MEMS device and electro-acoustic conversion device

Abstract

The invention provides an MEMS device, which increases the displacement of a movable part, reduces the stress of the MEMS device, enables the MEMS device to be miniaturized, and improves the resonance frequency. The MEMS device is provided with a frame-shaped fixed part, a movable part arranged on the inner side of the fixed part in plan view, four torsion beams for supporting the movable part, driving beams which are respectively arranged relative to the torsion beams, one ends of the driving beams are connected with the torsion beams, and the other ends of the driving beams are connected with the inner edge of the fixed part, and driving sources arranged on the driving beams. Each of the drive beams is arranged to be point-symmetric with respect to the center of the movable part in plan view, and each of the drive beams has a region in which the width in a direction parallel to a first side connected to the inner edge gradually increases toward the first side in plan view. The movable part is provided with extension parts extending radially from the center in plan view, the number of the extension parts is the same as the number of the torsion beams, each extension part comprises an upper surface, a lower surface, one end surface and two side surfaces connected with the end surface, and each torsion beam is connected with two adjacent side surfaces included in different extension parts.

Description

Technical Field

[0001] The present disclosure relates to a MEMS device and an electroacoustic transducer. Background Art

[0002] MEMS devices, manufactured using microfabrication technology within microelectromechanical systems (MEMS), have been developed. Because MEMS devices are manufactured using semiconductor processes, they offer numerous advantages, including minimal deviation, small size, thinness, light weight, low power consumption, and excellent frequency characteristics. MEMS devices have a fixed portion and a movable portion. By driving the movable portion, they can be used in electroacoustic transducers such as headphones and microphones (see, for example, Patent Document 1). Increasing the displacement of the movable portion of the MEMS device can increase sound pressure when used in electroacoustic transducers. Driving the movable portion generates stress in the MEMS device. Furthermore, miniaturization of MEMS devices is required in electroacoustic transducers. Furthermore, increasing the resonant frequency of the MEMS device can improve acoustic characteristics when used in electroacoustic transducers.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: U.S. Patent Specification No. 9980051 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] The present disclosure aims to increase the displacement of a movable portion in a MEMS device. Furthermore, the present disclosure aims to reduce stress in the MEMS device. Furthermore, the present disclosure aims to miniaturize the MEMS device. Furthermore, the present disclosure aims to increase the resonant frequency in the MEMS device.

[0008] Solutions to Problems

[0009] A MEMS device according to one embodiment of the present disclosure comprises: a frame-shaped fixed portion; a movable portion arranged on the inner side of the fixed portion when viewed in a plane; four torsion beams supporting the movable portion; a driving beam provided for each of the torsion beams, one end of the driving beam being connected to the torsion beam and the other end being connected to the inner edge of the fixed portion; and a driving source arranged at each of the driving beams, wherein each of the driving beams is symmetrically arranged with respect to the center point of the movable portion when viewed in a plane, and each of the driving beams has a region in which the width in a direction parallel to the first side connected to the inner edge gradually widens toward the first side when viewed in a plane.

[0010] Furthermore, a MEMS device according to an embodiment of the present disclosure comprises: a frame-shaped fixed portion; a movable portion arranged on the inner side of the fixed portion when viewed in a planar manner; a plurality of torsion beams supporting the movable portion; a driving beam provided for each of the torsion beams, one end of which is connected to the torsion beam and the other end of which is connected to the inner side surface of the fixed portion; and a driving source arranged at each of the driving beams, the movable portion having an extension portion extending radially from the center when viewed in a planar manner, the number of which is the same as the number of the torsion beams, each of the extension portions including an upper surface, a lower surface, an end surface and two side surfaces connected to the end surface, and each of the torsion beams being connected to both sides of the adjacent side surfaces included in different of the extension portions.

[0011] Furthermore, a MEMS device according to one embodiment of the present disclosure includes: a frame-shaped fixed portion; a movable portion arranged inside the above-mentioned fixed portion when viewed in plan; a torsion beam and a drive beam connecting the above-mentioned fixed portion and the above-mentioned movable portion at a position closer to the lower surface than the respective upper surfaces; a drive source arranged on the lower surface of the above-mentioned drive beam; a pair of conduction pads arranged on the lower surface of the above-mentioned fixed portion; a first wiring electrically connecting one side of the pair of conduction pads to one side of the electrodes of each of the above-mentioned drive sources; and a second wiring electrically connecting the other side of the pair of conduction pads to the other side of the electrodes of each of the above-mentioned drive beams, the first wiring including a ring-shaped wiring and a branch wiring branching from the above-mentioned ring-shaped wiring and connected to each of the above-mentioned drive sources, the ring-shaped wiring extending from one side of the above-mentioned conduction pad and arranged in a ring shape so as to surround a plurality of the above-mentioned drive sources when viewed in plan, and returning to one side of the above-mentioned conduction pad, and the second wiring being arranged inward of the above-mentioned ring-shaped wiring when viewed in plan.

[0012] Furthermore, a MEMS device according to one embodiment of the present disclosure includes: a frame-shaped fixed portion; a movable portion arranged on the inner side of the fixed portion when viewed in a planar manner; four torsion beams supporting the movable portion; a driving beam provided for each of the torsion beams, one end of the driving beam being connected to the torsion beam and the other end being connected to the inner side surface of the fixed portion; and a driving source arranged on each of the driving beams, wherein the movable portion is in a cross shape.

[0013] The effects of the invention are as follows.

[0014] According to the present disclosure, the displacement of the movable portion of a MEMS device can be increased. Furthermore, according to the present disclosure, the stress of the MEMS device can be reduced. Furthermore, according to the present disclosure, the MEMS device can be miniaturized. Furthermore, according to the present disclosure, the resonant frequency of the MEMS device can be increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a top perspective view illustrating the MEMS device according to the first embodiment.

[0016] Figure 2 This is a bottom side perspective view illustrating the MEMS device according to the first embodiment.

[0017] Figure 3 This is a plan view illustrating the MEMS device according to the first embodiment.

[0018] Figure 4 It is a bottom view illustrating the MEMS device according to the first embodiment.

[0019] Figure 5 This is a cross-sectional view illustrating the MEMS device according to the first embodiment.

[0020] Figure 6 This is a diagram (part 1) explaining the reduction of stress in the MEMS device 20 .

[0021] Figure 7 It shows Figure 6 Figure 2 shows the effect of the construction shown.

[0022] Figure 8 This is a diagram (part 2) explaining the reduction of stress in the MEMS device 20 .

[0023] Figure 9 This is a diagram (part 3) explaining the reduction of stress in the MEMS device 20 .

[0024] Figure 10 This is a fourth diagram illustrating the reduction in stress of the MEMS device 20 .

[0025] Figure 11 is a simulation result of the resonance frequency of the MEMS device 20 .

[0026] Figure 12 This is a perspective view of the upper surface side showing an example of the electroacoustic transducer according to the first embodiment.

[0027] Figure 13 This is a bottom perspective view illustrating the electroacoustic transducer according to the first embodiment.

[0028] Figure 14 1 is a cross-sectional view illustrating the electroacoustic transducer according to the first embodiment.

[0029] Figure 15 It is an exploded perspective view of the upper surface side showing an example of the electroacoustic transducer according to the first embodiment.

[0030] Figure 16 It is an exploded perspective view from the bottom side showing an example of the electroacoustic transducer according to the first embodiment.

[0031] Figure 17This is a diagram (part 1) illustrating a method for manufacturing the electroacoustic transducer according to the first embodiment.

[0032] Figure 18 This is a diagram (part 2) illustrating the method for manufacturing the electroacoustic transducer according to the first embodiment.

[0033] Figure 19 This is a plan view illustrating a MEMS device according to the second embodiment.

[0034] Figure 20 2 is a diagram showing a comparison result between the MEMS device 20A and the MEMS device 20 .

[0035] Figure 21 It is an exploded perspective view of the upper surface side showing an example of the electroacoustic transducer according to the third embodiment.

[0036] Figure 22 This is the simulation result of the resonant frequency of the MEMS device and diaphragm.

[0037] Figure 23 These are the simulation results of the resonant frequencies when the thicknesses of the torsion beam and the drive beam are changed.

[0038] Figure 24 It is an exploded perspective view of the upper surface side showing an example of an electroacoustic transducer according to a fourth embodiment.

[0039] Figure 25 This is a plan view illustrating an example of a substrate constituting the electroacoustic transducer according to the fourth embodiment.

[0040] Figure 26 It is a plan view showing the process of arranging a MEMS device on a substrate.

[0041] Figure 27 It is a cross-sectional view showing the process of arranging a MEMS device on a substrate.

[0042] Figure 28 This is a plan view illustrating a substrate constituting the electroacoustic transducer according to Modification 1 of the fourth embodiment.

[0043] Figure 29 This is a plan view illustrating a substrate constituting an electroacoustic transducer according to a second modification of the fourth embodiment.

[0044] Figure 30 This is a plan view illustrating a substrate constituting an electroacoustic transducer according to a third modification of the fourth embodiment.

[0045] Figure 31 This is a plan view showing the state after the MEMS device is aligned on the substrate.

[0046] Figure 32It is a bottom view illustrating wiring of the MEMS device according to the fifth embodiment.

[0047] Figure 33 These are simulation results of stress distribution when the movable part of a MEMS device is moved.

[0048] Figure 34 This is a bottom view illustrating wiring of a MEMS device according to Modification 1 of the fifth embodiment.

[0049] Figure 35 This is a bottom view illustrating a metal film of the MEMS device according to the sixth embodiment.

[0050] Figure 36 1C is a bottom view of an electroacoustic transducer 1C using a MEMS device 20C.

[0051] Figure 37 This is the process for measuring the displacement of the movable part.

[0052] Figure 38 This is a bottom view illustrating a metal film of a MEMS device according to Modification 1 of the sixth embodiment.

[0053] Figure 39 This is a bottom view illustrating a metal film of a MEMS device according to a second modification of the sixth embodiment.

[0054] Figure 40 1 is a cross-sectional view illustrating an electroacoustic transducer according to a seventh embodiment.

[0055] Figure 41 30D is a plan view showing an example of the diaphragm 30D.

[0056] Figure 42 This is a partial cross-sectional view illustrating an electroacoustic transducer according to Modification 1 of the seventh embodiment.

[0057] Figure 43 This is a partial cross-sectional view illustrating an electroacoustic transducer according to Modification 2 of the seventh embodiment.

[0058] Explanation of symbols

[0059] 1, 1A, 1B, 1C—Electroacoustic converter, 10—Substrate, 101—First side, 102—Second side, 103—Third side, 104—Fourth side, 10a—Upper surface, 10b—Lower surface, 10x—Cavity, 10y—Through hole, 11a, 11b—Internal connection pads, 12a, 12b—External connection pads, 13a, 13b—Through wiring, 14, 14a, 14b—Height alignment pads , 15—first alignment pad, 16—second alignment pad, 17a—positive electrode mark, 17b—negative electrode mark, 18—alignment mark, 20, 20A, 20B, 20C, 20D, 20E, 20F—MEMS device, 21—fixed part, 21a—inner side, 22—movable part, 23—torsion beam, 24—drive beam, 24a—first side, 24b—second side, 241—first area, 242—second area , 243—third area, 244—fourth area, 25—driving source, 26—convex part, 26a—side, 27—concave part, 27a—inner side, 28a, 28b—conductive pad, 30, 30A, 30D—diaphragm, 31—frame part, 32, 32A—central part, 33—connecting part, 34—slit, 35, 35M, 35N—concave-convex structure, 35a—first convex part, 35b—first concave part, 36a—second Protrusion, 36b—second recess, 40—vibration plate, 41—first wiring, 41a—ring wiring, 41b—branch wiring, 42—second wiring, 42a—part, 43, 43a, 43b—metal film, 50—cover part, 51—thick plate part, 50x—cavity part, 50y—opening part, 60—adhesive layer, 70—mesh part, 200, 210—adhesive layer, 310—conductive bonding material, 400—adsorption fixture. DETAILED DESCRIPTION

[0060] Hereinafter, the embodiment of the invention will be described with reference to the accompanying drawings. In each of the drawings, the same components are sometimes denoted by the same reference numerals, and repeated descriptions are omitted.

[0061] <First embodiment>

[0062] (MEMS devices)

[0063] Figure 1 This is a top perspective view illustrating the MEMS device according to the first embodiment. Figure 2 This is a bottom side perspective view illustrating the MEMS device according to the first embodiment. Figure 3 This is a plan view illustrating the MEMS device according to the first embodiment. Figure 4 It is a bottom view illustrating the MEMS device according to the first embodiment. Figure 5 is a cross-sectional view illustrating a MEMS device according to the first embodiment, showing a Figure 1The cross section of line AA.

[0064] In addition, for reference, in each of the drawings, orthogonal coordinates having an X-axis, a Y-axis, and a Z-axis are sometimes shown. In each of the X-, Y-, and Z-directions, the side pointed by the arrow is sometimes referred to as the "+ side," and the opposite side is sometimes referred to as the "- side." Furthermore, the surface on the Z+ side of each component is sometimes referred to as the upper surface, and the surface on the Z- side is sometimes referred to as the lower surface. However, the above directions do not limit the orientation of the MEMS device, etc., of the embodiment when in use; the orientation of the MEMS device, etc., of the embodiment is arbitrary. Furthermore, the situation of observing an object from the Z+ side to the Z- side, or vice versa, is sometimes referred to as a plan view.

[0065] When referring to Figures 1 to 5 , the MEMS device 20 includes a fixed portion 21, a movable portion 22, a plurality of torsion beams 23, a plurality of drive beams 24, and a plurality of drive sources 25. The number of torsion beams 23, drive beams 24, and drive sources 25 is the same. Figure 2 and Figure 4 In FIG. 2 , for convenience of explanation, the driving source 25 is shown as a dot pattern. In the following drawings, the same display may be used.

[0066] The fixing portion 21 is formed into a frame shape when viewed from above. The fixing portion 21 has an outer edge and an inner edge when viewed from above. The inner edge and the outer edge may be similar in shape or not. For example, the inner edge may be polygonal and the outer edge may be circular or elliptical. Figures 1 to 5 In the example of , the inner edge of the fixing portion 21 is square, and the outer edge is square or rectangular. When the outer edge is square or rectangular, it can be easily processed by cutting with a blade, so it is preferred in terms of reducing processing costs.

[0067] The length of one side of the outer edge of the fixing portion 21 can be, for example, approximately 3 mm to 10 mm. The width of the fixing portion 21 (the distance from the inner edge to the outer edge) can be, for example, approximately 0.3 mm to 1.0 mm. The thickness of the fixing portion 21 can be, for example, approximately 100 μm to 500 μm.

[0068] In the present application, polygons such as quadrilaterals include polygons in which corners are rounded or chamfered, or in which protrusions or grooves are partially provided.

[0069] The movable portion 22 is positioned inside the fixed portion 21 when viewed in plan and is supported so as to be freely movable relative to the fixed portion 21. When viewed in plan, the center O of the movable portion 22 is preferably aligned with the center of the inner edge of the fixed portion 21. The movable portion 22 is preferably point-symmetrical with respect to the center O of the movable portion 22 when viewed in plan. The thickness of the movable portion 22 is the same as that of the fixed portion 21. The upper surface of the movable portion 22 and the upper surface of the fixed portion 21 are coplanar. The lower surface of the movable portion 22 and the lower surface of the fixed portion 21 are coplanar.

[0070] Alternatively, the upper and lower surfaces of the movable portion 22 and the upper and lower surfaces of the fixed portion 21 may be arranged to be non-coplanar. For example, by intentionally changing the film formation and polarization conditions of the drive source 25, the drive beam 24 can be warped, causing the height of the movable portion 22 to deviate toward the upper surface of the fixed portion 21. The distance between the upper surface of the fixed portion 21 and the upper surface of the movable portion 22 can be, for example, approximately 20 to 100 μm. Furthermore, the distance between the lower surface of the fixed portion 21 and the lower surface of the movable portion 22 can be, for example, approximately 20 to 100 μm.

[0071] In the present application, the same plane means that the height difference between the two is 20 μm or less.

[0072] The movable portion 22 has extension portions extending radially from the center in a planar view, the number of which is the same as the number of the torsion beams 23. Each extension portion includes an upper surface, a lower surface, an end surface, and two side surfaces connected to the end surface. Figures 1 to 5 In the example of FIG, the movable portion 22 has a cross shape including four extending portions radially extending from the center in a plan view.

[0073] Furthermore, when the movable portion 22 is cross-shaped, with respect to surfaces other than the upper and lower surfaces, the two pairs of surfaces that face each other in the longitudinal direction are referred to as end surfaces, and the remaining surfaces are referred to as side surfaces. In other words, when the movable portion 22 is cross-shaped, the movable portion 22 has four end surfaces of equal area and eight side surfaces of equal area. The eight side surfaces consist of four pairs of adjacent side surfaces. Furthermore, fillets and chamfers between end and side surfaces, and between side surfaces, are not included in the end and side surfaces.

[0074] The torsion beam 23 and the driving beam 24 connect the fixed part 21 and the movable part 22 at a position closer to the lower surface than the upper surface of each. The plurality of torsion beams 23 support the movable part 22 from the outside. The torsion beam 23 is elastically deformable. The torsion beam 23 is thinner than the movable part 22. The thickness of the torsion beam 23 can be, for example, about 5 μm to 60 μm. The torsion beam 23 is connected to the end of the lower surface side of the side of the movable part 22. Figures 1 to 5In the example of FIG, four torsion beams 23 are provided. It is preferable that the torsion beams 23 are arranged so as to be point-symmetrical with respect to the center O of the movable portion 22 in a plan view.

[0075] The upper surface of the torsion beam 23 is located lower than the upper surfaces of the fixed portion 21 and the movable portion 22. The lower surface of the torsion beam 23 is located on the same plane as the lower surfaces of the fixed portion 21 and the movable portion 22. When viewed in plan, each torsion beam 23 includes, for example, an L-shaped region. When the torsion beam 23 includes an L-shaped region, the length of the torsion beam 23 can be increased. This makes it easier for the torsion beam 23 to twist, thereby increasing the displacement of the movable portion 22. As a result, when the MEMS device 20 is used in an electroacoustic transducer, high sound pressure can be achieved.

[0076] When the movable portion 22 is shaped like a cross when viewed in plan, the length of the torsion beam 23 can be increased compared to when the movable portion 22 is shaped like a square with sides of the same length as the longitudinal direction of the cross. This increases the displacement of the movable portion 22. As a result, when the MEMS device 20 is used in an electroacoustic transducer, high sound pressure can be achieved. Furthermore, when the movable portion 22 is shaped like a cross when viewed in plan, compared to when the movable portion 22 is shaped like a square with sides of the same length as the longitudinal direction of the cross, the weight can be reduced, thereby increasing the resonant frequency.

[0077] A plurality of driving beams 24 are provided for each twist beam 23. Figures 1 to 5 In the example shown, four torsion beams 23 are provided, and therefore four drive beams 24 are also provided. One end of the drive beam 24 is connected to the torsion beam 23, and the other end is connected to the inner edge of the fixed portion 21. Specifically, the drive beam 24 is connected to the lower end of the inner side surface of the fixed portion 21. Each drive beam 24 is connected to only one of the four sides that constitute the inner edge of the fixed portion 21 when viewed in plan. Furthermore, the number of torsion beams 23 and drive beams 24 may be other than four.

[0078] The drive beam 24 is elastically deformable. The thickness of the drive beam 24 is the same as that of the torsion beam 23. The upper surface of the drive beam 24 is located lower than the upper surfaces of the fixed portion 21 and the movable portion 22. The lower surface of the drive beam 24 is located on the same plane as the lower surfaces of the fixed portion 21 and the movable portion 22. Furthermore, the upper surface of the drive beam 24 and the upper surface of the torsion beam 23 are located on the same plane. The lower surface of the drive beam 24 and the lower surface of the torsion beam 23 are located on the same plane. The drive beams 24 are preferably arranged so as to be point-symmetrical with respect to the center O of the movable portion 22 when viewed in plan.

[0079] The drive source 25 is disposed on the lower surface of each drive beam 24. To increase driving force, the drive source 25 is preferably disposed substantially entirely on the lower surface of each drive beam 24. The drive source 25 includes, for example, a piezoelectric film made of a piezoelectric material that converts applied electrical energy into mechanical energy. The drive source 25 vibrates in response to input of an AC signal.

[0080] The driving source 25 can be configured, for example, to include a lower electrode disposed on the lower surface of the driving beam 24, a piezoelectric film stacked on the lower electrode, and an upper electrode stacked on the piezoelectric film. The upper and lower electrodes can be made of, for example, gold (Au), platinum (Pt), or the like. The upper and lower electrodes can also be constructed by stacking multiple films.

[0081] The piezoelectric film can be made of, for example, PZT (lead zirconate titanate), a piezoelectric material. Alternatively, the piezoelectric film can be made of PNZT (lead zirconate titanate niobate), PLZT (lead lanthanum zirconate titanate), PLT (lead lanthanum titanate), PMN (lead magnesium niobate), PMNN (lead manganese niobate), BaTiO3 (barium titanate), or the like.

[0082] The driving source 25 is not limited to a three-layer structure consisting of a lower electrode, a piezoelectric film, and an upper electrode. For example, the driving source 25 may have two or more layers of piezoelectric films and intermediate electrodes. In this case, the piezoelectric films and intermediate electrodes are alternately stacked on the lower electrode in the required number, and finally, the piezoelectric film and the upper electrode are sequentially stacked on the uppermost intermediate electrode. The intermediate electrode can be made of the same material as the upper and lower electrodes.

[0083] When driving source 25 comprises a piezoelectric film and an intermediate electrode, the intermediate electrode is grounded, and a driving signal is supplied to the lower and upper electrodes. When the driving signal is supplied to the lower and upper electrodes, driving source 25 displaces according to the voltage of the driving signal. Furthermore, even when the driving signal is supplied to the intermediate electrode and the lower and upper electrodes are connected to ground, driving can still be achieved. By having n layers of piezoelectric film, the driving voltage of driving source 25 can be reduced to 1 / nth of that in the case of a single layer of piezoelectric film.

[0084] The MEMS device 20 can be fabricated using, for example, a semiconductor process using an SOI (Silicon On Insulator) substrate. However, the MEMS device 20 is not limited thereto and may also be formed from a Si (silicon) substrate, a sapphire substrate, an alumina substrate, a spinel substrate, a quartz substrate, a crystal substrate, a glass substrate, or a ceramic substrate. Of these, SOI and Si substrates are preferred due to their ease of microfabrication.

[0085] An SOI substrate consists of a buried oxide (BOX) layer made of silicon oxide on a supporting layer made of single-crystalline silicon (Si), and an active layer made of single-crystalline silicon on top of the buried layer. When fabricating a MEMS device 20 using an SOI substrate, the fixed portion 21 and movable portion 22 can be formed, for example, from the supporting layer, the buried layer, and the active layer. Furthermore, the torsion beam 23 and drive beam 24 can be formed, for example, from the active layer. Because the active layer is relatively thin, the torsion beam 23 and drive beam 24 formed from the active layer have elastic properties.

[0086] like Figure 3 As shown, in a plan view, each driving beam 24 has a region whose width in a direction parallel to the first side 24a connected to the inner edge of the fixing portion 21 gradually widens toward the first side 24a. Figure 3 In the example shown in FIG. 2 , when viewed in plan, each driving beam 24 has the widest width in a direction parallel to the first side 24 a at the position of the first side 24 a.

[0087] And, in Figure 3 In the example of FIG. 2 , when viewed from above, the width of each driving beam 24 in a direction parallel to the first side 24a is narrowest at the position of the second side 24b connected to the torsion beam 23. Figure 3 In the example, the first side 24a is parallel to the second side 24b.

[0088] And, as Figure 3 As shown, in plan view, each driving beam 24 may include a trapezoidal first region 241 and a trapezoidal second region 242 having a smaller area than the first region 241. The first region 241 is located closer to the first side 24a, and the second region 242 is located farther from the first side 24a than the first region 241. Furthermore, in each of the trapezoids forming the first and second regions 241, when the side closer to the first side 24a is defined as the lower base and the side farther from the first side 24a is defined as the upper base, the length of the lower base of the trapezoid forming the second region 242 is less than or equal to the length of the upper base of the trapezoid forming the first region 241. In plan view, the first side 24a, the upper base of the trapezoid forming the first region 241, and the upper base of the trapezoid forming the second region 242 may be parallel.

[0089] exist Figure 3 In the example shown in FIG2 , one side of the trapezoid constituting the first region 241 and one side of the trapezoid constituting the second region 242 are perpendicular to the first side 24a when viewed in plan. Furthermore, the other side of the trapezoid constituting the first region 241 and the other side of the trapezoid constituting the second region 242 have different inclination directions relative to the first side 24a when viewed in plan.

[0090] That is, the other side of the trapezoid constituting the first region 241 is inclined so as to approach the first side 24a as the first side 24a moves away from the corner of the fixing portion 21. Furthermore, the other side of the trapezoid constituting the second region 242 is inclined so as to move away from the first side 24a as the first side 24a moves away from the corner of the fixing portion 21.

[0091] exist Figure 3 In the example of FIG, in a plan view, the upper base of the trapezoid constituting the second region 242 is connected to the torsion beam 23, but one waist or the other waist of the trapezoid constituting the second region 242 may be connected to the torsion beam 23. Figure 19 , which will be explained in detail below.

[0092] Furthermore, in plan view, a third region 243, such as a rectangle, may be provided between the first side 24a and the first region 241, and a fourth region 244, such as a trapezoid, may be provided between the first region 241 and the second region 242. Alternatively, the third region 243 may be omitted, and the lower base of the trapezoid constituting the first region 241 may coincide with the first side 24a. Furthermore, the fourth region 244 may be omitted, and the upper base of the trapezoid constituting the first region 241 may coincide with the lower base of the trapezoid constituting the second region 242.

[0093] Thus, in the MEMS device 20, each drive beam 24 has a region whose width, parallel to a first side 24a connected to the inner edge of the fixed portion 21, gradually widens toward the first side 24a when viewed in plan. This structure allows the portion of the drive beam 24 connected to the inner edge of the fixed portion 21 to have a relatively wide shape, thereby enabling the movable portion 22 to be moved with high torque and a large displacement. As a result, when the MEMS device 20 is used in an electroacoustic transducer, high sound pressure can be achieved. Specifically, for example, by configuring each drive beam 24 to include a trapezoidal first region 241 and a second region 242, as described above, the movable portion 22 can be moved with high torque and a large displacement.

[0094] Furthermore, in MEMS device 20, drive beam 24 is preferably formed from single-crystal silicon, with both the inner and outer edges of fixing portion 21 aligned parallel to the <100> orientation of the single-crystal silicon. This allows for even higher sound pressure when MEMS device 20 is used in an electroacoustic transducer. This will be described in detail below.

[0095] For example, when a substrate (wafer) made of single-crystal silicon is used to manufacture the MEMS device 20, the substrate's principal surface is set to the (100) plane. In this case, either the <110> orientation or the <100> orientation is predominant as the crystal orientation along the substrate's principal surface. However, multiple MEMS devices 20 are arranged on the substrate so that the outer and inner edges of the fixing portion 21 are parallel to the <100> orientation. As a result, in the individualized MEMS devices 20, the outer and inner edges of the fixing portion 21 are all parallel to the <100> orientation.

[0096] The Young's modulus of single-crystal silicon varies depending on its crystal orientation. Specifically, the Young's modulus of single-crystal silicon is approximately 160 GPa when the crystal orientation is <110>, and approximately 130 GPa when the crystal orientation is <100>. Therefore, in the MEMS device 20, when the outer and inner edges of the fixed portion 21 are all parallel to the <100> orientation, the drive beam 24 is more likely to bend than when the outer and inner edges of the fixed portion 21 are all parallel to the <110> orientation. As a result, the movable portion 22 can be moved with higher torque and greater displacement, so when the MEMS device 20 is used in an electroacoustic transducer, a higher sound pressure can be achieved.

[0097] Furthermore, when an SOI substrate is used in the manufacture of the MEMS device 20, the main surfaces of the support layer and the active layer composed of single-crystal silicon are oriented as (100) planes, and the outer and inner edges of the fixing portion 21 are all parallel to the <100> orientation. This can achieve the same effects as described above.

[0098] Furthermore, in the MEMS device 20, all driving beams 24 have the same shape and are arranged point-symmetrically with respect to the center of the movable portion 22 in plan view. This makes it less likely that the movable portion 22 will tilt when it is moved, thereby reducing the risk of unwanted resonance.

[0099] (Reduction of Stress in MEMS Device 20 )

[0100] Figure 6 1 is a diagram illustrating the reduction of stress in the MEMS device 20. Figure 6 The upper portion is a perspective view of the upper surface side of the MEMS device 20 , and the lower portion is an enlarged view of the inner side of the dotted line E1 in the upper portion.

[0101] exist Figure 6 In the example of FIG. 1 , the movable portion 22 includes extension portions 22a, 22b, 22c, and 22d that extend radially from the center in a plan view and form a cross shape that is symmetrical with respect to the center point of the movable portion 22. Figure 6As shown in FIG. 1 , each torsion beam 23 is preferably connected to both adjacent side surfaces included in different extension portions constituting the movable portion 22. Figure 6 In the example shown in FIG. 1 , each torsion beam 23 connects to the entirety of one side surface and a portion of the other side surface of the adjacent side surface in plan view. Furthermore, in each torsion beam 23, the corner of the portion E2 connecting to the other side surface of the adjacent side surface is arc-shaped in plan view.

[0102] In this manner, each torsion beam 23 is connected to both adjacent side surfaces, resulting in a structure in which the L-shaped tip of each torsion beam 23 is offset by L1 relative to one of the adjacent side surfaces of the movable portion 22. When the length of the side surface of the movable portion 22 is 400 μm, L1 is, for example, approximately 50 to 300 μm.

[0103] Figure 7 It shows Figure 6 Figure 2 shows the effect of the construction shown. Figure 7 In the case of no offset, each torsion beam 23 is connected to only one side of the adjacent side of the movable portion 22 and Figure 6 The case where L1 is zero is shown. The case where there is an offset is Figure 6 The structure shown in the figure is as follows. Figure 7 In the Results column, a contour plot shows the simulation results of the stress generated when the movable portion 22 is moved. The arrows in the Results column indicate the location of the maximum stress area and the maximum stress value. The Results graph is inverted vertically relative to the Structure graph. Specifically, the Results graph shows the stress near the boundary between the torsion beam 23 and the movable portion 22.

[0104] like Figure 7 As shown in FIG. 1 , when the movable portion 22 is moved, a large stress is generated near the boundary between the torsion beam 23 and the movable portion 22. However, by providing an offset at the portion where each torsion beam 23 connects to the movable portion 22, the starting point of the bending of the torsion beam 23 is offset from the side surface of the movable portion 22, which serves as the boundary between the torsion beam 23 and the movable portion 22. This reduces the maximum stress. As a result, the risk of damage to the torsion beam 23 is reduced.

[0105] Figure 8 2 is a diagram illustrating the reduction of stress in the MEMS device 20. Figure 8 The upper portion is a perspective view of the upper surface side of the MEMS device 20 , and the lower portion is an enlarged view of the inner side of the dotted line E3 of the upper portion.

[0106] like Figure 8 As shown, the MEMS device 20 has a protrusion 26 that protrudes from each side of the inner side surface 21a of the fixed portion 21 toward one side of the movable portion 22 in a plan view. The thickness of the protrusion 26 is the same as that of the fixed portion 21. The protrusion 26 has a substantially right triangle shape in a plan view, for example.

[0107] Each driving beam 24 is connected to the inner side surface 21a of the fixing portion 21 and the side surface 26a of the convex portion 26 continuous with the inner side surface 21a. In plan view, the corner of the portion E4 of each driving beam 24 connected to the side surface 26a of the convex portion 26 is arc-shaped.

[0108] In this way, each drive beam 24 is connected to the inner side surface 21a of the fixing portion 21 and the side surface 26a of the protrusion 26 that is continuous with the inner side surface 21a. This creates a structure in which one end of each drive beam 24 connected to the fixing portion 21 is offset by L2 relative to the inner side surface 21a of the fixing portion 21. If the length of the side surface 26a of the protrusion 26 is 200 μm, L2 can be approximately 50 to 150 μm, for example. This offset offsets the starting point of the drive beam 24's bending from the inner side surface 21a of the fixing portion 21, which serves as the boundary between the drive beam 24 and the fixing portion 21. This reduces the maximum stress generated at one end of the connection between the drive beam 24 and the fixing portion 21. Consequently, the risk of damage to the drive beam 24 is reduced.

[0109] Figure 9 3 is a diagram illustrating the reduction of stress in the MEMS device 20. Figure 9 The upper portion is a perspective view of the upper surface side of the MEMS device 20 , and the lower portion is an enlarged view of the inner side of the upper dotted line E5 .

[0110] like Figure 9 As shown, the MEMS device 20 has recesses 27 that extend from each side of the inner side surface 21a of the fixing portion 21 toward one side of the outer side surface in a plan view. Furthermore, each drive beam 24 is connected to the inner side surface 21a of the fixing portion 21 and to the inner side surface 27a of the recess 27 that is continuous with the inner side surface 21a. In each drive beam 24, the corner of the portion E6 connecting to the inner side surface 27a of the recess 27 is rounded in a plan view.

[0111] In this way, each drive beam 24 is connected to the inner side surface 21a of the fixing portion 21 and the inner side surface 27a of the recessed portion 27, which is continuous with the inner side surface 21a. This creates a structure in which the other end of each drive beam 24 connected to the fixing portion 21 is offset by L3 relative to the inner side surface 21a of the fixing portion 21. If the length of the inner side surface 27a of the recessed portion 27 is 400 μm, L3 can be approximately 50 to 300 μm, for example. This offset offsets the starting point of the drive beam 24's bending from the inner side surface 21a of the fixing portion 21, which serves as the boundary between the drive beam 24 and the fixing portion 21. This reduces the maximum stress generated at the other end of the connection between the drive beam 24 and the fixing portion 21. Consequently, the risk of damage to the drive beam 24 is reduced.

[0112] Figure 104 is a diagram illustrating the reduction of stress in the MEMS device 20. Figure 10 The upper portion is a perspective view of the lower surface side of the MEMS device 20 , and the lower portion is an enlarged view of the inner side of the dotted line E7 in the upper portion.

[0113] like Figure 10 As shown in FIG, in the MEMS device 20, the corner E8 of the driving source 25 is arc-shaped when viewed in plan. This can reduce the risk of damage to the driving source 25 due to electric field concentration.

[0114] (Size of the movable portion 22 of the MEMS device 20)

[0115] Figure 11 is a simulation result of the resonance frequency of the MEMS device 20 . Figure 11 In the example, the movable portion is large when the shape of the movable portion 22 is large, and the movable portion is small when the shape of the movable portion 22 is small. Figure 11 As shown, the resonant frequency can be adjusted by changing the size of the movable portion 22. Specifically, by miniaturizing the movable portion 22, the resonant frequency can be increased. Considering the Harman curve, the resonant frequency of the movable portion 22 is preferably between 1 kHz and 3 kHz, more preferably around 2 kHz. The Harman curve is a frequency characteristic of the sound pressure level and is used as an indicator when adjusting the characteristics of headphones and other devices.

[0116] (Electroacoustic conversion device)

[0117] Figure 12 This is a perspective view of the upper surface side showing an example of the electroacoustic transducer according to the first embodiment. Figure 13 This is a bottom perspective view illustrating the electroacoustic transducer according to the first embodiment. Figure 14 is a cross-sectional view illustrating an electroacoustic converter according to a first embodiment, Figure 12 The cross section of the BB line. Figure 15 It is an exploded perspective view of the upper surface side showing an example of the electroacoustic transducer according to the first embodiment. Figure 16 It is an exploded perspective view from the bottom side showing an example of the electroacoustic transducer according to the first embodiment.

[0118] When referring to Figures 12 to 16 , the electroacoustic transducer 1 includes a substrate 10, a MEMS device 20, a diaphragm 30, a vibration plate 40, a cover member 50, and a mesh member 70. The electroacoustic transducer 1 is an earphone or a set-type speaker.

[0119] The substrate 10 is a component that serves as the base of the electroacoustic converter 1. As the substrate 10, for example, a glass epoxy substrate can be used. As the substrate 10, a silicon substrate or a ceramic substrate can also be used. The thickness of the substrate 10 can be, for example, about 0.2 mm to 0.6 mm. The substrate 10 has a wiring layer formed of, for example, gold, copper, etc. The wiring layer can be provided on the upper surface 10a and / or the lower surface 10b of the substrate 10, or can be provided inside the substrate 10. That is, the substrate 10 can also be a multilayer wiring substrate. In addition, the wiring layer can include pads, through wiring, dummy wiring, etc.

[0120] A pair of internal connection pads 11a and 11b are arranged on the upper surface 10a of the substrate 10, forming a path for signals supplied to all driving sources 25. Furthermore, a pair of external connection pads 12a and 12b are arranged on the lower surface 10b of the substrate 10, for supplying signals from outside the electroacoustic transducer 1 to the electroacoustic transducer 1.

[0121] Internal connection pads 11a and external connection pads 12a are electrically connected via through-wiring 13a extending from upper surface 10a to lower surface 10b through substrate 10. Similarly, internal connection pads 11b and external connection pads 12b are electrically connected via through-wiring 13b extending from upper surface 10a to lower surface 10b through substrate 10.

[0122] Furthermore, a positive electrode mark 17a and a negative electrode mark 17b indicating the polarity of the external connection pads 12a and 12b are provided on the lower surface 10b of the substrate 10. The positive electrode mark 17a indicates that the external connection pad 12a is a "+" terminal, and the negative electrode mark 17b indicates that the external connection pad 12b is a "-" terminal.

[0123] Furthermore, a mesh 70 alignment mark 18 is disposed on the lower surface 10b of the substrate 10 so as to surround the through-hole 10y. For example, if the mesh 70 is circular, the alignment mark 18 can be annular. In this case, the inner diameter of the annular ring can be approximately the same as the diameter of the mesh 70, thereby enabling alignment of the mesh 70.

[0124] The positive electrode mark 17a, the negative electrode mark 17b, and the alignment mark 18 can be formed of, for example, the same metal material as the external connection pads 12a and 12b. The thickness of the positive electrode mark 17a, the negative electrode mark 17b, and the alignment mark 18 can be, for example, the same as that of the external connection pads 12a and 12b. Furthermore, the positive electrode mark 17a, the negative electrode mark 17b, and the alignment mark 18 do not need to be electrically disconnected (floating).

[0125] The external connection pads 12a and 12b, the positive electrode mark 17a, the negative electrode mark 17b, and the alignment mark 18 protrude from the lower surface 10b of the substrate 10. A resin film may be disposed on the lower surface 10b of the substrate 10 by printing or the like in areas where the external connection pads 12a and 12b, the positive electrode mark 17a, the negative electrode mark 17b, and the alignment mark 18 are not provided. Examples of the resin film include polyimide films.

[0126] By making the thickness of the resin film the same as that of the external connection pads 12a and 12b, the positive electrode mark 17a, the negative electrode mark 17b, and the alignment mark 18, the lower surface 10b of the substrate 10 can be flattened. This prevents the electroacoustic transducer 1 from tilting relative to the predetermined plane when the electroacoustic transducer 1 is disposed on a predetermined plane with the lower surface 10b of the substrate 10 as the lower side.

[0127] The pair of internal connection pads 11 a and 11 b of the substrate 10 are electrically connected to a pair of conduction pads 28 a and 28 b arranged on the lower surface of the fixed portion 21 of the MEMS device 20 via a conductive bonding material.

[0128] The substrate 10 has a frame-shaped upper surface 10a, a lower surface 10b, and a cavity portion 10x that is recessed from the upper surface 10a side to the lower surface 10b side. In the case of the MEMS device 20, when a driving voltage is applied, the movable portion 22 is displaced toward the substrate 10 side. At this time, if the cavity portion 10x is not provided on the substrate 10 and the upper surface of the substrate 10 is flat, there is a concern that the movable portion 22 may contact the substrate 10. Such a concern is eliminated by providing the cavity portion 10x on the substrate 10. The depth from the upper surface 10a of the substrate 10 to the bottom surface of the cavity portion 10x is determined in consideration of the maximum displacement of the movable portion 22, and can be, for example, approximately 0.1 mm to 0.4 mm.

[0129] The cavity 10x can be formed by joining a frame-shaped substrate to the outer periphery of a plate-shaped substrate, or by providing a hollow portion in the center of a plate-shaped substrate by machining. In other words, the substrate 10 can be formed by joining multiple substrates or by machining a single substrate.

[0130] Furthermore, a structure in which a through hole is provided in the substrate 10 instead of the cavity 10 x is also conceivable. However, the rigidity of the entire electroacoustic transducer 1 cannot be ensured. Therefore, a structure in which the cavity 10 x is provided in the substrate 10 is advantageous.

[0131] Furthermore, by providing the cavity portion 10 x in the substrate 10 , a back volume of the electroacoustic transducer 1 can be formed, thereby achieving an effect of reducing the sharpness at the resonance frequency.

[0132] Furthermore, substrate 10 is preferably provided with a through-hole 10y. For example, through-hole 10y can be provided in the center of cavity 10x when viewed in plan. Through-hole 10y serves as an air inlet and outlet path for the interior of substrate 10. Specifically, the provision of through-hole 10y allows air to enter and exit through through-hole 10y, thereby reducing air resistance during the movement of movable portion 22 of MEMS device 20. As a result, movable portion 22 can be easily moved, and the displacement of movable portion 22 can be increased.

[0133] The MEMS device 20 is arranged on the substrate 10 so that the driving source 25 faces the substrate 10 side. In the MEMS device 20, for example, the lower surface of the fixing portion 21 can be bonded to the upper surface 10a of the substrate 10 via an adhesive layer. The adhesive layer can be formed, for example, from a thermosetting adhesive. Examples of thermosetting adhesives include epoxy adhesives. The adhesive layer can also be formed from double-sided tape or a UV-curable adhesive.

[0134] The outer surface of the fixed portion 21 is exposed to the outside of the electroacoustic transducer 1. That is, in the electroacoustic transducer 1, no other components are arranged outside the outer surface of the fixed portion 21. In plan view, the movable portion 22, torsion beam 23, drive beam 24, and drive source 25 are located at a position overlapping the cavity 10x.

[0135] By directly bonding the lower surface of the fixing portion 21 of the MEMS device 20 to the upper surface 10a of the substrate 10, no other components such as a bonding frame are required, and no components are provided outside the outer surface of the fixing portion 21. Therefore, the electroacoustic transducer 1 can be miniaturized.

[0136] The diaphragm 30 is a flexible, film-like member disposed on the MEMS device 20. The diaphragm 30 is, for example, rectangular in plan view. However, this is not limiting. The diaphragm 30 may also have other shapes, such as a circle, an ellipse, a triangle, or a polygon with a pentagon or larger shape, in plan view.

[0137] Diaphragm 30 includes a frame portion 31, a central portion 32 located inward of the inner edge of frame portion 31, and a connecting portion 33 connecting the inner edge of frame portion 31 to the outer edge of central portion 32. In diaphragm 30, the upper surface of frame portion 31 and the upper surface of central portion 32 are, for example, coplanar, and the lower surface of frame portion 31 and the lower surface of central portion 32 are, for example, coplanar. Connecting portion 33 protrudes toward lid member 50 from the upper surfaces of frame portion 31 and central portion 32. In a cross-sectional view taken perpendicular to the upper surface of central portion 32, the upper and lower surfaces of connecting portion 33 are curved in the same direction.

[0138] Alternatively, the upper and lower surfaces of the frame portion 31 may be arranged to be non-coplanar with the upper and lower surfaces of the central portion 32. For example, the height of the central portion 32 may be offset relative to the frame portion 31 by intentionally changing the molding conditions of the diaphragm 30. The distance between the upper surface of the frame portion 31 and the upper surface of the central portion 32 may be, for example, approximately 20 to 100 μm. Furthermore, the distance between the lower surface of the frame portion 31 and the lower surface of the central portion 32 may be, for example, approximately 20 to 100 μm.

[0139] The connecting portion 33 has a plurality of slits 34 arranged at predetermined intervals in a direction extending annularly and substantially perpendicular thereto. With this structure, when the diaphragm 30 vibrates, it is difficult to suppress the displacement of the central portion 32 caused by the displacement of the movable portion 22 using the tension from the frame portion 31 fixed to the fixed portion 21.

[0140] The thickness of the diaphragm 30 can be, for example, approximately 5 to 50 μm. The diaphragm 30 can be made of, for example, an elastomer or a resin. Examples of elastomers include TPEE (polyester elastomer) and TPU (polyurethane elastomer). Examples of resins include PET (polyethylene terephthalate), PI (polyimide), and PEEK (polyetheretherketone). The diaphragm 30 can also be made of a relatively thin metal.

[0141] From the perspective of structural simplicity and ease of processing, the frame portion 31, the central portion 32, and the connecting portion 33 are preferably integrally formed, but may also be formed by joining different components. When the frame portion 31, the central portion 32, and the connecting portion 33 are integrally formed, the diaphragm 30 can be formed by, for example, heating and pressurizing a resin film using a mold.

[0142] In the diaphragm 30, the lower surface of the frame portion 31 can be bonded to the upper surface of the fixed portion 21 of the MEMS device 20 via an adhesive layer, for example. Furthermore, the lower surface of the central portion 32 can be bonded to the upper surface of the movable portion 22 of the MEMS device 20 via an adhesive layer, for example. The adhesive layer can be formed of, for example, a thermosetting adhesive. Examples of thermosetting adhesives include epoxy adhesives. The adhesive layer can also be formed of double-sided tape or ultraviolet curing adhesives. When viewed in plan, the central portion 32 and the connecting portion 33 of the diaphragm 30 are located inside the fixed portion 21 of the MEMS device 20 and overlap with the cavity portion 10x of the substrate 10.

[0143] In this way, the structure of securing the diaphragm 30 to the upper surface of the fixed portion 21 of the MEMS device 20 eliminates the need for a frame to secure the diaphragm 30 outside the fixed portion 21 of the MEMS device 20. This maximizes the shape of the MEMS device 20 to the same extent as the external shape constraints of the electroacoustic transducer 1. This increases the area of ​​the drive source 25, allowing the movable portion 22 to be moved with high torque and a large displacement. As a result, high sound pressure can be achieved in the electroacoustic transducer 1. Furthermore, the elimination of the frame reduces the number of components, thereby shortening production cycle time by reducing man-hours. Furthermore, the cost of manufacturing equipment can be reduced.

[0144] The central portion 32 of the diaphragm 30 vibrates in response to the vibration of the movable portion 22 of the MEMS device 20 , thereby generating a sound wave having a vibration frequency in the audible range corresponding to the vibration of the movable portion 22 of the MEMS device 20 .

[0145] exist Figures 12 to 16 In the example shown, a vibration plate 40 is fixed to the upper surface of the central portion 32 of the diaphragm 30. While the diaphragm 30 itself requires soft physical properties, a relatively hard region is preferably provided to increase sound pressure. Placing the vibration plate 40 on the central portion 32 of the diaphragm 30 creates a relatively hard region, thereby increasing sound pressure.

[0146] The vibration plate 40 can be made of, for example, a resin such as PEN (polyethylene naphthalate). Other materials for the vibration plate 40 include metals such as aluminum and carbon. The vibration plate 40 can be secured to the upper surface of the central portion 32 of the diaphragm 30 using, for example, an adhesive or double-sided tape. The thickness of the vibration plate 40 can be, for example, approximately 25 to 100 μm. Alternatively, the vibration plate 40 can be positioned on the lower surface of the central portion 32 of the diaphragm 30.

[0147] The cover member 50 is disposed on the diaphragm 30 as needed. Providing the cover member 50 protects the diaphragm 30 and improves the overall rigidity of the electroacoustic transducer 1. Furthermore, when the electroacoustic transducer 1 is mounted on other components, the cover member 50 can be used as a mounting reference.

[0148] The cover member 50 has a cavity portion 50x on the lower surface side. The outer peripheral area of ​​the cavity portion 50x of the cover member 50 is a frame-shaped thick plate portion, and the cavity portion 50x is a thin plate portion arranged on the inner side of the thick plate portion. The lower surface of the thick plate portion of the cover member 50 can be bonded to the upper surface of the frame portion 31 of the diaphragm 30 via an adhesive layer, for example. The adhesive layer can be formed by, for example, a thermosetting adhesive. Examples of thermosetting adhesives include epoxy adhesives and the like. The adhesive layer can also be formed by double-sided tape or ultraviolet curing adhesives. The cavity portion 50x has one or more openings 50y, and sound waves are output via the openings 50y.

[0149] The electroacoustic transducer 1 can be thin and rigid while having the cover member 50. The thickness of the cover member 50 can be about 0.3 mm in the outer peripheral region outside the cavity 50x and about 0.1 mm in the cavity 50x.

[0150] As a material for the cover member 50, for example, metals such as SUS (stainless steel) and aluminum can be used. Resins such as PC (polycarbonate) can also be used as a material for the cover member 50. From the perspective of achieving a thinner profile while ensuring rigidity, metal is preferably used as the material for the cover member 50.

[0151] The mesh member 70 is positioned on the lower surface 10b of the substrate 10 as needed. The mesh member 70 has a plurality of relatively small openings. A resin such as polyester can be used as the material for the mesh member 70. The mesh member 70 can be bonded to the lower surface 10b of the substrate 10 via an adhesive layer 60 having a central opening, thereby blocking the through-holes 10y of the substrate 10. The adhesive layer 60 is, for example, a double-sided tape.

[0152] By providing mesh 70 and adjusting its aperture ratio, the Q value of the resonant frequency of electroacoustic converter 1 can be reduced, thereby achieving a nearly flat frequency characteristic. Furthermore, providing mesh 70 maintains the flow of air through through-holes 10y, reducing the risk of foreign matter such as dust and water entering the interior of electroacoustic converter 1.

[0153] Figure 17 and Figure 18 : is a diagram illustrating a method for manufacturing the electroacoustic converter of the first embodiment. Figure 17 and Figure 18 In FIG, thick arrows indicate the process flow, and thin arrows indicate the supply of components. Figure 17 The state of each component as viewed from the bottom is shown in FIG. Figure 18 2 shows the state of each component as viewed from the top. For the convenience of explanation, the adhesive layers 200 and 210 are shown as dot patterns.

[0154] First, if Figure 17 As shown in the left end of FIG, a cover member 50 having a cavity portion 50x and an opening portion 50y is prepared. Figure 17 As shown in the center of the cover 50, an adhesive layer 200 is disposed in an annular shape on the lower surface of the outer periphery of the cavity 50x of the cover member 50. The adhesive layer 200 can be formed of an epoxy adhesive, for example. Next, a diaphragm 30 including a frame portion 31, a central portion 32, and a connecting portion 33 is prepared. Figure 17As shown in the right end of FIG, the upper surface of the frame portion 31 of the diaphragm 30 is bonded to the lower surface of the thick plate portion of the cover member 50 via the adhesive layer 200. In addition, before bonding to the cover member 50, the vibration plate 40 is preliminarily arranged on the central portion 32 of the diaphragm 30 by bonding or the like.

[0155] Then, if Figure 18 As shown in the left end of FIG, a substrate 10 and a MEMS device 20 are prepared, and the MEMS device 20 is bonded to the substrate 10. Figure 18 As shown in the center of FIG, an adhesive layer 210 is arranged in an annular shape on the upper surface of the fixing portion 21 of the MEMS device 20. The adhesive layer 210 can be formed of an epoxy adhesive, for example. Then, as shown in FIG. Figure 18 As shown on the right side of Figure 17 The assembly of the diaphragm 30 and the cover member 50 produced in the process is bonded to the upper surface of the fixing portion 21 of the MEMS device 20 via the adhesive layer 210. Subsequently, the mesh member 70 is fixed via the adhesive layer 60 so as to block the through-holes 10y of the substrate 10, thereby completing the electroacoustic transducer 1. Alternatively, the mesh member 70 may be previously fixed to the substrate 10.

[0156] <Second embodiment>

[0157] In the second embodiment, an example is shown in which the connection positions of the torsion beam, the movable portion, and the drive beam are different in the MEMS device.

[0158] Figure 19 This is a plan view illustrating a MEMS device according to the second embodiment. Figure 19 The MEMS device 20A shown is similar to the MEMS device 20 (see Figure 3 Compared to the MEMS device 20A (e.g., FIG. 2 ), the connection positions of the torsion beam 23 to the movable portion 22 and the drive beam 24 are different. In the MEMS device 20A, similar to the MEMS device 20, each drive beam 24 has a region whose width in a direction parallel to the first side 24a connected to the inner edge of the fixed portion 21 gradually widens toward the first side 24a when viewed in plan.

[0159] exist Figure 3 In the MEMS device 20 shown in FIG. 1 , the upper base of the trapezoid constituting the second region 242 is connected to the torsion beam 23 when viewed in plan, but Figure 19 In the illustrated MEMS device 20A, the side of the trapezoid forming the second region 242, which is closest to the movable portion 22, is connected to the torsion beam 23. Furthermore, the lower base of the trapezoid forming the first region 241 coincides with the first side 24a. In the MEMS device 20A, the upper base of the trapezoid forming the first region 241 may also coincide with the lower base of the trapezoid forming the second region 242.

[0160] Figure 202 is a graph showing the comparison results of the MEMS device 20A and the MEMS device 20, and the displacement of the movable portion 22 and the sound pressure level SPL at 20 Hz of the two devices were obtained by simulation. Figure 20 As shown, there is no significant difference in characteristics between the MEMS device 20A and the MEMS device 20 , and both can fully function as MEMS speakers. However, the MEMS device 20 slightly outperforms the MEMS device 20 in terms of displacement and sound pressure level.

[0161] <Third embodiment>

[0162] In the third embodiment, an example is described in which diaphragms having different shapes are used in the electroacoustic transducer.

[0163] Figure 21 1 is an exploded perspective view of the upper surface side of the electroacoustic converter according to the third embodiment. Figure 21 When the electroacoustic converter 1A and the electroacoustic converter 1 (refer to Figure 15 The difference compared to the diaphragm 30 is that the diaphragm 30 is replaced by the diaphragm 30A.

[0164] Diaphragm 30A includes a frame portion 31 with a circular inner edge, a circular central portion 32A located inward of the inner edge of frame portion 31, and a connecting portion 33 connecting the inner edge of frame portion 31 to the outer edge of central portion 32A. The lower surface of central portion 32A is connected to the upper surface of movable portion 22. A vibration plate 40 is disposed on the upper surface of central portion 32A. The shape of vibration plate 40 is also circular, corresponding to the shape of central portion 32A.

[0165] In the diaphragm 30A, the upper surface of the frame portion 31 and the upper surface of the central portion 32A are, for example, located on the same plane, and the lower surface of the frame portion 31 and the lower surface of the central portion 32A are, for example, located on the same plane. The connecting portion 33 protrudes further than the upper surface of the central portion 32A, and in a cross-sectional view taken perpendicular to the upper surface of the central portion 32A, the upper and lower surfaces of the connecting portion 33 are curved in the same direction. The connecting portion 33 has a plurality of slits 34 arranged at predetermined intervals in a direction extending annularly and approximately perpendicular thereto. When viewed in plan, the length direction of each slit 34 is oriented toward the center of the central portion 32A. When viewed in plan, the length direction of each slit 34 may also be oriented tangentially relative to the circular inner edge of the frame portion 31. The frame portion 31, the central portion 32A, and the connecting portion 33 are, for example, integrally constructed. Furthermore, similar to the case of the diaphragm 30 , the upper surface and the lower surface of the frame portion 31 and the upper surface and the lower surface of the central portion 32A may be configured so as not to be flush with each other.

[0166] Figure 22 is the simulation result of the resonant frequency of the MEMS device and the diaphragm. Figure 22The "Structure" column shows a simulation of the resonant frequency of a diaphragm comprising a MEMS device and a vibration plate. The MEMS device 20 is not shown. Diaphragms 30 and 30A are made of the same material and have the same thickness. Furthermore, the vibration plates 40 are made of the same material and have the same thickness, and the lengths of the arrows are the same.

[0167] like Figure 22 As shown, the resonant frequency of diaphragm 30A is higher than that of diaphragm 30. Specifically, a circular shape is lighter than a rectangular shape for the center portion and diaphragm, making it easier to drive and resulting in a higher resonant frequency. Furthermore, a circular shape for the center portion and diaphragm is preferred because it minimizes deformation and reduces the likelihood of unwanted resonance in the torsional direction.

[0168] Thus, when the central portion 32A of the diaphragm 30 and the vibration plate 40 are made circular, the resonance frequency becomes higher. Also, as described above, when the movable portion 22 is made lighter, the resonance frequency becomes higher. Figure 23 As shown, the resonance frequency also changes according to the thickness of the torsion beam 23 and the drive beam 24 . Figure 23 These are simulation results of the resonance frequency when the thickness of the torsion beam and the drive beam are changed. Note that the thickness of the piezoelectric film constituting the drive source 25 and the number of layers of the piezoelectric film are the same.

[0169] like Figure 23 As shown, circularizing the center of the diaphragm and the diaphragm, and increasing the thickness of the torsion beam 23 and drive beam 24, can increase the resonant frequency. For example, by setting the thickness of the torsion beam 23 and drive beam 24 to between 25 μm and 35 μm, the resonant frequency can be adjusted to approximately 1.5 kHz to 2.5 kHz. As mentioned above, this corresponds to the optimal resonant frequency when considering the Harman curve. Furthermore, increasing the thickness of the torsion beam 23 and drive beam 24 results in higher torque.

[0170] <Fourth embodiment>

[0171] In the fourth embodiment, an example is shown in which pads for height alignment and positioning are arranged on a MEMS device.

[0172] Figure 24 It is an exploded perspective view of the upper surface side showing an example of an electroacoustic transducer according to a fourth embodiment. Figure 25 1 is a top view showing an example of a substrate constituting an electroacoustic converter according to a fourth embodiment. Figure 24 and Figure 25 When the electroacoustic converter 1B and the electroacoustic converter 1 (refer to Figure 15 The difference compared to the above embodiment is that a height alignment pad 14 is added to the substrate 10.

[0173] In the electroacoustic transducer 1B, a pair of internal connection pads 11a and 11b, which serve as a path for signals supplied to the drive source 25 of the MEMS device 20, and a height alignment pad 14 are arranged in an area of ​​the upper surface 10a of the substrate 10 that overlaps with the fixing portion 21 of the MEMS device 20 when viewed in plan. The height alignment pad 14 is arranged separately from the internal connection pads 11a and 11b. Since the height alignment pad 14 is a dummy pad, it does not need to be electrically connected (it can be left floating).

[0174] In the electroacoustic transducer 1B, the lower surface of the fixing portion 21 of the MEMS device 20 is bonded to the upper surface 10 a of the substrate 10 with the internal connection pads 11 a and 11 b and the height alignment pad 14 interposed therebetween.

[0175] The height alignment pads 14 and the internal connection pads 11a and 11b are positioned at the same height from the top surface 10a of the substrate 10. The height (i.e., thickness) of the internal connection pads 11a and 11b and the height alignment pads 14 from the top surface 10a of the substrate 10 can be set, for example, to be approximately 10 μm to 50 μm. The height alignment pads 14 are provided to reduce the tilt of the MEMS device 20 disposed on the substrate 10 relative to the top surface 10a of the substrate 10.

[0176] In this embodiment, the substrate 10 has a rectangular shape in a plan view having a first side 101 and a second side 102 facing each other, and a third side 103 and a fourth side 104 facing each other.

[0177] In this case, the height alignment pad 14 needs to be arranged at least along the second side 102. In order to more reliably reduce the tilt of the MEMS device 20, as shown in FIG. Figure 25 As shown, the height alignment pads 14 are preferably arranged one each along the second side 102, the third side 103, and the fourth side 104. For example, the three height alignment pads 14 can be arranged near the center of each of the second side 102, the third side 103, and the fourth side 104.

[0178] Figure 26 It is a plan view showing the process of arranging a MEMS device on a substrate. Figure 27 is a cross-sectional view showing the process of configuring a MEMS device on a substrate, showing the Figure 26 The cross section of the CC line.

[0179] like Figure 26 and Figure 27 As shown, in order to configure the MEMS device 20 on the substrate 10, first, as shown in FIG. Figure 26 and Figure 27The substrate 10 is prepared as shown by the base of the arrow in FIG. Next, an adhesive layer 210 is placed in a ring shape on the upper surface 10a of the substrate 10, along the arrow, exposing the internal connection pads 11a and 11b and covering each height alignment pad 14. Furthermore, a conductive bonding material 310 is placed on the internal connection pads 11a and 11b exposed from the adhesive layer 210. The conductive bonding material 310 can be, for example, a conductive paste (e.g., silver paste) or solder.

[0180] Next, the MEMS device 20 is sucked onto the suction jig 400 as indicated by the arrow, and then moved onto the substrate 10 for alignment. Next, the suction jig 400 is lowered as indicated by the arrow to position and press the MEMS device 20 onto the substrate 10. The suction is then released, and the suction jig 400 is removed from the MEMS device 20. At this point, the MEMS device 20 is supported by the internal connection pads 11 a and 11 b and the height alignment pads 14, allowing the MEMS device 20 to be fixed with little tilt relative to the upper surface 10 a of the substrate 10.

[0181] That is, the parallelism between the substrate 10 and the MEMS device 20 can be maintained, and electrical conduction between the substrate 10 and the MEMS device 20 and sealing by the adhesive layer 210 can be reliably achieved. Furthermore, the substrate 10, the MEMS device 20, and the adhesive layer 210 can secure a designed spatial area.

[0182] By disposing the height alignment pads 14 in this manner, it is possible to improve the assembly accuracy of the MEMS device 20 and the surrounding members.

[0183] In addition, it is also considered to increase the number of internal connection pads instead of providing a design for height alignment pads 14, for example, in addition to the first side 101, internal connection pads are also arranged on other sides. However, in this case, since the through wiring connected to the internal connection pads also needs to be arranged along each side, the substrate 10 becomes larger, so it is not recommended. In addition, if the number of internal connection pads increases, the number of parts to be joined using conductive bonding material also increases, so there is a concern that the connection reliability will be reduced. By providing only a pair of internal connection pads as in the present embodiment, and providing a height alignment pad separately from the internal connection pads, the above concerns can be eliminated.

[0184] Figure 28 This is a plan view illustrating a substrate constituting the electroacoustic transducer according to Modification 1 of the fourth embodiment. Figure 28In the embodiment, two height alignment pads 14a are arranged on the upper surface 10a of the substrate 10. Specifically, one height alignment pad 14a is arranged along the corner connecting the second side 102 and the third side 103 and the corner connecting the second side 102 and the fourth side 104, respectively.

[0185] exist Figure 28 Similarly, when the MEMS device 20 is arranged on the substrate 10, the MEMS device 20 is supported by the internal connection pads 11a and 11b and the height alignment pads 14a. Therefore, the MEMS device 20 can be fixed with almost no tilt relative to the upper surface 10a of the substrate 10.

[0186] Figure 29 This is a plan view illustrating a substrate constituting an electroacoustic transducer according to a second modification of the fourth embodiment. Figure 29 In the embodiment, a height alignment pad 14b is disposed on the upper surface 10a of the substrate 10. Specifically, the height alignment pad 14b is disposed along the second side 102 and is disposed so as to extend to a corner connecting the second side 102 and the third side 103 and a corner connecting the second side 102 and the fourth side 104.

[0187] exist Figure 29 In this case, when the MEMS device 20 is arranged on the substrate 10, the MEMS device 20 is also supported by the internal connection pads 11a and 11b and the height alignment pad 14b. Therefore, the MEMS device 20 can be fixed with almost no tilt relative to the upper surface 10a of the substrate 10.

[0188] Figure 30 This is a plan view illustrating a substrate constituting an electroacoustic transducer according to a third modification of the fourth embodiment. Figure 30 In FIG. 1 , in addition to the three height alignment pads 14 , a first alignment pad 15 and a second alignment pad 16 are arranged on the upper surface 10 a of the substrate 10 .

[0189] Specifically, a plurality of first alignment pads 15 are arranged in a region of the upper surface 10a of the substrate 10 that is located outside the fixing portion 21 of the MEMS device 20 in a plan view. Figure 30 In the example shown in FIG. 1 , one first alignment pad 15 is disposed along each of the two end portions of each side of the substrate 10 , and a total of eight first alignment pads 15 are disposed.

[0190] A plurality of second alignment pads 16 are arranged on the upper surface 10a of the substrate 10 in a region outside the fixing portion 21 of the MEMS device 20 in a plan view. Figure 30In the example shown in FIG, one second alignment pad 16 is provided along each of a pair of opposing sides of the substrate 10, for a total of two second alignment pads 16. For example, in a plan view, the second alignment pad 16 can be provided at a position sandwiched between two first alignment pads 15 provided on the same side of the substrate 10 in an opposing manner.

[0191] Figure 26 and Figure 27 In the embodiment, the first alignment pads 15 and / or the second alignment pads 16 can be used for alignment when placing the adhesive layer 210 and the MEMS device 20 on the substrate 10. Specifically, the first alignment pads 15 can be used for alignment when placing the MEMS device 20 on the substrate 10 using, for example, a suction jig 400. Furthermore, the second alignment pads 16 can be used as identification marks when placing the adhesive layer 210 on the substrate 10 using, for example, a robot.

[0192] Figure 31 : is a top view showing the state after the MEMS device is aligned on the substrate. Figure 31 The upper portion is an overall view of the substrate 10 and the MEMS device 20 , and the lower portion is an enlarged view of the inner side of the dotted line of the upper portion.

[0193] like Figure 31 As shown, when the first alignment pads 15 are used for alignment, the sides of the first alignment pads 15 facing the center of the substrate 10 are arranged so as to coincide with the outer edges of the MEMS device 20 in a plan view. This allows alignment of the MEMS device 20 and the substrate 10.

[0194] When the second alignment pads 16 are used for alignment, the MEMS device 20 and the substrate 10 can be aligned by recognizing the two second alignment pads 16 as identification marks. Furthermore, the adhesive layer 210 and the substrate 10 can be aligned by recognizing the two second alignment pads 16 as identification marks.

[0195] Furthermore, the first alignment pads 15 and the second alignment pads 16 may both be provided on the substrate 10, or only one of them may be provided, depending on the specifications of the device being used. For example, by selecting the device, only the second alignment pads 16 may be used to perform both the alignment of the adhesive layer 210 on the substrate 10 and the alignment of the MEMS device 20.

[0196] By disposing the first alignment pads 15 and / or the second alignment pads 16 in this manner, it is possible to improve the assembly accuracy of the MEMS device 20 and the surrounding members.

[0197] <Fifth embodiment>

[0198] In the fifth embodiment, an example of laying out wiring arranged in a MEMS device is described.

[0199] Figure 32 1 is a bottom view showing the wiring of the MEMS device according to the fifth embodiment. Figure 32 , the MEMS device 20B includes a pair of conduction pads 28 a and 28 b , a first wiring 41 , and a second wiring 42 .

[0200] The conductive pads 28a and 28b, the first wiring 41, and the second wiring 42 form a path for signals supplied to the drive source 25 of the MEMS device 20B. The conductive pads 28a and 28b, the first wiring 41, and the second wiring 42 can be arranged, for example, on the lower surface of the fixed portion 21. The first wiring 41 and the second wiring 42 can also extend from the lower surface of the fixed portion 21 to the lower surfaces of the drive beam 24, the torsion beam 23, and the movable portion 22.

[0201] The conductive pads 28a and 28b, the first wiring 41, and the second wiring 42 can be formed of, for example, gold. The thickness of the conductive pads 28a and 28b, the first wiring 41, and the second wiring 42 can be set to, for example, approximately 0.05 μm to 1.00 μm.

[0202] The first wiring 41 electrically connects the conduction pad 28a, one of the pair of conduction pads, to one electrode of each drive source 25. The second wiring 42 electrically connects the conduction pad 28b, the other of the pair of conduction pads, to the other electrode of each drive source 25.

[0203] Specifically, when each driving source 25 has an upper electrode and a lower electrode but no intermediate electrode, for example, the first wiring 41 is connected to the lower electrode, and the second wiring 42 is connected to the upper electrode. Alternatively, the first wiring 41 may be connected to the upper electrode, and the second wiring 42 may be connected to the lower electrode.

[0204] When each driving source 25 has an upper electrode, a lower electrode, and an intermediate electrode, the first wiring 41 is connected to the upper electrode and the lower electrode, and the second wiring 42 is connected to the intermediate electrode. Alternatively, the first wiring 41 may be connected to the intermediate electrode, and the second wiring 42 may be connected to the upper electrode and the lower electrode.

[0205] The first wiring 41 includes a loop wiring 41a and branch wirings 41b that branch from the loop wiring 41a and are connected to the respective drive sources 25. The loop wiring 41a extends from the conduction pad 28a and is arranged in a loop shape to surround the multiple drive sources 25 in a plan view, and then returns to the conduction pad 28a. The second wiring 42 is arranged inward of the loop wiring 41a in a plan view.

[0206] exist Figure 32 In the example shown, the second wiring 42 extends from the conduction pad 28b, passes through each drive source 25, and returns to the conduction pad 28b. For example, the second wiring 42 includes four portions 42a that directly connect adjacent drive sources 25. Each portion 42a is arranged along a portion of the loop wiring 41a that connects adjacent branch wirings 41b. This arrangement makes it easier for the second wiring 42 to extend from the conduction pad 28b and return to the conduction pad 28b via each drive source 25.

[0207] Thus, in the MEMS device 20B, the first wiring 41 includes the loop wiring 41a and the branch wiring 41b. Furthermore, the second wiring 42 extends from the conduction pad 28b, passes through each drive source 25, and returns to the conduction pad 28b. This wiring shortens the paths of the first wiring 41 and the second wiring 42 connecting the conduction pads 28a and 28b to the respective drive sources 25.

[0208] Therefore, it is possible to suppress the delay of the signal input to the driving source 25 farther from the conduction pads 28a and 28b relative to the signal input to the driving source 25 closer to the conduction pads 28a and 28b. In other words, signals with a small phase difference can be input to the driving source 25 closer to the conduction pads 28a and 28b and the driving source 25 farther from the conduction pads 28a and 28b. As a result, the displacement of the movable portion 22 can be increased.

[0209] Furthermore, if the phases of the signals input to the drive sources 25 deviate, the drive sources 25 can be driven in directions that cancel out the displacement of the movable portion 22. However, in the MEMS device 20B, when signals with smaller phase differences are input to the drive sources 25, it becomes difficult to cancel out the displacement of the movable portion 22. This improves the frequency characteristics of the MEMS device 20B. This effect is particularly significant when the signal frequency is high.

[0210] Furthermore, it is preferable that the first wiring 41 is connected to the ground wiring of the external circuit, and the second wiring 42 is connected to the signal wiring of the external circuit. In this case, the second wiring 42 connected to the signal wiring is surrounded by the first wiring 41 connected to the ground wiring, thereby reducing the possibility of noise being superimposed on the second wiring 42.

[0211] And, in Figure 32 In the example of , it is possible to achieve miniaturization of the MEMS device 20B and improve the connection reliability between the MEMS device 20B and the substrate 10. This will be described in detail below.

[0212] The fixing portion 21 of the MEMS device 20B requires a certain width for reasons such as ensuring a sufficient area for bonding to the substrate 10, ensuring space for arranging the first and second wirings 41 and 42, and ensuring space for arranging the conductive bonding material used for connection to the internal connection pads 11a and 11b of the substrate 10. If the width of the fixing portion 21 is made bilaterally symmetrical, the horizontal dimension of the fixing portion 21 will increase. Furthermore, if the width of the fixing portion 21 is made vertically and horizontally symmetrical, the outer shape of the fixing portion 21 will increase in the vertical, horizontal, and vertical directions.

[0213] Therefore, if Figure 32 As shown, in the MEMS device 20B, the fixed portion 21 has a rectangular frame shape. The width of the portion along the first side 201 of the fixed portion 21 is wider than the width of the portions along the other three sides, and the center of the outer edge of the fixed portion 21 does not coincide with the center of the movable portion 22. For example, the width of the portion along the first side 201 of the fixed portion 21 can be 0.9 mm, while the width of the portions along the other three sides can be 0.5 mm. Furthermore, on the lower surface of the portion of the fixed portion 21 along the wider first side 201, only a pair of conductive pads 28a and 28b are provided for the multiple drive sources 25. This structure reduces the width of the portions along the other three sides of the fixed portion 21, excluding the first side 201, thereby miniaturizing the MEMS device 20B.

[0214] Specifically, a method of providing a pair of conduction pads for each drive source 25 is also conceivable. However, if there are four drive sources 25, eight conduction pads are required. Therefore, to ensure space for the conduction pads, the MEMS device becomes larger. However, the MEMS device 20B only has a pair of conduction pads 28a and 28b, which allows for miniaturization.

[0215] Furthermore, the conductive pads 28a and 28b are connected to the internal connection pads 11a and 11b of the substrate 10 via a conductive bonding material. However, since the number of connected pads is small, high connection reliability can be achieved. Furthermore, since the conductive pads 28a and 28b are easily connected to the pads of the substrate 10, this also contributes to cost reduction.

[0216] In addition, if Figure 25As shown in FIG. 1 , substrate 10, like MEMS device 20B, can be configured such that the width of a portion along one side is wider than the width of portions along the other three sides, and the center of the outer edge of substrate 10 does not coincide with the center of cavity 10x. Furthermore, internal connection pads 11a and 11b and through-wirings 13a and 13b can be arranged in the widened portion. This structure reduces the width of portions along the other three sides, excluding those where internal connection pads 11a and 11b and through-wirings 13a and 13b are arranged, thereby miniaturizing substrate 10. Furthermore, miniaturizing substrate 10 and MEMS device 20B can also miniaturize the entire electroacoustic transducer device.

[0217] Figure 33 This is the simulation result of stress distribution when the movable part of the MEMS device is moved. Figure 33 The lower portion shows the entire lower surface of the MEMS device 20B, and the upper portion shows an enlarged view of the area inside the dotted line of the lower portion. The enlarged view also shows the conduction pad 28a, the first wiring 41, and a portion of the second wiring 42.

[0218] like Figure 33 As shown, there is an area near the inner edge of the fixed portion 21 where high stress is applied. Therefore, the first wiring 41 and the second wiring 42 are preferably arranged to avoid this area where high stress is applied. This can reduce the risk of disconnection of the first wiring 41 and / or the second wiring 42 when the movable portion 22 of the MEMS device 20B is moved.

[0219] Figure 34 This is a bottom view showing the wiring of the MEMS device according to the first modification of the fifth embodiment. Figure 34 When the configuration of the second wiring 42 of the MEMS device 20C is Figure 32 The MEMS device 20B shown is different.

[0220] Specifically, in Figure 34 In the example, a portion of the second wiring 42 is arranged on the lower surface of the movable portion 22 and the plurality of torsion beams 23. According to this arrangement, the path of the second wiring 42 connecting the conductive pad 28b to each drive source 25 can be shortened. In addition, the path of the first wiring 41 connecting the conductive pad 28a to each drive source 25 can be shortened. Figure 32 Therefore, it is possible to suppress the delay of the signal input to the driving source 25 far from the conductive pads 28a and 28b relative to the signal input to the driving source 25 close to the conductive pads 28a and 28b. Figure 32 , the displacement of the movable portion 22 can be increased, and the frequency characteristics of the MEMS device 20C can be improved.

[0221] <Sixth Implementation>

[0222] In the sixth embodiment, an example is described in which the inspection of the displacement of the movable portion of the MEMS device is facilitated.

[0223] Figure 35 1 is a bottom view showing a metal film of a MEMS device according to a sixth embodiment. Figure 35 In the MEMS device 20D, a cross-shaped metal film 43 is arranged on the lower surface of the movable portion 22 .

[0224] Examples of materials for the metal film 43 include gold (Au), copper (Cu), silver (Ag), aluminum (Al), platinum (Pt), titanium (Ti), and tungsten (W). The thickness of the metal film 43 can be, for example, approximately 0.02 μm to 1.00 μm. The metal film 43 can be formed, for example, by sputtering. The visible light reflectivity of the metal film 43 is 80% or greater.

[0225] Furthermore, from the perspective of simplifying the manufacturing process, the metal film 43 is preferably formed of the same material as that of the first wiring 41 and the second wiring 42. For example, if the first wiring 41 and the second wiring 42 are made of gold, the metal film 43 is also preferably formed of gold. Alternatively, the metal film 43 may be formed of the same material as that of the electrode constituting the driving source 25. For example, if the electrode constituting the driving source 25 is made of platinum, the metal film 43 is also preferably formed of platinum.

[0226] Figure 36 This is a bottom view of an electroacoustic transducer 1C using a MEMS device 20D. As described above, substrate 10 includes through-holes 10y, which serve as air inlet and outlet paths for the interior of substrate 10. Furthermore, when viewed from above, metal film 43 is located overlapping through-holes 10y. Therefore, light can be irradiated onto metal film 43 from outside of electroacoustic transducer 1C, and light reflected from metal film 43 can be received outside of electroacoustic transducer 1C.

[0227] With this configuration, even after the MEMS device 20D is mounted on the substrate 10, etc., an optical displacement meter can be used to measure the displacement of the movable portion 22. Of course, the displacement of the movable portion 22 can also be measured using the MEMS device 20D alone. Furthermore, an optical displacement meter irradiates light onto the object being measured, measures the angle, position, and velocity of the reflected light from the object, and calculates the displacement of the object. Examples of optical displacement meters include laser displacement meters. Laser displacement meters use, for example, red laser light with a wavelength of approximately 630 to 690 nm.

[0228] When the movable portion 22 of the MEMS device 20D is made of silicon, the reflectivity in the wavelength range of red laser light is approximately 35%. Therefore, if the metal film 43 is not provided on the lower surface of the movable portion 22, even if a laser displacement meter is used to measure the displacement of the movable portion 22, the amount of reflected light is insufficient, and high-precision measurement cannot be expected.

[0229] In contrast, when the metal film 43 is provided on the lower surface of the movable portion 22, the reflectivity in the wavelength range of the red laser light can be ensured to be 80% or higher. Therefore, by irradiating the metal film 43 with light from the laser displacement meter, a sufficient amount of reflected light can be obtained, thereby improving the signal-to-noise ratio and enabling highly accurate measurement of the displacement of the movable portion 22. This results in a MEMS device 20D capable of highly accurate measurement of the displacement of the movable portion 22.

[0230] Figure 37 This is the process for measuring the displacement of the movable portion. First, in step S101, the movable portion 22 is displaced. For example, the movable portion 22 can be repeatedly displaced at a constant frequency and amplitude. Next, in step S102, light is irradiated onto the metal film 43 from a laser displacement meter or the like, and the laser displacement meter or the like receives the reflected light from the metal film 43. Next, in step S103, the displacement of the movable portion 22 is calculated based on the received reflected light.

[0231] In this way, by configuring the metal film 43 on the lower surface of the movable part 22, the displacement of the movable part 22 can be measured with high precision. In addition, it is also possible to perform sound pressure measurement or impedance measurement instead of measuring the displacement of the movable part 22. However, since the sound pressure measurement requires a dedicated device, the inspection cost becomes high. In addition, the impedance measurement can be performed by a relatively cheap device, but there is a disadvantage that the correlation with the actual acoustic performance is low. In contrast, the displacement of the movable part 22 can be measured using a relatively cheap optical displacement meter, and the correlation with the actual acoustic performance is also sufficiently high.

[0232] Furthermore, when the mesh 70 is provided to block the through-hole 10 y of the substrate 10 , the displacement of the movable portion 22 can be measured before disposing the mesh 70 or after removing the mesh 70 .

[0233] The shape of the metal film formed on the lower surface of the movable portion 22 only needs to be larger than the beam diameter of the irradiated light and does not need to conform to the shape of the movable portion 22. When a laser displacement meter is used, the beam diameter of the laser light is approximately 10 μm to 1000 μm. Another example of the shape of the metal film provided on the movable portion 22 is shown below.

[0234] Figure 38This is a bottom view showing a metal film of a MEMS device according to a modification example 1 of the sixth embodiment. Figure 38 In the MEMS device 20E, a triangular metal film 43 a is arranged on the lower surface of the movable portion 22 . Figure 39 This is a bottom view showing a metal film of a MEMS device according to a second modification of the sixth embodiment. Figure 39 In the MEMS device 20F, a substantially mountain-shaped metal film 43 b is disposed on the lower surface of the movable portion 22 .

[0235] By disposing metal film 43a or 43b on the lower surface of movable portion 22, the displacement of movable portion 22 can be measured with high precision, similar to the case of disposing metal film 43. Furthermore, unlike metal film 43, metal films 43a and 43b are not point-symmetrical. Specifically, metal films 43a and 43b taper toward guide pads 28a and 28b. Therefore, they can be used to determine the orientation of MEMS devices 20E and 20F.

[0236] When assembling MEMS devices 20E and 20F on substrate 10, it is necessary to bond conduction pads 28a and 28b to internal connection pads 11a and 11b on substrate 10. Therefore, it is necessary to align the orientation of MEMS devices 20E and 20F with substrate 10. Visually checking metal films 43a and 43b makes it easy to determine the orientation of MEMS devices 20E and 20F, thereby preventing incorrect orientation during assembly on substrate 10.

[0237] In the above description, an example of measuring the displacement of the movable part 22 by providing a metal film on the lower surface of the movable part 22 is shown. As another method, it is also possible to measure the displacement of the movable part 22 by Figure 12 In the method shown in FIG. 1 , the diaphragm side of the electroacoustic transducer is irradiated with light to measure the displacement of the movable part.

[0238] For example, in Figure 12 In the illustrated electroacoustic transducer 1, the diaphragm 40 is exposed through the opening 50y of the cover member 50. Therefore, by irradiating light from a laser displacement meter or the like onto the diaphragm 40 and receiving the reflected light from the diaphragm 40, the displacement of the movable portion 22 can be calculated. Furthermore, since the central portion 32 of the diaphragm 30 and the diaphragm 40 displace in the same manner as the movable portion 22, it is sufficient to measure the displacement of the diaphragm 40, which becomes the displacement of the movable portion 22.

[0239] When the vibration plate 40 is formed of a material with low reflectivity, such as resin, a metal film similar to the metal film 43 needs to be deposited on at least the area of ​​the upper surface of the vibration plate 40 where light is irradiated, in order to improve measurement accuracy. However, when the vibration plate 40 is formed of a metal material, the metal film does not need to be disposed.

[0240] Furthermore, when the vibrating plate 40 is not provided on the central portion 32 of the diaphragm 30, or when the vibrating plate 40 is provided on the lower surface side of the central portion 32 of the diaphragm 30, light can be irradiated from a laser displacement meter or the like toward the central portion 32 of the diaphragm 30. The laser displacement meter or the like then receives the reflected light from the central portion 32 of the diaphragm 30, and the displacement of the movable portion 22 can be calculated. Furthermore, since the central portion 32 of the diaphragm 30 displaces in the same manner as the movable portion 22, it is sufficient to measure the displacement of the central portion 32 of the diaphragm 30, which serves as the displacement of the movable portion 22.

[0241] When the diaphragm 30 is formed of a material with low reflectivity, such as resin, in order to improve measurement accuracy, it is necessary to arrange a metal film similar to the metal film 43 by vapor deposition or the like on at least the area of ​​the upper surface of the central portion 32 of the diaphragm 30 where light is irradiated. However, when the diaphragm 30 is formed of a metal material, it is not necessary to arrange a metal film.

[0242] When measuring the displacement of the movable portion by irradiating light from the diaphragm side of the electroacoustic transducer, the position of the through-hole 10y in the substrate 10 is irrelevant to the displacement measurement, allowing the through-hole 10y to be positioned at any desired location. This increases the design freedom of the placement of the through-hole 10y.

[0243] Thus, the method for measuring the displacement of a movable part in this embodiment includes: a step of displacing the movable part; a step of irradiating light from outside the electroacoustic converter device onto the movable part or a portion that displaces in conjunction with the movement of the movable part; and a step of calculating the displacement based on reflected light from the irradiated light. Furthermore, a metal film is disposed at the location where the light is irradiated, or the portion where the light is irradiated is formed of a metal material. This allows for highly accurate measurement of the displacement of the movable part.

[0244] Seventh embodiment

[0245] In the seventh embodiment, an example in which a concavo-convex structure is provided on a diaphragm is described.

[0246] Figure 40 : is a cross-sectional view showing an example of an electroacoustic converter according to a seventh embodiment. Figure 40 The upper part is an overall view of the electroacoustic converter, and the lower part is an enlarged view of the inner side of the dotted line of the upper part.

[0247] like Figure 40 As shown, the electroacoustic converter 1D is similar to the electroacoustic converter 1 (see Figure 14 The difference compared with the diaphragm 30 is that the diaphragm 30D is provided instead of the diaphragm 30.

[0248] Diaphragm 30D includes frame 31, central portion 32, and connecting portion 33. Concavo-convex structure 35 is provided on the upper and lower surfaces of frame 31. The structure, material, and thickness of diaphragm 30D other than concavo-convex structure 35 can be the same as those of diaphragm 30, for example.

[0249] The diaphragm 30D can be formed by heating and pressurizing a resin material using a mold, for example. However, by providing a concavo-convex structure in advance on the surface of the mold used in this case, the concavo-convex structure 35 can be formed simultaneously with the frame 31 and the like.

[0250] The concavo-convex structure 35 includes, for example, a plurality of first protrusions 35a protruding from the upper surface of the frame portion 31 and a plurality of first concave portions 35b recessed from the lower surface of the frame portion 31 toward the upper surface, serving as the opposite surface. When viewed in plan, the first protrusions 35a and the first concave portions 35b overlap. The height of the first protrusions 35a from the upper surface of the frame portion 31 is, for example, approximately 20 to 40 μm. Furthermore, the depth of the first concave portions 35b from the lower surface of the frame portion 31 is, for example, approximately 20 to 40 μm.

[0251] Furthermore, at least a portion of the concavo-convex structure 35 is located at a position where the upper surface of the fixing portion 21 of the MEMS device 20 overlaps with the lower surface of the thick plate portion 51 of the cover member 50 when viewed in plan. The upper side of the concavo-convex structure 35 is bonded to the thick plate portion 51 of the cover member 50 via the adhesive layer 200. Furthermore, the lower side of the concavo-convex structure 35 is bonded to the fixing portion 21 of the MEMS device 20 via the adhesive layer 210.

[0252] In this manner, the provision of the concavo-convex structure 35 produces an anchoring effect, thereby achieving a diaphragm 30D with improved bonding strength to other components. Specifically, the bonding strength between the frame portion 31 of the diaphragm 30D and the thick plate portion 51 of the cover member 50 can be improved, and the bonding strength between the frame portion 31 of the diaphragm 30D and the fixing portion 21 of the MEMS device 20 can be improved.

[0253] In addition, the concavo-convex structure 35 may be a structure including a plurality of first convex portions protruding from the lower surface of the frame portion 31 and a plurality of first concave portions recessed from the upper surface of the frame portion 31 toward the lower surface as the opposite surface. Figure 40 The concavo-convex structure 35 shown is a structure in which the concavo-convex structure 35 is reversed upside down. In this case, the same effect as above is achieved.

[0254] Figure 41 FIG is a top view showing an example of a diaphragm 30D. Figure 41 As shown, the concavo-convex structure 35 is preferably provided on the entire frame portion 31 of the diaphragm 30D. The first convex portion 35a and the first concave portion 35b may be rectangular, circular, or other shapes in a plan view.

[0255] Furthermore, the shapes of the first convex portion 35a and the first concave portion 35b in a plan view may be point-symmetrical or non-point-symmetrical. Furthermore, the shapes of the first convex portion 35a and the first concave portion 35b in a plan view are not limited to the following: Figure 41 The dot shape shown may be, for example, a narrow and long straight line, a curved line, or a mixture of the above shapes. Furthermore, the straight lines and curved lines may intersect in a grid pattern.

[0256] Figure 42 FIG. 1 is a partial cross-sectional view illustrating an electroacoustic converter according to a first modification of the seventh embodiment. Figure 42 As shown in the concave-convex structure 35M, the cross-sectional shape of the first convex portion 35a and the first concave portion 35b can also be a curved shape such as a part of a circle or an ellipse. In this case, the concave-convex structure 35M also produces an anchoring effect, thereby playing a role in Figure 40 The same effect as the situation.

[0257] Figure 43 This is a partial cross-sectional view illustrating an electroacoustic transducer according to Modification 2 of the seventh embodiment. Figure 43 The illustrated concavo-convex structure 35N includes a plurality of first convex portions 35a protruding from the upper surface of the frame portion 31, a plurality of second convex portions 36a protruding from the lower surface of the frame portion 31, a plurality of first concave portions 35b recessed from the lower surface of the frame portion 31 toward the upper surface, and a plurality of second concave portions 36b recessed from the upper surface toward the lower surface of the frame portion 31. In plan view, the first convex portions 35a and the first concave portions 35b overlap, and the second convex portions 36a and the second concave portions 36b overlap.

[0258] In this case, the concavo-convex structure 35N also produces an anchoring effect, thereby playing the same role as Figure 40 The same effect is achieved in the case of FIG. In addition, the cross-sectional shapes of the first convex portion 35a, the first concave portion 35b, the second convex portion 36a, and the second concave portion 36b are not limited to Figure 43 The shape shown can also be Figure 40 In this case, the concave-convex structure 35N also produces an anchoring effect, thereby playing the role of Figure 40 The same effect as the situation.

[0259] While preferred embodiments have been described in detail above, the present invention is not limited to the above embodiments and various modifications and substitutions can be made to the above embodiments without departing from the scope of the claims. Furthermore, the content described in one embodiment can also be applied to other embodiments.

Claims

1. A MEMS device, characterized in that: have: a frame-shaped fixing portion; A movable portion disposed inside the fixed portion when viewed in plan; four torsion beams supporting the movable portion; A driving beam is provided for each of the torsion beams, one end of the driving beam being connected to the torsion beam and the other end of the driving beam being connected to the inner edge of the fixing portion; and A driving source is provided for each of the driving beams. The driving beams are arranged symmetrically with respect to the center point of the movable portion in a plan view. In a plan view, each of the driving beams has a region whose width in a direction parallel to a first side connected to the inner edge gradually widens toward the first side.

2. The MEMS device according to claim 1, wherein: When viewed in plan, each of the driving beams has a maximum width at a position on the first side in a direction parallel to the first side.

3. The MEMS device according to claim 2, wherein: In a plan view, each of the driving beams has a narrowest width in a direction parallel to the first side at a position of the second side connected to the torsion beam.

4. The MEMS device according to any one of claims 1 to 3, characterized in that When viewed in plan, each of the driving beams includes a trapezoidal first region and a trapezoidal second region with an area smaller than that of the first region. The first area is located on a side close to the first side. The second region is located on a side farther from the first side than the first region. In each trapezoid constituting the above-mentioned first area and the above-mentioned second area, when the side close to the above-mentioned first side is set as the lower base and the side away from the above-mentioned first side is set as the upper base, the length of the lower base of the trapezoid constituting the above-mentioned second area is less than or equal to the length of the upper base of the trapezoid constituting the above-mentioned first area.

5. The MEMS device according to claim 4, wherein: When viewed in plan, the first side, the upper base of the trapezoid constituting the first region, and the upper base of the trapezoid constituting the second region are parallel.

6. The MEMS device according to claim 4, wherein: In a plan view, one side of the trapezoid constituting the first region and one side of the trapezoid constituting the second region are perpendicular to the first side.

7. The MEMS device according to claim 6, wherein: In a plan view, the other side of the trapezoid constituting the first region and the other side of the trapezoid constituting the second region have different inclination directions relative to the first side.

8. The MEMS device according to claim 6, wherein: In a plan view, one or the other waist of the trapezoid constituting the second region is connected to the torsion beam.

9. The MEMS device according to claim 4, wherein: In a plan view, a rectangular third region is provided between the first side and the first region, and a trapezoidal fourth region is provided between the first region and the second region.

10. A MEMS device, characterized in that: have: A rectangular frame-shaped fixing portion; A movable portion disposed inside the fixed portion when viewed in plan; four torsion beams supporting the movable portion; A driving beam is provided for each of the torsion beams, one end of the driving beam being connected to the torsion beam and the other end of the driving beam being connected to the inner edge of the fixing portion; and A driving source is provided for each of the driving beams. The driving beam is formed of single crystal silicon. The inner edge and the outer edge of the fixing portion are all parallel to the <100> orientation of the crystal orientation of the single crystal silicon.

11. The MEMS device according to claim 10, wherein: The fixed portion, the movable portion, and the torsion beam are formed of single crystal silicon.

12. The MEMS device according to claim 10, wherein: The fixed portion and the movable portion are formed by a support layer, a buried layer, and an active layer constituting an SOI substrate. The torsion beam is formed by the active layer constituting the SOI substrate.

13. An electroacoustic conversion device, characterized in that: have: substrate; The MEMS device according to any one of claims 1 to 3 and claims 10 to 12, which is arranged on the substrate; and A diaphragm is disposed on the MEMS device and bonded to the movable portion.

14. A MEMS device, characterized in that: have: a frame-shaped fixing portion; A movable portion disposed inside the fixed portion when viewed in plan; a plurality of torsion beams supporting the movable portion; A driving beam is provided for each of the torsion beams, one end of the driving beam being connected to the torsion beam and the other end of the driving beam being connected to the inner side surface of the fixing portion; and A driving source is provided for each of the driving beams. The movable portion includes extension portions extending radially from the center in a plan view, the number of which is equal to the number of the torsion beams. Each of the extension portions includes an upper surface, a lower surface, an end surface, and two side surfaces connected to the end surface. Each of the torsion beams is connected to both of the adjacent side surfaces included in different extension portions.

15. The MEMS device according to claim 14, wherein: Each of the torsion beams is connected to the entirety of one of the adjacent side surfaces and a portion of the other side surface in a plan view.

16. The MEMS device according to claim 15, wherein: In each of the torsion beams, a corner of a portion connected to the other of the adjacent side surfaces is arc-shaped when viewed in plan.

17. The MEMS device according to claim 14, wherein: Each of the twist beams includes an L-shaped region when viewed in plan.

18. The MEMS device according to claim 14, wherein: The movable portion has a cross shape that is point-symmetrical with respect to a center of the movable portion in a plan view.

19. The MEMS device according to any one of claims 14 to 18, characterized in that The movable portion has a convex portion protruding from each side of the inner side of the fixed portion toward the movable portion in a plan view and having a thickness equal to that of the fixed portion. Each of the driving beams is connected to an inner side surface of the fixing portion and a side surface of the convex portion that is continuous with the inner side surface.

20. The MEMS device according to claim 19, wherein: In a plan view, a corner of a portion of each of the driving beams connected to a side surface of the convex portion is arc-shaped.

21. The MEMS device according to any one of claims 14 to 18, wherein: The fixing portion has a recessed portion that is recessed from each side of the inner side of the fixing portion toward one side of the outer side when viewed in a plan view. Each of the driving beams is connected to an inner side surface of the fixing portion and an inner side surface of the recessed portion that is continuous with the inner side surface.

22. The MEMS device according to claim 21, wherein: In a plan view, a corner of a portion of each of the driving beams connected to an inner side surface of the recessed portion is arc-shaped.

23. An electroacoustic conversion device, characterized in that: have: substrate; The MEMS device according to any one of claims 14 to 18, disposed on the substrate; and A diaphragm is disposed on the MEMS device and connected to the movable portion.

24. A MEMS device, characterized in that: have: a frame-shaped fixing portion; A movable portion disposed inside the fixed portion when viewed in plan; a torsion beam and a drive beam connecting the fixed portion and the movable portion at positions closer to the lower surface than the upper surfaces of the respective portions; a driving source disposed on the lower surface of the driving beam; a pair of conductive pads disposed on the lower surface of the fixing portion; a first wiring electrically connecting one of the pair of conduction pads to one of the electrodes of each of the drive sources; and a second wiring electrically connecting the other of the pair of conduction pads to the other of the electrodes of each of the drive beams; The first wiring includes a ring wiring and branch wirings branching from the ring wiring and connected to each of the driving sources. The ring wiring extends from one side of the conduction pad and is arranged in a ring shape so as to surround the plurality of driving sources when viewed in plan, and returns to one side of the conduction pad. The second wiring is arranged inside the loop-shaped wiring in a plan view.

25. The MEMS device according to claim 24, wherein: The second wiring extends from the other side of the conduction pad, passes through each of the driving sources, and returns to the other side of the conduction pad.

26. The MEMS device according to claim 25, wherein: The second wiring includes a portion directly connecting adjacent driving sources to each other.

27. The MEMS device according to claim 26, wherein: Each of the portions is arranged along a portion of the ring wiring that connects adjacent branch wirings.

28. The MEMS device according to claim 24, wherein: Part of the second wiring is arranged on a lower surface of the movable portion and lower surfaces of the plurality of torsion beams.

29. The MEMS device according to claim 24, wherein: The first wiring is connected to a ground wiring of an external circuit, and the second wiring is connected to a signal wiring of the external circuit.

30. The MEMS device according to claim 24, wherein: When viewed from above, the fixing portion is in the shape of a rectangular frame, wherein the width of the portion along the first side is wider than the width of the portions along the other three sides. The pair of conduction pads are arranged along the first side.

31. An electroacoustic conversion device, characterized in that: have: substrate; The MEMS device according to any one of claims 24 to 30 configured on the substrate; and A diaphragm is disposed on the MEMS device and bonded to the movable portion.

32. A MEMS device, characterized in that: have: a frame-shaped fixing portion; A movable portion disposed inside the fixed portion when viewed in plan; four torsion beams supporting the movable portion; A driving beam is provided for each of the torsion beams, one end of the driving beam being connected to the torsion beam and the other end of the driving beam being connected to the inner side surface of the fixing portion; and A driving source is provided for each of the driving beams. The movable portion is in a cross shape.

33. The MEMS device according to claim 32, wherein: The movable portion is point-symmetrical with respect to a center of the movable portion in a plan view.

34. The MEMS device according to claim 32, wherein: Each of the twist beams includes an L-shaped region when viewed in plan.

35. The MEMS device according to claim 34, wherein: The torsion beams are point-symmetrical with respect to the center of the movable portion in a plan view.

36. The MEMS device according to claim 32, wherein: The driving beams are point-symmetrical with respect to the center of the movable portion in a plan view.

37. An electroacoustic conversion device, characterized in that: have: substrate; The MEMS device according to any one of claims 32 to 36 configured on the substrate; and A diaphragm is disposed on the MEMS device and connected to the movable portion.

38. The electroacoustic converter according to claim 37, characterized in that When viewed in plan, the diaphragm includes a frame portion having a circular inner edge, a circular central portion located inward of the inner edge of the frame portion, and a connecting portion connecting the inner edge of the frame portion and the outer edge of the central portion. The central portion is connected to the movable portion.

39. The electroacoustic converter according to claim 38, characterized in that The connecting portion protrudes from the upper surface of the central portion. In a cross-sectional view taken in a direction perpendicular to the upper surface of the central portion, the upper surface and the lower surface of the connecting portion are curved in the same direction.

40. The electroacoustic converter according to claim 39, characterized in that The connecting portion has a plurality of slits arranged at predetermined intervals.

41. The electroacoustic converter according to claim 38, characterized in that The frame portion, the central portion, and the connecting portion are integrally structured.

42. The electroacoustic converter according to claim 38, characterized in that A vibration plate is fixed to the central portion.

43. The electroacoustic converter according to claim 38, characterized in that It also has a cover member disposed on the diaphragm, The cover member includes a frame-shaped thick plate portion and a thin plate portion disposed inside the thick plate portion and having an opening. The lower surface of the thick plate portion is joined to the upper surface of the frame portion.

44. The electroacoustic converter according to claim 38, characterized in that A pair of internal connection pads forming a path for a signal supplied to the driving source are arranged on the upper surface of the substrate. A pair of external connection pads are arranged on the lower surface of the substrate. The internal connection pads and the external connection pads are electrically connected via through wirings that penetrate the substrate from the upper surface to the lower surface.

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