Sound conversion device

Abstract

The invention provides a sound conversion device which suppresses invasion of foreign matters between a diaphragm and a fixed electrode. A MEMS microphone (100) is provided with: a substrate (10) having an opening penetrating in a first direction, which is a plate thickness direction; a conductive diaphragm (20) disposed so as to cover the opening (11); and a fixed electrode (40) which faces the diaphragm (20) and in which an opening (70) for adjusting frequency characteristics is formed on the outside of the outer periphery of the fixed electrode (40).

Description

Technical Field

[0001] The present disclosure relates to a sound conversion device. Background Art

[0002] For example, a microphone is known that includes: a substrate having an opening; a vibration electrode plate formed so as to cover the opening; a back plate formed so as to cover the vibration electrode plate; and a fixed electrode plate disposed on the back plate (for example, see Patent Document 1). In the microphone described in Patent Document 1, a plurality of holes are disposed in the center of the vibration electrode plate.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent No. 6127595 Summary of the invention

[0006] Problems to be solved by the invention

[0007] In the conventional microphone, foreign matter that has entered through the opening of the substrate may enter between the vibrating electrode plate (diaphragm) and the fixed electrode plate through the plurality of holes provided in the center of the vibrating electrode plate.

[0008] An object of the present disclosure is to provide a sound conversion device capable of suppressing the intrusion of foreign matter into a space between a diaphragm and a fixed electrode.

[0009] Solutions to Solve Problems

[0010] An acoustic converter according to one aspect of the present disclosure includes: a substrate having an opening; a diaphragm arranged to cover the opening; and a fixed electrode facing the diaphragm and having an opening for adjusting frequency characteristics formed in a region outside the outer periphery of the fixed electrode.

[0011] Effects of the Invention

[0012] The present disclosure can provide a sound conversion device that can suppress the intrusion of foreign matter into a space between a diaphragm and a fixed electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is an exploded perspective view showing the MEMS microphone according to the first embodiment.

[0014] Figure 2 It is a top view showing the diaphragm.

[0015] Figure 3 It means along Figure 2 Cross-sectional view of the cut surface along line III-III.

[0016] Figure 4 It is a plan view showing part of the diaphragm of the MEMS microphone according to the second embodiment.

[0017] Figure 5 It is a plan view showing part of the diaphragm of the MEMS microphone according to the third embodiment.

[0018] Figure 6 It is a plan view showing a diaphragm of a MEMS microphone according to a fourth embodiment.

[0019] Figure 7 It means along Figure 6 Cross-sectional view of the cutting surface along line VII-VII.

[0020] Figure 8 It means along Figure 6 A cross-sectional view of the section taken along line VIII-VIII in FIG.

[0021] Fig. 9 It is a partial plan view showing a diaphragm of a MEMS microphone according to a fifth embodiment.

[0022] Fig.10 It means along Fig. 9 Cross-sectional view of the cut surface along line XX.

[0023] In the figure:

[0024] 100, 100D, 100E—MEMS microphone (sound conversion device), 10—substrate, 11—opening, 20, 20B, 20C, 20D, 20E—diaphragm, 21—movable membrane, 22—fixed membrane, 23—slit, 30—back plate, 31—plurality of holes, 40—fixed electrode, 40a—outer periphery of fixed electrode, 50—support component, 70, 70B, 70C, 70D, 70E—opening for adjusting frequency characteristics, R1—region where the diaphragm and the fixed electrode are opposite to each other, R2—region outside the outer periphery of the fixed electrode, X—X-axis direction, Y—Y-axis direction, Z—Z-axis direction (first direction, plate thickness direction). DETAILED DESCRIPTION

[0025] Hereinafter, the sound conversion device according to the embodiment will be described with reference to the drawings. In addition, in this specification and the drawings, substantially the same components are sometimes denoted by the same reference numerals to omit repeated descriptions.

[0026] [MEMS Microphone 100 of First Embodiment]

[0027] Reference Figure 1 to Figure 3 , a MEMS microphone 100 according to a first embodiment will be described. Figure 1It is an exploded perspective view showing the MEMS microphone 100 according to the first embodiment. Figure 2 It is a top view showing the diaphragm 20 . Figure 3 It means along Figure 2 1 and 2. In addition, in each figure, three orthogonal directions, namely, the X-axis direction, the Y-axis direction, and the Z-axis direction are shown. The Z-axis direction is the thickness direction of the substrate 10 and is an example of the first direction. In addition, in the following description, "upper" and "lower" are sometimes used, but the configuration of the MEMS microphone 100 is not limited to this.

[0028] like Figure 1 As shown, the MEMS microphone 100 includes a substrate 10, a diaphragm 20, a back plate 30, a fixed electrode 40, and a support member 50. The MEMS microphone 100 is an example of a "sound conversion device". The MEMS microphone 100 is an electrostatic capacitance type element manufactured using MEMS technology. "MEMS" is an abbreviation for Micro Electro Mechanical System. The sound conversion device is not limited to the MEMS microphone 100, and can be other sound sensors or a speaker.

[0029] [Substrate 10]

[0030] The substrate 10 is formed of, for example, single crystal silicon. The substrate 10 may also be formed into a rectangular parallelepiped shape by, for example, cutting. An opening 11 is formed in the substrate 10 and passes through in the Z-axis direction. The opening 11 is also referred to as a cavity. When viewed in the Z-axis direction, the opening 11 is, for example, rectangular. The shape of the opening 11 is not limited to a rectangle, and may be other shapes. The substrate 10 has a first surface 10a and a second surface that are opposite to each other in the Z-axis direction. The first surface 10a is a surface on the side of the diaphragm 20 in the Z-axis direction.

[0031] [Diaphragm 20]

[0032] The diaphragm 20 is conductive and is arranged to cover the opening 11. The diaphragm 20 is a conductive polysilicon thin film. The diaphragm 20 is a vibrating electrode plate. The thickness direction of the diaphragm 20 is along the Z-axis direction. The diaphragm 20 has a movable film 21 and a fixed film 22. The movable film 21 is arranged in a manner to cover the opening 11 in the Z-axis direction. Figure 2 As shown, the movable film 21 includes a main body portion 21 a having a substantially rectangular shape and a protruding portion 21 b protruding outward from a corner of the main body portion 21 a .

[0033] The main body 21a is arranged to overlap with the opening 11 when viewed in the Z-axis direction. The protrusion 21b is arranged to overlap with the first surface 10a of the substrate 10 when viewed in the Z-axis direction. The protrusion 21b is fixed to the first surface 10a of the substrate 10. The protrusion 21b may be fixed to the substrate 10 via a support member 50 arranged between the protrusion 21b and the first surface 10a of the substrate 10 in the Z-axis direction. The main body 21a is a portion that can vibrate in the Z-axis direction.

[0034] [Fixed film 22]

[0035] The fixed film 22 is arranged around the movable film 21 when viewed in the Z-axis direction. The fixed film 22 is formed to surround the movable film 21. The fixed film 22 is arranged to overlap the first surface 10a of the substrate 10 when viewed in the Z-axis direction. The fixed film 22 is fixed to the first surface 10a of the substrate 10 via the support member 50.

[0036] [Slit 23]

[0037] In the X-axis direction and the Y-axis direction, a slit 23 is formed between the movable film 21 and the fixed film 22. The slit 23 is a portion where the diaphragm 20 does not exist. The slit 23 is formed to surround the movable film 21. The width of the slit 23 crossing the longitudinal direction can be, for example, 0.38 μm. The slit 23 is formed to penetrate the diaphragm 20 in the Z-axis direction. The slit 23 can be formed by etching a polysilicon film. As a result, the movable film 21 and the fixed film 22 are divided.

[0038] [Back panel 30]

[0039] The back plate 30 is arranged on the side opposite to the substrate 10 with respect to the diaphragm 20 in the Z-axis direction. The plate thickness direction of the back plate 30 is along the Z-axis direction. The back plate 30 is arranged to be separated from the diaphragm 20 in the Z-axis direction. A predetermined space is formed between the diaphragm 20 and the back plate 30. When viewed along the Z-axis direction, the back plate 30 is arranged to cover the opening of the substrate 10.

[0040] The back plate 30 is formed with a plurality of holes 31 penetrating in the Z-axis direction. The plurality of holes 31 are arranged at predetermined intervals in the X-axis direction and the Y-axis direction. The plurality of holes 31 are acoustic holes (sound holes) for allowing sound vibration to pass through. The back plate 30 has a first surface 30a and a second surface 30b that are opposite to each other in the Z-axis direction. The first surface 30a is a surface on the diaphragm 20 side, and the second surface 30b is a surface on the side opposite to the diaphragm 20.

[0041] The periphery of the back plate 30 is arranged at a position overlapping the first surface 10a of the substrate 10 when viewed in the Z-axis direction. The periphery of the back plate 30 is arranged outside the diaphragm 20 in the X-axis direction and the Y-axis direction and is fixed to the first surface 10a of the substrate 10.

[0042] [Fixed electrode 40]

[0043] The fixed electrode 40 is formed on the first surface 30a of the back plate 30. The fixed electrode 40 is arranged to face the main body 21a of the movable film 21 of the diaphragm 20 in the Z-axis direction. The fixed electrode 40 is arranged inside the slit 23 in the X-axis direction and the Y-axis direction. When viewed along the Z-axis direction, the fixed electrode 40 is arranged at a position overlapping with the opening 11 of the substrate 10.

[0044] [Electrostatic capacitance C]

[0045] The diaphragm 20 and the fixed electrode 40 are arranged separately in the Z-axis direction and function as parallel plates. The main body 21a of the movable film 21 of the diaphragm 20 is a movable electrode, and is displaced in the Z-axis direction by the action of sound pressure. As a result, the electrostatic capacitance C between the diaphragm 20 and the fixed electrode 40 changes. In the MEMS microphone 100, sound can be sensed by converting the change in the electrostatic capacitance C into a voltage.

[0046] [Frequency characteristics]

[0047] The main characteristic of a microphone is the sensor's responsiveness to the frequency of sound. This is called "frequency characteristic". In a microphone, the sensitivity of a signal in the range of, for example, 10 Hz to 100 Hz is intentionally reduced in order to reduce wind noise and ambient sound. The frequency characteristic is achieved by forming an opening in a portion of the diaphragm 20.

[0048] [Opening 70 for frequency characteristic adjustment]

[0049] like Figure 2 as well as Figure 3 As shown, an opening 70 for adjusting the frequency characteristics is provided in the fixed film 22. Hereinafter, the "opening 70 for adjusting the frequency characteristics" is sometimes abbreviated as "opening 70". The opening 70 penetrates the fixed film 22 in the Z-axis direction. The shape of the opening 70 is, for example, circular. The shape of the opening 70 is not limited to a circle, and may be an ellipse, a rectangle, a triangle, or other shapes. The inner diameter of the opening 70 may be, for example, greater than 1 μm and less than 30 μm.

[0050] A plurality of openings 70 may be formed in the fixed membrane 22. In the MEMS microphone 100, for example, a total of four openings 70 may be formed. The plurality of openings 70 may be formed at two locations on both sides of the movable membrane 21 in the X-axis direction and at two locations on both sides of the movable membrane 21 in the Y-axis direction. The position and number of the openings 70 are not limited thereto.

[0051] The opening 70 is formed at a position overlapping with the hole 31 of the back plate 30 when viewed in the Z-axis direction. For example, the center 70a of the opening 70 is arranged at a position overlapping with the hole 31. The hole 31 is formed above the opening 70 in the Z-axis direction.

[0052] The opening 70 is formed in a region R2 that is outside the outer periphery 40a of the fixed electrode 40. The region R2 is formed outside the region R1. The region R1 is a region where the diaphragm 20 and the fixed electrode 40 are opposed to each other. The region R1 is formed inside the outer periphery 40a of the fixed electrode 40. The outer periphery 40a of the fixed electrode 40 may also be the outermost edge portion. When viewed along the Z-axis direction, the opening 70 is arranged at a position overlapping with the region R2.

[0053] [Operation and Effect of MEMS Microphone 100 of First Embodiment]

[0054] The MEMS microphone 100 of the first embodiment includes a substrate 10 having an opening 11 , a diaphragm 20 arranged to cover the opening 11 , and a fixed electrode 40 facing the diaphragm 20 and having an opening 70 for adjusting frequency characteristics formed in a region R2 outside the outer periphery of the fixed electrode 40 .

[0055] According to such MEMS microphone 100, the frequency characteristics can be improved by forming opening 70, and the sensitivity to sound of a frequency band that is inaudible to humans can be reduced. In MEMS microphone 100, the sensitivity to wind noise and environmental sound can be intentionally reduced.

[0056] In addition, in the MEMS microphone 100, the opening 70 is formed in the region R2, so that the intrusion of foreign matter between the diaphragm 20 and the fixed electrode 40 can be suppressed. In the MEMS microphone 100, the intrusion of foreign matter between the diaphragm 20 and the fixed electrode 40 is suppressed, so the concern of short circuit between the two electrodes of the diaphragm 20 and the fixed electrode 40 is reduced. As a result, the reliability of the MEMS microphone 100 can be improved. When the foreign matter is a conductor, there is a concern of short circuit, but in the MEMS microphone 100, the concern of foreign matter intrusion is low, and the concern of short circuit is reduced.

[0057] Furthermore, in the MEMS microphone 100 , the fixed electrode 40 is not formed at a position facing the opening 70 . Therefore, even if foreign matter enters through the opening 70 , the possibility of the foreign matter coming into contact with the fixed electrode 40 is reduced.

[0058] If foreign matter is sandwiched between the diaphragm 20 and the fixed electrode 40, the displacement of the diaphragm 20 is suppressed. However, in the MEMS microphone 100, the invasion of foreign matter into the space between the diaphragm 20 and the fixed electrode 40 is suppressed, so the displacement of the diaphragm 20 is difficult to be suppressed. As a result, the sensitivity of the MEMS microphone 100 is suppressed from decreasing.

[0059] In addition, in the MEMS microphone 100, the opening 70 for adjusting the frequency characteristics is provided in the diaphragm 20. In such a MEMS microphone 100, it is sufficient only to provide the opening 70 in the diaphragm 20, and the manufacturing is easy, and the frequency characteristics can be adjusted with a simple structure.

[0060] In addition, the MEMS microphone 100 is provided with a plurality of openings 70 for adjusting the frequency characteristics. In the MEMS microphone 100, the inner diameter of one opening 70 can be reduced. Thus, the frequency characteristics can be adjusted while suppressing a decrease in the strength of the diaphragm 20.

[0061] In the MEMS microphone 100, the diaphragm 20 includes a movable film 21 capable of vibrating in the Z-axis direction and a fixed film 22 disposed around the movable film 21 and fixed to the substrate 10. The fixed film 22 is provided with an opening 70 for adjusting the frequency characteristics.

[0062] In such a MEMS microphone 100, a fixed membrane 22 is formed around a movable membrane 21, and a slit 23 is formed between the movable membrane 21 and the fixed membrane 22. According to the MEMS microphone 100 of this structure, acoustic resistance can be ensured, and a sound pressure difference can be provided between both surfaces of the diaphragm 20. The both surfaces of the diaphragm 20 are two surfaces facing each other in the thickness direction, and are the surface on the opening 11 side of the substrate 10 and the surface on the fixed electrode 40 side.

[0063] In addition, since the opening 70 is formed in the fixed film 22, it is not necessary to form an opening in the movable film 21. Therefore, the frequency characteristics can be adjusted while suppressing the reduction in the strength of the movable film 21. In addition, when the opening is formed in the movable film 21, there is a concern that the movable film 21 may be deformed, such as warping, but in the MEMS microphone 100, the opening 70 is formed in the fixed film 22, thereby reducing the concern that the movable film 21 may be deformed, such as warping.

[0064] In addition, the MEMS microphone 100 includes a back plate 30 fixed to the substrate 10. The fixed electrode 40 is formed on the first surface 30a of the back plate 30 that is opposite to the diaphragm 20, and a plurality of holes 31 penetrating in the Z-axis direction are formed in the back plate 30, and the area of ​​the opening 70 for adjusting the frequency characteristics is smaller than the area of ​​the plurality of holes 31. The inner diameter ID31 of one hole 31 is larger than the inner diameter ID70 of one opening 70.

[0065] In the MEMS microphone 100 of this structure, the inner diameter ID31 of the hole 31 formed in the back plate 30 is larger than the inner diameter ID70 of the opening 70 for adjusting the frequency characteristics, so foreign matter that enters through the opening 70 is easily discharged to the outside through the hole 31. As a result, the concern about the presence of foreign matter between the back plate 30 and the diaphragm 20 is reduced.

[0066] In addition, in the MEMS microphone 100, the hole 31 is formed at a position overlapping with the opening 70 when viewed in the Z-axis direction. Thus, foreign matter that has passed through the opening 70 directly travels and is easily discharged to the outside of the back plate 30 through the hole 31. Therefore, foreign matter is less likely to be retained between the diaphragm 20 and the back plate 30.

[0067] [MEMS Microphone 100 of Second Embodiment]

[0068] Next, a MEMS microphone 100 according to a second embodiment will be described. Figure 4 FIG. 1 is a top view showing a portion of a diaphragm 20B of a MEMS microphone 100 according to a second embodiment. The MEMS microphone 100 according to the second embodiment differs from the MEMS microphone 100 according to the first embodiment in that the arrangement and shape of an opening 70B for adjusting the frequency characteristics are different. In the description of the second embodiment, the same description as that of the first embodiment may be omitted.

[0069] The MEMS microphone 100 of the second embodiment includes a diaphragm 20B. The diaphragm 20B includes a movable membrane 21 and a fixed membrane 22. An opening 70B for adjusting the frequency characteristics is formed in the fixed membrane 22. The opening 70B is formed in a semicircular shape. The shape of the opening 70B is not limited to a semicircular shape, and may be a rectangular shape, a semi-elliptical shape, a substantially circular shape, or other shapes.

[0070] The opening 70B is connected to the slit 23. The opening 70B is formed to extend from the slit 23 to the side opposite to the movable film 21. The slit 23 may include the opening 70B. The width of the slit 23 may include different portions in the length direction of the slit 23. The width of the slit 23 is along the X-axis direction, for example. The length direction of the slit 23 is along the Y-axis direction, for example.

[0071] [Operation and Effect of MEMS Microphone 100 of Second Embodiment]

[0072] The MEMS microphone 100 of the second embodiment has the same effects as the MEMS microphone 100 of the first embodiment. The opening 70B for adjusting the frequency characteristics may be formed to communicate with the slit 23. According to the MEMS microphone 100 of this structure, the minimum width of the fixed membrane 22 can be increased. Thus, it is possible to suppress the reduction in the strength of the fixed membrane 22. According to the MEMS microphone 100 of the second embodiment, the minimum width of the fixed membrane 22 can be increased compared to the structure in which the opening 70 is formed at the center of the width direction of the fixed membrane 22.

[0073] [MEMS Microphone 100 of Third Embodiment]

[0074] Next, a MEMS microphone 100 according to a third embodiment will be described. Figure 5 FIG. 1 is a top view showing a portion of a diaphragm 20C of a MEMS microphone 100 according to a third embodiment. The MEMS microphone 100 according to the third embodiment differs from the MEMS microphone 100 according to the second embodiment in that an opening 70C for adjusting the frequency characteristics is arranged and shaped differently. In the description of the third embodiment, the same description as that of the first and second embodiments may be omitted.

[0075] The MEMS microphone 100 of the third embodiment includes a diaphragm 20C. The diaphragm 20C includes a movable film 21 and a fixed film 22. An opening 70C for adjusting the frequency characteristics is formed in the movable film 21. The opening 70C is formed in a semicircular shape.

[0076] The opening 70C communicates with the slit 23. The opening 70C is formed to extend from the slit 23 to the side opposite to the fixed film 22. The slit 23 may include the opening 70C. The edge of the movable film 21 is formed to be recessed inward. The opening 70C may also be formed in this way.

[0077] [Operation and Effects of MEMS Microphone 100 According to Third Embodiment]

[0078] The MEMS microphone 100 of the third embodiment has the same operational effects as the MEMS microphone 100 of the first embodiment. The frequency characteristic adjustment opening 70C may be formed to communicate with the slit 23 .

[0079] In addition, in the MEMS microphone 100, the opening 70C for adjusting the frequency characteristics is provided in the movable membrane 21. In the MEMS microphone 100 of this structure, the opening 70C may not be provided in the fixed membrane 22, so that the strength reduction of the fixed membrane 22 can be suppressed. In addition, by arranging the opening 70C for adjusting the frequency characteristics further inside the opening 11, even if the size of the opening 11 varies, the relationship in which the opening 70C for adjusting the frequency characteristics and the opening 11 are opposed can be maintained, and the variation of the frequency characteristics can be suppressed.

[0080] The opening 70C for adjusting the frequency characteristics formed in the movable membrane 21 may not be connected to the slit 23. The opening 70C only needs to be formed in the region R2 of the diaphragm 20 that is outside the outer periphery 40a of the fixed electrode 40. In the MEMS microphone 100, the opening 70B may be formed in the fixed membrane 22, and the opening 70C may be formed in the movable membrane 21.

[0081] [MEMS Microphone 100D of Fourth Embodiment]

[0082] Next, a MEMS microphone 100D according to a fourth embodiment will be described. Figure 6 1 is a plan view showing a diaphragm 20D of a MEMS microphone 100D according to a fourth embodiment. Figure 7 It means along Figure 6 Cross-sectional view of the cutting surface along line VII-VII. Figure 8 It means along Figure 6 The MEMS microphone 100D of the fourth embodiment is different from the MEMS microphone 100 of the first embodiment in that the opening 70D for adjusting the frequency characteristics is arranged and shaped differently. In the description of the fourth embodiment, the same description as that of the first to third embodiments is sometimes omitted.

[0083] like Figure 6 to Figure 8 As shown, the MEMS microphone 100D includes a diaphragm 20D. The diaphragm 20D includes a movable film 21 and a fixed film 22. The diaphragm 20D does not have an opening 70D for adjusting the frequency characteristics.

[0084] In the MEMS microphone 100D, an opening 70D for adjusting the frequency characteristics is formed in a region R2 outside the outer periphery 40a of the fixed electrode 40 as viewed in the Z-axis direction. The opening 70D is formed to penetrate the support member 50 in the X-axis direction. Figure 8 As shown, the opening 70D is formed between the diaphragm 20D and the first surface 10a of the substrate 10 in the Z-axis direction. The opening 70D is formed at a position opposite to the first surface 10a of the substrate 10 in the Z-axis direction. In other words, the opening 70D is not in contact with the opening 11 in the Z-axis direction.

[0085] The opening 70D may be formed between a plurality of support members 50. A plurality of openings 70D may be formed in the support member 50. In addition, for example, a recess may be formed on the upper surface or the lower surface of the support member 50 to form the opening 70D penetrating the width direction of the support member 50.

[0086] like Figure 7 as well as Figure 8 As shown, in the X-axis direction, a gap 72 is formed between the diaphragm 20D and the back plate 30. The gap 72 communicates with the opening 70D.

[0087] [Functions and Effects of MEMS Microphone 100D of Fourth Embodiment]

[0088] The MEMS microphone 100D of the fourth embodiment has the same operational effects as the MEMS microphone 100 of the first embodiment. The opening 70D for adjusting the frequency characteristics may be formed in the support member 50 .

[0089] The MEMS microphone 100D includes a support member 50, which is disposed between the substrate 10 and the diaphragm 20D in the Z-axis direction (first direction), is disposed so as to surround the opening 11 of the substrate 10 when viewed in the Z-axis direction, and supports the diaphragm 20D. The opening 70D for adjusting the frequency characteristics penetrates the support member 50 in the X-axis direction (a second direction intersecting the first direction).

[0090] According to the MEMS microphone 100D of this structure, the opening 70D penetrating in the X-axis direction can reduce the possibility of foreign matter entering through the opening 11 entering the opening 70D. Therefore, the possibility of foreign matter entering between the diaphragm 20 and the fixed electrode 40 through the opening 70D and the gap 72 is suppressed.

[0091] In the MEMS microphone 100D, the opening 70D for adjusting the frequency characteristics is provided at a position facing the substrate 10 in the Z-axis direction. Thus, for example, foreign matter that has passed through the opening 11 in the Z-axis direction hits the diaphragm 20D and is unlikely to enter between the diaphragm 20D and the fixed electrode 40. According to the MEMS microphone 100D, the entry of foreign matter into between the diaphragm 20D and the fixed electrode 40 can be suppressed.

[0092] [MEMS Microphone 100E of Fifth Embodiment]

[0093] Next, a MEMS microphone 100E according to a fifth embodiment will be described. Fig. 9 1 is a plan view showing a diaphragm 20E of a MEMS microphone 100E according to a fifth embodiment. Fig.10 It means along Fig. 9 The MEMS microphone 100E of the fifth embodiment is different from the MEMS microphone 100 of the first embodiment in that the frequency characteristic adjustment opening 70E is arranged differently. In the description of the fifth embodiment, the same description as the first to fourth embodiments may be omitted.

[0094] The MEMS microphone 100E includes a diaphragm 20E. The diaphragm 20E includes a movable film 21 and a fixed film 22. An opening 70E for adjusting the frequency characteristics is formed in the fixed film 22. The opening 70E is formed to be opposite to the first surface 10a of the substrate 10 in the Z-axis direction. The opening 70E is not in contact with the opening 11 in the Z-axis direction. The opening 70E is arranged outside the peripheral edge 11a of the opening 11 in the X-axis direction. The peripheral edge 11a may also be an end of the first surface 10a of the substrate 10 on the side of the opening 11. Fig. 9 In FIG. 1 , a periphery 11 a of the opening 11 of the substrate 10 is indicated by a dotted line.

[0095] like Fig.10 As shown, in the Z-axis direction, a gap 74 is formed between the diaphragm 20E and the first surface 10a of the substrate 10. The gap 74 is formed in the Z-axis direction between the support member 50 and the peripheral edge 11a of the opening 11. The opening 70E for frequency characteristic adjustment communicates with the gap 74 and the opening 11.

[0096] The opening width D74 of the gap 74 may be, for example, 2 μm or less. The opening width D74 is the opening width of the gap 74 along the Z-axis direction, and may be the length between the first surface 10a of the substrate 10 and the diaphragm 20E. The acoustic impedance that determines the frequency characteristics of the MEMS microphone 100E may be a composite resistance of the acoustic impedance based on the opening 70D and the acoustic impedance based on the gap 74.

[0097] [Functions and Effects of MEMS Microphone 100E of Fifth Embodiment]

[0098] The MEMS microphone 100E of the fifth embodiment has the same effects as the MEMS microphone 100 of the first embodiment. The opening 70E for adjusting the frequency characteristics may be arranged to face the first surface 10a of the substrate 10 in the Z-axis direction. As a result, foreign matter is unlikely to enter the opening 70E. Therefore, it is possible to suppress the intrusion of foreign matter between the diaphragm 20E and the fixed electrode 40.

[0099] [Positional Relationship Between the Opening 70 for Adjusting Frequency Characteristics and the Opening 11 of the Substrate 10]

[0100] like Figure 3As shown, the opening 70 for adjusting the frequency characteristics may be arranged so as to overlap with the opening 11 of the substrate 10 when viewed in the Z-axis direction. In the MEMS microphone 100 having this structure, the acoustic impedance that determines the frequency characteristics is determined only by the acoustic impedance of the opening 70 formed in the fixed film 22. Therefore, the frequency characteristics (manufacturing variations) have less variations than the MEMS microphone 100E of the fifth embodiment.

[0101] [Modifications]

[0102] In the MEMS microphone 100 of the modified example, the inner diameter of the hole 31 formed outside the region R1 may be larger than the inner diameter of the hole 31 formed in the region R1. The inner diameter of the hole 31 arranged at a position overlapping with the opening 70 for adjusting the frequency characteristics when viewed in the Z-axis direction may be larger than the inner diameter of the hole 31 formed in the region R1.

[0103] In addition, other embodiments of the invention may be combined with other structural elements in the structures listed in the above embodiments, and the invention is not limited to the structures shown here. In this regard, changes can be made within the scope of the gist of the invention and can be appropriately determined according to its application.

Claims

1. A sound conversion device, characterized in that: have: a substrate having an opening; a diaphragm configured to cover the opening; and a fixed electrode, which is opposite to the diaphragm, An opening for adjusting frequency characteristics is formed in a region outside the outer circumference of the fixed electrode.

2. The sound conversion device according to claim 1, characterized in that: The frequency characteristic adjustment opening is provided in the diaphragm.

3. The sound conversion device according to claim 1, characterized in that: A plurality of openings for adjusting the frequency characteristics are provided.

4. The sound conversion device according to claim 2, characterized in that: The diaphragm includes: a movable film that can vibrate in a first direction that is a thickness direction of the substrate; and a fixed film that is arranged around the movable film and fixed to the substrate. The opening for adjusting the frequency characteristics is provided in the movable film.

5. The sound conversion device according to claim 4, characterized in that: The frequency characteristic adjustment opening is provided at a position facing the opening of the substrate.

6. The sound conversion device according to claim 2, characterized in that: The diaphragm includes: a movable film that can vibrate in a first direction that is a thickness direction of the substrate; and a fixed film that is arranged around the movable film and fixed to the substrate. The opening for adjusting the frequency characteristics is provided in the fixed film.

7. The sound conversion device according to claim 6, characterized in that: The frequency characteristic adjustment opening is provided at a position facing the substrate.

8. The sound conversion device according to claim 1, characterized in that: A supporting member is provided, the supporting member being arranged between the substrate and the diaphragm, being arranged so as to surround the opening of the substrate, and supporting the diaphragm, The frequency characteristic adjustment opening passes through the supporting member.

9. The sound conversion device according to claim 1, characterized in that: A back plate fixed to the substrate is provided, The fixed electrode is formed on a surface of the back plate that is opposite to the diaphragm. The back plate is formed with a plurality of holes penetrating in the plate thickness direction. The area of ​​the opening for adjusting the frequency characteristics is smaller than the area of ​​the plurality of holes.

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