Piezoelectric element

Abstract

To provide a piezoelectric element capable of improving detection sensitivity. [Solution] The piezoelectric element comprises a support, a vibrating portion 20, and a connecting portion 30. The vibrating portion includes a piezoelectric film and an electrode film, and has a support region 21 supported by the support, and a floating region 22 that floats above the support and includes a plurality of vibrable vibrating regions 220. The plurality of electrode films include a support-side electrode film formed on the support region side and a vibrating-side electrode film formed on the vibrating region side. The connecting portion has a connecting wiring portion 33 that electrically connects the support-side electrode films of each of the plurality of electrode films. The support has a support substrate that supports the vibrating portion. The support substrate has a vibrating opening 10b that forms a plurality of vibrating regions, and a support forming portion provided on the support direction side of the vibrating opening and supporting the support region, with a support opening 10c formed in the support forming portion. At least a portion of the support-side electrode film is provided at a position that overlaps with the support opening in the stacking direction.

Description

Technical Field

[0001] The present disclosure relates to a piezoelectric element.

Background Art

[0002] Conventionally, a piezoelectric element having an SOI substrate composed of a support substrate, a BOX layer, and a silicon layer, an n-type region, and a conductor film is known (see, for example, Patent Document 1). In this piezoelectric element, a piezoelectric film formed on the SOI substrate is provided in a plurality of regions, and the conductor film is formed on the piezoelectric film across the plurality of regions. Further, the piezoelectric film is in a state where the end portions are supported and the central portion is not supported by cutting out the central portions of the support substrate and the BOX layer, and the central portion is vibratable within a certain range. Then, this piezoelectric element detects a sound wave propagated from the outside by detecting a potential difference generated between the n-type region, which is the lower electrode, and the conductor film, which is the upper electrode, when the piezoelectric film vibrates.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the piezoelectric element described in Patent Document 1, the conductor film, which is an electrode, is formed across a plurality of regions of the piezoelectric film, so that the piezoelectric films in the plurality of regions are electrically connected. Here, when an electrode is formed on the piezoelectric film, the potential of the portion where the electrode is formed on the piezoelectric film becomes the same potential as that of the electrode. That is, among the portions of the piezoelectric film that vibrate due to sound waves, the portion where the electrode is formed has the same potential as this electrode.

[0005] Consequently, when detecting changes in the potential difference of a piezoelectric film when it vibrates using electrodes, the charge at the site where the electrodes are formed on the piezoelectric film cannot be utilized. Therefore, when electrodes are formed across multiple piezoelectric films, if these electrodes are formed on the vibrating portion of the piezoelectric film, the voltage detected from the electrodes when the piezoelectric film vibrates will decrease compared to a configuration where electrodes are not formed on the vibrating portion. Therefore, in a configuration where electrodes are formed on the vibrating portion of the piezoelectric film, there is a risk that the detection sensitivity of the piezoelectric element when detecting sound waves will decrease.

[0006] Therefore, the inventors considered forming electrodes in areas of the piezoelectric film that are less prone to vibration, specifically in areas of the piezoelectric film supported by the substrate, in order to avoid the loss of charge in those areas. However, when electrodes are placed in areas of the piezoelectric film supported by the substrate, there is a risk of parasitic capacitance occurring between the substrate and these electrodes. If parasitic capacitance occurs between the substrate and the electrodes, and the potential of the piezoelectric film decreases when the piezoelectric film vibrates, there is a risk that the detection sensitivity of the piezoelectric element when detecting sound waves will decrease. This was discovered through the inventors' diligent research.

[0007] In view of the above points, this disclosure aims to provide a piezoelectric element capable of improving detection sensitivity. [Means for solving the problem]

[0008] According to one perspective of this disclosure, Piezoelectric elements are Support (10) and A vibrating part (20) is stacked on a support along a predetermined stacking direction and vibrates when pressure is applied from the outside, It comprises a connecting part (30) connected to a vibrating part, The vibrating part includes a piezoelectric film (60) that deforms under pressure, and a plurality of electrode films (70) connected to the piezoelectric film that extract the charge generated by the deformation of the piezoelectric film, and also has a support region (21) supported by a support body, and a floating region (22) connected to the support region and floating away from the support body. The floating region includes multiple vibrating regions (220), Each of the multiple vibration regions has a fixed end (221) that forms the boundary with the support region, and a free end (222) on the opposite side of the support end. Each of the multiple electrode films is formed spanning from a support region to one of the multiple vibration regions, and includes a support-side electrode film (70a) formed on the support region side and a vibration-side electrode film (70b) formed on the vibration region side. The connection portion is positioned on the support direction side of the support end in the vibrating portion, when the direction from the vibrating end toward the support end is defined as the support direction, and has a connection wiring portion (33) that electrically connects the support-side electrode films of each of the multiple electrode films. The support has a support substrate (11) that supports the vibrating part. The support substrate has vibration openings (10b) that form multiple vibration regions, and a support forming portion (111) provided on the support direction side of the vibration openings to support the support regions, and a support opening (10c) is formed in the support forming portion. The support electrode film is positioned such that at least a portion of it overlaps with the support opening in the stacking direction.

[0009] According to this, multiple electrode films can be electrically connected by connecting wiring sections placed in the support region. Therefore, when acquiring the potential of the piezoelectric film when it vibrates via the electrode films and connecting wiring sections, it is possible to avoid the loss of the charge at the site where the connecting wiring sections are formed on the electrode films. Consequently, the decrease in voltage detected when the piezoelectric film vibrates can be suppressed, and as a result, the detection sensitivity when the piezoelectric element detects sound waves can be improved compared to a configuration in which the connecting wiring sections are placed on the electrode films within the vibrating region.

[0010] Furthermore, by positioning the support electrode film in a location that overlaps with the support opening, it is possible to avoid the generation of parasitic capacitance between the support electrode film and the support substrate, thereby avoiding a reduction in the change in the potential difference of the piezoelectric film caused by the generation of parasitic capacitance. As a result, compared to a configuration in which the support substrate is located in a position that overlaps with the support electrode film in the stacking direction, the detection sensitivity when the piezoelectric element detects sound waves can be improved.

[0011] The reference numerals in parentheses attached to each component indicate an example of the correspondence between that component and the specific components described in the embodiments described later. [Brief explanation of the drawing]

[0012] [Figure 1] This is a top view of a piezoelectric element according to the first embodiment. [Figure 2] This is a cross-sectional view taken along line II-II in Figure 1. [Figure 3] This is a cross-sectional view taken along line III-III in Figure 1. [Figure 4] This is a cross-sectional view taken along line IV-IV in Figure 1. [Figure 5] This is a top view of the support according to the first embodiment. [Figure 6] This is an enlarged view of section VI in Figure 1. [Figure 7] This contour plot shows the simulation results of stress generated in the vibration region when the opening end of the floating opening is not uneven. [Figure 8] This contour plot shows the simulation results of stress generated in the vibration region when the opening end of a floating opening has an uneven shape. [Figure 9] This figure corresponds to Figure 6 of the piezoelectric element according to the second embodiment. [Figure 10] This figure shows the effect of changing the convex ratio on the detection sensitivity of the piezoelectric element. [Figure 11] This contour plot shows the simulation results of stress generated in the vibration region when the width dimension of the recess is increased. [Figure 12]This is a figure corresponding to FIG. 6 of the piezoelectric element according to the third embodiment. [Figure 13] This is a top view of a piezoelectric element according to another embodiment. [Figure 14] This is a top view of a piezoelectric element according to another embodiment.

Modes for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following embodiments, parts that are the same as or equivalent to those described in the preceding embodiments may be given the same reference numerals, and the description thereof may be omitted. Further, in the embodiments, when only a part of the components is described, the components described in the preceding embodiments can be applied to other parts of the components. The following embodiments can be partially combined with each other as long as there is no problem in the combination, even if not specifically stated.

[0014] (First Embodiment) The piezoelectric element 1 of the first embodiment will be described with reference to FIGS. 1 to 8. Note that the piezoelectric element 1 of this embodiment is preferably used as a microphone, for example. As shown in FIGS. 1 to 4, the piezoelectric element 1 of this embodiment includes a support 10, a vibration part 20 laminated on the support 10, and a connection part 30 connected to the vibration part 20. Hereinafter, as shown in FIG. 2 and the like, the direction in which the support 10 and the vibration part 20 are laminated is also referred to as the lamination direction D1. As shown in FIG. 1, the piezoelectric element 1 of this embodiment is formed in a rectangular shape when viewed in the direction along the lamination direction D1.

[0015] The support 10 has a rectangular shape when viewed in the direction along the stacking direction D1. The support 10 has a support substrate 11 that supports the vibrating part 20 and an insulating film 12 formed on the support substrate 11. The support 10 has a floating opening 100 formed therein to allow the inner edge of the vibrating part 20 to float. The support substrate 11 is made of, for example, a silicon substrate, and the insulating film 12 is made of, for example, an oxide film. The support substrate 11 and the insulating film 12 have a rectangular outer shape when viewed in the direction along the stacking direction D1 and are cylindrical with a through hole in the center.

[0016] The support substrate 11 has a substrate through-hole 110 formed in the stacking direction D1, and a support forming portion 111 that supports the vibrating portion 20 around the substrate through-hole 110. The insulating film 12 also has an insulating through-hole 120 formed in the stacking direction D1. The substrate through-hole 110 and the insulating through-hole 120 have the same shape when viewed in the direction along the stacking direction D1. In other words, the substrate through-hole 110 and the insulating through-hole 120 have the same shape in the cross-section perpendicular to the stacking direction D1. The floating opening 100 of the support 10 is formed by the substrate through-hole 110 and the insulating through-hole 120 being connected in the stacking direction D1. That is, the floating opening 100 is formed by penetrating the support substrate 11 and the insulating film 12 in the stacking direction D1.

[0017] As shown in Figures 1 and 5, the floating opening 100 has an uneven opening. That is, the substrate through-hole 110 and insulating through-hole 120 that constitute the floating opening 100 also have an uneven opening. The floating opening 100 is formed by alternating arrangements of a plurality of recesses 40 that are recessed toward the outer edge of the support 10 and a plurality of protrusions 50 that protrude in the opposite direction to the recesses 40. Details of the floating opening 100 will be described later. Note that in Figures 1 and 5, only representative parts of the plurality of recesses 40 and protrusions 50 are shown by reference numerals, and other reference numerals are omitted.

[0018] The vibrating section 20 constitutes a sensing section that vibrates in response to external pressure and is laminated on the support 10. The vibrating section 20 is arranged on the support 10 and has a support region 21 supported by the support 10 and a floating region 22 that is connected to the support region 21 and floats away from the support 10 on the floating opening 100. The entire floating region 22 has a shape corresponding to the floating opening 100. That is, the shape of the floating region 22 when viewed in the direction along the lamination direction D1 is the same as the shape of the substrate through-hole 110 and the insulating through-hole 120. The floating region 22 in this embodiment, which is formed by the floating opening 100 whose opening end is formed in an uneven shape, has an uneven outer edge shape.

[0019] As shown in Figure 1, a separation slit 23 is formed in the floating region 22, penetrating the floating region 22 in the stacking direction D1. In this embodiment, the separation slit 23 is formed to divide the floating region 22 into four sections. More specifically, two separation slits 23 are formed, passing through the center C of the floating region 22 and extending toward the opposing corners of the floating region 22. In other words, the separation slits 23 extend from each corner of the floating region 22, which is roughly rectangular in plan, toward the center C, and are formed so that the two separation slits 23 intersect at the center C.

[0020] As a result, the floating region 22 is separated into four vibration regions 220 which are roughly triangular in shape. Specifically, the floating region 22 is composed of four vibration regions 220 which are roughly isosceles triangular in shape in shape, each having two sides of equal length extending toward the center C of the floating region 22 and a base connected to those two sides.

[0021] Although not particularly limited, in this embodiment the width of the separation slit 23 is approximately 1 μm. Furthermore, the width of the separation slit 23 in the direction perpendicular to the direction of extension is constant from one end to the other. In addition, although the separation slit 23 in this embodiment is formed to terminate within the floating region 22, it may extend to the support region 21.

[0022] Each vibration region 220, which is roughly triangular in shape, is formed by dividing the floating region 22 as described above, so that the base side of the triangle is a fixed end supported by the support 10 (i.e., the support region 21). Each vibration region 220 is a cantilever with the vertex side opposite the base side being a free end. In other words, each vibration region 220 is connected to the support region 21 and is also cantilevered.

[0023] However, as described above, the floating opening 100 is formed by a plurality of recesses 40 and a plurality of protrusions 50. Therefore, vibration is limited in the floating region 22 on the outer edge side of the protrusions 50 by being supported by these protrusions 50. In other words, the portion of the floating region 22 that overlaps with the space formed by the recesses 40 in the stacking direction D1 is less susceptible to deformation by the protrusions 50. For this reason, the vibration region 220 in this embodiment is the region on the central side C of the floating region 22 from the portion supported by the protrusions 50. Also, the support region 21 is the region on the outer edge side of the portion supported by the protrusions 50 in the floating region 22.

[0024] In other words, the vibration region 220 is formed in the region of the floating region 22 excluding the portion that overlaps with the space formed by the recess 40 of the floating opening 100 in the stacking direction D1. The support region 21 is a region that includes the portion of the floating region 22 that overlaps with the support 10 in the stacking direction D1, and the portion that overlaps with the space formed by the recess 40 in the stacking direction D1, and is formed on the outer edge side of the support 10 from the four vibration regions 220. For this reason, the floating region 22 includes a part of the support region 21 and the vibration region 220. Hereinafter, the portion of the floating opening 100 that forms the vibration region 220 will be referred to as the vibration opening 10b, and the portion of the floating opening 100 that forms the support region 21 will be referred to as the support opening 10c. In Figures 1 and 5, the boundary between the vibration region 220 and the support region 21, with the bottom edge of the vibration region 220 shown as a dashed line.

[0025] In this embodiment, the support region 21 is formed in a rectangular shape when viewed along the stacking direction D1, and has a rectangular through-hole in the center when viewed along the stacking direction D1. Hereinafter, the boundary between each of the four vibration regions 220 and the support region 21 will be referred to as the support end 221, and the end opposite to the support end 221, i.e., the end on the central C side, will be referred to as the vibration end 222. The direction from the vibration end 222 toward the support end 221 will also be referred to as the support direction D2. The recess 40 of the floating opening 100 is formed by the inner edge of the support forming portion 111 being recessed toward the support direction D2. The convex portion 50 of the floating opening 100 is formed by the inner edge of the support forming portion 111 protruding from the recess 40 toward the opposite side of the support direction D2, forming the support end 221 for deformation of the vibration region 220. In this embodiment, the vibration region 220 has a cantilever beam shape in which the support end 221 is a fixed end and the vibration end 222 is a free end.

[0026] The vibrating section 20 has a configuration that includes a piezoelectric film 60 and an electrode film 70 connected to the piezoelectric film 60. Specifically, the piezoelectric film 60 has a lower piezoelectric film 61 and an upper piezoelectric film 62 laminated on the lower piezoelectric film 61. The electrode film 70 has a lower electrode film 71 positioned below the lower piezoelectric film 61, an intermediate electrode film 72 positioned between the lower piezoelectric film 61 and the upper piezoelectric film 62, and an upper electrode film 73 positioned on the upper piezoelectric film 62. In other words, the vibrating section 20 has a bimorph structure in which the lower piezoelectric film 61 is sandwiched between the lower electrode film 71 and the intermediate electrode film 72, and the upper piezoelectric film 62 is sandwiched between the intermediate electrode film 72 and the upper electrode film 73.

[0027] Furthermore, the vibrating section 20 of this embodiment has a base film 80 on which the lower piezoelectric film 61 and the lower electrode film 71 are arranged. In other words, the piezoelectric film 60 and the electrode film 70 are arranged on the support 10 via the base film 80. The base film 80 is not strictly necessary, but is provided to facilitate crystal growth when forming the lower piezoelectric film 61, etc. The base film 80 is made of AlN or the like.

[0028] The lower piezoelectric film 61 and the upper piezoelectric film 62 are made of ScAlN. The lower electrode film 71, the intermediate electrode film 72, the upper electrode film 73, etc., are made of molybdenum, copper, platinum, titanium, aluminum, etc. The piezoelectric film 60 has a thickness of about 1 μm, and the base film 80 has a thickness of about several tens of nanometers. In other words, the base film 80 is extremely thin compared to the piezoelectric film 60.

[0029] Furthermore, the lower electrode film 71, the intermediate electrode film 72, and the upper electrode film 73 are formed in each of the four vibration regions 220. Each of the lower electrode film 71, intermediate electrode film 72, and upper electrode film 73 formed in each of the four vibration regions 220 is formed in a shape corresponding to the vibration region 220, which is approximately triangular in plan. That is, the lower electrode film 71, the intermediate electrode film 72, and the upper electrode film 73 are formed in an approximately triangular shape in plan. Moreover, the triangular cross-sectional area of ​​the lower electrode film 71, the intermediate electrode film 72, and the upper electrode film 73 perpendicular to the stacking direction D1 is smaller than the triangular cross-sectional area of ​​the vibration region 220 perpendicular to the stacking direction D1. In addition, at least a portion of the lower electrode film 71, the intermediate electrode film 72, and the upper electrode film 73 overlap each other in the stacking direction D1. In this embodiment, the lower electrode film 71, the intermediate electrode film 72, and the upper electrode film 73 all overlap each other in the stacking direction D1, and their outer edges are formed with substantially the same shape.

[0030] Furthermore, in this embodiment, each vibration region 220 is defined as a first region R1 on the fixed end side and a second region R2 on the free end side. The lower electrode film 71, intermediate electrode film 72, and upper electrode film 73 are formed in the first region R1 and the second region R2, respectively. However, the lower electrode film 71, intermediate electrode film 72, and upper electrode film 73 formed in the first region R1 are separated from the lower electrode film 71, intermediate electrode film 72, and upper electrode film 73 formed in the second region R2, and are in an insulated state.

[0031] As shown in Figure 1, the upper electrode film 73 formed in the second region R2 is formed in a planar triangular shape. Although not shown, the lower electrode film 71 and the intermediate electrode film 72 formed in the second region R2 are also formed in a planar triangular shape, similar to the upper electrode film 73. Furthermore, the lower electrode film 71, the intermediate electrode film 72, and the upper electrode film 73 formed in the second region R2 are each formed to overlap each other in the stacking direction D1. In other words, the lower electrode film 71, the intermediate electrode film 72, and the upper electrode film 73 formed in the second region R2 have the same shape and are positioned to overlap in the stacking direction D1.

[0032] Furthermore, the upper electrode film 73 formed in the first region R1 is divided into multiple parts, as shown in Figure 1. Specifically, the upper electrode film 73 formed in the first region R1 is divided into three planar, substantially trapezoidal shapes with different shapes by two electrode slits 74. The electrode slits 74 are formed to penetrate the upper electrode film 73 in the stacking direction D1. The two electrode slits 74 are formed to extend toward the center C from two points that divide the base of the planar, substantially isosceles triangular upper electrode film 73 into three equal parts. The two electrode slits 74 formed in this way do not intersect each other. Hereinafter, the parts of the upper electrode film 73 formed in the first region R1 that are divided into three by the two electrode slits 74 will be referred to as the first base film 731, the second base film 732, and the third base film 733. The first base membrane 731, the second base membrane 732, and the third base membrane 733 are arranged in this order in the vibration region 220.

[0033] Although not shown in the figure, the lower electrode film 71 and the intermediate electrode film 72 formed in the first region R1 are similarly divided into three parts by two slits. The lower electrode film 71, the intermediate electrode film 72, and the upper electrode film 73 formed in the first region R1 are formed to overlap each other in the stacking direction D1. That is, the lower electrode film 71, the intermediate electrode film 72, and the upper electrode film 73 formed in the first region R1 have the same shape and are positioned to overlap in the stacking direction D1. In Figure 1, only representative parts of the multiple electrode slits 74, the first base film 731, the second base film 732, and the third base film 733 are shown by their symbols, and other symbols are omitted.

[0034] Furthermore, as shown in Figures 1 to 4, the lower electrode film 71, intermediate electrode film 72, and upper electrode film 73 formed in the first region R1 are partially extended from the vibration region 220 to the support region 21. The lower electrode film 71, intermediate electrode film 72, and upper electrode film 73 formed in the first region R1 are not extended from the vibration region 220 to the support region 21 in other parts, but their ends extend to the support end 221, which is the boundary between the vibration region 220 and the support region 21. The lower electrode film 71, intermediate electrode film 72, and upper electrode film 73 formed in this way are formed spanning from the support region 21 to the vibration region 220.

[0035] Hereinafter, the portion of the lower electrode film 71 formed on the support region 21 side will be referred to as the lower support side electrode film 71a, and the portion of the lower electrode film 71 formed on the vibration region 220 side will be referred to as the lower vibration side electrode film 71b. Similarly, the portion of the intermediate electrode film 72 formed on the support region 21 side will be referred to as the intermediate support side electrode film 72a, and the portion of the intermediate electrode film 72 formed on the vibration region 220 side will be referred to as the intermediate vibration side electrode film 72b. Furthermore, the portion of the upper electrode film 73 formed on the support region 21 side will be referred to as the upper support side electrode film 73a, and the portion of the upper electrode film 73 formed on the vibration region 220 side will be referred to as the upper vibration side electrode film 73b. However, the lower support side electrode film 71a, the intermediate support side electrode film 72a, and the upper support side electrode film 73a may be collectively referred to simply as the support side electrode film 70a. In addition, the lower vibration-side electrode film 71b, the intermediate vibration-side electrode film 72b, and the upper vibration-side electrode film 73b may be collectively referred to simply as the vibration-side electrode film 70b.

[0036] Details of the lower support electrode film 71a, the intermediate support electrode film 72a, and the upper support electrode film 73a will be described below. However, the lower support electrode film 71a, the intermediate support electrode film 72a, and the upper support electrode film 73a have the same basic structure and shape as each other. For this reason, in the following, only the upper support electrode film 73a will be described in detail, and detailed descriptions of the lower support electrode film 71a and the intermediate support electrode film 72a will be omitted.

[0037] The upper support side electrode film 73a is included in multiple parts of the upper electrode film 73 formed in the first region R1. Specifically, there are two upper support side electrode films 73a in each of the three parts divided by the two electrode slits 74: the first base film 731, the second base film 732, and the third base film 733. Each of these upper support side electrode films 73a is formed in a rectangular shape when viewed along the stacking direction D1, and extends from the base side of the triangular upper electrode film 73 in the support direction D2. That is, the upper support side electrode film 73a is formed to extend away from the vibration region 220.

[0038] The lower support side electrode film 71a and the intermediate support side electrode film 72a, like the upper support side electrode film 73a, are each included in two of the lower support side electrode film 71 and intermediate support side electrode film 72, which are divided into three first regions R1. The lower support side electrode film 71a and the intermediate support side electrode film 72a are each formed in a rectangular shape when viewed along the stacking direction D1, and extend in the support direction D2 from the bottom side of the triangular lower support side electrode film 71 and intermediate support side electrode film 72. The lower support side electrode film 71a, the intermediate support side electrode film 72a and the upper support side electrode film 73a overlap each other in the stacking direction D1.

[0039] Furthermore, the floating opening 100 in this embodiment has an uneven shape corresponding to the lower support side electrode film 71a, the intermediate support side electrode film 72a, and the upper support side electrode film 73a. Specifically, as shown in Figure 5, the recess 40 is formed by being recessed in the support direction D2 from the inner edge that forms the support region 21 in the support body 10. The convex portion 50 protrudes from the recess 40 on the opposite side of the support direction D2 and forms the inner edge that forms the support region 21. In other words, the recess 40 is formed in the support forming portion 111 because the support forming portion 111 that supports the support region 21 is formed by being recessed in the support direction D2. The recess 40 is formed in a rectangular shape when viewed in the direction along the stacking direction D1. The recess 40 has a first recess 41, a second recess 42, a third recess 43, and a fourth recess 44 on each of the four sides that form the rectangular shape, which will be described below.

[0040] As shown in Figure 1, the recess 40 includes a first recess 41 formed to be large enough to surround, in the stacking direction D1, the upper support electrode film 73a that is further away from the second base film 732, of the two upper support electrode films 73a extending from the first base film 731. The first recess 41 overlaps, in the stacking direction D1, at least a portion of the upper support electrode film 73a that is further away from the second base film 732, of the two upper support electrode films 73a extending from the first base film 731.

[0041] Furthermore, the recess 40 includes a second recess 42 formed to be large enough to surround, in the stacking direction D1, the upper support electrode film 73a closer to the second base film 732, out of the two upper support electrode films 73a extending from the first base film 731, and the upper support electrode film 73a closer to the first base film 731, out of the two upper support electrode films 73a extending from the second base film 732. The second recess 42 overlaps, in the stacking direction D1, at least a portion of each of the upper support electrode film 73a closer to the second base film 732, out of the two upper support electrode films 73a extending from the first base film 731, and the upper support electrode film 73a closer to the first base film 731, out of the two upper support electrode films 73a extending from the second base film 732.

[0042] Furthermore, the recess 40 includes a third recess 43 formed to be large enough to surround, in the stacking direction D1, the upper support electrode film 73a closer to the third base film 733 among the two upper support electrode films 73a extending from the second base film 732, and the upper support electrode film 73a closer to the second base film 732 among the two upper support electrode films 73a extending from the third base film 733. The third recess 43 overlaps, in the stacking direction D1, with at least a portion of each of the upper support electrode film 73a closer to the third base film 733 among the two upper support electrode films 73a extending from the third base film 732 and the upper support electrode film 73a closer to the second base film 732 among the two upper support electrode films 73a extending from the third base film 733.

[0043] Furthermore, the recess 40 includes a fourth recess 44 formed to be large enough to surround, in the stacking direction D1, the upper support electrode film 73a that is further away from the second base film 732, of the two upper support electrode films 73a extending from the third base film 733. The fourth recess 44 overlaps, in the stacking direction D1, at least a portion of the upper support electrode film 73a that is further away from the second base film 732, of the two upper support electrode films 73a extending from the third base film 733.

[0044] Here, when the area in the stacking direction D1 where the support-side electrode film 70a and the space formed by the recess 40 overlap is defined as the recess range, at least one of the support-side electrode films 70a that each of the lower electrode film 71, intermediate electrode film 72, and upper electrode film 73 has is included within the recess range. In this embodiment, the first recess 41, second recess 42, third recess 43, and fourth recess 44 are formed such that all six support-side electrode films 70a that each of the lower electrode film 71, intermediate electrode film 72, and upper electrode film 73 has are included within the recess range. In other words, each of the multiple support-side electrode films 70a overlaps with one of the spaces formed by the multiple recesses 40 of the support substrate 11 in the stacking direction D1. Furthermore, each of the multiple support-side electrode films 70a is configured not to overlap with the support substrate 11 and the insulating film 12 of the support 10 in the stacking direction D1.

[0045] Furthermore, protrusions 50 are formed between each of the first recess 41, second recess 42, third recess 43, and fourth recess 44. The floating opening 100 is formed by these multiple recesses 40 and multiple protrusions 50. In other words, the floating region 22 formed by the floating opening 100 is formed by the multiple recesses 40 and multiple protrusions 50 formed in this manner. In addition, the substrate through-holes 110 and insulating through-holes 120 that constitute the floating opening 100 are also formed by these multiple recesses 40 and multiple protrusions 50.

[0046] As described above, the floating region 22 includes a vibration region 220 and a support region 21. Specifically, the vibration region 220 is the region inside the boundary between the vibration region 220 and the support region 21, as shown by the dashed lines in Figures 1 and 5 of the floating region 22. In contrast, the support region 21 is the region that includes the portion outside the boundary between the vibration region 220 and the support region 21, as shown by the dashed lines in Figures 1 and 5 of the floating region 22. That is, the vibration region 220 is the region that overlaps with the space inside the convex portion 50 in the floating region 22 in the stacking direction D1. In contrast, the support region 21 is the region that overlaps with the space formed by the concave portion 40 formed on the support direction D2 side of the convex portion 50 in the floating region 22 in the stacking direction D1.

[0047] Therefore, the multiple recesses 40 and multiple protrusions 50 that form the floating region 22 form a vibration region 220 in the vibrating portion 20, and also form a part of the support region 21 on the support direction D2 side of the vibration region 220. This part of the support region 21 is the part that overlaps with the space formed by the multiple recesses 40 in the stacking direction D1. In this embodiment, the support-side electrode film 70a is positioned at a location that overlaps with any of the first recess 41, second recess 42, third recess 43, and fourth recess 44 in the stacking direction D1. In this embodiment, the part that forms the vibration region 220 in the floating opening 100 corresponds to the vibration opening 10b, and the vibration opening 10b is formed by the multiple protrusions 50. Also, the recesses 40 that form the support region 21 in the floating opening 100 correspond to the support opening 10c, and the support opening 10c is formed by the multiple recesses 40. The recesses 40 are in communication with the vibration opening 10b. Furthermore, the floating opening 100 of this embodiment includes a vibration opening 10b and a support opening 10c.

[0048] As shown in Figures 1 to 4, the support region 21 of the vibrating section 20 is provided with a connecting section 30 that connects the lower electrode film 71, the intermediate electrode film 72, and the upper electrode film 73. That is, the connecting section 30 is located on the support direction D2 side of the vibrating end 222 of the vibrating section 20. As shown in Figures 1 to 3 and 6, the connecting section 30 has a first electrode section 31 that electrically connects the lower electrode film 71 and the upper electrode film 73 formed in the first region R1, and a second electrode section 32 that is electrically connected to the intermediate electrode film 72 formed in the first region R1. Furthermore, the connecting section 30 has a connecting wiring section 33 that connects the first electrode section 31 and the second electrode section 32, and two circuit wiring sections 34 that are connected to an external circuit.

[0049] The first electrode portion 31 is positioned in a through-hole formed by penetrating the upper electrode film 73, the upper piezoelectric film 62, and the lower piezoelectric film 61. The first electrode portion 31 electrically connects the upper electrode film 73 and the lower electrode film 71. The second electrode portion 32 is positioned in a through-hole formed by penetrating the upper piezoelectric film 62. The second electrode portion 32 is electrically connected to the intermediate electrode film 72. The first electrode portion 31 and the second electrode portion 32 are formed in the support region 21 and are positioned to overlap in the stacking direction D1 with the space formed by the recess 40 in the support region 21.

[0050] The connecting wiring section 33 is formed in a thin plate shape and spans the first electrode section 31 and the second electrode section 32. Specifically, the connecting wiring section 33 has a first connecting wiring section 331 that connects the vibration regions 220, which are divided into four by the separation slit 23, in series, and a second connecting wiring section 332 that connects the upper electrode film 73, the upper piezoelectric film 62, and the lower piezoelectric film 61, which each have portions that are divided into three within each vibration region 220, in parallel.

[0051] The first connecting wiring section 331 extends from the first electrode section 31 to the second electrode section 32 in adjacent vibration regions 220. The first connecting wiring section 331 electrically connects the first base film 731 and the third base film 733 in different vibration regions 220. The first connecting wiring section 331 is formed in a U-shape when viewed along the stacking direction D1. The first connecting wiring section 331 is formed in the support region 21 and is formed so as not to straddle the vibration region 220. In addition, a portion of the first connecting wiring section 331 overlaps with a portion of the first recess 41 and a portion of the fourth recess 44 in the stacking direction D1. However, the first connecting wiring section 331 is formed to straddle a portion of the support region 21 that does not overlap with the recess 40 in the stacking direction D1.

[0052] The second connecting wiring section 332 extends from the first electrode section 31 to the second electrode section 32 of the lower electrode film 71, intermediate electrode film 72, and upper electrode film 73, which are divided by the first region R1 within each of the four vibration regions 220. The second connecting wiring section 332 connects the first base film 731 and the second base film 732, or the second base film 732 and the third base film 733. The second connecting wiring section 332 is formed in a rectangular shape when viewed along the stacking direction D1. The second connecting wiring section 332 is formed in the support region 21 and is formed so as not to straddle the vibration region 220. The entire second connecting wiring section 332 overlaps with either the second recess 42 or the third recess 43 in the stacking direction D1.

[0053] The two circuit wiring sections 34 are voltage output wiring sections for outputting changes in charge in the vibration region 220 as pressure detection signals to the outside. The two circuit wiring sections 34 are each connected to a pad section 35 which is connected to an external circuit. For this reason, unlike the first electrode section 31, the second electrode section 32, and the connecting wiring section 33, the two circuit wiring sections 34 are not for connecting the electrode film 70. Parts of each of the two circuit wiring sections 34 overlap with parts of the first recess 41 and the fourth recess 44, respectively, in the stacking direction D1.

[0054] The first electrode portion 31, the second electrode portion 32, the connecting wiring portion 33, and the circuit wiring portion 34 are constructed using ScAlN or the like, similar to the piezoelectric film 60. Alternatively, the first electrode portion 31, the second electrode portion 32, the connecting wiring portion 33, and the circuit wiring portion 34 may be constructed using molybdenum, copper, platinum, titanium, aluminum, or the like, similar to the electrode film 70. The lower electrode film 71, the intermediate electrode film 72, and the upper electrode film 73 formed in the second region R2 are not electrically connected to the first electrode portion 31 and the second electrode portion 32, and are in a floating state. For this reason, the lower electrode film 71, the intermediate electrode film 72, and the upper electrode film 73 formed in the second region R2 are not necessarily required, but in this embodiment, they are provided to protect the portions of the lower piezoelectric film 61 and the upper piezoelectric film 62 located in the second region R2.

[0055] The vibration unit 20 of this embodiment is configured to output the change in charge in the four vibration regions 220 as a single pressure detection signal. In other words, the four vibration regions 220 are electrically connected in series. More specifically, each of the four vibration regions 220 has a bimorph structure, with each lower electrode film 71, each intermediate electrode film 72, and each upper electrode film 73 formed in each vibration region 220 being connected in parallel, while the vibration regions 220 are connected in series with each other.

[0056] The above describes the configuration of the piezoelectric element 1 in this embodiment. When sound pressure is applied to each vibration region 220 of such a piezoelectric element 1, each vibration region 220 vibrates. In this case, for example, if the free end side of the vibration region 220 is displaced upward, tensile stress is generated in the lower piezoelectric film 61 and compressive stress is generated in the upper piezoelectric film 62. Therefore, sound pressure can be detected by extracting charge from the first electrode portion 31 and the second electrode portion 32 connected by the connecting wiring portion 33.

[0057] Incidentally, in a piezoelectric element 1 that extracts the stress generated in the piezoelectric film 60 as an electric charge from the electrode film 70, let's assume that a connection wiring section 33 for extracting the charge is placed on the electrode film 70 within the vibration region 220. In this case, the potential of the area on the electrode film 70 where the connection wiring section 33 is placed and the potential of the connection wiring section 33 are the same. That is, in the part of the electrode film 70 vibrating within the vibration region 220 where the connection wiring section 33 is formed, the potential is the same as that of the connection wiring section 33.

[0058] Therefore, when acquiring the potential of the piezoelectric film 60 when stress is generated via the electrode film 70 and the connecting wiring portion 33, the charge of the part of the piezoelectric film 60 connected to the part of the electrode film 70 where the connecting wiring portion 33 is formed cannot be utilized. In other words, of the stress generated in the piezoelectric film 60, the stress generated indirectly in the part connected to the part where the connecting wiring portion 33 is formed cannot be used for sound pressure detection, and the stress generated in that part becomes wasted stress. Consequently, if the connecting wiring portion 33 is formed in the part of the electrode film 70 that is located within the vibration region 220, the voltage detected when the piezoelectric film 60 vibrates will decrease compared to the case where the connecting wiring portion 33 is formed outside the vibration region 220. As a result, in the configuration in which the connecting wiring portion 33 for extracting charge is placed on the electrode film 70 within the vibration region 220, there is a risk that the detection sensitivity when the piezoelectric element 1 detects sound waves will decrease compared to the configuration in which the connecting wiring portion 33 is placed on the electrode film 70 outside the vibration region 220.

[0059] In contrast, in the piezoelectric element 1 of this embodiment, the electrode film 70 is formed spanning from the vibration region 220 to the support region 21, and has a support-side electrode film 70a formed in the support region 21. The connecting wiring section 33 is connected to the support-side electrode film 70a located within the support region 21, which is outside the vibration region 220. Specifically, the first connecting wiring section 331, which connects the four vibration regions 220 in series, is formed in the support region 21 and connects the support-side electrode films 70a of different vibration regions 220 without crossing the vibration regions 220. Furthermore, the second connecting wiring section 332, which connects the lower electrode film 71, intermediate electrode film 72, and upper electrode film 73, which are divided within the four vibration regions 220, in parallel, is formed in the support region 21 and connects the support-side electrode films 70a within one vibration region 220 without crossing the vibration regions 220.

[0060] According to this, when acquiring the potential of the piezoelectric film 60 when the piezoelectric film 60 vibrates via the electrode film 70 and the connecting wiring portion 33, it is possible to avoid the inability to utilize the charge in the area of ​​the electrode film 70 where the first connecting wiring portion 331 and the second connecting wiring portion 332 are formed. Therefore, it is possible to suppress the decrease in voltage detected when the piezoelectric film 60 vibrates. As a result, compared to a configuration in which the first connecting wiring portion 331 and the second connecting wiring portion 332 are placed on the electrode film 70 within the vibration region 220, the detection sensitivity when the piezoelectric element 1 detects sound waves can be improved.

[0061] However, in order to form the connection wiring section 33 for extracting charge in the support region 21, when forming the electrode film 70 spanning from the vibration region 220 to the support region 21, let's assume that the support substrate 11 is located at a position that overlaps with the electrode film 70 in the stacking direction D1 within the support region 21. In this case, there is a risk that parasitic capacitance will occur between the electrode film 70 and the support substrate 11. If parasitic capacitance occurs between the electrode film 70 and the support substrate 11 and the potential of the piezoelectric film 60 decreases when the piezoelectric film 60 vibrates, there is a risk that the detection sensitivity of the piezoelectric element 1 when detecting sound waves will decrease.

[0062] In contrast, in the piezoelectric element 1 of this embodiment, the first recess 41, second recess 42, third recess 43, and fourth recess 44 are formed such that all six support-side electrode films 70a, each of the lower electrode film 71, intermediate electrode film 72, and upper electrode film 73, are included within the recess range. That is, each of the multiple support-side electrode films 70a overlaps with one of the spaces formed by the multiple recesses 40 of the support substrate 11 in the stacking direction D1, but does not overlap with the support substrate 11 in the stacking direction D1.

[0063] Therefore, it is possible to avoid the generation of parasitic capacitance between the electrode film 70 and the support substrate 11. Furthermore, it is possible to avoid the potential of the piezoelectric film 60 decreasing due to the generation of parasitic capacitance. As a result, compared to a configuration in which the support substrate 11 is located at a position overlapping with the electrode film 70 in the stacking direction D1, the detection sensitivity when the piezoelectric element 1 detects sound waves can be improved.

[0064] Furthermore, according to the above embodiment, the following effects can be obtained.

[0065] (1) In the above embodiment, the support substrate 11 has a floating opening 100 that forms a floating region 22. The floating opening 100 is formed in an uneven shape with a plurality of recesses 40 formed in the direction of support D2 at its opening end, and a plurality of protrusions 50 that project from the plurality of recesses 40 toward the opposite side of the support direction D2. The vibration opening 10b is formed by the plurality of protrusions 50. The support opening 10c in the support region 21 that does not overlap with the support side electrode film 70a in the stacking direction D1 is formed by a plurality of recesses 40.

[0066] By making the floating opening 100 have an uneven shape, the support end 221 of the vibration region 220 becomes a part that is supported by the protrusion 50. In other words, the fixed end when the vibrating part 20 vibrates is supported by the protrusion 50. When the vibrating part 20 vibrates, the stress generated in the piezoelectric film 60 provided in the vibration region 220 is greater at the support end 221, which is the fixed end, than at the vibrating end 222, which is the free end.

[0067] Furthermore, in the piezoelectric element 1 that detects stress generated in the piezoelectric film 60, the greater the stress generated in the piezoelectric film 60, the greater the voltage detected when the piezoelectric film 60 vibrates. For this reason, in order to improve the detection sensitivity of the piezoelectric element 1 of this embodiment, which is configured in a cantilever shape, it is desirable to have a structure in which the stress at the fixed end becomes greater than the stress generated at the free end when stress is generated in the piezoelectric film 60 due to vibration.

[0068] Furthermore, when providing the connection wiring section 33 for extracting charge on the electrode film 70, it is desirable to place the connection wiring section 33 in a location on the electrode film 70 that overlaps with a location where stress is less likely to occur rather than a location where stress is more likely to occur in the piezoelectric film 60. When the connection wiring section 33 is provided on the electrode film 70, as described above, the charge in the area where the connection wiring section 33 is formed cannot be utilized, so even if the connection wiring section 33 is provided in a location where stress is more likely to occur, it is not possible to extract charge from the piezoelectric element 1. In other words, the stress in the piezoelectric film 60 at the location connected to the electrode film 70 on which the connection wiring section 33 is provided is wasted.

[0069] Here, the difference in stress between the case where the opening end of the floating opening 100 has an uneven shape and the case where it does not have an uneven shape will be explained with reference to Figures 7 and 8. The contour plot shown in Figure 7 shows the simulation results of the stress generated in the vibration region 220 when a predetermined sound pressure is applied to a piezoelectric element 1 whose opening end of the floating opening 100 does not have an uneven shape. The contour plot shown in Figure 8 shows the simulation results of the stress generated in the vibration region 220 when a predetermined sound pressure is applied to a piezoelectric element 1 whose opening end of the floating opening 100 has an uneven shape, similar to the piezoelectric element 1 of this embodiment.

[0070] As shown in Figure 7, when the opening end of the floating opening 100 is not uneven, the stress generated in the vibration region 220 is greatest near the center of the support end 221, and the stress gradually decreases as you move away from the center of the support end 221. Also, the stress generated in the vibration region 220 is smaller at the free end, the vibrating end 222, compared to the stress generated at the fixed end, the support end 221.

[0071] Furthermore, as shown in Figure 8, when the opening end of the floating opening 100 has an uneven shape, the stress generated in the vibration region 220 is greatest near the center of the support end 221, specifically in the area where it overlaps with the protrusion 50 in the stacking direction D1. As you move away from the center of the support end 221, the stress generated in the vibration region 220 gradually decreases. However, when the opening end of the floating opening 100 has an uneven shape, the stress generated in the support end 221 is smaller near the area where the recess 40 of the support end 221 overlaps with the stacking direction D1 compared to when the opening end of the floating opening 100 does not have an uneven shape. This is because, by forming the recess 40 as a depression in the support direction D2, the vibration region 220 cannot be supported in the area where the recess 40 of the support end 221 overlaps with the stacking direction D1, making it difficult for stress to be generated in that area.

[0072] As the stress generated near the overlapping portion of the support end 221 with the recess 40 in the stacking direction D1 decreases, this reduced stress is applied to the support end 221 that overlaps with the protrusions 50 at both ends of the recess 40 in the stacking direction D1. Therefore, when the opening end of the floating opening 100 has an uneven shape, the stress generated at the support end 221 near the protrusions 50 is greater than when the opening end of the floating opening 100 does not have an uneven shape. Furthermore, the stress generated at the portion of the support end 221 that overlaps with the protrusions 50 in the stacking direction D1, where the connecting wiring portion 33 is not placed, can be increased. As a result, when sound pressure is applied to the vibration region 220, the voltage based on the stress generated in the vibration region 220 can be increased, and the detection sensitivity of the piezoelectric element 1 can be improved.

[0073] Furthermore, by making the opening end of the floating opening 100 uneven, the stress generated in the area where the connecting wiring section 33 is located, which is an area where the charge of the piezoelectric film 60 cannot be utilized, can be reduced. This makes it easier to avoid wasting the stress of the piezoelectric film 60 in the area where the charge of the piezoelectric film 60 cannot be utilized.

[0074] (2) In the above embodiment, all of the support side electrode films 70a, of which the lower electrode film 71, the intermediate electrode film 72, and the upper electrode film 73 each have six, are included within the recessed area.

[0075] According to this configuration, compared to a configuration in which not all of the support electrode film 70a is included within the recessed area, it is possible to avoid the generation of parasitic capacitance between all of the support electrode film 70a and the support substrate 11, and therefore, the detection sensitivity of the piezoelectric element 1 can be further improved.

[0076] (Second Embodiment) Next, the second embodiment will be described with reference to Figures 9 to 11. In this embodiment, the shape of the support electrode film 70a and the shape of the recess 40 differ from those of the first embodiment. Other than this, it is the same as the first embodiment. For this reason, in this embodiment, the parts that differ from the first embodiment will be mainly described, and the parts that are the same as the first embodiment may be omitted from the description.

[0077] As shown in Figure 9, the support-side electrode film 70a of this embodiment has a connection installation section 75 on which the first electrode section 31, the second electrode section 32, and the connection wiring section 33 are installed, and a connection connecting section 76 that connects the connection installation section 75 to the vibration-side electrode film 70b. The connection installation section 75 and the connection connecting section 76 are arranged in this order along the support direction D2. For this reason, the connection connecting section 76 is formed on the opposite side of the support direction D2 from the connection installation section 75.

[0078] Furthermore, the width direction D3 of the connection and coupling portion 76, specifically the direction perpendicular to the stacking direction D1 and the support direction D2, is smaller than the width direction D3 of the connection and installation portion 75. As a result, the width direction D3 of the support-side electrode film 70a is larger along the support direction D2. That is, the width direction D3 of the support-side electrode film 70a on the side connected to the vibration region 220 is smaller than the width direction D3 of the side where the connection wiring portion 33 is installed. In this embodiment, the width direction D3 of the support-side electrode film 70a is gradually increased along the support direction D2. And, in this embodiment, the width direction D3 of the connection and coupling portion 76 of the support-side electrode film 70a is smaller than the width direction D3 of the portion corresponding to the connection and coupling portion 76 in the support-side electrode film 70a of the first embodiment.

[0079] Furthermore, the dimensions in the width direction D3 of the support electrode film 70a may increase in two or more steps along the support direction D2. Alternatively, the dimensions in the width direction D3 of the support electrode film 70a may increase continuously and gradually along the support direction D2.

[0080] Furthermore, as shown in Figure 9, the recess 40 of this embodiment has an installation recess 40a that overlaps with the connection installation portion 75 in the stacking direction D1, and a communication recess 40b that connects the vibration opening 10b and the installation recess 40a. The communication recess 40b and the installation recess 40a are arranged in this order along the support direction D2. For this reason, the communication recess 40b is formed on the opposite side from the support direction D2 from the installation recess 40a.

[0081] Furthermore, the width direction D3 of the communication recess 40b is smaller than the width direction D3 of the installation recess 40a, specifically in the direction perpendicular to the stacking direction D1 and the support direction D2. As a result, the width direction D3 of the recess 40 increases along the support direction D2. That is, the width direction D3 of the recess 40 is smaller than the width direction D3 of the opening portion of the recess 40 that communicates with the vibration opening 10b. In this embodiment, the width direction D3 of the recess 40 is smaller than the width direction D3 of the opening portion on the support direction D2 side of the opening portion that communicates with the vibration opening 10b. In this embodiment, the width direction D3 of the recess 40 increases in stages along the support direction D2. And, in this embodiment, the width direction D3 of the communication recess 40b is smaller than the width direction D3 of the portion corresponding to the communication recess 40b in the recess 40 of the first embodiment.

[0082] Furthermore, the dimension of the communication recess 40b in the width direction D3 is smaller than the dimension of the connecting portion 76 in the width direction D3. The connecting portion 76 overlaps with the communication recess 40b in the stacking direction D1. In other words, the portion in which the connecting portion 76 is formed is contained within the communication recess 40b in the stacking direction D1.

[0083] Furthermore, the dimensions of the recess 40 in the width direction D3 may increase in two or more steps along the support direction D2. Alternatively, the dimensions of the recess 40 in the width direction D3 may increase continuously and gradually along the support direction D2.

[0084] Furthermore, the floating opening 100 having the recesses 40 formed in this manner has a larger proportion of recesses 40 compared to the floating opening 100 in the first embodiment. Also, the floating opening 100 has its opening end formed with alternating communication recesses 40b and protrusions 50. In this embodiment, the proportion of the area where communication recesses 40b are formed at the opening end of the floating opening 100 is smaller than the proportion of the area where protrusions 50 are formed at the opening end. The reason why the proportion of the area where protrusions 50 are formed is smaller than the proportion of the area where communication recesses 40b are formed will be explained with reference to Figures 10 and 11.

[0085] Figure 10 shows the effect on the detection sensitivity of the piezoelectric element 1 caused by changing the convexity ratio, which is the range in which the convex portion 50 is formed within the entire range of the inner edge of the support substrate 11 that forms the floating opening 100. Specifically, Figure 10 shows the effect on the detection sensitivity of the piezoelectric element 1 caused by changing the widthwise D3 dimensions of the convex portion 50 and the recessed portion 40, while keeping the number of convex portions 50 and recessed portions 40 constant. The shape with a convexity ratio of 100% shown in Figure 10 is a shape in which the entire range of the inner edge of the support substrate 11 is formed by convex portions 50, and no recessed portions 40 are formed, with the inner edge of the support substrate 11 being occupied by convex portions 50. Then, by decreasing the widthwise D3 dimension of the convex portion 50 and increasing the widthwise D3 dimension of the recessed portion 40, the proportion of the range in which the recessed portion 40 is formed increases, and the proportion of the range in which the convex portion 50 is formed decreases, resulting in a convexity ratio less than 100%. In other words, the larger the proportion of the area where the recess 40 is formed, the smaller the proportion of the area where the convex portion 50 is formed, resulting in a smaller convex ratio.

[0086] For example, as shown in Figure 11, by making the widthwise dimension D3 of the recess 40 larger than the widthwise dimension D3 of the recess 40 in this embodiment, the smaller the ratio of the protrusions, the greater the influence on the detection sensitivity of the piezoelectric element 1, and the lower the detection sensitivity detected by the piezoelectric element 1. In other words, by increasing the widthwise dimension D3 of the recess 40 and decreasing the widthwise dimension D3 of the protrusion 50, the larger the proportion of the area where the recess 40 is formed and the smaller the proportion of the area where the protrusion 50 is formed, the lower the detection sensitivity detected by the piezoelectric element 1.

[0087] The reason for this decrease in detection sensitivity will now be explained. As mentioned above, when the floating opening 100 has an uneven shape, the portion of the floating opening 100 that overlaps with the recess 40 formed in the support direction D2 in the stacking direction D1 cannot support the vibration region 220. Therefore, when sound pressure is applied to the vibrating part 20, stress is unlikely to be generated in the portion that overlaps with the recess 40 in the stacking direction D1. In contrast, the convex portion 50 supports the support end 221 of the vibration region 220. Therefore, when sound pressure is applied to the vibrating part 20, stress tends to concentrate in the portion that overlaps with the convex portion 50 in the stacking direction D1.

[0088] Therefore, if the number of protrusions 50 and recesses 40 forming the floating opening 100 is constant, reducing the widthwise dimension D3 of the protrusions 50 and increasing the widthwise dimension D3 of the recesses 40 reduces the stress generated at the support end 221. In other words, the larger the proportion of the area formed by the recesses 40 and the smaller the proportion of the area formed by the protrusions 50, the smaller the stress generated at the support end 221. Therefore, the larger the proportion of the area formed by the recesses 40 and the smaller the proportion of the area formed by the protrusions 50, the lower the voltage detected when the piezoelectric film 60 vibrates, and the lower the detection sensitivity of the piezoelectric element 1.

[0089] Therefore, in order to suppress a decrease in the detection sensitivity of the piezoelectric element 1, it is desirable to increase the proportion of the area formed by the protrusion 50 while reducing the proportion of the area formed by the recess 40. Furthermore, it is desirable to increase the width dimension D3 of the protrusion 50 as much as possible. For this reason, the floating opening 100 of this embodiment suppresses a decrease in the detection sensitivity of the piezoelectric element 1 by making the proportion of the area in which the protrusion 50 is formed at the opening end larger than the proportion of the area in which the communication recess 40b is formed at the opening end.

[0090] However, if the width dimension D3 of the protrusion 50 is increased and the width dimension D3 of the recess 40 is decreased, the formation range for forming the first electrode portion 31, the second electrode portion 32, and the connecting wiring portion 33 so that they overlap with the recess 40 in the stacking direction D1 will be limited. In other words, if the width dimension D3 of the recess 40 is reduced in order to improve the detection sensitivity of the piezoelectric element 1, there is a risk that the first electrode portion 31, the second electrode portion 32, and the connecting wiring portion 33 will not be able to be formed in a position that overlaps with the recess 40 in the stacking direction D1. For example, suppose that the first electrode portion 31, the second electrode portion 32, and the connecting wiring portion 33 in this embodiment are made of ScAlN, which is a difficult-to-etch material. In this case, it is difficult to form these first electrode portion 31, second electrode portion 32, and connecting wiring portion 33 within the recess 40, which has a limited width dimension D3.

[0091] In contrast, the recess 40 of this embodiment has an installation recess 40a and a communication recess 40b, and the width D3 dimension of the communication recess 40b is smaller than the width D3 dimension of the installation recess 40a. Even if the width D3 dimension of the communication recess 40b is reduced to increase the range formed by the protrusion 50 at the opening end in order to suppress a decrease in the detection sensitivity of the piezoelectric element 1, it is possible to avoid limiting the size of the first electrode portion 31, the second electrode portion 32 and the connecting wiring portion 33 that can be formed.

[0092] (Third embodiment) Next, a third embodiment will be described with reference to Figure 12. This embodiment differs from the first embodiment in that a piezoelectric film slit 90 is formed in the vibrating part 20. Other than this, it is the same as the first embodiment. Therefore, in this embodiment, the parts that differ from the first embodiment will be mainly described, and the parts that are the same as the first embodiment may be omitted from the description.

[0093] As shown in Figure 12, the piezoelectric film 60 is formed spanning from the support region 21 to the vibration region 220 and includes a support-side piezoelectric film 63 formed at a position overlapping with the recess 40 in the stacking direction D1. The support-side electrode film 70a is connected to the support-side piezoelectric film 63.

[0094] A piezoelectric film slit 90 is formed in the support-side piezoelectric film 63 at a position that does not overlap with the support-side electrode film 70a in the stacking direction D1. The piezoelectric film slit 90 is formed to penetrate the piezoelectric film 60 in the stacking direction D1. Specifically, the piezoelectric film slit 90 penetrates the lower piezoelectric film 61 and the upper piezoelectric film 62. As a result, the piezoelectric film slit 90 communicates with the support opening 10c. That is, the piezoelectric film slit 90 communicates with the space formed by the recess 40. For example, two piezoelectric film slits 90 are formed extending along the support direction D2, at a position that overlaps with the third recess 43. Furthermore, of the two piezoelectric film slits 90 formed at a position that overlaps with the third recess 43, one is formed on one side of the width direction D3 of the support-side electrode film 70a included in the second base film 732, and the other is formed on the other side of the width direction D3 of the support-side electrode film 70a included in the third base film 733.

[0095] Although not shown in the figures, piezoelectric film slits 90 are also formed at positions that overlap with the first recess 41, the second recess 42, and the fourth recess 44 in the stacking direction D1. Two piezoelectric film slits 90 formed at the position overlapping with the first recess 41 are formed along the support direction D2 on one side and the other side of the width direction D3 of the support side electrode film 70a included in the first base film 731. Two piezoelectric film slits 90 formed at the position overlapping with the second recess 42 are formed such that one is formed along the support direction D2 on one side of the width direction D3 of the support side electrode film 70a included in the first base film 731, and the other is formed along the support direction D2 on the other side of the width direction D3 of the support side electrode film 70a included in the second base film 732. Two piezoelectric film slits 90 formed at the position overlapping with the fourth recess 44 are formed along the support direction D2 on one side and the other side of the width direction D3 of the support side electrode film 70a included in the third base film 733.

[0096] The configuration of the piezoelectric film slit 90 is not limited to these. For example, the piezoelectric film slit 90 formed in a position overlapping with the third recess 43 may also be formed between the support-side electrode film 70a included in the second base film 732 and the support-side electrode film 70a included in the third base film 733. Alternatively, the piezoelectric film slit 90 formed in a position overlapping with the third recess 43 may be formed only between the support-side electrode film 70a included in the second base film 732 and the support-side electrode film 70a included in the third base film 733. Alternatively, the piezoelectric film slit 90 formed in a position overlapping with the third recess 43 may be formed only on one side of the width direction D3 of the support-side electrode film 70a included in the second base film 732, or only on the other side of the width direction D3 of the support-side electrode film 70a included in the third base film 733.

[0097] By forming the piezoelectric film slit 90 in this manner, the stress transmitted from the piezoelectric film 60 to the support-side piezoelectric film 63 can be suppressed. Therefore, the stress generated in the area where the connecting wiring section 33 is located, which is a part where the charge of the piezoelectric film 60 cannot be utilized, can be reduced. This makes it easier to avoid wasting the stress of the piezoelectric film 60 in the area where the charge of the piezoelectric film 60 cannot be utilized.

[0098] Although this embodiment is a modification based on the first embodiment, it is also possible to combine this embodiment with either the first or second embodiment described above.

[0099] (Other embodiments) While representative embodiments of this disclosure have been described above, this disclosure is not limited to the embodiments described above and can be modified in various ways, for example, as follows.

[0100] In the above-described embodiment, an example was described in which the vibrating unit 20 has a lower piezoelectric film 61, an upper piezoelectric film 62, a lower electrode film 71, an intermediate electrode film 72, and an upper electrode film 73, but it is not limited to this. The vibrating unit 20 only needs to have a configuration that has at least one piezoelectric film 60 and one electrode film 70.

[0101] In the above-described embodiment, an example was given in which the piezoelectric element 1 is formed in a rectangular shape when viewed in a direction perpendicular to the stacking direction D1, but the invention is not limited to this. For example, the piezoelectric element 1 may have a polygonal shape such as a pentagon or a hexagon when viewed in a direction perpendicular to the stacking direction D1.

[0102] In the above-described embodiment, an example was given in which the vibrating section 20 is divided into four vibrating regions 220 by the separation slit 23, but the invention is not limited to this. For example, the vibrating section 20 may be divided into three or fewer vibrating regions 220 by the separation slit 23, or it may be divided into five or more vibrating regions 220.

[0103] In the above-described embodiment, an example was described in which the first connecting wiring portion 331 is formed in a U-shape, with a portion overlapping the recess 40 in the stacking direction D1 and the other portion not overlapping the recess 40 in the stacking direction D1. However, the invention is not limited to this example.

[0104] For example, as shown in Figure 13, the first connecting wiring section 331 may be formed in an L-shape, with the entire section overlapping the recess 40. In this case, as shown in Figure 13, the first recess 41 and the fourth recess 44 may be in communication and form an L-shape.

[0105] In the above-described embodiment, an example was given in which the opening end of the floating opening 100 is formed in an uneven shape, and the opening ends of the substrate through-hole 110 and the insulating through-hole 120 are also formed in an uneven shape, but the invention is not limited to this.

[0106] For example, as shown in Figure 14, the floating opening 100 may have a rectangular opening, and the openings of the substrate through-hole 110 and the insulating through-hole 120 may also be rectangular. In this case, the floating opening 100 corresponds to the vibration opening 10b that forms the vibration region 220. Also, when the floating opening 100 is formed in a rectangular shape and the vibration region 220 is formed by the floating opening 100, as shown in Figure 14, a support opening 10c different from the floating opening 100 is formed in the support forming portion 111 on the support direction side of the floating opening 100, penetrating the support 10 in the stacking direction D1. In this configuration, the vibration opening 10b and the support opening 10c are not in communication with each other. In this case, at least a portion of the support-side electrode film 70a and the connecting wiring portion 33 are provided at a position that overlaps with the support opening 10c in the stacking direction D1.

[0107] In the embodiments described above, it goes without saying that the elements constituting the embodiments are not necessarily essential, except in cases where they are explicitly stated to be essential or where they are clearly considered essential in principle.

[0108] In the embodiments described above, if numerical values ​​such as the number, numerical values, quantities, or ranges of the components of the embodiment are mentioned, the embodiment is not limited to those specific numbers unless explicitly stated as particularly essential or clearly limited to a specific number in principle.

[0109] In the embodiments described above, when referring to the shape, positional relationships, etc. of the components, the definition is not limited to those shapes, positional relationships, etc., unless otherwise specifically stated or when the definition is fundamentally limited to a particular shape, positional relationship, etc. [Explanation of Symbols]

[0110] 10b Vibration opening 10c support opening 20 Vibration section 21 Support area 22. Floating Area 33 Connection wiring section 220 Vibration area 221 Support end 222 Vibration end

Claims

1. Piezoelectric element, Support (10) and A vibrating part (20) is stacked on the support along a predetermined stacking direction and vibrates when pressure is applied from the outside, It comprises a connecting part (30) connected to the vibrating part, The vibrating part includes a piezoelectric film (60) that deforms due to the pressure, and a plurality of electrode films (70) connected to the piezoelectric film that extract the charge generated by the deformation of the piezoelectric film, and also has a support region (21) supported by the support, and a floating region (22) connected to the support region and floating away from the support. The floating region includes a plurality of vibrating regions (220), Each of the multiple vibration regions has a fixed end (221) that forms the boundary with the support region, and a free end (222) on the opposite side of the support end. Each of the plurality of electrode films is formed spanning from the support region to any of the plurality of vibration regions, and includes a support-side electrode film (70a) formed on the support region side and a vibration-side electrode film (70b) formed on the vibration region side. The connection portion is positioned on the side of the support direction from the support end in the vibrating portion, when the direction from the vibrating end toward the support end is defined as the support direction, and has a connection wiring portion (33) that electrically connects the support-side electrode films of each of the plurality of electrode films. The support has a support substrate (11) that supports the vibrating part, The support substrate has vibration openings (10b) that form the plurality of vibration regions, and a support forming portion (111) provided on the support direction side of the vibration openings to support the support regions, and a support opening (10c) is formed in the support forming portion. A piezoelectric element wherein at least a portion of the support electrode film is provided at a position that overlaps with the support opening in the stacking direction.

2. The support substrate forms the floating region and has a floating opening (100) that includes the vibration opening and the support opening. The floating opening has an uneven shape, with a plurality of recesses (40) formed by the opening end being recessed toward the support direction, and a plurality of protrusions (50) that project from the plurality of recesses toward the opposite side of the support direction. The vibration opening is formed by a plurality of the aforementioned protrusions, The piezoelectric element according to claim 1, wherein the support opening is formed by a plurality of recesses, and the space formed by the plurality of recesses communicates with the vibration opening.

3. The multiple recesses are formed at positions that overlap with the support side electrode film of each of the multiple electrode films in the stacking direction. When the area in which the support electrode film and the recess overlap in the aforementioned stacking direction is defined as the recess area, The piezoelectric element according to claim 2, wherein at least one of the plurality of support-side electrode films is included within the recessed area.

4. The piezoelectric element according to claim 3, wherein each of the plurality of support-side electrode films is included within the recessed area.

5. The support-side electrode film has a connection installation portion (75) on which the connection wiring portion is installed, and a connection connecting portion (76) formed on the opposite side from the support direction from the connection installation portion, which connects the connection installation portion and the vibration-side electrode film. The recess has, in the stacking direction, an installation recess (40a) that overlaps with the connection installation portion, and a communication recess (40b) located on the opposite side from the support direction from the installation recess, which connects the vibration opening and the installation recess. The piezoelectric element according to claim 3, wherein the dimension of the communication recess in the width direction intersecting the stacking direction and the support direction is smaller than the dimension of the installation recess in the width direction.

6. The piezoelectric element according to claim 5, wherein the floating opening has an opening end formed with the communication recess and the protrusion arranged alternately, and the proportion of the area where the communication recess is formed at the opening end is smaller than the proportion of the area where the protrusion is formed at the opening end.

7. The piezoelectric film is formed spanning from the support region to the vibration region, and includes a support-side piezoelectric film (63) that is formed at a position overlapping with the support opening in the stacking direction and connected to the support-side electrode film. The piezoelectric element according to claim 1, wherein a piezoelectric film slit (90) is formed in the support side piezoelectric film at a position that does not overlap with the support side electrode film in the stacking direction.

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