Piezoelectric elements, piezoelectric devices

Abstract

To improve the detection accuracy.SOLUTION: A piezoelectric element includes a supporter 10, and a vibration part 20 disposed on the supporter 10 and including a piezoelectric film 50 and an electrode film 60 connected to the piezoelectric film 50 and extracting charges generated by deformation of the piezoelectric film 50, including a support region 21a supported by the supporter and a vibration region 22 connected to the support region 21a and floating from the supporter 10, and outputting a pressure detection signal based on the charges. The vibration region 22 has a plurality of slits formed from the support region 21a side toward a central part C in the vibration region 22, and is supported on both sides with respect to the support region 21a. A base film 70 is provided between the supporter 10 and the piezoelectric film 50.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] The present invention relates to a piezoelectric element and a piezoelectric device having a vibration region. [Background technology]

[0002] Piezoelectric elements having a vibration region have been proposed in the past (see, for example, Patent Document 1). Specifically, the vibration region of this piezoelectric element has a piezoelectric film and an electrode film connected to the piezoelectric film, and is cantilevered. In such a piezoelectric element, when the vibration region vibrates due to acoustic pressure (hereinafter simply referred to as sound pressure), the piezoelectric film is deformed and an electric charge is generated in the piezoelectric film. Therefore, the sound pressure applied to the vibration region can be detected by extracting the electric charge generated in the piezoelectric film via the electrode film. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5936154 Summary of the Invention [Problem to be solved by the invention]

[0004] However, there is a demand for improved detection accuracy in the above-described piezoelectric elements.

[0005] In view of the above, an object of the present invention is to provide a piezoelectric element and a piezoelectric device that can improve detection accuracy. [Means for solving the problem]

[0006] Claim 1 for achieving the above object provides a piezoelectric element having a vibration section (20) that outputs a pressure detection signal according to pressure, the vibration section including a support (10), a piezoelectric film (50) disposed on the support, and an electrode film (60) connected to the piezoelectric film and configured to extract an electric charge generated by deformation of the piezoelectric film, the vibration section having a support region (21a) supported by the support, and a vibration region (22) connected to the support region and floating above the support, the vibration region outputting a pressure detection signal based on the electric charge, the vibration region having a plurality of slits (40-44) formed from the support region side toward a center (C) of the vibration region, and supported at both ends by the support region, and a base film (70) is provided between the support and the piezoelectric film. The slit is formed so that a tapered portion (45) having a width that narrows from the one surface side toward the other surface side is formed, where the surface of the vibration region opposite the support is one surface (22a) and the surface of the vibration region on the support side is the other surface (22b). .

[0007] This allows the resonant frequency to be increased compared to when the vibration region is cantilevered, thereby broadening the frequency range over which detection sensitivity can be maintained and improving detection accuracy.

[0008] Also, claims 4 A piezoelectric device having a piezoelectric element having a vibration part (20) that outputs a pressure detection signal according to pressure, or one of three the piezoelectric element described above, a mounting member (101) on which the piezoelectric element is mounted, and a lid portion (102) fixed to the mounting member while accommodating the piezoelectric element, and a casing (100) having a through hole (101b) formed therein that communicates with the outside and through which pressure is introduced, and the slit is formed in a part of the vibration area different from the part facing the through hole.

[0009] According to this, since the piezoelectric element capable of increasing the resonance frequency is provided, the frequency range over which detection sensitivity can be maintained can be widened, and detection accuracy can be improved.

[0010] 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]

[0011] [Figure 1A] FIG. 2 is a cross-sectional view of the piezoelectric element according to the first embodiment. [Figure 1B] FIG. 2 is a cross-sectional view of the piezoelectric element according to the first embodiment. [Figure 1C] FIG. 2 is a cross-sectional view of the piezoelectric element according to the first embodiment. [Figure 2A] FIG. 2 is a plan view of the piezoelectric element according to the first embodiment. [Figure 2B] FIG. 3 is a plan view of an electrode film formed in a first region in the first embodiment. [Figure 3] FIG. 2 is a circuit schematic diagram of a piezoelectric element according to the first embodiment. [Figure 4A] This is a method for manufacturing the piezoelectric element shown in FIG. 1C. [Figure 4B] This is a method of manufacturing a piezoelectric element following FIG. 4A. [Figure 4C] This is a method of manufacturing a piezoelectric element following FIG. 4B. [Figure 5] 1 is a cross-sectional view of a piezoelectric device according to a first embodiment. [Figure 6] FIG. 10 is a diagram showing the relationship between the connection length and the resonance frequency of the piezoelectric element. [Figure 7] FIG. 10 is a diagram showing the relationship between the frequency applied to the vibration region and the output signal. [Figure 8] FIG. 10 is a diagram showing the relationship between the connection length and the generated stress ratio. [Figure 9] FIG. 10 is a diagram illustrating the relationship between sound pressure and output signal. [Figure 10A] FIG. 4 is a plan view of a piezoelectric element according to a modified example of the first embodiment. [Figure 10B] FIG. 4 is a plan view of a piezoelectric element according to a modified example of the first embodiment. [Figure 11A] FIG. 10 is a plan view of a vibration region in a modified example of the first embodiment. [Figure 11B] FIG. 10 is a plan view of a vibration region in a modified example of the first embodiment. [Figure 11C] FIG. 10 is a plan view of a vibration region in a modified example of the first embodiment. [Figure 11D]FIG. 10 is a plan view of a vibration region in a modified example of the first embodiment. [Figure 11E] FIG. 10 is a plan view of a vibration region in a modified example of the first embodiment. [Figure 11F] FIG. 10 is a plan view of a vibration region in a modified example of the first embodiment. [Figure 11G] FIG. 10 is a plan view of a vibration region in a modified example of the first embodiment. [Figure 12] FIG. 10 is a plan view of an electrode film formed in a first region in a modified example of the first embodiment. [Figure 13] 13 is a circuit schematic diagram of a piezoelectric element having the electrode film shown in FIG. 12. [Figure 14] FIG. 10 is a plan view of a piezoelectric element according to a second embodiment. [Figure 15] FIG. 10 is a schematic diagram of a vibration region described in a third embodiment. [Figure 16] FIG. 10 is a schematic diagram showing the magnitude of the bending moment in the vibration region. [Figure 17] FIG. 10 is a diagram showing stress distribution in a vibration region. [Figure 18] FIG. 10 is a plan view of a piezoelectric element according to a third embodiment. [Figure 19] FIG. 19 is a circuit schematic diagram of the piezoelectric element shown in FIG. [Figure 20] FIG. 10 is a cross-sectional view of a piezoelectric element according to a fourth embodiment. [Figure 21] FIG. 21 is a plan view of the piezoelectric element shown in FIG. [Figure 22] FIG. 10 is a cross-sectional view of a piezoelectric element according to a fifth embodiment. [Figure 23] FIG. 23 is a plan view of the piezoelectric element shown in FIG. 22. [Figure 24A] FIG. 13 is a plan view of a piezoelectric element according to a sixth embodiment. [Figure 24B] FIG. 13 is a plan view of an electrode film formed in a first region in the sixth embodiment. [Figure 25] FIG. 13 is a circuit schematic diagram of a piezoelectric element according to a sixth embodiment. [Figure 26] FIG. 10 is a cross-sectional view of a piezoelectric element according to a sixth embodiment. [Figure 27]FIG. 13 is a plan view of a piezoelectric element in a modified example of the sixth embodiment. [Figure 28] FIG. 20 is a plan view of an electrode film formed in a first region in a modified example of the sixth embodiment. [Figure 29] FIG. 13 is a circuit schematic diagram of a piezoelectric element in a modified example of the sixth embodiment. [Figure 30] FIG. 13 is a plan view of a piezoelectric element according to a seventh embodiment. [Figure 31] FIG. 12 is a cross-sectional view of a piezoelectric device according to a seventh embodiment. [Figure 32] FIG. 13 is a cross-sectional view illustrating a piezoelectric device according to an eighth embodiment. [Figure 33] FIG. 10 is a diagram showing the relationship between the slit width, the slit length, and the acoustic resistance when the thickness of the vibration region is constant. [Figure 34] FIG. 10 is a diagram showing the relationship between the thickness of the vibration region, the slit length, and the acoustic resistance when the slit width is constant. [Figure 35] FIG. 10 is a diagram showing the relationship between the slit length and the acoustic resistance ratio. [Figure 36] FIG. 13 is a cross-sectional view of a slit of a piezoelectric element according to the ninth embodiment. [Figure 37] FIG. 10 is a diagram showing the relationship between the slit width on one surface side and acoustic resistance. [Figure 38A] FIG. 13 is a cross-sectional view of a slit of a piezoelectric element in a modified example of the ninth embodiment. [Figure 38B] FIG. 13 is a cross-sectional view of a slit of a piezoelectric element in a modified example of the ninth embodiment. [Figure 38C] FIG. 13 is a cross-sectional view of a slit of a piezoelectric element in a modified example of the ninth embodiment. [Figure 39] FIG. 23 is a plan view showing the positional relationship between a piezoelectric element and a bonding member in a tenth embodiment. [Figure 40A] FIG. 23 is a plan view showing the positional relationship between a piezoelectric element and a bonding member in a modified example of the tenth embodiment. [Figure 40B] FIG. 23 is a plan view showing the positional relationship between a piezoelectric element and a bonding member in a modified example of the tenth embodiment. [Figure 41A]FIG. 23 is a plan view showing the positional relationship between a piezoelectric element and a bonding member in a modified example of the tenth embodiment. [Figure 41B] FIG. 23 is a plan view showing the positional relationship between a piezoelectric element and a bonding member in a modified example of the tenth embodiment. [Figure 41C] FIG. 23 is a plan view showing the positional relationship between a piezoelectric element and a bonding member in a modified example of the tenth embodiment. [Figure 42] FIG. 22 is a cross-sectional view of a piezoelectric device according to an eleventh embodiment. [Figure 43] FIG. 23 is a cross-sectional view of a piezoelectric element according to a twelfth embodiment. [Figure 44A] 44A to 44C are cross-sectional views showing a manufacturing process of the piezoelectric element shown in FIG. [Figure 44B] FIG. 44B is a cross-sectional view showing the manufacturing process of the piezoelectric element subsequent to FIG. 44A. [Figure 44C] FIG. 44C is a cross-sectional view showing the manufacturing process of the piezoelectric element subsequent to FIG. 44B. [Figure 45] FIG. 44D is a schematic diagram of a portion where a slit is formed in the manufacturing process of FIG. 44C. [Figure 46] FIG. 10 is a diagram showing the relationship between frequency, sensitivity, and effective width. [Figure 47] 10 is a diagram showing the relationship between the film thickness of an etching mask material and the angle formed with respect to the film thickness of a piezoelectric film. FIG. [Figure 48] FIG. 10 is a cross-sectional view of a piezoelectric device according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following embodiments, parts that are identical or equivalent to each other will be denoted by the same reference numerals.

[0013] (First embodiment) A piezoelectric element 1 according to a first embodiment will be described with reference to FIGS. 1A, 1B, 1C, 2A, and 2B. The piezoelectric element 1 according to this embodiment is preferably used as a microphone, for example. FIG. 1A corresponds to a cross-sectional view taken along line IA-IA in FIG. 2A, FIG. 1B corresponds to a cross-sectional view taken along line IB-IB in FIG. 2A, and FIG. 1C corresponds to a cross-sectional view taken along line IC-IC in FIG. 2A. Note that FIG. 2A omits a first electrode portion 81 and a second electrode portion 82, which will be described later. Also, in the drawings corresponding to FIG. 2A, which will be described later, the first electrode portion 81 and the second electrode portion 82 are omitted as appropriate.

[0014] The piezoelectric element 1 of this embodiment includes a support 10 and a vibrating portion 20, and has a rectangular planar shape. The support 10 includes a support substrate 11 having one surface 11a and another surface 11b, and an insulating film 12 formed on the one surface 11a of the support substrate 11. 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.

[0015] The vibration section 20 constitutes the sensing section 30, which outputs a pressure detection signal corresponding to pressure such as sound pressure, and is disposed on the support 10. The support 10 is formed with a recess 10a for floating the inner edge side of the vibration section 20. Therefore, the vibration section 20 has a support region 21a disposed on the support 10, and a floating region 21b that is connected to the support region 21a and floats above the recess 10a. In this embodiment, the opening end of the recess 10a on the vibration section 20 side (hereinafter simply referred to as the opening end of the recess 10a) has a rectangular shape in plan view. Therefore, the entire floating region 21b has a rectangular shape in plan view.

[0016] Furthermore, the floating region 21b is formed with slits 40 penetrating the floating region 21b in the thickness direction. In this embodiment, first to fourth slits 41 to 44 are formed in the floating region 21b. The first to fourth slits 41 to 44 extend from each corner of the floating region 21b, which has a rectangular planar shape, toward the center C of the floating region 21b. However, the first to fourth slits 41 to 44 are formed so as not to reach the center C. In other words, the first to fourth slits 41 to 44 are formed so as not to divide the floating region 21b.

[0017] In this embodiment, the first to fourth slits 41 to 44 are formed so that the slit lengths L along the extension direction are equal to each other. Furthermore, the first to fourth slits 41 to 44 in this embodiment have a constant slit width g along the thickness direction of the vibrating region 22. The vibrating region 22 is configured by such floating region 21b, and is supported at both ends by the support region 21a.

[0018] The slit width g of the first to fourth slits 41 to 44 is the length in a direction perpendicular to the extension direction of the first to fourth slits 41 to 44 and along the surface direction of the vibrating region 22. In other words, the slit width g of the first to fourth slits 41 to 44 is the distance between the side surfaces 22c of the vibrating region 22 exposed by the first slits 41 to 44.

[0019] Hereinafter, the surface of the vibrating region 22 opposite to the support 10 will be referred to as one surface 22a of the vibrating region 22, and the surface of the vibrating region 22 facing the support 10 will be referred to as the other surface 22b of the vibrating region 22. Similarly, the surfaces of the vibrating region 22 exposed from the first to fourth slits 41 to 44 will be referred to as side surfaces 22c of the vibrating region 22. In addition, in the normal direction to the one surface 22a of the vibrating region 22, the areas surrounded by one side forming the outline of the vibrating region 22 and imaginary lines K1 and K2 extending along the slits 41 to 44 will be referred to as the first to fourth vibrating regions 221 to 224. In the following, the normal direction to the one surface 22a of the vibrating region 22 will also be simply referred to as the normal direction. In other words, "in the normal direction to the one surface 22a of the vibrating region 22" can also be referred to as when viewed from the normal direction to the one surface 22a of the vibrating region 22.

[0020] In this embodiment, a virtual line extending along the first slit 41 and the third slit 43 is referred to as a virtual line K1, and a virtual line extending along the second slit 42 and the fourth slit 44 is referred to as a virtual line K2. In the normal direction, a region of the vibration region 22 that includes a portion between the first slit 41 and the second slit 42 and is surrounded by the virtual lines K1 and K2 is referred to as a first vibration region 221. In the normal direction, a region of the vibration region 22 that includes a portion between the second slit 42 and the second slit 43 and is surrounded by the virtual lines K1 and K2 is referred to as a second vibration region 222. In the normal direction, a region of the vibration region 22 that includes a portion between the third slit 43 and the fourth slit 44 and is surrounded by the virtual lines K1 and K2 is referred to as a third vibration region 223. In the normal direction, the region of the vibration region 22 that includes the portion between the fourth slit 44 and the first slit 41 and is surrounded by the virtual lines K1 and K2 is defined as a fourth vibration region 224. The vibration region 22 of this embodiment is formed by integrating the first to fourth vibration regions 221 to 224.

[0021] 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 has a lower-layer electrode film 61 arranged below the lower-layer piezoelectric film 51, an intermediate electrode film 62 arranged between the lower-layer piezoelectric film 51 and the upper-layer piezoelectric film 52, and an upper-layer electrode film 63 arranged 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.

[0022] The lower-layer piezoelectric film 51 and the upper-layer piezoelectric film 52 are made of lead-free piezoelectric ceramics such as scandium aluminum nitride (ScAlN) and aluminum nitride (AlN). The lower-layer electrode film 61, the intermediate electrode film 62, and the upper-layer electrode film 63 are made of molybdenum, copper, platinum, titanium, etc.

[0023] 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. In this embodiment, the underlayer 70 is made of aluminum nitride or the like. The piezoelectric film 50 has a thickness of about 1 μm, and the underlayer 70 has a thickness of about several tens of nanometers. That is, the underlayer 70 is made extremely thin compared to the piezoelectric film 50.

[0024] In addition, in each vibrating region 22 of this embodiment, the portion of the vibrating region 22 on the support region 21a side, which becomes the fixed end when the vibrating region 22 vibrates, is designated as a first region R1, and the portion on the center C side is designated as a second region R2. The lower electrode film 61, intermediate electrode film 62, and upper electrode film 63 are formed in the first region R1 and the second region R2, respectively. However, the lower electrode film 61, intermediate electrode film 62, and upper electrode film 63 formed in the first region R1 are separated from the lower electrode film 61, intermediate electrode film 62, and upper electrode film 63 formed in the second region R2, and are insulated from each other. The lower electrode film 61, intermediate electrode film 62, and upper electrode film 63 formed in the first region R1 are appropriately extended to the support region 21a.

[0025] In this embodiment, the lower electrode film 61, the intermediate electrode film 62, and the upper electrode film 63 are formed so as not to reach the first to fourth slits 41 to 44. In other words, the lower electrode film 61, the intermediate electrode film 62, and the upper electrode film 63 are formed so as to terminate inside the side surface 22c of the vibrating region 22 that is exposed from the first to fourth slits 41 to 44. In other words, the lower electrode film 61, the intermediate electrode film 62, and the upper electrode film 63 are disposed inside the first to fourth slits 41 to 44 in the normal direction. Therefore, the side surface 22c of the vibrating region 22 is formed by the lower piezoelectric film 51, the upper piezoelectric film 52, and the base film 70.

[0026] A first electrode portion 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 portion 82 electrically connected to the intermediate electrode film 62 formed in the first region R1 are formed in the support region 21a of the vibration portion 20. As described above, the first electrode portion 81 and the second electrode portion 82 are omitted from the illustration in FIG. 2A.

[0027] The first electrode portion 81 has a through electrode 81b formed in a hole portion 81a that penetrates the upper-layer electrode film 63, the upper-layer piezoelectric film 52, and the lower-layer piezoelectric film 51, and electrically connected to the lower-layer electrode film 61 and the upper-layer electrode film 63. In this embodiment, the through electrode 81b is electrically connected to the lower-layer electrode film 61 and the upper-layer electrode film 63 that are formed in the first vibration region 221. The first electrode portion 81 also has a pad portion 81c formed on the through electrode 81b and electrically connected to the through electrode 81b.

[0028] The second electrode portion 82 is formed in a hole portion 82a that penetrates the upper-layer piezoelectric film 52 and exposes the intermediate electrode film 62, and has a through electrode 82b that is electrically connected to the intermediate electrode film 62. In this embodiment, the through electrode 82b is electrically connected to the intermediate electrode film 62 that is formed in the fourth vibration region 224. In addition, the second electrode portion 82 has a pad portion 82c that is formed on the through electrode 82b and is electrically connected to the through electrode 82b.

[0029] 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. The lower-layer electrode film 61, the intermediate electrode film 62, and the upper-layer electrode film 63 formed in the second region R2 are not electrically connected to the respective electrode portions 81 and 82, and are in a floating state. For this reason, the lower-layer electrode film 61, the intermediate electrode film 62, and the upper-layer 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-layer piezoelectric film 51 and the upper-layer piezoelectric film 52 located in the second region R2.

[0030] Furthermore, the lower electrode film 61, intermediate electrode film 62, and upper electrode film 63 formed in the first region R1 are divided by the first to fourth vibration regions 221 to 224. In other words, the lower electrode film 61, intermediate electrode film 62, and upper electrode film 63 formed in the first region R1 are not formed so as to straddle the first to fourth vibration regions 221 to 224. The lower electrode film 61, intermediate electrode film 62, and upper electrode film 63 formed in the first region R1 of each of the vibration regions 221 to 224 are connected via wiring films or the like (not shown).

[0031] As shown in FIG. 2B , the lower electrode film 61, intermediate electrode film 62, and upper electrode film 63 of this embodiment are formed so that the outer shapes of the portions formed in the first region R1 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, intermediate electrode film 62, and upper electrode film 63 are divided into the first to fourth vibration regions 221 to 224 as described above. Therefore, the outer shapes of the portions of the lower electrode film 61, intermediate electrode film 62, and upper electrode film 63 formed in the first region R1 here refer to shapes formed by the outer outlines of the portions of the lower electrode film 61, intermediate electrode film 62, and upper electrode film 63 located in the first region R1 and extensions of these outer outlines. Although FIG. 2B is not a cross-sectional view, the electrode film 60 formed in the first region R1 is hatched for ease of understanding. Furthermore, although FIG. 2B shows an electrode film 60, the lower electrode film 61, intermediate electrode film 62, and upper electrode film 63 that make up the electrode film 60 each have the same shape as the electrode film 60 in FIG. 2B in the first region R1.

[0032] The piezoelectric element 1 of this embodiment is configured to output a change in charge in the first to fourth vibration regions 221 to 224 as a single pressure detection signal. Specifically, each of the vibration regions 221 to 224 has a bimorph structure, and as shown in FIG. 3, 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. The piezoelectric element 1 outputs the potential difference between the first electrode portion 81 and the second electrode portion 82 as a pressure detection signal. In this case, for example, the second electrode portion 82 is connected to ground, and the piezoelectric element 1 outputs the potential difference between the ground and the first electrode portion 81 as a pressure detection signal.

[0033] Next, a manufacturing method for such a piezoelectric element 1 will be briefly described with reference to Figures 4A, 4B, and 4C. Figures 4A to 4C are cross-sectional views of a portion corresponding to Figure 1C.

[0034] First, as shown in FIG. 4A, a support 10 having a support substrate 11 and an insulating film 12 is prepared, on which a base film 70, a piezoelectric film 50, an electrode film 60, a first electrode portion 81, a second electrode portion 82, and the like are formed. In other words, a piezoelectric element 1 shown in FIG. 1C is prepared without the recess 10a and the first to fourth slits 41 to 44. The piezoelectric film 50 and the electrode film 60 formed in the process of FIG. A constitute the vibrating portion 20. For this reason, in FIG. 4A, the same reference numerals are used as the one surface 22a and the other surface 22b of the vibrating region 22. The first electrode portion 81 and the second electrode portion 82 are formed on a cross section different from that shown in FIG. 4A.

[0035] Here, the base film 70, the piezoelectric film 50, the electrode film 60, and the like are formed by appropriate general sputtering, etching, and the like. In this case, when the base film 70 and the lower electrode film 61 serving as the electrode film 60 are formed on the support 10, the base film 70 and the lower electrode film 61 are formed in a state in which tensile stress remains because the linear expansion coefficients of the base film 70 and the lower electrode film 61 are greater than the linear expansion coefficient of the support 10. Therefore, if the piezoelectric film 50 is formed without any further processing, the piezoelectric film 50 is likely to be formed in a state in which tensile stress resulting from the tensile stress of the base film 70 and the lower electrode film 61 remains. Furthermore, if tensile stress remains in the piezoelectric film 50, the characteristics of the piezoelectric element 1 are likely to fluctuate. Therefore, when forming the piezoelectric film 50, it is preferable to, for example, do the following.

[0036] For example, when forming the upper-layer piezoelectric film 52, it is preferable to apply a higher voltage during sputtering than when forming the lower-layer piezoelectric film 51, so that compressive stress is generated in the upper-layer piezoelectric film 52. This cancels out the tensile stress of the lower-layer piezoelectric film 51 and the compressive stress of the upper-layer piezoelectric film 52, thereby reducing the stress remaining inside the piezoelectric film 50 as a whole. In this case, the upper-layer piezoelectric film 52 may be formed by multiple sputtering operations. Then, tensile stress may be generated in the portion of the upper-layer piezoelectric film 52 facing the lower-layer piezoelectric film 51, and compressive stress may be generated in the uppermost portion opposite the lower-layer piezoelectric film 51, thereby reducing the stress remaining inside the piezoelectric film 50.

[0037] Next, as shown in FIG. 4B, anisotropic dry etching is performed using a mask (not shown) to form first to fourth slits 41 to 44 that penetrate the piezoelectric film 50 and reach the support 10. This forms a vibration region component 220 that will become the vibration region 22 when a recess 10a (described later) is formed. The second and third slits 43 and 44 are formed on a cross section different from that shown in FIG. 4B. The vibration region component 220 is a portion that will become the vibration region 22 when the recess 10a is formed. For this reason, in the drawing, the same reference numerals are assigned to one surface, the other surface, and side surfaces of the vibration region component 220 as to one surface 22a, the other surface 22b, and side surface 22c of the vibration region 22.

[0038] 4C, using a mask (not shown), etching is performed from the other surface 11b of the support substrate 11 through the insulating film 12 to reach the base film 70, forming the recess 10a. In this embodiment, the support substrate 11 is removed by anisotropic dry etching, and then the insulating film 12 is removed by isotropic wet etching to form the recess 10a. As a result, the vibrating region component 220 is suspended from the support 10, forming the vibrating region 22, and the piezoelectric element 1 shown in FIG. 1 is manufactured.

[0039] In this step, although not shown, the recess 10a may be formed by arranging a protective resist or the like that covers the upper piezoelectric film 52 and the upper electrode film 63. This makes it possible to prevent the vibration region 22 from being damaged when the recess 10a is formed. However, the protective resist is removed after the recess 10a is formed.

[0040] The above is the configuration of the piezoelectric element 1 in this embodiment. Next, a piezoelectric device S10 using such a piezoelectric element 1 will be described.

[0041] 5, the piezoelectric device of this embodiment is configured by housing a piezoelectric element 1 in a casing 100. The casing 100 has a printed circuit board 101 on which the piezoelectric element 1 and a circuit board 110 that performs predetermined signal processing and the like 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 110. In this embodiment, the printed circuit board 101 corresponds to a mounted member.

[0042] Although not shown, the printed circuit board 101 is configured to have wiring portions and through-hole electrodes appropriately formed thereon, and also has electronic components such as capacitors (not shown) mounted thereon as needed. The piezoelectric element 1 is mounted on one surface 101a of the printed circuit board 101 via a bonding member 2 such as an adhesive on the other surface 11b of the support substrate 11. The circuit board 110 is mounted on the one surface 101a of the printed circuit board 101 via a bonding member 111 made of a conductive material. The pad portion 81c of the piezoelectric element 1 and the circuit board 110 are electrically connected via a bonding wire 120. Note that the pad portion 82c of the piezoelectric element 1 is electrically connected to the circuit board 110 via the bonding wire 120 in a cross section different from that of FIG. 5. The lid portion 102 is made of metal, plastic, resin, or the like, and is fixed to the printed circuit board 101 via a bonding member such as an adhesive (not shown) so as to accommodate the piezoelectric element 1 and the circuit board 110.

[0043] In this embodiment, a through-hole 101b communicating with the external space is formed in a portion of the printed circuit board 101 facing the sensing unit 30. Specifically, the through-hole 101b is substantially cylindrical, and is formed so that its central axis coincides with the center C of the vibration region 22 in the normal direction.

[0044] The above is the configuration of the piezoelectric device S10 in this embodiment. Hereinafter, the space within the casing 100 between the portion where the through 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 40. 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 affects the pressure on the surface of the vibration region 22 that faces the through hole 101b formed in the casing 100 (i.e., the other surface 22b in this embodiment). The back space S2 can also be said to be a space that affects the pressure on the surface of the vibration region 22 that faces the through hole 101b formed in the casing 100 (i.e., the one surface 22a in this embodiment).

[0045] Next, the operation and effects of the piezoelectric device S10 will be described.

[0046] In the piezoelectric device S10 of this embodiment, when sound pressure as pressure is introduced into the pressure-receiving surface space S1 and the sound pressure is applied to the vibration region 22 (i.e., the sensing unit 30), the vibration region 22 vibrates. Then, electric charges are generated in the lower-layer piezoelectric film 51 and the upper-layer piezoelectric film 52 based on stress corresponding to the displacement of the vibration region 22. Therefore, in such a piezoelectric device S10, the sound pressure is detected by extracting the electric charges from the first electrode portion 81 and the second electrode portion 82.

[0047] At this time, the stress generated in the vibration region 22 (i.e., the piezoelectric film 50) is likely to be greater on the fixed end side where the vibration region 22 is supported than in the center C. For this reason, in the piezoelectric element 1 of this embodiment, as described above, the vibration region 22 is divided into a first region R1 where the stress is likely to be greater and a second region R2 where the stress is likely to be smaller. 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 and second electrode portions 81 and 82, respectively, so that the charges generated in the lower piezoelectric film 51 and the upper piezoelectric film 52 located in the first region R1 can be extracted. This makes it possible to suppress the influence of noise from becoming too large.

[0048] Here, the resonant frequency f of the vibration region 22 in the piezoelectric element 1 (hereinafter also simply referred to as the resonant frequency f of the piezoelectric element 1) depends on the spring constant k of the vibration region 22 that forms a beam and the mass m of the vibration region 22, and is expressed by the following formula 1.

[0049]

number

[0050] 2A, the length between the first slit 41 and the center C of the vibrating region 22 is defined as a first length X, and the length between the second slit 42 and the center C of the vibrating region 22 is defined as a second length Y. In this embodiment, since the slit lengths L of the first to fourth slits 41 to 44 are equal as described above, the first length X and the second length Y are equal. If the sum of the first length X and the second length Y is defined as the connection length (i.e., X+Y), the relationship between the connection length and the resonant frequency f is shown in FIG.

[0051] Specifically, when the vibrating region 22 is supported at both ends, the spring constant (i.e., rigidity) increases as the connection length increases, resulting in a higher resonant frequency f compared to when the vibrating region 22 is supported at one end. Therefore, as shown in FIG. 7, adjusting the connection length can raise the resonant frequency f above 20,000 Hz (i.e., 20 kHz), which is the audible range. In other words, adjusting the connection length can cause the resonant frequency f to exist at a frequency higher than the frequency at which the output signal becomes +3 dB, relative to the reference output signal (i.e., 0 dB) at a frequency of 1,000 Hz (i.e., 1 kHz). This broadens the frequency range over which detection sensitivity can be maintained. However, since the thickness of the piezoelectric film 50 of the vibrating region 22 of this embodiment is approximately 1 μm, the resonant frequency f saturates at approximately 22.5 kHz when the connection length is approximately 300 μm. In addition, by making it possible for the low-frequency roll-off frequency to exist at frequencies where the output signal is smaller than -3 dB, the frequency range over which detection sensitivity can be maintained can be further widened. This low-frequency roll-off frequency will be specifically described in the eighth embodiment described later.

[0052] On the other hand, as shown in FIG. 8, the longer the connection length, the greater the spring constant, making it more difficult for the vibrating region 22 to deform, resulting in a smaller generated stress ratio. In other words, the longer the connection length, the lower the sensitivity. In this case, as shown in FIG. 9, assuming that the frequency of the input sound pressure is constant, the AOP (Acoustic Over Point) can be increased by lowering the sensitivity. Therefore, it is preferable to adjust the connection length according to the intended use. Note that the generated stress ratio in FIG. 8 is based on the stress generated at the boundary between the vibrating region 22 and the support region 21a when the vibrating region 22 is cantilevered. The generated stress ratio indicates the ratio of the stress generated at the boundary between the vibrating region 22 and the support region 21a when the vibrating region 22 is supported at both ends to the reference stress.

[0053] According to the present embodiment described above, the vibrating region 22 of the piezoelectric element 1 is supported at both ends. This allows the resonant frequency f to be higher than when the vibrating region 22 is supported at one end. This allows the frequency range over which detection sensitivity can be maintained to be broadened, thereby improving detection accuracy.

[0054] (1) In this embodiment, the resonant frequency f of the piezoelectric element 1 can be set to 20 kHz or higher. Therefore, with such a piezoelectric element 1, the resonant frequency f can be set outside the audible range, and the frequency range over which detection sensitivity can be maintained in the audible range can be widened.

[0055] (Modification of the first embodiment) A modification of the first embodiment will be described. As described above, it is preferable that the connection length be adjusted appropriately depending on the application and its relationship with detection sensitivity. In this case, as shown in FIG. 10A, the first slit 41 and the third slit 43 may have a different slit length L from the second slit 42 and the fourth slit 44. The first length X and the second length Y do not have to be the same distance, and the first length X may be shorter than the second length Y. Although not particularly shown, the first length X and the second length Y may have a longer length than the second length Y.

[0056] 10B, the first to fourth slits 41 to 44 may be formed only in the first region R1 of the vibration region 22. Although not particularly shown, the first to fourth slits 41 to 44 may be formed so that their slit lengths L are different from one another.

[0057] In this way, in the piezoelectric element 1 of this embodiment, the slit lengths L of the first to fourth slits 41 to 44 can be changed as appropriate, and can be changed according to the product in which it is to be mounted. Therefore, the piezoelectric element 1 of this embodiment can also improve the selectivity of the product in which it is to be mounted.

[0058] The planar shape of the vibrating region 22 can be changed as appropriate. For example, as shown in FIGS. 11A to 11G, the planar shape of the vibrating region 22 may be a hexagon, octagon, decagon, dodecagon, tetragon, hexagon, or circle. Although not specifically shown, the vibrating region 22 may also be another polygonal shape. Although the slits 40 formed in the vibrating region 22 are omitted in FIGS. 11A to 11G, the vibrating region 22 actually has slits 40 formed therein. For example, when the planar shape of the vibrating region 22 is hexagonal as shown in FIG. 11A, six slits 40 are formed from each corner of the vibrating region 22's outer shape toward the center C. When the planar shape of the vibrating region 22 is circular as shown in FIG. 11G, a desired number of slits 40 are formed evenly in the circumferential direction.

[0059] Furthermore, as shown in FIG. 12, the electrode film 60 may be divided into a plurality of charge regions 60a in the first region R1. For example, the electrode film 60 may be divided into three charge regions 60a in the first region R1 of each of the vibration regions 221 to 224. The lower electrode film 61, intermediate electrode film 62, and upper electrode film 63 that make up the electrode film 60 are each divided into charge regions 60a in the first region R1 as shown in FIG. 12. In this case, as shown in FIG. 13, the piezoelectric element 1 is in a state where the capacitances formed by the divided charge regions 60a are connected in series. This allows the capacitance in each of the vibration regions 221 to 224 to be reduced, thereby improving output. In other words, the detection sensitivity can be improved.

[0060] (Second embodiment) A second embodiment will be described. This embodiment is different from the first embodiment in that the shapes of the first to fourth slits 41 to 44 are changed. As the rest of the configuration is the same as the first embodiment, a description thereof will be omitted here.

[0061] In the piezoelectric element 1 of this embodiment, as shown in FIG. 14, the first to fourth slits 41 to 44 are tapered in the normal direction such that the slit width g narrows toward the center C.

[0062] According to the present embodiment described above, the vibrating region 22 is supported at both ends, which makes it possible to increase the resonance frequency f of the piezoelectric element 1 and to obtain the same effects as those of the first embodiment.

[0063] (1) In this embodiment, the first to fourth slits 41 to 44 are tapered such that the slit width g narrows toward the center C of the vibrating region 22. Therefore, when sound pressure is applied to the vibrating region 22 and the vibrating region 22 bends, the slit widths g of the first to fourth slits 41 to 44 in the bent state tend to become uniform. In other words, when the vibrating region 22 bends, the slit widths g of the first to fourth slits 41 to 44 tend to become uniform in the normal direction between the portion on the support region 21a side and the portion on the center C side. Therefore, differences in the ease with which local sound pressure escapes within the first to fourth slits 41 to 44 are less likely to occur, and noise can be reduced. This further improves detection accuracy.

[0064] (Third embodiment) A third embodiment will now be described. This embodiment differs from the first embodiment in that the method of dividing the first region R1 and the second region R2 is changed. As the rest of the configuration is the same as the first embodiment, a description thereof will be omitted here.

[0065] The piezoelectric element 1 of this embodiment has the same configuration as the first embodiment, and the vibrating region 22 is supported at both ends. Assume that sound pressure is applied from the other surface 22b of the vibrating region 22, as shown in FIG. 15 . In this case, as shown in FIG. 16 , a maximum bending moment Mmax occurs in the vibrating region 22 on the support region 21a side, and a large bending moment also occurs in the center C. Note that, as shown in FIG. 17 , opposite stresses occur in the lower-layer piezoelectric film 51 and the upper-layer piezoelectric film 52 of the piezoelectric film 50. Furthermore, opposite stresses occur in the outer edge portion of the piezoelectric film 50 on the support region 21 side and the inner edge portion on the center C side. That is, opposite stresses occur in the piezoelectric film 50 in the portion located in the first region R1 and the portion located on the center C side.

[0066] 18, in this embodiment, the central region 225 including the center C of the vibrating region 22 and its peripheral region is also defined as the first region R1, and the charge of this central region 225 is also extracted. Note that the central region 225 can also be said to be a region configured by the regions on the central region C side of the first to fourth vibrating regions 221 to 224.

[0067] Specifically, in this embodiment, as shown in FIG. 19 , the electric charge in the central region 225 is combined with the electric charges in the first to fourth vibration regions 221 to 224 and output. More specifically, in addition to the first electrode portion 81 and the second electrode portion 82, the piezoelectric element 1 of this embodiment is formed with a third electrode portion 83 and a fourth electrode portion 84. In the central region 225, the lower electrode film 61 and the upper electrode film 63 are electrically connected to the third electrode portion 83, and the intermediate electrode film 62 is connected to the fourth electrode portion 84. The fourth electrode portion 82 connected to the intermediate electrode film 62 is connected to, for example, ground, similar to the second electrode portion 82. Opposite stresses are generated in the piezoelectric film 50 in a portion located in the first region R1 and a portion located in the central region 225. Therefore, the piezoelectric element 1 outputs the difference between the output based on the potential difference between the first electrode portion 81 and the second electrode portion 82 and the output based on the potential difference between the third electrode portion 83 and the fourth electrode portion 84 as the overall pressure detection signal.

[0068] According to the present embodiment described above, the vibrating region 22 is supported at both ends, which makes it possible to increase the resonance frequency f of the piezoelectric element 1 and to obtain the same effects as those of the first embodiment.

[0069] (1) In this embodiment, the charge is also extracted from the central region 225 of the vibration region 22. This makes it possible to improve the detection sensitivity.

[0070] (Fourth embodiment) A fourth embodiment will be described. This embodiment is different from the first embodiment in that the configuration of the vibration region 22 is changed. As the rest is the same as the first embodiment, a description thereof will be omitted here.

[0071] In the piezoelectric element 1 of this embodiment, as shown in FIGS. 20 and 21, the first to fourth slits 41 to 44 extend to the center C of the vibration region 22. That is, the first to fourth slits 41 to 44 are formed so as to intersect at the center C. Therefore, the first to fourth vibration regions 221 to 224 are partitioned by the first to fourth slits 41 to 44. Note that FIG. 20 corresponds to a cross-sectional view taken along line XX-XX in FIG. 21. Also, although FIG. 21 is not a cross-sectional view, a connecting member 90, which will be described later, is hatched to facilitate understanding.

[0072] In this embodiment, a connecting member 90 is embedded in and near the center C of the first to fourth slits 41 to 44. In this embodiment, the first to fourth vibrating regions 221 to 224 are integrated by this connecting member 90, and the vibrating region 22 is supported at both ends by the support region 21a. The connecting member 90 in this embodiment is made of a material with lower rigidity than the piezoelectric film 50, and is made, for example, of a material made by mixing an ionic liquid with a polyimide component and hardening it through heat treatment at about 150°C. Note that an ionic liquid is a liquid salt compound composed only of ions (i.e., anions and cations).

[0073] Such a piezoelectric element 1 is manufactured, for example, as follows. That is, when the first to fourth slits 41 to 44 are formed in the step of FIG. 4B, the first to fourth slits 41 to 44 are made to intersect at the center C of the vibrating region 22. Thereafter, photoresist or the like is disposed so as to cover the upper electrode film 63, etc., and the photoresist is patterned so as to form openings in the portions where the connecting members 90 are to be disposed. Next, the connecting members 90 are embedded in the first to fourth slits 41 to 44 by a method such as spin coating, and are then hardened by a heat treatment. Subsequently, lift-off is performed to remove the photoresist, so that the connecting members 90 are disposed in the first to fourth slits 41 to 44. Thereafter, the step of FIG. 4C is performed to manufacture the piezoelectric element 1 shown in FIGS. 20 and 21.

[0074] According to the present embodiment described above, the vibrating region 22 is supported at both ends, which makes it possible to increase the resonance frequency f of the piezoelectric element 1 and to obtain the same effects as those of the first embodiment.

[0075] (1) As in this embodiment, the vibrating region 22 may be supported at both ends by the connecting member 90.

[0076] (2) In this embodiment, the connecting member 90 is made of a material that is less rigid than the piezoelectric film 50. Therefore, the influence of the connecting member 90 on the detection sensitivity of the piezoelectric element 1 can be suppressed.

[0077] (Fifth embodiment) A fifth embodiment will be described. This embodiment is different from the fourth embodiment in that the configuration of the vibration region 22 is changed. As the rest is the same as the fourth embodiment, a description thereof will be omitted here.

[0078] In the piezoelectric element 1 of this embodiment, as shown in Figures 22 and 23, no connecting members 90 are arranged in the first to fourth slits 41 to 44, and a connecting member 91 is arranged on one surface 22a of the vibration region 22. Note that Figure 22 corresponds to a cross-sectional view taken along line XXII-XXII in Figure 23. Although Figure 23 is not a cross-sectional view, a connecting member 91, which will be described later, is hatched to facilitate understanding.

[0079] Specifically, the connecting member 91 is arranged on one surface 22a of the vibrating region 22 so as to cover (i.e., straddle) the center C and the surrounding areas of the first to fourth slits 41 to 44. In this embodiment, the first to fourth vibrating regions 221 to 224 are integrated in this manner, and the vibrating region 22 is supported at both ends by the support region 21a. The connecting member 91 is made of a material with lower rigidity than the piezoelectric film 50, such as polyimide. More specifically, the connecting member 91 is made of polydimethylsiloxane (i.e., PDMS) or the like.

[0080] Such a piezoelectric element 1 is manufactured, for example, as follows. That is, after the first to fourth slits 41 to 44 are formed so as to intersect at the center C of the vibration region 22, the connecting member 91 is arranged by a method such as spin coating. In this embodiment, the viscosity of the connecting member 91 is adjusted so that the connecting member 91 does not get into the first to fourth slits 41 to 44 when the spin coating method is performed. Next, the connecting member 91 is patterned using a photoresist. Thereafter, the step of FIG. 4C is performed to manufacture the piezoelectric element 1 shown in FIGS. 22 and 23.

[0081] According to the present embodiment described above, the vibrating region 22 is supported at both ends, which makes it possible to increase the resonance frequency f of the piezoelectric element 1 and to obtain the same effects as those of the first embodiment.

[0082] (1) As in this embodiment, the vibrating region 22 may be supported at both ends by the connecting member 91.

[0083] (2) In this embodiment, the connecting member 91 is made of a material that is less rigid than the piezoelectric film 50, and therefore, the same effects as those of the fourth embodiment can be obtained.

[0084] (Sixth embodiment) In this embodiment, the shapes of the vibration region 22 and the intermediate electrode film 62 are adjusted compared to the first embodiment. As the rest is the same as the first embodiment, a description thereof will be omitted here.

[0085] The piezoelectric element 1 of this embodiment will be described with reference to Fig. 24A and Fig. 24B. Note that the slits 40 are omitted in Fig. 22. However, the slits 40 actually extend from each corner of the planar shape of the vibrating region 22 toward the center C, similar to the first embodiment.

[0086] As shown in FIG. 24A, the vibrating region 22 has an outer shape of a regular octagon in the normal direction. That is, the opening of the recess 10a of the support body 10 has an octagonal shape. The reason why the vibrating region 22 has an octagonal shape will be explained below. As described above, in this embodiment, the support substrate 11 is made of silicon. Therefore, by making the opening of the recess 10a have an octagonal shape (i.e., the outer shape of the vibrating region 22), it is possible to prevent strain from concentrating in a local area at the opening end of the recess 10a in the support substrate 11 (i.e., the outer end of the vibrating region 22). Therefore, it is possible to prevent strain from concentrating in a local area at the boundary between the vibrating region 22 and the support region 21a.

[0087] Furthermore, as shown in FIG. 24B, the electrode film 60 of this embodiment has a regular octagonal outer shape in the normal direction at the portion formed in the first region R1. That is, the electrode film 60 is formed in the first region so that its outer edge substantially coincides with the opening edge of the recess 10a. The electrode film 60 is separated from the portion formed in the first region R1 by electrode film slits 60b, which are different from the slits 40. Specifically, six electrode film slits 60b are formed, and a virtual shape KS (hereinafter simply referred to as a virtual shape) formed by connecting predetermined points within each electrode film slit 60b is formed to be hexagonal. More specifically, the electrode film slits 60b are formed so that a virtual shape KS formed by connecting points where each electrode film slit 60b and the outer shape of the electrode film 60 intersect is also hexagonal.

[0088] Here, the outline of the portion of the electrode film 60 located in the first region R1 refers to the shape formed by the outline of the portion of the electrode film 60 located in the first region R1 and the extension of that outline, as described above.

[0089] The reason why the virtual shape KS of the electrode film 60 is hexagonal is explained below. As described above, the electrode film 60 and the piezoelectric film 50 are stacked and arranged in the following order: lower-layer electrode film 61, lower-layer piezoelectric film 51, intermediate electrode film 62, upper-layer piezoelectric film 52, and upper-layer electrode film 63. When forming the lower-layer electrode film 61, intermediate electrode film 62, and upper-layer electrode film 63, a metal film is deposited and then patterned into a desired shape by dry etching using a mask. Although a mask is used, there is a possibility that the underlying lower-layer piezoelectric film 51 and upper-layer piezoelectric film 52 may be etched. In this case, if the piezoelectric film 50 is made of ScAlN, AlN, or the like, it has a hexagonal crystal structure. Therefore, by making the virtual shape KS of the electrode film 60 hexagonal, it is possible to prevent the crystallinity of the piezoelectric film 50 from being destroyed when the surface of the piezoelectric film 50 is etched. In other words, by matching the portion where the electrode film slits 60b are formed to the crystal structure of the piezoelectric film 50, it is possible to prevent fluctuations in the characteristics of the piezoelectric film 50.

[0090] 25, the piezoelectric element 1 of this embodiment has capacitances connected between the electrode films 61 to 63. In this embodiment, as described above, the electrode film 60 is divided into six by electrode film slits 60b that are separate from the slits 40. Therefore, the piezoelectric element 1 of this embodiment has six divided regions 226, and outputs a pressure detection signal based on the capacitance of each region 226.

[0091] In this embodiment, the electrode films 60 are separated by the electrode film slits 60b, as described above, and are not separated by the slits 40. Therefore, as shown in FIG. 26, the electrode films 60 are connected where the slits 40 are formed. Such a piezoelectric element 1 can be manufactured, for example, by forming the slits 40 or the electrode film slits 60b for each film when performing the steps shown in FIGS. 4A and 4B. For example, after forming the base film 70, a metal film is formed on the base film 70. Then, the electrode film slits 60b are formed when the metal film is patterned to form the lower-layer electrode film 61. Thereafter, the lower-layer piezoelectric film 51 is formed on the lower-layer electrode film 61. Before forming the intermediate electrode film 62, the slits 40 that penetrate only the lower-layer piezoelectric film 51 are formed in the lower-layer piezoelectric film 51. The intermediate electrode film 62, the upper-layer piezoelectric film 52, and the upper-layer electrode film 63 are then similarly formed to manufacture the piezoelectric element 1 of this embodiment.

[0092] Furthermore, in practice, the electrode film 60 of this embodiment has an outer edge portion opposite the center portion C that extends to the outside of the first region R1, and an inner edge portion that extends to the inside of the second region R2. Therefore, when forming a metal film and then patterning the metal film into a desired shape to form the intermediate electrode film 62 and the upper electrode film 63, even if the piezoelectric film 50 is removed in portions other than the electrode film slits 60b, the piezoelectric film 50 outside the first region R1 is removed. Therefore, by forming the virtual shape KS into a hexagonal shape, it is possible to suppress a decrease in detection accuracy.

[0093] Furthermore, the imaginary shapes KS of the vibrating region 22 and the electrode film 60 are arranged to be point-symmetric with respect to the center C. In this embodiment, in the normal direction, the imaginary shape KS of the electrode film 60 is hexagonal, and the outer shape of the vibrating region 22 is a regular octagon. The vibrating region 22 and the electrode film 60 are arranged so that two opposing vertices of the imaginary shape KS of the electrode film 60 coincide with two opposing vertices of the outer shape of the vibrating region 22. In other words, the two opposing vertices of the imaginary shape KS of the electrode film 60 are arranged on an imaginary line K3 connecting the two opposing vertices of the vibrating region 22.

[0094] Furthermore, the piezoelectric element 1 (i.e., the vibrating portion 20) of this embodiment has a rectangular planar shape as described above. The imaginary shape KS of the vibrating region 22 and the electrode film 60 is formed so that each corner is located at a position different from the imaginary line K4 connecting the opposing corners of the outer shape of the piezoelectric element 1.

[0095] According to the present embodiment described above, the vibrating region 22 is supported at both ends, which makes it possible to increase the resonance frequency f of the piezoelectric element 1 and to obtain the same effects as those of the first embodiment.

[0096] (1) In this embodiment, the vibration region 22 and the electrode film 60 are arranged in point symmetry with respect to the center C in the normal direction. Therefore, when sound pressure is applied to the vibration region 22, it is easy to extract electric charge uniformly from the electrode film 60. Therefore, it is possible to prevent a decrease in detection sensitivity and a decrease in detection accuracy.

[0097] (2) In this embodiment, the imaginary shape KS of the vibrating region 22 and the electrode film 60 is formed so that each corner is located at a position different from the imaginary line K4 connecting the opposing corners of the outer shape of the piezoelectric element 1. This prevents a decrease in detection accuracy. In other words, in the piezoelectric element 1, the portion on the imaginary line K4 connecting the opposing corners is easily distorted by thermal stress or the like. In this case, if the corner of the vibrating region 22 or the corner of the imaginary shape KS of the electrode film 60 is located on the imaginary line K4, a large thermal stress is likely to be applied to the easily deformed corner, which tends to increase noise. Therefore, by locating the corners of the vibrating region 22 and the electrode film 60 at a position different from the imaginary line K4, as in this embodiment, a decrease in detection accuracy can be prevented.

[0098] (3) In this embodiment, the imaginary shape KS of the electrode film 60 is a hexagon. This prevents the crystallinity of the piezoelectric film 50 from being broken when the electrode film 60 is patterned. This prevents the characteristics of the piezoelectric element 1 from fluctuating.

[0099] (4) In this embodiment, the outer shape of the vibration region 22 is a regular octagon. This can prevent strain from concentrating in a local area of ​​the vibration region 22.

[0100] (Modification of the sixth embodiment) A modification of the sixth embodiment will be described. In the sixth embodiment, if the vibrating region 22 and the electrode film 60 are arranged so as to be point-symmetric with respect to the center C, it is possible to easily extract electric charge uniformly from the electrode film 60, as in the sixth embodiment. For this reason, for example, as shown in FIG. 27, the vibrating region 22 and the electrode film 60 may be arranged so that a pair of vertices of the imaginary shape KS of the electrode film 60 is located on an imaginary line K3 connecting the centers of a pair of opposing sides of the vibrating region 22 and the center C. Note that even in such a configuration, it is preferable that the vibrating region 22 and the electrode film 60 are formed so that each corner is located at a position different from the imaginary line K4. Also, in FIG. 27, as in FIG. 24A, the slits 40 are not shown.

[0101] Furthermore, in the sixth embodiment, similar to the modified example of the first embodiment, the electrode film 60 may be divided into a plurality of charge regions 60a in the first region R1 as shown in Fig. 28. Then, as shown in Fig. 29, each divided charge region 60a may be connected in series. When the electrode film 60 is configured in this manner, the electrode film 60 may be formed by slits 40 formed in the piezoelectric film 50.

[0102] (Seventh embodiment) A seventh embodiment will be described. In this embodiment, the location of the through-hole 101b of the piezoelectric device S10 is specified, in contrast to the first embodiment. As the rest is the same as the first embodiment, a description thereof will be omitted here.

[0103] 30 and 31, in the piezoelectric device S10 of this embodiment, the first to fourth slits 41 to 44 are formed in a portion of the printed circuit board 101 that is different from a portion facing the through hole 101b formed therein. In other words, the through hole 101b is formed in a portion of the printed circuit board 101 that is different from a portion facing the first to fourth slits 41 to 44. In FIG. 30, the portion facing the through hole 101b is indicated by a dashed line.

[0104] According to the present embodiment described above, the vibrating region 22 is supported at both ends, which makes it possible to increase the resonance frequency f of the piezoelectric element 1 and to obtain the same effects as those of the first embodiment.

[0105] (1) In this embodiment, the first to fourth slits 41 to 44 are formed in a portion different from the portion facing the through hole 101b formed in the printed circuit board 101. This prevents sound pressure from flowing directly into the back space S2 through the first to fourth slits 41 to 44. This reduces noise caused by Brownian motion in the first to fourth slits 41 to 44. Furthermore, it prevents foreign matter such as dust from accumulating in the first to fourth slits 41 to 44.

[0106] (Eighth embodiment) An eighth embodiment will be described. In this embodiment, the slit length L and other parameters are specified in comparison with the first embodiment. As the rest of the configuration is the same as the first embodiment, a description thereof will be omitted here.

[0107] The piezoelectric device S10 of this embodiment is basically the same as that of the first embodiment, and is configured as shown in FIG. 32. Note that the piezoelectric element 1 in FIG. 32 corresponds to the piezoelectric element 1 in FIG. 1C. FIG. 32 also schematically shows acoustic resistance Rg, which will be described later, and other parameters. In this case, the sensitivity of the piezoelectric device S10 is expressed as 1 / {(1 / Cm)+(1 / Cb)}, where Cm is the acoustic compliance of the piezoelectric element 1 and Cb is the acoustic compliance of the back space S2. Note that the acoustic compliance Cb is expressed by the following equation 2.

[0108]

number

[0109] In the first embodiment, the frequency range over which sensitivity can be maintained is broadened by increasing the resonant frequency of the piezoelectric element 1. In this case, the frequency range over which sensitivity can be maintained can also be broadened by reducing the low-frequency roll-off frequency. For this reason, in this embodiment, the low-frequency roll-off frequency is reduced.

[0110] First, the low frequency roll-off frequency fr is expressed by the following formula 3, where Rg is the acoustic resistance (that is, air resistance) due to the slits 40 (that is, the first to fourth slits 41 to 44).

[0111]

number

[0112]

number

[0113] In order to set the low frequency roll-off frequency fr to 20 Hz or less, which is outside the audible range, it is sufficient to satisfy the following formula 5.

[0114]

number

[0115]

number

[0116]

number

[0117] Here, for example, when the thickness h of the vibration region 22 is 1 μm, it is confirmed that the acoustic resistance Rg decreases as the slit width g increases and also decreases as the slit length L increases, as shown in Fig. 33. Furthermore, when the slit width g is 1 μm, it is confirmed that the acoustic resistance Rg decreases as the thickness h of the vibration region 22 increases and also decreases as the slit length L increases, as shown in Fig. 34. And, as shown in Fig. 35, for example, when the slit length L is 700 μm, which provides an acoustic resistance of about 100 Hz, it is confirmed that if the slit length L is about 150 μm, the acoustic resistance can be kept at 20 Hz or less.

[0118] In FIG. 35, the case where the slit length L is 700 μm is used as the reference, and therefore the acoustic resistance ratio when the slit length L is 700 μm is 1. Also, in FIG. 35, the volume of the back space S2 that affects the acoustic compliance Cb of the back space S2 is 4×10 -9 m 3 It states that:

[0119] According to the present embodiment described above, the vibrating region 22 is supported at both ends, which makes it possible to increase the resonance frequency f of the piezoelectric element 1 and to obtain the same effects as those of the first embodiment.

[0120] (1) In this embodiment, the slit length L, the slit width g, the thickness h of the vibration region 22, and the acoustic compliance Cb of the back space S2 are formed to satisfy the above-mentioned formula 7. Therefore, the low-frequency roll-off frequency fr can be set to 20 Hz or less, and the range in which sensitivity can be maintained can be widened.

[0121] (Ninth embodiment) A ninth embodiment will be described. This embodiment differs from the eighth embodiment in that the shape of the slit 40 is changed. As the rest of the configuration is the same as the eighth embodiment, a description thereof will be omitted here.

[0122] In the eighth embodiment, a configuration has been described in which the slit width g is constant along the thickness direction of the vibrating region 22. However, the slit 40 may be configured so that the slit width g varies along the thickness direction of the vibrating region 22, and may be configured so that the slit width g varies in three stages, for example, as shown in Fig. 36. Specifically, in this embodiment, the slits 40 (i.e., the first to fourth slits 41 to 44) are formed so that the slit width g increases in the order of g1, g2, and g3 from the other surface 22b side to the one surface 22a side of the vibrating region 22.

[0123] In this case, the slit length L is expressed by the following formula 8. In the following formula 8, the thickness of the vibrating region 22 where the slit width is g1 is defined as the thickness h1 of the vibrating region 22, the thickness of the vibrating region 22 where the slit width is g2 is defined as the thickness h2 of the vibrating region 22, and the thickness of the vibrating region 22 where the slit width is g3 is defined as the thickness h3 of the vibrating region 22.

[0124]

number

[0125] According to the present embodiment described above, the vibrating region 22 is supported at both ends, which makes it possible to increase the resonance frequency f of the piezoelectric element 1 and to obtain the same effects as those of the first embodiment.

[0126] (1) As in this embodiment, the slit 40 does not have to have a constant slit width g along the thickness direction of the vibrating region 22.

[0127] (Modification of the 10th embodiment) A modification of the tenth embodiment will be described. In the tenth embodiment, the shape of the slits 40 (i.e., the first to fourth slits 41 to 44) can be modified as appropriate. For example, as shown in FIG. 38A, the first to fourth slits 41 to 44 may have a constant slit width g on the other surface 22b side and a tapered shape that gradually widens on the one surface 22a side. Also, as shown in FIG. 38B, the first to fourth slits 41 to 44 may have a configuration in which the slit width g is narrowest at the center in the thickness direction of the vibrating region 22. And, as shown in FIG. 38C, the first to fourth slits 41 to 44 may be formed so that narrow and wide portions of the slit width g of the vibrating region 22 are alternately formed in the thickness direction of the vibrating region 22.

[0128] (Tenth embodiment) A tenth embodiment will be described. In this embodiment, the shape of the joining member 2 is specified in comparison with the first embodiment. As the rest is the same as the first embodiment, a description thereof will be omitted here.

[0129] In the piezoelectric device S10 of this embodiment, as shown in FIG. 39, the bonding member 2 has a rectangular outer shape with corners in the normal direction. The bonding member 2 is bonded to the other surface 11b of the support substrate 11 of the piezoelectric element 1 at a location different from the corners of the piezoelectric element 1. In this embodiment, the bonding member 2 is arranged so that the corners of the bonding member 2 protrude from opposing sides of the piezoelectric element 1 in the normal direction. The bonding member 2 is also arranged so that the corners of the bonding member 2 are located at locations different from the virtual line K4 connecting the opposing corners of the outer shape of the piezoelectric element 1. The bonding member 2 of this embodiment is formed using a bonding sheet whose outer shape is predetermined.

[0130] In addition, as in the sixth embodiment, the electrode film 60 and the vibration region 22 of this embodiment are hexagonal and regular octagonal, respectively. The electrode film 60 and the vibration region 22 are arranged point-symmetrically with respect to the center C. Note that the slits 40 are omitted in FIG. 39.

[0131] According to the present embodiment described above, the vibrating region 22 is supported at both ends, which makes it possible to increase the resonance frequency f of the piezoelectric element 1 and to obtain the same effects as those of the first embodiment.

[0132] (1) In this embodiment, the bonding member 2 is disposed in a portion of the piezoelectric element 1 that is different from the corners of the piezoelectric element 1. This prevents thermal stress from being transmitted from the printed circuit board 101 to the corners of the piezoelectric element 1, which are prone to large deformation. This makes it difficult for the piezoelectric element 1 to deform due to the transmitted thermal stress, and the vibration region 22 to deform. This prevents a decrease in detection sensitivity, and improves detection accuracy.

[0133] (2) In this embodiment, the bonding members 2 have a rectangular outer shape with corners. The bonding members 2 are arranged such that the corners are located at positions different from the virtual line K4 in the normal direction. This prevents stress from concentrating on the corners of the bonding members 2 due to deformation of the piezoelectric element 1, and prevents defects such as peeling of the bonding members 2 from occurring.

[0134] (Modification of the 10th embodiment) A modified example of the tenth embodiment will be described. The bonding members 2 may be formed in an equilateral triangular shape in the normal direction as shown in Fig. 40A, or in a regular octagonal shape in the normal direction as shown in Fig. 40B. Although not specifically shown, the bonding members 2 may also be formed in a regular hexagonal or regular decagonal shape in the normal direction. The bonding members 2 may be arranged so as to protrude from the piezoelectric element 1 in the normal direction, or may be arranged only inside the piezoelectric element 1.

[0135] The bonding member 2 may be disposed as shown in Fig. 41A to Fig. 41C, with reference to the through hole 101b formed in the printed circuit board 101. Fig. 41A to Fig. 41C are plan views of the piezoelectric element 1 and the bonding member 2 as viewed from the other surface 11b of the support substrate 11. In Fig. 41A to Fig. 41C, the vibrating region 22 is omitted, and the portion facing the through hole 101b is indicated by a dashed line. In Fig. 41A to Fig. 41C, the recess 10a formed in the support substrate 11 has a shape that coincides with the through hole 101b in the normal direction.

[0136] For example, as shown in FIG. 41A, the bonding member 2 may be annular and surround the through hole 101b in the normal direction. Also, as shown in FIG. 41B, the bonding member 2 may be cross-shaped in the normal direction, with a portion extending in one direction and a portion extending perpendicular to the one direction. Furthermore, as shown in FIG. 41C, the bonding member 2 may be diamond-shaped in the normal direction. In FIG. 41B, the corners of the bonding member 2 are positioned on the virtual line K4. However, even with this configuration, the bonding member 2 is bonded only to portions of the piezoelectric element 1 other than the corners, making it difficult for thermal stress to propagate to the corners of the piezoelectric element 1, and thus achieving the same effect as the tenth embodiment.

[0137] (Eleventh embodiment) An eleventh embodiment will be described. In this embodiment, in contrast to the first embodiment, protrusions are formed on the printed circuit board 101. As the rest is the same as the first embodiment, a description thereof will be omitted here.

[0138] 42, in the piezoelectric device S10 of this embodiment, a protrusion 101c is formed on the printed circuit board 101. Specifically, the protrusion 101c has a shape that matches the outer shape of the joining member 2 and is configured as a part of the printed circuit board 101. For example, the protrusion 101c of this embodiment is formed in a part of the printed circuit board 101 that faces the piezoelectric element 1, and is different from the part that faces the corner of the piezoelectric element 1.

[0139] According to the present embodiment described above, the vibrating region 22 is supported at both ends, which makes it possible to increase the resonance frequency f of the piezoelectric element 1 and to obtain the same effects as those of the first embodiment.

[0140] (1) In this embodiment, protrusions 101c are formed on the printed circuit board 101. Therefore, when applying and arranging the liquid bonding material 2, the outer shape of the bonding material 2 to be bonded to the piezoelectric element 1 can be easily adjusted by applying the bonding material 2 onto the protrusions 101c. Therefore, a liquid bonding material can be used as the bonding material 2, improving the selectivity of the bonding material 2. In particular, when adjusting the shape of the bonding material 2 as in the above tenth embodiment, the outer shape of the bonding material 2 can be easily adjusted.

[0141] (Modification of the eleventh embodiment) A modification of the eleventh embodiment will be described below. In the eleventh embodiment, the protruding portion 101c may be formed as a separate member from the printed circuit board 101.

[0142] (Twelfth embodiment) A twelfth embodiment will be described. This embodiment is different from the first embodiment in that the shape of the slit 40 is changed. As the rest is the same as the first embodiment, a description thereof will be omitted here.

[0143] In the piezoelectric element 1 of this embodiment, the piezoelectric film 50 is made of ScAlN. As shown in FIG. 43, the first slits 41 and the fourth slits 44 are formed so as to form tapered portions 45 whose widths narrow from the one surface 22a toward the other surface 22b. In other words, the first slits 41 and the fourth slits 44 are formed so that the side surfaces 22c form the tapered portions 45. Furthermore, the first slits 41 and the fourth slits 44 of this embodiment have a shape in which their widths continuously narrow from the one surface 22a toward the other surface 22b. In other words, the first slits 41 are formed so that the side surfaces 22c of the vibrating region 22 are substantially flat.

[0144] The first slit 41 and the fourth slit 44 are formed so that the angle θ1 formed between the other surface 22b and the side surface 22c of the vibrating region 22 (hereinafter simply referred to as the angle formed by the vibrating region 22) is 39 to 81°.

[0145] The angle θ1 can also be said to be the taper angle of the slit 40. The second slit 42 and the third slit 43 have the same shapes as the first slit 41 and the fourth slit 44 in a cross section different from that shown in FIG. 43. FIG. 43 corresponds to a cross section taken along line IC-IC in FIG. 1. The vibrating region 22 has one surface 22a and another surface 22b that are parallel to each other. In this embodiment, the other surface 22b corresponds to the surface parallel to the one surface 22a.

[0146] Next, a method for manufacturing the piezoelectric element 1 will be described with reference to Figures 44A to 44C, 45, and 46. Figures 44A to 44C correspond to cross-sectional views taken along line IC-IC in Figure 1. Although Figures 44A to 44C show cross-sectional views of the first slit 41 and the fourth slit 44, the same applies to the second and third slits 42 and 43.

[0147] First, a process similar to that shown in FIG. 4A is carried out to prepare a substrate in which the first to fourth slits 41 to 44 are not formed.

[0148] 44A, an etching mask material 200 made of photoresist or the like is disposed so as to cover the upper-layer electrode film 63 etc., and openings 201 are formed in the etching mask material 200, at which the first to fourth slits 41 to 44 are to be formed. The second and third slits 42 and 43 are formed on a cross section different from that shown in FIG. 44A. Hereinafter, the surface of the etching mask material 200 that covers the upper-layer electrode film 63 and the upper-layer piezoelectric film 52 will be referred to as the other surface 200b, the surface of the etching mask material 200 opposite to the other surface 200b will be referred to as the one surface 200a, and the side of the opening 201 will be referred to as the side surface 200c.

[0149] Next, as shown in FIG. 44B, a heat treatment is performed to adjust the shape of the opening 201 of the etching mask material 200. Specifically, the etching mask material 200 is disposed so as to cover the upper electrode film 63 and the upper piezoelectric film 52, and the portion on the other surface 200b side, which is fixed thereto, thermally shrinks differently from the portion on the one surface 200a side. More specifically, when the heat treatment is performed, the portion on the other surface 200b side of the etching mask material 200 is less susceptible to thermal shrinkage, while the portion on the one surface 200a side is more susceptible to thermal shrinkage. Therefore, the heat treatment is performed to adjust the angle θ2 formed between the other surface 200b and the side surface 200c of the etching mask material 200 (hereinafter simply referred to as the angle θ2 formed by the etching mask material 200) to match the angle θ1 formed by the desired vibration region 22. In this case, since the piezoelectric film 50 and the etching mask material 200 are made of different materials, their etching rates are usually different when anisotropic dry etching, which will be described later, is performed. Therefore, based on the etching rate etc., the angle θ2 formed by the etching mask material 200 is adjusted so that the angle θ1 formed by the vibration region 22 has a desired value. Note that, since the angle θ2 formed by the etching mask material 200 here is adjusted as described above, it may match the angle θ1 formed by the vibration region 22 in some cases, but it may not match the angle θ1 formed by the vibration region 22 in other cases.

[0150] 44C, anisotropic dry etching is performed using the etching mask material 200 as a mask to form first to fourth slits 41 to 44 that penetrate the piezoelectric film 50 and reach the support 10. In this embodiment, the first to fourth slits 41 to 44 are formed so as to form a vibrating region component 220 having a side surface 22c that becomes a tapered portion 45.

[0151] As described above, the angle θ2 of the etching mask material 200 is adjusted according to the angle θ1 of the vibration region 22, and the angle θ1 of the vibration region component 220 is set to 39 to 81°. The vibration region component 220 is the portion that becomes the vibration region 22 by forming the recess 10a. Therefore, the angle θ1 of the vibration region component 220 is the same as the angle θ1 of the vibration region 22. In the drawing, the same reference numerals are assigned to the one surface 22a, the other surface 22b, and the side surface 22c of the vibration region 22 for the one surface 22a, the other surface 22b, and the side surface 22c of the vibration region 22. The shapes of the lower electrode film 61, the intermediate electrode film 62, and the upper electrode film 63 are adjusted so that they do not reach the first to fourth slits 41 to 44. Therefore, in this process, the piezoelectric film 50 and the base film 70 are anisotropically dry-etched.

[0152] 4C, etching is performed from the other surface 11b of the support substrate 11 through the insulating film 12 to reach the base film 70, forming the recess 10a. As a result, the vibrating region component 220 is suspended from the support 10, forming the vibrating region 22, and the piezoelectric element 1 shown in FIG. 1 is manufactured.

[0153] Next, the angle θ1 formed by the vibrating region component 220 (that is, the vibrating region 22) in the manufacturing process of this embodiment will be described.

[0154] First, according to the inventors' investigations, when a piezoelectric film 50 made of ScAlN or the like is anisotropically dry etched, the following phenomenon has been confirmed when the angle θ1 is 81° or greater. That is, when the angle θ1 is 81° or greater, the etched atoms are redeposited on the side surfaces 22c of the first to fourth slits 41 to 44, which tends to reduce the processability. Furthermore, according to the inventors' investigations, when a piezoelectric film 50 made of ScAlN or the like is anisotropically dry etched, the following phenomenon has been confirmed when the angle θ1 is 63° or greater. That is, when the angle θ1 is 63° or greater, the etched atoms are redeposited near the openings of the first to fourth slits 41 to 44 on the one surface 22a side, which tends to reduce the processability. For this reason, when forming the first to fourth slits 41 to 44, it is preferable that the angle θ1 be 63° or less. This can prevent the processability from being reduced by the fences or the like.

[0155] Furthermore, 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 forming the first to fourth slits 41 to 44 penetrating the piezoelectric film 50, it has been confirmed that the thickness of the etching mask material 200 is preferably 1 to 5 times the thickness of the piezoelectric film 50 so that the etching mask material 200 remains on the piezoelectric film 50. In other words, when forming the first to fourth slits 41 to 44 penetrating the piezoelectric film 50, it has been confirmed that the thickness of the etching mask material 200 is preferably 1 to 5 times the thickness of the piezoelectric film 50 so that the piezoelectric film 50 covered with the etching mask material 200 is not removed by anisotropic dry etching. That is, as shown in FIG. 45 , when the thickness of the piezoelectric film 50 is A1, the thickness A2 of the etching mask material 200 is preferably A1 to 5A1. Note that the base film 70 of this embodiment is formed to be extremely thin compared to the piezoelectric film 50, as described above. For this reason, the influence of the base film 70 is ignored. In other words, the film thickness A1 of the piezoelectric film 50 corresponds to the thickness h of the vibration region 22 described above.

[0156] Furthermore, when forming the first to fourth slits 41 to 44, they are also affected by exposure restrictions of the processing equipment. According to the study by the present inventors, with current general processing equipment, as shown in Fig. 45, when the width of the first to fourth slits 41 to 44 on the one surface 22a side is defined as the slit width g, it has been confirmed that the resolution of the slit width g relative to the film thickness A2 of the etching mask material 200 is limited to 1 / 2 to 1 / 3 of the film thickness A2 of the etching mask material 200. Therefore, since the film thickness A2 of the etching mask material 200 is represented by A1 to 5A1, the slit width g has a limit in the range of A1 / 3 to 5A1 / 2.

[0157] In the piezoelectric element 1 described above, sound pressure escapes through the first to fourth slits 41 to 44. In this case, as shown in FIG. 46, the longer the effective width of the first to fourth slits 41 to 44, the lower the sensitivity at low frequencies. For this reason, it is preferable that the first to fourth slits 41 to 44 are formed so that their effective widths are narrower. The effective width of the first to fourth slits 41 to 44 refers to the average width of the first to fourth slits 41 to 44. For example, in the present embodiment, when the first to fourth slits 41 to 44 are tapered such that the slit width g continuously narrows from the one surface 22a toward the other surface 22b, the effective width is the average of the width on the one surface 22a side and the width on the other surface 22b side.

[0158] In this embodiment, the first to fourth slits 41 to 44 are formed by anisotropic dry etching, resulting in a substantially flat side surface 22c. Therefore, assuming that the width of the first to fourth slits 41 to 44 on the other surface 22b side is substantially zero to prevent sensitivity degradation, and assuming that the thickness of the piezoelectric film 50 is A1 and the width of the slit on the one surface 22a side is g, tan θ1 = A1 / (g / 2). Note that g / 2 can also be considered the effective slit width. Therefore, since the slit width g is A1 / 3 to 5A1 / 2 as described above, tan θ1 = 6 to 0.8, and θ1 = 39 to 81° is preferable. In other words, when forming the first to fourth slits 41 to 44, it is preferable that the angle θ1 formed by the vibration region component 220 be 39 to 81°. This prevents degradation of the processability of the first to fourth slits 41 to 44 due to the film thickness A2 of the etching mask material 200.

[0159] 47 shows the relationship between the ratio of the thickness A2 of the etching mask material 200 to the thickness A1 of the piezoelectric film 50 (hereinafter also referred to as the thickness ratio), and the formed angle. As described above, the resolution of the slit width g relative to the thickness A2 of the etching mask material 200 is limited to 1 / 2 to 1 / 3 of the thickness A2 of the etching mask material 200. Therefore, the lower limit of the formed angle θ1, 39°, occurs when the resolution is 1 / 2 times that of the etching mask material 200, and the upper limit occurs when the resolution is 1 / 3 times that of the etching mask material.

[0160] Here, a comparative piezoelectric element 1 is taken as an example in which the piezoelectric film 50 is made of an easily etchable material such as AlN, and the side surface 22c of the vibration region 22 is approximately perpendicular to the other surface 22b. The effective width of the slits 40 in the comparative piezoelectric element 1 is defined as g. In this case, if the effective width in the piezoelectric element 1 of this embodiment is g or more, the slit width g of the first to fourth slits 41 to 44 will become too wide, and the sensitivity may be lower than that of the comparative piezoelectric element 1.

[0161] Therefore, it is preferable that the slits 40 are formed so that their effective width is equal to or less than the effective width of the slits 40 in the piezoelectric element 1 of the comparative example. In other words, it is preferable that the slits 40 are configured so that tan θ1 is 1 or greater. For this reason, it is preferable that θ1 is 45° or greater. This also prevents a decrease in sensitivity. In this case, by setting θ1 to 63° or less, it is possible to prevent a decrease in the workability of the slits 40 due to a fence or the like.

[0162] According to the present embodiment described above, the vibrating region 22 is supported at both ends, which makes it possible to increase the resonance frequency f of the piezoelectric element 1 and to obtain the same effects as those of the first embodiment.

[0163] (1) In this embodiment, the angle θ1 formed by the vibration region 22 is set to 39 to 81 degrees. This makes it possible to prevent a decrease in the processability of the slit 40 due to the film thickness A2 of the etching mask material 200, and the slit 40 can be suitably formed. Furthermore, because the angle θ1 is 81 degrees or less, it is possible to reduce the influence of redeposition and prevent a decrease in the processability.

[0164] (2) In this embodiment, the angle θ formed by the vibration region 22 is set to 63° or less, which can prevent the workability from being reduced due to the influence of the fence.

[0165] (3) In this embodiment, the angle θ1 formed by the vibration region 22 is set to 45° or more, which further prevents the detection sensitivity from decreasing.

[0166] As in the above-described ninth embodiment, this embodiment can also be applied to the case where the slits 40 are formed stepwise along the thickness direction of the vibrating region 22. In this case, as shown in Fig. 36, the angle θ1 is defined as the angle formed between the other surface 22b and the line connecting the opening end of the slit 40 on the other surface 22b side and the opening end of the slit 40 on the one surface 22a side.

[0167] Furthermore, when forming the electrode film slits 60b in the electrode film 60 as in the sixth embodiment, the slits 40 are formed each time each of the piezoelectric films 51, 52 is formed. Therefore, in this configuration, the angle θ1 is set as the angle between the side surface 20c and the portion of each of the piezoelectric films 51, 52 on the other surface 20b side.

[0168] (Modification of the twelfth embodiment) A modification of the twelfth embodiment will be described. In the twelfth embodiment, when the first slits 41 to 44 are formed, dry etching may be performed after wet etching. In this case, the etching mask material 200 is not removed when wet etching is performed, so that the film thickness A2 of the etching mask material 200, which is determined based on the film thickness A1 of the piezoelectric film 50, can be made thinner, and the slit width g, which is determined by the film thickness A2 of the etching mask material 200, can be made narrower. Therefore, the effective width g / 2 can be made narrower, and sensitivity can be improved.

[0169] (Other embodiments) Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and modifications within the scope of equivalents. In addition, various combinations and forms, as well as other combinations and forms including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

[0170] For example, in each of the above embodiments, the vibration section 20 may be configured to have at least one layer of piezoelectric film 50 and one layer of electrode film 60. Furthermore, the piezoelectric element 1 may have a polygonal planar shape such as a pentagonal or hexagonal shape instead of a rectangular shape.

[0171] In each of the above embodiments, the piezoelectric device S10 may be configured such that a through-hole 102a is formed in the lid portion 102, as shown in Fig. 48. In this case, as shown in Fig. 48, the pressure-receiving surface space S1 is the space on one surface 22a side of the vibration region 22 of the casing 100, and the back space S2 is the space on the other surface 22b side of the vibration region 22 of the casing 100.

[0172] In the above embodiments, the piezoelectric element 1 has been described in which the vibrating region 22 is supported at both ends to improve detection accuracy. However, for example, in the second embodiment, the slit 40 can be tapered to improve detection accuracy. In the sixth embodiment, the shapes of the piezoelectric film 50 and the electrode film 60 can be adjusted to improve detection accuracy. In the seventh embodiment, the positional relationship between the slit 40 and the through-hole 101b can be adjusted to improve detection accuracy. In the eighth embodiment, the low-frequency roll-off frequency can be reduced to improve detection accuracy of the piezoelectric element 1. In the tenth embodiment, the positional relationship between the piezoelectric element 1 and the bonding member 2 can be adjusted to improve detection accuracy. Therefore, in these piezoelectric elements 1 or piezoelectric devices S10, the vibrating region 22 may be cantilevered. That is, for example, if the outer shape of the vibrating region 22 is rectangular in plan view and the first to fourth slits 41 to 44 are formed in the vibrating region 22, the first to fourth slits 41 to 44 may be formed to intersect at the center C of the vibrating region 22. The manufacturing method in the twelfth embodiment relates to the shape of the slits 40, and is therefore also applicable to a manufacturing method for a piezoelectric element 1 in which the vibrating region 22 is cantilevered.

[0173] The above embodiments may be combined as appropriate. For example, the second embodiment may be combined with any of the third to twelfth embodiments, so that the slit 40 has a tapered shape that narrows toward the center C. The third embodiment may be combined with any of the fourth to twelfth embodiments, so that charge is also extracted from the central region 225 of the vibrating region 22. The fourth or fifth embodiment may be combined with any of the sixth to twelfth embodiments, so that the vibrating region 22 is supported at both ends by the connecting member 90 or the connecting member 91. The sixth embodiment may be combined with any of the seventh to twelfth embodiments, so that the shape and arrangement of the vibrating region 22 and the electrode film 60 are defined. The seventh embodiment may be combined with any of the eighth to twelfth embodiments, so that the slit 40 is formed in a portion different from the portion facing the through-hole 101b. The eighth embodiment may be combined with any of the ninth to twelfth embodiments, so that the slit length L is defined. The ninth embodiment may be combined with any of the tenth to twelfth embodiments so that the slit width g of the slit 40 varies along the thickness direction of the vibration region 22. The tenth embodiment may be combined with any of the eleventh and twelfth embodiments so that the location of the joining member 2 is defined. The eleventh embodiment may be combined with the twelfth embodiment so that the protrusion 101c is formed on the printed circuit board 101. Furthermore, combinations of the above embodiments may be further combined with each other. [Explanation of symbols]

[0174] 10 Support 20 Vibration unit 21a Support area 22 Vibration area 50 Piezoelectric film 60 Electrode membrane C center

Claims

1. A piezoelectric element having a vibration part (20) that outputs a pressure detection signal according to pressure, A support (10); The vibration unit is disposed on the support and includes a piezoelectric film (50) and an electrode film (60) connected to the piezoelectric film and extracting electric charges generated by deformation of the piezoelectric film, and has a support region (21 a) supported by the support and a vibration region (22) connected to the support region and floating above the support, and outputs the pressure detection signal based on the electric charges; The vibration region has a plurality of slits (40 to 44) formed from the support region side toward a center (C) of the vibration region, and is supported at both ends by the support region, a base film (70) is provided between the support and the piezoelectric film; The slit is a piezoelectric element that is formed so that, when the surface opposite the support in the vibration region is one surface (22a) and the surface on the support side in the vibration region is the other surface (22b), a tapered portion (45) is formed whose width narrows from the one surface side toward the other surface side.

2. A piezoelectric element as described in Claim 1, wherein the angle (θ1) formed between the side surface (22c) constituting the tapered portion in the vibration region and a surface (22b) parallel to the one surface is 39 to 81°.

3. 3. The piezoelectric element according to claim 1, wherein the base film is thinner than the piezoelectric film.

4. A piezoelectric device including a piezoelectric element having a vibration part (20) that outputs a pressure detection signal according to pressure, A piezoelectric element according to any one of claims 1 to 3; The piezoelectric element is mounted on a mounting member (101), and a lid (102) is fixed to the mounting member in a state where the piezoelectric element is housed therein. The casing (100) has a through hole (101b) formed therein, the through hole communicating with the outside and through which the pressure is introduced. The slit is formed in a portion of the vibration region that is different from a portion facing the through hole.

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