Piezoelectric element and microphone

Abstract

To provide a piezoelectric element capable of suppressing deformation of a vibration part without using a stress relaxation layer.SOLUTION: A piezoelectric element includes a support body 10, a vibration part 20 laminated on the support body along a predetermined lamination direction and vibrated by pressure applied from the outside, and a deformation suppression part 90 arranged separately from the vibration part and suppressing deformation of the support body. The vibration part has a support area 21a supported by the support body and a floating area 21b connected to the support area and floating from the support body. The support faces the floating region and has an opening 111 opened to the floating region. The deformation suppressing portion is disposed across the opening.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to piezoelectric elements and microphones. [Background technology]

[0002] Conventionally, a MEMS resonator has been known that includes a wafer substrate, a stress relaxation layer laminated on the wafer substrate, a nitride film laminated on the stress relaxation layer, and a MEMS structure provided on the surface of the nitride film (see, for example, Patent Document 1). The MEMS structure has a lower electrode and an upper electrode, with a gap formed between the lower electrode and the upper electrode. As a result, the MEMS structure has a cantilevered movable electrode structure in which the upper electrode is spaced apart from the lower electrode, allowing the upper electrode to vibrate.

[0003] In such a cantilevered movable electrode structure, when the upper electrode bends in a direction intersecting the vibration direction due to thermal expansion or the like, the second moment of area of ​​the upper electrode increases. This increase in the second moment of area becomes a factor that hinders the vibration of the upper electrode and reduces the vibration characteristics of the MEMS resonator.

[0004] In contrast, in the MEMS resonator described in Patent Document 1, the stress relaxation layer and the MEMS structure are made of the same material, but are made of a different material from the nitride film. This MEMS resonator has a sandwich structure in which the nitride film is sandwiched between the MEMS structure and the stress relaxation layer, which have thermal stresses in the same direction, and is configured to relieve thermal stress from the nitride film to the MEMS structure, which is caused by differences in thermal expansion coefficients. This MEMS resonator also has a stress relaxation layer below the nitride film, which relieves internal stress transmitted from the lower layer to the MEMS structure via the nitride film, thereby suppressing deformation of the upper electrode. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-123801 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the method of alleviating stress transmitted to a MEMS structure using a stress relaxation layer as described in Patent Document 1, the greater the stress transmitted to the MEMS structure, the thicker the stress relaxation layer must be. However, increasing the thickness of the stress relaxation layer increases the stress caused by curing and shrinkage of the electrodes, making it difficult for the electrodes to vibrate. For this reason, the method of alleviating stress using a stress relaxation layer in a piezoelectric element having a vibrating part that vibrates in response to external pressure, such as the MEMS vibrator described in Patent Document 1, has limited effectiveness. Therefore, there is a risk that the stress relaxation layer will not be able to suppress deformation of the vibrating part.

[0007] In view of the above, an object of the present disclosure is to provide a piezoelectric element that can suppress deformation of a vibrating portion without using a stress relaxation layer, and a microphone including the piezoelectric element. [Means for solving the problem]

[0008] According to one aspect of the present disclosure, The piezoelectric element is A support (10); a vibration section (20) that is stacked on the support body along a predetermined stacking direction and vibrates when pressure is applied from the outside; a deformation suppression section (90, 90a, 90b, 91, 92) that is arranged apart from the vibration section and suppresses deformation of the support, The vibration section has a support region (21a) supported by the support body and a floating region (21b) connected to the support region and floating above the support body, The support has an opening (111) facing the floating region and opening to the floating region; The deformation suppression portion is disposed across the opening.

[0009] Also, from another point of view, The piezoelectric element according to claim 1; a casing (100) having a substrate (101) on which a piezoelectric element is mounted and a cover (102) fixed to the substrate in a state in which the piezoelectric element is housed, and having a through-hole (101b) formed therein that communicates with the outside and through which sound pressure is introduced; The support is disposed on the substrate; The through-hole is formed to penetrate in the stacking direction and communicate with the opening, The deformation suppression portion is disposed opposite to and spaced apart from the substrate in the stacking direction, and is disposed at a position not overlapping with the through hole in the stacking direction.

[0010] According to this, the rigidity of the support can be increased by the deformation suppressing portion, and deformation of the vibrating portion due to deformation of the support can be suppressed.

[0011] The reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and the specific components described in the embodiments described below. [Brief explanation of the drawings]

[0012] [Figure 1] 2. FIG. 3 is a cross-sectional view of the piezoelectric element according to the first embodiment, taken along line II in FIG. [Figure 2] FIG. 2 is a top view of the piezoelectric element according to the first embodiment. [Figure 3] 1 is a cross-sectional view of a piezoelectric device according to a first embodiment. [Figure 4] FIG. 4 is a simulation diagram for explaining deformation of the vibrating section according to the first embodiment. [Figure 5] 1 is a perspective view of a piezoelectric device according to a first embodiment. [Figure 6] FIG. 1 is a top view of a piezoelectric device according to a first embodiment. [Figure 7] FIG. 2 is a top view of the piezoelectric device according to the first embodiment, with the vibrating portion omitted. [Figure 8] FIG. 2 is a perspective view of the piezoelectric device according to the first embodiment, with the vibrating portion omitted. [Figure 9]FIG. 7 is a cross-sectional view schematically showing a cross section taken along line IX-IX in FIG. 6. [Figure 10] FIG. 10 is an enlarged view of the X portion of FIG. 9. [Figure 11] 2A to 2C are cross-sectional views showing a manufacturing process of the piezoelectric element shown in FIG. [Figure 12] 12A to 12C are cross-sectional views showing the manufacturing process of the piezoelectric element following FIG. [Figure 13] 13A to 13C are cross-sectional views showing the manufacturing process of the piezoelectric element following FIG. 12. [Figure 14] 8 is a view corresponding to FIG. 7 of a piezoelectric element according to a first modified example of the first embodiment. FIG. [Figure 15] 8 is a view corresponding to FIG. 7 of a piezoelectric element according to a first modified example of the first embodiment. FIG. [Figure 16] 8 is a view corresponding to FIG. 7 of a piezoelectric element according to a second modified example of the first embodiment. FIG. [Figure 17] 7 is a view corresponding to FIG. 6 of a piezoelectric element according to a second embodiment. FIG. [Figure 18] 8 is a view corresponding to FIG. 7 of a piezoelectric element according to a second embodiment. [Figure 19] FIG. 18 is a cross-sectional view schematically showing a cross section taken along the line XIX-XIX in FIG. 17. [Figure 20] 18, showing a piezoelectric element according to a modified example of the second embodiment. FIG. DETAILED DESCRIPTION OF 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 will be given the same reference numerals, and their description may be omitted. Furthermore, in the embodiments, when only some of the components are described, the components described in the preceding embodiments can be applied to the remaining components. The following embodiments can be partially combined with each other, even if not specifically stated, as long as there is no particular problem with the combination.

[0014] (First embodiment) A piezoelectric element 1 according to a first embodiment will be described with reference to Figures 1 to 13. In this embodiment, an example will be described in which the piezoelectric element 1 is applied to a microphone, which is a piezoelectric device 10S described below. First, the piezoelectric element 1 will be described.

[0015] As shown in Figures 1 and 2, the piezoelectric element 1 of this embodiment includes a support 10 and a vibration section 20 laminated on the support 10. Hereinafter, the direction in which the support 10 and the vibration section 20 are laminated will also be referred to as a lamination direction D1. In addition, in the lamination direction D1, the direction from the support 10 toward the vibration section 20 will be referred to as a first lamination direction D1a, and in the lamination direction D1, the direction opposite to the first lamination direction D1a will be referred to as a second lamination direction D1b. As shown in Figure 2, the piezoelectric element 1 of this embodiment is formed in a rectangular shape when viewed from a direction perpendicular to the lamination direction D1.

[0016] The support 10 is formed to have a rectangular shape when viewed from a direction perpendicular to the stacking direction D1. The support 10 includes a support substrate 11 having a first substrate surface 11a, which is the surface on the first stacking direction D1a side, and a second substrate surface 11b, which is the surface on the second stacking direction D1b side, and an insulating film 12 formed on the first substrate surface 11a. The support 10 is formed with a recess 10a for floating the inner edge side of the vibrating section 20. 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 are formed to have a rectangular outer shape when viewed from a direction perpendicular to the stacking direction D1, and are formed into a square tube shape with a through-hole in the center.

[0017] The support substrate 11 has a substrate through hole 111 formed to penetrate in the stacking direction D1. The insulating film 12 has an insulating through hole 121 formed to penetrate in the stacking direction D1. The substrate through hole 111 and the insulating through hole 121 are formed to have a rectangular shape when viewed in a direction perpendicular to the stacking direction D1. In other words, the substrate through hole 111 and the insulating through hole 121 have a rectangular cross section perpendicular to the stacking direction D1. The substrate through hole 111 and the insulating through hole 121 have the same hole size.

[0018] The recess 10a of the support body 10 is formed by the substrate through-holes 111 and the insulating through-holes 121 continuing in the stacking direction D1. That is, the recess 10a is formed to penetrate in the stacking direction D1 and has a rectangular shape when viewed in a direction perpendicular to the stacking direction D1. As will be described later with reference to FIG. 7, the support substrate 11 has four hole corners 112, which are corners of the rectangular substrate through-holes 111. The substrate through-holes 111 correspond to openings, and the hole corners 112 correspond to opening corners. The support substrate 11 is provided with a deformation suppression section 90, which will be described later. The deformation suppression section 90 will be described in detail later.

[0019] The vibration section 20 constitutes the sensing section 30, which vibrates in response to external pressure, and is disposed on the surface of the support 10 on the first stacking direction D1a side. The vibration section 20 includes a support region 21a disposed on the support 10 and a floating region 21b connected to the support region 21a and floating above the recess 10a. The entire floating region 21b has a shape corresponding to the recess 10a, specifically, a substantially rectangular shape in plan view. That is, the floating region 21b has a rectangular shape when viewed from a direction perpendicular to the stacking direction D1, and is equal in size to the substrate through-hole 111 and the insulating through-hole 121. As shown in FIG. 2, the substantially rectangular floating region 21b has four floating corners 23.

[0020] As shown in FIGS. 1 and 2 , the floating region 21b of this embodiment has slits 41 formed therein, penetrating the floating region 21b in the stacking direction D1. The slits 41 of this embodiment are formed so as to divide the floating region 21b into four parts. Specifically, two slits 41 are formed so as to pass through the center C of the floating region 21b and extend across the floating region 21b from one of two opposing floating corners 23 in the floating region 21b to the other floating corner 23. In other words, the slits 41 extend from each of the four floating corners 23 of the floating region 21b, which has a substantially rectangular shape in plan view, toward the center C, and the slits 41 intersect at the center C. This separates the floating region 21b into four vibration regions 22, each having a substantially triangular shape in plan view.

[0021] In this embodiment, the widths of the two slits 41 are set so that the intervals between the vibrating regions 22 are the same. Here, the surface of the vibrating region 22 opposite the support 10 is referred to as the first vibrating surface 22a, the surface of the vibrating region 22 facing the support 10 is referred to as the second vibrating surface 22b, and the surface connecting the first vibrating surface 22a and the second vibrating surface 22b is referred to as the vibrating side surface 22c. The direction in which the slit 41 extends from one of the two opposing floating corner portions 23 to the other is referred to as the slit direction, and the dimension of the slit 41 in a direction perpendicular to the slit direction and the stacking direction D1 is referred to as the slit width 41a. The vibrating side surface 22c is flat and perpendicular to the stacking direction D1 and the slit direction. The slit width 41a of the slit 41 is constant from the first vibrating surface 22a side to the second vibrating surface 22b side.

[0022] Since each of the planar triangular vibration regions 22 is formed by dividing the floating region 21b as described above, the base side of the triangle is a fixed end supported by the support body 10 (i.e., the support region 21a). Each of the vibration regions 22 is a cantilever with the apex side opposite the base side being a free end. In other words, each of the vibration regions 22 is connected to the support region 21a and is cantilevered.

[0023] The vibration section 20 has a configuration including a piezoelectric film 50 and an electrode film 60 connected to the piezoelectric film 50. Specifically, the piezoelectric film 50 has a lower-layer piezoelectric film 51 and an upper-layer piezoelectric film 52 laminated on the lower-layer piezoelectric film 51. The electrode film 60 also has a lower-layer electrode film 61 disposed below the lower-layer piezoelectric film 51, an intermediate electrode film 62 disposed between the lower-layer piezoelectric film 51 and the upper-layer piezoelectric film 52, and an upper-layer electrode film 63 disposed on the upper-layer piezoelectric film 52. In other words, the vibration section 20 has a bimorph structure in which the lower-layer piezoelectric film 51 is sandwiched between the lower-layer electrode film 61 and the intermediate electrode film 62, and the upper-layer piezoelectric film 52 is sandwiched between the intermediate electrode film 62 and the upper-layer electrode film 63.

[0024] Furthermore, the vibration section 20 of this embodiment has an underlayer 70 on which the lower-layer piezoelectric film 51 and the lower-layer electrode film 61 are disposed. That is, the piezoelectric film 50 and the electrode film 60 are disposed on the support 10 via the underlayer 70. The underlayer 70 is not necessarily required, but is provided to facilitate crystal growth when forming the lower-layer piezoelectric film 51 and the like. The underlayer 70 is made of AlN or the like.

[0025] The lower-layer piezoelectric film 51 and the upper-layer piezoelectric film 52 are made of ScAlN. The lower-layer electrode film 61, the intermediate electrode film 62, etc. are made of molybdenum, copper, platinum, titanium, aluminum, etc. The piezoelectric film 50 has a thickness of about 1 μm, and the base film 70 has a thickness of about several tens of nanometers. In other words, the base film 70 is extremely thin compared to the piezoelectric film 50.

[0026] In addition, in each vibration region 22 of this embodiment, the fixed end side is defined as a first region R1, and the free end side is defined as a second region R2. The lower electrode film 61, the intermediate electrode film 62, and the upper electrode film 63 are formed in the first region R1 and the second region R2, respectively. However, the lower electrode film 61, the intermediate electrode film 62, and the upper electrode film 63 formed in the first region R1 are separated and insulated from the lower electrode film 61, the intermediate electrode film 62, and the upper electrode film 63 formed in the second region R2. The lower electrode film 61, the intermediate electrode film 62, and the upper electrode film 63 formed in the first region R1 are appropriately extended to the support region 21a.

[0027] The lower electrode film 61, the intermediate electrode film 62, and the upper electrode film 63 are formed so as not to reach the slits 41. That is, the lower electrode film 61, the intermediate electrode film 62, and the upper electrode film 63 formed in the second region R2 are formed so as to terminate more inward than the vibrating side surface 22c of the vibrating region 22. In other words, the lower electrode film 61, the intermediate electrode film 62, and the upper electrode film 63 are disposed more inward than the slits 41 when viewed in the stacking direction D1.

[0028] In the support region 21a of the vibrating section 20, a first electrode section 81 electrically connected to the lower-layer electrode film 61 and the upper-layer electrode film 63 formed in the first region R1, and a second electrode section 82 electrically connected to the intermediate electrode film 62 formed in the first region R1 are formed. Note that FIG. 1 is a cross-sectional view taken along line II in FIG. 2, and the vibrating section 22 on the left side of the page and the vibrating section 22 on the right side of the page show different cross sections. Also, in FIG. 2, the first electrode section 81 and the second electrode section 82 are omitted. Also, in FIG. 5 (described later) and the like, the first electrode section 81, the second electrode section 82, and the like are omitted as appropriate.

[0029] The first electrode portion 81 is formed in a first hole portion 81a that penetrates the upper-layer electrode film 63, the upper-layer piezoelectric film 52, and the lower-layer piezoelectric film 51 to expose the lower-layer electrode film 61, and has a first through electrode 81b electrically connected to the lower-layer electrode film 61 and the upper-layer electrode film 63. The first electrode portion 81 also has a first pad portion 81c formed on the first through electrode 81b and electrically connected to the first through electrode 81b. The second electrode portion 82 is formed in a second hole portion 82a that penetrates the upper-layer piezoelectric film 52 to expose the intermediate electrode film 62, and has a second through electrode 82b electrically connected to the intermediate electrode film 62. The second electrode portion 82 also has a second pad portion 82c formed on the second through electrode 82b and electrically connected to the second through electrode 82b. Like the electrode film 60, the first electrode portion 81 and the second electrode portion 82 are made of molybdenum, copper, platinum, titanium, aluminum, or the like.

[0030] The lower electrode film 61, intermediate electrode film 62, and upper electrode film 63 formed in the second region R2 are not electrically connected to the first electrode portion 81 and the second electrode portion 82, and are in a floating state. Therefore, the lower electrode film 61, intermediate electrode film 62, and upper electrode film 63 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 51 and the upper piezoelectric film 52 located in the second region R2.

[0031] Furthermore, the lower electrode film 61, the intermediate electrode film 62, and the upper electrode film 63 formed in the first region R1 are divided into each vibrating region 22 by the slits 41. That is, the lower electrode film 61, the intermediate electrode film 62, and the upper electrode film 63 formed in the first region R1 of each vibrating region 22 are not formed so as to straddle each vibrating region 22. The lower electrode film 61, the intermediate electrode film 62, and the upper electrode film 63 formed in the first region R1 of each vibrating region 22 are connected via a wiring film or the like (not shown).

[0032] In this embodiment, the lower electrode film 61, the intermediate electrode film 62, and the upper electrode film 63 are formed so that their outer shapes are substantially the same as the outer shape of the vibration region 22, and are rectangular in plan view in this embodiment. However, the lower electrode film 61, the intermediate electrode film 62, and the upper electrode film 63 are divided by each vibration region 22 as described above. Therefore, the outer shapes of the lower electrode film 61, the intermediate electrode film 62, and the upper electrode film 63 here refer to shapes formed by the outer lines of the lower electrode film 61, the intermediate electrode film 62, and the upper electrode film 63 and extensions of these outer lines.

[0033] The sensing unit 30 of this embodiment is configured to output a change in charge in the four vibration regions 22 as one pressure detection signal. That is, the four vibration regions 22 are electrically connected in series. More specifically, each of the four vibration regions 22 has a bimorph structure, and the lower electrode films 61, intermediate electrode films 62, and upper electrode films 63 formed in each vibration region 22 are connected in parallel, while the vibration regions 22 are connected in series.

[0034] The above is the configuration of the piezoelectric element 1 in this embodiment. When sound pressure is applied to each vibration region 22 (i.e., sensing portion 30) of such a piezoelectric element 1, each vibration region 22 vibrates. In this case, for example, when the free end side of the vibration region 22 is displaced upward, tensile stress is generated in the lower-layer piezoelectric film 51 and compressive stress is generated in the upper-layer piezoelectric film 52. Therefore, sound pressure can be detected by extracting the electric charge from the first electrode portion 81 and the second electrode portion 82.

[0035] At this time, the stress generated in the vibration region 22 (i.e., the piezoelectric film 50) is greater at the fixed end than at the free end because the stress is released at the free end. In other words, less charge is generated at the free end, and the signal-to-noise ratio (SN ratio) tends to be smaller. For this reason, in the piezoelectric element 1 of this embodiment, as described above, each vibration region 22 is divided into a first region R1 where stress tends to be large and a second region R2 where stress tends to be small. In the piezoelectric element 1, the lower electrode film 61, the upper electrode film 63, and the intermediate electrode film 62 arranged in the first region R1 are connected to the first electrode portion 81 and the second electrode portion 82, respectively, so that the charge generated in the lower piezoelectric film 51 and the upper piezoelectric film 52 located in the first region R1 can be extracted. This prevents the influence of noise from becoming too large.

[0036] Next, a piezoelectric device 10S using the piezoelectric element 1 will be described with reference to Fig. 3. As shown in Fig. 3, the piezoelectric device 10S of this embodiment is configured as a microphone in which the piezoelectric element 1 is housed in a casing 100. The piezoelectric device 10S includes the piezoelectric element 1, a circuit board (not shown) that performs predetermined signal processing, etc., and a printed circuit board 101 that houses the piezoelectric element 1 and the circuit board. The casing 100 has the printed circuit board 101 on which the piezoelectric element 1 and the circuit board (not shown) are mounted, and a lid 102 that is fixed to the printed circuit board 101 so as to house the piezoelectric element 1 and the circuit board.

[0037] Although not shown, the printed circuit board 101 is configured to have wiring sections and through-hole electrodes appropriately formed thereon, and also has electronic components such as capacitors (not shown) mounted thereon as necessary. The printed circuit board 101 has a mounting surface 101a on the side in the first stacking direction D1a on which the piezoelectric element 1 is mounted. The second substrate surface 11b of the support substrate 11 is mounted on the mounting surface 101a via a bonding member 2 such as an adhesive. The bonding member 2 can be made of, for example, a thermosetting resin such as epoxy resin. The piezoelectric element 1 and the circuit board are electrically connected to each other via, for example, bonding wires, with the first pad portion 81c and the second pad portion 82c.

[0038] The lid 102 is made of metal, plastic, resin, or the like, and is fixed to the printed circuit board 101 via a bonding material such as an adhesive (not shown) so as to accommodate the piezoelectric element 1 and the circuit board. A sound hole 101b through which sound pressure is introduced is formed in the printed circuit board 101. The sound hole 101b is formed by penetrating the printed circuit board 101 in the stacking direction D1 in a portion of the printed circuit board 101 facing the sensing unit 30. The sound hole 101b is substantially cylindrical, and is formed so that its central axis coincides with the center C of the vibration region 22 when viewed in a direction perpendicular to the stacking direction D1. In other words, the cross section of the sound hole 101b perpendicular to the stacking direction D1 is formed to be circular. The sound hole 101b corresponds to a through hole.

[0039] The above is the configuration of the piezoelectric device 10S in this embodiment. Hereinafter, the space within the casing 100 between the portion where the sound hole 101b is formed and the vibration region 22 will be referred to as the pressure-receiving surface space S1. The back space S2 will include a space located on the opposite side of the vibration region 22 from the pressure-receiving surface space S1, and will be connected to this space without the slit 41. The back space S2 can be said to be a space within the casing 100 that is different from the pressure-receiving surface space S1, or a space excluding the pressure-receiving surface space S1. In other words, the pressure-receiving surface space S1 can be said to be a space that influences the pressure on the surface of the vibration region 22 on the sound hole 101b side of the casing 100 (i.e., the second vibration surface 22b in this embodiment). The back space S2 can also be said to be a space that influences the pressure on the surface of the vibration region 22 on the opposite side of the sound hole 101b side of the casing 100 (i.e., the first vibration surface 22a in this embodiment).

[0040] In such a piezoelectric device 10S, sound pressure is introduced as pressure into the pressure-receiving surface space S1, whereby sound pressure is applied to the vibration region 22 (that is, the sensing section 30), and the sound pressure is detected as described above.

[0041] As described above, the piezoelectric element 1 is mounted on the mounting surface 101a of the printed circuit board 101 by the bonding member 2, with the second substrate surface 11b of the support substrate 11 being connected to the mounting surface 101a of the printed circuit board 101. The bonding member 2 for bonding the piezoelectric element 1 to the printed circuit board 101 can be made of a thermosetting resin such as epoxy resin. If the thermal expansion coefficients of the support substrate 11, which is made of a silicon substrate, and the printed circuit board 101 are different from each other, the support substrate 11 may be deformed when the piezoelectric element 1 is mounted on the printed circuit board 101. When the support substrate 11 is deformed, the vibration section 20 may be warped in a direction intersecting the stacking direction D1, as shown in FIG. 4 . When the vibration section 20 is bent, the second moment of area of ​​the vibration section 20 increases.

[0042] As a result, when sound pressure is applied to each vibrating region 22, the free end side of the vibrating region 22 becomes less likely to displace, inhibiting the vibration of each vibrating region 22. This causes a decrease in the sensitivity of the piezoelectric element 1 when detecting sound pressure. Therefore, the piezoelectric element 1 of this embodiment is provided with a deformation suppression section 90 that suppresses deformation of the support substrate 11.

[0043] The deformation suppression section 90 will be described with reference to Figs. 5 to 10. Note that the lid section 102 is not shown in Figs. 5 to 10. Also, in Fig. 6, the vibration section 20 is shown as a see-through view, and the deformation suppression section 90 and sound hole 101b covered by the vibration section 20 are shown by dashed lines. Furthermore, in Figs. 7 and 8, the vibration section 20 is not shown.

[0044] As shown in FIGS. 5 to 8, the support body 10 of this embodiment is provided with a deformation suppression portion 90 that suppresses deformation of the support substrate 11. The deformation suppression portion 90 is provided on the support substrate 11 and is formed integrally with the support substrate 11. That is, in this embodiment in which the support substrate 11 is made of a silicon substrate, the deformation suppression portion 90 is also made of a silicon substrate. The deformation suppression portion 90 is formed so as to divide into four the space surrounded by the recess 10a of the support body 10 within the pressure-receiving surface space S1. That is, the deformation suppression portion 90 is formed so as to divide the substrate through-hole 111 into four.

[0045] 7, the substrate through hole 111 of this embodiment is formed in a rectangular shape when viewed in a direction perpendicular to the stacking direction D1, and has four hole corners 112, which are corners of the rectangular substrate through hole 111. Hereinafter, one of a pair of opposing hole corners 112 of the four hole corners 112 will be referred to as a first hole corner 112a, and the other will be referred to as a second hole corner 112b. Furthermore, one of the remaining pair of opposing hole corners 112 of the four hole corners 112 will be referred to as a third hole corner 112c, and the other will be referred to as a fourth hole corner 112d.

[0046] In this embodiment, two deformation suppression portions 90 are formed so as to pass through the hole center HC of the substrate through hole 111 and extend across the substrate through hole 111 from one side to the other side of two opposing hole corners 112 in the substrate through hole 111. The two deformation suppression portions 90 are formed in a diagonal brace shape so as to intersect with each other at the hole center HC.

[0047] Hereinafter, one of the two deformation suppression portions 90 may be referred to as the first crossing suppression portion 90a and the other as the second crossing suppression portion 90b. The first crossing suppression portion 90a is formed to extend across the substrate through hole 111 from the first hole corner 112a to the second hole corner 112b. The second crossing suppression portion 90b is formed to extend across the substrate through hole 111 from the third hole corner 112c to the fourth hole corner 112d.

[0048] By providing the deformation suppression portion 90 on the support substrate 11 in this manner, the annular support substrate 11, which has a rectangular outer diameter when viewed in a direction perpendicular to the stacking direction D1 and has the substrate through-hole 111, has high rigidity and is less likely to deform. This makes it possible to suppress deformation of the support substrate 11 caused by the difference in thermal expansion coefficient between the support substrate 11 and the printed circuit board 101, and to suppress deformation of the vibrating portion 20 associated with deformation of the support substrate 11. This makes it possible to suppress a decrease in the detection sensitivity of the piezoelectric element 1 caused by an increase in the second moment of area of ​​the vibrating portion 20.

[0049] As described above, the vibrating section 20 has a support region 21a arranged on the support body 10 and a floating region 21b floating above the recess 10a. The recess 10a has a structure in which the substrate through-hole 111 and the insulating through-hole 121 are connected in the stacking direction D1. Therefore, each of the four floating corners 23 of the floating region 21b overlaps with each of the four hole corners 112 of the support substrate 11 in the stacking direction D1.

[0050] Therefore, the two slits 41 formed by extending from one side to the other of the two opposing floating corners 23 and the two deformation suppression portions 90 formed by extending from one side to the other of the two opposing hole corners 112 overlap in the stacking direction D1. In other words, the deformation suppression portions 90 are provided at positions that overlap the slits 41 in the stacking direction D1.

[0051] However, as shown in Figures 9 and 10, the deformation suppression section 90 is separated from the vibrating section 20 in the stacking direction D1. That is, a gap is provided between the surface of the deformation suppression section 90 on the first stacking direction D1a side and the second vibrating surface 22b of the vibrating section 20, and they are not in contact with each other when the vibrating section 20 is not vibrating. The positional relationship and dimensional relationship between the deformation suppression section 90 and the vibrating section 20 will be described with reference to Figures 9 and 10. Note that Figures 9 and 10 are schematic diagrams that omit illustration of each film that constitutes the vibrating section 20, and therefore omit illustration of the piezoelectric film 50, electrode film 60, and base film 70, as well as the first electrode section 81 and second electrode section 82, etc.

[0052] Here, the extension direction is defined as the direction in which the first crossing suppression portion 90a and the second crossing suppression portion 90b extend from one side to the other side of the two opposing hole corner portions 112. In this embodiment, in which the two slits 41 and the first crossing suppression portion 90a and the second crossing suppression portion 90b are arranged in positions where they overlap each other in the stacking direction D1, the extension direction coincides with the slit direction.

[0053] 10, the dimension of the deformation suppression portion 90 in the direction perpendicular to the extension direction and the stacking direction D1 is defined as a suppression portion width 90c. The distance between the deformation suppression portion 90 and the vibrating portion 20 in the stacking direction D1 is defined as a suppression portion distance 90d. In this embodiment, the suppression portion width 90c is larger than the slit width 41a. The suppression portion distance 90d is smaller than the suppression portion width 90c and the slit width 41a.

[0054] The suppression portion width 90c and the slit width 41a are not necessarily uniform, and the shapes and dimensions of the suppression portion width 90c and the slit width 41a may change due to manufacturing errors or the like when manufacturing the piezoelectric element 1. The suppression portion distance 90d may also change due to warping or the like of the vibrating portion 20, and even a slight warping can easily change the dimensions on the free end side of the vibrating region 22 in particular.

[0055] Therefore, the phrase "the suppression portion width 90c is larger than the slit width 41a" does not have a strict meaning, but rather indicates a state in which most of the suppression portion width 90c is larger than the slit width 41a, and may include a state in which a portion of the suppression portion width 90c is slightly smaller than the slit width 41a due to manufacturing errors, etc. Furthermore, the phrase "the suppression portion distance 90d is smaller than the suppression portion width 90c and the slit width 41a" does not have a strict meaning, but may include a state in which, for example, the suppression portion distance 90d of the entire area of ​​the deformation suppression portion 90, in a portion facing the free end side of the vibration region 22, is slightly larger than the suppression portion width 90c and the slit width 41a. Note that the deformation suppression portion 90 may be separated from or in contact with the printed circuit board 101 in the stacking direction D1.

[0056] Next, a method for manufacturing the piezoelectric element 1 will be described with reference to FIGS.

[0057] First, as shown in Fig. 11, a support substrate 11 is prepared, and an insulating film 12 is formed on a first substrate surface 11a of the support substrate 11. This forms a support body 10 in a state before the recess 10a is formed. The size of the support substrate 11 in the stacking direction D1, i.e., the plate thickness, is approximately 500 µm. The size of the insulating film 12 in the stacking direction D1, i.e., the film thickness, is approximately 0.5 µm.

[0058] Then, the vibrating section 20 is constructed by forming a base film 70, a piezoelectric film 50, an electrode film 60, etc. on the support body 10 having the support substrate 11 and the insulating film 12. The base film 70, the piezoelectric film 50, and the electrode film 60 are constructed by appropriately performing general sputtering, etching, etc. The position of the electrode film 60 is adjusted so that it is not exposed from the portion where the slit 41 is formed.

[0059] 11 does not show details of the base film 70, the piezoelectric film 50, the electrode film 60, etc. Although not shown, the first electrode portion 81 and the second electrode portion 82 are provided after the base film 70, the piezoelectric film 50, and the electrode film 60 are formed. The size of the vibration portion 20 in the stacking direction D1, i.e., the film thickness, is approximately 1 μm.

[0060] Then, slits 41 are formed in the vibrating part 20. The slits 41 can be formed, for example, by covering with a mask material portions of the piezoelectric film 50 and the electrode film 60 where the slits 41 are not to be formed, and performing dry etching. Furthermore, the etching for forming the slits 41 is performed so as to penetrate through the piezoelectric film 50 and the base film 70. In this embodiment, two intersecting slits 41 are formed so as to form four vibrating regions 22.

[0061] Next, as shown in FIG. 12, a protective resist P is placed to cover the vibration section 20. Then, using a mask (not shown), etching is performed so as to penetrate from the second substrate surface 11b side of the support substrate 11 to the first substrate surface 11a side, forming the recess 10a and the deformation suppression section 90. As described above, the mask portion for forming the deformation suppression section 90 is positioned so that the deformation suppression section 90 faces the slit 41. For example, dry etching can be used for the etching to form the recess 10a and the deformation suppression section 90.

[0062] By forming the recess 10a and the deformation suppression portion 90 in this manner, it is possible to simultaneously form the recess 10a and the deformation suppression portion 90. That is, the deformation suppression portion 90 can be provided on the support substrate 11 without adding an additional step for forming the deformation suppression portion 90. Furthermore, by arranging the protective resist P that covers the vibrating portion 20, it is possible to prevent the vibrating region 22 from being destroyed when the recess 10a and the deformation suppression portion 90 are formed.

[0063] 13, etching is then performed to reach the base film 70, removing a portion of the insulating film 12 to form an insulating through-hole 121. Specifically, portions of the insulating film 12 facing the recess 10a and the deformation suppression portion 90 in the stacking direction D1 are removed by etching to form the insulating through-hole 121. Wet etching, for example, can be used for etching to remove the insulating film 12. Then, the protective resist P covering the vibrating portion 20 is removed. This completes the manufacturing process of the piezoelectric element 1 shown in FIG. 1, in which four vibrating regions 22 floating above the support 10 are formed and the deformation suppression portion 90 is provided on the support substrate 11.

[0064] Incidentally, ScAlN, which constitutes the piezoelectric film 50, is a material that is difficult to etch. Furthermore, according to the study by the present inventors, when the slits 41 penetrating the piezoelectric film 50 are formed by etching, it is difficult to reduce the slit width 41a. For example, when the slits 41 are formed by the above-described manufacturing method, the slit width 41a is approximately 1 μm.

[0065] However, the size of the slit width 41a affects the increase or decrease in acoustic resistance when sound passes through the slit 41; the larger the slit width 41a, the lower the acoustic resistance. The lower the acoustic resistance, the lower the sensitivity in the low-frequency band. Therefore, to prevent sound pressure from passing through the slit 41 and prevent a decrease in sensitivity in the low-frequency band, it is necessary to make the slit width 41a as small as possible. However, when forming the slit 41 by etching in a piezoelectric film 50 made of ScAlN, which is a material that is difficult to etch, there is a limit to how small the slit width 41a can be, and it is difficult to make it significantly smaller than 1 μm.

[0066] In contrast to this, by making the suppression section distance 90d, which is the distance between the vibration section 20 and the deformation suppression section 90, smaller than the slit width 41a, it is possible to increase the acoustic resistance by the space between the vibration section 20 and the deformation suppression section 90. Here, in the piezoelectric element 1 of this embodiment, the space between the vibration section 20 and the deformation suppression section 90 is formed by removing the insulating film 12 by wet etching.

[0067] The insulating film 12 is made of an oxide film or the like and has a thickness of approximately 0.5 μm. This allows the suppression portion distance 90d to be half the slit width 41a, which is approximately 1 μm. This prevents sound pressure from escaping between the vibrating portion 20 and the deformation suppression portion 90, and prevents a decrease in sensitivity in the low frequency range caused by the slit 41.

[0068] As described above, the piezoelectric element 1 of this embodiment includes the support 10, the vibration section 20 that is stacked on the support 10 along the stacking direction D1 and vibrates in response to externally applied pressure, and the deformation suppression section 90 that is disposed at a distance from the vibration section 20 and suppresses deformation of the support substrate 11 of the support 10. The vibration section 20 has a support region 21a that is supported by the support 10, and a floating region 21b that is connected to the support region 21a and floats above the support 10. The support 10 faces the floating region 21b and has a substrate through-hole 111 that opens to the floating region 21b. The deformation suppression section 90 is disposed across the substrate through-hole 111.

[0069] According to this, the deformation suppression section 90 can increase the rigidity of the support substrate 11, and can suppress deformation of the vibration section 20 that accompanies deformation of the support substrate 11. Furthermore, deformation of the vibration section 20 can suppress a decrease in the detection sensitivity of the piezoelectric element 1 that is caused by an increase in the second moment of area of ​​the vibration section 20.

[0070] Furthermore, according to the above embodiment, the following effects can be obtained.

[0071] (1) In the above embodiment, the vibration section 20 is formed with slits 41 that divide the floating region 21b into four vibration regions 22. The deformation suppression section 90 is formed to extend along the slit direction and is positioned to overlap the slit 41 in the stacking direction D1 and face the slit 41. The suppression section distance 90d is smaller than the slit width 41a. The suppression section width 90c is larger than the slit width 41a.

[0072] This makes it possible to increase acoustic resistance by using the space between the vibration section 20 and the deformation suppression section 90. Therefore, it is possible to suppress sound pressure from escaping between the vibration section 20 and the deformation suppression section 90, and to suppress a decrease in sensitivity in the low frequency band caused by the slits 41.

[0073] (2) In the above embodiment, the substrate through hole 111 has a rectangular cross-sectional shape perpendicular to the stacking direction D1, and includes a first hole corner 112a and a second hole corner 112b facing each other on the inside, and a third hole corner 112c and a fourth hole corner 112d facing each other on the inside. The deformation suppression portion 90 includes a first intersection suppression portion 90a and a second intersection suppression portion 90b that intersect. The first intersection suppression portion 90a is formed by extending across the substrate through hole 111 from the first hole corner 112a to the second hole corner 112b. The second intersection suppression portion 90b is formed by extending across the substrate through hole 111 from the third hole corner 112c to the fourth hole corner 112d.

[0074] This allows the rigidity of the support substrate 11 to be made relatively high with a relatively simple configuration.

[0075] (First modified example of the first embodiment) In the above-described first embodiment, an example was described in which two deformation suppression portions 90 are formed so as to extend across the substrate through hole 111 from one of the two opposing hole corner portions 112 in the substrate through hole 111 to the other hole corner portion 112, but the present invention is not limited to this.

[0076] For example, as shown in FIG. 14, the deformation suppression portion 90 may be formed on only one of the two opposing hole corners 112 in the substrate through hole 111, extending across the substrate through hole 111 from the first hole corner 112a to the second hole corner 112b.

[0077] Alternatively, as shown in Fig. 15, three deformation suppression portions 90 may be formed so as to extend from a position different from the hole corner 112 across the substrate through hole 111 to a position different from the hole corner 112. Specifically, the deformation suppression portions 90 may be formed so as to extend across the substrate through hole 111 from one side to the other side of two opposing sides of the four sides surrounding the substrate through hole 111. In this case, the deformation suppression portions 90 may be formed so as to pass through the hole center HC of the substrate through hole 111, or may be formed so as not to pass through the hole center HC of the substrate through hole 111. Alternatively, although not shown, four or more deformation suppression portions 90 may be formed.

[0078] (Second modified example of the first embodiment) In the above-described first embodiment, an example was described in which the substrate through hole 111 and the insulating through hole 121 are formed in a rectangular shape when viewed in a direction perpendicular to the stacking direction D1, and the cross sections of the substrate through hole 111 and the insulating through hole 121 perpendicular to the stacking direction D1 are rectangular, but this is not limiting.

[0079] For example, as shown in Fig. 16, the substrate through hole 111 and the insulating through hole 121 may have a circular shape when viewed in a direction perpendicular to the stacking direction D1, and a circular cross section perpendicular to the stacking direction D1. In this case, the deformation suppression portion 90 may be formed so as to start from any part of the circumference surrounding the substrate through hole 111 and extend across the substrate through hole 111 to a part different from the starting point. Furthermore, the deformation suppression portion 90 may be formed so as to pass through the center of the substrate through hole 111 as shown in Fig. 16, or may be formed so as not to pass through the center of the substrate through hole 111, although not shown. Alternatively, two or more deformation suppression portions 90 may be formed, although not shown.

[0080] (Second embodiment) Next, a second embodiment will be described with reference to FIGS. 17 to 19. In this embodiment, the shape of the deformation suppression portion 90 is different from that of the first embodiment. Other than this, the second embodiment is similar to the first embodiment. Therefore, in this embodiment, the differences from the first embodiment will be mainly described, and descriptions of the same parts as the first embodiment may be omitted.

[0081] The deformation suppression section 90 of this embodiment will be described with reference to FIGS. 17 to 19. In FIG. 17, the vibration section 20 is shown as a see-through view, and the deformation suppression section 90 and sound hole 101b covered by the vibration section 20 are indicated by dashed lines. FIG. 19 is a schematic diagram in which the films constituting the vibration section 20 are not shown, omitting the piezoelectric film 50, electrode film 60, and base film 70, as well as the first electrode section 81 and second electrode section 82. As shown in FIG. 19, the deformation suppression section 90 of this embodiment is smaller in size in the stacking direction D1 than the deformation suppression section 90 of the first embodiment. A gap is provided between the deformation suppression section 90 and the support substrate 11, so that they are not in contact with each other.

[0082] 17 and 18, the deformation suppression portion 90 of this embodiment is formed so as to bypass the sound hole 101b formed in the printed circuit board 101. That is, the deformation suppression portion 90 of this embodiment is formed in a position that does not overlap with the sound hole 101b in the stacking direction D1. The deformation suppression portion 90 has four linear suppression portions 91 that extend linearly from the hole corner portions 112 toward the hole center HC of the substrate through-hole 111, and one cylindrical suppression portion 92 that is connected to the four linear suppression portions 91 and is formed in a cylindrical shape so as to surround the sound hole 101b when viewed in a direction perpendicular to the stacking direction D1.

[0083] Each of the four linear suppression portions 91 extends across the substrate through hole 111 from one of the four hole corners 112 toward the opposing hole corner 112 and up to the cylindrical suppression portion 92. The four linear suppression portions 91 are provided at positions that overlap with the slits 41 in the stacking direction D1. Specifically, one linear suppression portion 91 extending from one of the four hole corners 112 overlaps, in the stacking direction D1, with one slit 41 extending from a floating corner 23 that overlaps with that hole corner 112 in the stacking direction D1.

[0084] The four linear suppression portions 91 have dimensions in a direction perpendicular to the slit direction and the stacking direction D1 that are equal to the suppression portion width 90c of the deformation suppression portion 90 of the first embodiment. The linear suppression portions 91 have dimensions in a direction perpendicular to the slit direction and the stacking direction D1 that are greater than the slit width 41a.

[0085] The cylindrical suppression portion 92 has a cylindrical shape extending in the stacking direction D1, and has an inner diameter that is approximately equal to the inner diameter of the sound hole 101b. The cylindrical suppression portion 92 is arranged so that its axis is coaxial with the axis of the sound hole 101b and the axis of the board through-hole 111. The surface of the cylindrical suppression portion 92 on the second stacking direction D1b side faces, but is spaced apart from, the surface of the printed circuit board 101 on the first stacking direction D1a side. A gap is formed between the surface of the cylindrical suppression portion 92 on the second stacking direction D1b side and the surface of the printed circuit board 101 on the first stacking direction D1a side. This forms a flow path between the cylindrical suppression portion 92 and the printed circuit board 101 into which sound introduced from the sound hole 101b can flow.

[0086] In this way, the deformation suppression portion 90 of this embodiment, which is composed of four linear suppression portions 91 and one cylindrical suppression portion 92, is formed so as not to overlap with the sound hole 101b in the stacking direction D1. When sound pressure is applied to the piezoelectric device 10S and the vibration region 22 of the piezoelectric device 10S vibrates, the resonant frequency of the vibration region 22 is affected by the shape of the sound hole 101b. Specifically, the larger the inner diameter of the sound hole 101b, the higher the resonant frequency of the vibration region 22. Furthermore, the longer the length of the sound hole 101b, the lower the resonant frequency of the vibration region 22.

[0087] The higher the resonant frequency of the vibrating region 22, the higher the sensitivity in the high frequency band, and the wider the frequency band can be improved. On the other hand, the lower the resonant frequency of the vibrating region 22, the lower the sensitivity in the high frequency band, and the narrower the band in which sound can be detected. Hereinafter, as shown in FIG. 19, the inner diameter of the sound hole 101b will be referred to as the sound hole diameter φ, and the length of the sound hole 101b will be referred to as the sound hole length d. The sound hole length d is the size of the sound hole 101b in the stacking direction D1.

[0088] Here, if the deformation suppression part 90 were positioned at a position overlapping with the sound hole 101b in the stacking direction D1, the deformation suppression part 90 would be between the sound hole 101b and the vibration region 22, making it difficult for sound that has passed through the sound hole 101b to reach the vibration region 22. For this reason, when the deformation suppression part 90 and the sound hole 101b overlap in the stacking direction D1, the sound hole diameter φ becomes smaller compared to when the deformation suppression part 90 and the sound hole 101b do not overlap in the stacking direction D1.

[0089] As a result, the resonant frequency at which the vibrating region 22 vibrates is lower than when the deformation suppression section 90 and the sound hole 101b do not overlap in the stacking direction D1. This lower resonant frequency may result in a decrease in sensitivity in the high-frequency band. Therefore, the deformation suppression section 90 of this embodiment is positioned so as not to overlap with the sound hole 101b in the stacking direction D1.

[0090] Furthermore, if the cylindrical suppression portion 92 is formed so that there is no gap between the surface of the cylindrical suppression portion 92 on the second stacking direction D1b side and the surface of the printed circuit board 101 on the first stacking direction D1a side, the space surrounded by the sound hole 101b will communicate with the space surrounded by the cylindrical suppression portion 92. This will extend the length of the hole through which sound passes when sound pressure is applied to the piezoelectric device 10S.

[0091] As a result, the resonant frequency at which the vibrating region 22 vibrates is smaller than when a gap is formed between the cylindrical suppression portion 92 and the printed circuit board 101. The lower resonant frequency may result in a decrease in sensitivity in the high frequency band. Therefore, the deformation suppression portion 90 of this embodiment is formed so as to have a gap between the surface of the cylindrical suppression portion 92 on the second stacking direction D1b side and the surface of the printed circuit board 101 on the first stacking direction D1a side. The deformation suppression portion 90 is formed so that sound can flow through the gap thus formed.

[0092] The resonant frequency of the vibrating region 22 when it vibrates is affected by the acoustic inertance of the piezoelectric device 10S. Specifically, the resonant frequency of the vibrating region 22 is inversely proportional to the acoustic inertance of the piezoelectric device 10S. For this reason, it is desirable to form the piezoelectric device 10S so that the acoustic inertance of the piezoelectric device 10S is as small as possible.

[0093] In the piezoelectric device 10S of this embodiment, there are two acoustic inertances: the acoustic inertance between the cylindrical suppression portion 92 and the printed circuit board 101, and the acoustic inertance inside the sound hole 101b. The resonance frequency of the vibration region 22 is strongly influenced by the larger of these two acoustic inertances. Here, the acoustic inertance inside the sound hole 101b is referred to as sound hole inertance L1, and the acoustic inertance between the cylindrical suppression portion 92 and the printed circuit board 101 is referred to as suppression inertance L2.

[0094] When the cylindrical suppression portion 92 is configured so that the suppression inertance L2 is greater than the acoustic hole inertance L1, the acoustic inertance of the piezoelectric device 10S is strongly affected by the suppression inertance L2. As a result, the acoustic inertance of the piezoelectric device 10S becomes larger than in a configuration in which the deformation suppression portion 90 is not provided in the piezoelectric element 1. This is undesirable because it reduces the resonance frequency of the vibration region 22 and causes a decrease in sensitivity in the high frequency band.

[0095] In contrast, if the cylindrical suppression section 92 is configured so that the sound hole inertance L1 is greater than the suppression inertance L2, the acoustic inertance of the piezoelectric device 10S is strongly affected by the sound hole inertance L1. In other words, the acoustic inertance of the piezoelectric device 10S can be made closer to the acoustic inertance in a state in which the deformation suppression section 90 is not provided on the piezoelectric element 1. For this reason, the deformation suppression section 90 of this embodiment has the cylindrical suppression section 92 formed so that the sound hole inertance L1 is greater than the suppression inertance L2.

[0096] Here, general acoustic inertance can be found by multiplying the density of air by the length of the flow path through which sound flows, and dividing the result by the cross-sectional area of ​​the flow path. Therefore, the sound hole inertance L1 is calculated using the following formula 1.

[0097] (Number 1) L1=ρd / π(1 / 2φ) 2 In Equation 1, ρ is the density of air. Furthermore, d in Equation 1 is the above-mentioned sound hole length d, and φ is the sound hole diameter φ. Furthermore, π in Equation 1 is the ratio of the circumference of a circle to its circumference.

[0098] The suppression inertance L2 is calculated by the following equation 2.

[0099] (Number 2) L2=ρw / πrt In Equation 2, ρ represents the density of air. Furthermore, w in Equation 2 represents the size of the cylindrical suppression portion 92 in a direction extending radially from the axis of the cylindrical suppression portion 92, as shown in FIG. 19. That is, w in Equation 2 represents the thickness of the outer wall portion of the cylindrical suppression portion 92. Furthermore, r in Equation 2 represents the inner diameter of the cylindrical suppression portion 92. Furthermore, t in Equation 2 represents the dimension in the stacking direction D1 between the surface of the cylindrical suppression portion 92 on the second stacking direction D1b side and the surface of the printed circuit board 101 on the first stacking direction D1a side.

[0100] In the deformation suppression section 90 of this embodiment, the shape of the cylindrical suppression section 92 is set so that the acoustic hole inertance L1 is greater than the suppression inertance L2. This makes it possible to bring the acoustic inertance of the piezoelectric device 10S closer to the acoustic inertance of the piezoelectric element 1 without the deformation suppression section 90. Therefore, it is possible to suppress a decrease in the resonance frequency of the vibrating region 22 caused by providing the deformation suppression section 90, and to suppress a decrease in sensitivity in the high frequency band.

[0101] As described above, the piezoelectric device 10S of this embodiment includes a casing 100 having a printed circuit board 101 on which a piezoelectric element 1 is mounted, a lid 102 fixed to the printed circuit board 101 while accommodating the piezoelectric element 1, and a sound hole 101b formed therein that communicates with the outside and through which sound pressure is introduced. The support body 10 is disposed on the printed circuit board 101. The sound hole 101b penetrates the printed circuit board 101 in the stacking direction D1 and communicates with the board through-hole 111. The deformation suppression part 90 faces the printed circuit board 101 at a distance in the stacking direction D1, and is disposed in a position that does not overlap with the sound hole 101b in the stacking direction D1.

[0102] This makes it possible to prevent a decrease in the resonance frequency when sound that has passed through the sound hole 101b collides with the deformation suppression portion 90 and vibrates the vibration region 22. Furthermore, the decrease in the resonance frequency makes it possible to suppress a decrease in sensitivity in the high frequency band.

[0103] Furthermore, according to the above embodiment, the following effects can be obtained.

[0104] (1) In the above embodiment, the shape of the cylindrical suppression portion 92 of the deformation suppression portion 90 is set so that the sound hole inertance L1 is larger than the suppression inertance L2.

[0105] This makes it possible to make the acoustic inertance of the piezoelectric device 10S closer to the acoustic inertance when the deformation suppression section 90 is not provided on the piezoelectric element 1. As a result, it is possible to suppress a decrease in the resonance frequency of the vibrating region 22 that would otherwise be caused by providing the deformation suppression section 90, and to suppress a decrease in sensitivity in the high frequency band.

[0106] (2) In the above embodiment, the substrate through-hole 111 has a rectangular cross-sectional shape perpendicular to the stacking direction D1 and includes a first hole corner 112a, a second hole corner 112b, a third hole corner 112c, and a fourth hole corner 112d on the inside. The sound hole 101b has a circular cross-sectional shape perpendicular to the stacking direction D1. The deformation suppression section 90 includes four linear suppression sections 91 formed by extending linearly from the first hole corner 112a, the second hole corner 112b, the third hole corner 112c, and the fourth hole corner 112d toward the opposing hole corner, and a cylindrical suppression section 92 to which each of the four linear suppression sections 91 is connected and which is formed cylindrically so as to surround the periphery of the sound hole 101b when viewed in a direction perpendicular to the stacking direction D1.

[0107] This allows the rigidity of the support substrate 11 to be relatively high, and also makes it possible to easily achieve a configuration in which the deformation suppression portion 90 and the sound hole 101b do not overlap in the stacking direction D1.

[0108] (Modification of the second embodiment) In the above-described first embodiment, an example was described in which the deformation suppression portion 90 is composed of four linear suppression portions 91 extending from a hole corner portion 112 toward the opposing hole corner portion 112, and one cylindrical suppression portion 92 formed in a cylindrical shape, but this is not limited to this.

[0109] 19, as long as the deformation suppression portion 90 does not overlap with the sound hole 101b in the stacking direction D1. The four linear suppression portions 91 may extend from between the hole corner portions 112 and be connected to surround the sound hole 101b. In this case, the deformation suppression portion 90 may be formed in a rectangular shape made up of the four linear suppression portions 91.

[0110] (Other embodiments) Representative embodiments of the present disclosure have been described above, but the present disclosure is not limited to the above-described embodiments and can be modified in various ways, for example, as follows.

[0111] In the above embodiment, an example has been described in which the vibration section 20 has the lower-layer piezoelectric film 51, the upper-layer piezoelectric film 52, the lower-layer electrode film 61, the intermediate electrode film 62, and the upper-layer electrode film 63, but the present invention is not limited to this. The vibration section 20 may be configured to have at least one piezoelectric film 50 and one electrode film 60.

[0112] In the above embodiment, the piezoelectric element 1 is formed in a rectangular shape when viewed in a direction perpendicular to the stacking direction D1, but is not limited to this. For example, the piezoelectric element 1 may be formed in a polygonal shape such as a pentagonal or hexagonal shape when viewed in a direction perpendicular to the stacking direction D1.

[0113] In the above embodiment, an example has been described in which the vibration section 20 is divided into four vibration regions 22 by the slits 41, but this is not limiting. For example, the vibration section 20 may be divided by the slits 41 into three or fewer vibration regions 22, or five or more vibration regions 22.

[0114] In the above-described embodiment, an example has been described in which the support substrate 11 and the deformation suppression portion 90 are integrally formed, but the present invention is not limited to this. The support substrate 11 and the deformation suppression portion 90 may be configured as separate bodies and may be formed from different materials.

[0115] In the first embodiment described above, an example has been described in which the suppression portion distance 90d is smaller than the slit width 41a and the suppression portion width 90c is larger than the slit width 41a, but this is not limiting. The suppression portion distance 90d may be larger than the slit width 41a. The suppression portion width 90c may be smaller than the slit width 41a.

[0116] In the second embodiment described above, an example was described in which the shape of the cylindrical suppression portion 92 is set so that the sound hole inertance L1 is greater than the suppression inertance L2, but the present invention is not limited to this. The shape of the cylindrical suppression portion 92 of the deformation suppression portion 90 may be set so that the sound hole inertance L1 is equal to or less than the suppression inertance L2.

[0117] In the above-described embodiments, it goes without saying that the elements constituting the embodiments are not necessarily essential unless they are specifically stated as essential or are clearly considered essential in principle.

[0118] In the above-described embodiments, when numerical values ​​such as the number, values, amounts, ranges, etc. of components of the embodiments are mentioned, they are not limited to the specific numbers unless they are specifically stated as essential or are clearly limited to a specific number in principle.

[0119] In the above-described embodiments, when referring to the shapes, positional relationships, etc. of components, etc., the shapes, positional relationships, etc. are not limited to those unless otherwise specified or when they are fundamentally limited to specific shapes, positional relationships, etc. [Explanation of symbols]

[0120] 10 Support 20 Vibration unit 21a Support area 21b Floating region 90, 90a, 90b, 91, 92 Deformation suppression section 111 Opening

Claims

1. A piezoelectric element, A support (10); a vibration part (20) that is stacked on the support body along a predetermined stacking direction and vibrates when pressure is applied from the outside; a deformation suppression section (90, 90a, 90b, 91, 92) that is disposed apart from the vibration section and suppresses deformation of the support body, The vibration section has a support region (21a) supported by the support body and a floating region (21b) connected to the support region and floating above the support body, the support has an opening (111) facing the floating region and opening to the floating region; The deformation suppression portion is disposed across the opening of the piezoelectric element.

2. The vibration section has slits (41) formed therein that divide the floating area into a plurality of vibration areas (22), When a direction in which the slits extend is defined as a slit direction, the deformation suppression portion is formed to extend along the slit direction, and is disposed at a position overlapping with the slits in the stacking direction and faces the slits, When the dimension of the slit in the direction perpendicular to the slit direction and the stacking direction is defined as a slit width (41a), and the distance between the slit and the deformation suppression portion in the stacking direction is defined as a suppression portion distance (90d), at least a portion of the suppression portion distance is smaller than the slit width, 2. The piezoelectric element of claim 1, wherein when the dimension of the deformation suppression portion in a direction perpendicular to the slit direction and the stacking direction is defined as a suppression portion width (90c), at least a portion of the suppression portion width is larger than the slit width.

3. The opening has a rectangular cross section perpendicular to the stacking direction and has four opening corners (112) on the inside, The deformation suppression portion has two intersecting intersection suppression portions (90a, 90b), The four opening corners include a first opening corner (112a) and a second opening corner (112b) that are opposite to each other, and a third opening corner (112c) and a fourth opening corner (112d) that are opposite to each other; 3. The piezoelectric element of claim 1, wherein one side of the two crossing suppression portions is formed to extend across the opening from the first opening corner portion to the second opening corner portion, and the other side is formed to extend across the opening from the third opening corner portion to the fourth opening corner portion.

4. The piezoelectric element according to claim 1 ; a casing (100) having a substrate (101) on which the piezoelectric element is mounted and a lid (102) fixed to the substrate in a state in which the piezoelectric element is housed, and having a through hole (101b) formed therein that communicates with the outside and through which sound pressure is introduced; the support is disposed on the substrate; The through hole is formed to penetrate in the stacking direction and communicate with the opening, The deformation suppression portion is disposed opposite the substrate at a distance in the stacking direction and at a position not overlapping with the through hole in the stacking direction.

5. The microphone according to claim 4 , wherein the deformation suppression portion is set so that an acoustic inertance inside the through hole is greater than an acoustic inertance between the deformation suppression portion and the substrate.

6. The opening has a rectangular cross section perpendicular to the stacking direction and has four opening corners (112) on the inside, The through hole has a circular cross section perpendicular to the stacking direction, The microphone of claim 4 or 5, wherein the deformation suppression portion includes four linear suppression portions (91) formed by extending linearly from each of the four opening corner portions toward the opposing opening corner portion, and a cylindrical suppression portion (92) to which each of the four linear suppression portions is connected and which is formed cylindrically so as to surround the periphery of the through hole when viewed in a direction perpendicular to the stacking direction.

Images