Sound conversion device

Abstract

To prevent foreign matter from entering between a diaphragm and a fixed electrode.SOLUTION: An MEMS microphone 100 includes a substrate 10 having an opening penetrating in a first direction which is the plate thickness direction, a conductive diaphragm 20 arranged to cover the opening 11, and a fixed electrode 40 opposed to the diaphragm 20, and an opening 70 for adjusting the frequency characteristics is formed outside the outer periphery of the fixed electrode 40.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to an acoustic transducer. [Background technology]

[0002] For example, a microphone is known that includes a substrate having an opening, a vibrating electrode plate formed to cover the opening, a back plate formed to cover the vibrating electrode plate, and a fixed electrode plate provided on the back plate (see, for example, Patent Document 1). In the microphone described in Patent Document 1, a plurality of holes are provided in the center of the vibrating electrode plate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6127595 Summary of the Invention [Problem to be solved by the invention]

[0004] In microphones relating to conventional technology, there was a risk that foreign matter that entered through an opening in the substrate would pass through multiple holes provided in the center of the vibrating electrode plate and enter between the vibrating electrode plate (diaphragm) and the fixed electrode plate.

[0005] An object of the present disclosure is to provide an acoustic transducer capable of suppressing the intrusion of foreign matter between a diaphragm and a fixed electrode. [Means for solving the problem]

[0006] An acoustic transducer according to one aspect of the present disclosure comprises a substrate having an opening, a diaphragm arranged to cover the opening, and a fixed electrode facing the diaphragm, and an opening for adjusting frequency characteristics is formed in an area outside the outer periphery of the fixed electrode. Effect of the Invention

[0007] The present disclosure can provide an acoustic transducer capable of suppressing the intrusion of foreign matter between a diaphragm and a fixed electrode. [Brief description of the drawings]

[0008] [Figure 1] 1 is an exploded perspective view showing a MEMS microphone according to a first embodiment. [Diagram 2] FIG. [Diagram 3] 3 is a cross-sectional view showing a section taken along line III-III in FIG. 2. [Figure 4] FIG. 11 is a plan view showing a diaphragm portion of a MEMS microphone according to a second embodiment. [Diagram 5] FIG. 11 is a plan view showing a diaphragm portion of a MEMS microphone according to a third embodiment. [Figure 6] FIG. 13 is a plan view showing a diaphragm of a MEMS microphone according to a fourth embodiment. [Figure 7] 7 is a cross-sectional view showing a cut surface along the line VII-VII in FIG. 6. [Figure 8] 8 is a cross-sectional view showing a section taken along line VIII-VIII in FIG. 6. [Figure 9] FIG. 13 is a partial plan view showing a diaphragm of a MEMS microphone according to a fifth embodiment. [Figure 10] 10 is a cross-sectional view showing a cut surface along the line XX in FIG. 9. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an acoustic transducer according to an embodiment will be described with reference to the accompanying drawings. In this specification and the drawings, substantially identical components are designated by the same reference numerals, and redundant description may be omitted.

[0010] [MEMS microphone 100 according to the first embodiment] The MEMS microphone 100 according to the first embodiment will be described with reference to Figs. 1 to 3. Fig. 1 is an exploded perspective view showing the MEMS microphone 100 according to the first embodiment. Fig. 2 is a plan view showing the diaphragm 20. Fig. 3 is a cross-sectional view showing a cut surface along line III-III in Fig. 2. In each drawing, three orthogonal directions, 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 the following description, the terms "upper" and "lower" may be used, but the arrangement of the MEMS microphone 100 is not limited to this.

[0011] As shown in Fig. 1, 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 an "acoustic transducer". The MEMS microphone 100 is a capacitive element manufactured using MEMS technology. "MEMS" is an abbreviation for Micro Electro Mechanical System. The acoustic transducer is not limited to the MEMS microphone 100, and may be another acoustic sensor or a speaker.

[0012] [Substrate 10] The substrate 10 is made of, for example, single crystal silicon. The substrate 10 may be formed into a rectangular parallelepiped shape by, for example, dicing. An opening 11 is formed in the substrate 10 penetrating in the Z-axis direction. The opening 11 is also called a cavity. When viewed in the Z-axis direction, the opening 11 has, for example, a rectangular shape. The shape of the opening 11 is not limited to a rectangular shape, and may be other shapes. The substrate 10 has a first surface 10a and a second surface facing each other in the Z-axis direction. The first surface 10a is the surface on the diaphragm 20 side in the Z-axis direction.

[0013] [Diaphragm 20] The diaphragm 20 is conductive and 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 to cover the opening 11 in the Z-axis direction. As shown in FIG. 2, the movable film 21 includes a main body portion 21a having a substantially rectangular shape and a protrusion portion 21b protruding outward from a corner of the main body portion 21a.

[0014] The main body 21a is disposed so as to overlap the opening 11 when viewed in the Z-axis direction. The protruding portion 21b is disposed so as to overlap the first surface 10a of the substrate 10 when viewed in the Z-axis direction. The protruding portion 21b is fixed to the first surface 10a of the substrate 10. The protruding portion 21b may be fixed to the substrate 10 via a support member 50 disposed between the protruding portion 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.

[0015] [Fixed membrane 22] The fixed film 22 is disposed around the movable film 21 when viewed in the Z-axis direction. The fixed film 22 is formed so as to surround the movable film 21. The fixed film 22 is disposed so as 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 a support member 50.

[0016] [Slit 23] A slit 23 is formed between the movable film 21 and the fixed film 22 in the X-axis direction and the Y-axis direction. The slit 23 is a portion where the diaphragm 20 does not exist. The slit 23 is formed so as to surround the movable film 21. The width of the slit 23 intersecting the longitudinal direction may be, for example, 0.38 μm. The slit 23 is formed so as to penetrate the diaphragm 20 in the Z-axis direction. The slit 23 can be formed by etching a single polysilicon film. This separates the movable film 21 and the fixed film 22.

[0017] [Backplate 30] The backplate 30 is disposed on the opposite side of the diaphragm 20 from the substrate 10 in the Z-axis direction. The plate thickness direction of the backplate 30 is along the Z-axis direction. The backplate 30 is disposed away from the diaphragm 20 in the Z-axis direction. A predetermined space is formed between the diaphragm 20 and the backplate 30. The backplate 30 is disposed so as to cover the opening of the substrate 10 when viewed in the Z-axis direction.

[0018] The back plate 30 has a plurality of holes 31 formed therethrough in the Z-axis direction. The holes 31 are arranged at predetermined intervals in the X-axis direction and the Y-axis direction. The holes 31 are acoustic holes for passing acoustic vibrations. The back plate 30 has a first surface 30a and a second surface 30b facing each other in the Z-axis direction. The first surface 30a is the surface on the diaphragm 20 side, and the second surface 30b is the surface opposite the diaphragm 20.

[0019] The peripheral portion of the backplate 30 is disposed at a position overlapping the first surface 10a of the substrate 10 when viewed in the Z-axis direction. The peripheral portion of the backplate 30 is disposed 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.

[0020] [Fixed electrode 40] The fixed electrode 40 is formed on the first surface 30a of the back plate 30. The fixed electrode 40 is disposed so as to face the main body portion 21a of the movable film 21 of the diaphragm 20 in the Z-axis direction. The fixed electrode 40 is disposed on the inside of the slits 23 in the X-axis and Y-axis directions. The fixed electrode 40 is disposed at a position overlapping with the opening 11 of the substrate 10 when viewed in the Z-axis direction.

[0021] [Capacitance C] The diaphragm 20 and the fixed electrode 40 are disposed apart 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 when sound pressure acts on it. This causes a change in capacitance C between the diaphragm 20 and the fixed electrode 40. The MEMS microphone 100 can sense sound by converting the change in capacitance C into a voltage.

[0022] [Frequency characteristics] The main characteristic of a microphone is the responsiveness of the sensor to sound frequency. This is called the "frequency characteristic." In some microphones, the sensitivity is intentionally lowered, for example, in the range of 10 Hz to 100 Hz, in order to reduce wind noise and environmental noise. The frequency characteristic is achieved by forming an opening in a part of the diaphragm 20.

[0023] [Aperture for frequency response adjustment 70] As shown in Figs. 2 and 3, the fixed film 22 is provided with an opening 70 for adjusting frequency characteristics. Hereinafter, the "opening 70 for adjusting frequency characteristics" may be abbreviated to "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 circular, and may be elliptical, rectangular, triangular, or another shape. The inner diameter of the opening 70 may be, for example, 1 µm or more and 30 µm or less.

[0024] A plurality of openings 70 may be formed in the fixed film 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 in two locations on both sides in the X-axis direction and two locations on both sides in the Y-axis direction with respect to the movable film 21. The positions and number of the openings 70 are not limited thereto.

[0025] When viewed in the Z-axis direction, the opening 70 is formed at a position overlapping with the hole 31 of the back plate 30. For example, the center 70a of the opening 70 is disposed at a position overlapping with the hole 31. The hole 31 is formed above the opening 70 in the Z-axis direction.

[0026] The opening 70 is formed in region R2, which is outside the outer periphery 40a of the fixed electrode 40. Region R2 is formed outside region R1. Region R1 is the region where the diaphragm 20 and the fixed electrode 40 face each other. Region R1 is formed inside the outer periphery 40a of the fixed electrode 40. The outer periphery 40a of the fixed electrode 40 may be the outermost edge. The opening 70 is disposed at a position overlapping region R2 when viewed in the Z-axis direction.

[0027] [Actions and Effects of the MEMS Microphone 100 According to the First Embodiment] The MEMS microphone 100 of the first embodiment comprises 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 an opening 70 for adjusting frequency characteristics is formed in a region R2 outside the outer periphery of the fixed electrode 40.

[0028] According to the MEMS microphone 100, the opening 70 can improve the frequency characteristics and reduce the sensitivity to sounds in the frequency band that humans cannot hear. The MEMS microphone 100 can intentionally reduce the sensitivity to wind noise and environmental sounds.

[0029] Furthermore, in the MEMS microphone 100, the opening 70 is formed in the region R2, thereby making it possible to prevent foreign matter from entering between the diaphragm 20 and the fixed electrode 40. In the MEMS microphone 100, the intrusion of foreign matter between the diaphragm 20 and the fixed electrode 40 is prevented, thereby reducing the risk of a short circuit occurring between the two electrodes, the diaphragm 20 and the fixed electrode 40. As a result, the reliability of the MEMS microphone 100 can be improved. If the foreign matter is a conductor, there is a risk of a short circuit, but in the MEMS microphone 100, the risk of foreign matter entering is low, and the risk of a short circuit occurring is reduced.

[0030] In addition, in the MEMS microphone 100, the fixed electrode 40 is not formed in a position opposite the opening 70, so even if a foreign object enters through the opening 70, the risk of the foreign object coming into contact with the fixed electrode 40 is reduced.

[0031] If a foreign object is caught between the diaphragm 20 and the fixed electrode 40, the displacement of the diaphragm 20 is suppressed, but in the MEMS microphone 100, the intrusion of foreign objects between the diaphragm 20 and the fixed electrode 40 is suppressed, so the displacement of the diaphragm 20 is less suppressed. As a result, the decrease in sensitivity in the MEMS microphone 100 is suppressed.

[0032] Furthermore, 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 only necessary to provide the opening 70 in the diaphragm 20, so that the manufacture is easy and the frequency characteristics can be adjusted with a simple configuration.

[0033] Furthermore, the MEMS microphone 100 is provided with a plurality of openings 70 for adjusting frequency characteristics. The inner diameter of each opening 70 can be reduced in the MEMS microphone 100. This makes it possible to adjust the frequency characteristics while suppressing a decrease in the strength of the diaphragm 20.

[0034] In the MEMS microphone 100, the diaphragm 20 has a movable film 21 that can vibrate in the Z-axis direction, and a fixed film 22 that is disposed around the movable film 21 and fixed to the substrate 10. An opening 70 for adjusting frequency characteristics is provided in the fixed film 22.

[0035] 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 having this structure, it is possible to ensure acoustic resistance and to provide a sound pressure difference between both sides of the diaphragm 20. The two sides of the diaphragm 20 refer to both sides that face each other in the thickness direction, that is, the side on the opening 11 side of the substrate 10 and the side on the fixed electrode 40 side.

[0036] Furthermore, since the opening 70 is formed in the fixed film 22, there is no need to form an opening in the movable film 21. Therefore, it is possible to adjust the frequency characteristics while suppressing a decrease in the strength of the movable film 21. Furthermore, if an opening is formed in the movable film 21, there is a risk of deformation such as warping of the movable film 21. However, in the MEMS microphone 100, by forming the opening 70 in the fixed film 22, the risk of deformation such as warping of the movable film 21 is reduced.

[0037] The MEMS microphone 100 also includes a backplate 30 fixed to the substrate 10. The fixed electrode 40 is formed on a first surface 30a of the backplate 30 facing the diaphragm 20, and the backplate 30 is formed with a plurality of holes 31 penetrating in the Z-axis direction, and the area of ​​an opening 70 for adjusting frequency characteristics is smaller than the area of ​​the plurality of holes 31. An inner diameter ID31 of one hole 31 is larger than an inner diameter ID70 of one opening 70.

[0038] In the MEMS microphone 100 having this configuration, 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 that foreign matter that enters through the opening 70 is easily discharged to the outside through the hole 31. This reduces the risk of foreign matter being present between the back plate 30 and the diaphragm 20.

[0039] Furthermore, in the MEMS microphone 100, a hole 31 is formed at a position overlapping with the opening 70 when viewed in the Z-axis direction. This makes it easier for foreign matter that has passed through the opening 70 to continue traveling and pass through the hole 31, and be discharged to the outside of the back plate 30. Therefore, foreign matter is less likely to remain between the diaphragm 20 and the back plate 30.

[0040] [MEMS microphone 100 according to the second embodiment] Next, a MEMS microphone 100 according to a second embodiment will be described. Fig. 4 is a plan view showing a diaphragm 20B portion of the MEMS microphone 100 according to the 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 the opening 70B for adjusting the frequency characteristics are different. Note that in the description of the second embodiment, the same description as in the first embodiment may be omitted.

[0041] The MEMS microphone 100 according to the second embodiment includes a diaphragm 20B. The diaphragm 20B has a movable film 21 and a fixed film 22. An opening 70B for adjusting frequency characteristics is formed in the fixed film 22. The opening 70B is formed to have a semicircular shape. The shape of the opening 70B is not limited to a semicircular shape, and may be a rectangular shape, a semielliptical shape, a substantially circular shape, or another shape.

[0042] The opening 70B communicates with the slit 23. The opening 70B is formed to protrude from the slit 23 to the opposite side 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 longitudinal direction of the slit 23. The width of the slit 23 is along, for example, the X-axis direction. The longitudinal direction of the slit 23 is along, for example, the Y-axis direction.

[0043] [Actions and effects of the MEMS microphone 100 according to the second embodiment] The MEMS microphone 100 according to the second embodiment has the same effects as the MEMS microphone 100 according to the first embodiment. The opening 70B for adjusting frequency characteristics may be formed so as to communicate with the slit 23. With the MEMS microphone 100 having this configuration, the minimum width of the fixed film 22 can be increased. This makes it possible to suppress a decrease in strength of the fixed film 22. With the MEMS microphone 100 according to the second embodiment, the minimum width of the fixed film 22 can be increased compared to a configuration in which the opening 70 is formed in the center of the fixed film 22 in the width direction.

[0044] [MEMS microphone 100 according to the third embodiment] Next, a MEMS microphone 100 according to a third embodiment will be described. Fig. 5 is a plan view showing a portion of the diaphragm 20C of the MEMS microphone 100 according to the third embodiment. The MEMS microphone 100 according to the third embodiment differs from the MEMS microphone 100 according to the second embodiment in that the arrangement and shape of the opening 70C for adjusting the frequency characteristics are different. Note that in the description of the third embodiment, descriptions similar to those of the first and second embodiments may be omitted.

[0045] The MEMS microphone 100 according to the third embodiment includes a diaphragm 20C. The diaphragm 20C has a movable film 21 and a fixed film 22. An opening 70C for adjusting frequency characteristics is formed in the movable film 21. The opening 70C is formed to have a semicircular shape.

[0046] The opening 70C communicates with the slit 23. The opening 70C is formed so as to protrude from the slit 23 to the opposite side to the fixed film 22. The slit 23 may include the opening 70C. The edge of the movable film 21 is formed so as to be recessed inward. The opening 70C may be formed in this manner.

[0047] [Actions and Effects of the MEMS Microphone 100 According to the Third Embodiment] The MEMS microphone 100 according to the third embodiment has the same effects as the MEMS microphone 100 according to the first embodiment. The opening 70C for adjusting frequency characteristics may be formed so as to communicate with the slit 23.

[0048] Furthermore, in MEMS microphone 100, opening 70C for adjusting frequency characteristics is provided in movable film 21. In MEMS microphone 100 having this configuration, opening 70C does not need to be provided in fixed film 22, which can suppress a decrease in strength of fixed film 22. Furthermore, by locating opening 70C for adjusting frequency characteristics on the inner side of opening 11, even if the dimensions of opening 11 vary, opening 70C for adjusting frequency characteristics and opening 11 can be maintained in an opposing relationship, and variation in frequency characteristics can be suppressed.

[0049] The opening 70C for adjusting frequency characteristics formed in the movable film 21 does not have to be connected to the slit 23. The opening 70C may be formed in the region R2 outside the outer periphery 40a of the diaphragm 20 and the fixed electrode 40. In the MEMS microphone 100, the opening 70B may be formed in the fixed film 22, and the opening 70C may be formed in the movable film 21.

[0050] [MEMS microphone 100D according to the fourth embodiment] Next, a MEMS microphone 100D according to a fourth embodiment will be described. FIG. 6 is a plan view showing a diaphragm 20D of the MEMS microphone 100D according to the fourth embodiment. FIG. 7 is a cross-sectional view showing a cut surface along line VII-VII in FIG. 6. FIG. 8 is a cross-sectional view showing a cut surface along line VIII-VIII in FIG. 6. The MEMS microphone 100D according to the fourth embodiment differs from the MEMS microphone 100 according to the first embodiment in that the arrangement and shape of the opening 70D for adjusting frequency characteristics are different. Note that in the description of the fourth embodiment, the same description as in the first to third embodiments may be omitted.

[0051] 6 to 8, the MEMS microphone 100D includes a diaphragm 20D. The diaphragm 20D has a movable film 21 and a fixed film 22. The diaphragm 20D does not have an opening 70D for adjusting frequency characteristics.

[0052] In the MEMS microphone 100D, an opening 70D for adjusting frequency characteristics is formed in a region R2 outside the outer periphery 40a of the fixed electrode 40 when viewed in the Z-axis direction. The opening 70D is formed so as to penetrate the support member 50 in the X-axis direction. As shown in Fig. 8, 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 facing the first surface 10a of the substrate 10 in the Z-axis direction. In other words, the opening 70D does not contact the opening 11 in the Z-axis direction.

[0053] The opening 70D may be formed between multiple support members 50. Multiple openings 70D may be formed in the support member 50. Also, for example, a recess may be formed in the upper surface or lower surface of the support member 50, thereby forming the opening 70D penetrating the support member 50 in the width direction.

[0054] 7 and 8, 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.

[0055] [Actions and Effects of the MEMS Microphone 1004 According to the Fourth Embodiment] The MEMS microphone 100D according to the fourth embodiment has the same effects as the MEMS microphone 100 according to the first embodiment. The opening 70D for adjusting frequency characteristics may be formed in the support member 50.

[0056] The MEMS microphone 100D includes a support member 50 that is disposed between the substrate 10 and the diaphragm 20D in the Z-axis direction (first direction), that is disposed so as to surround the opening 11 of the diaphragm 20D as viewed in the Z-axis direction, and that supports the diaphragm 20D. An opening 70D for adjusting frequency characteristics penetrates the support member 50 in the X-axis direction (second direction intersecting the first direction).

[0057] According to MEMS microphone 100D having this configuration, opening 70D penetrating in the X-axis direction is formed, which reduces the risk of foreign matter that has entered through opening 11 entering opening 70D. Therefore, the risk of foreign matter passing through opening 70D and further through gap 72 to enter between diaphragm 20 and fixed electrode 40 is reduced.

[0058] In the MEMS microphone 100D, the opening 70D for adjusting frequency characteristics is provided at a position facing the substrate 10 in the Z-axis direction. As a result, for example, foreign matter that passes through the opening 11 in the Z-axis direction hits the diaphragm 20D and is unlikely to penetrate between the diaphragm 20D and the fixed electrode 40. With the MEMS microphone 100D, the intrusion of foreign matter between the diaphragm 20D and the fixed electrode 40 can be suppressed.

[0059] [MEMS microphone 100E according to the fifth embodiment] Next, a MEMS microphone 100E according to a fifth embodiment will be described. Fig. 9 is a plan view showing a diaphragm 20E of the MEMS microphone 100E according to the fifth embodiment. Fig. 10 is a cross-sectional view showing a cut surface along line XX in Fig. 9. The MEMS microphone 100E according to the fifth embodiment differs from the MEMS microphone 100 according to the first embodiment in that the arrangement of the opening 70E for adjusting frequency characteristics is different. Note that in the description of the fifth embodiment, descriptions similar to those of the first to fourth embodiments may be omitted.

[0060] The MEMS microphone 100E includes a diaphragm 20E. The diaphragm 20E has a movable film 21 and a fixed film 22. An opening 70E for adjusting frequency characteristics is formed in the fixed film 22. The opening 70E is formed to face the first surface 10a of the substrate 10 in the Z-axis direction. The opening 70E does not contact the opening 11 in the Z-axis direction. The opening 70E is disposed outside the periphery 11a of the opening 11 in the X-axis direction. The periphery 11a may be an end of the first surface 10a of the substrate 10 on the opening 11 side. In FIG. 9, the periphery 11a of the opening 11 of the substrate 10 is indicated by a dashed line.

[0061] 10, a gap 74 is formed between the diaphragm 20E and the first surface 10a of the substrate 10 in the Z-axis direction. The gap 74 is formed between the support member 50 and the periphery 11a of the opening 11 in the Z-axis direction. The opening 70E for adjusting frequency characteristics communicates with the gap 74 and the opening 11.

[0062] An 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. In the MEMS microphone 100E, the acoustic resistance that determines the frequency characteristics may be a composite resistance of the acoustic resistance due to the opening 70D and the acoustic resistance due to the gap 74.

[0063] [Actions and Effects of the MEMS Microphone 100E According to the Fifth Embodiment] The MEMS microphone 100E according to the fifth embodiment has the same effects as the MEMS microphone 100 according to the first embodiment. The frequency characteristic adjustment opening 70E may be disposed to face the first surface 10a of the substrate 10 in the Z-axis direction. This makes it difficult for foreign matter to enter the opening 70E. Therefore, the intrusion of foreign matter between the diaphragm 20E and the fixed electrode 40 can be suppressed.

[0064] [Positional relationship between frequency characteristic adjustment opening 70 and opening 11 of substrate 10] 3, the opening 70 for adjusting the frequency characteristics may be disposed 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 configuration, the acoustic resistance that determines the frequency characteristics is determined only by the acoustic resistance of the opening 70 formed in the fixed film 22. Therefore, there is less variation in the frequency characteristics (manufacturing variation) compared to the MEMS microphone 100E according to the fifth embodiment described above.

[0065] [Variations] In the MEMS microphone 100 according to 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 within the region R1. The inner diameter of the hole 31 arranged at a position overlapping with the frequency characteristic adjustment opening 70 as viewed in the Z-axis direction may be larger than the inner diameter of the hole 31 formed within the region R1.

[0066] In addition, the present invention is not limited to the configuration shown here, and may be implemented in other embodiments in which other components are combined with the configurations and the like of the above-mentioned embodiment. In this regard, the present invention may be modified within the scope of the gist of the present invention, and may be appropriately determined according to the application form. [Explanation of symbols]

[0067] 100, 100D, 100E...MEMS microphone (acoustic transducer), 10...substrate, 11...opening, 20, 20B, 20C, 20D, 20E...diaphragm, 21...movable membrane, 22...fixed membrane, 23...slit, 30...back plate, 31...multiple holes, 40...fixed electrode, 40a...outer periphery of fixed electrode, 50...support member, 70, 70B, 70C, 70D, 70E...openings for adjusting frequency characteristics, R1...area where diaphragm and fixed electrode face each other, R2...area outside the outer periphery of fixed electrode, X...X-axis direction, Y...Y-axis direction, Z...Z-axis direction (first direction, plate thickness direction).

Claims

1. a substrate having an opening; A diaphragm disposed to cover the opening; a fixed electrode facing the diaphragm, An acoustic transducer, wherein an opening for adjusting frequency characteristics is formed in an area outside the outer periphery of the fixed electrode.

2. The acoustic transducer according to claim 1 , wherein the opening for adjusting the frequency characteristics is provided in the diaphragm.

3. The acoustic transducer according to claim 1 , further comprising a plurality of the frequency characteristic adjusting openings.

4. the diaphragm has a movable film that is vibrable in a first direction that is a thickness direction of the substrate, and a fixed film that is disposed around the movable film and fixed to the substrate, The acoustic transducer according to claim 2 , wherein the opening for adjusting the frequency characteristics is provided in the movable membrane.

5. The acoustic transducer according to claim 4 , wherein the opening for adjusting frequency characteristics is provided at a position opposite to the opening of the substrate.

6. the diaphragm has a movable film that is vibrable in a first direction that is a thickness direction of the substrate, and a fixed film that is disposed around the movable film and fixed to the substrate, The acoustic transducer according to claim 2 , wherein the opening for adjusting the frequency characteristics is provided in the fixed film.

7. The acoustic transducer according to claim 6 , wherein the opening for adjusting frequency characteristics is provided at a position facing the substrate.

8. a support member disposed between the substrate and the diaphragm, the support member being disposed so as to surround the opening of the substrate and supporting the diaphragm; The acoustic transducer according to claim 1 , wherein the opening for adjusting frequency characteristics penetrates the support member.

9. a backplate fixed to the substrate; the fixed electrode is formed on a surface of the back plate facing the diaphragm, The back plate is formed with a plurality of holes penetrating in a plate thickness direction, The acoustic transducer according to claim 1 , wherein an area of ​​the opening for adjusting frequency characteristics is smaller than an area of ​​the plurality of holes.

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