0101] Figure 4 (A) is a side view showing the shape of the elastic portion in which stress is substantially uniform over the entire length of the side surface. Figure 4 (B) Yes Figure 4 (A) Region IV B Magnified image of .

[0102] The parabolic beam 252 includes: first to fourth beam components 252a to 252d; and two beam component connecting parts 254 connecting the first beam component 252a to the second beam component 252b, and the third beam component 252c to the fourth beam component 252d. The four beam components, the first to fourth beam components 252a to 252d, each have a parabolic profile.

[0103] like Figure 4As shown in FIG. (B), the first beam component 252a and the second beam component 252b, and the third beam component 252c and the fourth beam component 252d are connected on the vertex side of the parabola by the beam component connecting portion 254. In a state where the vertex of the first beam component 252a is in contact with the vertex of the second beam component 252b, the vicinity of the vertices of the first and second beam components 252a and 252b are integrated to form the beam component connecting portion 254. Similarly, in a state where the vertex of the third beam component 252c is in contact with the vertex of the fourth beam component 252d, the vicinity of the vertices of the third and fourth beam components 252c and 252d are integrated to form the beam component connecting portion 254.

[0104] In addition, the second beam configuration part 252b and the third beam configuration part 252c are integrated on the base side of the parabola, and the base side of the first beam configuration part 252a and the base side of the fourth beam configuration part 252d are fixed.

[0105] Below, link Figure 4 The fixed beams at both ends of the four parabolic beams shown in the figure are called parabolic beams. Figure 3 The elastic portion 152 is Figure 4 The side surface of the area to the right of the axis of the parabola is made into a flat beam structure, and the elastic portion 152 is also called a parabolic beam.

[0106] By making the elastic part 152 into a parabolic beam, the elastic part 152 is similar to the comparative example having a rectangular cross section over the entire length. Figure 7 Compared with the rectangular beam of (A), the spring constant can be increased, and thus the elastic energy that the elastic portion 152 can retain can be increased.

[0107] Figure 7 This is a three-dimensional diagram showing the stress distribution generated in the elastic part through simulation. Figure 7 (A) is the structure of a comparative example, Figure 7 (B) is a diagram showing the structure of this embodiment.

[0108] Figure 7 (A) shows the stress distribution of a rectangular elastic portion 301 having a uniform cross-sectional area as a comparative example.

[0109] In the comparative example, as described above, a large stress is generated on the side surfaces in the positive direction of the x-axis and the negative direction of the x-axis on the middle portion 301m in the y-axis direction and the one end 301ta side and the other end 301tb of the elastic portion 301. In addition, the stress generated on the side surfaces between the middle portion 301m in the y-axis direction and the one end 301ta in the y-axis direction of the elastic portion 301 and between the middle portion 301m in the y-axis direction and the other end 301tb in the y-axis direction of the elastic portion 301 is small. That is, the magnitude of the stress generated in the elastic portion 301 is not uniform over the entire length, but is uneven.

[0110] Figure 7 (B) represents the maximum stress generated in the elastic part 251 formed by the parabolic beam and Figure 7 (A) Stress distribution in a state of deformation in the same manner as the maximum stress of the comparative example.

[0111] In by Figure 7 (B) In the elastic portion 251 formed by the parabolic beam 252 shown in the figure, it was confirmed that relatively large stress was generated on the side surfaces of the first to fourth beam components 252a to 252d in the positive direction of the x-axis and the negative direction of the x-axis in addition to the beam component connecting portion 254, and that the stress was substantially uniform over the entire surface of the side surfaces of the first to fourth beam components 252a to 252d.

[0112] Therefore, the maximum deflection amount of the elastic portion 301 of the comparative example is about 0.5 μm, and the maximum deflection amount of the elastic portion 251 formed of the parabolic beam 252 is about 1.0 μm.

[0113] In this way, by adopting a structure in which stress is generated substantially equally in the first to fourth beam-forming portions 252 a to 252 d , the spring constant can be increased, and the elastic energy that the elastic portion 251 can retain can be increased. The reason for this will be described below.

[0114] Furthermore, in order to explain the effects of the present embodiment by comparison, rectangular beams having the same cross-sectional area will be described first.

[0115] Figure 8 (A) is a schematic diagram of a rectangular beam fixed at both ends (hereinafter referred to as a rectangular beam). Figure 8 (B) indicates Figure 8 (A) The cross-sectional shape, Figure 8 (C) Yes Figure 8 (A) Bending stress distribution diagram, Figure 8 (D) Yes Figure 8 (A) Bending moment diagram, Figure 8 (E) indicates Figure 8 (A) Bending stress on the lower surface side surface of the beam in the x-axis direction shown in the figure.

[0116] Hereinafter, the length of the beam in the x-axis direction, in other words, the length in the bending direction is referred to as thickness, the length of the beam in the extending direction is referred to as beam length, and the length of the beam in the z-axis direction orthogonal to the x-axis direction and the y-axis direction is referred to as width.

[0117] The rectangular beam has a thickness w throughout the entire length of the beam. 1 , width b 1 The same rectangular cross-section. That is, the thickness of the beam w 1 and width b 1 It is constant at any position along the length of the beam. The two ends of the beam are fixed, and a concentrated load P1 is applied to the middle of the beam length. The position where the concentrated load P1 is applied is set as the origin 0, and the length from the origin is set as y. The length of the beam is set as L 1 Therefore, the positions y of one end of the beam and the other end are ±L 1 / 2.

[0118] Bending moment M1(y) at position y, bending stress σ on the lower surface side in the x-axis direction max1 (y) are represented by formula (1) and (2) respectively.

[0119] M 1 (y) = L 1 P 1 (1-4|y| / L 1 ) / 8 (1)

[0120] σ max1 (y) = M 1 (y) / Z 1 (2)

[0121] Z 1 is the profile coefficient, expressed by formula (3).

[0122] Z 1 =b 1 w 1 2 / 6 (3)

[0123] In a rectangular beam, the section modulus Z 1 is independent of y and is constant, so σ max1 (y) and M 1 (y). Therefore, Figure 8 (D) The |M 1 (y)|The maximum position (y=0, y=±L 1 / 2), |σ max1 (y)|Take the maximum value σ 1 (Refer to ( Figure 8 (E)).

[0124] That is, formula (4) holds.

[0125] σ 1 =σ max1 (0) = 3L 1 P 1 / 4b 1 w 1 2 (4)

[0126] That is, at y = 0, y = ±L 1 / 2, stress is concentrated. If the concentrated load P1 is increased, the area corresponding to this position exceeds the allowable stress and the beam is broken. At this time, there is a surplus of stress in the area outside this area. Therefore, by improving the uneven stress in the rectangular beam and making it equal, the entire beam can be effectively utilized. This is like Figure 7 (A) As described with the comparative product shown in the figure.

[0127] Deflection δ 1 The bending moment and the section secondary moment are expressed by equation (5).

[0128] δ 1 =L 1 3 P 1 / 16Eb 1 w 1 3 (5)

[0129] Here, E is Young's modulus.

[0130] The parabolic beam will be described below.

[0131] Fig. 9 (A) is a schematic diagram of a parabolic beam with both ends fixed. Fig. 9 (B) indicates Fig. 9 (A) The cross-sectional shape, Fig. 9 (C) Yes Fig. 9 (A) Bending moment diagram, Fig. 9 (D) indicates Fig. 9 (A) Bending stress on the lower surface side surface of the beam in the x-axis direction shown in the figure.

[0132] In a parabolic beam, the width b of the cross section is constant at any position along the length of the beam, but the thickness w is a function of y. Let the thickness at position y along the length of the beam be w(y). The two ends of the beam are fixed, and a concentrated load P is applied to the middle of the length of the beam. Let the position where the concentrated load P is applied be the origin 0, and let the length from the origin be y. Let the length of the beam be L.

[0133] The thickness of the beam at one end and the other end of the parabola beam is w. 0(Refer to Fig. 9 (A)).

[0134] Let the function w(y) have the following symmetry.

[0135] (i) Symmetric with respect to y = 0

[0136] That is, w(-y) = w(y)

[0137] (ii) The part where 0≤y is symmetric with respect to y=L / 4

[0138] That is, w(L / 4-y)=w(L / 4+y)(x≥0)

[0139] According to the above symmetry, the bending moment M(y), the bending stress σ on the lower surface side in the x-axis direction max (y) are represented by equations (6) and (7) respectively.

[0140] M(y)=LP(1-4|y| / L) / 8 (6)

[0141] σ max (y) = M (y) / Z (y) (7)

[0142] Z(y) is the profile coefficient, expressed by equation (8).

[0143] Z(y)=bw(y) 2 / 6 (8)

[0144] Here, by appropriately choosing the function w(y), |σ max (y)| can be a constant value σ without depending on y.

[0145] |σ max (y)|=σ (9)

[0146] If equations (6), (7), and (8) are substituted into equation (9), we get equation (10).

[0147]

[0148] The thickness of the parabolic beam at one end and the other end is w(-L / 2) = w 0 , and the relationship between σ and w0 is obtained as equation (11).

[0149] σ=3LP / 4bw 0 2 (11)

[0150] According to formula (11), formula (10) becomes formula (10a).

[0151]

[0152] The absolute value of the bending stress on the lower surface side surface in the x-axis direction does not depend on the position y but depends on σ, and has a uniform distribution.

[0153] The deflection δ is calculated based on the bending moment and the section secondary moment and is expressed by equation (12).

[0154] δ=L 3 P / 8Ebw 0 3 (12)

[0155] If the shape of the parabolic beam shown in equation (10a) is Figure 4 .

[0156] Figure 4 The beam length L, position y, and thickness w of the beam at one end and the other end are shown. 0 Respectively with L, y, w in formula (10a) 0 correspond.

[0157] When the length from the center in the y-axis direction is y=±L / 4, the thickness of the beam becomes w(y)=0, but such a beam cannot bear the concentrated load P. Therefore, the surrounding area including this position is connected by the connecting portion.

[0158] The following describes the effect of replacing the elastic portion 152 from a rectangular beam to a parabolic beam. The replacement conditions are the same except for the thickness w of the beam.

[0159] That is, the width of the beam b 1 = b, beam length L 1 =L.

[0160] In addition, if the maximum stress of the beam reaches the allowable stress σ of the material 0 The deflection at 0 , then these conditions are met. That is, the deflection δ 1 =δ=δ 0 , bending stress σ 1 =σ=σ 0 .

[0161] That is, consider the case where both the rectangular beam and the parabolic beam are bent to the edge of failure and the amount of deflection is equal. In this case, according to equations (4), (5), (11), and (12), equation (13) holds.

[0162] w 0 / w 1 =2L 2 σδ 1 / L 1 2 σ 1δ=2 (13)

[0163] Formula (13) indicates that by making the elastic part 152 a parabolic beam, the thickness of one end and the other end of the elastic part 152 fixed to the fixing part 150 can be twice that of a rectangular beam. This suggests that the elastic energy that the elastic part 152 can hold can be increased.

[0164] Therefore, find the elastic energy that the rectangular beam and the parabolic beam can hold respectively.

[0165] The elastic energy U of the rectangular beam and the parabolic beam in the state of bending to the limit is 1 , U are represented by equations (14) and (15) respectively.

[0166] U 1 =P 1 δ 1 / 2 (14)

[0167] U=Pδ / 2 (15)

[0168] According to equations (4), (11) and (13), the above magnitudes satisfy the relationship shown in equation (16).

[0169] U / U 1 =Pδ / P 1 δ 1 =4 (16)

[0170] According to equation (16), by replacing the beam with a parabolic beam of the same length, the elastic energy that can be retained can be increased to four times that of the rectangular beam without causing damage.

[0171] Therefore, the elastic portion 152 having the parabolic beam structure has the effect of being able to maintain a vibration state against a large external vibration.

[0172] (Deformation of parabolic beam)

[0173] Figure 5 is shown as a schematic diagram Figure 4 The corresponding figure is Figure 3 Schematic diagram of an approximately equal beam of the embodiment shown.

[0174] Figure 4 The parabolic beam 252 shown in the figure has a structure in which four beam components have line-symmetric outlines with respect to an axis passing through the apex and parallel to the y-axis direction.

[0175] Figure 5 The elastic portion 261 shown in the figure has a parabolic beam structure in which one side surface extends linearly and only the side surface opposing the one side surface has a curved surface.

[0176] In the elastic portion 261 , a side surface 263 on the opposite side to the side facing the central band portion 121 of the movable electrode portion 12 extends linearly in the y-axis direction.

[0177] The four beam components 262a to 262d are connected to form the elastic component 261. The connection method is similar to Figure 4 The same as the parabolic beam 252 .

[0178] That is, the base of the beam component 262 a and the base of the beam component 262 d are fixed. The base of the beam component 262 b and the base of the beam component 262 c are integrated at the center of the elastic portion 261 in the y-axis direction.

[0179] The beam components 262a and 262b are connected at the beam component connection parts 264 on the respective apex sides. Also, the beam components 262c and 262d are connected at the beam component connection parts 264 on the respective apex sides.

[0180] The thickness of each beam component 262a to 262d in the x-axis direction at the position where the length from the center of the elastic portion 261 in the y-axis direction is y, in other words, the length from one side surface 263 to the curved surface side is equal to Figure 4 The thickness w(y) of the parabolic beam 252 shown in the figure is the same at the same position. Since the elastic part 261 is a structure in which only one side is bent, in other words, the thickness of each beam component is Figure 4 The distance from the illustrated parabolic beam 252 to an axis parallel to the y-axis passing through the vertex is twice the thickness.

[0181] In the present specification, the term "parabolic" is used as a term including shapes similar to a parabola in addition to a parabola.

[0182] In the elastic part 261, the thickness of each beam component is also Figure 4 The thickness of the corresponding y position in the illustrated parabolic beam 252 is the same, and thus acts as the Figure 4 The parabolic beam 252 shown in the figure constitutes the elastic portion 251 which has the same effect.

[0183] In the above description, the elastic parts 251 and 261 are exemplified as parts having a parabola or a parabola-shaped contour. However, it is not necessary to make the contour of the elastic parts 251 and 261 accurately a parabola or a parabola. Figure 7 As described in (A), in a rectangular beam, regions with low stress are generated between the center and one end and the other end of the fixed portion of the beam. Therefore, if a thin-walled portion is provided in the region with low stress and the rigidity is reduced, the stress on the entire surface of the elastic portion 251, 261 will be uniform, and a corresponding effect can be achieved.

[0184] In addition, in the above-mentioned embodiment, the following structure is illustrated, that is, the side surface of the elastic portion 152 of the fixing portion 150 is set as a curved surface, and the slit 153 provided between the elastic portion 152 and the fixing portion body is composed of a first slit portion 153a with a smaller slit width and a second slit portion 153b with a larger slit width than the first slit portion 153a.

[0185] However, the effect of making the contour of the elastic portion 152 parabolic or parabolic-shaped can be obtained regardless of whether the slit 153 is composed of a plurality of slits having different slit widths.

[0186] Furthermore, the effect achieved by the slit 153 being composed of a plurality of slits having different slit widths can be obtained regardless of whether the contour of the elastic portion 152 is a parabola or a parabola shape.

[0187] Therefore, the side surface of the elastic portion 152 may be formed as a curved surface, and the slit 153 may be formed of a plurality of slits having different slit widths. The MEMS element 10 may be formed by using each of these structures independently.

[0188] (Modifications of the Fixed Part and the Movable Part)

[0189] Fig.10 It is a plan view showing a modified example of the movable part and the fixed part.

[0190] Fig.10 The side surface 156 of the illustrated fixed portion 150 facing the central band portion 121 of the movable electrode portion 12 extends linearly in the y-axis direction, and no protruding surface is formed on the side surface 156. In contrast, a protruding portion 128 that protrudes toward the movable electrode portion 12 is provided on one side surface 121a of the central band portion 121 of the movable electrode portion 12 facing the fixed portion 150. The front end portion 128a of the protruding portion 128 is provided at a position corresponding to the center of the fixed portion 150 in the y-axis direction.

[0191] The slit 155 provided in the fixing portion 150 is composed of a first slit portion 155 a provided in the center portion and substantially circular second slit portions 155 b provided on both sides of the first slit portion 155 a in the y-axis direction.

[0192] In this way, the protrusion 128 may be provided on the side of the movable electrode section 12. In addition, the second slit section 155b may be circular or elliptical.

[0193] Furthermore, in the above-described embodiment, an example of a structure in which the elastic portion 152 is provided in the fixed portion 150 is described. However, the elastic portion 152 may be provided in the movable electrode portion 12 .

[0194] According to the above-described embodiment, the following effects are achieved.

[0195] (1) The MEMS element 10 includes: a base 7; a movable electrode portion (movable portion) 12; and a fixed portion 150 having an elastic portion 152 and a fixed portion body 151, wherein the elastic portion 152 extends in a direction intersecting the moving direction of the movable electrode portion 12, and has a central portion that receives the force of the central band portion 121 of the movable electrode portion 12, and one end and the other end fixed to the fixed portion body 151, and has thin-walled portions between the central portion and the one end and between the central portion and the other end, respectively, with a wall thickness thinner than that of the central portion, the one end, and the other end. When an external force acts on the central portion, the stress generated on the side surface of the elastic portion 152 having a rectangular beam structure between the central portion and the one end and between the central portion and the other end is smaller than the stress generated on the side surface of the central portion, the one end, and the other end. In the present embodiment, a structure is provided in which the thin-walled portions are provided between the central portion and the one end and between the central portion and the other end, where the stress is small. As a result, the stress on the side surface of the thin-walled portion of the elastic portion 152 increases, and the stress on the entire side surface of the elastic portion 152 becomes uniform. Therefore, the elastic portion can be miniaturized and the spring constant can be increased, and the elastic energy accompanying the deformation can be increased. As a result, damage to the elastic portion 152 when subjected to a large external force can be suppressed.

[0196] (2) The elastic portion 152 is formed into a gently curved surface between the central portion and the thin portion so that the stress therebetween becomes substantially uniform. By making the stress generated between the central portion and the thin portion uniform, the elastic portion can be miniaturized.

[0197] It is possible to suppress damage between the central portion and the thin-walled portion of the elastic portion 152 .

[0198] (3) The side surface of the central portion of the elastic portion 152 facing the central band portion 121 of the movable electrode portion 12 protrudes further toward the central band portion 121 of the movable electrode portion 12 than the thin-walled portion. Therefore, when the central band portion 121 of the movable electrode portion 12 abuts against the elastic portion 152, it is possible to suppress the generation of an undesirable rotational moment in the central band portion 121, and the movable electrode portion 12 can be effectively moved linearly. As a result, it is possible to suppress a decrease in power generation efficiency.

[0199] (4) The elastic part 152 is formed of a parabolic beam, which has: the second and third beam components 152b and 152c having two parabolic profiles integrated on the base side; the first beam component 152a having a parabolic profile connected to the vertex side of the second beam component 152b; and the fourth beam component 152d having a parabolic profile connected to the vertex side of the third beam component 152c. Thus, compared with the case where the elastic part 152 is formed of a rectangular beam, as long as the elastic part is miniaturized or the parabolic beam and the rectangular beam are made the same size, the maximum deflection amount can be increased or the spring constant can be increased, and the elastic energy that the elastic part 152 can retain can be increased.

[0200] When the elastic portion 152 is formed of the above-described parabolic beam, it is preferable that the thickness w(y) of the elastic portion 152 be set so as to substantially satisfy the following formula.

[0201]

[0202] Wherein, w(y) is the thickness of the parabolic beam at the position y from the center of the beam length of the elastic portion 152, and w 0 is the thickness of one end of the elastic portion 152 , |y| is the absolute value of the length from the center of the beam length of the elastic portion 152 to the position y, and L is the total length of the beam length of the elastic portion 152 .

[0203] (5) The MEMS element 10 includes the susceptor 7 , the movable electrode portion 12 , and the fixed portion 150 including the elastic portion 152 and the fixed portion main body 151 . The fixed portion 150 includes the slit 153 extending along the elastic portion 152 and penetrating the fixed portion main body 151 . The elastic portion 152 extends in a direction intersecting the moving direction of the central band portion 121 of the movable electrode portion 12, and includes a central portion that receives the force of the central band portion 121, and one end and the other end fixed to the fixed portion main body 151. The slit 153 includes a first slit portion 153a provided corresponding to the central portion of the elastic portion 152, and a second slit portion 153b connected to the first slit portion 153a and provided on the inner side near one end and the other end of the elastic portion 152. The width of the second slit portion 153b in the moving direction of the central band portion 121 is formed to be larger than the width of the first slit portion 153a in the moving direction of the central band portion 121. The corner portion 171 on one end side and the corner portion 171 on the other end side of the elastic portion 152 of the second slit portion 153b are respectively provided with arc-shaped curved portions, and the curvature radius Rb of the arc-shaped curved portion is larger than the curvature radius Ra of the circle inscribed in the first slit portion 153a. Therefore, concentrated stress generated in the corner 171 on one end side and the corner 171 on the other end side of the elastic portion 152 can be suppressed, and even when the elastic portion 152 is subjected to large vibration, damage can be suppressed.

[0204] In the above embodiment, the MEMS element 10 is formed of an SOI substrate and exemplified, but a silicon substrate may be used. In addition, glass, metal, alumina, etc. may be used instead of the silicon substrate.

[0205] In addition, in the above embodiment, the MEMS element 10 is illustrated as a vibration power generation element. However, it can also be used as a MEMS element for a vibration actuator that applies a driving voltage from the outside to vibrate the movable electrode portion. In the vibration actuator, the vibration of the movable electrode portion can be used to form various devices. In addition, the MEMS element 10 of this embodiment can also be used as various sensors.

[0206] Various embodiments and modifications are described in the above description, but the present invention is not limited to these contents. The above various embodiments and modifications can also be combined, or appropriately changed, and other schemes considered within the scope of the technical concept of the present invention are also included in the scope of the present invention.

[0207] The disclosures of the following priority basic applications are incorporated herein by reference.

[0208] Japan Special Application No. 2019-187153 (applied on October 10, 2019)

[0209] Explanation of symbols

[0210] 1—vibration power generating device, 7—base, 10—MEMS element, 11—fixed electrode portion, 12—movable electrode portion (movable portion), 13—elastic support portion, 110—fixed comb teeth, 120—movable comb teeth, 121—central belt portion, 121a—side surface, 128—protrusion, 150—fixed portion, 151—fixed portion body, 152—elastic portion, 152a to 152d—beam forming portion, 153—slit, 153a—first slit portion, 153b—second slit portion, 153c—slit portion, 153d—slit portion, 153e—first slit portion, 153f—second slit portion, 153f— ... 4—beam-constituting-part connecting part, 155—slit, 155a—first slit part, 155b—second slit part, 161—side surface, 163—inner side surface, 171—corner, 251—elastic part, 252—parabolic beam, 252a—first beam-constituting part, 252b—second beam-constituting part, 252c—third beam-constituting part, 252d—fourth beam-constituting part, 254—beam-constituting-part connecting part, 261—elastic part, 262a~262d—beam-constituting part, 264—beam-constituting-part connecting part.

Claims

1. A MEMS element, characterized in that: have: Pedestal; a movable portion, at least a portion of which is fixed to the base and is movable in a predetermined direction; and a fixed part, at least a part of which is fixed to the base, and comprises an elastic part disposed opposite to the movable part and a fixed part main body to which the elastic part is fixed, The elastic part extends in a direction intersecting the moving direction of the movable part, and has a central part that receives the force of the movable part, and one end and the other end that are fixed to the main body of the fixed part, and has a thin-walled part between the central part and the one end, and between the central part and the other end, which is thinner than the central part, the one end, and the other end, respectively. The elastic portion has a gently curved surface formed between the central portion and the thin-walled portion so that stress therebetween becomes uniform.

2. The MEMS element according to claim 1, characterized in that: A side surface of the central portion of the elastic portion that faces the movable portion protrudes further toward the movable portion than the thin-walled portion.

3. The MEMS element according to claim 1, characterized in that: A protrusion that faces the central portion of the fixed portion is formed on a side surface of the movable portion that faces the fixed portion.

4. The MEMS element according to claim 1, characterized in that: A slit is provided between the elastic portion and the fixing portion body, the slit extending along the elastic portion and penetrating the fixing portion body. The side surface of the elastic portion facing the movable portion is formed as a gently curved surface in which stress generated by a force received from the movable portion becomes uniform on a surface of the central portion and a surface of the thin-walled portion.

5. The MEMS element according to claim 1, characterized in that: The elastic part has four beam components. A slit extending along the elastic portion is provided between the elastic portion and the fixing portion body. At least one of the side surface of the elastic portion facing the movable portion and the side surface of the elastic portion on the slit side has a parabolic structure, and the parabolic structure includes: a first beam-forming portion having a parabolic curved surface whose base is fixed to one end of the fixed portion body; a second beam-forming portion having a parabolic curved surface connected to the first beam-forming portion at the vertex side; a third beam-forming portion having a parabolic curved surface integrated with the second beam-forming portion at the base; and a fourth beam-forming portion having a parabolic curved surface connected to the third beam-forming portion at the vertex side and whose base is fixed to the other end of the fixed portion body.

6. The MEMS element according to claim 5, characterized in that: The side surface of the elastic portion facing the movable portion has a shape formed by joining a parabolic curved surface having a center of the central portion as a base end and a parabolic curved surface having the one end as a base end at the vertex side of each parabolic curved surface between the central portion and the one end. The side surface of the elastic portion on the slit side is formed in a linear shape.

7. The MEMS element according to claim 5, characterized in that: The thickness w(y) of the elastic portion is set to satisfy the following formula: Wherein: w(y) is the thickness of the parabolic beam of the elastic part at the position y from the center of the beam length, w0 is the thickness of one end of the elastic part, |y| is the absolute value of the length of the elastic part from the center of the beam length to the position y, and L is the total length of the beam length of the elastic part.

8. The MEMS element according to claim 1, characterized in that: A slit extending along the elastic portion is provided between the elastic portion and the fixing portion body. The slit includes: a first slit portion provided corresponding to the central portion of the elastic portion; and a second slit portion connected to the first slit portion and provided inside the vicinity of the one end and the vicinity of the other end of the elastic portion. The width of the second slit portion in the moving direction of the movable portion is larger than the width of the first slit portion.

9. The MEMS element according to claim 8, characterized in that: A stopper is provided in a region of the fixing portion body that is opposite to the first slit portion. The front end surface of the stopper portion is a final limiting front end surface that finally limits the force of the movable portion received via the elastic portion.

10. The MEMS element according to claim 1, characterized in that: The base, the fixed portion, and the movable portion are formed of silicon.

11. A MEMS element, characterized in that: have: Pedestal; a movable portion, at least a portion of which is fixed to the base and is movable in a predetermined direction; and a fixed part, at least a part of which is fixed to the base, and comprises an elastic part disposed opposite to the movable part and a fixed part main body to which the elastic part is fixed, The fixing portion has a slit between the elastic portion and the fixing portion body extending along the elastic portion and penetrating the fixing portion body. The elastic part extends in a direction intersecting the moving direction of the movable part, and has a central part receiving the force of the movable part and a beam structure fixed to one end and the other end of the fixed part body. A thin-walled portion having a thickness thinner than that of the central portion, the one end, and the other end is provided between the central portion and the one end, and between the central portion and the other end, respectively. The central portion of the elastic portion and the thin-walled portion are formed into a gently curved surface so that stress therebetween becomes uniform. The slit includes: a first slit portion provided corresponding to the central portion of the elastic portion; and a second slit portion connected to the first slit portion and provided inside the vicinity of the one end and the vicinity of the other end of the elastic portion. The width of the movable part of the second slit part in the moving direction is formed to be larger than the width of the first slit part, and an arc-shaped curved part is provided at the corner of the one end side and the corner of the other end side of the elastic part of the second slit part, and the curvature radius of the arc-shaped curved part is larger than the curvature radius of the circle inscribed in the first slit part.

12. The MEMS element according to claim 11, characterized in that: The base, the fixed portion, and the movable portion are formed of silicon.

13. The MEMS element according to claim 12, characterized in that: The movable portion includes a plurality of movable comb teeth and a comb tooth connecting portion connecting the plurality of movable comb teeth, and the fixed portion includes a plurality of fixed comb teeth that are inserted into and removed from the plurality of movable comb teeth of the movable portion.

14. The MEMS element according to claim 13, characterized in that: An electret is formed on at least one of the movable comb teeth and the fixed comb teeth.

15. A vibration power generation device, characterized in that: have: The MEMS element as claimed in any one of claims 1 to 14; an elastic supporting portion that elastically supports the movable portion of the MEMS element on the fixed portion; and An output unit outputs electric power generated by the vibration of the movable unit relative to the fixed unit.

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