Acoustic converter

Abstract

To improve sensitivity. [Solution] The sound conversion device 200 comprises a support substrate 211 having an opening 221, and a diaphragm 220 provided on the support substrate 211 so as to cover the opening 221, which deforms in response to sound pressure and generates an electric charge. The diaphragm 220 has a first detection region 323 located near the center of the opening 221 and capable of detecting an electric charge, a non-detection region 324 located radially outside the first detection region 323 in the radial direction of the opening and not capable of detecting an electric charge, and a second detection region 325 located radially outside the non-detection region 324 in the radial direction of the opening and capable of detecting an electric charge.

Description

[Technical Field]

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

[0002] For example, there is known a piezoelectric element including a piezoelectric film having one end supported and the other end being a free end, and a pair of electrodes disposed across the piezoelectric film (see, for example, Patent Document 1). [Prior Art Literature] [Patent Literature]

[0003] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2019-140638 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] In an acoustic transducer including a piezoelectric element, improvement of sensitivity is demanded. An object of the present disclosure is to provide an acoustic transducer capable of improving sensitivity. [Means for Solving the Problem]

[0005] An acoustic transducer according to the present disclosure includes: a support substrate having an opening; and a vibration plate provided on the support substrate so as to cover the opening, the vibration plate being deformed in accordance with sound pressure to generate an electric charge. The vibration plate has: a first detection region disposed at a position close to the center of the opening and capable of detecting an electric charge; a non-detection region disposed outward of the first detection region in a radial direction of the opening and not detecting an electric charge; and a second detection region disposed outward of the non-detection region in the radial direction of the opening and capable of detecting an electric charge. [Effects of the Invention]

[0006] The present disclosure can provide an acoustic transducer capable of improving sensitivity. [Brief Description of the Drawings]

[0007] [Figure 1] This is a plan view illustrating an acoustic conversion device according to the first embodiment. [Figure 2] This is a perspective view illustrating an acoustic conversion device according to the first embodiment. [Figure 3] This is a perspective view illustrating the acoustic conversion device according to the first embodiment, viewed from the bottom. [Figure 4] This is a cross-sectional view illustrating an acoustic conversion device according to the first embodiment. [Figure 5] This is a magnified cross-sectional view illustrating a diaphragm (piezoelectric film). [Figure 6] This is a side view illustrating the distribution of electric charge generated on a diaphragm that deforms under sound pressure. [Figure 7] This is a magnified cross-sectional view illustrating a larger portion of the diaphragm. [Figure 8] This is a plan view illustrating an acoustic conversion device according to the second embodiment. [Figure 9] This is a cross-sectional view illustrating an acoustic conversion device according to the second embodiment, and is a cross-sectional view along the line IX-IX in Figure 8. [Figure 10] This is a circuit diagram of the sound conversion device according to the second embodiment. [Figure 11] This is an exploded perspective view illustrating an acoustic conversion device according to the third embodiment. [Figure 12] This is an exploded perspective view illustrating an acoustic conversion device according to the fourth embodiment. [Figure 13] This is a plan view illustrating an acoustic conversion device according to a modified example. [Figure 14] This table shows the relationship between the thickness of the intermediate layer, the signal-to-noise ratio, and the resonant frequency. [Figure 15] Figure 15(a) is a partially exploded perspective view illustrating a modified acoustic converter 200E, and Figure 15(b) is an enlarged view illustrating the intermediate layer in detail. [Figure 16] This graph shows the relationship between the sensing area diameter ratio and the normalized SNR. [Modes for carrying out the invention]

[0008] The acoustic converter according to the embodiment will be described below with reference to the attached drawings. In this specification and drawings, substantially identical components may be denoted by the same reference numerals to avoid redundant explanations. In this specification, the terms "upper" and "lower" may be used. These refer to the state shown in Figure 4, where the upper electrode 30 is located in the Z-axis direction is referred to as "upper," and the lower electrode 40 is located as "lower." The actual arrangement of the acoustic converter 200 is not limited to this.

[0009] [Acoustic converter 200 according to the first embodiment] Figure 1 is a plan view illustrating the acoustic converter 200 according to the first embodiment. Figure 2 is a perspective view illustrating the acoustic converter 200 according to the first embodiment. Figure 3 is a perspective view illustrating the acoustic converter 200 according to the first embodiment from the bottom side. Figure 4 is a cross-sectional view illustrating the acoustic converter 200 according to the first embodiment. Note that in each figure, mutually orthogonal X-axis, Y-axis, and Z-axis directions may be shown. The X-axis, Y-axis, and Z-axis directions do not have to be orthogonal. The X-axis, Y-axis, and Z-axis directions may be any direction. 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.

[0010] The acoustic converter 200 shown in Figures 1 to 4 is a piezoelectric acoustic converter having a piezoelectric element (piezoelectric film). The acoustic converter 200 may be, for example, a microphone (MEMS microphone). The acoustic converter 200 may be used for noise cancellation. The acoustic converter 200 may be a TWS (True Wireless Stereo) or an in-vehicle device installed in an automobile. The acoustic converter 200 may be used, for example, as a hearing aid. The acoustic converter 200 only needs to be able to detect a physical quantity, and its application is not particularly limited. The physical quantity may be, for example, sound pressure.

[0011] [Support substrate 211] The acoustic transduction device 200 includes a support substrate 211 and a vibration plate 220. The support substrate 211 may have a rectangular shape when viewed in the Z-axis direction. The plate thickness direction of the support substrate 211 is along the Z-axis direction. The support substrate 211 has an upper surface 211a and a lower surface 211b opposed in the Z-axis direction. An opening 221 is formed in the support substrate 211. The opening 221 is formed to penetrate the support substrate 211 in the Z-axis direction. The support substrate 211 is formed from, for example, a silicon wafer. The opening 221 is formed to have a circular shape when viewed in the Z-axis direction. Although the opening 221 is described as being circular, it may be substantially circular including an elliptical shape or a polygonal shape.

[0012] [Vibration plate 220] The vibration plate 220 includes a piezoelectric film. The vibration plate 220 is formed so as to cover the opening 221. The vibration plate 220 is formed to have a circular shape when viewed in the Z-axis direction. An outer peripheral edge 222 of the vibration plate 220 is a fixed end of the vibration plate 220, and is fixed to the upper surface 211a of the support substrate 211. As will be described later, the vibration plate 220 has a first detection region 223, a non-detection region 224, and a second detection region 225. The vibration plate 220 is also called a "diaphragm". Although the vibration plate 220 is described as being circular, it may be substantially circular including an elliptical shape or a polygonal shape.

[0013] [Piezoelectric film] The piezoelectric film, which is the vibration plate 220, deforms in accordance with sound pressure and generates electric charge. FIG. 5 is an enlarged cross-sectional view illustrating an example of the piezoelectric film in an enlarged manner. The piezoelectric film includes a lower electrode layer 440, a lower piezoelectric layer 460, an upper electrode layer 430, an intermediate layer 90, a lower electrode layer 340, an upper piezoelectric layer 360, and an upper electrode layer 330. These lower electrode layer 440, lower piezoelectric layer 460, upper electrode layer 430, intermediate layer 90, lower electrode layer 340, upper piezoelectric layer 360, and upper electrode layer 330 are stacked in this order.

[0014] [Lower electrode layer 440] The lower electrode layer 440 has lower electrodes 441 to 443, which are electrode thin films. The lower electrode layer 440 is positioned close to the opening 221 in the Z-axis direction. The lower electrodes 441 to 443 are positioned apart in the X-axis direction. Lower electrode 441 is circular in shape. When viewed in the Z-axis direction, lower electrode 441 is positioned close to the center C11 of the diaphragm 220. Lower electrode 442 is ring-shaped when viewed in the Z-axis direction. Lower electrode 442 is positioned outside lower electrode 441 in the radial direction. Lower electrode 443 is ring-shaped when viewed in the Z-axis direction. Lower electrode 443 is positioned outside lower electrode 442 in the radial direction. Although the shape of lower electrode 441 is described as circular, it may be approximately circular including ellipses or polygons to match the shape of the diaphragm 220.

[0015] [No-electrode formation area 483,484] In the radial direction of the diaphragm 220, there is an electrode-free region 483 between the lower electrode 441 and the lower electrode 442 where no electrodes are formed. In the radial direction of the diaphragm 220, there is an electrode-free region 484 between the lower electrode 442 and the lower electrode 443 where no electrodes are formed.

[0016] [Lower piezoelectric layer 460] 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 diaphragm 220.

[0017] [Top electrode layer 430] The upper electrode layer 430 has upper electrodes 431 to 433, which are electrode thin films. The upper electrode layer 430 is formed on the lower piezoelectric layer 460. The upper electrodes 431 to 433 are spaced apart in the X-axis direction. The upper electrode 431 is circular in shape. When viewed in the Z-axis direction, the upper electrode 431 is positioned close to the center C11 of the diaphragm 220. The upper electrode 432 is ring-shaped when viewed in the Z-axis direction. In the radial direction, the upper electrode 432 is positioned outside the upper electrode 431. The upper electrode 433 is ring-shaped when viewed in the Z-axis direction. In the radial direction, the upper electrode 433 is positioned outside the upper electrode 432.

[0018] [No-electrode formation area 481,482] In the radial direction of the diaphragm 220, there is an electrode-free region 481 between the upper electrode 431 and the upper electrode 432 where no electrodes are formed. In the radial direction of the diaphragm 220, there is an electrode-free region 482 between the upper electrode 432 and the upper electrode 433 where no electrodes are formed.

[0019] [Middle class 90] The intermediate layer 90 is formed on top of the upper electrode layer 430. The intermediate layer 90 is formed continuously in the radial direction of the diaphragm 220. In the Z-axis direction, the intermediate layer 90 is positioned between the upper electrode layer 430 and the lower electrode layer 340.

[0020] [Lower electrode layer 340] The lower electrode layer 340 has lower electrodes 341 to 343, which are electrode thin films. The lower electrode layer 340 is formed on the intermediate layer 90. The lower electrodes 341 to 343 are spaced apart in the X-axis direction. Lower electrode 341 is circular in shape. When viewed in the Z-axis direction, lower electrode 341 is positioned close to the center C11 of the diaphragm 220. Lower electrode 342 is ring-shaped when viewed in the Z-axis direction. Lower electrode 342 is positioned outside lower electrode 341 in the radial direction. Lower electrode 343 is ring-shaped when viewed in the Z-axis direction. Lower electrode 343 is positioned outside lower electrode 342 in the radial direction.

[0021] [Electrode non-formation area 383,384] In the radial direction of the diaphragm 220, there is an electrode-free region 383 between the lower electrode 341 and the lower electrode 342 where no electrodes are formed. In the radial direction of the diaphragm 220, there is an electrode-free region 384 between the lower electrode 342 and the lower electrode 343 where no electrodes are formed.

[0022] [Upper piezoelectric layer 360] The upper piezoelectric layer 360 is a piezoelectric thin film and is formed on the lower electrode layer 340. The lower piezoelectric layer 360 is formed continuously in the radial direction of the diaphragm 220.

[0023] [Top electrode layer 330] The upper electrode layer 330 has upper electrodes 331 to 333, which are electrode thin films. The upper electrode layer 330 is formed on the upper piezoelectric layer 360. The upper electrodes 331 to 333 are spaced apart in the X-axis direction. Upper electrode 331 is circular in shape. When viewed in the Z-axis direction, upper electrode 331 is positioned close to the center C11 of the diaphragm 220. Upper electrode 332 is ring-shaped when viewed in the Z-axis direction. Upper electrode 332 is positioned outside upper electrode 331 in the radial direction. Upper electrode 333 is ring-shaped when viewed in the Z-axis direction. Upper electrode 333 is positioned outside upper electrode 432 in the radial direction. Although the shape of upper electrode 331 is circular, it may be approximately circular including ellipses or polygons to match the shape of the diaphragm 220.

[0024] [Materials and thickness of piezoelectric thin films] 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 aluminum nitride (ScAlN (Sc: 1-60 at%)). The piezoelectric material used as the lower piezoelectric layer 460 may be, for example, 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).

[0025] The thickness of the lower piezoelectric layer 460 may be, for example, 100 nm or more and 1 μm or less. The material of the lower piezoelectric layer 460 may be, for example, ScAlN (Sc: 40 at%), and the thickness of the lower piezoelectric layer 460 may be, for example, 500 nm.

[0026] The thickness of the upper piezoelectric layer 360 may be, for example, 100 nm or more and 1 μm or less. The material of the upper piezoelectric layer 360 may be, for example, ScAlN (Sc: 40 at%), and the thickness of the upper piezoelectric layer 360 may be, for example, 500 nm.

[0027] [Seed membrane 370, 470] The diaphragm 220 may include seed films 370 and 470. The lower electrode layer 440 is formed on the seed film 470. The seed film 370 is formed on the intermediate layer 90, and the lower electrode layer 340 is formed on the seed film 370.

[0028] [Materials and thickness of seed membranes 370 and 470] The material for seed films 370 and 470 may be aluminum nitride (AlN) or scandium aluminum nitride (ScAlN (Sc: 1-60 at%)). The film thickness of seed films 370 and 470 may be, for example, 5 nm to 500 nm. In the example, the material for seed films 370 and 470 is aluminum nitride (AlN), and the film thickness of seed films 370 and 470 is 5 nm.

[0029] The diaphragm 220 is equipped with seed films 370 and 470, which makes it easier to control the crystallinity of the piezoelectric layer. The seed films 370 and 470 are, for example, AlN.

[0030] [Material and thickness of electrode thin film] The material of the electrode thin film in the upper electrode layers 330, 430 and the lower electrode layers 340, 440 may be, for example, aluminum (Al), molybdenum (Mo), platinum (Pt), titanium (Ti), titanium nitride (TiN), or gold (Au). The thickness of the electrode thin film may be, for example, 5 nm to 100 nm. The thickness of the electrode thin film may also be, for example, 20 nm. The electrode thin films in the upper electrode layers 330, 430 and the lower electrode layers 340, 440 may be formed from the same material or from different materials.

[0031] [Material and thickness of the intermediate layer 90] The intermediate layer 90 is formed from, for example, a low-density material. Examples of low-density materials include silicon dioxide (SiO2), polysilicon (Poly-Si), aluminum (Al), aluminum nitride (AlN), silicon nitride (Si3N4), scandium aluminum nitride (ScAlN), aluminum oxide (Al2O3), and titanium (Ti). The intermediate layer 90 may be formed from the same material as the electrode thin films of the lower electrode layers 340, 440 and the upper electrode layers 330, 430.

[0032] The thickness of the intermediate layer 90 may be, for example, between 10 nm and 3000 nm. The material of the intermediate layer 90 may be, for example, SiO2, and the thickness of the intermediate layer 90 may be, for example, 1450 nm.

[0033] [First detection area, non-detection area, and second detection area] The diaphragm, or vibrating plate 220, as shown in Figures 4 and 5, comprises first detection regions 323, 423, non-detection regions 324, 424, and second detection regions 325, 425. The first detection regions 323, 423 and the second detection regions 325, 425 are regions where a physical quantity can be detected. The non-detection regions 324, 424 are regions where a physical quantity is not detected. The physical quantity is, for example, sound pressure.

[0034] The first detection region 323 is a region in the Z-axis direction where the lower electrode 341, the upper piezoelectric layer 360, and the upper electrode 331 overlap. The first detection region 423 is a region in the Z-axis direction where the lower electrode 441, the lower piezoelectric layer 460, and the upper electrode 431 overlap. The acoustic converter 200 can detect the piezoelectric output charge between the lower electrode 441 and the upper electrode 431. The acoustic converter 200 can detect the piezoelectric output charge between the lower electrode 341 and the upper electrode 331.

[0035] The non-detection region 324 includes the region where the lower electrode 342, the upper piezoelectric layer 360, and the upper electrode 332 overlap in the Z-axis direction. The non-detection region 424 includes the region where the lower electrode 442, the upper piezoelectric layer 460, and the upper electrode 432 overlap in the Z-axis direction. The acoustic converter 200 cannot detect the piezoelectric output charge between the lower electrode 442 and the upper electrode 432. The acoustic converter 200 cannot detect the piezoelectric output charge between the lower electrode 342 and the upper electrode 332.

[0036] The second detection region 325 is the region in the Z-axis direction where the lower electrode 343, the upper piezoelectric layer 360, and the upper electrode 333 overlap. The second detection region 425 is the region in the Z-axis direction where the lower electrode 443, the lower piezoelectric layer 460, and the upper electrode 433 overlap. The acoustic converter 200 can detect the piezoelectric output charge between the lower electrode 443 and the upper electrode 433. The acoustic converter 200 can detect the piezoelectric output charge between the lower electrode 343 and the upper electrode 333.

[0037] The first detection regions 323, 423 are formed at a position that includes the center of the diaphragm 220. The non-detection regions 324, 424 are formed radially around the diaphragm 220, outside the first detection regions 323, 423. The second detection regions 325, 425 are formed radially around the diaphragm 220, outside the non-detection region 324.

[0038] [Outer diameter of the first detection area 323, the non-detection area 324, and the second detection area 325] As shown in Figure 1, the outer diameter Φ323 of the first detection area 323 is, for example, 0.54 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 1 mm.

[0039] [Split position] As shown in Figure 5, electrode-free regions 483 and 484 are formed in the lower electrode layer 440. Electrode-free regions 481 and 482 are formed in the upper electrode layer 430. Electrode-free regions 383 and 384 are formed in the lower electrode layer 340. Electrode-free regions 381 and 382 are formed in the upper electrode layer 330.

[0040] The electrode-free regions 381-384 and 481-484 may also be called "divided positions." These electrode-free regions 381-384 and 481-484 are located at different positions in the radial direction of the diaphragm 220.

[0041] The electrode-free region 481 is located inward of the electrode-free region 483 in the radial direction of the diaphragm 220. The electrode-free region 482 is located outward of the electrode-free region 484 in the radial direction of the diaphragm 220.

[0042] The electrode-free region 383 is located inward of the electrode-free region 481 in the radial direction of the diaphragm 220. The electrode-free region 384 is located outward of the electrode-free region 482 in the radial direction of the diaphragm 220.

[0043] The electrode-free region 381 is located inward of the electrode-free region 383 in the radial direction of the diaphragm 220. The electrode-free region 382 is located outward of the electrode-free region 384 in the radial direction of the diaphragm 220.

[0044] In the diaphragm 220, multiple electrode-free regions 381-384 and electrode-free regions 481-484 are formed in positions that do not overlap with each other when viewed in the Z-axis direction. This suppresses a decrease in the strength of the diaphragm 220. Piezoelectric thin films are formed in electrode-free regions 381-384 and electrode-free regions 481-484.

[0045] The crystallinity of the piezoelectric thin film above the boundary between the end of the lower electrode 441 and the electrode-free region 483 is lower compared to the crystallinity of the piezoelectric thin film above the lower electrode 441. Similarly, the crystallinity of the piezoelectric thin film above the boundary between the electrode and the electrode-free region is lower compared to the crystallinity of the piezoelectric thin film above the electrode.

[0046] The division position, which is the electrode-free region 483, is located outside the first detection region 423 in the radial direction of the diaphragm 220. The division position, which is the electrode-free region 484, is located inside the second detection region 425 in the radial direction of the diaphragm 220. This does not hinder the crystal growth of the piezoelectric thin film that generates charge. In the acoustic converter 200, the piezoelectric thin film in the first detection region 423 and the second detection region 425 that generate charge has high crystallinity.

[0047] The division position, which is the electrode-free region 383, is located outside the first detection region 323 in the radial direction of the diaphragm 220. The division position, which is the electrode-free region 384, is located inside the second detection region 325 in the radial direction of the diaphragm 220. This does not hinder the crystal growth of the piezoelectric thin film that generates charge. In the acoustic converter 200, the piezoelectric thin film in the first detection region 423 and the second detection region 425 that generate charge has high crystallinity.

[0048] In the first embodiment, in the diaphragm 220, multiple electrode-free regions 381-384 and electrode-free regions 481-484 are formed in positions that do not overlap with each other when viewed in the Z-axis direction. However, in each laminate 300, 400, the multiple electrode-free regions 381-384 and electrode-free regions 481-484 may overlap with each other when viewed in the Z-axis direction, and between the laminate 300 and 400, the multiple electrode-free regions 381-384 and electrode-free regions 481-484 do not need to overlap with each other when viewed in the Z-axis direction. Furthermore, the regions where each piezoelectric element is formed that overlap in the Z-axis direction do not need to be formed symmetrically with respect to the intermediate layer 90.

[0049] [Effects of the sound conversion device 200 according to the first embodiment] The acoustic converter 200 according to the first embodiment includes a support substrate 211 having an opening 221, and a diaphragm 220 provided on the support substrate 211 so as to cover the opening 221, which deforms in response to sound pressure and generates an electric charge. The diaphragm 220 has first detection regions 323, 423 located near the center C11 of the opening 221 and capable of detecting an electric charge, non-detection regions 324, 424 located outside the first detection regions 323, 423 in the radial direction of the diaphragm 220 (the radial direction of the opening 221) and not capable of detecting an electric charge, and second detection regions 325, 425 located outside the non-detection regions 324, 424 in the radial direction of the opening 221 and capable of detecting an electric charge.

[0050] In this embodiment, the acoustic converter 200 generates an electric charge in response to the deformation of the diaphragm 220, and detects the charges generated in the first detection regions 323, 423 and the second detection regions 325, 425. In the acoustic converter 200, the electrodes divide the diaphragm 220 in the radial direction, thereby forming the first detection regions 323, 423, the non-detection regions 324, 424, and the second detection regions 325, 425. Such an acoustic converter 200 can improve the sensitivity of charge detection in response to sound pressure.

[0051] Figure 6 is a side view illustrating the distribution of electric charge generated on a diaphragm 220 that deforms under sound pressure. In the diaphragm 220, the radially outer peripheral edge is fixed to the support substrate 211. As shown in Figure 6, the area near the inflection point P12 is difficult to deform and therefore does not generate electric charge. The region near the inflection point P12 where no electric charge is generated is included in the second detection regions 325 and 425.

[0052] In contrast, the region including the center C11 of the diaphragm 220 and the vicinity of the outer edge 222 of the diaphragm 220 exhibit large deformation and generate a large amount of charge. The region including the center C11 of the diaphragm 220 and its surrounding area are included in the first detection region 323,423. The vicinity of the outer edge 222 of the diaphragm 220 is included in the second detection region 325,425. In the acoustic converter 200, the region including the inflection point P12, where charge generation is small, is not included in the first detection region 323,423 and the second detection region 325,425. As a result, the signal-to-noise ratio can be improved in the acoustic converter 200, and the sensitivity of charge detection can be increased.

[0053] Furthermore, in the acoustic converter 200, the diaphragm 220 has lower electrode layers 340, 440, piezoelectric layers 360, 460 formed on the lower electrode layers 340, 440, and upper electrode layers 330, 430 formed on the piezoelectric layers 360, 460. The lower electrode layers 340, 440 have lower electrodes 341, 441 for the first detection regions 323, 423, lower electrodes 342, 442 for the non-detection regions 324, 424, and lower electrodes 343, 443 for the second detection regions 325, 425. The upper electrode layer 330 has upper electrodes 331, 431 for the first detection regions 323, 423, upper electrodes 332, 432 for the non-detection region 324, and upper electrodes 333, 433 for the second detection regions 325, 425.

[0054] In the acoustic converter 200 with this configuration, the lower electrodes 342, 442 and upper electrodes 332, 432 are formed in the non-detection regions 324, 424, thereby improving the rigidity of the diaphragm 220 compared to a case where electrodes are not formed in the non-detection regions. As a result, the acoustic converter 200 can improve the resonant frequency when the diaphragm 220 deforms under sound pressure. Consequently, the sensitivity of the acoustic converter 200 can be improved.

[0055] In the acoustic converter 200, the lower electrode layers 340, 440 have electrode-free regions (first lower non-electrode regions) 383, 483 formed between the lower electrodes 341, 441 of the first detection regions 323, 423 and the lower electrodes 342, 442 of the non-detection regions 324, 424 in the radial direction (X-axis direction and Y-axis direction) of the diaphragm 220, and (second lower non-electrode regions) 384, 484 formed between the lower electrodes 343, 443 of the second detection regions 325, 425 and the lower electrodes 342, 442 of the non-detection regions 324, 424. The upper electrode layers 330, 430 have, in the radial direction of the diaphragm 220, electrode-free regions (first upper non-electrode regions) 381, 481 formed between the upper electrodes 331, 431 of the first detection regions 323, 423 and the upper electrodes 332, 432 of the non-detection regions 324, 424, and electrode-free regions (second upper non-electrode regions) 382, ​​482 formed between the upper electrodes 333, 433 of the second detection regions 325, 425 and the upper electrodes 332, 432 of the non-detection regions 324, 424. The electrode-free regions (first upper non-electrode regions) 381, 481 have portions that do not overlap with the electrode-free regions (first lower non-electrode regions) 383, 483 when viewed in the Z-axis direction (thickness direction of the diaphragm 220), and the electrode-free regions (second upper non-electrode regions) 382, ​​482 have portions that do not overlap with the electrode-free regions (second lower non-electrode regions) 384, 484 when viewed in the Z-axis direction.

[0056] In the acoustic converter 200 with this configuration, the electrode-free regions 381-384 and 481-484 are arranged so as not to overlap when viewed in the Z-axis direction. This ensures mechanical strength against deformation of the lower electrode layers 340, 440 and the upper electrode layers 330, 430. Furthermore, a step may occur at the boundary between the electrode-free regions 381-384 and 481-484 and the electrodes, and the crystallinity of the piezoelectric thin film may be low above this boundary. In such regions of the piezoelectric thin film, charge may not be efficiently generated. In the acoustic converter 200, since the electrode-free regions 381-384 and 481-484 are formed so as not to overlap, regions with low crystallinity can be prevented from overlapping. Therefore, regions where charge cannot be efficiently generated can be dispersed in the radial direction of the diaphragm 220, suppressing a decrease in detection sensitivity in the acoustic converter 200.

[0057] In the acoustic converter 200, the electrode-free regions (first upper non-electrode regions) 381, 481 are located inward of the electrode-free regions (first lower non-electrode regions) 383, 483 in the radial direction of the diaphragm 220, while the electrode-free regions (second upper non-electrode regions) 382, ​​482 are located outward of the electrode-free regions (second lower non-electrode regions) 384, 484.

[0058] In the acoustic converter 200 with this configuration, the boundaries between the electrode-free regions 381-384 and 481-484 and the electrodes are arranged so that they do not overlap. This suppresses a decrease in the mechanical strength of the diaphragm 220. Furthermore, in the acoustic converter 200, regions with low crystallinity are formed so that they are not included in the first detection region 323 and the second detection region 325. As a result, a decrease in the detection sensitivity of the acoustic converter 200 is suppressed.

[0059] In the acoustic converter 200, the diaphragm 220 comprises a plurality of laminates 300, 400 having lower electrode layers 340, 440, piezoelectric layers 360, 460, and upper electrode layers 330, 430. The plurality of laminates 300, 400 are stacked in the Z-axis direction. Laminate 300 has a lower electrode layer 340, an upper piezoelectric layer 360, and an upper electrode layer 330. Laminate 400 has a lower electrode layer 440, an upper piezoelectric layer 460, and an upper electrode layer 430.

[0060] In an acoustic converter 200 with this configuration, the signal-to-noise ratio can be increased by the bimorph effect, thereby improving detection sensitivity.

[0061] The acoustic converter 200 includes an intermediate layer 90 positioned between multiple laminates 300 and 400 in the Z-axis direction. In this configuration of the acoustic converter 200, the laminates 300 and 400 are spaced apart in the Z-axis direction. This allows for a higher bimorph effect, a larger signal-to-noise ratio, and improved detection sensitivity.

[0062] Furthermore, in the acoustic converter 200, the piezoelectric layers 360 and 460 may be aluminum nitride or scandium aluminum nitride. In an acoustic converter 200 with this configuration, the piezoelectric response when the acoustic converter 200 deforms in response to sound pressure can be improved. In an acoustic converter 200 with this configuration, the piezoelectric effect can be further enhanced.

[0063] [Shape of the electrode ends] Next, the shape of the electrode ends will be described. Figure 7 is a partially enlarged cross-sectional view illustrating an enlarged portion of the diaphragm. As shown in Figure 7, the ends of the upper electrodes 331, 332 and the lower electrode 341 may have a tapered shape. Similarly, the ends of the other upper electrodes 333, 431-433 and the lower electrodes 343, 441-443 may also have a tapered shape. The electrode ends are the ends facing each other in the radial direction of the diaphragm 220. The tapered shape of the electrode ends is formed so that the lower side protrudes more than the upper side.

[0064] Thus, by having tapered ends for the lower electrodes 341 and 342, the step at the boundary between the lower electrodes 341 and 342 and the electrode-free region 383 can be made gentler. Therefore, a decrease in crystallinity in the piezoelectric layer 360 can be suppressed. The same applies to the boundaries between other electrodes and electrode-free regions.

[0065] [Acoustic converter 200B according to the second embodiment] Next, the acoustic converter 200B according to the second embodiment will be described. Figure 8 is a plan view illustrating the acoustic converter 200B according to the second embodiment. Figure 9 is a cross-sectional view illustrating the acoustic converter according to the second embodiment, and is a cross-sectional view along the line IX-IX in Figure 8. The differences between the acoustic converter 200B according to the second embodiment shown in Figures 8 and 9 and the acoustic converter 200 according to the first embodiment shown in Figure 1 are that it includes a plurality of upper electrodes 331B, 333B, 431B, 433B divided in the circumferential direction, a plurality of lower electrodes 341B, 343B, 441B, 443B divided in the circumferential direction, and electrode-free regions 385, 386 extending in the radial direction. Note that in the description of the acoustic converter 200B according to the second embodiment, explanations similar to those in the description of the acoustic converter 200 according to the first embodiment may be omitted.

[0066] [Laminate 300B] The acoustic converter 200B comprises laminates 300B and 400B, as shown in Figure 9. Laminate 300B has an upper electrode layer 330B, a piezoelectric layer 360, and a lower electrode layer 340B. The upper electrode layer 330B has a plurality of upper electrodes 331B, upper electrodes 332, and a plurality of upper electrodes 333B divided in the circumferential direction.

[0067] [First detection area 323B] The laminate 300B has a first detection region 323B, a non-detection region 324, and a second detection region 325B. The first detection region 323B has a plurality of upper electrodes 331B, a piezoelectric layer 360, and a plurality of lower electrodes 341B. The first detection region 323B includes a plurality of piezoelectric elements. In the first detection region 323B, the piezoelectric elements have an upper electrode 331B, a piezoelectric layer 360, and a lower electrode 341B.

[0068] [Second detection area 325B] The second detection region 325B has a plurality of upper electrodes 333B, a piezoelectric layer 360, and a plurality of lower electrodes 343B. The second detection region 325B includes a plurality of piezoelectric elements. In the second detection region 325B, the piezoelectric elements have an upper electrode 333B, a piezoelectric layer 360, and a lower electrode 343B.

[0069] The upper electrode layer 330B includes electrode-free regions 381, 383 and electrode-free regions 385, 386, as shown in Figure 8.

[0070] [Electrode non-formation area 385] The electrode-free region 385 divides the upper electrode into multiple parts in the first detection region 323B. The electrode-free region 385 extends radially from the center of the diaphragm 220. The multiple electrode-free regions 385 are arranged at equal intervals in the circumferential direction. The areas of the multiple upper electrodes 331B are equal. The acoustic converter 200B has, for example, 10 upper electrodes 331B.

[0071] [Electrode non-formation area 386] The electrode-free region 386 divides the upper electrode into multiple parts in the second detection region 325B. The electrode-free region 386 extends radially from the electrode-free region 382 toward the outer edge 222 of the diaphragm 220. The multiple electrode-free regions 386 are arranged at equal intervals in the circumferential direction. The areas of the multiple upper electrodes 333B are equal. The acoustic converter 200B has, for example, 12 upper electrodes 333B.

[0072] The lower electrode layer 340B, like the upper electrode layer 330B, includes a radially extending electrode-free region.

[0073] [Laminate 400B] As shown in Figure 9, the laminate 400B has an upper electrode layer 430B, a piezoelectric layer 460, and a lower electrode layer 440B. The upper electrode layer 430B has a plurality of upper electrodes 431B, upper electrodes 432, and a plurality of upper electrodes 433B divided in the circumferential direction.

[0074] [First detection area 423B] The laminate 400B has a first detection region 423B, a non-detection region 424, and a second detection region 425B. The first detection region 423B has a plurality of upper electrodes 431B, a piezoelectric layer 460, and a plurality of lower electrodes 441B. The first detection region 423B includes a plurality of piezoelectric elements. In the first detection region 423B, the piezoelectric elements have an upper electrode 431B, a piezoelectric layer 460, and a lower electrode 441B. In the first detection region 423B, the areas of the plurality of upper electrodes 431B are equal to each other. In the first detection region 423B, the areas of the plurality of lower electrodes 441B are equal to each other.

[0075] [Second detection area 425B] The second detection region 425B has a plurality of upper electrodes 433B, a piezoelectric layer 460, and a plurality of lower electrodes 443B. The second detection region 425B includes a plurality of piezoelectric elements. In the second detection region 425B, the piezoelectric elements have an upper electrode 433B, a piezoelectric layer 460, and a lower electrode 443B. In the second detection region 425B, the areas of the plurality of upper electrodes 433B are equal to each other. In the second detection region 425B, the areas of the plurality of lower electrodes 443B are equal to each other.

[0076] The upper electrode layer 430B and the lower electrode layer 440 of the laminate 400B include radially extending electrode-free regions, similar to the laminate 300B.

[0077] [Capacitance of piezoelectric element] In the laminate 300B, the capacitances of the multiple piezoelectric elements arranged in the circumferential direction of the diaphragm 220 are equal to each other. In the laminate 400B, the capacitances of the multiple piezoelectric elements arranged in the circumferential direction of the diaphragm 220 are equal to each other.

[0078] [Series connection of multiple piezoelectric elements] In the diaphragm 220B, multiple piezoelectric elements arranged in the circumferential direction are electrically connected in series.

[0079] [Effects of the sound converter 200B according to the second embodiment] The sound converter 200B according to this second embodiment also provides the same effects and advantages as the sound converter 200 according to the first embodiment described above.

[0080] In the acoustic converter 200B, the lower electrode layers 340B, 440B of the first detection regions 323B, 423B include a plurality of lower electrodes (multiple parts) 341B, 441B arranged in the circumferential direction of the diaphragm 220B; the lower electrode layers 340B, 440B of the second detection regions 325B, 425B include a plurality of lower electrodes (multiple parts) 343B, 443B arranged in the circumferential direction of the diaphragm 220B; the upper electrode layers 330B, 430B of the first detection regions 323B, 423B include a plurality of upper electrodes (multiple parts) 331B, 431B arranged in the circumferential direction of the diaphragm 220; and the upper electrode layers 330B, 430B of the second detection regions 325B, 425B include a plurality of upper electrodes (multiple parts) 333B, 433B arranged in the circumferential direction of the diaphragm 220. The area of ​​each of the multiple lower electrodes 341B, 441B contained in the lower electrode layers 340B, 440B of the first detection regions 323B, 423B may be the same as the area of ​​each of the multiple lower electrodes 343B, 443B contained in the lower electrode layers 340B, 440B of the second detection regions 325B, 425B. The area of ​​each of the multiple upper electrodes 331B, 431B contained in the upper electrode layers 330B, 430B of the first detection regions 323B, 423B may be the same as the area of ​​each of the multiple upper electrodes 333B, 433B contained in the upper electrode layers 330B, 430B of the second detection regions 325B, 425B. "Same" includes "approximately the same".

[0081] According to the acoustic converter 200B with this configuration, by making the areas of multiple electrodes equal, the design freedom of amplification circuits and the like connected to multiple piezoelectric elements having these electrodes can be increased. Specifically, when connecting the capacitances of piezoelectric elements having electrodes arranged above and below the piezoelectric layer 360 and piezoelectric layer 460 in series, it becomes easier to calculate the capacitance of the multiple piezoelectric elements compared to when the areas of the divided multiple electrodes are not equal. Therefore, the circuit design of amplification circuits and the like designed based on the total capacitance of the diaphragm 220B becomes easier.

[0082] Furthermore, when multiple capacitances are electrically connected in series, if the areas of the divided electrodes are not equal, the charge generated at each capacitance will differ when subjected to sound pressure. In such cases, excess charge may be generated, which may reduce the overall detection accuracy of the diaphragm 220. In the acoustic converter 200B, since the areas of the multiple electrodes are equal, the generation of excess charge is suppressed. As a result, the reduction in the overall detection accuracy of the diaphragm 220B can be suppressed.

[0083] [Circuit diagram of the sound converter 200B according to the second embodiment] Next, the circuit diagram of the sound converter 200B according to the second embodiment will be described. Figure 10 is the circuit diagram of the sound converter 200B according to the second embodiment.

[0084] As shown in Figure 10, the acoustic converter 200B has a MEMS microphone chip 201. The MEMS microphone chip 201 is equipped with a diaphragm 220B. The diaphragm 220B has a plurality of first detection regions 323B, 423B and second detection regions 325B, 425B.

[0085] Multiple first detection regions 323B, 423B each have an upper electrode 331B, a lower electrode 341B, an upper electrode 431B, and a lower electrode 441B. Multiple second detection regions 325B, 425B each have an upper electrode 333B, a lower electrode 343B, an upper electrode 433B, and a lower electrode 443B.

[0086] In the first detection regions 323B and 423B of the acoustic converter 200B, the piezoelectric output charge between the upper electrode 331B and the lower electrode 341B, and the piezoelectric output charge between the upper electrode 431B and the lower electrode 441B can be detected. Multiple piezoelectric elements arranged in the circumferential direction are connected in series.

[0087] In the second detection regions 325B and 425B of the acoustic converter 200B, the piezoelectric output charge between the upper electrode 333B and the lower electrode 343B, and the piezoelectric output charge between the upper electrode 433B and the lower electrode 443B can be detected. Multiple piezoelectric elements arranged in the circumferential direction are connected in series.

[0088] Furthermore, the MEMS microphone chip 201 has pads 213 and 214. Multiple piezoelectric elements are connected to the electrodes of the pads 213 and 214. The acoustic converter 200B includes an IC 202 connected to pad 213. IC 202 is an amplifier that amplifies the output signal of the piezoelectric element of the diaphragm 220. IC 202 may also be provided with a function to perform AD (analog-to-digital) conversion after amplifying the output signal of the piezoelectric element of the diaphragm 220.

[0089] The polarity of the charge generated in the second detection region 325B,425B is the opposite of the polarity of the charge generated in the first detection region 323B,423B. Therefore, the second detection region 325B,425B and the first detection region 323B,423B are connected in series with the wiring reversed.

[0090] [Acoustic converter 200C according to the third embodiment] Next, the acoustic converter 200C according to the third embodiment will be described. Figure 11 is an exploded perspective view illustrating the acoustic converter 200C according to the third embodiment. The difference between the acoustic converter 200C according to the third embodiment shown in Figure 11 and the acoustic converter 200B according to the second embodiment is that an opening 91 is formed in the intermediate layer 90C. Note that in the description of the acoustic converter 200C according to the third embodiment, explanations similar to those given in the descriptions of the acoustic converters 200 and 200B according to the above embodiments may be omitted.

[0091] The diaphragm 220C of the acoustic converter 200C according to the third embodiment includes an intermediate layer 90C in which an opening 91 is formed. The opening 91 is formed on the inside in the radial direction of the diaphragm 220C. The opening 91 penetrates in the Z-axis direction. The peripheral edge of the opening 91 is formed on the inside of the electrode-free region 381 in the radial direction of the diaphragm 220C.

[0092] The opening 91 is circular when viewed in the Z-axis direction. The interior of the opening 91 is hollow, and no other objects are placed inside. The shape of the opening 91 is not limited to a circle. The shape of the opening 91 may be, for example, a polygon, a ring shape arranged concentrically, or an ellipse. In addition, multiple openings may be formed in the intermediate layer 90C.

[0093] In the acoustic converter 200C according to this third embodiment, the weight of the intermediate layer 90C can be reduced. In other words, the weight of the diaphragm 220C can be reduced. This makes it possible to improve the resonant frequency of the diaphragm 220C and improve the sensitivity of the acoustic converter 200C.

[0094] [Acoustic converter 200D according to the fourth embodiment] Next, the acoustic converter 200D according to the fourth embodiment will be described. Figure 12 is an exploded perspective view illustrating the acoustic converter 200D according to the fourth embodiment. The difference between the acoustic converter 200D according to the fourth embodiment shown in Figure 12 and the acoustic converter 200C according to the third embodiment is that it includes an intermediate layer 90D having a plurality of pillars 92. In the description of the acoustic converter 200D according to the fourth embodiment, explanations similar to those given in the descriptions of the acoustic converters 200, 200B, and 200C according to the above embodiments may be omitted.

[0095] The diaphragm 220D of the acoustic converter 200D according to the fourth embodiment includes an intermediate layer 90D having a plurality of pillars 92. The pillars 92 are cylindrical in shape. The direction of the centerlines of the plurality of pillars 92 is along the Z-axis direction. Gaps are formed around the plurality of pillars 92. The plurality of pillars 92 are formed on the upper electrodes 431B, 432, and 433B.

[0096] The shape of the pillar 92 is not limited to a cylindrical shape. For example, the pillar 92 may be prismatic, cylindrical, or rectangular.

[0097] In the acoustic converter 200D according to this fourth embodiment, the weight of the intermediate layer 90D can be reduced. In other words, the weight of the diaphragm 220D can be reduced. This makes it possible to improve the resonant frequency of the diaphragm 220D and improve the sensitivity of the acoustic converter 200D.

[0098] [Sound conversion device 200E related to a modified example] Next, a modified acoustic converter 200E will be described. Figure 15(a) is a partially exploded perspective view illustrating a modified acoustic converter 200E, and Figure 15(b) is an enlarged view illustrating an enlarged intermediate layer 90E. The modified acoustic converter 200E may include a porous intermediate layer 90E. Multiple cavities may be formed in the intermediate layer 90E. Multiple uneven shapes may also be formed in the intermediate layer 90E. Multiple openings may also be formed in the intermediate layer 90E. The openings may or may not penetrate the intermediate layer 90E in the Z-axis direction.

[0099] In the modified acoustic converter 200E, the weight of the intermediate layer 90E can be reduced, thereby reducing the weight of the diaphragm 220E. This improves the resonant frequency of the diaphragm 220E and improves the sensitivity of the acoustic converter 200E.

[0100] [Sound conversion device 200B related to a modified example] Figure 13 is a plan view illustrating a modified acoustic converter 200B. As shown in Figure 13, the diaphragm 220B of the acoustic converter 200B may have vent holes 93 formed therein. The vent holes 93 are through holes formed in the diaphragm for degassing. The vent holes 93 penetrate the diaphragm 220B in the Z-axis direction.

[0101] The vent hole 93 is provided, for example, at the center of the diaphragm 220B. The vent hole 93 is provided, for example, in the non-detection regions 324,424. The diaphragm 220B may have one vent hole 93 or multiple vent holes 93.

[0102] [Interlayer thickness, signal-to-noise ratio, and resonant frequency] Next, we will explain the relationship between the thickness of the interlayer, the signal-to-noise ratio (SNR), and the resonant frequency. Figure 14 is a table showing the relationship between the thickness of the interlayer, the SNR, and the resonant frequency.

[0103] The signal-to-noise ratio (SNR) and resonant frequency were measured using the acoustic converter 200 according to Examples 1-11 and Comparative Examples 1-7. The acoustic converter 200 according to Examples 1-11 and Comparative Examples 1-7 has the same configuration as the acoustic converter 200 according to the first embodiment described above, but differs in the material of the piezoelectric layer and the thickness of the intermediate layer. In Examples 1-5 and Comparative Examples 1-4, the piezoelectric layer material was AlN. In Examples 6-11 and Comparative Examples 5-7, the piezoelectric layer material was ScAlN. The thickness of the intermediate layer was changed as appropriate. As an evaluation result, a result above the reference value was evaluated as A, and a result below the reference value was evaluated as B. The acoustic converters according to the examples and comparative examples were placed in an anechoic chamber, and the SNR and resonant frequency were measured using an Audio Precision audio analyzer.

[0104] In Example 1, the signal-to-noise ratio (SNR) was high, and in Examples 2 and 3, the SNR was very high. In Examples 4 and 5, the resonant frequency was high. Examples 1 to 5 received an evaluation of A.

[0105] Examples 8-10 showed a high signal-to-noise ratio (SNR), and Examples 6 and 7 showed an extremely high SNR. Examples 9 and 10 showed a high resonant frequency, and Example 11 showed an extremely high resonant frequency.

[0106] [Relationship between sensing area diameter ratio and normalized SNR] Next, the relationship between the sensing area diameter ratio and the normalized SNR will be explained. Figure 16 is a graph showing the relationship between the sensing area diameter ratio and the normalized SNR. In Figure 16, the horizontal axis shows the sensing area diameter ratio [%], and the vertical axis shows the normalized SNR [%]. The graph shown in Figure 16 shows the relationship between the sensing area diameter ratio and the normalized SNR in the acoustic converter 200 according to the first embodiment shown in Figure 1.

[0107] The "percentage of sensing area" can be expressed by the following formula (1). Sensing area ratio = (radius of electrode separation part / diaphragm radius) × 100 ... (1) The "electrode separation radius" may also be the radius of the inner detection region 323. The "diaphragm radius" may also be the radius of the diaphragm 220. In Figure 1, the diameter φ323 of the inner detection region 323 and the diameter φ325 of the diaphragm 220 are shown.

[0108] The inner diameter of the opening 221 covered by the diaphragm 220 was defined as 100% of the sensing area diameter ratio. A normalized SNR of 100% was defined as the case where an electrode-free area was formed in 71% of the area. In Figure 16, "○" indicates the position of the boundary between the inner detection area 323 and the non-detection area 324. In Figure 16, "×" indicates the position of the boundary between the outer detection area 325 and the non-detection area 324.

[0109] The SNR normalized value of the inner detection region 323 is the value obtained when the outer diameter Φ323 of the inner detection region 323 is varied, with the boundary between the outer detection region 325 and the non-detection region 324 set at 71%.

[0110] The SNR normalized value of the outer detection region 325 is the value obtained when the boundary between the inner detection region 323 and the non-detection region 324 is set to 71%, and the inner diameter Φ324 of the outer detection region 325 is varied.

[0111] In the example shown in Figure 16, the normalized SNR value of the inner detection region 323 was maximized at point P21. The sensing region diameter ratio at point P21 was 59%.

[0112] In the example shown in Figure 16, the normalized SNR value of the outer detection region 325 was maximized at point P22. The sensing region diameter ratio at point P22 was 81%.

[0113] When the sensing area diameter ratio of the inner detection area 323 was between 44% and 71%, the SNR normalized value was 100% or higher. When the sensing area diameter ratio of the inner detection area 323 was between 49% and 67%, the SNR normalized value was 104% or higher. When the sensing area diameter ratio of the inner detection area 323 was between 51% and 65%, the SNR normalized value was 106% or higher.

[0114] The ratio of the sensing area diameter of the inner detection area 323 is preferably 44% to 71%, more preferably 49% to 67%, and even more preferably 51% to 65%.

[0115] When the sensing area diameter ratio of the outer detection area 325 was between 71% and 89%, the SNR normalized value was 100% or higher. When the sensing area diameter ratio of the outer detection area 325 was between 75% and 87%, the SNR normalized value was 104% or higher. When the sensing area diameter ratio of the outer detection area 325 was between 78% and 84%, the SNR normalized value was 106% or higher.

[0116] The ratio of the sensing area diameter of the outer detection area 325 is preferably 71% to 89%, more preferably 75% to 87%, and even more preferably 78% to 84%.

[0117] The case where the sensing area diameter ratio of the inner detection area 323 is 71% and the sensing area diameter ratio of the outer detection area 325 is 71% may also mean that the electrode division position is located at the 71% position.

[0118] In the acoustic converter 200, if 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 a value outside the range of 44% or more and 71% or less. In such cases, the SNR normalized value may be high.

[0119] In the acoustic converter 200, if 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 a value outside the range of 71% or more and 89% or less. In such cases, the SNR normalized value may be high.

[0120] Furthermore, other embodiments may be used in which other components are combined with the configurations listed in the above embodiments, and the present invention is not limited in any way to the configurations shown herein. In this regard, modifications can be made without departing from the spirit of the present invention, and can be appropriately determined according to the application form. [Explanation of Symbols]

[0121] 200, 200B, 200C, 200D, 200E: Acoustic converter, 90, 90C, 90D, 90E: Intermediate layer, 221: Aperture, 211: Support substrate, 220, 220B, 220C, 220D, 220E: Diaphragm, 222: Outer edge, 323, 323B, 423, 423B: First detection area, 324, 424: Non-detection area, 325, 325B, 425, 425B: Second detection area, 330, 330B, 430, 430B: Upper electrode layer, 331, 331B, 431, 431B: Upper electrode (upper electrode of the first detection area), 332, 432: Upper electrode (upper electrode of the non-detection area) Electrode), 333,333B,433,433B: Upper electrode (upper electrode of the second detection region), 340,340B,440,440B: Lower electrode layer, 341,341B,441,441B: Lower electrode (lower electrode of the first detection region), 342,442: Lower electrode (lower electrode of the non-detection region), 343,343B,443,443B: Lower electrode (lower electrode of the second detection region), 360: Upper piezoelectric layer (piezoelectric layer), 460: Lower piezoelectric layer (piezoelectric layer), 381~384: Non-electrode formed region, 481~484: Non-electrode formed region, X: X-axis direction, Y: Y-axis direction, Z: Z-axis direction (plate thickness direction).

Claims

1. A support substrate having an opening, The support substrate is provided so as to cover the opening, and includes a diaphragm that deforms in response to sound pressure and generates an electric charge, The aforementioned diaphragm is A first detection region is positioned near the center of the opening and capable of detecting electric charge, A non-detection region is located outside the first detection region in the radial direction of the opening and does not detect charge, An acoustic converter having a second detection region located outside the non-detection region in the radial direction of the opening and capable of detecting electric charge.

2. The aforementioned diaphragm is The lower electrode layer, A piezoelectric layer formed on the lower electrode layer, It has an upper electrode layer formed on the piezoelectric layer, The lower electrode layer is The lower electrode of the first detection region, The lower electrode of the non-detection region, The lower electrode of the second detection region is provided, The upper electrode layer is The upper electrode of the first detection region, The upper electrode of the non-detection region, The acoustic conversion device according to claim 1, further comprising the upper electrode of the second detection region.

3. The lower electrode layer is In the radial direction of the opening, a first lower non-electrode portion is formed between the lower electrode of the first detection region and the lower electrode of the non-detection region, The opening has a second lower non-electrode portion formed between the lower electrode of the second detection region and the lower electrode of the non-detection region in the radial direction of the opening, The upper electrode layer is In the radial direction of the opening, a first upper non-electrode portion is formed between the upper electrode of the first detection region and the upper electrode of the non-detection region, The opening has a second upper non-electrode portion formed between the upper electrode of the second detection region and the upper electrode of the non-detection region in the radial direction of the opening, The first upper non-electrode portion has a portion that does not overlap with the first lower non-electrode portion when viewed in the thickness direction of the support substrate. The acoustic conversion device according to claim 2, wherein the second upper non-electrode portion has a portion that does not overlap with the second lower non-electrode portion when viewed in the plate thickness direction.

4. The first upper non-electrode portion is positioned inward of the first lower non-electrode portion in the radial direction of the opening. The acoustic conversion device according to claim 3, wherein the second upper non-electrode portion is positioned outward from the second lower non-electrode portion in the radial direction of the opening.

5. The acoustic converter according to claim 2, wherein the ends of the lower electrode of the first detection region, the lower electrode of the non-detection region, the lower electrode of the second detection region, the upper electrode of the first detection region, the upper electrode of the non-detection region, and the upper electrode of the second detection region are tapered.

6. The lower electrode of the first detection region includes a plurality of portions arranged in the circumferential direction of the opening, The lower electrode of the second detection region includes a plurality of portions arranged in the circumferential direction of the opening, The upper electrode of the first detection region includes a plurality of portions arranged in the circumferential direction of the opening, The upper electrode of the second detection region includes a plurality of portions arranged in the circumferential direction of the opening, The area of ​​each of the plurality of parts included in the lower electrode of the first detection region is the same as the area of ​​each of the plurality of parts included in the lower electrode of the second detection region. The acoustic conversion device according to claim 2, wherein the area of ​​each of the plurality of parts included in the upper electrode of the first detection region is the same as the area of ​​each of the plurality of parts included in the upper electrode of the second detection region.

7. The diaphragm comprises a plurality of laminates having the lower electrode layer, the piezoelectric layer, and the upper electrode layer. The acoustic conversion device according to claim 2, wherein the plurality of laminates are laminated in the thickness direction of the diaphragm.

8. The acoustic conversion device according to claim 7, further comprising an intermediate layer disposed between the plurality of laminates in the thickness direction of the diaphragm.

9. The acoustic conversion device according to claim 2, wherein the piezoelectric layer comprises aluminum nitride or scandium aluminum nitride.

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