Piezoelectric element

Abstract

To provide a piezoelectric element capable of reducing dielectric loss tangent of a piezoelectric film.SOLUTION: A piezoelectric element includes a support body 10 having a support surface 121, and a vibration section 20 formed on the support surface. The vibration section has a first electrode 61, a piezoelectric film 50, and a second electrode 62 which are aligned in a lamination direction of the support body and the vibration section, and has an insulation film 80 for increasing an electric resistance value between the first electrode and the second electrode. The first electrode is arranged on the support surface, and has an aperture 612 formed through in a lamination direction and a first electrode surface 611 formed on the opposite side to the support surface side. The piezoelectric film is formed across the aperture on the first electrode surface and has a piezoelectric film surface 501 formed on the opposite side to the first electrode surface side. The seconde electrode is formed on the piezoelectric film surface. The insulation film is formed at a position where at least a part of the insulation film is overlapped with the aperture in the lamination direction between the first electrode and the second electrode.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Conventionally, a piezoelectric element has been known that includes a plate-shaped vibration plate that functions as a substrate, a first electrode, a second electrode, and a piezoelectric layer provided between the first and second electrodes (see, for example, Patent Document 1). In this piezoelectric element, the first electrode is filled in a recess formed by recessing into a first surface, which is the surface of the substrate, and has an upper surface that forms a continuous plane with the first surface. In addition, the piezoelectric layer is formed across the substrate and the first electrode on the continuous plane formed by the first surface of the substrate and the upper surface of the first electrode.

[0003] Patent Document 1 also describes that by forming the first surface of the substrate, which is the interface for crystal growth of the piezoelectric layer, and the top surface of the first electrode into a continuous flat surface, crystal growth during crystallization of the piezoelectric layer is stabilized. Hereinafter, the piezoelectric layer is also referred to as a piezoelectric film. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2012-59770 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, according to the inventor's intensive research, even if the substrate and the electrode are formed in a continuous plane, a slight step occurs at the connection portion between the substrate and the electrode. Therefore, when forming a piezoelectric film across the substrate and the electrode, it is found that there is a risk of abnormal crystal grains occurring at the connection portion between the substrate and the electrode. In addition, when forming a piezoelectric film across a substrate and an electrode made of different materials, it is found that there is a risk of the crystal orientation of the piezoelectric film being disturbed at the crossing portion.

[0006] The occurrence of these abnormal crystal grains and disturbance in the crystal orientation deteriorates the dielectric loss tangent of the piezoelectric film, which causes a deterioration in the sensitivity of the piezoelectric element.

[0007] An object of the present disclosure is to provide a piezoelectric element capable of reducing the dielectric tangent of a piezoelectric film. [Means for solving the problem]

[0008] The invention described in claim 1 is A piezoelectric element, A support (10) having a support surface (121); A vibration portion (20) provided on the support surface, The vibration section has a first electrode (61), a piezoelectric film (50), and a second electrode (62) arranged side by side in a stacking direction of the support body and the vibration section, and also has an insulating section (80) that increases the electrical resistance value between the first electrode and the second electrode; The first electrode is provided on the support surface and has an opening (612) formed penetrating in the stacking direction and a first electrode surface (611) formed on the side opposite to the support surface side, The piezoelectric film is provided across the opening on the first electrode surface, and has a piezoelectric film surface (501) formed on the opposite side to the first electrode surface side; The second electrode is provided on the piezoelectric film surface, The insulating portion is provided between the first electrode and the second electrode at a position where at least a portion of the insulating portion overlaps with the opening in the stacking direction.

[0009] According to this, the electrical resistance between the first electrode film and the second electrode film can be increased by the insulating portion provided at a position overlapping with the opening in the stacking direction, and therefore, even if crystallinity abnormalities occur in the portion of the piezoelectric film spanning the opening, deterioration of the dielectric tangent of the piezoelectric film can be reduced compared to when the insulating portion is not provided.

[0010] The reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and specific components described in the embodiments described below. [Brief description of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view of a piezoelectric element according to a first embodiment. [Diagram 2] FIG. 2 is a plan view of the piezoelectric element shown in FIG. [Diagram 3] 2 is a plan view of the piezoelectric element shown in FIG. 1 with an upper electrode film and a piezoelectric film removed. [Figure 4] FIG. 13 is a diagram showing the relationship between the size of an insulating film and its electrical resistance value. [Diagram 5] FIG. 10 is a view corresponding to FIG. 1 according to a second embodiment. [Figure 6] FIG. 11 is a view corresponding to FIG. 1 according to a first modified example of the second embodiment. [Figure 7] FIG. 11 is a view corresponding to FIG. 1 according to a third modified example of the second embodiment. [Figure 8] FIG. 11 is a view corresponding to FIG. 1 according to a third embodiment. [Figure 9] FIG. 11 is a view corresponding to FIG. 1 according to a fourth embodiment. [Figure 10] FIG. 11 is a view corresponding to FIG. 1 according to a first modified example of the fourth embodiment. [Figure 11] FIG. 11 is a view corresponding to FIG. 1 according to the fifth embodiment. [Figure 12] FIG. 11 is a view corresponding to FIG. 1 according to a modified example of the fifth embodiment. [Figure 13] FIG. 2 is a view corresponding to FIG. 1 according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, the embodiments of the present disclosure will be described with reference to the drawings. In the following embodiments, the same reference numerals are used for parts that are the same as or equivalent to those described in the preceding embodiments, and the description thereof may be omitted. In addition, in the embodiments, when only a part of the components is described, the components described in the preceding embodiments can be applied to the other parts of the components. In the following embodiments, each embodiment can be partially combined with each other, even if not specifically stated, as long as it does not cause any trouble in combination.

[0013] (First embodiment) A piezoelectric element 1 according to a first embodiment will be described with reference to Figures 1 to 4. The piezoelectric element 1 according to this embodiment is suitable for use as a microphone, for example.

[0014] 1 to 3, the piezoelectric element 1 of this embodiment includes a support 10 and a vibration section 20 formed on the support 10. Hereinafter, the direction in which the support 10 and the vibration section 20 are connected to each other is also referred to as a stacking direction D1.

[0015] The support 10 has a support substrate 11 and an insulating layer 12 formed side by side in a stacking direction D1. The support substrate 11 is made of, for example, a silicon substrate. The insulating layer 12 is formed on the support substrate 11 and is made of, for example, an oxide film. The insulating layer 12 has a support surface 121 on which the vibration section 20 is disposed.

[0016] The vibration section 20 constitutes the sensing section 30 that outputs a pressure detection signal corresponding to pressure such as sound pressure, and is disposed on the support surface 121. The support body 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 surface 121, and a floating region 21b that is connected to the support region 21a and floats on the recess 10a. The recess 10a has an open end on the vibration section 20 side that is substantially rectangular in plan view. Therefore, the floating region 21b is substantially rectangular in plan view.

[0017] As shown in Fig. 2 and Fig. 3, the floating region 21b is formed with a separation slit 40 penetrating the floating region 21b in the stacking direction D1. In this embodiment, the separation slit 40 is formed so as to divide the floating region 21b into four. More specifically, two separation slits 40 are formed so as to pass through the center C of the floating region 21b and extend toward opposing corners of the floating region 21b. In other words, the separation slits 40 are formed so as to extend from each corner of the floating region 21b, which is substantially rectangular in plan view, toward the center C, and the separation slits 40 intersect at the center C.

[0018] As a result, the floating region 21b is divided into a first vibration region 22a to a fourth vibration region 22d each having a substantially triangular shape in plan view. Specifically, the floating region 21b is made up of the first vibration region 22a to the fourth vibration region 22d each having a substantially isosceles triangular shape in plan view, each having two sides of equal length extending toward the center C of the floating region 21b and a base connected to the two sides.

[0019] Although not particularly limited, in this embodiment, the interval between the first vibration region 22a to the fourth vibration region 22d, i.e., the width of the separating slit 40, is about 1 μm. Furthermore, the separating slit 40 in this embodiment is formed so as to terminate within the floating region 21b, but may be extended to the supporting region 21a.

[0020] The first vibration region 22a to the fourth vibration region 22d are configured as cantilevers with the end on the support region 21a side as a fixed end and the tip end on the opposite side to the support region 21a as a free end. That is, the first vibration region 22a to the fourth vibration region 22d are connected to the support region 21a and are supported in a cantilevered manner. Hereinafter, the fixed end side of the first vibration region 22a to the fourth vibration region 22d is also referred to as a first region R1, and the free end side is also referred to as a second region R2.

[0021] The vibration section 20 has a seed layer 31, a piezoelectric film 50, and an electrode film 60 connected to the piezoelectric film 50. The seed layer 31 is formed on the support surface 121, and is made of, for example, thin-film aluminum nitride, that is, AlN.

[0022] The electrode film 60 has a lower electrode film 61 and an upper electrode film 62. The vibration part 20 has a portion positioned in the floating region 21b of the piezoelectric film 50 sandwiched between the lower electrode film 61 and the upper electrode film 62. The lower electrode film 61 is formed on the support surface 121 via a seed layer 31. The lower electrode film 61 has a lower electrode surface 611 on the side opposite to the support surface 121.

[0023] The upper electrode film 62 is formed on the piezoelectric film 50. The piezoelectric film 50 has a piezoelectric film surface 501 on which the upper electrode film 62 is provided, on the side opposite to the lower electrode surface 611. In other words, the upper electrode film 62 is formed on the piezoelectric film surface 501.

[0024] The vibration section 20 also has an insulating film 80 (described later) that increases the electrical resistance between the lower electrode film 61 and the upper electrode film 62. The insulating film 80 is provided between the lower electrode film 61 and the upper electrode film 62. The lower electrode film 61 corresponds to the first electrode, the lower electrode surface 611 corresponds to the first electrode surface, the upper electrode film 62 corresponds to the second electrode, and the insulating film 80 corresponds to the insulating portion.

[0025] The lower electrode film 61 and the upper electrode film 62 are formed by etching, and are formed in the first vibration region 22a to the fourth vibration region 22d, respectively. The lower electrode film 61 and the upper electrode film 62 formed in the first vibration region 22a to the fourth vibration region 22d, respectively, are formed in a shape corresponding to the first vibration region 22a to the fourth vibration region 22d, which are substantially triangular in plan view. That is, the lower electrode film 61 and the upper electrode film 62 are formed in a substantially triangular plan view, and the area of ​​the triangle is smaller than the area of ​​the first vibration region 22a to the fourth vibration region 22d. The lower electrode film 61 and the upper electrode film 62 at least partially overlap each other in the stacking direction D1. The lower electrode film 61 and the upper electrode film 62 of this embodiment completely overlap each other in the stacking direction D1, and the outer edges are formed in substantially the same shape.

[0026] The lower electrode film 61 and the upper electrode film 62 of this embodiment are formed in the first region R1 and the second region R2 in the first vibration region 22a to the fourth vibration region 22d, respectively. The lower electrode film 61 and the upper electrode film 62 formed in the first region R1 do not extend to the support region 21a. The lower electrode film 61 and the upper electrode film 62 formed in the first region R1 may be formed to extend to the support region 21a. The lower electrode film 61 and the upper electrode film 62 are connected to the electrode portion 70 provided in the support region 21a shown in FIG. 2 via electrical wiring (not shown).

[0027] The lower electrode film 61 and the upper electrode film 62 formed in each of the first vibrating region 22a to the fourth vibrating region 22d have the same basic configuration. Also, the insulating film 80 formed between the lower electrode film 61 and the upper electrode film 62 in each of the first vibrating region 22a to the fourth vibrating region 22d have the same basic configuration. Therefore, in the following, the lower electrode film 61, the upper electrode film 62, and the insulating film 80 formed in the first vibrating region 22a will be described in detail, and the lower electrode film 61, the upper electrode film 62, and the insulating film 80 formed in the second vibrating region 22b to the fourth vibrating region 22d may not be described in detail.

[0028] The lower electrode film 61 of this embodiment is divided into a plurality of parts as shown in Fig. 3. Moreover, the upper electrode film 62 is divided into a plurality of parts as shown in Fig. 2.

[0029] 3, the lower layer electrode film 61 is divided into two parts, a lower layer inner electrode film 61a having a substantially isosceles triangular shape in plan view and a lower layer outer electrode film 61b having a substantially trapezoidal shape in plan view, by the lower layer first slit 612. Furthermore, the lower layer outer electrode film 61b having a substantially trapezoidal shape in plan view is divided into three substantially trapezoidal shapes having different shapes by two lower layer second slits 613. The lower layer first slit 612 and the lower layer second slit 613 are formed penetrating the lower layer electrode film 61 in the stacking direction D1.

[0030] The lower layer first slits 612 are formed along the direction in which the base of the lower layer electrode film 61 having a substantially isosceles triangular shape in plan view extends. That is, the lower layer first slits 612 are formed along a direction perpendicular to the direction from the center of the base of the first vibrating region 22a toward the center C in a plane perpendicular to the stacking direction D1. Hereinafter, the direction in which the lower layer first slits 612 of each of the first vibrating region 22a to the fourth vibrating region 22d extend is also referred to as the slit direction D2, and the direction perpendicular to the slit direction D2 and the stacking direction D1 is also referred to as the slit width direction D3. The lower layer first slits 612 correspond to an opening, and the slit width direction D3 corresponds to the cross-sectional width direction.

[0031] The two lower layer second slits 613 are formed so as to extend from two points that divide the base of the substantially isosceles triangular lower layer electrode film 61 into three equal parts toward the approximate center of the lower layer inner electrode film 61a. The two lower layer second slits 613 thus formed do not intersect with each other.

[0032] 2, the upper layer electrode film 62 is divided into two parts, an upper layer inner electrode film 62a having a substantially isosceles triangular shape in plan view and an upper layer outer electrode film 62b having a substantially trapezoidal shape in plan view, by the upper layer first slit 622. Furthermore, the upper layer outer electrode film 62b having a substantially trapezoidal shape in plan view is divided into three substantially trapezoidal shapes having different shapes in plan view by two upper layer second slits 623. The upper layer first slit 622 and the upper layer second slit 623 are formed penetrating the upper layer electrode film 62 in the stacking direction D1.

[0033] The upper layer first slits 622 are formed along the slit direction D2. That is, the upper layer first slits 622 are formed along a direction perpendicular to the slit width direction D3 in a plane perpendicular to the stacking direction D1.

[0034] 1, the upper layer first slit 622 is formed shifted in the slit width direction D3 with respect to the formation position of the lower layer first slit 612 so as not to overlap with the lower layer first slit 612 in the stacking direction D1. Specifically, the upper layer first slit 622 is formed in a position closer to the support region 21a than the lower layer first slit 612. In other words, the upper layer first slit 622 is formed in a position farther from the center C of the floating region 21b than the lower layer first slit 612. The upper layer first slit 622 is formed in a position that positions the upper layer inner electrode film 62a in the second region R2 and positions the upper layer outer electrode film 62b in the first region R1.

[0035] The two upper layer second slits 623 are formed so as to extend from two points that divide the base of the upper layer electrode film 62 having a substantially isosceles triangular shape toward the approximate center of the upper layer inner electrode film 62a. The two upper layer second slits 623 thus formed do not intersect with each other. The two upper layer second slits 623 are formed at positions that overlap with the lower layer second slits 613 in the stacking direction D1.

[0036] In the piezoelectric element 1 thus formed, in each of the first vibration region 22a to the fourth vibration region 22d, the lower-layer inner electrode film 61a and the upper-layer inner electrode film 62a face each other in the stacking direction D1 via the piezoelectric film 50. In addition, in each of the first vibration region 22a to the fourth vibration region 22d, the piezoelectric element 1 has three lower-layer outer electrode films 61b and three upper-layer outer electrode films 62b face each other in the stacking direction D1 via the piezoelectric film 50.

[0037] Furthermore, in each of the first to fourth vibration regions 22a to 22d of the piezoelectric element 1, parts of the three lower-layer outer electrode films 61b and parts of the upper-layer inner electrode films 62a face each other in the stacking direction D1 via the piezoelectric film 50. However, in each of the first to fourth vibration regions 22a to 22d of the piezoelectric element 1, the lower-layer inner electrode films 61a and the upper-layer outer electrode films 62b do not face each other in the stacking direction D1.

[0038] In this embodiment, the end of the lower layer inner electrode film 61a on the fixed end side in the slit width direction D3 is positioned closer to the free end side than the end of the upper layer inner electrode film 62a on the fixed end side in the slit width direction D3. In contrast, the end of the lower layer outer electrode film 61b on the free end side in the slit width direction D3 is positioned closer to the free end side than the end of the upper layer outer electrode film 62b on the free end side in the slit width direction D3.

[0039] The lower electrode films 61 formed in the first vibrating region 22a to the fourth vibrating region 22d are electrically connected in series to each other via a lower wiring portion 61c. The upper electrode films 62 formed in the first vibrating region 22a to the fourth vibrating region 22d are electrically connected in series to each other via an upper wiring portion 62c.

[0040] As a result, in the floating region 21b, a capacitance is formed between the lower electrode film 61 and the upper electrode film 62 in each of the first vibrating region 22a to the fourth vibrating region 22d.

[0041] Although not particularly limited, in this embodiment, the lower electrode film 61 and the upper electrode film 62 are made of molybdenum. The lower electrode film 61 and the upper electrode film 62 may be made of a metal material containing, as a main component, any one of titanium, platinum, aluminum, ruthenium, silicon, etc., in addition to molybdenum. Furthermore, these materials constituting the lower electrode film 61 and the upper electrode film 62 are materials whose lattice number is closer to that of the piezoelectric film 50 than that of the insulating layer 12.

[0042] The piezoelectric film 50 is formed on a lower electrode surface 611 of a lower electrode film 61 in which a lower layer first slit 612 and a lower layer second slit 613 are formed. That is, the piezoelectric film 50 fills the lower layer first slit 612 and the lower layer second slit 613, and is formed on the lower electrode surface 611 across the lower layer first slit 612 and the lower layer second slit 613.

[0043] Although not particularly limited, in this embodiment, the piezoelectric film 50 contains scandium. For example, the piezoelectric film 50 is made of scandium aluminum nitride, that is, ScAlN.

[0044] When the piezoelectric film 50 is made of scandium aluminum nitride, the greater the mass of scandium contained per unit mass of the piezoelectric film 50, the easier it is to improve the detection sensitivity of the sound pressure of the piezoelectric element 1. In other words, the higher the concentration of scandium in the piezoelectric film 50 made of scandium aluminum nitride, the easier it is to improve the detection sensitivity of the sound pressure of the piezoelectric element 1. For this reason, in this embodiment, the piezoelectric film 50 is made of scandium aluminum nitride, which has a relatively high concentration of scandium.

[0045] The sensing section 30 of this embodiment is configured to output a change in charge in each of the first vibration area 22a to the fourth vibration area 22d as one pressure detection signal. In other words, the first vibration area 22a to the fourth vibration area 22d are electrically connected in series.

[0046] Next, the insulating film 80 will be described. The insulating film 80 in this embodiment is provided between the lower electrode film 61 and the upper electrode film 62 formed in each of the first vibrating region 22a to the fourth vibrating region 22d, at a position where at least a part of the insulating film 80 overlaps with the lower first slit 612 in the stacking direction D1. Specifically, the insulating film 80 is formed in a substantially planar thin film shape between the lower electrode surface 611 and the upper electrode film 62 at a position away from the lower electrode surface 611 in each of the first vibrating region 22a to the fourth vibrating region 22d. In this embodiment, the insulating film 80 is provided on the piezoelectric film surface 501 of the piezoelectric film 50 formed on the lower electrode surface 611, and is sandwiched between the piezoelectric film 50 and the upper electrode film 62.

[0047] The insulating film 80 is formed in a position overlapping from one end of the lower layer first slit 612 in the slit direction D2 to the other end of the lower layer first slit 612 in the stacking direction D1. Furthermore, as shown in Fig. 1, the insulating film 80 overlaps with the entire lower layer first slit 612 in the stacking direction D1 in a cross section cut in the stacking direction D1, and is formed across the lower layer first slit 612. In other words, the insulating film 80 covers the entire lower layer first slit 612 in the cross section shown in Fig. 1 when viewed from the stacking direction D1.

[0048] The insulating film 80 is formed so that the size in the slit width direction D3 is larger than the size in the slit width direction D3 of the lower layer first slit 612. However, the insulating film 80 is formed at a position not overlapping with the upper layer first slit 622 in the stacking direction D1 in the cross section shown in FIG.

[0049] Here, the insulating film 80 has a first extension portion 80a that does not overlap the lower layer first slit 612 in the stacking direction D1 on one side of the slit width direction D3 in the cross section shown in Fig. 1. Also, the insulating film 80 has a second extension portion 80b that does not overlap the lower layer first slit 612 in the stacking direction D1 on the other side of the slit width direction D3 in the cross section shown in Fig. 1.

[0050] The first expansion portion 80a has a first expansion width L1, which is the size in the slit width direction D3, set to be four or more times the piezoelectric film thickness t, which is the dimension in the stacking direction D1 of the piezoelectric film 50. The second expansion portion 80b has a second expansion width L2, which is the size in the slit width direction D3, set to be four or more times the piezoelectric film thickness t. In FIG. 1, in order to make the piezoelectric film 50 easier to see, the dimension in the stacking direction D1 of the piezoelectric film 50 is shown enlarged compared to the dimension in the stacking direction D1 of the first expansion portion 80a and the second expansion portion 80b.

[0051] The insulating film 80 is made of a material different from the support 10, and has a higher electrical resistance value than the piezoelectric film 50 and a lower dielectric constant than the piezoelectric film 50. For example, the insulating film 80 is solidified in an amorphous state in which atoms are irregularly arranged, and is made of an amorphous film having a relatively low defect density or no defects. Specifically, the insulating film 80 is made of silicon nitride, i.e., SiN, aluminum oxide, i.e., Al2O3, aluminum nitride, i.e., ALN, silicon dioxide, i.e., SiO2, and the like. The insulating film 80 is formed on the piezoelectric film surface 501 by a sputtering method, a CVD (short for Chemical Vapor Deposition) method, or the like.

[0052] A plurality of insulating films 80 are formed at positions corresponding to the lower layer first slits 612 formed in the lower layer electrode film 61 in each of the first vibrating region 22a to the fourth vibrating region 22d. That is, the insulating films 80 formed in each of the first vibrating region 22a to the fourth vibrating region 22d are distributed in an island shape and formed apart from each other at positions corresponding to the portions where the lower layer first slits 612 are formed in each of the first vibrating region 22a to the fourth vibrating region 22d. The upper layer electrode film 62 of each of the first vibrating region 22a to the fourth vibrating region 22d is provided on the piezoelectric film surface 501 across the insulating films 80 provided in each of the first vibrating region 22a to the fourth vibrating region 22d.

[0053] In the piezoelectric element 1 configured as above, when sound pressure is applied to the first vibration region 22a to the fourth vibration region 22d, which are the sensing section 30, the first vibration region 22a to the fourth vibration region 22d vibrate. In this case, for example, when the second region R2 side, i.e., the free end side, of each of the first vibration region 22a to the fourth vibration region 22d is displaced upward, a tensile stress is generated in a lower part of the piezoelectric film 50, and a compressive stress is generated in an upper part of the piezoelectric film 50. Therefore, the sound pressure is detected by extracting the electric charge between the lower electrode film 61 and the upper electrode film 62 provided in each of the first vibration region 22a to the fourth vibration region 22d.

[0054] Furthermore, the piezoelectric element 1 is configured in a cantilever support structure in which the first region R1 side is a fixed end and the tip portion on the second region R2 side is a free end in the first vibration region 22a to the fourth vibration region 22d. Therefore, the stress generated in the piezoelectric film 50 provided in each of the first vibration region 22a to the fourth vibration region 22d can improve the detection sensitivity of sound pressure compared to a case not configured in a cantilever support structure.

[0055] Also, the lower layer first slits 612 and the upper layer first slits 622 are formed shifted in the slit width direction D3 so as not to overlap with each other in the stacking direction D1. Therefore, the rigidity of the sensing section 30 is less likely to decrease compared to when the lower layer first slits 612 and the upper layer first slits 622 are formed at positions where they overlap with each other in the stacking direction D1. Therefore, the sensing section 30 is less likely to be damaged when each of the first vibrating region 22a to the fourth vibrating region 22d is displaced.

[0056] Incidentally, the piezoelectric film 50 of this embodiment is made of scandium aluminum nitride. The piezoelectric film 50 is formed across the lower layer first slits 612 on the lower layer electrode surface 611 of the lower layer electrode film 61 formed by etching using molybdenum. Therefore, when the piezoelectric film 50 made of a material different from the lower layer electrode film 61 is formed on the lower layer electrode surface 611, the crystal growth of the piezoelectric film 50 is not stable when the piezoelectric film 50 is crystallized in the portion formed across the lower layer first slits 612. Therefore, in the piezoelectric film 50, abnormal crystal grains are generated in the portion across the lower layer first slits 612, and a crystalline abnormal portion D is generated.

[0057] The crystalline abnormality D caused by the generation of abnormal crystal grains diffuses and occurs away from the center of the lower layer first slit 612 with respect to the edge of the lower layer first slit 612 as a reference as the farther it is from the lower layer first slit 612 in the stacking direction D1. In other words, the crystalline abnormality D spreads radially from the portion of the lower layer electrode surface 611 where the lower layer first slit 612 is formed toward the upper layer electrode film 62. The dashed lines shown in FIG. 1 indicate the crystalline abnormality D generated in the piezoelectric film 50.

[0058] The occurrence of such crystalline abnormality D reduces the electrical resistance between the lower electrode film 61 and the upper electrode film 62, causing a leak current to flow between the lower electrode film 61 and the upper electrode film 62. When a leak current flows between the lower electrode film 61 and the upper electrode film 62, the dielectric tangent of the piezoelectric element 1, i.e., the dielectric loss, deteriorates, causing a deterioration in the detection sensitivity of the sound pressure of the piezoelectric element 1. Furthermore, while the piezoelectric film 50 of this embodiment is made of scandium aluminum nitride, when scandium aluminum nitride is formed on the lower electrode surface 611 made of molybdenum, the higher the concentration of scandium, the more likely the crystalline abnormality D is to occur.

[0059] The dielectric tangent tan δ of the piezoelectric element 1 is expressed by the following formula 1.

[0060] (Number 1) tan δ=1 / ω×Rp×Cp In Formula 1, ω represents the angular frequency of the electric field generated between the lower electrode film 61 and the upper electrode film 62. Rp represents the electrical resistance of the piezoelectric element 1. Cp represents the electrostatic capacitance of the piezoelectric element 1. The dielectric tangent tan δ of the piezoelectric element 1 expressed in Formula 1 decreases as the electrical resistance Rp of the piezoelectric element 1, i.e., the electrical resistance between the lower electrode film 61 and the upper electrode film 62, increases.

[0061] In contrast, in this embodiment, an insulating film 80 that increases the electrical resistance value between the lower electrode film 61 and the upper electrode film 62 is provided between the lower electrode surface 611 and the upper electrode film 62 at a position overlapping with the lower first slit 612 in the stacking direction D1.

[0062] According to this, the insulating film 80 can increase the electrical resistance value between the lower electrode film 61 and the upper electrode film 62 in the portion of the piezoelectric film 50 that overlaps with the lower first slit 612 in the stacking direction D1. Therefore, even if a crystalline abnormality D occurs in a portion of the piezoelectric film 50 that spans the lower first slit 612, deterioration of the dielectric tangent tan δ of the piezoelectric film 50 can be reduced. Therefore, the detection sensitivity of the sound pressure of the piezoelectric element 1 can be improved compared to a case in which the insulating film 80 is not provided.

[0063] In particular, the piezoelectric element 1 of this embodiment is configured such that the crystalline abnormality D is likely to occur due to the piezoelectric film 50 being made of scandium aluminum nitride having a relatively high concentration of scandium. However, by providing the insulating film 80 between the lower electrode film 61 and the upper electrode film 62, it is possible to reduce deterioration in the dielectric tangent tan δ of the piezoelectric film 50. Therefore, by making the concentration of scandium relatively high, it is possible to improve the detection sensitivity of the sound pressure of the piezoelectric element 1, while suppressing a decrease in the detection sensitivity of the sound pressure of the piezoelectric element 1 caused by making the concentration of scandium relatively high.

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

[0065] (1) In the above embodiment, the insulating film 80 is provided on the piezoelectric film surface 501. The upper electrode film 62 is provided on the piezoelectric film surface 501 across the insulating film 80.

[0066] According to this, the insulating film 80 can be disposed on the piezoelectric element 1 more easily than in a configuration in which the insulating film 80 is formed inside the piezoelectric film 50 .

[0067] (2) In the above embodiment, the insulating film 80 has a first extension portion 80a that does not overlap the lower layer first slit 612 in the stacking direction D1 on one side in the slit width direction D3 perpendicular to the stacking direction D1 in the cross section shown in Fig. 1. Furthermore, the insulating film 80 has a second extension portion 80b that does not overlap the lower layer first slit 612 in the stacking direction D1 on the other side in the slit width direction D3. The first extension portion 80a and the second extension portion 80b are formed so that the size in the slit width direction D3 is four or more times the dimension in the stacking direction D1 of the piezoelectric film 50 on which the insulating film 80 is provided.

[0068] Incidentally, the crystalline abnormality D caused by abnormal crystal grains occurring in the piezoelectric film 50 diffuses and occurs away from the center of the lower layer first slit 612 with respect to the edge of the lower layer first slit 612 as the crystalline abnormality D occurs in the stacking direction D1. For this reason, the crystalline abnormality D occurring in the piezoelectric film 50 has a larger cross-sectional area in a cross section perpendicular to the stacking direction D1 as the crystalline abnormality D occurs closer to the upper layer electrode film 62.

[0069] Then, when the crystalline abnormality portion D reaches the upper electrode film 62 from the lower first slit 612, the cross-sectional area of ​​the crystalline abnormality portion D perpendicular to the stacking direction D1 becomes maximum. According to the inventor's careful study, it was found that the distance in the slit width direction D3 from the edge of the lower first slit 612 to the end of the crystalline abnormality portion D when the crystalline abnormality portion D reaches the upper electrode film 62 is about four times the piezoelectric film thickness t.

[0070] It has also been found that in the piezoelectric film 50 in which crystalline abnormality D occurs due to diffusion toward the upper electrode film 62, the greater the area that the insulating film 80 covers at the site where the crystalline abnormality D occurs, the greater the electrical resistance value between the lower electrode film 61 and the upper electrode film 62.

[0071] FIG. 4 shows the experimental results of measuring the electrical resistance between the lower electrode film 61 and the upper electrode film 62 when the insulating film 80 is provided on the piezoelectric film surface 501 and the cross-sectional area perpendicular to the stacking direction D1 of the insulating film 80 is changed.

[0072] In this experiment, a case in which the size of the lower layer first slit 612 in the slit width direction D3 is set equal to the size of the insulating film 80 in the slit width direction D3 was used as a reference. Then, the change in the electrical resistance value between the lower layer electrode film 61 and the upper layer electrode film 62 was measured when the size of the insulating film 80 in the slit width direction D3 was changed relative to the size of the lower layer first slit 612 in the slit width direction D3.

[0073] 4, when the size of the insulating film 80 in the slit width direction D3 is small relative to the size of the lower layer first slit 612 in the slit width direction D3, the electrical resistance value between the lower layer electrode film 61 and the upper layer electrode film 62 becomes smaller than the reference value. Also, when the size of the insulating film 80 in the slit width direction D3 is large relative to the size of the lower layer first slit 612 in the slit width direction D3, the electrical resistance value between the lower layer electrode film 61 and the upper layer electrode film 62 becomes larger than the reference value. That is, when the insulating film 80 has a first extension portion 80a and a second extension portion 80b that do not overlap the lower layer first slit 612 in the stacking direction D1 as in this embodiment, the electrical resistance value between the lower layer electrode film 61 and the upper layer electrode film 62 can be made larger than the reference value.

[0074] When the first expansion width L1 and the second expansion width L2 are set to four times the dimension in the stacking direction D1 of the piezoelectric film 50, i.e., the piezoelectric film thickness t, the electrical resistance between the lower electrode film 61 and the upper electrode film 62 becomes approximately the maximum value. In other words, the insulating film 80 having the first expansion portion 80a and the second expansion portion 80b covers the entire range in which the crystalline abnormality portion D is formed on the piezoelectric film surface 501, so that the electrical resistance Rp of the piezoelectric element 1 can be approximately maximized.

[0075] When the first expansion width L1 and the second expansion width L2 are set to be greater than four times the piezoelectric film thickness t, the electrical resistance between the lower electrode film 61 and the upper electrode film 62 becomes substantially constant. For this reason, the first expansion portion 80a and the second expansion portion 80b are formed so that the size in the slit width direction D3 is four times or more the dimension in the stacking direction D1 of the piezoelectric film 50 on which the insulating film 80 is provided. In this embodiment, the first expansion portion 80a and the second expansion portion 80b are not formed so that the size in the slit width direction D3 is larger than necessary. The first expansion portion 80a and the second expansion portion 80b are formed so that the size in the slit width direction D3 is 100 times or less the dimension in the stacking direction D1 of the piezoelectric film 50 on which the insulating film 80 is provided.

[0076] Therefore, according to this embodiment, it is possible to further reduce the deterioration of the dielectric tangent tanδ caused by the crystalline abnormality D of the piezoelectric film 50, compared to the case where the first expansion width L1 and the second expansion width L2 are set to be smaller than four times the piezoelectric film thickness t. Also, by not making the size of the first expansion portion 80a and the second expansion portion 80b in the slit width direction D3 larger than necessary, it is possible to ensure the effective range of each of the electrodes of the lower electrode film 61 and the upper electrode film 62.

[0077] (3) In the above embodiment, the insulating film 80 is made of a material different from the support body 10, and is formed at a position corresponding to the portion where the lower layer first slit 612 is to be formed.

[0078] Incidentally, the piezoelectric element 1 may be deformed by changes in external temperature, and may warp in the stacking direction D1 due to the difference in thermal expansion coefficient between the support 10 and the insulating film 80, which are made of different materials. In response to this, by forming the insulating film 80 only in the portion corresponding to the lower layer first slit 612, warping of the piezoelectric element 1 can be suppressed when the piezoelectric element 1 is deformed by changes in external temperature, compared to the case where the insulating film 80 is formed on the entire piezoelectric film surface 501. Therefore, with the above-mentioned configuration of the piezoelectric element 1 of this embodiment, it is possible to suppress variations in the detection results of sound pressure caused by changes in external temperature, and to increase the detection sensitivity of the sound pressure of the piezoelectric element 1.

[0079] (4) In the above embodiment, the insulating film 80 includes an amorphous film having an amorphous structure.

[0080] According to this, the crystalline abnormality D occurring in the portion of the piezoelectric film 50 spanning the lower layer first slit 612 is less likely to propagate in the stacking direction D1 than when the insulating film 80 does not include an amorphous film. Therefore, it is possible to further reduce the deterioration of the dielectric loss tangent tanδ of the piezoelectric film 50 caused by the crystalline abnormality D occurring in the portion of the piezoelectric film 50 spanning the lower layer first slit 612.

[0081] To manufacture the piezoelectric element 1 of this embodiment, first, a support 10 having an insulating layer 12 disposed on a support substrate 11 is prepared, and a seed layer 31, a lower electrode film 61, and a piezoelectric film 50 are formed in this order on the support 10. The lower electrode film 61 is made of molybdenum. The piezoelectric film 50 is made of scandium aluminum nitride, which has a relatively high concentration of scandium.

[0082] Then, an insulating film 80 is formed by patterning on the piezoelectric film surface 501 of the piezoelectric film 50 at a position overlapping with the lower layer first slit 612 in the stacking direction D1, and an upper layer electrode film 62 is formed on the piezoelectric film surface 501 across the insulating film 80. The insulating film 80 is made of silicon nitride, aluminum oxide, aluminum nitride, and silicon dioxide. The upper layer electrode film 62 is made of molybdenum. The lower layer electrode film 61 and the upper layer electrode film 62 are formed by a general etching method or the like. The piezoelectric film 50 and the insulating film 80 are formed by a general sputtering method, CVD method, or the like. In this way, the above-mentioned piezoelectric element 1 in which the vibration part 20 is arranged on the support 10 is manufactured.

[0083] (Modification of the first embodiment) In the above-described first embodiment, an example in which the insulating film 80 is made of silicon nitride, aluminum oxide, aluminum nitride, silicon dioxide, etc. has been described, but the present invention is not limited to this. For example, the insulating film 80 may be configured to be formed by stacking any two or more members selected from silicon nitride, aluminum oxide, aluminum nitride, and silicon dioxide.

[0084] Second embodiment Next, a second embodiment will be described with reference to FIG. 5. In this embodiment, the configuration of the piezoelectric film 50 and the position where the insulating film 80 is formed are different from those in the first embodiment. Other than this, the second embodiment is similar to the first embodiment. Therefore, in this embodiment, the parts different from the first embodiment will be mainly described, and the description of the parts similar to the first embodiment may be omitted.

[0085] The piezoelectric film 50 of this embodiment is divided into a lower piezoelectric film 51 provided on the lower electrode surface 611 and an upper piezoelectric film 52 laminated on the lower piezoelectric film 51. That is, the piezoelectric film 50 has the lower piezoelectric film 51 and the upper piezoelectric film 52 formed side by side in the lamination direction D1. That is, the lower piezoelectric film 51 and the upper piezoelectric film 52 in the vibration part 20 are sandwiched between the lower electrode film 61 and the upper electrode film 62.

[0086] In the sensing unit 30 of this embodiment, the first vibration region 22a to the fourth vibration region 22d have a bimorph structure, and a lower piezoelectric film 51 and an upper piezoelectric film 52 are formed in each of the first vibration region 22a to the fourth vibration region 22d. The lower piezoelectric film 51 and the upper piezoelectric film 52 formed in each of the first vibration region 22a to the fourth vibration region 22d have substantially equal dimensions in the stacking direction D1. The dimensions in the stacking direction D1 of the lower piezoelectric film 51 and the upper piezoelectric film 52 are substantially half the dimensions in the stacking direction D1 of the piezoelectric film 50 of the first embodiment.

[0087] Each of the lower piezoelectric films 51 formed in the first vibrating region 22a to the fourth vibrating region 22d has a lower piezoelectric film surface 511 on the side opposite to the lower electrode surface 611. Each of the upper piezoelectric films 52 formed in the first vibrating region 22a to the fourth vibrating region 22d has an upper piezoelectric film surface 521 on the side opposite to the lower piezoelectric film surface 511. The lower piezoelectric film 51 of this embodiment corresponds to the first piezoelectric film, the lower piezoelectric film surface 511 corresponds to the first piezoelectric film surface, and the upper piezoelectric film 52 corresponds to the second piezoelectric film.

[0088] The insulating film 80 of this embodiment is provided between the lower electrode film 61 and the upper electrode film 62 formed in each of the first vibrating region 22a to the fourth vibrating region 22d, at a position overlapping with the lower first slit 612 in the stacking direction D1. Specifically, the insulating film 80 is formed in a substantially planar thin film shape on the lower piezoelectric film surface 511 formed in each of the first vibrating region 22a to the fourth vibrating region 22d, at a position away from the lower electrode surface 611. Similarly to the first embodiment, the insulating film 80 is configured to include an amorphous film.

[0089] 5, in a cross section cut in the stacking direction D1, the insulating film 80 overlaps with the entire lower layer first slit 612 in the stacking direction D1 and is formed across the lower layer first slit 612. In addition, as shown in the cross section shown in FIG. 5, the insulating film 80 has a first extension portion 80a and a second extension portion 80b.

[0090] The first expansion portion 80a is formed so that the first expansion width L1 is four or more times the first piezoelectric film thickness t1, which is the dimension in the stacking direction D1 of the lower piezoelectric film 51. The second expansion portion 80b is formed so that the second expansion width L2 is four or more times the first piezoelectric film thickness t1. However, the first expansion width L1 and the second expansion width L2 in the insulating film 80 of this embodiment are formed smaller than the first expansion width L1 and the second expansion width L2 in the insulating film 80 of the first embodiment.

[0091] Similarly to the first embodiment, the lower piezoelectric film 51 and the upper piezoelectric film 52 are made of scandium aluminum nitride. The lower piezoelectric film 51 and the upper piezoelectric film 52 have approximately the same mass of scandium per unit mass. That is, the lower piezoelectric film 51 and the upper piezoelectric film 52, which are made of scandium aluminum nitride, have approximately the same concentration of scandium.

[0092] The upper-layer piezoelectric film 52 of each of the first vibrating region 22a to the fourth vibrating region 22d is provided on the lower-layer piezoelectric film surface 511, straddling the insulating film 80 provided on each of the first vibrating region 22a to the fourth vibrating region 22d. The upper-layer electrode film 62 of each of the first vibrating region 22a to the fourth vibrating region 22d is formed on the upper-layer piezoelectric film surface 521.

[0093] 5, when cut in the stacking direction D1 through the lower layer first slits 612. The upper layer piezoelectric film 52 is provided on the lower layer piezoelectric film surface 511 across the insulating film 80.

[0094] According to this, by forming the insulating film 80 on the lower piezoelectric film surface 511 of the lower piezoelectric film 51, the insulating film 80 can be placed closer to the lower first slit 612 than in a configuration in which it is formed on the upper piezoelectric film surface 521.

[0095] As described in the first embodiment, the crystalline abnormality D occurring in the portion straddling the lower layer first slit 612 radially diffuses from the edge of the lower layer first slit 612 as it moves away from the lower layer first slit 612 in the stacking direction D1. The cross-sectional area of ​​the crystalline abnormality D perpendicular to the stacking direction D1 increases as it moves away from the lower layer first slit 612.

[0096] Therefore, when the insulating film 80 is formed so as to cover the entire diffusion range of the crystalline abnormality portion D that is generated by diffusion, the size of the insulating film 80 in the slit width direction D3 needs to be increased the farther the position at which the insulating film 80 is positioned is from the lower layer first slit 612.

[0097] In contrast to this, in this embodiment, by forming the insulating film 80 on the lower piezoelectric film surface 511, the insulating film 80 can be brought closer to the lower first slits 612 than when it is formed on the upper piezoelectric film surface 521. As a result, when the insulating film 80 is formed so as to overlap the entire lower first slits 612 in the stacking direction D1, the cross-sectional area of ​​the insulating film 80 perpendicular to the stacking direction D1 can be made smaller than when it is formed on the upper piezoelectric film surface 521.

[0098] This makes it possible to increase the area where the lower electrode film 61 and the upper electrode film 62 face each other without sandwiching the insulating film 80. In other words, the effective area of ​​each of the electrodes of the lower electrode film 61 and the upper electrode film 62 can be increased.

[0099] Furthermore, by forming the insulating film 80 on the lower piezoelectric film surface 511, when a crystalline abnormality D occurs from the lower electrode film 61 toward the upper electrode film 62, the crystalline abnormality D is less likely to occur above a portion of the upper piezoelectric film 52 that straddles the insulating film 80. That is, even if a crystalline abnormality D occurs in the lower piezoelectric film 51, a leak current is less likely to flow from the lower electrode film 61 to the upper electrode film 62. Therefore, the capacitance between the lower electrode film 61 and the upper electrode film 62 can be ensured while reducing deterioration of the dielectric loss tangent tan δ caused by the crystalline abnormality D of the lower piezoelectric film 51.

[0100] In order to manufacture the piezoelectric element 1 of this embodiment, the lower piezoelectric film 51, the insulating film 80, and the upper piezoelectric film 52 are formed in this order on the lower electrode film 61, thereby achieving the above-mentioned configuration in which the vibration part 20 is arranged on the support 10.

[0101] (First modified example of the second embodiment) In the above-described second embodiment, the insulating film 80 is formed in a substantially planar thin film shape, but the present invention is not limited thereto. For example, the insulating film 80 may have an insulating recess 80c recessed toward the lower layer first slit 612 as shown in FIG. 6. That is, the insulating film 80 may be formed in a wedge shape.

[0102] As a result, the insulating recess 80c increases the electrical resistance value in a planar direction perpendicular to the stacking direction D1 in the area where the crystalline abnormality D occurs in the lower piezoelectric film 51, thereby suppressing leakage current from flowing in the planar direction.

[0103] (Second Modification of the Second Embodiment) In the above-described second embodiment, an example in which the insulating film 80 is configured to include an amorphous film has been described, but the present invention is not limited to this. For example, the insulating film 80 may be configured to include a material that allows the crystal structure of the upper-layer piezoelectric film 52 to be self-oriented. For example, the insulating film 80 may be configured to include a material such as silicon nitride, aluminum oxide, silicon dioxide, or tantalum pentoxide.

[0104] This can improve the electrical resistance value of the upper-layer piezoelectric film 52 compared to a configuration in which the insulating film 80 does not include a component that allows the crystal structure of the upper-layer piezoelectric film 52 to self-orient. Therefore, it is possible to further reduce the deterioration of the dielectric loss tangent tanδ of the piezoelectric film 50 caused by the crystalline abnormality D occurring in the portion of the piezoelectric film 50 spanning the lower-layer first slit 612.

[0105] (Third modified example of the second embodiment) In the above-mentioned second embodiment, an example in which the insulating film 80 is formed on the planar lower piezoelectric film surface 511 has been described, but the present invention is not limited thereto. For example, as shown in Fig. 7, the insulating film 80 may be configured to fill a piezoelectric film recess 513 forming a piezoelectric film space 512 recessed toward the lower electrode surface 611 on the lower piezoelectric film surface 511. In this case, the insulating film 80 may be configured to form a plane continuous with a surface different from the piezoelectric film recess 513 on the lower piezoelectric film surface 511 by a CMP (short for Chemical Mechanical Polisher) method, an etch-back method, or the like.

[0106] According to this, the area where the upper piezoelectric film 52 is formed becomes a continuous plane shape, which suppresses the occurrence of crystal abnormalities when the upper piezoelectric film 52 is crystallized, thereby reducing deterioration of the dielectric loss tangent tan δ.

[0107] (Fourth Modification of the Second Embodiment) In the above-described second embodiment, an example has been described in which the dimensions of the lower-layer piezoelectric film 51 and the upper-layer piezoelectric film 52 in the stacking direction D1 are approximately equal to each other, but the present invention is not limited to this. For example, the dimensions of the lower-layer piezoelectric film 51 and the upper-layer piezoelectric film 52 in the stacking direction D1 may be different from each other. That is, the dimension of the lower-layer piezoelectric film 51 in the stacking direction D1 may be smaller or larger than the dimension of the upper-layer piezoelectric film 52 in the stacking direction D1.

[0108] Third embodiment Next, a third embodiment will be described with reference to FIG. 8. This embodiment differs from the second embodiment in that the lower piezoelectric film 51 and the upper piezoelectric film 52 have different scandium concentrations. The rest of the embodiment is similar to the second embodiment. Therefore, in this embodiment, the differences from the second embodiment will be mainly described, and the description of the similarities between the second embodiment and the third embodiment may be omitted.

[0109] In the piezoelectric film 50 of this embodiment, the lower piezoelectric film 51 and the upper piezoelectric film 52 are made of scandium aluminum nitride containing scandium. The lower piezoelectric film 51 and the upper piezoelectric film 52 are formed to have different concentrations of scandium. Specifically, as shown in FIG. 8, the amount of scandium per unit mass of the lower piezoelectric film 51 is smaller than the amount of scandium per unit mass of the upper piezoelectric film 52. That is, the lower piezoelectric film 51 has a lower scandium concentration than the upper piezoelectric film 52. The scandium concentration of the lower piezoelectric film 51 of this embodiment is lower than the scandium concentrations of the lower piezoelectric film 51 and the upper piezoelectric film 52 of the second embodiment.

[0110] 8, the difference in scandium concentration is represented by the difference in hatching pitch. The lower piezoelectric film 51, which has a larger hatching pitch, has a lower scandium concentration than the upper piezoelectric film 52, which has a smaller hatching pitch.

[0111] Incidentally, as described in the first embodiment, the sound pressure detection sensitivity of the piezoelectric element 1 is more easily improved as the mass of scandium contained per unit mass of the piezoelectric film 50 is increased. However, in the piezoelectric element 1, the crystallinity abnormality D is more likely to occur in a portion of the piezoelectric film 50 that spans the lower layer first slit 612 as the amount of scandium per unit mass of the piezoelectric film 50 increases.

[0112] In contrast, in the piezoelectric element 1 of this embodiment, the amount of scandium per unit mass of the lower-layer piezoelectric film 51 configured to straddle the lower-layer first slit 612 is smaller than the amount of scandium per unit mass of the upper-layer piezoelectric film 52. This makes it possible to suppress the occurrence of crystalline abnormalities D in the portions of the lower-layer piezoelectric film 51 that straddle the lower-layer first slit 612. This makes it possible to reduce deterioration in dielectric loss tangent tan δ caused by crystalline abnormalities D occurring in the lower-layer piezoelectric film 51, compared to a configuration in which the amount of scandium per unit mass of the lower-layer piezoelectric film 51 is larger than the amount of scandium per unit mass of the upper-layer piezoelectric film 52.

[0113] (Modification of the third embodiment) In the above-described third embodiment, an example has been described in which the amount of scandium per unit mass of the lower piezoelectric film 51 is smaller than the amount of scandium per unit mass of the upper piezoelectric film 52. However, the present invention is not limited to this. The amount of scandium per unit mass of the lower piezoelectric film 51 may be larger than the amount of scandium per unit mass of the upper piezoelectric film 52.

[0114] (Fourth embodiment) Next, the fourth embodiment will be described with reference to FIG. 9. In this embodiment, the configuration of the piezoelectric film 50 is different from that of the second and third embodiments. Other than this, the fourth embodiment is similar to the second and third embodiments. Therefore, in this embodiment, the parts different from the second and third embodiments will be mainly described, and the description of the parts similar to the second and third embodiments may be omitted.

[0115] The piezoelectric film 50 of this embodiment has a lower piezoelectric film 51, an upper piezoelectric film 52, and an intermediate piezoelectric film 53 provided between the lower piezoelectric film 51 and the upper piezoelectric film 52. That is, the piezoelectric film 50 is formed by arranging the lower piezoelectric film 51, the intermediate piezoelectric film 53, and the upper piezoelectric film 52 in this order in the stacking direction D1. That is, the vibration section 20 is in a state in which the lower piezoelectric film 51, the intermediate piezoelectric film 53, and the upper piezoelectric film 52 are sandwiched between the lower electrode film 61 and the upper electrode film 62.

[0116] The dimension of the intermediate piezoelectric film 53 in the stacking direction D1 is smaller than the dimensions of the lower piezoelectric film 51 and the upper piezoelectric film 52 in the stacking direction D1. The dimensions of the lower piezoelectric film 51 and the upper piezoelectric film 52 in the stacking direction D1 are substantially equal to each other. The sum of the dimensions of the lower piezoelectric film 51, the intermediate piezoelectric film 53 and the upper piezoelectric film 52 in the stacking direction D1 is the dimension of the piezoelectric film 50 of the first embodiment in the stacking direction D1.

[0117] The lower piezoelectric film 51 has a lower piezoelectric film surface 511 on the side opposite to the lower electrode surface 611. The middle piezoelectric film 53 has a middle piezoelectric film surface 531 on the side opposite to the lower piezoelectric film surface 511. The upper piezoelectric film 52 has an upper piezoelectric film surface 521 on the side opposite to the middle piezoelectric film surface 531. In this embodiment, the lower piezoelectric film 51 corresponds to the first piezoelectric film, the lower piezoelectric film surface 511 corresponds to the first piezoelectric film surface, the middle piezoelectric film 53 corresponds to the second piezoelectric film, the middle piezoelectric film surface 531 corresponds to the second piezoelectric film surface, and the upper piezoelectric film 52 corresponds to the third piezoelectric film.

[0118] The insulating film 80 of this embodiment is provided between the lower electrode film 61 and the upper electrode film 62 at a position overlapping with the lower first slit 612 in the stacking direction D1. Specifically, the insulating film 80 is formed on the lower piezoelectric film surface 511 at a position away from the lower electrode surface 611 in a substantially planar thin film shape.

[0119] 9, in a cross section cut in the stacking direction D1, the insulating film 80 overlaps with the entire lower layer first slit 612 in the stacking direction D1 and is formed across the lower layer first slit 612.

[0120] Similarly to the second embodiment, the lower piezoelectric film 51, the intermediate piezoelectric film 53 and the upper piezoelectric film 52 are made of scandium aluminum nitride. The lower piezoelectric film 51 and the intermediate piezoelectric film 53 are formed to have different concentrations of scandium compared to the upper piezoelectric film 52. Specifically, the amount of scandium per unit mass of the lower piezoelectric film 51 and the intermediate piezoelectric film 53 is less than the amount of scandium per unit mass of the upper piezoelectric film 52.

[0121] That is, the lower piezoelectric film 51 and the middle piezoelectric film 53 have a lower concentration of scandium than the upper piezoelectric film 52. The lower piezoelectric film 51 and the middle piezoelectric film 53 also have approximately the same mass of scandium contained per unit mass. That is, the lower piezoelectric film 51 and the middle piezoelectric film 53 have approximately the same concentration of scandium.

[0122] The upper piezoelectric film 52 is provided on the intermediate piezoelectric film surface 531, straddling the insulating film 80. The upper electrode film 62 is formed on the upper piezoelectric film surface 521.

[0123] Thus, in the piezoelectric element 1 of this embodiment, the insulating film 80 is provided on the lower layer piezoelectric film surface 511, and in a cross section cut through the lower layer first slit 612 in the stacking direction D1, it overlaps with the entire lower layer first slit 612 in the stacking direction D1.

[0124] This allows the insulating film 80 to be closer to the lower first slits 612 than in a configuration in which the insulating film 80 is formed on the intermediate piezoelectric film surface 531 or the upper piezoelectric film surface 521. Therefore, when the insulating film 80 is formed so as to overlap the entire lower first slits 612 in the stacking direction D1, the cross-sectional area of ​​the insulating film 80 perpendicular to the stacking direction D1 can be made smaller than in a configuration in which the insulating film 80 is formed on the intermediate piezoelectric film surface 531 or the upper piezoelectric film surface 521.

[0125] Therefore, the area where the lower electrode film 61 and the upper electrode film 62 face each other and do not sandwich the insulating film 80 can be increased. That is, the effective areas of the electrodes of the lower electrode film 61 and the upper electrode film 62 can be expanded. Therefore, the capacitance between the lower electrode film 61 and the upper electrode film 62 can be ensured while reducing the deterioration of the dielectric loss tangent tan δ caused by the crystalline abnormality D of the piezoelectric film 50.

[0126] Furthermore, according to the above embodiment, the following effects can be obtained.

[0127] (1) In the above embodiment, the lower piezoelectric film 51, the intermediate piezoelectric film 53, and the upper piezoelectric film 52 contain scandium. The amount of scandium per unit mass of the lower piezoelectric film 51 is smaller than the amount of scandium per unit mass of the upper piezoelectric film 52, which is one of the intermediate piezoelectric film 53 and the upper piezoelectric film 52.

[0128] This makes it possible to reduce the occurrence of crystalline abnormalities D in the upper piezoelectric film 52, as compared with a configuration in which the amount of scandium per unit mass of the lower piezoelectric film 51 is greater than the amount of scandium per unit mass of the upper piezoelectric film 52. As a result, deterioration of the dielectric loss tangent tan δ of the piezoelectric element 1 can be reduced.

[0129] Furthermore, in this embodiment, the amount of scandium per unit mass of the intermediate piezoelectric film 53 is also smaller than the amount of scandium per unit mass of the upper piezoelectric film 52. Therefore, the generation of crystalline abnormalities D during crystallization of the intermediate piezoelectric film 53 can be suppressed more effectively than in a configuration in which the amount of scandium per unit mass of the intermediate piezoelectric film 53 is larger than the amount of scandium per unit mass of the upper piezoelectric film 52. Therefore, the crystallinity of the upper electrode film 62 formed on the intermediate piezoelectric film surface 531 can be improved.

[0130] (First modified example of the fourth embodiment) In the above-mentioned fourth embodiment, an example in which the insulating film 80 is formed on the planar lower piezoelectric film surface 511 has been described, but the present invention is not limited thereto. For example, as shown in FIG. 10, the lower piezoelectric film 51 may have a piezoelectric film recess 513 on the lower piezoelectric film surface 511, which forms a piezoelectric film space 512 recessed toward the lower electrode surface 611. Specifically, the piezoelectric film recess 513 has a large recess 513a whose size in the slit width direction D3 is larger than that of the lower layer first slit 612, and a small recess 513b whose size in the slit width direction D3 is smaller than that of the lower layer first slit 612. That is, the large recess 513a is formed to be larger in size in the slit width direction D3 than the small recess 513b.

[0131] The large depression 513a and the small depression 513b are formed side by side in this order in the stacking direction D1 from the intermediate piezoelectric film 53 side toward the lower electrode film 61 side. The large depression 513a is located in a portion that does not overlap with the lower layer first slit 612 in the stacking direction D1. All of the small depressions 513b overlap with the lower layer first slits 612 in the stacking direction D1.

[0132] The insulating film 80 is provided in the piezoelectric film space 512. A portion of the insulating film 80 provided in the large depression 513a overlaps with the lower layer first slit 612 in the stacking direction D1. A portion of the insulating film 80 provided in the small depression 513b overlaps with the lower layer first slit 612 in the stacking direction D1. The insulating film 80 has an insulating surface 80d formed on the side opposite to the piezoelectric film depression 513, which is formed in a plane perpendicular to the stacking direction D1. The insulating surface 80d forms a plane continuous with a surface different from the piezoelectric film depression 513 on the lower piezoelectric film surface 511 by a CMP method, an etch-back method, or the like.

[0133] According to this, the insulating surface 80d on which the intermediate piezoelectric film 53 is formed and a surface different from the piezoelectric film recess 513 on the lower piezoelectric film surface 511 become a continuous plane. That is, the lower piezoelectric film surface 511 and the insulating surface 80d, which are the interface of the crystal growth of the intermediate piezoelectric film 53, become a continuous plane. This makes it possible to suppress the occurrence of crystal abnormalities when the intermediate piezoelectric film 53 crystallizes and improve the crystallinity of the upper electrode film 62, thereby reducing deterioration of the dielectric loss tangent tan δ.

[0134] (Second modified example of the fourth embodiment) In the above-described fourth embodiment, the amount of scandium per unit mass of the lower piezoelectric film 51 and the intermediate piezoelectric film 53 is smaller than the amount of scandium per unit mass of the upper piezoelectric film 52. Also, an example has been described in which the lower piezoelectric film 51 and the intermediate piezoelectric film 53 contain approximately the same amount of scandium per unit mass, but this is not limiting.

[0135] However, this is not limited to the above configuration, so long as the amount of scandium per unit mass of the lower piezoelectric film 51 is smaller than the amount of scandium per unit mass of one of the intermediate piezoelectric film 53 and the upper piezoelectric film 52. The amount of scandium per unit mass of each of the lower piezoelectric film 51, the intermediate piezoelectric film 53, and the upper piezoelectric film 52 may be appropriately set depending on the application of the piezoelectric element 1, etc.

[0136] For example, the concentrations of scandium in the intermediate piezoelectric film 53 and the upper piezoelectric film 52 may be approximately equal to each other. Alternatively, the lower piezoelectric film 51, the intermediate piezoelectric film 53, and the upper piezoelectric film 52 may each have a configuration in which the amount of scandium per unit mass increases in the order of the lower piezoelectric film 51, the intermediate piezoelectric film 53, and the upper piezoelectric film 52.

[0137] Fifth embodiment Next, a fifth embodiment will be described with reference to FIG. 11. This embodiment differs from the first embodiment in that the insulating film 80 is replaced with a gap 81. The rest is the same as the first embodiment. Therefore, in this embodiment, the differences from the first embodiment will be mainly described, and the description of the same parts as the first embodiment may be omitted.

[0138] In this embodiment, as shown in Fig. 11, a gap 81 is formed by covering the piezoelectric film 50 with the upper electrode film 62 formed on the piezoelectric film surface 501 of the piezoelectric film 50. That is, in the piezoelectric element 1 of this embodiment, a gap is formed between the piezoelectric film 50 and the upper electrode film 62. The air present in the gap 81 functions as an insulating material. In this embodiment, the gap 81 corresponds to the insulating portion.

[0139] The gap 81 has a first gap portion 81a that does not overlap the lower layer first slit 612 in the stacking direction D1 on one side of the slit width direction D3 in the cross section shown in Fig. 11. Also, the gap 81 has a second gap portion 81b that does not overlap the lower layer first slit 612 in the stacking direction D1 on the other side of the slit width direction D3 in the cross section shown in Fig. 11. The size of the first gap portion 81a and the second gap portion 81b in the slit width direction D3 is set to be four or more times the dimension of the piezoelectric film 50 in the stacking direction D1.

[0140] Such a gap 81 can be provided on the piezoelectric film surface 501, for example, by forming a sacrificial layer on the piezoelectric film 50, forming an upper electrode film 62 on the formed sacrificial layer, and then removing the sacrificial layer by etching.

[0141] According to this, the gap 81 can increase the electrical resistance value between the lower-layer electrode film 61 and the upper-layer electrode film 62. Therefore, even if a crystalline abnormality D occurs in a portion of the piezoelectric film 50 spanning the lower-layer first slit 612, deterioration of the dielectric tangent tan δ of the piezoelectric film 50 can be reduced. Therefore, the detection sensitivity of the sound pressure of the piezoelectric element 1 can be improved compared to a case where the gap 81 is not provided.

[0142] (Modification of the fifth embodiment) In the above-described fifth embodiment, an example in which the void 81 is formed on the piezoelectric film surface 501 has been described, but the present invention is not limited thereto. For example, the void 81 may be configured to be provided inside the piezoelectric film 50, as shown in FIG. 12. In this case, the insulating film 80 can be formed by removing a part of the piezoelectric film 50 by an etching method using an etching hole (not shown) formed in the piezoelectric film 50 in order to form the insulating film 80.

[0143] (Other embodiments) Representative embodiments of the present disclosure have been described above, but the present disclosure is not limited to the above-described embodiments and can be modified in various ways, for example, as described below.

[0144] In the above-mentioned second and third embodiments, an example has been described in which the electrode film 60 has the lower electrode film 61 arranged on the support surface 121 via the seed layer 31 and the upper electrode film 62 arranged on the upper piezoelectric film surface 521, but the present invention is not limited thereto. For example, as shown in FIG. 13, the electrode film 60 may have a configuration in which the lower electrode film 61 arranged on the support surface 121 via the seed layer 31, the intermediate electrode film 63 arranged on the lower piezoelectric film surface 511, and the upper electrode film 62 arranged on the upper piezoelectric film surface 521. That is, the vibration section 20 may have a configuration in which the lower piezoelectric film 51 is sandwiched between the lower electrode film 61 and the intermediate electrode film 63, and the upper piezoelectric film 52 is sandwiched between the intermediate electrode film 63 and the upper electrode film 62.

[0145] When the electrode film 60 is configured in this manner, the electrode film 60 has a first electrode portion 71 that electrically connects the lower electrode film 61 and the upper electrode film 62, and a second electrode portion 72 that electrically connects the intermediate electrode film 63 and the upper electrode film 62. The upper electrode film 62 has an electrical wiring layer 62d that electrically connects the upper electrode film 62 on which the first electrode portion 71 is provided, and the upper electrode film 62 on which the second electrode portion 72 is provided. In the piezoelectric element 1 configured in this manner, the insulating film 80 may be configured to be provided between a portion of the upper electrode film 62 on which the electrical wiring layer 62d is provided and the lower electrode film 61, at a position that overlaps with the lower layer first slit 612 in the stacking direction D1.

[0146] 13, the insulating film 80 may be formed on the upper layer piezoelectric film surface 521 as long as the insulating film 80 is located at a position that overlaps with the lower layer first slit 612 in the stacking direction D1. Also, the insulating film 80 may be formed on the lower layer piezoelectric film surface 511 (not shown) as long as the insulating film 80 is located at a position that overlaps with the lower layer first slit 612 in the stacking direction D1.

[0147] In the above embodiment, an example has been described in which the insulating film 80 overlaps with the entire lower layer first slit 612 in the stacking direction D1 in a cross section cut in the stacking direction D1, but the present invention is not limited to this. The insulating film 80 may be configured to overlap with a part of the lower layer first slit 612 in the stacking direction D1 in a cross section cut in the stacking direction D1.

[0148] In the above embodiment, the piezoelectric film 50 is configured to contain scandium, but is not limited to this. For example, the piezoelectric film 50 may not contain scandium.

[0149] In the above embodiment, the insulating film 80 has a first extension portion 80a that does not overlap the lower layer first slit 612 in the stacking direction D1 on one side of the slit width direction D3 perpendicular to the stacking direction D1 in a cross section when cut in the stacking direction D1. The insulating film 80 also has a second extension portion 80b that does not overlap the lower layer first slit 612 in the stacking direction D1 on the other side of the slit width direction D3. The first extension portion 80a and the second extension portion 80b have a size in the slit width direction D3 that is four or more times the size in the stacking direction D1 of the piezoelectric film 50 on which the insulating film 80 is provided, but is not limited to this.

[0150] For example, the insulating film 80 may be configured not to have the first extension portion 80a and the second extension portion 80b. That is, the insulating film 80 may be configured such that the size of the insulating film 80 in the slit width direction D3 is smaller than the size of the lower-layer first slit 612 in the slit width direction D3.

[0151] Furthermore, the insulating film 80 may be configured such that the size of the first extension portion 80a and the second extension portion 80b in the slit width direction D3 is less than four times the size of the piezoelectric film 50 on which the insulating film 80 is provided in the stacking direction D1.

[0152] In the above embodiment, the insulating film 80 is formed at a position corresponding to the portion where the lower-layer first slit 612 is formed, but the present invention is not limited to this. For example, the insulating film 80 may be configured to have a size that overlaps with the lower-layer electrode film 61 and the upper-layer electrode film 62 in the stacking direction D1.

[0153] In the above embodiment, the piezoelectric element 1 detects a pressure detection signal corresponding to the sound pressure, but the present invention is not limited to this. For example, the piezoelectric element 1 may be configured to transmit ultrasonic waves and receive reflected waves of the transmitted ultrasonic waves.

[0154] In the above-described embodiments, it goes without saying that the elements constituting the embodiments are not necessarily essential, except in cases where it is particularly expressly stated that they are essential or where they are clearly considered to be essential in principle.

[0155] In the above-described embodiments, when numerical values ​​such as the number, values, amounts, ranges, etc. of components of the embodiments are mentioned, they are not limited to the specific numbers unless it is specifically stated as required or unless it is clearly limited to a specific number in principle.

[0156] In the above-described embodiments, when referring to the shapes, positional relationships, etc. of components, etc., there is no limitation to those shapes, positional relationships, etc., unless specifically stated or in principle limited to a specific shape, positional relationship, etc. [Explanation of symbols]

[0157] 10 Support 20 Vibration section 50 Piezoelectric film 61 1st electrode 62 2nd electrode 80 Insulating film 121 Support surface 501 Piezoelectric film surface 611 1st electrode film 612 Opening

Claims

1. A piezoelectric element, A support (10) having a support surface (121); A vibration part (20) provided on the support surface, the vibration section has a first electrode (61), a piezoelectric film (50), and a second electrode (62) arranged side by side in a stacking direction of the support body and the vibration section, and has an insulating section (80) that increases an electrical resistance value between the first electrode and the second electrode, The first electrode is provided on the support surface, and has an opening (612) formed penetrating in the stacking direction and a first electrode surface (611) formed on the opposite side to the support surface side, The piezoelectric film is provided across the opening on the first electrode surface and has a piezoelectric film surface (501) formed on the opposite side to the first electrode surface, The second electrode is provided on the piezoelectric film surface, The insulating portion is disposed between the first electrode and the second electrode, and at least a portion of the insulating portion overlaps with the opening in the stacking direction.

2. The insulating portion is provided on the piezoelectric film surface, The piezoelectric element according to claim 1 , wherein the second electrode is provided on the piezoelectric film surface across the insulating portion.

3. The piezoelectric film includes a first piezoelectric film (51) and a second piezoelectric film (52) formed side by side in the stacking direction, The first piezoelectric film is provided on the first electrode surface and has a first piezoelectric film surface (511) formed on the side opposite to the first electrode surface side, the insulating portion is provided on the first piezoelectric film surface, and overlaps with the entire opening in the stacking direction in a predetermined cross section taken through the opening in the stacking direction, The piezoelectric element according to claim 1 , wherein the second piezoelectric film is provided on the first piezoelectric film surface across the insulating portion.

4. 4. The piezoelectric element of claim 3, wherein the first piezoelectric film and the second piezoelectric film contain scandium, and the amount of scandium per unit mass of the first piezoelectric film is smaller than the amount of scandium per unit mass of the second piezoelectric film.

5. The piezoelectric film includes a first piezoelectric film (51), a second piezoelectric film (53), and a third piezoelectric film (52) that are formed side by side in the stacking direction, The first piezoelectric film is provided on the first electrode surface and has a first piezoelectric film surface (511) formed on the side opposite to the first electrode surface side, the insulating portion is provided on the first piezoelectric film surface, and overlaps with the entire opening in the stacking direction in a predetermined cross section taken through the opening in the stacking direction, The second piezoelectric film is provided on the first piezoelectric film surface across the insulating portion, and has a second piezoelectric film surface (513) formed on the opposite side to the first piezoelectric film surface, The piezoelectric element according to claim 1 , wherein the third piezoelectric film is provided on the second piezoelectric film surface.

6. 6. The piezoelectric element of claim 5, wherein the first piezoelectric film, the second piezoelectric film and the third piezoelectric film are composed of scandium, and the amount of scandium per unit mass of the first piezoelectric film is smaller than the amount of scandium per unit mass of at least one of the second piezoelectric film and the third piezoelectric film.

7. The first piezoelectric film has a piezoelectric film recess (513) that forms a piezoelectric film space (512) formed by recessing the first piezoelectric film surface toward the first electrode surface, A piezoelectric element as described in any one of claims 3 to 6, wherein the insulating portion is provided in the piezoelectric film space, and an insulating surface (80d) formed on the opposite side to the piezoelectric film recess side forms a plane that is continuous with a surface on the first piezoelectric film surface that is different from the piezoelectric film recess.

8. the insulating portion has, on one side in a cross-sectional width direction perpendicular to the stacking direction in the predetermined cross section, a first extension portion (80a) that does not overlap with the opening in the stacking direction, and a second extension portion (80b) that does not overlap with the opening in the stacking direction on the other side in the cross-sectional width direction, A piezoelectric element as described in any one of claims 3 to 7, wherein the size of the first extension portion and the second extension portion in the cross-sectional width direction is four or more times the dimension in the stacking direction of the piezoelectric film on which the insulating portion is provided.

9. the second piezoelectric film has a crystalline structure; 9. The piezoelectric element according to claim 3, wherein the insulating portion includes a material that allows the crystal structure of the second piezoelectric film to be self-oriented.

10. 10. The piezoelectric element according to claim 1, wherein the insulating portion is made of a different material from the support body, and is formed at a position corresponding to a portion where the opening is to be formed.

11. 11. The piezoelectric element according to claim 1, wherein the insulating portion includes an amorphous film having an amorphous structure.

12. The piezoelectric element according to claim 1 , wherein the insulating portion includes a gap.

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