Acoustic conversion device

Abstract

The invention provides an acoustic conversion device, which realizes improvement of sensitivity. An acoustic conversion device (100) is provided with: a fixed frame (10); and a cantilever (20), one end of which is a fixed end (22) fixed to the fixed frame (10) and the other end of which is a free end (21), the cantilever (20) extending from the fixed frame (10) toward the inside of the fixed frame (10), the cantilever (20) having: a plurality of detection regions (23) capable of detecting physical quantities; and a non-detection region (24) in which the physical quantity is not detected. The electrodes of the plurality of detection regions (23) are electrically connected in series.

Description

Technical Field

[0001] The present disclosure relates to an acoustic conversion device. Background Art

[0002] For example, a piezoelectric element is known that includes a piezoelectric film having one end supported and the other end being a free end, and a pair of electrodes arranged with the piezoelectric film interposed therebetween (for example, see Patent Document 1).

[0003] Prior art literature

[0004] Patent Document 1: Japanese Patent Application Laid-Open No. 2019-140638 Summary of the Invention

[0005] An acoustic transducer device having a piezoelectric element is required to have improved sensitivity. An object of the present disclosure is to provide an acoustic transducer device capable of achieving improved sensitivity.

[0006] The first embodiment of the acoustic conversion device disclosed herein comprises: a fixed frame; and a cantilever, one end of which is a fixed end fixed to the fixed frame and the other end is a free end, and extends from the fixed frame toward the inner side of the fixed frame. The cantilever has: a plurality of detection areas capable of detecting physical quantities; and a non-detection area that does not detect physical quantities, and the electrodes of the plurality of detection areas are electrically connected in series.

[0007] The second embodiment of the present disclosure provides an acoustic conversion device comprising: a fixed frame; and a cantilever, one end of which is a fixed end fixed to the fixed frame and the other end is a free end, and extends from the fixed frame toward the inside of the fixed frame, the cantilever having: a detection area capable of detecting physical quantities; and a non-detection area in which physical quantities are not detected.

[0008] The sound conversion device of the third scheme of the present invention comprises: a fixed frame; and a cantilever, one end of which is a fixed end fixed to the fixed frame and the other end is a free end, and extends from the fixed frame to the inner side of the fixed frame, and the cantilever has: a lower electrode; a first piezoelectric layer formed on the lower electrode; an intermediate electrode formed on the first piezoelectric layer; a second piezoelectric layer formed on the intermediate electrode; and an upper electrode formed on the second piezoelectric layer, and the thickness of the intermediate electrode is thicker than the thickness of the upper electrode or the lower electrode.

[0009] The effects of the present invention are as follows.

[0010] The present disclosure can provide an acoustic transducer capable of achieving improved sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a plan view illustrating the acoustic transducer device according to the first embodiment of the first aspect.

[0012] Figure 2This is a cross-sectional view illustrating the acoustic transducer according to the first embodiment of the first aspect, and is a view showing a cross section taken along the XZ plane.

[0013] Figure 3 This is a cross-sectional view illustrating the acoustic transducer according to the first embodiment of the first aspect, and is a view showing a cross section taken along the YZ plane.

[0014] Figure 4 This is a circuit diagram of an acoustic transducer according to an embodiment of the first aspect.

[0015] Figure 5 This is a cross-sectional view illustrating an acoustic transducer according to a second embodiment of the first aspect, and is a view showing a cross section taken along the YZ plane.

[0016] Figure 6 This is a cross-sectional view illustrating an acoustic transducer according to a third embodiment of the first aspect, and is a view showing a cross section taken along the YZ plane.

[0017] Figure 7 This is a partial plan view illustrating part of an acoustic transducer device according to a fourth embodiment of the first aspect.

[0018] Figure 8 This is a partially enlarged plan view illustrating an enlarged portion of the acoustic transducer device according to the fourth embodiment of the first aspect.

[0019] Figure 9 This is an example of the first solution along Figure 7 Cross-sectional view of the section taken along line IX-IX.

[0020] Figure 10 This is an example of the first solution along Figure 8 Cross-sectional view of the section taken along line X-X.

[0021] Figure 11 This is a partially enlarged perspective view illustrating an enlarged portion of the acoustic converter device in the first embodiment.

[0022] Figure 12 This is a plan view illustrating an acoustic transducer according to a fifth embodiment of the first aspect.

[0023] Figure 13 This is a perspective view illustrating an acoustic transducer according to a fifth embodiment of the first aspect.

[0024] Figure 14 This is a perspective view illustrating an acoustic transducer according to a fifth embodiment of the first aspect from the bottom side.

[0025] Figure 15 This is a cross-sectional view illustrating an acoustic transducer according to a fifth embodiment of the first aspect.

[0026] Figure 16 This is a partially enlarged cross-sectional view showing an example of an enlarged view of the vibration plate (piezoelectric film) in the first embodiment.

[0027] Figure 17 This is a side view illustrating the distribution of electric charges generated on the diaphragm deformed by sound pressure in the first embodiment.

[0028] Figure 18 This is a plan view illustrating an acoustic transducer according to a sixth embodiment of the first aspect.

[0029] Figure 19 is a cross-sectional view illustrating an acoustic converter device according to a sixth embodiment of the first aspect, taken along Figure 18 Cross-sectional view of line IX-IX in FIG.

[0030] Figure 20 This is a circuit diagram of an acoustic transducer according to a sixth embodiment of the first aspect.

[0031] Figure 21 Graph showing the relationship between the sensing area diameter ratio and the normalized SNR in the first embodiment.

[0032] Figure 22 This is a perspective view illustrating the acoustic transducer device according to the first embodiment of the second aspect.

[0033] Figure 23 This is a plan view illustrating the acoustic transducer according to the first embodiment of the second aspect.

[0034] Figure 24 This is a cross-sectional view illustrating the acoustic transducer according to the first embodiment of the second aspect.

[0035] Figure 25 This is a plan view illustrating an acoustic transducer according to a second embodiment of the second aspect.

[0036] Figure 26 Graph showing the relationship between the ratio of the detection region to the total length of the cantilever and the signal level in the second embodiment.

[0037] Figure 27 This is a cross-sectional view illustrating an acoustic transducer according to a third embodiment of the second aspect.

[0038] Figure 28 This is a cross-sectional view illustrating an acoustic transducer according to a fourth embodiment of the second aspect.

[0039] Figure 29 This is a perspective view illustrating an acoustic transducer according to a fifth embodiment of the second aspect.

[0040] Figure 30 This is a circuit diagram of an acoustic transducer according to an embodiment of the second aspect.

[0041] Figure 31 It is a plan view illustrating an acoustic transducer according to a sixth embodiment of the second aspect.

[0042] Figure 32 This is a cross-sectional view illustrating an acoustic transducer according to a seventh embodiment of the second aspect.

[0043] Figure 33 This is a plan view illustrating an acoustic transducer according to an eighth embodiment of the second aspect.

[0044] Figure 34 This is a perspective view illustrating an acoustic transducer according to an eighth embodiment of the second aspect.

[0045] Figure 35 This is a perspective view illustrating an acoustic transducer according to an eighth embodiment of the second aspect from the bottom side.

[0046] Figure 36 This is a cross-sectional view illustrating an acoustic transducer according to an eighth embodiment of the second aspect.

[0047] Figure 37 This is a partially enlarged cross-sectional view showing an example of an enlarged view of the vibration plate (piezoelectric film) in the second embodiment.

[0048] Figure 38 This is a side view illustrating the distribution of electric charges generated on the vibration plate deformed by sound pressure in the second embodiment.

[0049] Figure 39 It is a plan view illustrating an acoustic transducer according to a ninth embodiment of the second aspect.

[0050] Figure 40 is a cross-sectional view illustrating an acoustic converter device according to a ninth embodiment of the second aspect, taken along Figure 18 Cross-sectional view of line IX-IX in FIG.

[0051] Figure 41 This is a circuit diagram of an acoustic transducer according to a sixth embodiment of the second aspect.

[0052] Figure 42 Graph showing the relationship between the sensing area diameter ratio and the normalized SNR in the second embodiment.

[0053] Figure 43 This is a perspective view illustrating the acoustic transducer according to the first embodiment of the third aspect.

[0054] Figure 44 This is a cross-sectional view illustrating the acoustic transducer according to the first embodiment of the third aspect.

[0055] Figure 45It is a cross-sectional view illustrating the cantilever in the third embodiment.

[0056] Figure 46 It is a cross-sectional view illustrating a cantilever of a comparative example in the third embodiment.

[0057] Figure 47 This is a graph showing the relationship between the thickness ratio of the intermediate electrode and the voltage in the third embodiment.

[0058] Figure 48 This is a plan view illustrating an acoustic transducer according to a second embodiment of the third aspect.

[0059] Figure 49 This is a cross-sectional view illustrating an acoustic transducer according to a second embodiment of the third aspect.

[0060] Figure 50 This is a plan view illustrating an acoustic transducer according to a third embodiment of the third aspect.

[0061] Figure 51 This is a perspective view illustrating an acoustic transducer according to a third embodiment of the third aspect.

[0062] Figure 52 This is a perspective view illustrating the acoustic transducer according to the third embodiment of the third aspect from the bottom side.

[0063] Figure 53 This is a cross-sectional view illustrating an acoustic transducer according to a third embodiment of the third aspect.

[0064] Figure 54 This is a partially enlarged cross-sectional view showing an example of an enlarged vibrating plate (piezoelectric film) in the third embodiment.

[0065] Figure 55 This is a side view illustrating the distribution of electric charges generated on the vibration plate deformed by sound pressure in the third embodiment.

[0066] Figure 56 This is a plan view illustrating an acoustic transducer according to a fourth embodiment of the third aspect.

[0067] Figure 57 This is a cross-sectional view of an acoustic converter device according to a fourth embodiment of the third embodiment, taken along Figure 14 Cross-sectional view of line IX-IX in FIG.

[0068] Figure 58 This is a circuit diagram of an acoustic transducer according to a fourth embodiment of the third aspect.

[0069] Figure 59 Graph showing the relationship between the sensing area diameter ratio and the normalized SNR in the third embodiment.

[0070] In the figure: 100, 100B, 100C, 100D, 100E, 100F, 100G, 200, 200B—acoustic conversion device, 10—fixed frame, 20—cantilever, 20A—cantilever (first cantilever), 20B—cantilever (second cantilever), 20C—cantilever (first cantilever), 20D—cantilever (second cantilever), 20F—cantilever (second cantilever), 21—free end, 22—fixed end, 23, 23A, 23B, 23C, 23D—plurality of detection areas, 24—non-detection area, 25—non-detection area, 25A—non-detection area (first electrode non-formation area), 25B—non-detection area (second electrode non-formation area), 25 C, 25D—non-detection area, 30—upper electrode, 31—upper electrode, 40—lower electrode, 41—lower electrode, 50, 50B, 50G—middle electrode, 51—middle electrode, 53—lower connecting electrode, 54—upper connecting electrode, 61—lower piezoelectric layer or first piezoelectric layer, 61A—lower piezoelectric layer (first lower piezoelectric layer), 61B—lower piezoelectric layer (second lower piezoelectric layer), 62—upper piezoelectric layer or second piezoelectric layer, 81—electrode non-forming area (area where the upper electrode is not formed), 82—electrode non-forming area (area where the lower electrode is not formed), 83—electrode non-forming area (area where the middle electrode is not formed), W20—width (first Width of the cantilever), W20F—width (width of the second cantilever), 62A—upper piezoelectric layer (first upper piezoelectric layer), 62B—upper piezoelectric layer (second upper piezoelectric layer), 220, 220B—vibration plate (piezoelectric element, diaphragm), 222—outer periphery (fixed end) or outer periphery (fixed body), 323, 323B—first detection area (inner detection area), 324—non-detection area (first non-detection area), 325, 325B—second detection area (outer detection area), 331, 331B—upper electrode of the detection area, 332—upper electrode of the non-detection area, 333, 333B—upper electrode of the detection area, 381, 382— Electrode non-forming area, 385, 386—electrode non-forming area (second non-detection area), 423, 423B—first detection area (inner detection area), 424—non-detection area (first non-detection area), 425, 425B—second detection area (outer detection area), 431, 431B—upper electrode of the detection area, 432—upper electrode of the non-detection area, 433, 433B—upper electrode of the detection area, 481, 482—electrode non-forming area, C11—center of the diaphragm, X—X-axis direction (first direction), Y—Y-axis direction (second direction or direction intersecting with the first direction), Z—Z-axis direction (thickness direction or plate thickness direction). DETAILED DESCRIPTION

[0071] Hereinafter, the acoustic conversion devices of the first, second and third embodiments will be described with reference to the accompanying drawings. In addition, in this specification and the drawings, the same symbols are sometimes used to mark substantially the same components and repeated descriptions are omitted. In addition, in this specification, the terms "upper" and "lower" are sometimes used. They are, for example, Figure 2 、 Figure 24 as well as Figure 44 In the illustrated state, "upper" and "lower" refer to the direction in the Z-axis direction where the upper electrode 30 is located and the direction where the lower electrode 40 is located. The actual arrangement of the sound conversion device 100 is not limited to this. In the first and second embodiments, the upper electrode 30 may be located at the bottom and the lower electrode 40 may be located at the top.

[0072] [Acoustic Converter 100 According to the First Embodiment of the First Aspect]

[0073] Figure 1 This is a perspective view illustrating an acoustic transducer device 100 according to a first embodiment of the first aspect. Figure 2 This is a cross-sectional view of an acoustic transducer device 100 illustrating a first embodiment of the first embodiment of the first scheme, and is a view showing a cross section taken along the XZ plane. In addition, in each figure, the X-axis, Y-axis, and Z-axis directions may be shown as being orthogonal to each other. The X-axis, Y-axis, and Z-axis directions may not be orthogonal. The X-axis, Y-axis, and Z-axis directions may be arbitrary directions. The X-axis direction is an example of a first direction. The Y-axis direction is an example of a second direction intersecting the first direction. The Z-axis direction is an example of the thickness direction of the piezoelectric film.

[0074] Figure 1 as well as Figure 2 The acoustic converter 100 shown is a piezoelectric acoustic converter having a piezoelectric element (piezoelectric film). The acoustic converter 100 may be, for example, a microphone (MEMS microphone). The acoustic converter 100 may also be used for noise cancellation purposes. The acoustic converter 100 may also be TWS (Ture wireless stereo) or a vehicle-mounted device installed in a car. The acoustic converter 100 may also be used as a hearing aid, for example. The acoustic converter 100 may be used for any purpose as long as it can detect physical quantities. The physical quantity may be, for example, sound pressure.

[0075] [Fixed frame 10]

[0076] The sound conversion device 100 includes a fixed frame 10 and a pair of cantilevers 20. The fixed frame 10 is a rectangular frame when viewed from the Z-axis direction. The length of the fixed frame 10 in the X-axis direction is shorter than the length of the fixed frame 10 in the Y-axis direction. The fixed frame 10 has a first base 11 and a second base 12. The first base 11 can also be a substrate. The second base 12 is formed on the first base 11.

[0077] [Cantilever 20]

[0078] The pair of cantilevers 20 includes a piezoelectric film and extends from the fixed frame 10 toward the inside of the fixed frame 10 along the X-axis direction. One end of the cantilever 20 is a fixed end 22 and the other end is a free end 21.

[0079] The pair of cantilevers 20 includes cantilevers 20A and 20B disposed facing each other in the X-axis direction. The cantilever 20A is an example of a first cantilever, and the cantilever 20B is an example of a second cantilever. The free ends 21 of the pair of cantilevers 20 face each other.

[0080] like Figure 1 As shown, a pair of slits 71 and 72 are formed around cantilevers 20A and 20B. Slits 71 and 72 are gaps formed between the fixed frame 10 and the cantilever 20, penetrating the substrate in the Z-axis direction. The pair of slits 71 extend in the X-axis direction and are formed to be separated in the Y-axis direction. Slit 72 is a gap formed between the free end 21 and the fixed frame 10. The fixed end 22 of the cantilever 20 is connected to the fixed frame 10. The width of the slits 71 and 72 can be, for example, greater than 100 nm and less than 5 μm. The width of the slits 71 and 72 can also be, for example, 0.5 μm.

[0081] exist Figure 2 , a cross section along the XZ plane of the cantilever 20 (20A) and the fixed frame 10 is shown. Figure 2 As shown, the piezoelectric film of the cantilever 20 includes a lower electrode 40 , a lower piezoelectric layer 61 , an intermediate electrode 50 , an upper piezoelectric layer 62 , and an upper electrode 30 .

[0082] [Lower electrode 40]

[0083] Lower electrode 40 is an electrode thin film having lower electrode 41 and lower electrode 42. Lower electrode 41 and lower electrode 42 are spaced apart in the X-axis direction. Between lower electrode 41 and lower electrode 42 lies an electrode-free region 82 where no electrode is formed. Electrode-free region 82 is formed by etching after lower electrode 40 is formed to remove the electrode. Electrode-free region 82 can also be formed using a lift-off method.

[0084] The lower electrode 41 is formed on a side closer to the fixed end 22 in the X-axis direction. The lower electrode 42 is formed on a side closer to the free end 21 in the X-axis direction.

[0085] [Lower piezoelectric layer 61]

[0086] The lower piezoelectric layer 61 is a piezoelectric thin film, and is formed on the lower electrode 40. The lower piezoelectric layer 61 is formed continuously in the X-axis direction.

[0087] [Intermediate electrode 50]

[0088] The intermediate electrode 50 is an electrode thin film and includes an intermediate electrode 51 and an intermediate electrode 52. The intermediate electrodes 51 and 52 are spaced apart in the X-axis direction. An electrode-free region 83, where no electrode is formed, is located between the intermediate electrodes 51 and 52. After forming the intermediate electrode 50, etching is performed to remove the electrode, forming the electrode-free region 83. The electrode-free region 83 can also be formed using a lift-off method.

[0089] The intermediate electrode 51 is formed on a side closer to the fixed end 22 in the X-axis direction. The intermediate electrode 52 is formed on a side closer to the free end 21 in the X-axis direction.

[0090] [Upper piezoelectric layer 62]

[0091] The upper piezoelectric layer 62 is a piezoelectric thin film, and is formed on the intermediate electrode 50. The upper piezoelectric layer 62 is formed continuously in the X-axis direction.

[0092] [Upper electrode 30]

[0093] The upper electrode 30 is an electrode thin film having an upper electrode 31 and an upper electrode 32. The upper electrode 31 and the upper electrode 32 are arranged spaced apart in the X-axis direction. An electrode-free region 81, where no electrode is formed, is located between the upper electrode 31 and the upper electrode 32. After forming the upper electrode 30, etching is performed to remove the electrode, forming the electrode-free region 81. The electrode-free region 81 can also be formed using a lift-off method.

[0094] The upper electrode 31 is formed on a side closer to the fixed end 22 in the X-axis direction. The upper electrode 32 is formed on a side closer to the free end 21 in the X-axis direction.

[0095] [Material and thickness of piezoelectric film]

[0096] The material of the lower piezoelectric layer 61 and the upper piezoelectric layer 62 may be, for example, ScAlN. The material of the lower piezoelectric layer 61 may also be AlN. The Sc content may be greater than 0 at% and less than 50 at%. The thickness of the lower piezoelectric layer 61 and the upper piezoelectric layer 62 may also be, for example, greater than 100 nm and less than 1 μm. The thickness of the lower piezoelectric layer 61 and the upper piezoelectric layer 62 may also be, for example, 500 nm.

[0097] The lower piezoelectric layer 61 and the upper piezoelectric layer 62 may have a fluorite structure (hafnium oxide, zirconium oxide, cesium oxide) or a wurtzite structure (zinc oxide).

[0098] [Material and thickness of electrode film]

[0099] The material of the upper electrode 30, the lower electrode 40, and the intermediate electrode 50 may be, for example, Al, Mo, Pt, Ti, etc. The thickness of the upper electrode 30, the lower electrode 40, and the intermediate electrode 50 may be, for example, not less than 5 nm and not more than 100 nm. The thickness of the upper electrode 30, the lower electrode 40, and the intermediate electrode 50 may be, for example, 50 nm.

[0100] [Detection Area 23 and Non-Detection Area 24]

[0101] The cantilever 20 includes multiple detection regions 23 capable of detecting physical quantities, and non-detection regions 24 that do not detect physical quantities. The physical quantity is, for example, sound pressure. The multiple detection regions 23 may also be regions where the upper electrode 31, the intermediate electrode 51, and the lower electrode 41 overlap in the Z-axis direction. The upper electrode 31, the intermediate electrode 51, and the lower electrode 41 are electrically connected. The acoustic transducer 100 is capable of detecting the piezoelectric output charge between the upper electrode 31 and the intermediate electrode 51. The acoustic transducer 100 is capable of detecting the piezoelectric output charge between the lower electrode 41 and the intermediate electrode 51.

[0102] The detection region 23 is arranged closer to the fixed end 22 than the non-detection region 24. In other words, the non-detection region 24 is arranged closer to the free end 21 than the detection region 23.

[0103] The upper electrode 32 , the intermediate electrode 52 , and the lower electrode 42 are electrically connected.

[0104] [Multiple detection areas 23]

[0105] Figure 3 1 is a cross-sectional view illustrating the acoustic converter device 100 according to the first embodiment of the first aspect, and is a view showing a cross section taken along the YZ plane. Figure 3As shown, the acoustic transducer 100 includes a plurality of detection regions 23 arranged in the Y-axis direction. Each of the detection regions 23 includes an upper electrode 31 (upper electrode 31A), a lower electrode 41 (lower electrode 41A), an intermediate electrode 51 (intermediate electrode 51A), a lower piezoelectric layer 61 (lower piezoelectric layer 61A), and an upper piezoelectric layer 62 (upper piezoelectric layer 62A).

[0106] A non-detection region 25 is formed between adjacent detection regions 23 in the Y-axis direction. The non-detection region 25 is a region where no physical quantity is detected. A piezoelectric layer is formed in the non-detection region 25. The piezoelectric layer of the non-detection region 25 is integrally formed with the lower piezoelectric layer 61 and the upper piezoelectric layer 62. The non-detection region 25 is an example of a first electrode non-formation region where the upper electrode 31 and the lower electrode 41 are not formed. Furthermore, the non-detection region 25 is an example of a second electrode non-formation region where the intermediate electrode 51 is not formed.

[0107] [Circuit Diagram of Acoustic Converter 100 According to the First Embodiment]

[0108] Next, a circuit diagram of the sound conversion device 100 according to the first embodiment will be described. Figure 4 This is a circuit diagram of the sound conversion device 100 according to the first embodiment.

[0109] like Figure 4 As shown, the acoustic transducer device 100 includes a MEMS microphone chip 101. The MEMS microphone chip 101 is equipped with a pair of cantilevers 20A and 20B. The MEMS microphone chip 101 may also be equipped with three or more cantilevers 20. The cantilevers 20A and 20B have multiple detection regions 23. The multiple detection regions 23 include an upper electrode 31, a lower electrode 41, and an intermediate electrode 51. The acoustic transducer device 100 is capable of detecting the piezoelectric output charge between the upper electrode 31 and the intermediate electrode 51, as well as the piezoelectric output charge between the lower electrode 41 and the intermediate electrode 51. The multiple cantilevers 20A and 20B are connected in series. In the cantilever 20A, the multiple detection regions 23 are connected in series. In the cantilever 20B, the multiple detection regions 23 are connected in series. The multiple detection regions 23 of the cantilever 20A are connected in series with the multiple detection regions 23 of the cantilever 20B.

[0110] The MEMS microphone chip 101 also has pads 13 and 14. A cantilever 20A is connected to pad 13, and a cantilever 20B is connected to pad 14. The sound converter 100 includes an IC 102 connected to pad 13. IC 102 is an amplifier that amplifies the output signal of cantilever 20. IC 102 may also be provided with a function for performing analog-to-digital (A / D) conversion after amplifying the output signal of cantilever 20.

[0111] [Wiring section 16]

[0112] Figure 11 1 is a partially enlarged perspective view showing a portion of the acoustic converter 100. Figure 1 、 Figure 4 as well as Figure 11 As shown, the acoustic converter 100 includes a wiring portion 16 that electrically connects the plurality of detection regions 23 and the pads 13 and 14. The wiring portion 16 may be formed, for example, on the upper surface (front surface) of the fixing frame 10. A portion of the wiring portion 16 may also be formed inside the fixing frame 10. The wiring portion 16 connects the electrodes of the plurality of detection regions 23 in series.

[0113] like Figure 11 As shown, the wiring portion 16 includes wiring portion 16a, wiring portion 16b, wiring portion 16c, wiring portion 16d, and wiring portion 16e. The wiring portion 16a electrically connects the intermediate electrode 51 and the pad 13. The wiring portion 16a is drawn out from the intermediate electrode 51 and connected to the pad 13.

[0114] Wiring 16b extending from upper electrode 31 to fixed frame 10 is electrically connected to wiring 16c extending from lower electrode 41 to fixed frame 10. Wiring 16b and wiring 16c are connected on fixed frame 10. Wiring 16d is connected to wiring 16b.

[0115] The wiring portion 16 d drawn from the upper electrode 31 and the wiring portion 16 e drawn from the intermediate electrode 51 to the fixed frame 10 are connected on the fixed frame 10 .

[0116] like Figure 1 As shown, the wiring section 16 includes a wiring section 16 f . The wiring section 16 f is drawn from the upper electrode 31 to the fixing frame 10 side and is connected to the pad 14 on the fixing frame 10 .

[0117] [Shape of cantilever 20]

[0118] As described above, the cantilever 20 has a rectangular shape when viewed in the Z-axis direction. The rectangular shape of the cantilever 20 increases the area of ​​the cantilever 20 within the chip, enabling higher sensitivity. In other words, while maintaining the same sensitivity, the acoustic transducer 100 can be made more compact compared to conventional devices. This miniaturization of the acoustic transducer 100 allows for a lower price.

[0119] [Full length of cantilever 20]

[0120] In the acoustic transducer 100, the resonant frequency of the cantilever 20 can be easily changed by changing the overall length of the cantilever 20. During design, increasing the overall length of the cantilever 20 can lower the resonant frequency. The resonant frequency is lower when the overall length of the cantilever 20 is longer than when the overall length of the cantilever 20 is shorter. The overall length of the cantilever 20 can also be the length of the region where the upper electrode 30, lower electrode 40, and intermediate electrode 50 overlap.

[0121] [Width of cantilever 20]

[0122] The width of the cantilever 20 is the width along the Y-axis. The width of the cantilever 20 may also be the width of the region where the upper electrode 30, lower electrode 40, and intermediate electrode 50 overlap. In the acoustic transducer 100, by varying the width of the cantilever 20, the sensitivity of the cantilever 20 can be adjusted independently of the resonant frequency. During design, increasing the width of the cantilever 20 can improve sensitivity. A wider cantilever 20 exhibits higher sensitivity than a narrower one.

[0123] [Operation and Effect of the Acoustic Conversion Device 100 According to the First Embodiment of the First Aspect]

[0124] The sound conversion device 100 of the first embodiment of the first scheme comprises: a fixed frame 10; and a cantilever 20, one end of which is a fixed end 22 fixed to the fixed frame 10 and the other end is a free end 21, and the cantilever 20 extends from the fixed frame 10 toward the inside of the fixed frame 10. The cantilever 20 has: a plurality of detection areas 23 capable of detecting physical quantities; and a non-detection area 24 that does not detect physical quantities. The electrodes of the plurality of detection areas 23 are electrically connected in series.

[0125] In the acoustic transducer 100 of the first embodiment, the deformation of the cantilever 20 is detected, thereby enabling detection of a physical quantity. Multiple detection regions 23 are formed in the acoustic transducer 100, and the electrodes of these multiple detection regions 23 are electrically connected in series, thereby enhancing the sensitivity of the cantilever 20.

[0126] In the acoustic transducer 100 , the piezoelectric film of the cantilever 20 is divided at arbitrary planes and electrically connected in series, so that the capacitance of the entire piezoelectric film (the total of the plurality of detection regions 23 ) can be arbitrarily adjusted.

[0127] In the acoustic transducer 100 , by cutting the electrodes in the width direction (Y-axis direction) of the cantilever 20 , a plurality of detection regions are formed, thereby enabling improved sensitivity.

[0128] Furthermore, in the acoustic transducer 100 , by cutting the electrode in the longitudinal direction (X-axis direction) of the cantilever 20 , the detection region 23 and the non-detection region 24 can be formed, thereby improving sensitivity.

[0129] The cantilever 20 includes a cantilever (first cantilever) 20A and a cantilever (second cantilever) 20B facing each other in the X-axis direction (first direction) in which the cantilever 20 extends.

[0130] In the acoustic transducer 100 of the first embodiment, the electrodes of the plurality of detection regions 23 of the cantilever 20A and the electrodes of the plurality of detection regions 23 of the cantilever 20B are electrically connected in series. With this configuration, the acoustic transducer 100 can improve the sensitivity of the cantilever 20 .

[0131] Furthermore, in the acoustic transducer 100 according to the first embodiment, multiple detection regions 23 are arranged near the fixed end 22, and non-detection regions 24 are arranged near the free end 21. This configuration of the acoustic transducer 100 improves the sensitivity of the cantilever 20. In the cantilever 20, stress concentrates on the base portion near the first base 11 on the fixed end 22 side, generating a high amount of charge. On the other hand, almost no stress is generated on the free end 21 side of the cantilever 20, resulting in less charge generation. Therefore, by electrically disconnecting the base portion of the first base 11 on the fixed end 22 side from the tip portion on the free end 21 side, the charge generated per unit area can be increased by using only the base portion in the detection region 23. This increases the signal level and, consequently, the sensitivity.

[0132] In addition, in the sound conversion device 100, the cantilever 20 has a piezoelectric film, the piezoelectric film includes a lower electrode 40, a lower piezoelectric layer 61 formed on the lower electrode 40, an intermediate electrode 50 formed on the lower piezoelectric layer 61, an upper piezoelectric layer 62 formed on the intermediate electrode 50, and an upper electrode 30 formed on the upper piezoelectric layer 62, and has a non-detection area (a first electrode non-forming area, or a second electrode non-forming area) 25 between the multiple detection areas 23.

[0133] In the acoustic transducer device 100 of this configuration, the piezoelectric film-forming cantilever 20 deforms, thereby connecting the piezoelectric output charges generated between the upper electrode 31 and the intermediate electrode 51, and between the lower electrode 41 and the intermediate electrode 51, in the plurality of detection regions 23 to the intermediate electrode 51. The plurality of detection regions 23 can be divided by forming a non-detection region (electrode non-formation region) 25 where the upper electrode 30, lower electrode 40, and intermediate electrode 50 are not formed.

[0134] Furthermore, in the acoustic transducer 100, the electrode-non-formed region 82, where the lower electrode 40 is not formed, is formed at a position farther from the fixed end 22 than the electrode-non-formed region 81, where the upper electrode 30 is not formed. This prevents a decrease in the crystallinity of the lower piezoelectric layer 61 between the lower electrode 41 and the intermediate electrode 51, and of the upper piezoelectric layer 62 between the intermediate electrode 51 and the upper electrode 31. Consequently, charge can be stably generated in the lower piezoelectric layer 61 and the upper piezoelectric layer 62.

[0135] Furthermore, the acoustic transducer 100 is a piezoelectric acoustic transducer and is more resistant to dust and water droplets than conventional electrostatic acoustic transducers.

[0136] Furthermore, the rectangular shape of the acoustic transducer 100 allows for a larger area of ​​the cantilever 20 within the chip, resulting in higher sensitivity. This increased sensitivity allows for a smaller acoustic transducer 100. In the acoustic transducer 100, the resonant frequency can be easily varied by changing the length of the detection region 23 of the cantilever 20. By varying the width W20 of the detection region 23, the sensitivity can be adjusted regardless of the resonant frequency.

[0137] [Acoustic Converter 100B According to Second Embodiment of First Aspect]

[0138] Next, an acoustic conversion device 100B according to a second embodiment of the first aspect will be described. Figure 5 This is a cross-sectional view illustrating an acoustic transducer 100B according to the second embodiment of the first aspect, and is a view showing a cross section taken along the YZ plane. Figure 5 The sound conversion device 100B of the second embodiment of the first aspect shown in FIG. Figure 3 The acoustic transducer 100 of the first embodiment of the first embodiment shown differs in that non-detection regions 25A and 25B are formed instead of the non-detection region 25, and the arrangement of the upper electrode 31, lower electrode 41, and intermediate electrode 51 is different. Furthermore, in the description of the acoustic transducer 100B of the second embodiment of the first embodiment, descriptions that are identical to those of the acoustic transducer 100 of the first embodiment of the first embodiment may be omitted.

[0139] [Non-detection areas 25A, 25B]

[0140] The cantilever 20 of the acoustic conversion device 100B includes multiple detection areas 23A, 23B, 23C, and 23D. These multiple detection areas 23A, 23B, 23C, and 23D are arranged in the Y-axis direction. A non-detection area 25A is formed between the detection area 23A and the detection area 23B. A non-detection area 25B is formed between the detection area 23B and the detection area 23C. A non-detection area 25A is formed between the detection area 23C and the detection area 23D.

[0141] The intermediate electrode 51 in the detection region 23A is electrically connected to the intermediate electrode 51 in the detection region 23B. The upper electrode 31 in the detection region 23A is not electrically connected to the upper electrode 31 in the detection region 23B. The lower electrode 41 in the detection region 23A is not electrically connected to the lower electrode 41 in the detection region 23B. The intermediate electrode 51 is formed in the non-detection region 25A, connecting the detection regions 23A and 23B in series. The non-detection region 25A is an example of a first electrode non-formation region where the upper electrode 31 and the lower electrode 41 are not formed.

[0142] Upper electrode 31 of detection region 23B is electrically connected to upper electrode 31 of detection region 23C. Lower electrode 41 of detection region 23B is electrically connected to lower electrode 41 of detection region 23C. Intermediate electrode 51 of detection region 23B is not electrically connected to intermediate electrode 51 of detection region 23C. Upper electrode 31 and lower electrode 41 are formed in non-detection region 25B, connecting detection regions 23B and 23C in series. Non-detection region 25B is an example of a second electrode non-formation region where intermediate electrode 51 is not formed.

[0143] The intermediate electrode 51 in detection region 23C is electrically connected to the intermediate electrode 51 in detection region 23D. The upper electrode 31 in detection region 23C is electrically connected to the upper electrode 31 in detection region 23D. The lower electrode 41 in detection region 23C is not electrically connected to the lower electrode 41 in detection region 23D. In non-detection region 25A, intermediate electrode 51 is formed, connecting detection regions 23C and 23D in series. Non-detection region 25A is an example of a first electrode non-formation region where the upper electrode 31 and the lower electrode 41 are not formed.

[0144] In the sound conversion device 100B, the non-detection regions 25A and the non-detection regions 25B are alternately arranged in the Y-axis direction.

[0145] [Polarization Direction of the Piezoelectric Film of the Cantilever 20]

[0146] Next, the polarization direction of the piezoelectric film of the cantilever 20 will be described. Figure 5, the polarization directions in the lower piezoelectric layer 61 and the upper piezoelectric layer 62 are connected by arrows. For example, the upper electrode 31 and the lower electrode 41 in the detection area 23A are electrically connected to the terminal B (pad 13), and the upper electrode 31 and the lower electrode 41 in the detection area 23D are electrically connected to the terminal A (pad 14). In addition, other electrodes and wiring parts may be electrically connected between the upper electrode 31 and the lower electrode 41 and the terminals A and B. For example, terminal B is set to GND. For example, when an arbitrary value is set to "x", the potentials of the electrodes between terminals A and B (upper electrode 31, lower electrode 41 and intermediate electrode 51) become the following relationship, realizing series connection.

[0147] The potential of the upper electrode 31 and the lower electrode 41 of the detection area 23D may also be +4xV. The potential of the intermediate electrode 51 of the detection area 23D and the detection area 23C may also be +3xV. The potential of the upper electrode 31 and the lower electrode 41 of the detection area 23C and the detection area 23B may also be +2xV. The potential of the intermediate electrode 51 of the detection area 23B and the detection area 23A may also be +xV. The potential of the upper electrode 31 and the lower electrode 41 of the detection area 23A may also be 0V.

[0148] The polarization direction of detection region 23A is from the upper electrode 31 and the lower electrode 41 toward the intermediate electrode 51. The polarization direction of detection region 23B is from the intermediate electrode 51 toward the upper electrode 31 and the lower electrode 41. The polarization direction of detection region 23C is from the upper electrode 31 and the lower electrode 41 toward the intermediate electrode 51. The polarization direction of detection region 23D is from the intermediate electrode 51 toward the upper electrode 31 and the lower electrode 41.

[0149] By applying a DC (direct current) voltage between the terminal A and the terminal B in advance, the polarization direction of the piezoelectric film can be realized as described above.

[0150] [Operation and Effect of the Acoustic Conversion Device 100B According to the Second Embodiment of the First Aspect]

[0151] The sound conversion device 100B according to the second embodiment of the first aspect also exhibits the same effects as the sound conversion device 100 according to the first embodiment. In the sound conversion device 100B according to the second embodiment of the first aspect, the non-detection areas 25A and the non-detection areas 25B may be arranged alternately.

[0152] In the acoustic transducer 100B of this configuration, multiple detection regions (divided regions) 23 can be electrically connected in series without the need for a separate wiring section 16. This means that wiring sections connecting the multiple detection regions 23 do not need to be formed outside the piezoelectric film. In the acoustic transducer 100, series connection is achieved by making the polarization directions of adjacent regions differ.

[0153] The acoustic transducer 100B eliminates the need for external wiring sections 16 connecting multiple detection areas 23, enabling space savings, reducing the complexity of the film-forming process, and suppressing unwanted increases in overall device capacitance and leakage current caused by parasitic capacitance. The acoustic transducer 100B can also reduce the number of wiring sections 16 formed on the upper surface of the fixing frame 10, achieving space savings and miniaturization. For example, while maintaining the same surface area as conventional acoustic transducer 100B, sensitivity can be improved by increasing the area of ​​the piezoelectric film of the cantilever 20.

[0154] [Acoustic Converter 100C According to Third Embodiment of First Aspect]

[0155] Next, an acoustic transducer 100C according to a third embodiment of the first aspect will be described. Figure 6 This is a cross-sectional view illustrating an acoustic transducer 100C according to a third embodiment of the first aspect, and is a view showing a cross section taken along the YZ plane. Figure 6 The acoustic conversion device 100C shown is Figure 3 The acoustic transducer 100 of the first embodiment of the first embodiment shown in the figure differs in that a non-detection region 25C is formed instead of the non-detection region 25, and a lower connection electrode 53 and an upper connection electrode 54 are formed. Furthermore, in the description of the acoustic transducer 100C of the third embodiment of the first embodiment, descriptions that are identical to those of the acoustic transducers 100 and 100B of the first embodiment may be omitted.

[0156] [Non-detection areas 25A, 25B]

[0157] The cantilever 20 of the acoustic conversion device 100C has multiple detection areas 23A, 23B, 23C, and 23D. These multiple detection areas 23A, 23B, 23C, and 23D are arranged in the Y-axis direction. A non-detection area 25C is formed between the detection area 23A and the detection area 23B. Similarly, a non-detection area 25C is formed between the detection area 23B and the detection area 23C. A non-detection area 25C is formed between the detection area 23C and the detection area 23D. The detection areas 23A and 23C are examples of first detection areas, and the detection areas 23B and 23D are examples of second detection areas.

[0158] A lower connecting electrode 53 and an upper connecting electrode 54 are formed in the non-detection region 25C between the detection region 23A and the detection region 23B. The lower connecting electrode 53 electrically connects the lower electrode 41 (first lower electrode 41A) in the detection region 23A with the intermediate electrode 51 (second intermediate electrode 51B) in the detection region 23B. The upper connecting electrode 54 electrically connects the upper electrode 31 (first upper electrode 31A) in the detection region 23A with the intermediate electrode 51 in the detection region 23B. The lower connecting electrode 53 and the upper connecting electrode 54 are formed so as to branch from the intermediate electrode 51 in the detection region 23B. The intermediate electrode 51 (first intermediate electrode 51A) in the detection region 23A is connected to the upper electrode 31 (second upper electrode 31B), the lower electrode 41 (second lower electrode 41B), and the intermediate electrode 51 (second intermediate electrode 51B) in the detection region 23B.

[0159] A lower connecting electrode 53 and an upper connecting electrode 54 are formed in the non-detection region 25C between the detection region 23B and the detection region 23C. The lower connecting electrode 53 electrically connects the lower electrode 41 of the detection region 23B with the intermediate electrode 51 of the detection region 23C. The upper connecting electrode 54 electrically connects the upper electrode 31 of the detection region 23B with the intermediate electrode 51 of the detection region 23C. The lower connecting electrode 53 and the upper connecting electrode 54 are formed so as to branch from the intermediate electrode 51 of the detection region 23C. The intermediate electrode 51 of the detection region 23B is not connected to the upper electrode 31, the lower electrode 41, or the intermediate electrode 51 of the detection region 23C.

[0160] A lower connecting electrode 53 and an upper connecting electrode 54 are formed in the non-detection region 25C between the detection region 23C and the detection region 23D. The lower connecting electrode 53 electrically connects the lower electrode 41 of the detection region 23C with the intermediate electrode 51 of the detection region 23D. The upper connecting electrode 54 electrically connects the upper electrode 31 of the detection region 23C with the intermediate electrode 51 of the detection region 23D. The lower connecting electrode 53 and the upper connecting electrode 54 are formed so as to branch from the intermediate electrode 51 of the detection region 23D. The intermediate electrode 51 of the detection region 23C is not connected to the upper electrode 31, the lower electrode 41, or the intermediate electrode 51 of the detection region 23D.

[0161] [Polarization Direction of the Piezoelectric Film of the Cantilever 20]

[0162] Next, the polarization direction of the piezoelectric film of the cantilever 20 will be described. Figure 6 , the polarization directions in the lower piezoelectric layer 61 and the upper piezoelectric layer 62 are connected by arrows. The polarization directions in the detection regions 23A, 23B, 23C, and 23D are from the intermediate electrode 51 toward the upper electrode 31 and the lower electrode 41. The detection region 23A includes a lower piezoelectric layer 61A and an upper piezoelectric layer 62B. The detection region 23B includes a lower piezoelectric layer 61B and an upper piezoelectric layer 62B. The lower piezoelectric layer 61A is an example of a first lower piezoelectric layer, and the upper piezoelectric layer 62A is an example of a first upper piezoelectric layer. The lower piezoelectric layer 61B is an example of a second lower piezoelectric layer, and the upper piezoelectric layer 62B is an example of a second upper piezoelectric layer.

[0163] [Operation and Effect of the Acoustic Conversion Device 100C According to the Third Embodiment of the First Aspect]

[0164] The acoustic transducer 100C of the third embodiment of the first aspect also achieves the same effects as the acoustic transducers 100 and 100B of the aforementioned embodiments. The acoustic transducer 100C of the third embodiment of the first aspect may also include a lower connecting electrode 53 and an upper connecting electrode 54 branching from the intermediate electrode 51. The intermediate electrodes 51 and lower electrode 41 of adjacent detection regions 23A to 23D may be connected via the lower connecting electrode 53, and the intermediate electrodes 51 and upper electrode 31 of adjacent detection regions 23A to 23C may be connected via the upper connecting electrode 54.

[0165] [Acoustic Converter 100D According to Fourth Embodiment of First Aspect]

[0166] Next, an acoustic transducer 100D according to a fourth embodiment of the first aspect will be described. Figure 7 This is a partial plan view illustrating a portion of an acoustic transducer 100D according to a fourth embodiment of the first aspect. Figure 8This is a partially enlarged plan view illustrating an enlarged portion of an acoustic transducer 100D according to a fourth embodiment of the first aspect. Figure 9 is an example along Figure 7 Cross-sectional view of the section taken along line IX-IX. Figure 10 is an example along Figure 8 Cross-sectional view of the section taken along line X-X.

[0167] Figures 7 to 10 The acoustic conversion device 100D shown is Figure 3 The acoustic transducer 100 of the first embodiment of the first aspect shown differs in that a non-detection region 25D is formed in place of the non-detection region 25 and a wiring section 90 is provided. Furthermore, in the description of the acoustic transducer 100D of the fourth embodiment of the first aspect, descriptions identical to those of the acoustic transducers 100, 100B, and 100C of the embodiments of the first aspect may be omitted.

[0168] [Non-detection areas 25A, 25B]

[0169] like Figure 7 as well as Figure 8 As shown, the cantilever 20 of the acoustic transducer 100D includes multiple detection areas 23A, 23B, 23C, and 23D. These multiple detection areas 23A, 23B, 23C, and 23D are arranged in the Y-axis direction. A non-detection area 25D is formed between the multiple detection areas 23A to 23D.

[0170] like Figure 9 As shown, in the non-detection region 25D between the detection region 23A and the detection region 23B, the protruding portion 31 a of the upper electrode 31 , the protruding portion 41 a of the lower electrode 41 , and the protruding portion 51 b of the intermediate electrode 51 are formed.

[0171] Extension 31a extends from upper electrode 31 in detection region 23A toward upper electrode 31B in detection region 23B in the Y-axis direction. Extension 41a extends from lower electrode 41A in detection region 23A toward lower electrode 41B in detection region 23B in the Y-axis direction. Extension 51b extends from intermediate electrode 51B in detection region 23B toward intermediate electrode 51A in detection region 23A in the Y-axis direction.

[0172] [Wiring section 90]

[0173] The acoustic transducer 100D includes a wiring section 90 formed in the non-detection region 25D. Within the non-detection region 25D, the wiring section 90 electrically connects the extension 41a of the lower electrode 41A, the extension 51b of the intermediate electrode 51B, and the extension 31a of the upper electrode 31A. The wiring section 90 includes a first bonding portion 91, a first rising portion 92, a second bonding portion 93, a second rising portion 94, and a third bonding portion 95.

[0174] The first bonding portion 91 is formed on the overhanging portion 41a of the lower electrode 41A and is bonded to the lower electrode 41A. The first rising portion 92 is connected to the first bonding portion 91 and extends in the thickness direction of the piezoelectric film. The second bonding portion 93 is connected to the first rising portion 92, formed on the overhanging portion 51b of the intermediate electrode 51B, and is bonded to the intermediate electrode 51B. The second rising portion 94 is connected to the second bonding portion 93 and extends in the thickness direction of the piezoelectric film. The third bonding portion 95 is connected to the second rising portion 94, formed on the overhanging portion 31a of the upper electrode 31A, and is bonded to the upper electrode 31A.

[0175] [Operation and Effect of the Acoustic Conversion Device 100D According to the Fourth Embodiment of the First Aspect]

[0176] The acoustic transducer 100D according to the fourth embodiment of the first aspect also achieves the same operational effects as the acoustic transducers 100 and 100B according to the aforementioned embodiments. The acoustic transducer 100D according to the fourth embodiment of the first aspect may also include a wiring section 90 that electrically connects the lower electrode 41A, the intermediate electrode 51B, and the upper electrode 31A.

[0177] [Acoustic Converter 200 According to Fifth Embodiment of First Aspect]

[0178] Next, an acoustic transducer device 200 according to a fifth embodiment of the first aspect will be described. Figure 12 It is a plan view illustrating an acoustic transducer device 200 according to the fifth embodiment. Figure 13 This is a perspective view illustrating an acoustic transducer 200 according to a fifth embodiment of the first aspect. Figure 14 This is a perspective view illustrating an acoustic transducer device 200 according to a fifth embodiment of the first aspect, viewed from the bottom side. Figure 15This is a cross-sectional view illustrating a sound conversion device 200 according to the fifth embodiment of the first embodiment. In each figure, the X-axis, Y-axis, and Z-axis directions may be shown as being orthogonal to each other. The X-axis, Y-axis, and Z-axis directions may not be orthogonal. The X-axis, Y-axis, and Z-axis directions may be arbitrary directions. The X-axis direction is an example of a first direction. The Y-axis direction is an example of a direction intersecting the first direction. In the description of the sound conversion device 200 according to the fifth embodiment of the first embodiment, descriptions identical to those of the sound conversion device 100 according to the first embodiment will be omitted.

[0179] [Supporting substrate 211]

[0180] The sound conversion device 200 includes a supporting substrate (fixed frame) 211 and a vibration plate (piezoelectric element) 220. The supporting substrate 211 may also be rectangular when viewed in the Z-axis direction. The thickness direction of the supporting substrate 211 is along the Z-axis direction. The supporting substrate 211 has an upper surface 211a and a lower surface 211b that are opposite to each other in the Z-axis direction. An opening 221 is formed in the supporting substrate 211. The opening 221 is formed in a manner that penetrates the supporting substrate 211 in the Z-axis direction. The supporting substrate 211 is formed, for example, from a silicon wafer. The opening 221 is formed in a manner that is circular when viewed in the Z-axis direction.

[0181] [Vibration plate 220]

[0182] The vibration plate 220 has a piezoelectric film. The vibration plate 220 is formed in a manner covering the opening 221. The vibration plate 220 is formed in a manner that is circular when viewed in the Z-axis direction. The outer periphery 222 of the vibration plate 220 is the fixed end of the vibration plate 220 and is fixed to the upper surface 211a of the support substrate 211. As described later, the vibration plate 220 has a first detection area 323, a non-detection area 324, and a second detection area 325. The vibration plate 220 is also called a "diaphragm". In addition, the opening 221 is not limited to a circle and can also be an ellipse or other shape.

[0183] [Piezoelectric film]

[0184] The piezoelectric film serving as the vibration plate 220 is deformed according to sound pressure and generates electric charge. Figure 16 This is an enlarged cross-sectional view illustrating an enlarged piezoelectric film. The piezoelectric film includes a lower electrode layer 440, a lower piezoelectric layer (first piezoelectric layer) 460, an intermediate electrode layer 250, an upper piezoelectric layer (second piezoelectric layer) 360, and an upper electrode layer 330. The lower electrode layer 440, the lower piezoelectric layer 460, the intermediate electrode layer 250, the upper piezoelectric layer 360, and the upper electrode layer 330 are stacked in this order.

[0185] [Lower electrode layer 440]

[0186] The lower electrode layer 440 includes lower electrodes 441 to 443 serving as electrode films. The lower electrode layer 440 is positioned near the opening 221 in the Z-axis direction. The lower electrodes 441 to 443 are positioned separately in the X-axis direction. The lower electrode 441 is circular. The lower electrode 441 is positioned near the center C11 of the vibration plate 220 when viewed in the Z-axis direction. The lower electrode 442 is annular when viewed in the Z-axis direction. The lower electrode 442 is radially arranged outside the lower electrode 441. The lower electrode 443 is annular when viewed in the Z-axis direction. The lower electrode 443 is radially arranged outside the lower electrode 442.

[0187] [Electrode non-formation regions 483 and 484]

[0188] In the radial direction of the vibration plate 220 , an electrode-free region 483 is provided between the lower electrodes 441 and 442 . In the radial direction of the vibration plate 220 , an electrode-free region 484 is provided between the lower electrodes 442 and 443 .

[0189] [Lower piezoelectric layer 460]

[0190] The lower piezoelectric layer 460 is a piezoelectric thin film, and is formed on the lower electrode layer 440. The lower piezoelectric layer 460 is formed continuously in the radial direction of the vibration plate 220.

[0191] [Intermediate electrode layer 250]

[0192] The intermediate electrode layer 250 includes intermediate electrodes 251 to 253, which are thin electrode films. The intermediate electrode layer 250 is formed on the lower piezoelectric layer 460. The intermediate electrodes 251 to 253 are spaced apart in the X-axis direction. The intermediate electrode 251 is circular. When viewed in the Z-axis direction, the intermediate electrode 251 is positioned near the center C11 of the vibration plate 220. The intermediate electrode 252 is annular when viewed in the Z-axis direction. The intermediate electrode 252 is radially outside the intermediate electrode 251. The intermediate electrode 253 is annular when viewed in the Z-axis direction. The intermediate electrode 253 is radially outside the intermediate electrode 252.

[0193] [Electrode non-formation regions 281, 282]

[0194] In the radial direction of the vibration plate 220 , an electrode-free region 281 is provided between the intermediate electrodes 251 and 252 . In the radial direction of the vibration plate 220 , an electrode-free region 282 is provided between the intermediate electrodes 252 and 253 .

[0195] [Upper piezoelectric layer 360]

[0196] The upper piezoelectric layer 360 is a piezoelectric thin film, and is formed on the intermediate electrode layer 250. The upper piezoelectric layer 360 is formed continuously in the radial direction of the vibration plate 220.

[0197] [Upper electrode layer 330]

[0198] The upper electrode layer 330 includes upper electrodes 331 to 333 as electrode films. The upper electrode layer 330 is formed on the upper piezoelectric layer 360. The upper electrodes 331 to 333 are arranged separately in the X-axis direction. The upper electrode 331 is circular. When viewed in the Z-axis direction, the upper electrode 331 is arranged at a position close to the center C11 of the vibration plate 220. The upper electrode 332 is ring-shaped when viewed in the Z-axis direction. The upper electrode 332 is arranged radially outside the upper electrode 331. The upper electrode 333 is ring-shaped when viewed in the Z-axis direction. The upper electrode 333 is arranged radially outside the upper electrode 332.

[0199] [Material and thickness of piezoelectric film]

[0200] The piezoelectric material used as the lower piezoelectric layer 460 and the upper piezoelectric layer 360 may be, for example, aluminum nitride (AlN) or scandium-doped aluminum nitride (ScAlN (Sc: 1 to 60 at%)), or a piezoelectric material having a fluorite structure (hafnium oxide, zirconium oxide, cesium oxide), or a piezoelectric material having a wurtzite structure (zinc oxide, gallium nitride).

[0201] The thickness of the lower piezoelectric layer 460 may be, for example, not less than 100 nm and not more than 1 μm. The material of the lower piezoelectric layer 460 is, for example, ScAlN (Sc: 40 at %), and the thickness of the lower piezoelectric layer 460 may be, for example, 500 nm.

[0202] The thickness of the upper piezoelectric layer 360 is, for example, not less than 100 nm and not more than 1 μm. The material of the upper piezoelectric layer 360 is, for example, ScAlN (Sc: 40 at %), and the thickness of the upper piezoelectric layer 360 may be, for example, 500 nm.

[0203] [Material and thickness of electrode film]

[0204] The thickness of the electrode thin films in the upper electrode layer 330, the intermediate electrode layer 250, and the lower electrode layer 440 may be, for example, 5 nm or more and 100 nm or less. The thickness of the electrode thin films may be, for example, 20 nm. The electrode thin films in the upper electrode layer 330, the intermediate electrode layer 250, and the lower electrode layer 440 may also be formed with different thicknesses.

[0205] The material of the electrode thin films in the upper electrode layer 330, the intermediate electrode layer 250, and the lower electrode layer 440 may be formed, for example, from at least one of gold, platinum, tungsten, aluminum, copper, molybdenum, ruthenium, titanium, chromium, and nickel, or an alloy containing at least one of these. The electrode thin films in the upper electrode layer 330, the intermediate electrode layer 250, and the lower electrode layer 440 may be formed from the same material or different materials.

[0206] [First Detection Area, Non-Detection Area, and Second Detection Area]

[0207] like Figure 15 as well as Figure 16 As shown, diaphragm 220 includes first detection regions 323, 423, non-detection regions 324, 424, and second detection regions 325, 425. First detection regions 323, 423, and second detection regions 325, 425 are regions capable of detecting physical quantities. Non-detection regions 324, 424 are regions where no physical quantity is detected. For example, the physical quantity is sound pressure.

[0208] The first detection region 323 is the region where the intermediate electrode 251, upper piezoelectric layer 360, and upper electrode 331 overlap in the Z-axis direction. The first detection region 423 is the region where the lower electrode 441, lower piezoelectric layer 460, and intermediate electrode 251 overlap in the Z-axis direction. The acoustic transducer 200 can detect the piezoelectric output charge between the lower electrode 441 and the intermediate electrode 251. The acoustic transducer 200 can detect the piezoelectric output charge between the intermediate electrode 251 and the upper electrode 331.

[0209] Non-detection region 324 includes the area where the intermediate electrode 252, upper piezoelectric layer 360, and upper electrode 332 overlap in the Z-axis direction. Non-detection region 424 includes the area where the lower electrode 442, lower piezoelectric layer 460, and intermediate electrode 252 overlap in the Z-axis direction. The acoustic transducer 200 cannot detect the piezoelectric output charge between the lower electrode 442 and the intermediate electrode 252. The acoustic transducer 200 cannot detect the piezoelectric output charge between the intermediate electrode 252 and the upper electrode 332.

[0210] The second detection region 325 is the region where the intermediate electrode 253, the upper piezoelectric layer 360, and the upper electrode 333 overlap in the Z-axis direction. The second detection region 425 is the region where the lower electrode 443, the lower piezoelectric layer 460, and the intermediate electrode 253 overlap in the Z-axis direction. The acoustic transducer 200 can detect the piezoelectric output charge between the lower electrode 443 and the intermediate electrode 253. The acoustic transducer 200 can detect the piezoelectric output charge between the intermediate electrode 253 and the upper electrode 333.

[0211] First detection regions 323 and 423 are formed near the center of vibration plate 220. Non-detection regions 324 and 424 are formed radially outward of first detection regions 323 and 423 in vibration plate 220. Second detection regions 325 and 425 are formed radially outward of non-detection regions 324 and 424 in vibration plate 220.

[0212] [Outer diameters of the first detection area 323, the non-detection area 324, and the second detection area 325]

[0213] like Figure 12 As shown, the outer diameter Φ323 of the first detection area 323 is, for example, 0.59 mm. The outer diameter Φ324 of the non-detection area 324 is, for example, 0.81 mm. The outer diameter Φ325 of the second detection area 325 is, for example, 1 mm.

[0214] [Split Position]

[0215] like Figure 16 As shown, electrode non-formation regions 483 and 484 are formed in the lower electrode layer 440 , electrode non-formation regions 281 and 282 are formed in the intermediate electrode layer 250 , and electrode non-formation regions 381 and 382 are formed in the upper electrode layer 330 .

[0216] The electrode non-formed regions 281 , 282 , 381 , 382 , 483 , and 484 may also be referred to as “dividing positions.” These electrode non-formed regions 281 , 282 , 381 , 382 , 483 , and 484 are arranged at different positions in the radial direction of the vibration plate 220 .

[0217] The electrode non-formation region 381 is arranged radially inward of the vibration plate 220 relative to the electrode non-formation region 281. The electrode non-formation region 281 is arranged radially inward of the vibration plate 220 relative to the electrode non-formation region 483.

[0218] The electrode non-formation region 382 is arranged outside the electrode non-formation region 282 in the radial direction of the vibration plate 220 . The electrode non-formation region 282 is arranged outside the electrode non-formation region 484 in the radial direction of the vibration plate 220 .

[0219] In the vibration plate 220, the plurality of electrode-free regions 281, 282, 381, 382, ​​483, and 484 are formed at positions that do not overlap when viewed in the Z-axis direction. This prevents a decrease in the strength of the vibration plate 220. Furthermore, piezoelectric thin films are formed in the electrode-free regions 281, 282, 483, and 484.

[0220] The crystallinity of the piezoelectric film above the boundary between the end of the lower electrode 441 and the electrode non-formed region 483 is lower than the crystallinity of the piezoelectric film above the lower electrode 441. Similarly, the crystallinity of the piezoelectric film above the boundary between the electrode and the electrode non-formed region is lower than the crystallinity of the piezoelectric film above the electrode.

[0221] The splitting position, which serves as the electrode-free region 483, is located radially outward from the first detection region 423 of the diaphragm 220. The splitting position, which serves as the electrode-free region 484, is located radially inward from the second detection region 425 of the diaphragm 220. This prevents the crystal growth of the piezoelectric thin film that generates charge from being hindered. In the acoustic transducer 200, the piezoelectric thin film in the first detection region 423 and the second detection region 425, where charge is generated, has high crystallinity.

[0222] The splitting position, which serves as the electrode-free region 281, is located radially outward from the first detection region 323 of the diaphragm 220. The splitting position, which serves as the electrode-free region 282, is located radially inward from the second detection region 325 of the diaphragm 220. This prevents the crystal growth of the piezoelectric thin film that generates charge from being hindered. In the acoustic transducer 200, the piezoelectric thin film in the first detection region 323 and the second detection region 325, where charge is generated, has high crystallinity.

[0223] [Connection of piezoelectric film]

[0224] In the vibrating plate 220, which functions as a piezoelectric film (piezoelectric element), the electrodes of the first detection regions 323 and 423 are electrically connected in parallel. The electrodes of the first detection region 323 include an upper electrode 331 and an intermediate electrode 251. The electrodes of the first detection region 423 include a lower electrode 441 and an intermediate electrode 251. The electrodes of the second detection regions 325 and 425 are electrically connected in parallel. The electrodes of the second detection region 325 include an upper electrode 333 and an intermediate electrode 253. The electrodes of the second detection region 425 include a lower electrode 443 and an intermediate electrode 253.

[0225] The electrodes of the first detection region and the second detection region are electrically connected in series. Specifically, the electrodes are upper electrodes 331 and 333, lower electrodes 441 and 443, or intermediate electrodes 251 and 253.

[0226] [Operation and Effect of the Acoustic Conversion Device 200 According to the Fifth Embodiment of the First Aspect]

[0227] The acoustic transducer device 200 according to the fifth embodiment of the first aspect includes a support substrate (fixing frame) 211 and a vibration plate 220 serving as a piezoelectric element fixed to the support substrate 211. The vibration plate 220 has a plurality of detection regions capable of detecting physical quantities, namely first detection regions 323 and 423 and second detection regions 325 and 425, and non-detection regions 324 and 424 that do not detect physical quantities. The electrodes of the plurality of detection regions are electrically connected in series.

[0228] In the acoustic transducer 200 of the first embodiment, deformation of the diaphragm 220 is detected by detecting the deformation of the diaphragm 220, thereby enabling detection of a physical quantity. Acoustic transducer 200 includes first detection regions 323 and 423 and second detection regions 325 and 425. By electrically connecting the electrodes of these multiple detection regions in series, the sensitivity of the diaphragm 220 can be enhanced.

[0229] In the acoustic transducer device 200 , the piezoelectric element is a vibration plate (diaphragm) 220 , and an outer periphery 222 of the vibration plate 220 (outer periphery of the diaphragm) is a fixed end fixed to the support substrate 211 .

[0230] In the acoustic converter 200, the multiple detection areas include first detection areas 323 and 423, which are located radially closer to the center C11 of the diaphragm 220, and second detection areas 325 and 425, which are located radially farther from the center C11 of the diaphragm 220. Non-detection areas 324 and 424 are formed circumferentially between the inner and outer detection areas.

[0231] In the acoustic transducer 200 of the first embodiment, deformation of the diaphragm 220 generates electric charges corresponding to the diaphragm 220, and the generated electric charges are detected in the first detection regions 323 and 423 and the second detection regions 325 and 425. In the acoustic transducer 200, the electrodes are cut in the radial direction of the diaphragm 220 to form the first detection regions 323 and 423, the non-detection regions 324 and 424, and the second detection regions 325 and 425. This acoustic transducer 200 can improve the sensitivity of detecting electric charges based on sound pressure.

[0232] Figure 17 2 is a side view illustrating the distribution of electric charges generated on the vibration plate 220 that is deformed by sound pressure. In the vibration plate 220 serving as a diaphragm, the outer periphery 222 on the radially outer side is fixed to the support substrate 211. Figure 17As shown, the area near the inflection point P12 is less likely to deform and the amount of charge generated is small. The inflection point P12 and its vicinity, where the amount of charge generated is small, are included in the non-detection areas 324 and 424.

[0233] In contrast, the area near the center C11 of the diaphragm 220 and the periphery 222 of the diaphragm 220 deforms significantly, resulting in a higher amount of charge. The center C11 of the diaphragm 220 and its surrounding area are included in the first detection areas 323 and 423. The area near the periphery 222 of the diaphragm 220 is included in the second detection areas 325 and 425. In the sound conversion device 200, the area including the inflection point P12, where charge generation is relatively low, is not included in the first detection areas 323 and 423 or the second detection areas 325 and 425. This improves the signal-to-noise ratio (SN) of the sound conversion device 200, enabling detection sensitivity for charge.

[0234] [Shape of the End of the Electrode]

[0235] Next, the shape of the end portion of the electrode will be described. Figure 16 As shown, the ends of the upper electrodes 331-333, lower electrodes 441-443, and intermediate electrodes 251-253 may also be tapered. The ends of the electrodes are radially opposed to each other in the vibrating plate 220. The tapered shape of the electrode ends is formed so that the lower side protrudes further than the upper side.

[0236] By tapering the ends of the lower electrodes 441 to 443 in this manner, the steps at the boundaries between the lower electrodes 441 to 443 and the electrode-free regions 483 and 484 can be made gentle. This can suppress a decrease in the crystallinity of the piezoelectric layer 460. The same applies to the boundaries between the other electrodes and the electrode-free regions.

[0237] [Acoustic Converter 200B According to Sixth Embodiment of the First Aspect]

[0238] Next, an acoustic transducer 200B according to a sixth embodiment of the first aspect will be described. Figure 18 This is a plan view illustrating an acoustic transducer 200B according to a sixth embodiment of the first aspect. Figure 19 is a cross-sectional view illustrating an acoustic converter device according to a sixth embodiment of the first aspect, taken along Figure 18 Cross-sectional view of line IX-IX in FIG. Figure 18 as well as Figure 19 The sound conversion device 200B of the sixth embodiment of the first aspect shown in FIG. Figure 12The acoustic transducer 200 of the fifth embodiment shown differs in that it includes a plurality of circumferentially divided upper electrodes 331B and 333B, a plurality of circumferentially divided lower electrodes 441B and 443B, a plurality of circumferentially divided intermediate electrodes 251B and 253B, and radially extending electrode-free regions 385 and 386. In the description of the acoustic transducer 200B of the sixth embodiment of the first embodiment, descriptions identical to those of the acoustic transducer 200 of the fifth embodiment of the first embodiment may be omitted.

[0239] [Laminated body 300B]

[0240] like Figure 19 As shown, the acoustic transducer 200B includes laminates 300B and 400B. The laminate 300B includes an upper electrode layer 330B, a piezoelectric layer 360, and an intermediate electrode layer 250B. The upper electrode layer 330B includes a plurality of upper electrodes 331B divided in the circumferential direction, a circumferentially continuous upper electrode 332, and a plurality of circumferentially divided upper electrodes 333B. The intermediate electrode layer 250B includes a plurality of intermediate electrodes 251B divided in the circumferential direction, a circumferentially continuous intermediate electrode 252, and a plurality of circumferentially divided intermediate electrodes 253B.

[0241] [First detection area 323B]

[0242] The stack 300B includes a first detection region 323B, a non-detection region 324B, and a second detection region 325B. The first detection region 323B includes multiple upper electrodes 331B, a piezoelectric layer 360, and multiple intermediate electrodes 251B. The first detection region 323B includes multiple piezoelectric elements. Each piezoelectric element in the first detection region 323B includes an upper electrode 331B, a piezoelectric layer 360, and an intermediate electrode 251B.

[0243] [Second detection area 325B]

[0244] The second detection region 325B includes a plurality of upper electrodes 333B, a piezoelectric layer 360, and a plurality of intermediate electrodes 253B. The second detection region 325B includes a plurality of piezoelectric elements. In the second detection region 325B, the piezoelectric element includes an upper electrode 333B, a piezoelectric layer 360, and an intermediate electrode 253B.

[0245] like Figure 18 As shown, electrode non-formation regions 381 and 382 and electrode non-formation regions 385 and 386 are formed in the upper electrode layer 330B.

[0246] [Electrode non-formation region 385]

[0247] Electrode-free regions 385 divide the upper electrode into multiple sections within first detection region 323B. Electrode-free regions 385 extend radially from the center of diaphragm 220B. Multiple electrode-free regions 385 are circumferentially spaced evenly apart. The areas of the multiple upper electrodes 331B are substantially equal. For example, the sound conversion device 200B includes ten upper electrodes 331B.

[0248] [Electrode non-formation region 386]

[0249] Electrode non-formation region 386 divides the upper electrode into a plurality of parts in second detection region 325B. Electrode non-formation region 386 extends radially from electrode non-formation region 382 toward outer periphery 222 of vibration plate 220. Multiple electrode non-formation regions 386 are arranged at equal intervals in the circumferential direction.

[0250] [Laminated body 400B]

[0251] like Figure 19 As shown, the stack 400B includes an intermediate electrode layer 250B, a piezoelectric layer 460, and a lower electrode layer 440B. The intermediate electrode layer 250B serves as both the stack 300B and the stack 400B. The lower electrode layer 440B includes a plurality of lower electrodes 441B divided in the circumferential direction, a circumferentially continuous lower electrode 442, and a plurality of lower electrodes 443B divided in the circumferential direction.

[0252] [First detection area 423B]

[0253] The stack 400B includes a first detection region 423B, a non-detection region 424B, and a second detection region 425B. The first detection region 423B includes multiple intermediate electrodes 251B, a piezoelectric layer 460, and multiple lower electrodes 441B. The first detection region 423B includes multiple piezoelectric elements. In the first detection region 423B, the piezoelectric elements include intermediate electrodes 251B, a piezoelectric layer 460, and lower electrodes 441B. In the first detection region 423B, the areas of the multiple lower electrodes 441B are substantially equal.

[0254] [Second detection area 425B]

[0255] Second detection region 425B includes multiple intermediate electrodes 253B, a piezoelectric layer 460, and multiple lower electrodes 443B. Second detection region 425B includes multiple piezoelectric elements. In second detection region 425B, the piezoelectric elements include intermediate electrodes 253B, a piezoelectric layer 460, and lower electrodes 443B. In second detection region 425B, the areas of the multiple lower electrodes 443B are substantially equal.

[0256] Like the upper electrode layer 330B of the stacked body 300B, the lower electrode layer 440B and the intermediate electrode layer 250B of the stacked body 400B include electrode-free regions extending in the radial direction.

[0257] [Electrostatic Capacitance of Piezoelectric Element]

[0258] In the stacked body 300B, the capacitances of the plurality of piezoelectric elements arranged in the circumferential direction of the vibration plate 220B are equal to each other. In the stacked body 400B, the capacitances of the plurality of piezoelectric elements arranged in the circumferential direction of the vibration plate 220B are substantially equal to each other.

[0259] [Series connection of multiple piezoelectric elements]

[0260] In the vibration plate 220B, a plurality of piezoelectric elements arranged in the circumferential direction and the radial direction are electrically connected in series.

[0261] [Operation and Effect of the Acoustic Conversion Device 200B According to the Sixth Embodiment of the First Aspect]

[0262] The sound transducer 200B according to the sixth embodiment of the first aspect also exhibits the same operational effects as those of the sound transducer 200 according to the fifth embodiment of the first aspect.

[0263] In the acoustic transducer 200B, the multiple detection areas include first detection areas 323B and 423B, which are located radially closer to the center C11 of the diaphragm 220B; and second detection areas 325B and 425B, which are located radially farther from the center C11 of the diaphragm 220B. The non-detection areas 324 and 424 include electrode-free areas 381 and 382, ​​which are formed circumferentially of the diaphragm 220B between the inner and outer detection areas; and multiple electrode-free areas 385 and 386, which extend radially along the diaphragm and are spaced apart circumferentially.

[0264] According to such an acoustic transducer 200B, by including the electrode non-formation regions 385 and 386 extending in the radial direction, the electrode in the detection region can be divided into a plurality of parts.

[0265] [Modification of the Acoustic Conversion Device 200B According to the Sixth Embodiment of the First Aspect]

[0266] In the acoustic transducer 200B, the diaphragm (piezoelectric element) 220B includes a piezoelectric film, which includes a lower electrode layer 440B; a lower piezoelectric layer 460 formed on the lower electrode layer 440B; an intermediate electrode layer 250B formed on the lower piezoelectric layer 460; an upper piezoelectric layer 360 formed on the intermediate electrode layer 250B; and an upper electrode layer 330B formed on the upper piezoelectric layer 360. Between the plurality of detection regions (first detection regions 323B and 423B and second detection regions 325B and 425B) are located electrode-free regions (first electrode-free regions) where the upper and lower electrodes are not formed, or electrode-free regions (second electrode-free regions) where the intermediate electrodes are not formed.

[0267] In the acoustic conversion device 200B, when electrode-non-formation regions (first electrode-non-formation regions) are formed on the upper and lower electrodes, electrode-non-formation regions (second electrode-non-formation regions) do not need to be formed on the intermediate electrode. In the acoustic conversion device 200B, when electrode-non-formation regions (second electrode-non-formation regions) are formed on the intermediate electrode, electrode-non-formation regions (first electrode-non-formation regions) 381, 382, ​​483, and 484 do not need to be formed on the upper and lower electrodes.

[0268] Furthermore, within the detection region, the upper electrode, the intermediate electrode, and the lower electrode may be divided circumferentially. The upper electrode division position (electrode non-formed region) may differ from the intermediate electrode division position in the circumferential direction. Similarly, the lower electrode division position may differ from the intermediate electrode division position in the circumferential direction.

[0269] [Circuit Diagram of Acoustic Conversion Device 200B According to Sixth Embodiment of First Aspect]

[0270] Next, a circuit diagram of an acoustic transducer 200B according to a sixth embodiment of the first aspect will be described. Figure 20 This is a circuit diagram of an acoustic transducer 200B according to a sixth embodiment of the first aspect.

[0271] like Figure 20 As shown, the acoustic transducer 200B includes a MEMS microphone chip 201. The MEMS microphone chip 201 carries a vibration plate 220B. The vibration plate 220B includes a plurality of first detection areas 323B and 423B and second detection areas 325B and 425B.

[0272] The multiple first detection regions 323B and 423B include an upper electrode 331B, an intermediate electrode 251B, and a lower electrode 441B. The multiple second detection regions 325B and 425B include an upper electrode 333B, an intermediate electrode 253B, and a lower electrode 443B. The upper electrode 331B includes n circumferentially divided upper electrodes 331B-1, 331B-2, ..., 331B-n. n is a natural number. The same applies to the other upper, intermediate, and lower electrodes.

[0273] In the first detection regions 323B and 423B of the acoustic transducer 200B, piezoelectric output charges between the upper electrode 331B and the intermediate electrode 251B, and between the intermediate electrode 251B and the lower electrode 441B can be detected. Plural piezoelectric elements arranged in the circumferential direction are connected in series.

[0274] In the second detection regions 325B and 425B of the acoustic transducer 200B, piezoelectric output charges between the upper electrode 333B and the intermediate electrode 253B, and between the intermediate electrode 253B and the lower electrode 443B can be detected.

[0275] The MEMS microphone chip 201 also has pads 213 and 214. Multiple electrodes of piezoelectric elements are connected to these pads. The sound converter 200B includes an IC 202 connected to the pads 213. IC 202 is an amplifier that amplifies the output signal of the piezoelectric element of the vibration plate 220B. Alternatively, IC 202 may also be configured to amplify the output signal of the piezoelectric element of the vibration plate 220B and then perform analog-to-digital conversion.

[0276] The polarity of the charge generated in the second detection regions 325B and 425B is opposite to the polarity of the charge generated in the first detection regions 323B and 423B. Therefore, the wiring in the second detection regions 325B and 425B and the first detection regions 323B and 423B are connected in series in reverse order.

[0277] [Electrode connection]

[0278] In the acoustic transducer 200B, the upper electrodes 331B and the intermediate electrodes 251B of the plurality of first detection regions 323B may be electrically connected in series. Similarly, the upper electrodes 333B and the intermediate electrodes 253B of the plurality of second detection regions 325B may be electrically connected in series.

[0279] In the acoustic transducer 200B, the lower electrodes 441B and the intermediate electrodes 251B of the plurality of first detection regions 423B may be electrically connected in series. Similarly, the lower electrodes 433B and the intermediate electrodes 253B of the plurality of second detection regions 425B may be electrically connected in series.

[0280] In the acoustic conversion device 200B, the upper electrodes and the lower electrodes of the plurality of detection areas may be electrically connected in parallel.

[0281] [Regarding the relationship between the sensing area diameter ratio and the normalized SNR]

[0282] Next, the relationship between the sensing area diameter ratio and the normalized SNR will be described. Figure 21 It is a graph showing the relationship between the ratio of the sensing area diameter and the normalized SNR. Figure 21 In FIG. 5 , the horizontal axis represents the sensing area diameter ratio [%], and the vertical axis represents the normalized SNR [%]. Figure 21 The graph shown is a representation of Figure 12 FIG. 1 is a graph showing the relationship between the sensor area diameter ratio and the normalized SNR in the acoustic transducer 200 according to the fifth embodiment of the first aspect.

[0283] The "sensing area ratio" can be expressed by the following formula (1).

[0284] Sensing area ratio = (electrode separation radius / diaphragm radius) × 100···(1)

[0285] The “electrode separation radius” may also be the radius of the inner detection area 323. The “diaphragm radius” may also be the radius of the vibration plate 220. Figure 12 , a diameter φ323 of the inner detection region 323 and a diameter φ325 of the vibration plate 220 are shown.

[0286] The inner diameter of the opening 221 covered by the vibration plate 220 is set to 100% of the sensing area diameter ratio. The normalized SNR is set to 100% when the electrode non-formation area is formed at 71%. Figure 12 In , “0” indicates the position of the boundary between the inner detection area 323 and the non-detection area 324. Figure 12 In FIG. 3 , “×” indicates the position of the boundary between the outer detection area 325 and the non-detection area 324 .

[0287] The SNR normalized value of the inner detection area 323 is a value obtained when the boundary between the outer detection area 325 and the non-detection area 324 is set to 71% and the outer diameter Φ323 of the inner detection area 323 is changed.

[0288] The SNR normalized value of the outer detection area 325 is a value obtained when the boundary between the inner detection area 323 and the non-detection area 324 is set to 71% and the inner diameter Φ324 of the outer detection area 325 is changed.

[0289] exist Figure 21 In the example shown, the SNR normalized value of the inner detection area 323 reaches a maximum at point P21. The sensing area diameter ratio at point P21 is 59%.

[0290] exist Figure 21 In the example shown, the SNR normalized value of the outer detection area 325 reaches a maximum at point P22. The sensing area diameter ratio at point P22 is 81%.

[0291] When the sensing area diameter ratio of the inner detection area 323 is 44% or more and 71% or less, the normalized SNR value is 100% or more. When the sensing area diameter ratio of the inner detection area 323 is 49% or more and 67% or less, the normalized SNR value is 104% or more. When the sensing area diameter ratio of the inner detection area 323 is 51% or more and 65% or less, the normalized SNR value is 106% or more.

[0292] The sensing area diameter ratio of the inner detection region 323 is preferably 44% to 71%, more preferably 49% to 67%, and even more preferably 51% to 65%.

[0293] When the sensing area diameter ratio of the outer detection area 325 is 71% or more and 89% or less, the normalized SNR value is 100% or more. When the sensing area diameter ratio of the outer detection area 325 is 75% or more and 87% or less, the normalized SNR value is 104% or more. When the sensing area diameter ratio of the outer detection area 325 is 78% or more and 84% or less, the normalized SNR value is 106% or more.

[0294] The sensing area diameter ratio of the outer detection region 325 is preferably 71% to 89%, more preferably 75% to 87%, and even more preferably 78% to 84%.

[0295] The case where the sensing area diameter ratio of the inner detection region 323 is 71% and the sensing area diameter ratio of the outer detection region 325 is 71% may also be a case where the electrode division position exists at the 71% position.

[0296] In the acoustic conversion device 200, when the sensing area diameter ratio of the outer detection area 325 is 71% or more and 89% or less, the sensing area diameter ratio of the inner detection area 323 may be set to a value outside the range of 44% or more and 71% or less. In such a case, the normalized SNR value may be higher.

[0297] In the acoustic conversion device 200, when the sensing area diameter ratio of the inner detection area 323 is 44% or more and 71% or less, the sensing area diameter ratio of the outer detection area 325 may be set to a value outside the range of 71% or more and 89% or less. In such a case, the normalized SNR value may be higher.

[0298] [Acoustic Converter 100 According to First Embodiment of Second Aspect]

[0299] Figure 22 This is a perspective view illustrating the acoustic transducer 100 according to the first embodiment of the second aspect. Figure 23 It is a plan view illustrating the acoustic transducer device 100 according to the first embodiment of the second aspect. Figure 24 This is a cross-sectional view illustrating the acoustic conversion device according to the first embodiment of the second aspect. In addition, in each figure, the X-axis, Y-axis, and Z-axis directions may be shown as mutually orthogonal. The X-axis, Y-axis, and Z-axis directions may not be orthogonal. The X-axis, Y-axis, and Z-axis directions may be arbitrary directions. The X-axis direction is an example of a first direction. The Y-axis direction is an example of a direction intersecting the first direction.

[0300] Figures 22 to 24 The acoustic converter 100 shown is a piezoelectric acoustic converter having a piezoelectric element (piezoelectric film). The acoustic converter 100 may be, for example, a microphone (MEMS microphone). The acoustic converter 100 may also be used for noise cancellation purposes. The acoustic converter 100 may also be TWS (Ture wireless stereo) or a vehicle-mounted device installed in a car. The acoustic converter 100 may also be used as a hearing aid, for example. The acoustic converter 100 may be used for any purpose as long as it can detect physical quantities. The physical quantity may be, for example, sound pressure.

[0301] [Fixed frame 10]

[0302] The acoustic conversion device 100 includes a fixed frame 10 and a cantilever 20. The fixed frame 10 is a rectangular frame when viewed in the Z-axis direction. The length of the fixed frame 10 in the X-axis direction is shorter than the length of the fixed frame 10 in the Y-axis direction. The fixed frame 10 has a first base 11 and a second base 12. The first base 11 may also be a substrate. The second base 12 is formed on the first base 11.

[0303] [Cantilever 20]

[0304] The cantilever 20 has a piezoelectric film. The cantilever 20 extends from the fixed frame 10 toward the inner side of the fixed frame 10 along the X-axis direction. One end of the cantilever 20 is a fixed end 22, and the other end is a free end 21. Figure 22 as well as Figure 23 As shown, a pair of slits 71 and slit 72 are formed around the cantilever 20. Slits 71 and 72 are gaps formed between the fixed frame 10 and the cantilever 20, penetrating the substrate in the Z-axis direction. The pair of slits 71 extend in the X-axis direction and are formed to be separated in the Y-axis direction. Slit 72 is a gap formed between the free end 21 and the fixed frame 10. The fixed end 22 of the cantilever 20 is connected to the fixed frame 10. The width of the slits 71 and 72 can be, for example, greater than 100 nm and less than 5 μm. The width of the slits 71 and 72 can also be, for example, 0.5 μm.

[0305] Figure 24 Indicates along Figure 23 The cross section of line III-III in . Figure 24 As shown, the piezoelectric film of the cantilever 20 includes a lower electrode 40 , a first piezoelectric layer 61 , an intermediate electrode 50 , a second piezoelectric layer 62 , and an upper electrode 30 .

[0306] [Lower electrode 40]

[0307] The lower electrode 40 is an electrode thin film having a first lower electrode 41 and a second lower electrode 42. The first lower electrode 41 and the second lower electrode 42 are spaced apart in the X-axis direction. An electrode-free region 82, where no electrode is formed, is located between the first lower electrode 41 and the second lower electrode 42. The electrode-free region 82 is formed by etching after forming the lower electrode 40 to remove the electrode. The electrode-free region 82 can also be formed using a lift-off method.

[0308] The first lower electrode 41 is formed on a side closer to the fixed end 22 in the X-axis direction. The second lower electrode 42 is formed on a side closer to the free end 21 in the X-axis direction.

[0309] [First Piezoelectric Layer 61]

[0310] The first piezoelectric layer 61 is a piezoelectric thin film, and is formed on the lower electrode 40. The first piezoelectric layer 61 is formed continuously in the X-axis direction.

[0311] [Intermediate electrode 50]

[0312] The intermediate electrode 50 is an electrode thin film and includes a first intermediate electrode 51 and a second intermediate electrode 52. The first intermediate electrode 51 and the second intermediate electrode 52 are spaced apart in the X-axis direction. An electrode-free region 83, where no electrode is formed, is located between the first intermediate electrode 51 and the second intermediate electrode 52. The electrode-free region 83 is formed by etching after forming the intermediate electrode 50 to remove the electrode. The electrode-free region 83 can also be formed using a lift-off method.

[0313] The first intermediate electrode 51 is formed on a side closer to the fixed end 22 in the X-axis direction. The second intermediate electrode 52 is formed on a side closer to the free end 21 in the X-axis direction.

[0314] [Second piezoelectric layer 62]

[0315] The second piezoelectric layer 62 is a piezoelectric thin film, and is formed on the intermediate electrode 50. The first piezoelectric layer 61 is formed continuously in the X-axis direction.

[0316] [Upper electrode 30]

[0317] The upper electrode 30 is an electrode thin film having a first upper electrode 31 and a second upper electrode 32. The first upper electrode 31 and the second upper electrode 32 are spaced apart in the X-axis direction. An electrode-free region 81, where no electrode is formed, is located between the first upper electrode 31 and the second upper electrode 32. After forming the upper electrode 30, etching is performed to remove the electrodes, forming the electrode-free region 81. The electrode-free region 81 can also be formed using a lift-off method.

[0318] The first upper electrode 31 is formed on a side closer to the fixed end 22 in the X-axis direction. The second upper electrode 32 is formed on a side closer to the free end 21 in the X-axis direction.

[0319] [Material and thickness of piezoelectric film]

[0320] The material of the first piezoelectric layer 61 and the second piezoelectric layer 62 may be, for example, ScAlN. The material of the first piezoelectric layer 61 may also be AlN. The Sc content may be greater than 0 at % and less than 50 at %. The thickness of the first piezoelectric layer 61 and the second piezoelectric layer 62 may also be, for example, greater than 100 nm and less than 1 μm. The thickness of the first piezoelectric layer 61 and the second piezoelectric layer 62 may also be, for example, 500 nm.

[0321] The first piezoelectric layer 61 and the second piezoelectric layer 62 may have a fluorite structure (hafnium oxide, zirconium oxide, cesium oxide) or a wurtzite structure (zinc oxide).

[0322] [Material and thickness of electrode film]

[0323] The material of the upper electrode 30, the lower electrode 40, and the intermediate electrode 50 may be, for example, Al, Mo, Pt, Ti, etc. The thickness of the upper electrode 30, the lower electrode 40, and the intermediate electrode 50 may be, for example, not less than 5 nm and not more than 100 nm. The thickness of the upper electrode 30, the lower electrode 40, and the intermediate electrode 50 may be, for example, 50 nm.

[0324] [Detection Area 23 and Non-Detection Area 24]

[0325] The cantilever 20 includes a detection region 23 capable of detecting a physical quantity and a non-detection region 24 incapable of detecting the physical quantity. The physical quantity may be, for example, sound pressure. The detection region 23 may be a region where the first upper electrode 31, the first intermediate electrode 51, and the first lower electrode 41 overlap in the Z-axis direction. The first upper electrode 31, the first intermediate electrode 51, and the first lower electrode 41 are electrically connected. The acoustic transducer 100 is capable of detecting the piezoelectric output charge between the first upper electrode 31 and the first intermediate electrode 51. The acoustic transducer 100 is capable of detecting the piezoelectric output charge between the first lower electrode 41 and the first intermediate electrode 51.

[0326] The detection region 23 is arranged closer to the fixed end 22 than the non-detection region 24. In other words, the non-detection region 24 is arranged closer to the free end 21 than the detection region 23.

[0327] The non-detection region 24 is a region of the cantilever 20 excluding the detection region 23. The second upper electrode 32, the second intermediate electrode 52, and the second lower electrode 42 are not electrically connected.

[0328] [Length L21 of detection area 23]

[0329] The length L21 of the detection region 23 is the length in the X-axis direction. The length L21 of the detection region 23 may be the length of the first upper electrode 31 , the first intermediate electrode 51 , and the first lower electrode 41 , whichever is shorter.

[0330] The length L21 of the detection area 23 may be greater than 20% and less than 75% of the total length L20 of the cantilever 20. The total length L20 of the cantilever 20 is the length in the X-axis direction, which is the length from the fixed end 22 to the free end 21. The length L21 of the detection area 23 may be greater than 30% and less than 60% of the total length L20 of the cantilever 20. The length L21 of the detection area 23 may be greater than 40% and less than 45% of the total length L20 of the cantilever 20. The length of the non-detection area 24 is the remaining length after subtracting the length L21 of the detection area 23 from the total length L20 of the cantilever 20.

[0331] The first upper electrode 31 is shorter than the first intermediate electrode 51 and the first lower electrode 41 in the X-axis direction. The first lower electrode 41 is longer than the first upper electrode 31 and the first intermediate electrode 51 in the X-axis direction.

[0332] The second upper electrode 32 is longer in the X-axis direction than the second intermediate electrode 52 and the first piezoelectric layer 61. The second lower electrode 42 is shorter in the X-axis direction than the second upper electrode 32 and the second intermediate electrode 52.

[0333] [Split Position]

[0334] As described above, an electrode non-formation region 81 is formed between the first upper electrode 31 and the second upper electrode 32. The electrode non-formation region 81 may also be referred to as a splitting position. The splitting position as the electrode non-formation region 81 may be formed in a range of 20% to 75% of the total length L20 from the fixed end 22 to the cantilever 20. The splitting position as the electrode non-formation region 81 may also be formed in a range of 30% to 60% of the total length L20 from the fixed end 22 to the cantilever 20. The splitting position as the electrode non-formation region 81 may also be formed in a range of 40% to 45% of the total length L20 from the fixed end 22 to the cantilever 20.

[0335] In the X-axis direction, the end of the detection area 23 closer to the free end 21 may be located at a position that is between 20% and 75% of the total length L20 of the cantilever 20, as measured from the fixed end 22. The end of the detection area 23 closer to the free end 21 is the end farther from the fixed end 22. In the X-axis direction, the end of the detection area 23 closer to the free end 21 may be located at a position that is between 30% and 60% of the total length L20 of the cantilever 20, as measured from the fixed end 22. In the X-axis direction, the end of the detection area 23 closer to the free end 21 may be located at a position that is between 40% and 45% of the total length L20 of the cantilever 20, as measured from the fixed end 22.

[0336] The division positions of the upper electrode 30 (electrode non-formation region 81), the division positions of the intermediate electrode 50 (electrode non-formation region 83), and the division positions of the lower electrode 40 (electrode non-formation region 82) in the X-axis direction do not overlap with each other. A first intermediate electrode 51 and a first lower electrode 41 are formed below the electrode non-formation region 81. A second intermediate electrode 52 and a second upper electrode 32 are formed above the electrode non-formation region 82. The second upper electrode 32 is formed above the electrode non-formation region 83, and the first lower electrode 41 is formed below the electrode non-formation region 83. This can suppress a decrease in the mechanical strength of the cantilever 20. Furthermore, a piezoelectric film is formed in the electrode non-formation regions 81 to 83.

[0337] The electrode non-formation region 81 is located closer to the fixed end 22 than the electrode non-formation regions 82 and 83. The electrode non-formation region 82 is located farther from the fixed end 22 than the electrode non-formation regions 81 and 83. The crystallinity of the piezoelectric film above the boundary between the electrode non-formation region 82 and the end of the first lower electrode 41 is lower than the crystallinity of the piezoelectric film above the lower electrode 40. Similarly, the crystallinity of the piezoelectric film at the boundary between the electrode non-formation region 82 and the end of the second lower electrode 42 is lower than the crystallinity of the piezoelectric film above the lower electrode 40. In the cantilever 20, since the electrode non-formation region 82 is located farther from the fixed end 22 than the electrode non-formation regions 81 and 83, the boundaries with the ends of the first lower electrode 41 and the second lower electrode 42 are also formed at distant locations, thereby not hindering the crystal growth of the piezoelectric film that generates charge. The piezoelectric film generating charge includes a first piezoelectric layer 61 between the first lower electrode 41 and the first intermediate electrode 51, and a second piezoelectric layer 62 between the first upper electrode 31 and the first intermediate electrode 51. In the cantilever 20, the piezoelectric film in the detection region 23 generating charge has high crystallinity.

[0338] [Shape of cantilever 20]

[0339] As described above, the cantilever 20 has a rectangular shape when viewed in the Z-axis direction. The rectangular shape of the cantilever 20 increases the area of ​​the cantilever 20 within the chip, enabling higher sensitivity. In other words, while maintaining the same sensitivity, the acoustic transducer 100 can be made more compact compared to conventional devices. This miniaturization of the acoustic transducer 100 allows for a lower price.

[0340] [Full length L20 of cantilever 20]

[0341] In the acoustic transducer device 100, the resonant frequency of the cantilever 20 can be easily changed by changing the total length L20 of the cantilever 20. During design, the resonant frequency can be lowered by increasing the total length L20 of the cantilever 20. The resonant frequency is lower when the total length L20 is longer than when the total length L20 is shorter.

[0342] [Width W20 of cantilever 20]

[0343] exist Figure 23 The width W20 of the cantilever 20 is shown in the figure. The width W20 of the cantilever 20 is the width along the Y-axis and is the width of the detection area 23. In the acoustic converter 100, by changing the width W20 of the cantilever 20, the sensitivity of the cantilever 20 can be adjusted regardless of the resonant frequency. The sensitivity of the cantilever 20 is the sensitivity of the detection area 23. During design, increasing the width W20 of the cantilever 20 can improve sensitivity. A wider width W20 results in higher sensitivity than a narrower width W20.

[0344] [Shape of the End of the Electrode]

[0345] The ends of the electrodes in the X-axis direction may also be tapered. The electrodes include an upper electrode 30, a lower electrode 40, and an intermediate electrode 50. The thickness of the ends of the electrodes in the X-axis direction may be thinner than the thickness of the center portion of the electrodes in the X-axis direction. The ends of the electrodes may also be formed at an acute angle. The tapered shape may also be tilted so that the lower end is positioned outward from the upper end in the X-axis direction.

[0346] The end of the electrode can also be arranged inward of the free end 21 in the X-axis direction. In the X-axis direction, the first piezoelectric layer 61 and the second piezoelectric layer 62 can also be formed outside the end of the electrode. The first piezoelectric layer 61 and the second piezoelectric layer 62 can also be connected in the Z-axis direction in the area outside the end of the electrode. In this way, the tapered shape of the end of the electrode can suppress the decrease in the crystallinity of the first piezoelectric layer 61 and the second piezoelectric layer 62. Therefore, in the first piezoelectric layer 61 and the second piezoelectric layer 62, electric charges can be stably generated.

[0347] [Operation and Effect of the Acoustic Conversion Device 100 According to the First Embodiment of the Second Aspect]

[0348] The sound conversion device 100 of the first embodiment of the second scheme includes: a fixed frame 10; and a cantilever 20, one end of which is a fixed end 22 fixed to the fixed frame 10 and the other end is a free end 21, and the cantilever 20 extends from the fixed frame 10 toward the inside of the fixed frame 10, and the cantilever 20 has: a detection area 23 capable of detecting physical quantities; and a non-detection area 24 that does not detect physical quantities.

[0349] In the acoustic transducer 100 of the second embodiment, deformation of the cantilever 20 is detected, thereby enabling detection of a physical quantity. In the acoustic transducer 100, the electrodes are cut along the longitudinal direction (X-axis direction) of the cantilever 20 to form a detection region 23 and a non-detection region 24, thereby enhancing sensitivity.

[0350] In the cantilever 20, stress concentrates at the base portion near the first base portion 11 on the fixed end 22 side, generating a high charge. On the other hand, near the free end 21 side of the cantilever 20, stress is almost nonexistent, resulting in low charge generation. Therefore, by electrically disconnecting the base portion of the first base portion 11 on the fixed end 22 side from the tip portion on the free end 21 side, using only the base portion in the detection region 23, the charge generated per unit area can be increased. This improves the signal level and sensitivity.

[0351] In addition, in the acoustic conversion device 100, the cantilever 20 has a piezoelectric film, which includes: a lower electrode 40; a first piezoelectric layer 61 formed on the lower electrode 40; an intermediate electrode 50 formed on the first piezoelectric layer 61; a second piezoelectric layer 62 formed on the intermediate electrode 50; and an upper electrode 30 formed on the second piezoelectric layer 62, and between the detection area 23 and the non-detection area 24, there are electrode non-forming areas 82, 83, and 81 in which at least one of the lower electrode 40, the intermediate electrode 50, and the upper electrode 30 is not formed.

[0352] In the acoustic transducer 100 with this structure, the piezoelectric film-forming cantilever 20 deforms, causing piezoelectric output charges generated between the first upper electrode 31 and the first intermediate electrode 51, and between the first lower electrode 41 and the first intermediate electrode 51, in the detection region 23 to connect to the first intermediate electrode 51. In the acoustic transducer 100, electrode-free regions 82, 83, and 81, where no electrode is formed, are formed in at least one of the lower electrode 40, the intermediate electrode 50, and the upper electrode 30, thereby separating the detection region 23 from the non-detection region 24.

[0353] In the acoustic transducer 100, the electrode-non-formed region 82, where the lower electrode 40 is not formed, is formed at a position farther from the fixed end 22 than the electrode-non-formed region 81, where the upper electrode 30 is not formed. This prevents a decrease in the crystallinity of the first piezoelectric layer 61 between the first lower electrode 41 and the intermediate electrode 50, and of the second piezoelectric layer 62 between the intermediate electrode 50 and the first upper electrode 31. Consequently, charge can be stably generated in the first and second piezoelectric layers 61, 62.

[0354] Furthermore, the acoustic transducer 100 is a piezoelectric acoustic transducer and is more resistant to dust and water droplets than conventional electrostatic acoustic transducers.

[0355] Furthermore, the rectangular shape of the acoustic transducer 100 allows for a larger area of ​​the cantilever 20 within the chip, resulting in higher sensitivity. This increased sensitivity allows for miniaturization of the acoustic transducer 100. In the acoustic transducer 100, the resonant frequency can be easily changed by varying the overall length 20L of the cantilever 20. In the acoustic transducer 100, the sensitivity can be varied regardless of the resonant frequency by varying the width W20 of the detection region 23.

[0356] [Acoustic Converter 100B According to Second Embodiment of Second Aspect]

[0357] Next, an acoustic conversion device 100B according to a second embodiment of the second aspect will be described. Figure 25 This is a plan view illustrating an acoustic transducer 100B according to a second embodiment of the second aspect. Figure 25 The sound conversion device 100B of the second embodiment of the second aspect shown in FIG. Figure 2 The acoustic transducer 100 of the first embodiment of the second aspect shown differs from the acoustic transducer 100 of the first embodiment of the second aspect in that it includes a pair of cantilevers 20. In the description of the acoustic transducer 100B of the second embodiment of the second aspect, descriptions that are identical to those of the acoustic transducer 100 of the first embodiment of the second aspect may be omitted.

[0358] The acoustic conversion device 100B includes a pair of cantilevers 20. The pair of cantilevers 20 includes cantilevers 20A and 20B arranged to oppose each other in the X-axis direction. Cantilever 20A is an example of a first cantilever, and cantilever 20B is an example of a second cantilever. The free ends 21 of the pair of cantilevers 20 are opposed to each other. Cantilevers 20A and 20B have the same structure as the cantilever 20 described above. The capacitive element of cantilever 20A is connected in series with the capacitive element of cantilever 20B.

[0359] [Operation and Effect of the Acoustic Conversion Device 100B According to the Second Embodiment of the Second Aspect]

[0360] The sound transducer 100B according to the second embodiment of the second aspect also achieves the same effects as the sound transducer 100 according to the first embodiment of the second aspect described above. The sound transducer 100B according to the second embodiment of the second aspect includes a pair of cantilevers 20 that face each other in the X-axis direction, thereby improving sensitivity.

[0361] [Relationship between the Ratio of the Detection Area 23 and the Signal Level]

[0362] Next, refer to Figure 26 , the relationship between the ratio of the detection area 23 and the signal level is explained. Figure 26 Graph showing the relationship between the ratio of the detection area 23 to the total length L10 of the cantilever 20 and the signal level. Figure 26 In the figure, the horizontal axis represents the ratio of the detection area 23 (%), and the vertical axis represents the signal level (%). The ratio of the detection area 23 is the ratio of the length L21 of the detection area 23 to the total length L20 of the cantilever 20. When the ratio of the detection area 23 is between 40% and 45%, the signal level is 125% or higher. By keeping the ratio of the detection area 23 between 40% and 45%, the signal-to-noise ratio (S / N) can be improved by approximately 1.5 dB. Figure 26 The graph shown may be, for example, a calculation result of the acoustic conversion device 100B.

[0363] [Acoustic Converter 100C According to the Third Embodiment of the Second Aspect]

[0364] Next, an acoustic transducer 100C according to a third embodiment of the second aspect will be described. Figure 27 This is a cross-sectional view illustrating an acoustic transducer 100C according to a third embodiment of the second aspect. Figure 27 The acoustic conversion device 100C shown is Figure 24 The acoustic transducer 100 of the first embodiment of the second aspect shown differs from the first embodiment of the second aspect in that the upper electrode 30 and the lower electrode 40 are not divided. Furthermore, in the description of the acoustic transducer 100C of the third embodiment of the second aspect, descriptions that are identical to those of the acoustic transducer 100 of the first embodiment of the second aspect may be omitted.

[0365] The cantilever 20 of the acoustic transducer 100C includes an upper electrode 30, an intermediate electrode 50, and a lower electrode 40. The upper electrode 30 is formed continuously from the fixed end 22 to the free end 21. The lower electrode 40 is formed continuously from the fixed end 22 to the free end 21. The intermediate electrode 50 includes a first intermediate electrode 51 and a second intermediate electrode 52. An electrode-free region 83 is formed between the first intermediate electrode 51 and the second intermediate electrode 52.

[0366] The cantilever 20 has a detection region 23 and a non-detection region 24. The detection region 23 is the region where the lower electrode 40, the first intermediate electrode 51, and the upper electrode 30 overlap in the Z-axis direction. The acoustic transducer 100C can detect the capacitance between the upper electrode 30 and the first intermediate electrode 51. The acoustic transducer 100C can also detect the capacitance between the lower electrode 40 and the first intermediate electrode 51. The length L21C of the detection region 23 is the length of the first intermediate electrode 51 in the X-axis direction.

[0367] [Operation and Effect of Acoustic Conversion Device 100C According to Third Embodiment of Second Aspect]

[0368] The acoustic transducer 100C of the third embodiment of the second aspect also achieves the same effects as the acoustic transducer 100 of the first embodiment of the second aspect. In the acoustic transducer 100C, the intermediate electrode 50 is divided, but the upper electrode 30 and the lower electrode 40 do not need to be divided.

[0369] [Acoustic Converter 100D According to Fourth Embodiment of Second Aspect]

[0370] Next, an acoustic transducer 100D according to a fourth embodiment of the second aspect will be described. Figure 28 This is a cross-sectional view illustrating an acoustic transducer 100D according to a fourth embodiment of the second aspect. Figure 28 The acoustic conversion device 100D shown is Figure 24 The acoustic transducer 100 of the first embodiment of the second aspect shown differs from the intermediate electrode 50 in that the intermediate electrode 50 is not divided. In the description of the acoustic transducer 100C of the third embodiment of the second aspect, descriptions that are identical to those of the acoustic transducer 100 of the first embodiment of the second aspect may be omitted.

[0371] The cantilever 20 of the acoustic transducer 100D includes an upper electrode 30, an intermediate electrode 50, and a lower electrode 40. The upper electrode 30 includes a first upper electrode 31 and a second upper electrode 32. An electrode-free region 81 is formed between the first upper electrode 31 and the second upper electrode 32. The lower electrode 40 includes a first lower electrode 41 and a second lower electrode 42. An electrode-free region 82 is formed between the first lower electrode 41 and the second lower electrode 42. The intermediate electrode 50 is formed continuously from the fixed end 22 to the free end 21.

[0372] The cantilever 20 has a detection region 23 and a non-detection region 24. The detection region 23 is the region where the first lower electrode 41, the intermediate electrode 50, and the first upper electrode 31 overlap in the Z-axis direction. In the acoustic transducer 100D, piezoelectric output charge is generated between the first upper electrode 31 and the intermediate electrode 50. In the acoustic transducer 100D, piezoelectric output charge is generated between the first lower electrode 41 and the intermediate electrode 50. The length L21 of the detection region 23 is the length of the first upper electrode 31 in the X-axis direction.

[0373] [Operation and Effect of the Acoustic Conversion Device 100D According to the Fourth Embodiment of the Second Aspect]

[0374] The acoustic transducer 100D of the fourth embodiment of the second aspect also exhibits the same operational effects as the acoustic transducer 100 of the first embodiment of the second aspect. In the acoustic transducer 100D, the upper electrode 30 and the lower electrode 40 are divided, but the intermediate electrode 50 does not need to be divided.

[0375] In the acoustic transducer 100, at least one of the upper electrode 30, the lower electrode 40, and the intermediate electrode 50 may be divided. In the acoustic transducer 100, the upper electrode 30 may be divided, but the lower electrode 40 and the intermediate electrode 50 may not be divided. In the acoustic transducer 100, the lower electrode 40 may be divided, but the upper electrode 30 and the intermediate electrode 50 may not be divided.

[0376] [Acoustic Converter 100E According to Fifth Embodiment of Second Aspect]

[0377] Next, an acoustic transducer 100E according to a fifth embodiment of the second aspect will be described. Figure 29 This is a perspective view illustrating an acoustic transducer 100E according to a fifth embodiment of the second aspect. Figure 29 The acoustic converter device 100E of the fifth embodiment of the second aspect shown in FIG. Figure 25 The sound transducer 100B according to the second embodiment of the second embodiment shown differs in that it includes four cantilevers 20 and has a different shape of the fixing frame 10. Furthermore, in the description of the sound transducer 100E according to the fifth embodiment of the second embodiment, descriptions that are identical to those of the sound transducers 100 and 100B according to the second embodiment described above may be omitted.

[0378] The sound conversion device 100E includes a fixed frame 10. The fixed frame 10 has multiple frame portions 10B. The multiple frame portions 10B are arranged in the X-axis direction. The multiple frame portions 10B include a common portion 10E. The common portion 10E extends in the Y-axis direction at the center of the fixed frame 10. A pair of cantilevers 20 is formed within each of the multiple frame portions 10B. The free ends 21 of the pair of cantilevers 20 are arranged to face each other. The cantilevers 20 extending from the common portion 10E extend in opposite directions.

[0379] [Operation and Effect of the Acoustic Conversion Device 100E According to the Fifth Embodiment of the Second Aspect]

[0380] The sound transducer 100E of the fifth embodiment of the second aspect also achieves the same effects as the sound transducer 100 of the first embodiment of the second aspect described above. The sound transducer 100E of the fifth embodiment of the second aspect includes four cantilevers 20, thereby improving sensitivity. The sound transducer 100E may include multiple sets of a pair of cantilevers 20. The sound transducer 100E may also include four or more cantilevers 20.

[0381] [Circuit Diagram of Acoustic Converter 100E According to Second Embodiment]

[0382] Next, a circuit diagram of the sound conversion device 100E according to the second embodiment will be described. Figure 30 This is a circuit diagram of an acoustic transducer 100E according to the embodiment of the second aspect. In describing the circuit diagram of the acoustic transducer 100E, descriptions similar to those of the acoustic transducers 100 and 100B to 100D according to the embodiment of the second aspect described above may be omitted.

[0383] like Figure 30 As shown, an acoustic transducer device 100E includes a MEMS microphone chip 101. The MEMS microphone chip 101 is equipped with multiple cantilevers 20A, 20B, 20C, and 20D. The MEMS microphone chip 101 may also include four or more cantilevers 20. The cantilevers 20A, 20B, 20C, and 20D each have an upper electrode 30, a lower electrode 40, and an intermediate electrode 50. The acoustic transducer device 100 is capable of detecting piezoelectric output charges between the upper electrode 30 and the intermediate electrode 50, as well as between the lower electrode 40 and the intermediate electrode 50. The multiple cantilevers 20A, 20B, 20C, and 20D are connected in series.

[0384] The MEMS microphone chip 101 also has pads 13 and 14. A cantilever 20A is connected to pad 13, and a cantilever 20D is connected to pad 14. The acoustic converter 100E includes an IC 102 connected to pad 13. IC 102 is an amplifier that amplifies the output signal from cantilever 20. IC 102 may also be configured to perform analog-to-digital (A / D) conversion after amplifying the output signal from cantilever 20. IC 102 may also be configured to perform fixed-level adjustment of the output level of the amplified signal.

[0385] [Acoustic Converter 100F According to Sixth Embodiment of Second Aspect]

[0386] Next, an acoustic transducer 100F according to a sixth embodiment of the second aspect will be described. Figure 31 This is a plan view illustrating an acoustic transducer 100F according to a sixth embodiment of the second aspect. Figure 31 The sound converter 100F of the sixth embodiment of the second aspect shown in FIG. Figure 25 The sound transducer device 100B of the second embodiment of the second aspect shown differs in that it includes a pair of cantilevers 20 (cantilevers 20A, 20F) having different widths W20 and W20F, and in the shape of the fixing frame 10F. Furthermore, in the description of the sound transducer device 100F of the sixth embodiment, descriptions that overlap with those of the sound transducers 100 and 100B of the second embodiment described above may be omitted.

[0387] The acoustic transducer 100F includes cantilevers 20A and 20F as a pair of cantilevers 20. As described above, the cantilevers 20A and 20F have the same laminated structure as the cantilever 20, including an upper electrode 30, a lower electrode 40, an intermediate electrode 50, a first piezoelectric layer 61, and a second piezoelectric layer 62. The cantilever 20A has a detection region 23 and a non-detection region 24. The cantilever 20F has a detection region 23F and a non-detection region 24F.

[0388] Width W20F of cantilever 20F is greater than width W20 of cantilever 20A (W20F>W20). Width W20F corresponds to the width of first upper electrode 31 in detection region 23F. Width W20 corresponds to the width of first upper electrode 31 in detection region 23. The capacitive element of cantilever 20A is connected in series with the capacitive element of cantilever 20F.

[0389] The length L20 of the cantilever 20A may be equal to the length L20F of the cantilever 20F (L20=L20F). The length L21 of the detection region 23 of the cantilever 20A may be substantially equal to the length L21F of the detection region 23F of the cantilever 20F (L21≈L21F).

[0390] The shape of the fixing frame 10F corresponds to the shapes of the cantilevers 20A and 20F. The slits 71 formed on both sides of the cantilever 20A and the slits 71 formed on both sides of the cantilever 20F are arranged at different positions in the Y-axis direction.

[0391] [Operation and Effect of Acoustic Conversion Device 100F According to Sixth Embodiment of Second Aspect]

[0392] The acoustic transducer device 100F of the sixth embodiment of the second aspect also achieves the same operational effects as the acoustic transducer device 100 of the first embodiment of the second aspect described above. In the acoustic transducer device 100F of the sixth embodiment of the second aspect, the widths W20 and W20F of the opposing pair of cantilevers 20A and 20F along the Y-axis direction may be different.

[0393] [Acoustic Converter 100G According to Seventh Embodiment of Second Aspect]

[0394] Next, an acoustic transducer 100G according to a seventh embodiment of the second aspect will be described. Figure 32 This is a cross-sectional view illustrating an acoustic transducer 100G according to a seventh embodiment of the second aspect. Figure 32 The acoustic converter 100G of the seventh embodiment shown in FIG. Figure 24 The acoustic transducer 100 shown differs in that the thickness of the intermediate electrode 50G is thicker than the thickness of the upper electrode 30 and the lower electrode 40. In the description of the acoustic transducer 100G according to the seventh embodiment of the second aspect, descriptions identical to those of the acoustic transducer 100 according to the aforementioned embodiment of the second aspect may be omitted.

[0395] The cantilever 20 of the acoustic transducer 100G includes an upper electrode 30, a lower electrode 40, an intermediate electrode 50G, a first piezoelectric layer 61, and a second piezoelectric layer 62. The intermediate electrode 50G includes a first intermediate electrode 51 and a second intermediate electrode 52. The intermediate electrode 50G is thicker than the upper electrode 30. The intermediate electrode 50G is thicker than the lower electrode 40. The thickness of the intermediate electrode 50G may be the same as the thickness of the first intermediate electrode 51. In the detection region 23, the first intermediate electrode 51 is thicker than the first upper electrode 31 and the first lower electrode 41. The first upper electrode 31 may also have the same thickness as the first lower electrode 41.

[0396] The intermediate electrode 50G is formed to include a neutral plane N20. The neutral plane N20 is a hypothetical plane located, for example, at the center of the upper electrode 30 and the lower electrode 40 in the Z-axis direction when no stress is applied to the cantilever 20. Alternatively, the neutral plane N20 may be a hypothetical plane on which neither compressive nor tensile stress is applied when stress is applied to the cantilever 20.

[0397] [Operation and Effect of Acoustic Converter 100G According to Seventh Embodiment of Second Aspect]

[0398] The acoustic transducer 100G of the seventh embodiment of the second aspect also achieves the same effects as the acoustic transducer 100 of the first embodiment of the second aspect described above. In the acoustic transducer 100G of the seventh embodiment of the second aspect, the intermediate electrode 50 is thicker than the upper electrode 30 and the lower electrode 40. The intermediate electrode 50 is positioned at a position including the neutral plane N20. This positions the first and second piezoelectric layers 61 and 62 outward in the thickness direction. Therefore, when stress is generated in the cantilever 20, the deformation of the first and second piezoelectric layers 61 and 62 can be increased. As a result, the acoustic transducer 100G can achieve higher sensitivity, smaller size, and a higher SNR (S / N ratio).

[0399] [Acoustic Converter 200 According to the Eighth Embodiment of the Second Aspect]

[0400] Next, an acoustic transducer 200 according to an eighth embodiment of the second aspect will be described. Figure 33 It is a plan view illustrating an acoustic transducer device 200 according to an eighth embodiment of the second aspect. Figure 34 This is a perspective view illustrating an acoustic transducer 200 according to an eighth embodiment of the second aspect. Figure 35 This is a perspective view illustrating an acoustic transducer 200 according to an eighth embodiment of the second aspect from the bottom side. Figure 36 This is a cross-sectional view illustrating an acoustic conversion device 200 according to the eighth embodiment of the second embodiment. In each figure, the X-axis, Y-axis, and Z-axis directions may be shown as being orthogonal to each other. The X-axis, Y-axis, and Z-axis directions may not be orthogonal. The X-axis, Y-axis, and Z-axis directions may be arbitrary directions. The X-axis direction is an example of a first direction. The Y-axis direction is an example of a direction intersecting the first direction. In the description of the acoustic conversion device 200 according to the eighth embodiment of the second embodiment, descriptions identical to those of the acoustic conversion device 100 according to the aforementioned second embodiment will be omitted.

[0401] [Supporting substrate 211]

[0402] The sound conversion device 200 includes a supporting substrate (fixed frame) 211 and a vibration plate (piezoelectric element) 220. The supporting substrate 211 may also be rectangular when viewed in the Z-axis direction. The thickness direction of the supporting substrate 211 is along the Z-axis direction. The supporting substrate 211 has an upper surface 211a and a lower surface 211b that are opposite to each other in the Z-axis direction. An opening 221 is formed in the supporting substrate 211. The opening 221 is formed in a manner that penetrates the supporting substrate 211 in the Z-axis direction. The supporting substrate 211 is formed, for example, from a silicon wafer. The opening 221 is formed in a manner that is circular when viewed in the Z-axis direction.

[0403] [Vibration plate 220]

[0404] The vibration plate 220 has a piezoelectric film. The vibration plate 220 is formed in a manner covering the opening 221. The vibration plate 220 is formed in a manner that is circular when viewed in the Z-axis direction. The outer periphery 222 of the vibration plate 220 is the fixed end of the vibration plate 220 and is fixed to the upper surface 211a of the support substrate 211. As described later, the vibration plate 220 has a first detection area 324, a non-detection area 325, and a second detection area 326. The vibration plate 220 can also be called a "diaphragm". In addition, the opening 221 is not limited to a circle and can also be an ellipse or other shapes.

[0405] [Piezoelectric film]

[0406] The piezoelectric film serving as the vibration plate 220 is deformed according to sound pressure and generates electric charge. Figure 37 This is an enlarged cross-sectional view illustrating an enlarged piezoelectric film. The piezoelectric film includes a lower electrode layer 440, a lower piezoelectric layer (first piezoelectric layer) 460, an intermediate electrode layer 250, an upper piezoelectric layer (second piezoelectric layer) 360, and an upper electrode layer 330. The lower electrode layer 440, the lower piezoelectric layer 460, the intermediate electrode layer 250, the upper piezoelectric layer 360, and the upper electrode layer 330 are stacked in this order.

[0407] [Lower electrode layer 440]

[0408] The lower electrode layer 440 includes lower electrodes 441 to 443 serving as electrode films. The lower electrode layer 440 is positioned near the opening 221 in the Z-axis direction. The lower electrodes 441 to 443 are positioned separately in the X-axis direction. The lower electrode 441 is circular. The lower electrode 441 is positioned near the center C11 of the vibration plate 220 when viewed in the Z-axis direction. The lower electrode 442 is annular when viewed in the Z-axis direction. The lower electrode 442 is radially arranged outside the lower electrode 441. The lower electrode 443 is annular when viewed in the Z-axis direction. The lower electrode 443 is radially arranged outside the lower electrode 442.

[0409] [Electrode non-formation regions 483 and 484]

[0410] In the radial direction of the vibration plate 220 , an electrode-free region 483 is provided between the lower electrodes 441 and 442 . In the radial direction of the vibration plate 220 , an electrode-free region 484 is provided between the lower electrodes 442 and 443 .

[0411] [Lower piezoelectric layer 460]

[0412] The lower piezoelectric layer 460 is a piezoelectric thin film, and is formed on the lower electrode layer 440. The lower piezoelectric layer 460 is formed continuously in the radial direction of the vibration plate 220.

[0413] [Intermediate electrode layer 250]

[0414] The intermediate electrode layer 250 includes intermediate electrodes 251 to 253, which are thin electrode films. The intermediate electrode layer 250 is formed on the lower piezoelectric layer 460. The intermediate electrodes 251 to 253 are spaced apart in the X-axis direction. The intermediate electrode 251 is circular. When viewed in the Z-axis direction, the intermediate electrode 251 is positioned near the center C11 of the vibration plate 220. The intermediate electrode 252 is annular when viewed in the Z-axis direction. The intermediate electrode 252 is radially outside the intermediate electrode 251. The intermediate electrode 253 is annular when viewed in the Z-axis direction. The intermediate electrode 253 is radially outside the intermediate electrode 252.

[0415] [Electrode non-formation regions 281, 282]

[0416] In the radial direction of the vibration plate 220 , an electrode-free region 281 is provided between the intermediate electrodes 251 and 252 . In the radial direction of the vibration plate 220 , an electrode-free region 282 is provided between the intermediate electrodes 252 and 253 .

[0417] [Upper piezoelectric layer 360]

[0418] The upper piezoelectric layer 360 is a piezoelectric thin film, and is formed on the intermediate electrode layer 250. The upper piezoelectric layer 360 is formed continuously in the radial direction of the vibration plate 220.

[0419] [Upper electrode layer 330]

[0420] The upper electrode layer 330 includes upper electrodes 331 to 333 as electrode films. The upper electrode layer 330 is formed on the upper piezoelectric layer 360. The upper electrodes 331 to 333 are arranged separately in the X-axis direction. The upper electrode 331 is circular. When viewed in the Z-axis direction, the upper electrode 331 is arranged at a position close to the center C11 of the vibration plate 220. The upper electrode 332 is ring-shaped when viewed in the Z-axis direction. The upper electrode 332 is arranged radially outside the upper electrode 331. The upper electrode 333 is ring-shaped when viewed in the Z-axis direction. The upper electrode 333 is arranged radially outside the upper electrode 332.

[0421] [Material and thickness of piezoelectric film]

[0422] The piezoelectric material used as the lower piezoelectric layer 460 and the upper piezoelectric layer 360 may be, for example, aluminum nitride (AlN) or scandium-doped aluminum nitride (ScAlN (Sc: 1 to 60 at%)), or a piezoelectric material having a fluorite structure (hafnium oxide, zirconium oxide, cesium oxide), or a piezoelectric material having a wurtzite structure (zinc oxide, gallium nitride).

[0423] The thickness of the lower piezoelectric layer 460 may be, for example, not less than 100 nm and not more than 1 μm. The material of the lower piezoelectric layer 460 is, for example, ScAlN (Sc: 40 at %), and the thickness of the lower piezoelectric layer 460 may be, for example, 500 nm.

[0424] The thickness of the upper piezoelectric layer 360 is, for example, not less than 100 nm and not more than 1 μm. The material of the upper piezoelectric layer 360 is, for example, ScAlN (Sc: 40 at %), and the thickness of the upper piezoelectric layer 360 is, for example, 500 nm.

[0425] [Material and thickness of electrode film]

[0426] The thickness of the electrode thin films in the upper electrode layer 330, the intermediate electrode layer 250, and the lower electrode layer 440 may be, for example, 5 nm or more and 100 nm or less. The thickness of the electrode thin films may be, for example, 20 nm. The electrode thin films in the upper electrode layer 330, the intermediate electrode layer 250, and the lower electrode layer 440 may also be formed with different thicknesses.

[0427] The material of the electrode thin films in the upper electrode layer 330, the intermediate electrode layer 250, and the lower electrode layer 440 may be formed, for example, from at least one of gold, platinum, tungsten, aluminum, copper, molybdenum, ruthenium, titanium, chromium, and nickel, or an alloy containing at least one of these. The electrode thin films in the upper electrode layer 330, the intermediate electrode layer 250, and the lower electrode layer 440 may be formed from the same material or different materials.

[0428] [First Detection Area, Non-Detection Area, and Second Detection Area]

[0429] like Figure 36 as well as Figure 37 As shown, diaphragm 220 includes first detection regions 323, 423, non-detection regions 324, 424, and second detection regions 325, 425. First detection regions 323, 423, and second detection regions 325, 425 are regions capable of detecting physical quantities. Non-detection regions 324, 424 are regions where no physical quantity is detected. For example, the physical quantity is sound pressure.

[0430] The first detection region 323 is the region where the intermediate electrode 251, upper piezoelectric layer 360, and upper electrode 331 overlap in the Z-axis direction. The first detection region 423 is the region where the lower electrode 441, lower piezoelectric layer 460, and intermediate electrode 251 overlap in the Z-axis direction. The acoustic transducer 200 can detect the piezoelectric output charge between the lower electrode 441 and the intermediate electrode 251. The acoustic transducer 200 can detect the piezoelectric output charge between the intermediate electrode 251 and the upper electrode 331.

[0431] Non-detection region 324 includes the area where the intermediate electrode 252, upper piezoelectric layer 360, and upper electrode 332 overlap in the Z-axis direction. Non-detection region 424 includes the area where the lower electrode 442, lower piezoelectric layer 460, and intermediate electrode 252 overlap in the Z-axis direction. The acoustic transducer 200 cannot detect the piezoelectric output charge between the lower electrode 442 and the intermediate electrode 252. The acoustic transducer 200 cannot detect the piezoelectric output charge between the intermediate electrode 252 and the upper electrode 332.

[0432] The second detection region 325 is the region where the intermediate electrode 253, the upper piezoelectric layer 360, and the upper electrode 333 overlap in the Z-axis direction. The second detection region 425 is the region where the lower electrode 443, the lower piezoelectric layer 460, and the intermediate electrode 253 overlap in the Z-axis direction. The acoustic transducer 200 can detect the piezoelectric output charge between the lower electrode 443 and the intermediate electrode 253. The acoustic transducer 200 can detect the piezoelectric output charge between the intermediate electrode 253 and the upper electrode 333.

[0433] First detection regions 323 and 423 are formed near the center of vibration plate 220. Non-detection regions 324 and 424 are formed radially outward of first detection regions 323 and 423 in vibration plate 220. Second detection regions 325 and 425 are formed radially outward of non-detection regions 324 and 424 in vibration plate 220.

[0434] [Outer diameters of the first detection area 323, the non-detection area 324, and the second detection area 325]

[0435] like Figure 33 As shown, the outer diameter Φ323 of the first detection area 323 is, for example, 0.59 mm. The outer diameter Φ324 of the non-detection area 324 is, for example, 0.81 mm. The outer diameter Φ325 of the second detection area 325 is, for example, 1 mm.

[0436] [Split Position]

[0437] like Figure 37 As shown, electrode non-formation regions 483 and 484 are formed in the lower electrode layer 440 , electrode non-formation regions 281 and 282 are formed in the intermediate electrode layer 250 , and electrode non-formation regions 381 and 382 are formed in the upper electrode layer 330 .

[0438] The electrode non-formed regions 281 , 282 , 381 , 382 , 483 , and 484 may also be referred to as “dividing positions.” These electrode non-formed regions 281 , 282 , 381 , 382 , 483 , and 484 are arranged at different positions in the radial direction of the vibration plate 220 .

[0439] The electrode non-formation region 381 is arranged radially inward of the vibration plate 220 relative to the electrode non-formation region 281. The electrode non-formation region 281 is arranged radially inward of the vibration plate 220 relative to the electrode non-formation region 483.

[0440] The electrode non-formation region 382 is arranged outside the electrode non-formation region 282 in the radial direction of the vibration plate 220 . The electrode non-formation region 282 is arranged outside the electrode non-formation region 484 in the radial direction of the vibration plate 220 .

[0441] In the vibration plate 220, the plurality of electrode-free regions 281, 282, 381, 382, ​​483, and 484 are formed at positions that do not overlap when viewed in the Z-axis direction. This prevents a decrease in the strength of the vibration plate 220. Furthermore, piezoelectric thin films are formed in the electrode-free regions 281, 282, 483, and 484.

[0442] The crystallinity of the piezoelectric film above the boundary between the end of the lower electrode 441 and the electrode non-formed region 483 is lower than the crystallinity of the piezoelectric film above the lower electrode 441. Similarly, the crystallinity of the piezoelectric film above the boundary between the electrode and the electrode non-formed region is lower than the crystallinity of the piezoelectric film above the electrode.

[0443] The splitting position, which serves as the electrode-free region 483, is located radially outward from the first detection region 423 of the diaphragm 220. The splitting position, which serves as the electrode-free region 484, is located radially inward from the second detection region 425 of the diaphragm 220. This prevents the crystal growth of the piezoelectric thin film that generates charge from being hindered. In the acoustic transducer 200, the piezoelectric thin film in the first detection region 423 and the second detection region 425, where charge is generated, has high crystallinity.

[0444] The splitting position, which serves as the electrode-free region 281, is located radially outward from the first detection region 323 of the diaphragm 220. The splitting position, which serves as the electrode-free region 282, is located radially inward from the second detection region 325 of the diaphragm 220. This prevents the crystal growth of the piezoelectric thin film that generates charge from being hindered. In the acoustic transducer 200, the piezoelectric thin film in the first detection region 323 and the second detection region 325, where charge is generated, has high crystallinity.

[0445] [Connection of piezoelectric film]

[0446] In the vibrating plate 220, which functions as a piezoelectric film (piezoelectric element), the electrodes of the first detection regions 323 and 423 are electrically connected in parallel. The electrodes of the first detection region 323 include an upper electrode 331 and an intermediate electrode 251. The electrodes of the first detection region 423 include a lower electrode 441 and an intermediate electrode 251. The electrodes of the second detection regions 325 and 425 are electrically connected in parallel. The electrodes of the second detection region 325 include an upper electrode 333 and an intermediate electrode 253. The electrodes of the second detection region 425 include a lower electrode 443 and an intermediate electrode 253.

[0447] The electrodes of the first detection region and the second detection region are electrically connected in series. Specifically, the electrodes are upper electrodes 331 and 333, lower electrodes 441 and 443, or intermediate electrodes 251 and 253.

[0448] [Operation and Effect of the Acoustic Conversion Device 200 According to the Eighth Embodiment of the Second Aspect]

[0449] The acoustic transducer 200 according to the eighth embodiment of the second aspect includes a support substrate (fixing frame) 211 and a vibration plate 220 serving as a piezoelectric element fixed to the support substrate 211. The vibration plate 220 has a plurality of detection regions capable of detecting physical quantities, namely, first detection regions 323 and 423 and second detection regions 325 and 425; and non-detection regions 324 and 424 that do not detect physical quantities. The electrodes of the plurality of detection regions are electrically connected in series.

[0450] In the acoustic transducer 200 of the second embodiment, deformation of the diaphragm 220 is detected, thereby enabling detection of a physical quantity. Acoustic transducer 200 includes first detection regions 323 and 423 and second detection regions 325 and 425. By electrically connecting the electrodes of these multiple detection regions in series, the sensitivity of the diaphragm 220 can be increased.

[0451] In the acoustic transducer device 200 , the piezoelectric element is a vibration plate (diaphragm) 220 , and an outer periphery 222 of the vibration plate 220 (outer periphery of the diaphragm) is a fixed end fixed to the support substrate 211 .

[0452] In the acoustic converter 200, the multiple detection areas include first detection areas 323 and 423, which are located radially closer to the center C11 of the diaphragm 220, and second detection areas 325 and 425, which are located radially farther from the center C11 of the diaphragm 220. Non-detection areas 324 and 424 are formed circumferentially between the inner and outer detection areas.

[0453] In the acoustic transducer 200 of the second embodiment, deformation of the diaphragm 220 generates electric charges corresponding to the diaphragm 220, and the generated electric charges are detected in the first detection regions 323 and 423 and the second detection regions 325 and 425. In the acoustic transducer 200, the electrodes are cut in the radial direction of the diaphragm 220 to form the first detection regions 323 and 423, the non-detection regions 324 and 424, and the second detection regions 325 and 425. This acoustic transducer 200 can improve the sensitivity of detecting electric charges based on sound pressure.

[0454] Figure 38 2 is a side view illustrating the distribution of electric charges generated on the vibration plate 220 that is deformed by sound pressure. In the vibration plate 220 serving as a diaphragm, the outer periphery 222 on the radially outer side is fixed to the support substrate 211. Figure 38 As shown, the area near the inflection point P12 is less likely to deform and the amount of charge generated is small. The inflection point P12 with a small amount of charge generated and the area near it are included in the second detection area 325, 425.

[0455] In contrast, the area near the center C11 of the diaphragm 220 and the outer periphery 222 of the diaphragm 220 deforms significantly, resulting in a higher amount of charge. The center C11 of the diaphragm 220 and its surrounding area are included in the first detection areas 323 and 423. The area near the outer periphery 222 of the diaphragm 220 is included in the second detection areas 325 and 425. In the sound conversion device 200, the area including the inflection point P12, where charge generation is relatively low, is not included in the first detection areas 323 and 423 or the second detection areas 325 and 425. This improves the signal-to-noise ratio (SN / S) of the sound conversion device 200, enabling detection sensitivity for charge.

[0456] [Shape of the End of the Electrode]

[0457] Next, the shape of the end portion of the electrode will be described. Figure 37 As shown, the ends of the upper electrodes 331-333, lower electrodes 441-443, and intermediate electrodes 251-253 may also be tapered. The ends of the electrodes are radially opposed to each other in the vibrating plate 220. The tapered shape of the electrode ends is formed so that the lower side protrudes further than the upper side.

[0458] By tapering the ends of the lower electrodes 441 to 443 in this manner, the steps at the boundaries between the lower electrodes 441 to 443 and the electrode-free regions 483 and 484 can be made gentle. This can suppress a decrease in the crystallinity of the piezoelectric layer 460. The same applies to the boundaries between the other electrodes and the electrode-free regions.

[0459] [Acoustic Converter 200B According to Ninth Embodiment of Second Aspect]

[0460] Next, an acoustic transducer 200B according to a ninth embodiment of the second aspect will be described. Figure 39 It is a plan view illustrating an acoustic transducer 200B according to a ninth embodiment of the second aspect. Figure 40 is a cross-sectional view illustrating an acoustic converter device according to a ninth embodiment of the second aspect, taken along Figure 39 Cross-sectional view of line IX-IX in FIG. Figure 39 as well as Figure 40 The sound conversion device 200B of the ninth embodiment of the second aspect shown in FIG. Figure 33The acoustic transducer 200 of the eighth embodiment of the second embodiment shown differs in the following aspects: a plurality of circumferentially divided upper electrodes 331B and 333B; a plurality of circumferentially divided lower electrodes 441B and 443B; a plurality of circumferentially divided intermediate electrodes 251B and 253B; and radially extending electrode-free regions 385 and 386. In the description of the acoustic transducer 200B of the ninth embodiment of the second embodiment, descriptions identical to those of the acoustic transducer 200 of the eighth embodiment of the second embodiment may be omitted.

[0461] [Laminated body 300B]

[0462] like Figure 40 As shown, the acoustic transducer 200B includes laminates 300B and 400B. The laminate 300B includes an upper electrode layer 330B, a piezoelectric layer 360, and an intermediate electrode layer 250B. The upper electrode layer 330B includes a plurality of upper electrodes 331B divided in the circumferential direction, a circumferentially continuous upper electrode 332, and a plurality of circumferentially divided upper electrodes 333B. The intermediate electrode layer 250B includes a plurality of intermediate electrodes 251B divided in the circumferential direction, a circumferentially continuous intermediate electrode 252, and a plurality of circumferentially divided intermediate electrodes 253B.

[0463] [First detection area 323B]

[0464] The stack 300B includes a first detection region 323B, a non-detection region 324B, and a second detection region 325B. The first detection region 323B includes multiple upper electrodes 331B, a piezoelectric layer 360, and multiple intermediate electrodes 251B. The first detection region 323B includes multiple piezoelectric elements. Each piezoelectric element in the first detection region 323B includes an upper electrode 331B, a piezoelectric layer 360, and an intermediate electrode 251B.

[0465] [Second detection area 325B]

[0466] The second detection region 325B includes a plurality of upper electrodes 333B, a piezoelectric layer 360, and a plurality of intermediate electrodes 253B. The second detection region 325B includes a plurality of piezoelectric elements. In the second detection region 325B, the piezoelectric element includes an upper electrode 333B, a piezoelectric layer 360, and an intermediate electrode 253B.

[0467] like Figure 39 As shown, electrode non-formation regions 381 and 383 and electrode non-formation regions 385 and 386 are formed in the upper electrode layer 330B.

[0468] [Electrode non-formation region 385]

[0469] Electrode-free regions 385 divide the upper electrode into multiple sections within first detection region 323B. Electrode-free regions 385 extend radially from the center of diaphragm 220B. Multiple electrode-free regions 385 are circumferentially spaced evenly apart. The areas of the multiple upper electrodes 331B are substantially equal. For example, the sound conversion device 200B includes ten upper electrodes 331B.

[0470] [Electrode non-formation region 386]

[0471] Electrode non-formation region 386 divides the upper electrode into multiple parts in second detection region 325B. Electrode non-formation region 386 extends radially from electrode non-formation region 382 toward outer peripheral edge 222 of vibration plate 220. Multiple electrode non-formation regions 386 are arranged at equal intervals in the circumferential direction.

[0472] [Laminated body 400B]

[0473] like Figure 40 As shown, the stack 400B includes an intermediate electrode layer 250B, a piezoelectric layer 460, and a lower electrode layer 440B. The intermediate electrode layer 250B serves as both the stack 300B and the stack 400B. The lower electrode layer 440B includes a plurality of lower electrodes 441B divided in the circumferential direction, a circumferentially continuous lower electrode 442, and a plurality of lower electrodes 443B divided in the circumferential direction.

[0474] [First detection area 423B]

[0475] The stack 400B includes a first detection region 423B, a non-detection region 424, and a second detection region 425B. The first detection region 423B includes multiple intermediate electrodes 251B, a piezoelectric layer 460, and multiple lower electrodes 441B. The first detection region 423B includes multiple piezoelectric elements. In the first detection region 423B, the piezoelectric elements include intermediate electrodes 251B, a piezoelectric layer 460, and lower electrodes 441B. In the first detection region 423B, the areas of the multiple lower electrodes 441B are substantially equal.

[0476] [Second detection area 425B]

[0477] Second detection region 425B includes a middle electrode 253B, a piezoelectric layer 460, and multiple lower electrodes 443B. Second detection region 425B includes multiple piezoelectric elements. In second detection region 425B, the piezoelectric elements include a middle electrode 253B, a piezoelectric layer 460, and lower electrodes 443B. In second detection region 425B, the areas of the multiple lower electrodes 443B are substantially equal.

[0478] Like the upper electrode layer 330B of the stacked body 300B, the lower electrode layer 440B and the intermediate electrode layer 250B of the stacked body 400B include electrode-free regions extending in the radial direction.

[0479] [Electrostatic Capacitance of Piezoelectric Element]

[0480] In the stacked body 300B, the capacitances of the plurality of piezoelectric elements arranged in the circumferential direction of the vibration plate 220 are substantially equal to each other. In the stacked body 400B, the capacitances of the plurality of piezoelectric elements arranged in the circumferential direction of the vibration plate 220 are substantially equal to each other.

[0481] [Series connection of multiple piezoelectric elements]

[0482] In the vibration plate 220B, a plurality of piezoelectric elements arranged in the circumferential direction and the radial direction are electrically connected in series.

[0483] [Operation and Effect of the Acoustic Conversion Device 200B According to the Ninth Embodiment of the Second Aspect]

[0484] The sound transducer 200B according to the ninth embodiment of the second aspect also exhibits the same operational effects as those of the sound transducer 200 according to the eighth embodiment of the second aspect described above.

[0485] In the acoustic transducer 200B, the multiple detection areas include first detection areas 323B and 423B, which are located radially closer to the center C11 of the diaphragm 220B; and second detection areas 325B and 425B, which are located radially farther from the center C11 of the diaphragm 220B. The non-detection areas 324 and 424 include electrode-free areas 381 and 382, ​​which are formed circumferentially between the inner and outer detection areas; and multiple electrode-free areas 385 and 386, which extend radially along the diaphragm and are spaced apart circumferentially.

[0486] According to such an acoustic transducer 200B, by including the electrode non-formation regions 385 and 386 extending in the radial direction, the electrode in the detection region can be divided into a plurality of parts.

[0487] [Modification of the Acoustic Conversion Device 200B According to the Ninth Embodiment of the Second Aspect]

[0488] In the acoustic transducer 200B, the diaphragm (piezoelectric element) 220B includes a piezoelectric film, which includes a lower electrode layer 440B; a lower piezoelectric layer 460 formed on the lower electrode layer 440B; an intermediate electrode layer 250 formed on the lower piezoelectric layer 460; an upper piezoelectric layer 360 formed on the intermediate electrode layer 250B; and an upper electrode layer 330 formed on the upper piezoelectric layer 360. Between the plurality of detection regions (first detection regions 323B and 423B and second detection regions 325B and 425B) are located electrode-free regions (first electrode-free regions) where the upper and lower electrodes are not formed, or electrode-free regions (second electrode-free regions) where the intermediate electrodes are not formed.

[0489] In the acoustic conversion device 200B, when electrode-non-formation regions (first electrode-non-formation regions) are formed on the upper and lower electrodes, electrode-non-formation regions (second electrode-non-formation regions) do not need to be formed on the intermediate electrode. In the acoustic conversion device 200B, when electrode-non-formation regions (second electrode-non-formation regions) are formed on the intermediate electrode, electrode-non-formation regions (first electrode-non-formation regions) 381, 382, ​​483, and 484 do not need to be formed on the upper and lower electrodes.

[0490] Furthermore, within the detection region, the upper electrode, the intermediate electrode, and the lower electrode may be divided circumferentially. The upper electrode division position (electrode non-formed region) may differ from the intermediate electrode division position in the circumferential direction. Similarly, the lower electrode division position may differ from the intermediate electrode division position in the circumferential direction.

[0491] [Circuit Diagram of Acoustic Conversion Device 200B According to Ninth Embodiment of Second Aspect]

[0492] Next, a circuit diagram of an acoustic transducer 200B according to a ninth embodiment of the second aspect will be described. Figure 41 This is a circuit diagram of an acoustic transducer 200B according to a ninth embodiment of the second aspect.

[0493] like Figure 41 As shown, the acoustic transducer 200B includes a MEMS microphone chip 201. The MEMS microphone chip 201 carries a vibration plate 220B. The vibration plate 220B includes a plurality of first detection areas 323B and 423B and second detection areas 325B and 425B.

[0494] The multiple first detection regions 323B and 423B include an upper electrode 331B, an intermediate electrode 251B, and a lower electrode 441B. The multiple second detection regions 325B and 425B include an upper electrode 333B, an intermediate electrode 253B, and a lower electrode 443B. The upper electrode 331B includes n circumferentially divided upper electrodes 331B-1, 331B-2, ..., 331B-n. n is a natural number. The same applies to the other upper, intermediate, and lower electrodes.

[0495] In the first detection regions 323B and 423B of the acoustic transducer 200B, piezoelectric output charges between the upper electrode 331B and the intermediate electrode 251B, and between the intermediate electrode 251B and the lower electrode 441B can be detected. Plural piezoelectric elements arranged in the circumferential direction are connected in series.

[0496] In the second detection regions 325B and 425B of the acoustic transducer 200B, piezoelectric output charges between the upper electrode 333B and the intermediate electrode 253B, and between the intermediate electrode 253B and the lower electrode 443B can be detected.

[0497] The MEMS microphone chip 201 also has pads 213 and 214. Multiple electrodes of piezoelectric elements are connected to these pads. The sound converter 200B includes an IC 202 connected to the pads 213. IC 202 is an amplifier that amplifies the output signal of the piezoelectric element of the vibration plate 220B. Alternatively, IC 202 may also be configured to amplify the output signal of the piezoelectric element of the vibration plate 220B and then perform analog-to-digital conversion.

[0498] The polarity of the charge generated in the second detection regions 325B and 425B is opposite to the polarity of the charge generated in the first detection regions 323B and 423B. Therefore, the wiring in the second detection regions 325B and 425B and the first detection regions 323B and 423B are connected in series in reverse order.

[0499] [Electrode connection]

[0500] In the acoustic transducer 200B, the upper electrodes 331B and the intermediate electrodes 251B of the plurality of first detection regions 323B may be electrically connected in series. Similarly, the upper electrodes 333B and the intermediate electrodes 253B of the plurality of second detection regions 325B may be electrically connected in series.

[0501] In the acoustic transducer 200B, the lower electrodes 441B and the intermediate electrodes 251B of the plurality of first detection regions 423B may be electrically connected in series. Similarly, the lower electrodes 433B and the intermediate electrodes 253B of the plurality of second detection regions 425B may be electrically connected in series.

[0502] In the acoustic conversion device 200B, the upper electrodes and the lower electrodes of the plurality of detection areas may be electrically connected in parallel.

[0503] [Regarding the relationship between the sensing area diameter ratio and the normalized SNR]

[0504] Next, the relationship between the sensing area diameter ratio and the normalized SNR will be described. Figure 42 It is a graph showing the relationship between the ratio of the sensing area diameter and the normalized SNR. Figure 42 In FIG. 5 , the horizontal axis represents the sensing area diameter ratio [%], and the vertical axis represents the normalized SNR [%]. Figure 42 The graph shown is a representation of Figure 33 FIG. 1 is a graph showing the relationship between the sensor area diameter ratio and the normalized SNR in the acoustic transducer 200 according to the eighth embodiment of the second aspect.

[0505] The "sensing area ratio" can be expressed by the following formula (1).

[0506] Sensing area ratio = (electrode separation radius / diaphragm radius) × 100···(1)

[0507] The “electrode separation radius” may also be the radius of the inner detection area 323. The “diaphragm radius” may also be the radius of the vibration plate 220. Figure 33 , a diameter φ323 of the inner detection region 323 and a diameter φ325 of the vibration plate 220 are shown.

[0508] The inner diameter of the opening 221 covered by the vibration plate 220 is set to 100% of the sensing area diameter ratio. The normalized SNR is set to 100% when the electrode non-formation area is formed at 71%. Figure 33 In , “0” indicates the position of the boundary between the inner detection area 323 and the non-detection area 324. Figure 33 In FIG. 3 , “×” indicates the position of the boundary between the outer detection area 325 and the non-detection area 324 .

[0509] The SNR normalized value of the inner detection area 323 is a value obtained when the boundary between the outer detection area 325 and the non-detection area 324 is set to 71% and the outer diameter Φ323 of the inner detection area 323 is changed.

[0510] The SNR normalized value of the outer detection area 325 is a value obtained when the boundary between the inner detection area 323 and the non-detection area 324 is set to 71% and the inner diameter Φ324 of the outer detection area 325 is changed.

[0511] exist Figure 42 In the example shown, the SNR normalized value of the inner detection area 323 reaches a maximum at point P21. The sensing area diameter ratio at point P21 is 59%.

[0512] exist Figure 42 In the example shown, the SNR normalized value of the outer detection area 325 reaches a maximum at point P22. The sensing area diameter ratio at point P22 is 81%.

[0513] When the sensing area diameter ratio of the inner detection area 323 is 44% or more and 71% or less, the normalized SNR value is 100% or more. When the sensing area diameter ratio of the inner detection area 323 is 49% or more and 67% or less, the normalized SNR value is 104% or more. When the sensing area diameter ratio of the inner detection area 323 is 51% or more and 65% or less, the normalized SNR value is 106% or more.

[0514] The sensing area diameter ratio of the inner detection region 323 is preferably 44% to 71%, more preferably 49% to 67%, and even more preferably 51% to 65%.

[0515] When the sensing area diameter ratio of the outer detection area 325 is 71% or more and 89% or less, the normalized SNR value is 100% or more. When the sensing area diameter ratio of the outer detection area 325 is 75% or more and 87% or less, the normalized SNR value is 104% or more. When the sensing area diameter ratio of the outer detection area 325 is 78% or more and 84% or less, the normalized SNR value is 106% or more.

[0516] The sensing area diameter ratio of the outer detection region 325 is preferably 71% to 89%, more preferably 75% to 87%, and even more preferably 78% to 84%.

[0517] The case where the sensing area diameter ratio of the inner detection region 323 is 71% and the sensing area diameter ratio of the outer detection region 325 is 71% may also be a case where the electrode division position exists at the 71% position.

[0518] In the acoustic conversion device 200, when the sensing area diameter ratio of the outer detection area 325 is 71% or more and 89% or less, the sensing area diameter ratio of the inner detection area 323 may be set to a value outside the range of 44% or more and 71% or less. In such a case, the normalized SNR value may be higher.

[0519] In the acoustic conversion device 200, when the sensing area diameter ratio of the inner detection area 323 is 44% or more and 71% or less, the sensing area diameter ratio of the outer detection area 325 may be set to a value outside the range of 71% or more and 89% or less. In such a case, the normalized SNR value may be higher.

[0520] [Acoustic Converter 100 According to First Embodiment of Third Aspect]

[0521] Figure 43 This is a perspective view illustrating the acoustic transducer 100 according to the first embodiment of the third aspect. Figure 44 This is a cross-sectional view illustrating the acoustic transducer according to the first embodiment of the third aspect. Figure 45 20A. The figures sometimes illustrate mutually orthogonal X-axis, Y-axis, and Z-axis directions. The X-axis, Y-axis, and Z-axis directions may not be orthogonal. The X-axis, Y-axis, and Z-axis directions may be arbitrary directions. The X-axis direction is an example of a first direction. The Y-axis direction is a direction intersecting the first direction.

[0522] Figure 43 as well as Figure 44 The acoustic converter 100 shown is a piezoelectric acoustic converter having a piezoelectric element (piezoelectric film). The acoustic converter 100 may be, for example, a microphone (MEMS microphone). The acoustic converter 100 may also be used for noise cancellation purposes. The acoustic converter 100 may also be TWS (Ture wireless stereo) or a vehicle-mounted device installed in a car. The acoustic converter 100 may also be used as a hearing aid, for example. The acoustic converter 100 may be used for any purpose as long as it can detect physical quantities. The physical quantity may be, for example, sound pressure.

[0523] [Fixed frame 10]

[0524] The sound conversion device 100 includes a fixed frame 10 and a pair of cantilevers 20. The fixed frame 10 is a rectangular frame when viewed in the Z-axis direction. The length of the fixed frame 10 in the X-axis direction is shorter than the length of the fixed frame 10 in the Y-axis direction. The fixed frame 10 includes a substrate 11 and an insulating film 12. The insulating film 12 is formed on the substrate 11. Figure 44 As shown, a cavity (opening) 13 is formed in the substrate 11. The cavity 13 is formed so as to penetrate the substrate 11 in the Z-axis direction. The insulating film 12 covers the upper surface of the substrate 11. The insulating film 12 is arranged between the substrate 11 and the cantilever 20 in the Z-axis direction.

[0525] [Cantilever 20]

[0526] The pair of cantilevers 20 includes a piezoelectric film and extends from the fixed frame 10 toward the inside of the fixed frame 10 along the X-axis direction. One end of the cantilever 20 is a fixed end 22 and the other end is a free end 21.

[0527] The pair of cantilevers 20 includes cantilevers 20A and 20B disposed facing each other in the X-axis direction. The cantilever 20A is an example of a first cantilever, and the cantilever 20B is an example of a second cantilever. The free ends 21 of the pair of cantilevers 20 face each other.

[0528] like Figure 43 As shown, a pair of slits 71 and a slit 72 are formed around cantilevers 20A and 20B. Slit 71 is a gap formed between the fixed frame 10 and the cantilever 20, penetrating the substrate in the Z-axis direction. The pair of slits 71 extend in the X-axis direction and are formed to be separated in the Y-axis direction. Slit 72 is a gap formed between the opposing free ends 21. The fixed end 22 of the cantilever 20 is connected to the fixed frame 10. The width of slits 71 and 72 can be, for example, greater than 100 nm and less than 5 μm. The width of slits 71 and 72 can also be, for example, 0.5 μm.

[0529] exist Figure 44 , a cross section along the XZ plane of the cantilever 20 (20A) and the fixed frame 10 is shown. Figure 45 , a cross section of the cantilever 20 (20A) along the XZ plane is shown. Figure 44 As shown, the piezoelectric film of the cantilever 20 includes a lower electrode 40 , a first piezoelectric layer 61 , an intermediate electrode 50 , a second piezoelectric layer 62 , and an upper electrode 30 .

[0530] [Lower electrode 40]

[0531] The lower electrode 40 is an electrode thin film and is formed on the lower surface of the cantilever 20. The lower electrode 40 is formed continuously in the X-axis direction.

[0532] [First Piezoelectric Layer 61]

[0533] The first piezoelectric layer 61 is a piezoelectric thin film, and is formed on the lower electrode 40. The first piezoelectric layer 61 is formed continuously in the X-axis direction and the Y-axis direction.

[0534] [Intermediate electrode 50]

[0535] The intermediate electrode 50 is an electrode thin film formed on the first piezoelectric layer 61. The intermediate electrode 50 is formed continuously in the X-axis direction and the Y-axis direction. The thickness T50 of the intermediate electrode 50 will be described later.

[0536] [Second piezoelectric layer 62]

[0537] The second piezoelectric layer 62 is a piezoelectric thin film, and is formed on the intermediate electrode 50. The second piezoelectric layer 62 is formed continuously in the X-axis direction and the Y-axis direction.

[0538] [Upper electrode 30]

[0539] The upper electrode 30 is an electrode thin film, and is formed on the second piezoelectric layer 62. The upper electrode 30 is formed continuously in the X-axis direction and the Y-axis direction.

[0540] The upper electrode 30 and the lower electrode 40 are spaced apart in the Z-axis direction. The intermediate electrode 50 is disposed between the lower electrode 40 and the upper electrode 30 in the Z-axis direction. The first piezoelectric layer 61 is sandwiched between the lower electrode 40 and the intermediate electrode 50 in the Z-axis direction. The second piezoelectric layer 62 is sandwiched between the intermediate electrode 50 and the upper electrode 30 in the Z-axis direction.

[0541] [Material and thickness of piezoelectric film]

[0542] The material of the first piezoelectric layer 61 and the second piezoelectric layer 62 may be, for example, ScAlN. The material of the first piezoelectric layer 61 may be AlN. Sc may be greater than 0 at% and less than 50 at%. The thickness of the first piezoelectric layer 61 and the second piezoelectric layer 62 may be, for example, greater than 100 nm and less than 1 μm. The thickness of the first piezoelectric layer 61 and the second piezoelectric layer 62 may be, for example, 500 nm. The thickness of the first piezoelectric layer 61 may be the same as the thickness of the second piezoelectric layer 62. The thickness of the first piezoelectric layer 61 may be different from the thickness of the second piezoelectric layer 62.

[0543] The first piezoelectric layer 61 and the second piezoelectric layer 62 may have a fluorite structure (hafnium oxide, zirconium oxide, cesium oxide) or a wurtzite structure (zinc oxide). The material of the first piezoelectric layer 61 and the second piezoelectric layer 62 may be the same or different.

[0544] [Material of electrode film]

[0545] The materials of the upper electrode 30, lower electrode 40, and intermediate electrode 50 may be, for example, Al, Mo, Pt, Ti, etc. The material of the upper electrode 30 and the material of the lower electrode 40 may be the same or different.

[0546] [Thickness of electrode film]

[0547] Figure 45 The thickness T50 of the intermediate electrode 50 shown is thicker than the thicknesses T30 and T40 of the upper electrode 30 or lower electrode 40. The thickness T50 of the intermediate electrode 50 is thicker than the thickness T30 of the upper electrode 30. The thickness T50 of the intermediate electrode 50 is thicker than the thickness T40 of the lower electrode 40. The thickness T30 of the upper electrode 30 may be the same as the thickness T40 of the lower electrode 40. The thickness T30 of the upper electrode 30 is the thickness of the upper electrode 30 along the Z-axis. The thickness T40 of the lower electrode 40 is the thickness of the lower electrode 40 along the Z-axis. The thickness T50 of the intermediate electrode 50 is the thickness of the intermediate electrode 50 along the Z-axis. The thickness T30 of the upper electrode 30 and the thickness T40 of the lower electrode 40 may also be different.

[0548] The thicknesses T30 and T40 of the upper electrode 30 and the lower electrode 40 may be, for example, not less than 5 nm and not more than 100 nm. The thicknesses T30 and T40 of the upper electrode 30 and the lower electrode 40 may be, for example, not less than 50 nm. The thickness T50 of the intermediate electrode 50 may be, for example, not less than 10 nm and not more than 1000 nm. The thickness T50 of the intermediate electrode 50 may be, for example, not less than 10 nm and not more than 1000 nm. The thickness T50 of the intermediate electrode 50 may be, for example, not less than 100 nm. The thickness T50 of the intermediate electrode 50 may be thicker than the sum of the thickness T30 of the upper electrode 30 and the thickness T40 of the lower electrode 40.

[0549] [Ratio of Thickness T50 of Intermediate Electrode 50 to Thickness T20 of Cantilever 20]

[0550] The thickness T50 of the intermediate electrode 50 may be greater than or equal to 10% and less than or equal to 90% of the thickness T20 of the cantilever 20. The thickness T20 of the cantilever 20 is the thickness of the cantilever 20 along the Z-axis direction. The thickness T20 of the cantilever 20 is the total thickness of the thickness T40 of the lower electrode 40, the thickness of the first piezoelectric layer 61, the thickness T50 of the intermediate electrode 50, the thickness of the second piezoelectric layer 62, and the thickness T30 of the upper electrode 30. The thickness T50 of the intermediate electrode 50 may be greater than or equal to 30% and less than or equal to 70% of the thickness T20 of the cantilever 20. The thickness T50 of the intermediate electrode 50 may be greater than or equal to 40% and less than or equal to 60% of the thickness T20 of the cantilever 20. Furthermore, as described above, the thickness T20 of the intermediate electrode 50 is thicker than the thicknesses T30 and T40 of the upper or lower electrodes 30 and 40, respectively.

[0551] [Neutral surface N20]

[0552] The intermediate electrode 50 is positioned at a position including the neutral plane N20. The cantilever 20 may also include the neutral plane N20. For example, the neutral plane N20 may be a surface that does not generate either tensile or compressive forces in the longitudinal direction of the cantilever when the cantilever 20 deflects. The cantilever 20 deflects, for example, when subjected to acoustic pressure. The free end 21 of the cantilever 20 displaces relative to the fixed end 22 in the Z-axis direction.

[0553] For example, when the cantilever 20 is subjected to upward acoustic pressure in the Z-axis direction, the free end 21 displaces upward, causing the cantilever 20 to bend. At this time, a tensile force is generated in the first piezoelectric layer 61 below the intermediate electrode 50, while a compressive force is generated in the second piezoelectric layer 62 above the intermediate electrode 50. The magnitude of the tensile and compressive forces varies depending on the position in the Z-axis direction. The tensile force near the lower electrode 40 is greater than the tensile force near the intermediate electrode 50. The compressive force near the upper electrode 30 is greater than the compressive force near the intermediate electrode 50.

[0554] The neutral plane N20 is located near the center of the cantilever 20 in the thickness direction. The neutral plane N20 is an imaginary plane along the XY plane when the cantilever 20 is not bent. The intermediate electrode 50 is arranged at a position that includes the neutral plane N20. The center of the intermediate electrode 50 in the Z-axis direction may also be located on the neutral plane N20. In the case where the thickness of the first piezoelectric layer 61 is the same as the thickness of the second piezoelectric layer 62, the thickness T30 of the upper electrode 30 is the same as the thickness T40 of the lower electrode 40, the material of the first piezoelectric layer 61 is the same as the material of the second piezoelectric layer 62, and the material of the upper electrode 30 is the same as the material of the lower electrode 40, the neutral plane N is located at the center of the cantilever 20 in the thickness direction. The neutral plane N does not necessarily have to be located at the center of the cantilever 20 in the thickness direction. Due to the difference in thickness of the first piezoelectric layer 61 and the second piezoelectric layer 62, the difference in material of the first piezoelectric layer 61 and the second piezoelectric layer 62, the difference in thickness T30 and T40 of the upper electrode 30 and the lower electrode 40, and the difference in material of the upper electrode 30 and the lower electrode 40, the neutral plane N20 is located outside the center in the thickness direction of the cantilever 20.

[0555] [Cantilever 20C of Acoustic Converter Device of Comparative Example in Third Aspect]

[0556] Next, refer to Figure 46 Next, a cantilever 20C of an acoustic transducer device according to a comparative example will be described. Figure 46 2 is a cross-sectional view illustrating a cantilever 20C of a comparative example. In the cantilever 20C of the comparative example, the thicknesses T30, T40, and T50C of the upper electrode 30, the lower electrode 40, and the intermediate electrode 50C are the same.

[0557] When acoustic pressure acts on the cantilever 20C, causing it to bend, compressive and tensile forces act on the first and second piezoelectric layers 61 and 62. The magnitude of the tensile and compressive forces varies depending on the position in the Z-axis direction. The tensile force near the lower electrode 40 is greater than the tensile force near the intermediate electrode 50. The compressive force near the upper electrode 30 is greater than the compressive force near the intermediate electrode 50.

[0558] [Relationship between Thickness Ratio of Intermediate Electrode 50 and Voltage]

[0559] Next, refer to Figure 47 The relationship between the thickness ratio of the intermediate electrode 50 and the voltage in the acoustic transducer device 100 according to the first embodiment of the third aspect will be described. Figure 47 is a graph showing the relationship between the thickness ratio of the intermediate electrode 50 and the voltage. Figure 47 In the figure, the horizontal axis represents the thickness ratio [%] of the intermediate electrode 50, and the vertical axis represents the voltage. The thickness ratio of the intermediate electrode 50 is the ratio of the thickness T50 of the intermediate electrode 50 to the thickness T20 of the cantilever 20. The voltage shown on the vertical axis is the voltage generated by the piezoelectric effect in the first piezoelectric layer 61 and the second piezoelectric layer 62. Figure 47 The graph shown may also be a calculation result for the acoustic transducer device 100. The shape of the graph may vary depending on, for example, the material, structure, shape, and circuit configuration of the cantilever 20. For example, the generated voltage when the thickness ratio of the intermediate electrode 50 is 40% to 60% is higher than the generated voltage when the thickness ratio is 20% or less or 80% or more.

[0560] [Shape of cantilever 20]

[0561] As described above, the cantilever 20 has a rectangular shape when viewed in the Z-axis direction. A rectangular cantilever 20 can increase the area of ​​the cantilever 20 within the chip compared to a circular cantilever, thus achieving higher sensitivity. In other words, while maintaining the same sensitivity, the sound transducer 100 can be made more compact compared to conventional devices. This miniaturization of the sound transducer 100 allows for a lower price.

[0562] [Full length of cantilever 20]

[0563] In the acoustic transducer 100, the resonant frequency of the cantilever 20 can be easily changed by changing the overall length of the cantilever 20. During design, increasing the overall length of the cantilever 20 can lower the resonant frequency. The resonant frequency is lower when the overall length of the cantilever 20 is longer than when the overall length of the cantilever 20 is shorter. The overall length of the cantilever 20 may also be the length of the region where the upper electrode 30, lower electrode 40, and intermediate electrode 50 overlap.

[0564] [Width of cantilever 20]

[0565] The width of the cantilever 20 is the width along the Y-axis. The width of the cantilever 20 may also be the width of the region where the upper electrode 30, the lower electrode 40, and the intermediate electrode 50 overlap. In the acoustic transducer 100, by varying the width of the cantilever 20, the sensitivity of the cantilever 20 can be adjusted independently of the resonant frequency. During design, increasing the width of the cantilever 20 can improve sensitivity. A wider cantilever 20 exhibits higher sensitivity than a narrower cantilever.

[0566] [Operation and Effect of the Acoustic Conversion Device 100 According to the First Embodiment of the Third Aspect]

[0567] The sound transducer device 100 of the first embodiment of the third scheme includes: a fixed frame 10; and a cantilever 20, one end of which is a fixed end 22 fixed to the fixed frame 10 and the other end is a free end 21, and extends from the fixed frame 10 toward the inside of the fixed frame 10. The cantilever 20 has: a lower electrode 40; a first piezoelectric layer 61 formed on the lower electrode 40; an intermediate electrode 50 formed on the first piezoelectric layer 61; a second piezoelectric layer 62 formed on the intermediate electrode 50; and an upper electrode 30 formed on the second piezoelectric layer 62. The thickness T50 of the intermediate electrode 50 is thicker than the thicknesses T30 and T40 of the upper electrode 30 or the lower electrode 40.

[0568] In the acoustic transducer device 100, the cantilever 20 deforms in response to sound pressure, generating piezoelectric output charges in the first and second piezoelectric layers 61 and 62, which can then be detected. With this acoustic transducer device 100, portions of the first and second piezoelectric layers 61 and 62 can be positioned in regions where the tensile or compressive forces are greater when the cantilever 20 is flexed, while the intermediate electrode 50 can be positioned in regions where the tensile or compressive forces are less.

[0569] Furthermore, the acoustic transducer 100 is a piezoelectric acoustic transducer and is more resistant to dust and water droplets than conventional electrostatic acoustic transducers.

[0570] Furthermore, the rectangular shape of the acoustic transducer 100 allows for a larger area of ​​the cantilever 20 within the chip, resulting in higher sensitivity. This increased sensitivity allows for miniaturization of the acoustic transducer 100. In the acoustic transducer 100, the resonant frequency can be easily varied by changing the length of the cantilever 20. By varying the width W20 of the detection region 23, the sensitivity can be adjusted regardless of the resonant frequency.

[0571] [Acoustic Converter 100B According to Second Embodiment of Third Aspect]

[0572] Next, an acoustic transducer 100B according to a second embodiment of the third aspect will be described. Figure 48 This is a plan view illustrating an acoustic transducer 100B according to a second embodiment of the third aspect. Figure 49 This is a cross-sectional view illustrating an acoustic transducer 100B according to a second embodiment of the third aspect. Figure 48 as well as Figure 49 The sound conversion device 100B of the second embodiment of the third aspect shown in FIG. Figure 43 as well as Figure 44 The acoustic transducer 100 according to the first embodiment of the third aspect shown differs from the acoustic transducer 100 in that the cantilever 20 includes a detection region 23 and a non-detection region 24. Specifically, the upper electrode 30, the lower electrode 40, and the intermediate electrode 50 are divided in the X-axis direction. Furthermore, in the description of the acoustic transducer 100B according to the second embodiment of the third aspect, descriptions identical to those of the acoustic transducer 100 according to the first embodiment of the third aspect may be omitted.

[0573] [Lower electrode 40]

[0574] The lower electrode 40 is an electrode thin film having a first lower electrode 41 and a second lower electrode 42. The first lower electrode 41 and the second lower electrode 42 are spaced apart in the X-axis direction. An electrode-free region 82, where no electrode is formed, is located between the first lower electrode 41 and the second lower electrode 42. The electrode-free region 82 is formed by etching after forming the lower electrode 40 to remove the electrode. The electrode-free region 82 can also be formed using a lift-off method.

[0575] The first lower electrode 41 is formed on a side closer to the fixed end 22 in the X-axis direction. The second lower electrode 42 is formed on a side closer to the free end 21 in the X-axis direction.

[0576] [Intermediate electrode 50]

[0577] The intermediate electrode 50 is an electrode thin film and includes a first intermediate electrode 51 and a second intermediate electrode 52. The first intermediate electrode 51 and the second intermediate electrode 52 are spaced apart in the X-axis direction. An electrode-free region 83, where no electrode is formed, is located between the first intermediate electrode 51 and the second intermediate electrode 52. The electrode-free region 83 is formed by etching after forming the intermediate electrode 50 to remove the electrode. The electrode-free region 83 can also be formed using a lift-off method.

[0578] The first intermediate electrode 51 is formed on a side closer to the fixed end 22 in the X-axis direction. The second intermediate electrode 52 is formed on a side closer to the free end 21 in the X-axis direction.

[0579] [Upper electrode 30]

[0580] The upper electrode 30 is an electrode thin film having a first upper electrode 31 and a second upper electrode 32. The first upper electrode 31 and the second upper electrode 32 are spaced apart in the X-axis direction. An electrode-free region 81, where no electrode is formed, is located between the first upper electrode 31 and the second upper electrode 32. After forming the upper electrode 30, etching is performed to remove the electrodes, forming the electrode-free region 81. The electrode-free region 81 can also be formed using a lift-off method.

[0581] The first upper electrode 31 is formed on a side closer to the fixed end 22 in the X-axis direction. The second upper electrode 32 is formed on a side closer to the free end 21 in the X-axis direction.

[0582] [Detection Area 23 and Non-Detection Area 24]

[0583] The cantilever 20 includes a detection region 23 capable of detecting a physical quantity and a non-detection region 24 incapable of detecting a physical quantity. The physical quantity may be, for example, sound pressure. The detection region 23 may be a region where the first upper electrode 31, the first intermediate electrode 51, and the first piezoelectric layer 61 overlap in the Z-axis direction. The first upper electrode 31 and the first lower electrode 41 are electrically connected. The acoustic transducer 100 is capable of detecting the piezoelectric output charge between the first upper electrode 31 and the first intermediate electrode 51. The acoustic transducer 100 is capable of detecting the piezoelectric output charge between the first lower electrode 41 and the first intermediate electrode 51.

[0584] The detection region 23 is arranged closer to the fixed end 22 than the non-detection region 24. In other words, the non-detection region 24 is arranged closer to the free end 21 than the detection region 23.

[0585] The non-detection region 24 is a region of the cantilever 20 excluding the detection region 23. The second upper electrode 32, the second intermediate electrode 52, and the second lower electrode 42 are not electrically connected.

[0586] [Thickness of electrode film]

[0587] The thickness T51 of the first intermediate electrode 51 is thicker than the thicknesses T31 and T41 of the first upper electrode 31 or the first lower electrode 41. The thickness T51 of the first intermediate electrode 51 is thicker than the thickness T31 of the first upper electrode 31. The thickness T51 of the first intermediate electrode 51 is thicker than the thickness T41 of the first lower electrode 41. The thickness T31 of the first upper electrode 31 may be the same as the thickness T41 of the first lower electrode 41.

[0588] The thickness T52 of the second intermediate electrode 52 is thicker than the thicknesses T32 and T42 of the second upper electrode 32 or the second lower electrode 42. The thickness T52 of the second intermediate electrode 52 is thicker than the thickness T32 of the second upper electrode 32. The thickness T52 of the second intermediate electrode 52 is thicker than the thickness T42 of the second lower electrode 42. The thickness T32 of the second upper electrode 32 may be the same as the thickness T42 of the second lower electrode 42.

[0589] [Shape of the End of the Electrode]

[0590] The ends of the electrodes in the X-axis direction may also be tapered. The electrodes include an upper electrode 30, a lower electrode 40, and an intermediate electrode 50. The thickness of the ends of the electrodes in the X-axis direction may be thinner than the thickness of the center portion of the electrodes in the X-axis direction. The ends of the electrodes may also be formed at an acute angle. The tapered shape may also be tilted so that the lower end is positioned outward from the upper end in the X-axis direction.

[0591] The end of the electrode can also be arranged inward of the free end 21 in the X-axis direction. In the X-axis direction, the first piezoelectric layer 61 and the second piezoelectric layer 62 can also be formed outside the end of the electrode. The first piezoelectric layer 61 and the second piezoelectric layer 62 can also be connected in the Z-axis direction in the area outside the end of the electrode. In this way, the tapered shape of the end of the electrode can suppress the decrease in the crystallinity of the first piezoelectric layer 61 and the second piezoelectric layer 62. Therefore, in the first piezoelectric layer 61 and the second piezoelectric layer 62, electric charges can be stably generated.

[0592] [Operation and Effect of the Acoustic Conversion Device 100B According to the Second Embodiment of the Third Aspect]

[0593] The acoustic transducer 100B according to the second embodiment of the third aspect also achieves the same operational effects as the acoustic transducer 100 according to the first embodiment of the third aspect described above. In the acoustic transducer 100B according to the second embodiment of the third aspect, the electrodes are cut in the longitudinal direction (X-axis direction) of the cantilever 20 to form the detection region 23 and the non-detection region 24, thereby enhancing sensitivity.

[0594] In addition, in the acoustic conversion device 100, the cantilever 20 has a piezoelectric film, which includes: a lower electrode 40; a first piezoelectric layer 61 formed on the lower electrode 40; an intermediate electrode 50 formed on the first piezoelectric layer 61; a second piezoelectric layer 62 formed on the intermediate electrode 50; and an upper electrode 30 formed on the second piezoelectric layer 62, and between the detection area 23 and the non-detection area 24, there are electrode non-forming areas 82, 83, and 81 in which at least one of the lower electrode 40, the intermediate electrode 50, and the upper electrode 30 is not formed.

[0595] In the acoustic transducer 100 with this structure, the piezoelectric film-forming cantilever 20 deforms, causing piezoelectric output charges generated between the first upper electrode 31 and the first intermediate electrode 51, and between the first lower electrode 41 and the first intermediate electrode 51, in the detection region 23 to connect to the first intermediate electrode 51. In the acoustic transducer 100, electrode-free regions 82, 83, and 81, where no electrode is formed, are formed in at least one of the lower electrode 40, the intermediate electrode 50, and the upper electrode 30, thereby separating the detection region 23 from the non-detection region 24.

[0596] [Acoustic Converter 200 According to the Third Embodiment of the Third Aspect]

[0597] Next, an acoustic transducer 200 according to a third embodiment of the third aspect will be described. Figure 50 It is a plan view illustrating an acoustic transducer device 200 according to a third embodiment. Figure 51 This is a perspective view illustrating an acoustic transducer 200 according to a third embodiment of the third aspect. Figure 52 This is a perspective view illustrating an acoustic transducer device 200 according to a third embodiment of the third aspect from the bottom side. Figure 53 This is a cross-sectional view illustrating a sound conversion device 200 according to a third embodiment of the third embodiment. In each figure, the X-axis, Y-axis, and Z-axis directions may be shown as being orthogonal to each other. The X-axis, Y-axis, and Z-axis directions may not be orthogonal. The X-axis, Y-axis, and Z-axis directions may be arbitrary directions. The X-axis direction is an example of a first direction. The Y-axis direction is an example of a direction intersecting the first direction. In the description of the sound conversion device 200 according to the third embodiment of the third embodiment, descriptions identical to those of the sound conversion device 100 according to the aforementioned third embodiment of the third embodiment are omitted.

[0598] [Supporting substrate 211]

[0599] The sound conversion device 200 includes a supporting substrate (fixed frame) 211 and a vibration plate (piezoelectric element) 220. The supporting substrate 211 may also be rectangular when viewed in the Z-axis direction. The thickness direction of the supporting substrate 211 is along the Z-axis direction. The supporting substrate 211 has an upper surface 211a and a lower surface 211b that are opposite to each other in the Z-axis direction. An opening 221 is formed in the supporting substrate 211. The opening 221 is formed in a manner that penetrates the supporting substrate 211 in the Z-axis direction. The supporting substrate 211 is formed, for example, from a silicon wafer. The opening 221 is formed in a manner that is circular when viewed in the Z-axis direction.

[0600] [Vibration plate 220]

[0601] The vibration plate 220 has a piezoelectric film. The vibration plate 220 is formed in a manner covering the opening 221. The vibration plate 220 is formed in a manner that is circular when viewed in the Z-axis direction. The vibration plate 220 may also include a portion covering the outside of the opening 221. The outer periphery 222 of the vibration plate 220 is the fixed end of the vibration plate 220, which is fixed to the upper surface 211a of the support substrate 211. As described later, the vibration plate 220 has a first detection area 323, a non-detection area 324 and a second detection area 325. The vibration plate 220 may also be called a "diaphragm". In addition, the opening 221 is not limited to a circle, and may also be an ellipse or other shapes.

[0602] [Piezoelectric film]

[0603] The piezoelectric film serving as the vibration plate 220 is deformed according to sound pressure and generates electric charge. Figure 54 This is an enlarged cross-sectional view illustrating an enlarged piezoelectric film. The piezoelectric film includes a lower electrode layer 440, a lower piezoelectric layer (first piezoelectric layer) 460, an intermediate electrode layer 250, an upper piezoelectric layer (second piezoelectric layer) 360, and an upper electrode layer 330. The lower electrode layer 440, the lower piezoelectric layer 460, the intermediate electrode layer 250, the upper piezoelectric layer 360, and the upper electrode layer 330 are stacked in this order.

[0604] [Lower electrode layer 440]

[0605] The lower electrode layer 440 includes lower electrodes 441 to 443 serving as electrode films. The lower electrode layer 440 is positioned near the opening 221 in the Z-axis direction. The lower electrodes 441 to 443 are positioned separately in the X-axis direction. The lower electrode 441 is circular. The lower electrode 441 is positioned near the center C11 of the vibration plate 220 when viewed in the Z-axis direction. The lower electrode 442 is annular when viewed in the Z-axis direction. The lower electrode 442 is radially arranged outside the lower electrode 441. The lower electrode 443 is annular when viewed in the Z-axis direction. The lower electrode 443 is radially arranged outside the lower electrode 442.

[0606] [Electrode non-formation regions 483 and 484]

[0607] In the radial direction of the vibration plate 220 , an electrode-free region 483 is provided between the lower electrodes 441 and 442 . In the radial direction of the vibration plate 220 , an electrode-free region 484 is provided between the lower electrodes 442 and 443 .

[0608] [Lower piezoelectric layer 460]

[0609] The lower piezoelectric layer 460 is a piezoelectric thin film, and is formed on the lower electrode layer 440. The lower piezoelectric layer 460 is formed continuously in the radial direction of the vibration plate 220.

[0610] [Intermediate electrode layer 250]

[0611] The intermediate electrode layer 250 includes intermediate electrodes 251 to 253, which are thin electrode films. The intermediate electrode layer 250 is formed on the lower piezoelectric layer 460. The intermediate electrodes 251 to 253 are spaced apart in the X-axis direction. The intermediate electrode 251 is circular. When viewed in the Z-axis direction, the intermediate electrode 251 is positioned near the center C11 of the vibration plate 220. The intermediate electrode 252 is annular when viewed in the Z-axis direction. The intermediate electrode 252 is radially outside the intermediate electrode 251. The intermediate electrode 253 is annular when viewed in the Z-axis direction. The intermediate electrode 253 is radially outside the intermediate electrode 252.

[0612] [Electrode non-formation regions 281, 282]

[0613] In the radial direction of the vibration plate 220 , an electrode-free region 281 is provided between the intermediate electrodes 251 and 252 . In the radial direction of the vibration plate 220 , an electrode-free region 282 is provided between the intermediate electrodes 252 and 253 .

[0614] [Upper piezoelectric layer 360]

[0615] The upper piezoelectric layer 360 is a piezoelectric thin film, and is formed on the intermediate electrode layer 250. The upper piezoelectric layer 360 is formed continuously in the radial direction of the vibration plate 220.

[0616] [Upper electrode layer 330]

[0617] The upper electrode layer 330 includes upper electrodes 331 to 333 as electrode films. The upper electrode layer 330 is formed on the upper piezoelectric layer 360. The upper electrodes 331 to 333 are arranged separately in the X-axis direction. The upper electrode 331 is circular. When viewed in the Z-axis direction, the upper electrode 331 is arranged at a position close to the center C11 of the vibration plate 220. The upper electrode 332 is ring-shaped when viewed in the Z-axis direction. The upper electrode 332 is arranged radially outside the upper electrode 331. The upper electrode 333 is ring-shaped when viewed in the Z-axis direction. The upper electrode 333 is arranged radially outside the upper electrode 332.

[0618] [Material and thickness of piezoelectric film]

[0619] The piezoelectric material used as the lower piezoelectric layer 460 and the upper piezoelectric layer 360 may be, for example, aluminum nitride (AlN) or scandium-doped aluminum nitride (ScAlN (Sc: 1 to 60 at%)), or a piezoelectric material having a fluorite structure (hafnium oxide, zirconium oxide, cesium oxide), or a piezoelectric material having a wurtzite structure (zinc oxide, gallium nitride).

[0620] The thickness of the lower piezoelectric layer 460 may be, for example, not less than 100 nm and not more than 1 μm. The material of the lower piezoelectric layer 460 is, for example, ScAlN (Sc: 40 at %), and the thickness of the lower piezoelectric layer 460 may be, for example, 500 nm.

[0621] The thickness of the upper piezoelectric layer 360 may be, for example, not less than 100 nm and not more than 1 μm. The material of the upper piezoelectric layer 360 is, for example, ScAlN (Sc: 40 at %), and the thickness of the upper piezoelectric layer 360 may be, for example, 500 nm.

[0622] [Material and thickness of electrode film]

[0623] The thickness of the electrode thin films in the upper electrode layer 330, the intermediate electrode layer 250, and the lower electrode layer 440 may be, for example, 5 nm or more and 100 nm or less. The thickness of the electrode thin films may be, for example, 20 nm. The electrode thin films in the upper electrode layer 330, the intermediate electrode layer 250, and the lower electrode layer 440 may also be formed with different thicknesses.

[0624] The material of the electrode thin films in the upper electrode layer 330, the intermediate electrode layer 250, and the lower electrode layer 440 may be formed, for example, from at least one of gold, platinum, tungsten, aluminum, copper, molybdenum, ruthenium, titanium, chromium, and nickel, or an alloy containing at least one of these. The electrode thin films in the upper electrode layer 330, the intermediate electrode layer 250, and the lower electrode layer 440 may be formed from the same material or different materials.

[0625] [First Detection Area, Non-Detection Area, and Second Detection Area]

[0626] like Figure 53 as well as Figure 54 As shown, diaphragm diaphragm 220 includes first detection regions 323, 423, non-detection regions 324, 424, and second detection regions 325, 425. First detection regions 323, 423, and second detection regions 325, 425 are regions capable of detecting physical quantities. Non-detection regions 324, 424 are regions where no physical quantity is detected. For example, the physical quantity is sound pressure.

[0627] The first detection region 323 is the region where the intermediate electrode 251, upper piezoelectric layer 360, and upper electrode 331 overlap in the Z-axis direction. The first detection region 423 is the region where the lower electrode 441, lower piezoelectric layer 460, and intermediate electrode 251 overlap in the Z-axis direction. The acoustic transducer 200 can detect the piezoelectric output charge between the lower electrode 441 and the intermediate electrode 251. The acoustic transducer 200 can detect the piezoelectric output charge between the intermediate electrode 251 and the upper electrode 331.

[0628] Non-detection region 324 includes the area where the intermediate electrode 252, upper piezoelectric layer 360, and upper electrode 332 overlap in the Z-axis direction. Non-detection region 424 includes the area where the lower electrode 442, lower piezoelectric layer 460, and intermediate electrode 252 overlap in the Z-axis direction. The acoustic transducer 200 cannot detect the piezoelectric output charge between the lower electrode 442 and the intermediate electrode 252. The acoustic transducer 200 cannot detect the piezoelectric output charge between the intermediate electrode 252 and the upper electrode 332.

[0629] The second detection region 325 is the region where the intermediate electrode 253, the upper piezoelectric layer 360, and the upper electrode 333 overlap in the Z-axis direction. The second detection region 425 is the region where the lower electrode 443, the lower piezoelectric layer 460, and the intermediate electrode 253 overlap in the Z-axis direction. The acoustic transducer 200 can detect the piezoelectric output charge between the lower electrode 443 and the intermediate electrode 253. The acoustic transducer 200 can detect the piezoelectric output charge between the intermediate electrode 253 and the upper electrode 333.

[0630] First detection regions 323 and 423 are formed near the center of vibration plate 220. Non-detection regions 324 and 424 are formed radially outward of first detection regions 323 and 423 in vibration plate 220. Second detection regions 325 and 425 are formed radially outward of non-detection regions 324 and 424 in vibration plate 220.

[0631] [Outer diameters of the first detection area 323, the non-detection area 324, and the second detection area 325]

[0632] like Figure 50 As shown, the outer diameter Φ323 of the first detection area 323 is, for example, 0.59 mm. The outer diameter Φ324 of the non-detection area 324 is, for example, 0.81 mm. The outer diameter Φ325 of the second detection area 325 is, for example, 1 mm.

[0633] [Split Position]

[0634] like Figure 54 As shown, electrode non-formation regions 483 and 484 are formed in the lower electrode layer 440 , electrode non-formation regions 281 and 282 are formed in the intermediate electrode layer 250 , and electrode non-formation regions 381 and 382 are formed in the upper electrode layer 330 .

[0635] The electrode non-formed regions 281 , 282 , 381 , 382 , 483 , and 484 may also be referred to as “dividing positions.” These electrode non-formed regions 281 , 282 , 381 , 382 , 483 , and 484 are arranged at different positions in the radial direction of the vibration plate 220 .

[0636] The electrode non-formation region 381 is arranged radially inward of the vibration plate 220 relative to the electrode non-formation region 281. The electrode non-formation region 281 is arranged radially inward of the vibration plate 220 relative to the electrode non-formation region 483.

[0637] The electrode non-formation region 382 is arranged outside the electrode non-formation region 282 in the radial direction of the vibration plate 220 . The electrode non-formation region 282 is arranged outside the electrode non-formation region 484 in the radial direction of the vibration plate 220 .

[0638] In the vibration plate 220, the plurality of electrode-free regions 281, 282, 381, 382, ​​483, and 484 are formed at positions that do not overlap when viewed in the Z-axis direction. This prevents a decrease in the strength of the vibration plate 220. Furthermore, piezoelectric thin films are formed in the electrode-free regions 281, 282, 483, and 484.

[0639] The crystallinity of the piezoelectric film above the boundary between the end of the lower electrode 441 and the electrode non-formed region 483 is lower than the crystallinity of the piezoelectric film above the lower electrode 441. Similarly, the crystallinity of the piezoelectric film above the boundary between the electrode and the electrode non-formed region is lower than the crystallinity of the piezoelectric film above the electrode.

[0640] The splitting position, which serves as the electrode-free region 483, is located radially outward from the first detection region 423 of the diaphragm 220. The splitting position, which serves as the electrode-free region 484, is located radially inward from the second detection region 425 of the diaphragm 220. This prevents the crystal growth of the piezoelectric thin film that generates charge from being hindered. In the acoustic transducer 200, the piezoelectric thin film in the first detection region 423 and the second detection region 425, where charge is generated, has high crystallinity.

[0641] The splitting position, which serves as the electrode-free region 281, is located radially outward from the first detection region 323 of the diaphragm 220. The splitting position, which serves as the electrode-free region 282, is located radially inward from the second detection region 325 of the diaphragm 220. This prevents the crystal growth of the piezoelectric thin film that generates charge from being hindered. In the acoustic transducer 200, the piezoelectric thin film in the first detection region 323 and the second detection region 325, where charge is generated, has high crystallinity.

[0642] [Connection of piezoelectric film]

[0643] In the vibrating plate 220, which functions as a piezoelectric film (piezoelectric element), the electrodes of the first detection regions 323 and 423 are electrically connected in parallel. The electrodes of the first detection region 323 include an upper electrode 331 and an intermediate electrode 251. The electrodes of the first detection region 423 include a lower electrode 441 and an intermediate electrode 251. The electrodes of the second detection regions 325 and 425 are electrically connected in parallel. The electrodes of the second detection region 325 include an upper electrode 333 and an intermediate electrode 253. The electrodes of the second detection region 425 include a lower electrode 443 and an intermediate electrode 253.

[0644] The electrodes of the first detection region and the second detection region are electrically connected in series. Specifically, the electrodes are upper electrodes 331 and 333, lower electrodes 441 and 443, or intermediate electrodes 251 and 253.

[0645] [Operation and Effect of the Acoustic Converter 200 According to the Third Embodiment of the Third Aspect]

[0646] The sound transducer device 200 of the third embodiment of the third aspect includes a support substrate (fixing frame) 211 and a vibration plate 220 serving as a piezoelectric element fixed to the support substrate 211. The vibration plate 220 has multiple detection regions capable of detecting physical quantities: first detection regions 323 and 423 and second detection regions 325 and 425; and non-detection regions 324 and 424 that do not detect physical quantities. The electrodes of the multiple detection regions are electrically connected in series.

[0647] In the third embodiment, the acoustic transducer 200 can detect physical quantities by detecting the deformation of the diaphragm 220 as the diaphragm 220 deforms. The acoustic transducer 200 includes first detection regions 323 and 423 and second detection regions 325 and 425. By electrically connecting the electrodes of these multiple detection regions in series, the sensitivity of the diaphragm 220 can be increased.

[0648] In the acoustic transducer device 200 , the piezoelectric element is a vibration plate (diaphragm) 220 , and an outer periphery 222 of the vibration plate 220 (outer periphery of the diaphragm) is a fixed end fixed to the support substrate 211 .

[0649] In the acoustic converter 200, the multiple detection areas include first detection areas 323 and 423, which are located radially closer to the center C11 of the diaphragm 220, and second detection areas 325 and 425, which are located radially farther from the center C11 of the diaphragm 220. Non-detection areas 324 and 424 are formed circumferentially between the inner and outer detection areas.

[0650] In the acoustic transducer 200 according to the third embodiment, deformation of the diaphragm 220 generates electric charges corresponding to the diaphragm 220, and the generated electric charges are detected in the first detection regions 323 and 423 and the second detection regions 325 and 425. In the acoustic transducer 200, the electrodes are cut in the radial direction of the diaphragm 220 to form the first detection regions 323 and 423, the non-detection regions 324 and 424, and the second detection regions 325 and 425. This acoustic transducer 200 can improve the sensitivity of detecting electric charges based on sound pressure.

[0651] Figure 55 2 is a side view illustrating the distribution of electric charges generated on the vibration plate 220 that is deformed by sound pressure. In the vibration plate 220 serving as a diaphragm, the outer periphery 222 on the radially outer side is fixed to the support substrate 211. Figure 55 As shown, the area near the inflection point P12 is less likely to deform and the amount of charge generated is small. The inflection point P12 and its vicinity, where the amount of charge generated is small, are included in the non-detection areas 324 and 424.

[0652] In contrast, the area near the center C11 of the diaphragm 220 and the periphery 222 of the diaphragm 220 deforms significantly, resulting in a higher amount of charge. The center C11 of the diaphragm 220 and its surrounding area are included in the first detection areas 323 and 423. The area near the periphery 222 of the diaphragm 220 is included in the second detection areas 325 and 425. In the sound conversion device 200, the area including the inflection point P12, where charge generation is relatively low, is not included in the first detection areas 323 and 423 or the second detection areas 325 and 425. This improves the signal-to-noise ratio (SN) of the sound conversion device 200, enabling detection sensitivity for charge.

[0653] [Shape of the End of the Electrode]

[0654] Next, the shape of the end portion of the electrode will be described. Figure 54 As shown, the ends of the upper electrodes 331-333, lower electrodes 441-443, and intermediate electrodes 251-253 may also be tapered. The ends of the electrodes are radially opposed to each other in the vibrating plate 220. The tapered shape of the electrode ends is formed so that the lower side protrudes further than the upper side.

[0655] By tapering the ends of the lower electrodes 441-443 in this manner, the steps at the boundaries between the lower electrodes 441-443 and the electrode-free regions 483 and 484 can be made gentle. This can suppress a decrease in the crystallinity of the piezoelectric layer 460. The same applies to the boundaries between the other electrodes and the electrode-free regions.

[0656] [Acoustic Converter 200B According to Fourth Embodiment of Third Aspect]

[0657] Next, an acoustic transducer 200B according to a fourth embodiment of the third aspect will be described. Figure 56 This is a plan view illustrating an acoustic transducer 200B according to a fourth embodiment of the third aspect. Figure 57 This is a cross-sectional view of an acoustic converter device according to a fourth embodiment of the third embodiment, taken along Figure 56 Cross-sectional view of line IX-IX in FIG. Figure 56 as well as Figure 57 The sound conversion device 200B of the fourth embodiment of the third aspect shown in FIG. Figure 50The acoustic transducer 200 of the third embodiment of the third aspect shown differs in that it includes a plurality of circumferentially divided upper electrodes 331B and 333B, a plurality of circumferentially divided lower electrodes 441B and 443B, a plurality of circumferentially divided intermediate electrodes 251B and 253B, and radially extending electrode-free regions 385 and 386. In the description of the acoustic transducer 200B of the fourth embodiment of the third aspect, descriptions identical to those of the acoustic transducer 200 of the third embodiment of the third aspect may be omitted.

[0658] [Laminated body 300B]

[0659] like Figure 57 As shown, the acoustic transducer 200B includes laminates 300B and 400B. The laminate 300B includes an upper electrode layer 330B, a piezoelectric layer 360, and an intermediate electrode layer 250B. The upper electrode layer 330B includes a plurality of upper electrodes 331B divided in the circumferential direction, a circumferentially continuous upper electrode 332, and a plurality of circumferentially divided upper electrodes 333B. The intermediate electrode layer 250B includes a plurality of intermediate electrodes 251B divided in the circumferential direction, a circumferentially continuous intermediate electrode 252, and a plurality of circumferentially divided intermediate electrodes 253B.

[0660] [First detection area 323B]

[0661] The stack 300B includes a first detection region 323B, a non-detection region 324B, and a second detection region 325B. The first detection region 323B includes multiple upper electrodes 331B, a piezoelectric layer 360, and multiple intermediate electrodes 251B. The first detection region 323B includes multiple piezoelectric elements. Each piezoelectric element in the first detection region 323B includes an upper electrode 331B, a piezoelectric layer 360, and an intermediate electrode 251B.

[0662] [Second detection area 325B]

[0663] The second detection region 325B includes a plurality of upper electrodes 333B, a piezoelectric layer 360, and a plurality of intermediate electrodes 253B. The second detection region 325B includes a plurality of piezoelectric elements. In the second detection region 325B, the piezoelectric element includes an upper electrode 333B, a piezoelectric layer 360, and an intermediate electrode 253B.

[0664] like Figure 56 As shown, electrode non-formation regions 381 and 382 and electrode non-formation regions 385 and 386 are formed in the upper electrode layer 330B.

[0665] [Electrode non-formation region 385]

[0666] Electrode-free regions 385 divide the upper electrode into multiple sections within first detection region 323B. Electrode-free regions 385 extend radially from the center of diaphragm 220B. Multiple electrode-free regions 385 are circumferentially spaced evenly apart. The areas of the multiple upper electrodes 331B are substantially equal. For example, the sound conversion device 200B includes ten upper electrodes 331B.

[0667] [Electrode non-formation region 386]

[0668] Electrode non-formation region 386 divides the upper electrode into a plurality of parts in second detection region 325B. Electrode non-formation region 386 extends radially from electrode non-formation region 382 toward outer periphery 222 of vibration plate 220. Multiple electrode non-formation regions 386 are arranged at equal intervals in the circumferential direction.

[0669] [Laminated body 400B]

[0670] like Figure 57 As shown, the stack 400B includes an intermediate electrode layer 250B, a piezoelectric layer 460, and a lower electrode layer 440B. The intermediate electrode layer 250B serves as both the stack 300B and the stack 400B. The lower electrode layer 440B includes a plurality of lower electrodes 441B divided in the circumferential direction, a circumferentially continuous lower electrode 442, and a plurality of lower electrodes 443B divided in the circumferential direction.

[0671] [First detection area 423B]

[0672] The stack 400B includes a first detection region 423B, a non-detection region 424B, and a second detection region 425B. The first detection region 423B includes multiple intermediate electrodes 251B, a piezoelectric layer 460, and multiple lower electrodes 441B. The first detection region 423B includes multiple piezoelectric elements. In the first detection region 423B, the piezoelectric elements include intermediate electrodes 251B, a piezoelectric layer 460, and lower electrodes 441B. In the first detection region 423B, the areas of the multiple lower electrodes 441B are substantially equal.

[0673] [Second detection area 425B]

[0674] Second detection region 425B includes multiple intermediate electrodes 253B, a piezoelectric layer 460, and multiple lower electrodes 443B. Second detection region 425B includes multiple piezoelectric elements. In second detection region 425B, the piezoelectric elements include intermediate electrodes 253B, a piezoelectric layer 460, and lower electrodes 443B. In second detection region 425B, the areas of the multiple lower electrodes 443B are equal.

[0675] Like the upper electrode layer 330B of the stacked body 300B, the lower electrode layer 440B and the intermediate electrode layer 250B of the stacked body 400B include electrode-free regions extending in the radial direction.

[0676] [Electrostatic Capacitance of Piezoelectric Element]

[0677] In the stacked body 300B, the electrostatic capacitances of the plurality of piezoelectric elements arranged in the circumferential direction of the vibration plate 220 are equal to each other. In the stacked body 400B, the electrostatic capacitances of the plurality of piezoelectric elements arranged in the circumferential direction of the vibration plate 220 are substantially equal to each other.

[0678] [Series connection of multiple piezoelectric elements]

[0679] In the vibration plate 220B, a plurality of piezoelectric elements arranged in the circumferential direction and the radial direction are electrically connected in series.

[0680] [Operation and Effect of the Acoustic Conversion Device 200B According to the Fourth Embodiment of the Third Aspect]

[0681] The sound transducer 200B according to the fourth embodiment of the third aspect also exhibits the same operational effects as those of the sound transducer 200 according to the third embodiment of the third aspect described above.

[0682] In the acoustic transducer 200B, the multiple detection areas include first detection areas 323B and 423B, which are located radially closer to the center C11 of the diaphragm 220B; and second detection areas 325B and 425B, which are located radially farther from the center C11 of the diaphragm 220B. The non-detection areas 324 and 424 include electrode-free areas 381 and 382, ​​which are formed circumferentially between the inner and outer detection areas; and multiple electrode-free areas 385 and 386, which extend radially along the diaphragm and are spaced apart circumferentially.

[0683] According to such an acoustic transducer 200B, by including the electrode non-formation regions 385 and 386 extending in the radial direction, the electrode in the detection region can be divided into a plurality of parts.

[0684] [Modification of the Acoustic Conversion Device 200B According to the Fourth Embodiment of the Third Aspect]

[0685] In the acoustic transducer 200B, the diaphragm (piezoelectric element) 220B includes a piezoelectric film, which includes a lower electrode layer 440B; a lower piezoelectric layer 460 formed on the lower electrode layer 440; an intermediate electrode layer 250B formed on the lower piezoelectric layer 460; an upper piezoelectric layer 360 formed on the intermediate electrode layer 250B; and an upper electrode layer 330 formed on the upper piezoelectric layer 360. Between the plurality of detection regions (first detection regions 323B and 423B and second detection regions 325B and 425B), there are electrode-non-formation regions (first electrode-non-formation regions) where the upper and lower electrodes are not formed, or electrode-non-formation regions (second electrode-non-formation regions) where the intermediate electrodes are not formed.

[0686] In the acoustic conversion device 200B, when electrode-non-formation regions (first electrode-non-formation regions) are formed on the upper and lower electrodes, electrode-non-formation regions (second electrode-non-formation regions) do not need to be formed on the intermediate electrode. In the acoustic conversion device 200B, when electrode-non-formation regions (second electrode-non-formation regions) are formed on the intermediate electrode, electrode-non-formation regions (first electrode-non-formation regions) 381, 382, ​​483, and 484 do not need to be formed on the upper and lower electrodes.

[0687] Furthermore, within the detection region, the upper electrode, the intermediate electrode, and the lower electrode may be divided circumferentially. The upper electrode division position (electrode non-formed region) may differ from the intermediate electrode division position in the circumferential direction. Similarly, the lower electrode division position may differ from the intermediate electrode division position in the circumferential direction.

[0688] [Circuit Diagram of Acoustic Conversion Device 200B According to Fourth Embodiment of Third Aspect]

[0689] Next, a circuit diagram of an acoustic transducer 200B according to a fourth embodiment of the third aspect will be described. Figure 58 This is a circuit diagram of an acoustic transducer 200B according to a fourth embodiment of the third aspect.

[0690] like Figure 58 As shown, the acoustic transducer 200B includes a MEMS microphone chip 201. The MEMS microphone chip 201 carries a vibration plate 220B. The vibration plate 220B includes a plurality of first detection areas 323B and 423B and second detection areas 325B and 425B.

[0691] The multiple first detection regions 323B and 423B include an upper electrode 331B, an intermediate electrode 251B, and a lower electrode 441B. The multiple second detection regions 325B and 425B include an upper electrode 333B, an intermediate electrode 253B, and a lower electrode 443B. The upper electrode 331B includes n circumferentially divided upper electrodes 331B-1, 331B-2, ..., 331B-n. n is a natural number. The same applies to the other upper, intermediate, and lower electrodes.

[0692] In the first detection regions 323B and 423B of the acoustic transducer 200B, piezoelectric output charges between the upper electrode 331B and the intermediate electrode 251B, and between the intermediate electrode 251B and the lower electrode 441B can be detected. Plural piezoelectric elements arranged in the circumferential direction are connected in series.

[0693] In the second detection regions 325B and 425B of the acoustic transducer 200B, piezoelectric output charges between the upper electrode 333B and the intermediate electrode 253B, and between the intermediate electrode 253B and the lower electrode 443B can be detected.

[0694] The MEMS microphone chip 201 also has pads 213 and 214. Multiple electrodes of piezoelectric elements are connected to these pads. The sound converter 200B includes an IC 202 connected to the pads 213. IC 202 is an amplifier that amplifies the output signal of the piezoelectric element of the vibration plate 220B. Alternatively, IC 202 may also be configured to amplify the output signal of the piezoelectric element of the vibration plate 220B and then perform analog-to-digital conversion.

[0695] The polarity of the charge generated in the second detection regions 325B and 425B is opposite to the polarity of the charge generated in the first detection regions 323B and 423B. Therefore, the wiring in the second detection regions 325B and 425B and the first detection regions 323B and 423B are connected in series in reverse order.

[0696] [Electrode connection]

[0697] In the acoustic transducer 200B, the upper electrodes 331B and the intermediate electrodes 251B of the plurality of first detection regions 323B may be electrically connected in series. Similarly, the upper electrodes 333B and the intermediate electrodes 253B of the plurality of second detection regions 325B may be electrically connected in series.

[0698] In the acoustic transducer 200B, the lower electrodes 441B and the intermediate electrodes 251B of the plurality of first detection regions 423B may be electrically connected in series. Similarly, the lower electrodes 433B and the intermediate electrodes 253B of the plurality of second detection regions 425B may be electrically connected in series.

[0699] In the acoustic conversion device 200B, the upper electrodes and the lower electrodes of the plurality of detection areas may be electrically connected in parallel.

[0700] [Regarding the relationship between the sensing area diameter ratio and the normalized SNR]

[0701] Next, the relationship between the sensing area diameter ratio and the normalized SNR will be described. Figure 59 It is a graph showing the relationship between the ratio of the sensing area diameter and the normalized SNR. Figure 59 In FIG. 5 , the horizontal axis represents the sensing area diameter ratio [%], and the vertical axis represents the normalized SNR [%]. Figure 59 The graph shown is a representation of Figure 50 The graph shown is a relationship between the sensor area diameter ratio and the normalized SNR in the acoustic transducer 200 according to the third embodiment of the third aspect.

[0702] The "sensing area ratio" can be expressed by the following formula (1).

[0703] Sensing area ratio = (electrode separation radius / diaphragm radius) × 100···(1)

[0704] The “electrode separation radius” may also be the radius of the inner detection area 323. The “diaphragm radius” may also be the radius of the vibration plate 220. Figure 50 , a diameter φ323 of the inner detection region 323 and a diameter φ325 of the vibration plate 220 are shown.

[0705] The inner diameter of the opening 221 covered by the vibration plate 220 is set to 100% of the sensing area diameter ratio. The normalized SNR is set to 100% when the electrode non-formation area is formed at 71%. Figure 59 In , “0” indicates the position of the boundary between the inner detection area 323 and the non-detection area 324. Figure 59 In FIG. 3 , “×” indicates the position of the boundary between the outer detection area 325 and the non-detection area 324 .

[0706] The SNR normalized value of the inner detection area 323 is a value obtained when the boundary between the outer detection area 325 and the non-detection area 324 is set to 71% and the outer diameter Φ323 of the inner detection area 323 is changed.

[0707] The SNR normalized value of the outer detection area 325 is a value obtained when the boundary between the inner detection area 323 and the non-detection area 324 is set to 71% and the inner diameter Φ324 of the outer detection area 325 is changed.

[0708] exist Figure 59 In the example shown, the SNR normalized value of the inner detection area 323 reaches a maximum at point P21. The sensing area diameter ratio at point P21 is 59%.

[0709] exist Figure 59 In the example shown, the SNR normalized value of the outer detection area 325 reaches a maximum at point P22. The sensing area diameter ratio at point P22 is 81%.

[0710] When the sensing area diameter ratio of the inner detection area 323 is 44% or more and 71% or less, the normalized SNR value is 100% or more. When the sensing area diameter ratio of the inner detection area 323 is 49% or more and 67% or less, the normalized SNR value is 104% or more. When the sensing area diameter ratio of the inner detection area 323 is 51% or more and 65% or less, the normalized SNR value is 106% or more.

[0711] The sensing area diameter ratio of the inner detection region 323 is preferably 44% to 71%, more preferably 49% to 67%, and even more preferably 51% to 65%.

[0712] When the sensing area diameter ratio of the outer detection area 325 is 71% or more and 89% or less, the normalized SNR value is 100% or more. When the sensing area diameter ratio of the outer detection area 325 is 75% or more and 87% or less, the normalized SNR value is 104% or more. When the sensing area diameter ratio of the outer detection area 325 is 78% or more and 84% or less, the normalized SNR value is 106% or more.

[0713] The sensing area diameter ratio of the outer detection region 325 is preferably 71% to 89%, more preferably 75% to 87%, and even more preferably 78% to 84%.

[0714] The case where the sensing area diameter ratio of the inner detection region 323 is 71% and the sensing area diameter ratio of the outer detection region 325 is 71% may also be a case where the electrode division position exists at the 71% position.

[0715] In the acoustic conversion device 200, when the sensing area diameter ratio of the outer detection area 325 is 71% or more and 89% or less, the sensing area diameter ratio of the inner detection area 323 may be set to a value outside the range of 44% or more and 71% or less. In such a case, the normalized SNR value may be higher.

[0716] In the acoustic conversion device 200, when the sensing area diameter ratio of the inner detection area 323 is 44% or more and 71% or less, the sensing area diameter ratio of the outer detection area 325 may be set to a value outside the range of 71% or more and 89% or less. In such a case, the normalized SNR value may be higher.

[0717] In addition, relative to the structure etc. enumerated in the above-mentioned embodiment, other embodiments etc. in combination with other constituent elements etc. can also be used, and the present invention is not limited to the structure shown here. About this aspect, can be changed within the scope of not departing from the gist of the present invention, can be appropriately determined according to its application mode.

[0718] In the first embodiment described above, the acoustic transducer 100 is illustrated as including a cantilever beam structured arm 20 having a free end 21 and a fixed end 22. However, the acoustic transducer 100 is not limited to this configuration. Alternatively, the acoustic transducer 100 may include a beam structure that serves as a double-support beam, with both ends of the beam structure connected to opposing portions of the fixed frame 10 as fixed ends 22. In the acoustic transducer 100 with this structure, the center portion of the double-support beam deflects in the thickness direction when subjected to sound pressure. Alternatively, the acoustic transducer 100 may include a double-support beam in place of the cantilever 20.

[0719] In the first embodiment described above, the acoustic transducer devices 100 , 100B, 100C, and 100D are described as including a pair of cantilevers 20A and 20B. However, the acoustic transducer devices 100 , 100B, 100C, and 100D may include one cantilever 20 or three or more cantilevers 20 .

[0720] In the second embodiment described above, the acoustic transducer devices 100, 100B-100G are exemplified as including a cantilever beam structured cantilever 20 having a free end 21 and a fixed end 22. However, the acoustic transducer devices 100, 100B-100G are not limited to this configuration. The acoustic transducer devices 100, 100B-100G may also include a beam structure serving as a double-support beam, with both ends of the beam structure connected to opposing portions of the fixed frame 10 as fixed ends 22. In the acoustic transducer devices 100, 100B-100G with this structure, the center portion of the double-support beam deflects in the thickness direction when subjected to sound pressure. The acoustic transducer devices 100, 100B-100G may also include a double-support beam in place of the cantilever 20 (20A-20D).

[0721] In the above-mentioned embodiment of the second scheme, the case where the upper electrode 30, the lower electrode 40 and the intermediate electrode 50 are formed in the non-detection area 24 is illustrated, but at least one of the upper electrode 30, the lower electrode 40 and the intermediate electrode 50 may not be formed in the non-detection area 24, the upper electrode 30 and the lower electrode 40 may not be formed, or the upper electrode 30, the lower electrode 40 and the intermediate electrode 50 may not be formed.

[0722] In the third embodiment described above, the acoustic transducer devices 100 and 100B are exemplified as having a cantilever beam structure with a cantilever 20 having a free end 21 and a fixed end 22. However, the acoustic transducer devices 100 and 100B are not limited to this structure. The acoustic transducer devices 100 and 100B may also have a beam structure that is a double-support beam, with both ends of the beam structure connected to opposing portions of the fixed frame 10 as fixed ends 22. In the acoustic transducer devices 100 and 100B with this structure, the center portion of the double-support beam deflects in the thickness direction when subjected to sound pressure. The acoustic transducer devices 100 and 100B may also have a double-support beam in place of the cantilever 20.

[0723] In the third embodiment described above, the acoustic transducer devices 100 and 100B are described as including a pair of cantilevers 20A and 20B. However, the acoustic transducer devices 100 and 100B may include one cantilever 20 or may include three or more cantilevers 20 .

[0724] In the third embodiment described above, the intermediate electrode 50 is thicker than the upper electrode 30, but may also be the same thickness as the lower electrode 40. The intermediate electrode 50 may also be thicker than the upper electrode 30 and thinner than the lower electrode 40. The intermediate electrode 50 may be thicker than the lower electrode 40, but may also be the same thickness as the upper electrode 30. The intermediate electrode 50 may also be thicker than the lower electrode 40 and thinner than the upper electrode 30.

Claims

1. An acoustic conversion device, characterized in that: have: Fixed frame; and The piezoelectric element is fixed to the above-mentioned fixing frame, The piezoelectric element has: a plurality of detection areas capable of detecting physical quantities; and Non-detection area where physical quantities are not detected. The electrodes of the plurality of detection areas are electrically connected in series.

2. The sound conversion device according to claim 1, wherein The piezoelectric element is a cantilever, one end of which is a fixed end fixed to the fixing frame, and the other end is a free end, and extends from the fixing frame toward the inner side of the fixing frame. The cantilever includes a first cantilever and a second cantilever, and the first cantilever and the second cantilever are opposed to each other in a first direction in which the cantilever extends.

3. The sound conversion device according to claim 2, characterized in that The electrodes of the plurality of detection regions of the first cantilever and the electrodes of the plurality of detection regions of the second cantilever are electrically connected in series.

4. The sound conversion device according to claim 2, wherein: The plurality of detection areas are arranged on a side close to the fixed end. The non-detection area is arranged on a side closer to the free end.

5. The sound conversion device according to claim 1, wherein The piezoelectric element is a diaphragm. The outer periphery of the diaphragm is a fixed end fixed to the fixing frame.

6. The sound conversion device according to claim 5, characterized in that The above-mentioned multiple detection areas have: an inner detection region disposed near the center of the diaphragm in the radial direction of the diaphragm; and an outer detection area, which is arranged at a position away from the center of the diaphragm in the radial direction of the diaphragm, The non-detection area mentioned above has: a circumferential electrode non-formation region, which is annular, continuous in the circumferential direction of the diaphragm, and formed between the inner detection region and the outer detection region; and A plurality of radial electrode non-formation regions extend in the radial direction of the diaphragm and are formed at intervals in the circumferential direction of the diaphragm.

7. The sound conversion device according to claim 1, wherein The piezoelectric element has a piezoelectric film. The piezoelectric film includes: lower electrode; a lower piezoelectric layer formed on the lower electrode; an intermediate electrode formed on the lower piezoelectric layer; an upper piezoelectric layer formed on the intermediate electrode; and an upper electrode formed on the upper piezoelectric layer, Between the plurality of detection regions, there is a first electrode non-formation region where the upper electrode and the lower electrode are not formed, or a second electrode non-formation region where the intermediate electrode is not formed.

8. The sound conversion device according to claim 7, characterized in that The piezoelectric element is a diaphragm. The outer periphery of the diaphragm is fixed to the fixed end of the fixed frame. The lower electrodes and the upper electrodes of the plurality of detection regions, or the intermediate electrodes, are electrically connected in series. The upper electrodes and the lower electrodes of the plurality of detection regions are electrically connected in parallel.

9. The sound conversion device according to claim 7, characterized in that The first electrode non-formation regions and the second electrode non-formation regions are alternately arranged in a direction in which the plurality of detection regions are arranged.

10. The sound conversion device according to claim 1, wherein The plurality of detection areas include a first detection area and a second detection area. The first detection area includes: a first lower electrode; a first lower piezoelectric layer formed on the first lower electrode; a first intermediate electrode formed on the first lower piezoelectric layer; a first upper piezoelectric layer formed on the first intermediate electrode; and a first upper electrode formed on the first upper piezoelectric layer, The second detection area includes: a second lower electrode; a second lower piezoelectric layer formed on the second lower electrode; a second intermediate electrode formed on the second lower piezoelectric layer; a second upper piezoelectric layer formed on the second intermediate electrode; and a second upper electrode formed on the second upper piezoelectric layer, Between the first detection area and the second detection area is formed: a lower connecting electrode connecting the first lower electrode and the second intermediate electrode; and An upper connecting electrode connecting the first upper electrode and the second intermediate electrode.

11. The sound conversion device according to claim 2, wherein: The plurality of detection areas include a first detection area and a second detection area. The first detection area includes: a first lower electrode; a first lower piezoelectric layer formed on the first lower electrode; a first intermediate electrode formed on the first lower piezoelectric layer; a first upper piezoelectric layer formed on the first intermediate electrode; and a first upper electrode formed on the first upper piezoelectric layer, The second detection area includes: a second lower electrode; a second lower piezoelectric layer formed on the second lower electrode; a second intermediate electrode formed on the second lower piezoelectric layer; a second upper piezoelectric layer formed on the second intermediate electrode; and a second upper electrode formed on the second upper piezoelectric layer, Between the first detection area and the second detection area, The first lower electrode extends toward the second lower electrode in a second direction intersecting the first direction in which the cantilever extends. The second intermediate electrode extends toward the first intermediate electrode in the second direction. The first upper electrode extends toward the second upper electrode in the second direction. A wiring portion is provided for connecting the extending portion of the first lower electrode, the extending portion of the second intermediate electrode, and the extending portion of the first upper electrode.

12. The sound conversion device according to claim 11, wherein The wiring section includes: a first bonding portion formed on the first lower electrode and bonded to the first lower electrode; a first rising portion connected to the first bonding portion and extending along the thickness direction of the piezoelectric film; a second bonding portion connected to the first rising portion, formed on the second intermediate electrode and bonded to the second intermediate electrode; a second rising portion connected to the second bonding portion and extending in a thickness direction of the piezoelectric film; and The third bonding portion is connected to the second rising portion, is formed on the first upper electrode, and is connected to the first upper electrode.

13. An acoustic conversion device, characterized in that: have: Fixed frame; A double support beam with both ends fixed to the opposite parts of the above-mentioned fixed frame, The above double support beam has: a plurality of detection areas capable of detecting physical quantities; and Non-detection area where physical quantities are not detected. The electrodes of the plurality of detection areas are electrically connected in series.

14. An acoustic conversion device, characterized in that: have: Fixed frame; and The piezoelectric element is fixed to the above-mentioned fixing frame, The piezoelectric element has: a detection area capable of detecting a physical quantity; and A non-detection area where physical quantities are not detected.

15. The sound conversion device according to claim 14, wherein: The piezoelectric element has a piezoelectric film. The piezoelectric film includes: lower electrode; a first piezoelectric layer formed on the lower electrode; an intermediate electrode formed on the first piezoelectric layer; a second piezoelectric layer formed on the intermediate electrode; and an upper electrode formed on the second piezoelectric layer, An electrode non-formation region is provided between the detection region and the non-detection region, and at least one of the lower electrode, the intermediate electrode, and the upper electrode is not formed in the electrode non-formation region.

16. The sound conversion device according to claim 14 or 15, characterized in that: The piezoelectric element is a cantilever, one end of which is a fixed end fixed to the fixing frame, and the other end is a free end, and extends from the fixing frame toward the inner side of the fixing frame. The cantilever includes a first cantilever and a second cantilever, and the first cantilever and the second cantilever are opposed to each other in a first direction in which the cantilever extends.

17. The sound conversion device according to claim 16, wherein: The detection region has a length from the fixed end to the cantilever of not less than 20% and not more than 75% of the total length of the cantilever in a first direction in which the cantilever extends.

18. The sound conversion device according to claim 17, characterized in that The detection region has a length in the first direction that is not less than 30% and not more than 60% of the entire length from the fixed end to the cantilever.

19. The sound conversion device according to claim 18, characterized in that The detection region has a length in the first direction that is not less than 40% and not more than 45% of the entire length from the fixed end to the cantilever.

20. The sound conversion device according to claim 16, wherein In the direction in which the cantilever extends, i.e., the first direction, An end portion of the detection region closer to the free end is formed at a position not less than 20% and not more than 75% of the total length from the fixed end to the cantilever.

21. The sound conversion device according to claim 20, characterized in that In the first direction, An end portion of the detection region closer to the free end is formed at a position not less than 30% and not more than 60% of the total length from the fixed end to the cantilever.

22. The sound conversion device according to claim 21, characterized in that In the first direction, An end portion of the detection region closer to the free end is formed at a position not less than 40% and not more than 45% of the total length from the fixed end to the cantilever.

23. The sound conversion device according to claim 14 or 15, characterized in that: The piezoelectric element is a diaphragm. The outer periphery of the diaphragm is a fixed end fixed to the fixing frame.

24. The sound conversion device according to claim 23, characterized in that A plurality of the above detection areas have: an inner detection region disposed near the center of the diaphragm in the radial direction of the diaphragm; and an outer detection area, which is arranged at a position away from the center of the diaphragm in the radial direction of the diaphragm, The non-detection area mentioned above has: a first non-detection region disposed in a circumferential direction of the diaphragm and formed between the inner detection region and the outer detection region; and a plurality of second non-detection areas extending in the radial direction of the diaphragm and formed at intervals in the circumferential direction of the diaphragm; The radially outer end of the inner detection region is formed at a position not less than 44% and not more than 71% of the radius of the diaphragm from the center of the diaphragm. The radially inner end of the outer detection region is arranged outward of the radially outer end of the inner detection region in the radial direction of the diaphragm and is formed at a position not less than 71% and not more than 89% of the radius of the diaphragm from the center of the diaphragm.

25. The sound conversion device according to claim 24, characterized in that The radially outer end of the inner detection region is formed at a position not less than 49% and not more than 67% of the radius of the diaphragm from the center of the diaphragm. The radially inner end portion of the outer detection region is formed at a position that is not less than 75% and not more than 87% of the radius of the diaphragm from the center of the diaphragm.

26. The sound conversion device according to claim 24, characterized in that The radially outer end of the inner detection region is formed at a position not less than 51% and not more than 65% of the radius of the diaphragm from the center of the diaphragm. The radially inner end portion of the outer detection region is formed at a position that is not less than 78% and not more than 84% of the radius of the diaphragm from the center of the diaphragm.

27. The sound conversion device according to claim 15, characterized in that The electrode non-formation region is a region where the intermediate electrode is not formed.

28. The sound conversion device according to claim 15, characterized in that The electrode non-forming region includes: a region where the lower electrode is not formed; and A region where the upper electrode is not formed.

29. The sound conversion device according to claim 28, characterized in that The region where the lower electrode is not formed is formed at a position farther from a fixed end fixed to the fixing frame than the region where the upper electrode is not formed.

30. The sound conversion device according to claim 16, characterized in that A direction in which the cantilever extends is defined as a first direction. In a direction intersecting the first direction, a width of the first cantilever is greater than a width of the second cantilever.

31. An acoustic conversion device, characterized in that: have: Fixed frame; and A double support beam with both ends fixed to the opposite parts of the above-mentioned fixed frame, The above double support beam has: a detection area capable of detecting a physical quantity; and A non-detection area where physical quantities are not detected.

32. An acoustic conversion device, characterized in that: have: Fixed frame; and The piezoelectric element is fixed to the above-mentioned fixing frame, The piezoelectric element has: lower electrode; a first piezoelectric layer formed on the lower electrode; an intermediate electrode formed on the first piezoelectric layer; a second piezoelectric layer formed on the intermediate electrode; and an upper electrode formed on the second piezoelectric layer, The intermediate electrode is thicker than the upper electrode or the lower electrode.

33. The sound conversion device according to claim 32, characterized in that The piezoelectric element is a cantilever, one end of which is a fixed end fixed to the fixing frame, and the other end is a free end, and extends from the fixing frame toward the inner side of the fixing frame. The cantilever includes a first cantilever and a second cantilever, and the first cantilever and the second cantilever are opposite to each other in a first direction in which the cantilever extends.

34. The sound conversion device according to claim 33, characterized in that The piezoelectric element is a diaphragm. The outer periphery of the diaphragm is fixed to the fixed end of the fixing frame.

35. The sound conversion device according to claim 33 or 34, characterized in that: The thickness of the intermediate electrode is not less than 10% and not more than 90% of the thickness of the piezoelectric element.

36. The sound conversion device according to claim 33 or 34, characterized in that The thickness of the intermediate electrode is not less than 30% and not more than 70% of the thickness of the piezoelectric element.

37. The sound conversion device according to claim 33 or 34, characterized in that The thickness of the intermediate electrode is not less than 40% and not more than 60% of the thickness of the piezoelectric element.

38. The sound conversion device according to claim 32, characterized in that The piezoelectric element includes a neutral surface that does not generate any tensile force or compressive force generated inside the piezoelectric element when the piezoelectric element is flexed. The intermediate electrode includes the neutral surface.

39. The sound conversion device according to claim 38, characterized in that The neutral plane is the center of the piezoelectric element in the thickness direction.

40. The sound conversion device according to claim 39, characterized in that The thickness of the upper electrode is the same as the thickness of the lower electrode.

41. The sound conversion device according to claim 39 or 40, characterized in that The thickness of the first piezoelectric layer is the same as the thickness of the second piezoelectric layer.

42. The sound conversion device according to claim 41, characterized in that The material of the upper electrode is the same as that of the lower electrode. The material of the first piezoelectric layer is the same as that of the second piezoelectric layer.

43. An acoustic conversion device, characterized in that: have: Fixed frame; and A double support beam with both ends fixed to the opposite parts of the above-mentioned fixed frame, The above double support beam has: lower electrode; a first piezoelectric layer formed on the lower electrode; an intermediate electrode formed on the first piezoelectric layer; a second piezoelectric layer formed on the intermediate electrode; and an upper electrode formed on the second piezoelectric layer, The intermediate electrode is thicker than the upper electrode or the lower electrode.

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