Piezoelectric film device, transducer, and method for manufacturing piezoelectric film device

Abstract

To provide a piezoelectric film device capable of increasing intended vibration while suppressing unintended vibration, a transducer and a method for manufacturing a piezoelectric film device.SOLUTION: A sonic wave generating device includes a piezoelectric film device which includes: a substrate 80 that has a lower surface 81 and an upper surface 82 facing in opposite directions to each other; a supporting part 41 that supports the lower surface 81 and that is fixed to an installation surface; and a piezoelectric film that is provided on the upper surface 82 and that is displaced in a vertical direction together with the substrate 80 in response to the application of a bias voltage. The substrate 80 has, as areas of the lower surface 81, a first area 81x that is supported by the supporting part 41 and a second area 81y that is not supported by the supporting part 41. The substrate has a cantilever structure where the substrate is supported in only the first area 81x by the supporting part 41. A part of the root 89 of the cantilever structure is made of a silicon oxide film 35 that is a low Young's modulus material part 88 with a Young's modulus lower than that of silicon that is a material forming other portions in the substrate 80.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to a piezoelectric membrane device, a transducer, and a method for manufacturing a piezoelectric membrane device. [Background technology]

[0002] Patent document 1 describes a transducer that includes a support having a cavity, a vibrating membrane that is disposed opposite the cavity and is capable of vibrating in the opposing direction, and a piezoelectric element formed on the surface of the vibrating membrane opposite the cavity, forming a cantilever having a fixed end and a free end. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-52305

[0004] [overview] Here, in the above-mentioned transducer, a method for increasing the sound pressure (i.e., increasing the vibration) is to make the transducer thinner to make it easier to bend. However, when the thickness is reduced, the vibration increases, but vibrations other than the primary resonance may also increase, and there is a risk of unintended vibrations occurring.

[0005] The present disclosure provides a piezoelectric film device, a transducer, and a method for manufacturing a piezoelectric film device that can increase intended vibration while suppressing unintended vibration.

[0006] A piezoelectric film device according to one aspect of the present disclosure comprises a substrate having a first surface and a second surface facing in opposite directions, a support portion supporting the first surface and fixed to an installation surface, and a piezoelectric film provided on the second surface and displacing in the first direction together with the substrate in response to application of a bias voltage, wherein a portion of the portion of the substrate supported by the support portion is made of a low Young's modulus material having a lower Young's modulus than the material constituting the remaining portion of the substrate. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a plan view of a sound wave generating device according to the present embodiment. [Diagram 2] FIG. 2 is a bottom view of the sound wave generating device according to the present embodiment. [Diagram 3] FIG. 3 is a vertical cross-sectional view of the sound wave generating device taken along line III-III in FIG. [Figure 4] FIG. 4 is a vertical cross-sectional view showing the support portion and the substrate according to the present embodiment. [Diagram 5] 5(a) and (b) are diagrams illustrating the first creation method. [Figure 6] 6(a) and (b) are vertical cross-sectional views showing the steps of the first manufacturing method. [Figure 7] 7(a) to (c) are vertical cross-sectional views showing the steps of the second manufacturing method. [Figure 8] FIG. 8 is a longitudinal cross-sectional view showing steps in a manufacturing procedure for an acoustic wave generating device. [Figure 9] FIG. 9 is a vertical cross-sectional view showing a step carried out following the step shown in FIG. [Figure 10] FIG. 10 is a vertical cross-sectional view showing a step carried out following the step shown in FIG. [Figure 11] FIG. 11 is a vertical cross-sectional view showing a step carried out following the step shown in FIG. [Figure 12] FIG. 12 is a plan view showing a step carried out following the step shown in FIG. [Figure 13] FIG. 13 is a plan view showing a step carried out following the step shown in FIG. [Figure 14] FIG. 14 is a vertical cross-sectional view showing a step carried out following the step shown in FIG. [Figure 15] FIG. 15 is a vertical cross-sectional view showing a step carried out following the step shown in FIG. [Figure 16]FIG. 16 is a diagram illustrating the function and effect of the sound wave generating device according to this embodiment. [Figure 17] FIG. 17 is a plan view of a sound wave generating device according to a modified example. [Figure 18] 18 is a longitudinal sectional view of the sound wave generating device taken along line XVIII-XVIII in FIG. 17. FIG. [Figure 19] FIG. 19 is a plan view of a sound wave generating device according to a modified example. [Figure 20] FIG. 20 is a top perspective view of the sound wave generating device shown in FIG. [Figure 21] FIG. 21 is a perspective view from below of the sound wave generating device shown in FIG. [Figure 22] FIG. 22 is a perspective view of a sound wave generating device according to a modified example, as viewed from above. [Diagram 23] FIG. 23 is a perspective view from below of the sound wave generating device shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] [Detailed Description] Hereinafter, an embodiment will be described with reference to the drawings. In the description, the same elements or elements having the same functions are denoted by the same reference numerals, and duplicated description will be omitted.

[0009] Fig. 1 is a plan view of a sound wave generating device (transducer) according to this embodiment. Fig. 2 is a bottom view of the sound wave generating device according to this embodiment. Fig. 3 is a vertical cross-sectional view of the sound wave generating device taken along line III-III in Fig. 1. Note that Fig. 3 shows a simplified configuration of a substrate 80, which will be described later, and omits the illustration of a low Young's modulus material portion 88 (details will be described later).

[0010] The sound wave generating device 1 is, for example, a device including one piezoelectric film device 90. The sound wave generating device 1 is a device that generates sound waves by vibrating the air through the vibration of the piezoelectric film of the piezoelectric film device 90. The sound wave generating device 1 may be, for example, a speaker, or an ultrasonic transducer that generates ultrasonic waves. In this case, the speaker and the ultrasonic transducer both vibrate the air and can operate with roughly the same structure, but the frequency ranges used are different between the audible range and the ultrasonic range. The piezoelectric film device 90 is, for example, a MEMS (Micro Electro Mechanical Systems) device that utilizes piezoelectric characteristics. In the following, the sound wave generating device 1 will be described as a speaker.

[0011] 1 to 3, the sound wave generating device 1 includes a substrate assembly 2 and a subframe 3. The substrate assembly 2 includes a support substrate 4, a vibration film forming layer 6, and a piezoelectric element .

[0012] The support substrate 4 has a quadrangular shape (approximately rectangular) in plan view. In the following description, the longitudinal direction of the approximately rectangular support substrate 4 in plan view is defined as the X direction, the lateral direction is defined as the Y direction, and the direction intersecting the X direction and the Y direction (i.e., the thickness direction of the support substrate 4) is defined as the Z direction. Within the Z direction, the direction in which the piezoelectric element 10 is located relative to the support substrate 4 will be described as "up" and the direction in which the support substrate 4 is located relative to the piezoelectric element 10 will be described as "down".

[0013] The support substrate 4 is made of, for example, a part of an SOI substrate. Specifically, the SOI substrate includes a silicon (Si) substrate 32 as a support layer, an oxide film layer 33 as a BOX layer formed on the surface of the silicon substrate 32, and a silicon (Si) layer 34 as an active layer formed on the surface of the silicon substrate 32. In the configuration according to this embodiment, a silicon oxide (SiO2) film 35 is formed on the surface of the silicon layer 34. Among them, the support substrate 4 includes the silicon substrate 32 and the oxide film layer 33 formed on the surface of the silicon substrate 32. The thickness of the support substrate 4 is about 380 μm.

[0014] The support substrate 4 has a cavity 5 formed by a through hole penetrating in the Z direction. The cavity 5 has a rectangular parallelepiped shape in plan view with a rectangular opening 53 on the lower surface (bottom surface) side of the cavity 5 as the bottom surface.

[0015] The support substrate 4 includes a support portion 41, a first portion 42, a second portion 43, and a third portion 44. The support portion 41 supports a lower surface 81 of the substrate 80 and is fixed to an installation surface as described later. The support portion 41 and the second portion 43 extend along the Y direction so as to sandwich the cavity 5 between them in the X direction. The first portion 42 and the third portion 44 extend along the X direction so as to sandwich the cavity 5 between them in the Y direction. That is, the support portion 41, the first portion 42, the second portion 43, and the third portion 44 are provided so as to surround the cavity 5. In the following description, the direction in the X direction in which the second portion 43 is located with respect to the support portion 41 as a reference is referred to as the "front", and the direction in which the support portion 41 is located with respect to the second portion 43 as a reference is referred to as the "rear".

[0016] The vibration membrane forming layer 6 is formed on the support substrate 4. The vibration membrane forming layer 6 is made of a laminated film in which a silicon layer 34 and a silicon oxide film 35 are laminated in this order from the support substrate 4 side. The silicon layer 34 has a thickness of, for example, about 20 μm, and the silicon oxide film 35 has a thickness of, for example, about 0.5 μm.

[0017] The vibration membrane forming layer 6 includes a vibration membrane 7 facing the cavity 5 in a plan view, and a frame portion 8 formed to surround the cavity 5. The vibration membrane 7 has a rectangular shape that is almost similar to the cavity 5 in a plan view. The frame portion 8 includes a support frame body 181 (see FIG. 3), a first portion 182 (see FIG. 1), a second portion 183 (see FIG. 3), and a third portion 184 (see FIG. 1). The support frame body 181 constitutes a part of a substrate 80 described later, and is supported by a support portion 41. The first portion 182 is formed along the X direction on the first portion 42 of the support substrate 4 and is supported by the first portion 42. The second portion 183 is formed along the Y direction on the second portion 43 of the support substrate 4 and is supported by the second portion 43. The third portion 184 is formed along the X direction on the third portion 44 of the support substrate 4 and is supported by the third portion 44.

[0018] In the manufacturing process, the slits 9 are formed before the cavities 5 are formed in the support substrate 4 (details will be described later). In the step of forming the slits 9, the slits 9 are formed so as to penetrate the vibration membrane 7 from the surface of the interlayer insulating film 15 (described later) formed on the vibration membrane forming layer 6 and reach the support substrate 4.

[0019] 1, the slit 9 is composed of a first portion 9a and a third portion 9c formed along the X direction, and a second portion 9b formed along the Y direction. The first portion 9a is formed along a side extending in the X direction at one end side of the cavity 5 in the Y direction. The third portion 9c is formed along a side extending in the X direction at the other end side of the cavity 5 in the Y direction. The second portion 9b is formed so as to connect a front end portion of the first portion 9a and a front end portion of the third portion 9c.

[0020] The piezoelectric element 10 is formed after forming a hydrogen barrier film 14 on the vibration film forming layer 6. In detail, the piezoelectric element 10 is formed so that at least a part of it is disposed on the vibration film 7. In this embodiment, the entire piezoelectric element 10 is disposed on the vibration film 7. The piezoelectric element 10 includes a lower electrode 11 formed on the vibration film 7, a piezoelectric film 12 formed on the lower electrode 11, and an upper electrode 13 formed on the piezoelectric film 12. In addition, a hydrogen barrier film 140 is formed on the upper electrode 13 of the piezoelectric element 10.

[0021] The lower electrode 11 and the upper electrode 13 are made of a conductive metal thin film such as platinum, molybdenum, iridium, titanium, etc. The lower electrode 11 has a thickness of, for example, about 200 nm, and the upper electrode 13 has a thickness of, for example, about 80 nm.

[0022] The piezoelectric film 12 is made of, for example, lead zirconate titanate (PZT). The piezoelectric film 12 may be made of niobium-doped lead zirconate titanate (PNZT) film, lanthanum-doped lead zirconate titanate (PLZT) film, strontium barium titanate (BST) film, strontium bismuth tantalate (SBT) film, strontium barium niobate (SBN) film, lithium niobate (LiNbO3) film, barium titanate (TiBaO3) film, lanthanum strontium copper oxide (LSCO) film, potassium dihydrogen phosphate (KDP) film, potassium tantalum niobate (KTN) film, magnesium lead niobate titanate (PMN-PT) ceramic film, zinc lead niobate titanate (PZN-PT) ceramic film, aluminum nitride (AIN), zinc oxide (ZnO), lead titanate (PbTiO3), etc. The thickness of the piezoelectric film 12 is, for example, about 2 μm.

[0023] A hydrogen barrier film 14 is formed on the vibration film 7 and frame portion 8 that constitute the vibration film forming layer 6. The hydrogen barrier film 14 is formed on the vibration film 7 so as to cover the piezoelectric element 10. The hydrogen barrier film 14 is made of, for example, Al2O3 (alumina). The hydrogen barrier film 14 has a thickness of about 20 nm to 100 nm. The hydrogen barrier film 14 is provided to prevent deterioration of the characteristics of the piezoelectric film 12 due to hydrogen reduction.

[0024] An interlayer insulating film 15 is laminated on the hydrogen barrier film 14. The interlayer insulating film 15 is made of, for example, a film (TEOS film) containing tetraethoxysilane (TEOS). The interlayer insulating film 15 may be made of silicon nitride (SiN) or the like. The thickness of the interlayer insulating film 15 is, for example, about 0.2 μm to 1.5 μm.

[0025] An upper wiring 18 and a lower wiring 19 (see FIG. 1) are formed on the interlayer insulating film 15. The upper wiring 18 and the lower wiring 19 are provided at the X-direction end (rear end) of the interlayer insulating film 15 on the side where the support portion 41 is provided. The upper wiring 18 and the lower wiring 19 extend in the X-direction with a gap between them in the Y-direction. The upper wiring 18 and the lower wiring 19 may be made of a metal material containing Al (aluminum). The thickness of the upper wiring 18 and the lower wiring 19 is, for example, about 1 μm.

[0026] The front end of the upper wiring 18 is disposed above the rear end of the upper electrode 13. A contact hole 16 (see FIGS. 1 and 3) is formed between the upper wiring 18 and the upper electrode 13, continuously penetrating the hydrogen barrier film 14 and the interlayer insulating film 15. The front end of the upper wiring 18 enters the contact hole 16 and is connected to the rear end of the upper electrode 13 within the contact hole 16. A wide upper pad portion 18a is formed at the rear end of the upper wiring 18. The upper pad portion 18a is disposed on a support frame 181 of the frame portion 8.

[0027] The front end of the lower wiring 19 is disposed above the rear end of the lower electrode 11. A contact hole 17 (see FIG. 1) is formed between the lower wiring 19 and the lower electrode 11, continuously penetrating the hydrogen barrier film 14 and the interlayer insulating film 15. The front end of the lower wiring 19 enters the contact hole 17 and is connected to the rear end of the lower electrode 11 within the contact hole 17. A wide lower pad portion 19a is formed at the rear end of the lower wiring 19. The lower pad portion 19a is disposed on a support frame 181 of the frame portion 8.

[0028] A passivation film 20 is formed on the interlayer insulating film 15 so as to cover the upper wiring 18 and the lower wiring 19. The passivation film 20 is made of, for example, a film (TEOS film) containing tetraethoxysilane (TEOS). The passivation film 20 may be made of silicon nitride (SiN) or the like. The thickness of the passivation film 20 is, for example, about 0.1 μm to 1.0 μm. The passivation film 20 has an upper pad opening 21 exposing a part of the upper pad portion 18a and a lower pad opening 22 (see FIG. 1) exposing a part of the lower pad portion 19a. Hereinafter, the hydrogen barrier film 14, the interlayer insulating film 15, and the passivation film 20 may be collectively referred to as an insulating film 30.

[0029] In the substrate assembly 2, the vibration membrane 7 and the support frame 181 of the frame portion 8 form a substrate 80 having a rectangular shape in a plan view. The substrate 80 has a lower surface 81 (first surface) and an upper surface 82 (second surface) facing in opposite directions. The lower surface 81 is the lower surface of the silicon layer 34, and the upper surface 82 is the upper surface of the silicon oxide film 35. The substrate 80 has, as regions of the lower surface 81, a first region 81x supported by the support portion 41 and a second region 81y not supported by the support portion 41.

[0030] The first region 81x is supported by the upper surface of the oxide film layer 33 of the support portion 41 and fixed to the upper surface. Being supported by (the upper surface of the oxide film layer 33 of) the support portion 41 means, for example, being in contact with the support portion 41 directly or via some member and being supported by the support portion 41. Being fixed to the support portion 41 means, for example, being fixed to the support portion 41 directly or via some member and not being separated from the support portion 41. Being fixed to the support portion 41 may be, for example, integrated with the support portion 41 or may be bonded to the support portion 41. Note that in the substrate 80, the entire region supported by the support portion 41 does not necessarily have to be fixed to the support portion 41, and only a part of the supported region may be fixed to the support portion 41.

[0031] The piezoelectric film 12 is provided on an upper surface 82 of the substrate 80 (i.e., an upper surface of the silicon oxide film 35) via a lower electrode 11, and displaces in the vertical direction (first direction) together with the substrate 80 in response to application of a bias voltage and a drive voltage, which will be described later. Such a substrate 80, a support portion 41, and a piezoelectric element 10 may be collectively referred to as a piezoelectric film device 90.

[0032] The piezoelectric film device 90 has a cantilever structure in which the rear end of the substrate 80 supported by the support portion 41 is a fixed end and the front end of the substrate 80 is a free end. In the piezoelectric film device 90, the piezoelectric film 12 is displaced in the vertical direction in response to application of a bias voltage and a drive voltage, and the free end side (front end side) of the substrate 80 is displaced in the vertical direction together with the piezoelectric film 12.

[0033] As shown in FIG. 1 and FIG. 3, the subframe 3 is composed of, for example, a silicon substrate with a silicon oxide film (not shown) formed on the lower surface and the upper surface. The subframe 3 is disposed on the substrate assembly 2 so as to cover the piezoelectric film device 90. The subframe 3 is bonded to the frame portion 8 via an adhesive (not shown). The subframe 3 is composed of a first portion 131, a second portion 132, a third portion 133, and a connecting portion 134, all of which are erected in the Z direction. As shown in FIG. 1, the first portion 131 is formed along the X direction above the first portion 182 of the frame portion 8. The second portion 132 is formed along the Y direction above the second portion 183 of the frame portion 8. The third portion 133 is formed along the X direction above the third portion 184 of the frame portion 8. The connecting portion 134 is formed along the Y direction above the support frame body 181. The area surrounded by the first portion 131, the second portion 132, the third portion 133, and the connecting portion 134 is the area directly above the cavity 5, and is an accommodating recess 3a for accommodating the piezoelectric film device 90. A through hole 3b that functions as an outlet for the sound generated by the sound wave generating device 1 is formed above the accommodating recess 3a.

[0034] The provision of the above-mentioned subframe 3 prevents air leakage and improves the sound characteristics of the sound wave generating device 1. The provision of the subframe 3 also protects the cantilever-structured piezoelectric film device 90. Furthermore, the provision of the subframe 3 improves the rigidity of the chip.

[0035] In such a sound wave generating device 1, when a voltage is applied between the lower electrode 11 and the upper electrode 13, the piezoelectric film 12 is deformed by the inverse piezoelectric effect. As a result, the piezoelectric film 12 and the substrate 80 constituting the piezoelectric film device 90 are deformed with the first region 81x, which is the fixed end, as a fulcrum. When a voltage corresponding to an audio signal is continuously applied between the lower electrode 11 and the upper electrode 13, the piezoelectric film device 90 vibrates so that the free end side of the substrate 80 moves back and forth in the up and down direction. This vibration of the piezoelectric film device 90 vibrates the air around the piezoelectric film device 90, generating sound waves. The sound waves propagate to the external space through the through hole 3b of the subframe 3. Note that sound waves are also generated in the opposite direction.

[0036] Next, a detailed configuration of the substrate 80 will be described with reference to Fig. 4. Fig. 4 is a vertical cross-sectional view showing the support portion 41 and the substrate 80 according to this embodiment. As described above, Fig. 3 shows a simplified configuration of the substrate 80 and omits illustration of the low Young's modulus material portion 88, but Fig. 4 shows the details of the substrate 80 and illustrates the low Young's modulus material portion 88.

[0037] As shown in FIG. 4, a part of a base portion 89 of the cantilever structure in the substrate 80 is provided with a low Young's modulus material portion 88 made of a low Young's modulus material having a lower Young's modulus than silicon, which is a material constituting the remaining portion of the substrate 80. The base portion of the cantilever structure is, for example, a portion including a boundary portion between the first region 81x and the second region 81y in the X direction. The base portion of the cantilever structure may be, for example, a portion near the boundary portion between the first region 81x and the second region 81y in the X direction. That is, the base portion 89 of the cantilever structure may be only a portion on the first region 81x adjacent to the second region 81y, or only a portion on the second region 81y adjacent to the first region 81x. Such a base portion 89 is a portion to which the most stress is applied when the substrate 80 is displaced in the up-down direction, and is a portion that is affected by bending due to the displacement.

[0038] The low Young's modulus material is, for example, an oxide film (silicon oxide film). The Young's modulus of the silicon oxide film is 72 Gpa, which is lower than the Young's modulus of silicon constituting the other parts, which is 193 Gpa. In this way, the Young's modulus of the low Young's modulus material may be 1 / 2 or less of the Young's modulus of silicon, which is the material of the other parts.

[0039] In the configuration according to the present embodiment, the region of the root portion 89 on the upper surface 82 side is the low Young's modulus material portion 88, and the region on the lower surface 81 side is not the low Young's modulus material portion 88 but is the region of the silicon layer 34. As described above, the film thickness of the silicon layer 34 is, for example, about 20 μm. The low Young's modulus material portion 88 may be provided in a region of the silicon layer 34, about 12 μm thick on the upper surface 82 side (i.e., a region of about 3 / 5 in the thickness direction of the silicon layer 34). The length of the low Young's modulus material portion 88 in the X direction may be, for example, about 1000 μm. The entire film thickness of the silicon layer 34 may be made of the low Young's modulus material.

[0040] Next, two methods (a first and a second creation method) for creating the low Young's modulus material portion 88 will be described. FIGS. 5(a) and (b) are diagrams for explaining the first creation method. FIGS. 6(a) and (b) are vertical cross-sectional views showing the steps of the first creation method. The first creation method is a method in which a thermal oxidation process is performed on an SOI substrate to form a silicon oxide film 35 on the surface of a silicon layer 34 and simultaneously create the low Young's modulus material portion 88.

[0041] As shown in Fig. 5(a) and (b), the first preparation method is a method for preparing the intended low Young's modulus material portion 88 by utilizing the characteristic that when a silicon oxide film 35 is formed on the surface of a silicon layer 34 by thermal oxidation, about 44% of the thickness of the silicon oxide film is formed on the silicon layer side (see Fig. 5(b)). That is, as shown in Fig. 6(a), the groove interval W1 and groove width W2 of the multiple grooves 84 (recesses) to be formed are derived in advance based on the thickness d of the silicon oxide film 35 to be obtained, and the multiple grooves 84 are formed in the silicon layer 34. As a result, a processed member 101A is prepared (first step) including a portion made of silicon (first material) and having multiple grooves 84 formed in a part of the portion made of silicon. The depth of the grooves 84 is determined according to the thickness of the low Young's modulus material portion 88 to be obtained. Then, by performing a thermal oxidation process on the surface of the silicon layer 34 in which the multiple grooves 84 are formed, a silicon oxide film 35 is formed in the processed member 101A, and the grooves 84 are filled with the silicon oxide film to form a low Young's modulus material portion 88 (second process).

[0042] Now, assuming that the thickness of the silicon oxide film 35 to be obtained is d, the groove interval is W1, and the groove width is W2, it is considered that the values ​​of W1 and W2 are determined so that the following formulas (1) and (2) hold based on the film thickness relationship shown in Fig. 5(b) (approximately 44% of the silicon oxide film is formed on the silicon layer 34 side, and approximately 56% is formed on the surface of the silicon layer 34). The depth of the groove 84 is determined according to the thickness of the low Young's modulus material portion 88 to be obtained. d×44%>W1×1 / 2···(1) d×56%>W2×1 / 2···(2) Based on the above formulas (1) and (2) and information on the desired thickness of the low Young's modulus material portion 88, the conditions for the multiple grooves 84 to be formed in the silicon layer 34 are determined, and the silicon layer 34 having the multiple grooves 84 formed therein according to the determined conditions is subjected to a thermal oxidation treatment. As a result, the low Young's modulus material portion 88 having the intended thickness is formed as shown in FIG. 6(b).

[0043] 7(a) to 7(c) are vertical cross-sectional views showing the steps of the second manufacturing method. In the second manufacturing method, a recess corresponding to the shape of the desired low Young's modulus material portion 88 is formed on the surface of the silicon layer 34, and a silicon oxide film is formed on the recess and the surface of the silicon layer 34, thereby creating the low Young's modulus material portion 88.

[0044] As shown in FIG. 7(a), in the second preparation method, first, a recess 85 is formed on the surface of the silicon layer 34 according to the shape (thickness and length in the X and Y directions) of the low Young's modulus material portion 88 to be obtained. This prepares a processed member 101B including a portion made of silicon (first material) and having the recess 85 formed in a part of the portion made of silicon (first step). Next, as shown in FIG. 7(b), a silicon oxide film is formed on the recess 85 and the surface of the silicon layer 34. That is, the silicon oxide film is filled in the recess 85 (second step). A nitride film or the like may be formed instead of the silicon oxide film. In this case, the low Young's modulus material portion 88 is composed of a nitride film. Finally, as shown in FIG. 7(c), the excess low Young's modulus material is ground (polished) by CMP (Chemical Mechanical Polishing) or the like.

[0045] Next, an example of a manufacturing procedure for the sound wave generating device 1 according to this embodiment will be described with reference to Fig. 8 to Fig. 15. Fig. 8 to Fig. 15 are vertical cross-sectional views (or plan views) showing a manufacturing procedure for the sound wave generating device 1 according to this embodiment shown in Fig. 1. Here, a manufacturing procedure for forming the low Young's modulus material part 88 by the above-mentioned first manufacturing method will be described.

[0046] First, as shown in FIG. 8, a thermal oxidation process is performed on an SOI substrate. The SOI substrate includes a silicon substrate 32, an oxide film layer 33 formed on the surface thereof, and a silicon layer 34 formed on the surface thereof. Here, an SOI substrate (a member to be processed 101A) having a plurality of grooves 84 (see FIG. 6(a)) formed in a part of the silicon layer 34 is prepared (first step). Then, the member to be processed 101A is thermally oxidized to form a silicon oxide film 35 on the surface of the silicon layer 34 opposite to the oxide film layer 33, and a silicon oxide film 31 on the surface of the silicon substrate 32 opposite to the oxide film layer 33. At the same time as the silicon oxide film 35 is formed, the silicon oxide film is filled in the plurality of grooves 84 (see FIG. 6(a)), and a low Young's modulus material portion 88 is formed (second step). This prepares a processed member 101 after thermal oxidation treatment, having one end face 101a (upper surface of silicon oxide film 35) and the other end face 101b (lower surface of silicon oxide film 31) facing in opposite directions. The silicon substrate 32 and the oxide film layer 33 are parts that constitute the support substrate 4, and the silicon layer 34, the silicon oxide film 35, and the low Young's modulus material part 88 are parts that constitute the vibration membrane forming layer 6.

[0047] 9, a hydrogen barrier film 14 is formed on one end surface 101a (upper surface of the silicon oxide film 35) of the workpiece 101, and then a lower electrode film 111 which is a material film of the lower electrode 11, a piezoelectric material film 112 which is a material film of the piezoelectric film 12, and an upper electrode film 113 which is a material film of the upper electrode 13 are formed in that order (third step). Then, the upper electrode film 113, the piezoelectric material film 112, and the lower electrode film 111 are patterned, for example, in that order by photolithography and etching to form the upper electrode 13, the piezoelectric film 12, and the lower electrode 11. As a result, the piezoelectric film 12 and electrodes (the lower electrode 11 and the upper electrode 13) are formed on the one end surface 101a of the workpiece 101, and the piezoelectric element 10 is formed (film forming step).

[0048] 10, a hydrogen barrier film 140 is formed to cover the exposed surface of the piezoelectric element 10. The hydrogen barrier film 140 is made of, for example, an alumina film. An interlayer insulating film 15 is then formed on the entire surface of the hydrogen barrier film 140. Furthermore, the hydrogen barrier film 140 and the interlayer insulating film 15 are continuously etched to form contact holes 16 and 17 (see FIG. 1). At this time, the interlayer insulating film 15 and the hydrogen barrier film 14 in the slit portion are also etched.

[0049] Then, a wiring film, which is a material film of the upper wiring 18 and the lower wiring 19 (see FIG. 1), is formed on the interlayer insulating film 15 including the inside of the contact holes 16 and 17, and the wiring film is patterned by photolithography and etching to form the upper wiring 18 and the lower wiring 19. Then, a passivation film 20 is formed on the interlayer insulating film 15 so as to cover the upper wiring 18 and the lower wiring 19. The interlayer insulating film 15 and the passivation film 20 are made of, for example, a TEOS film containing tetraethoxysilane (TEOS). The interlayer insulating film 15 and the passivation film 20 may be made of, for example, silicon nitride (SiN) or the like.

[0050] 11, an upper pad opening 21 exposing a part of the upper pad portion 18a is formed in the passivation film 20 by photolithography and etching, and a lower pad opening 22 (see FIG. 1) exposing a part of the lower pad portion 19a is formed. An opening 23 is formed in the interlayer insulating film 15 and the passivation film 20 by photolithography and etching. The opening 23 may not be formed or may be partially opened. Then, a slit 9 is formed by photolithography and etching, which penetrates the vibration film forming layer 6 (silicon oxide film 35 and silicon layer 34) and the oxide film layer 33 continuously and reaches the silicon substrate 32. By forming the slit 9, a frame portion 8 which is a peripheral portion of the vibration film forming layer 6 and a vibration film 7 which is a central portion of the vibration film forming layer 6 are obtained, and a substrate assembly work-in-progress 2A before the cavity 5 is formed is obtained.

[0051] 12, an adhesive (not shown) is applied to the surface of the subframe 3 facing the board assembly work-in-progress 2A, and the subframe 3 is fixed to the board assembly work-in-progress 2A.

[0052] Next, as shown in FIG. 13, a support substrate 400 is temporarily attached to the upper surface of the subframe 3, and the silicon oxide film 31 and silicon substrate 32, which are the other end surface of the substrate assembly work-in-progress 2A (the component to be processed after film formation), are polished to thin the silicon substrate 32.

[0053] 14, a resist mask (not shown) is formed on the lower surface of the silicon substrate 32 in a region where the cavity 5 is to be formed (specifically, a region where the opening 53 is to be formed), and the silicon substrate 32 is etched from the lower surface. This forms the cavity 5, and the sound wave generating device 1 is formed (fourth step) including a piezoelectric film device 90 having a substrate 80, a support portion 41, and a piezoelectric film 12. In the fourth step, polishing and the like are performed so that the low Young's modulus material portion 88 becomes a base portion 89 of the cantilever structure. Finally, as shown in FIG. 15, the support substrate 400 is peeled off, so that the piezoelectric film device 90 becomes operable, and the manufacture of the sound wave generating device 1 is completed.

[0054] Next, the effects of the piezoelectric film device 90, the sound wave generating device 1, and the manufacturing method of the piezoelectric film device 90 according to this embodiment will be described.

[0055] The piezoelectric film device 90 of this embodiment comprises a substrate 80 having a lower surface 81 and an upper surface 82 facing in opposite directions, a support portion 41 supporting the lower surface 81 and fixed to an installation surface, and a piezoelectric film 12 provided on the upper surface 82 and displacing vertically together with the substrate 80 in response to the application of a bias voltage. The substrate 80 has, as regions of the lower surface 81, a first region 81x supported by the support portion 41 and a second region 81y not supported by the support portion 41, and has a cantilever structure supported by the support portion 41 only in the first region 81x, and a portion of a base portion 89 of the cantilever structure is made of a silicon oxide film, which is a low Young's modulus material having a lower Young's modulus than silicon, the material constituting the remaining portions of the substrate 80.

[0056] In a piezoelectric film device that is a sound wave generating device with a cantilever structure, one possible method for increasing the sound pressure (i.e., increasing the vibration) is to make the substrate of the cantilever thinner to make it easier to bend. However, when the substrate is made thinner, not only does the vibration increase, but vibrations other than the primary resonance may also increase, and there is a risk of unintended vibrations occurring. It is also possible to simply use a material with a low Young's modulus for the substrate of the cantilever (for example, a material with a Young's modulus lower than that of silicon), but in this case there is a risk that it will not be able to withstand the semiconductor process during manufacturing.

[0057] In this regard, in the piezoelectric film device 90 according to the present embodiment, only a part of the root portion 89 of the cantilever structure is replaced from silicon to a silicon oxide film, which is a low Young's modulus material. In this way, a part of the root portion 89, which is the part of the substrate 80 most susceptible to bending, is replaced with a silicon oxide film, which is easier to bend than silicon, and the vibration of the cantilever can be increased. In addition, since only a part of the root portion 89 is replaced with a silicon oxide film and the thickness of the substrate itself is not thinned, it is possible to appropriately suppress the increase in vibration other than the first resonance. As described above, according to the piezoelectric film device 90 according to the present embodiment, it is possible to suppress unintended vibration in the cantilever and increase the intended vibration. In addition, in the piezoelectric film device 90 according to the present embodiment, only a part of the substrate 80 is replaced with a silicon oxide film, so there is no problem with adapting to a semiconductor process, which is a problem when the entire substrate is made of a low Young's modulus material.

[0058] FIG. 16 is a diagram for explaining the action and effect of the piezoelectric film device 90 included in the sound wave generating device 1 according to this embodiment. In FIG. 16, the horizontal axis indicates frequency, the left vertical axis indicates sound pressure (vibration), and the right vertical axis indicates the amount of displacement. In FIG. 16, the thick solid line indicates the sound pressure in the piezoelectric film device 90 according to this embodiment, the thin solid line indicates the sound pressure in the piezoelectric film device according to the comparative example, the thick dashed line indicates the amount of displacement in the piezoelectric film device 90 according to this embodiment, and the thin dashed line indicates the amount of displacement in the piezoelectric film device according to the comparative example. The piezoelectric film device according to the comparative example here is the same as the piezoelectric film device 90 in terms of conditions such as the thickness (20 μm) of the silicon layer, which is the active layer constituting the substrate, and is different from the piezoelectric film device 90 only in that a part of the substrate is not replaced with a silicon oxide film. FIG. 16 shows a simulation result when the piezoelectric film device 90 according to this embodiment and the piezoelectric film device according to the comparative example are vibrated.

[0059] As shown in Fig. 16, in the piezoelectric film device 90 according to this embodiment, although a part of the substrate 80 is made of a low Young's modulus material, the sound pressure (vibration) other than the first resonance can be made to be the same as that of the piezoelectric film device according to the comparative example in which the silicon oxide film, which is a low Young's modulus material, is not used. In other words, unintended vibration can be suppressed. In addition, in the piezoelectric film device 90, since a part of the base portion 89 is replaced with a silicon oxide film, the sound pressure (vibration) and the amount of displacement in the first resonance (low frequency range) can be improved.

[0060] In the piezoelectric film device 90, the region on the upper surface 82 side of the base portion 89 is made of a silicon oxide film, which is a low Young's modulus material, and the region on the lower surface 81 side of the base portion 89 is not made of a silicon oxide film, which is a low Young's modulus material. Considering the suitability for semiconductor processes, it is preferable to limit the region in which the low Young's modulus material is used, but by making only the upper surface 82 side a low Young's modulus material, it is possible to increase vibration while realizing suitability for semiconductor processes. In addition, by forming a silicon oxide film, which is a low Young's modulus material portion 88, on the upper surface 82 on the side where the silicon oxide film 35 is formed, it becomes easier to form them simultaneously, and the ease of manufacture can be improved.

[0061] As described above, the low Young's modulus material is an oxide film (for example, a silicon oxide film). This allows the low Young's modulus material portion 88 to be formed simultaneously with the formation of the silicon oxide film 35, thereby improving ease of manufacture.

[0062] The Young's modulus of the low Young's modulus material may be half or less than that of the other parts of the substrate, which allows the vibration of the cantilever to be appropriately increased.

[0063] 1, the sound wave generating device 1 according to this embodiment is configured to include one of the above-mentioned piezoelectric film devices 90. Since such a sound wave generating device 1 includes the above-mentioned piezoelectric film device 90, it is possible to suppress unintended vibrations while amplifying intended vibrations.

[0064] The manufacturing method of the piezoelectric film device according to the present embodiment includes a first step of preparing a workpiece including a portion made of a first material (silicon) and having a recess formed in a part of the portion made of the first material, a second step of filling the recess with a low Young's modulus material (silicon oxide film) having a Young's modulus lower than that of the first material, a third step of forming a piezoelectric film 12 and electrodes (upper electrode 13, lower electrode 11) on one end surface of the workpiece after the second step, and a fourth step of forming a substrate 80 and a support part 41 by processing the other end surface of the workpiece after the third step, and in the fourth step, the other end surface of the workpiece is processed so that the low Young's modulus material part 88 is located at the root part 89 of the cantilever structure. According to such a manufacturing method, the piezoelectric film device 90 having the above-mentioned effect can be appropriately manufactured.

[0065] In the second step, the first material may be thermally oxidized to form an oxide film, which is a low Young's modulus material, in the recess. This allows the SOI substrate to be thermally oxidized to form the silicon oxide film 35 on the surface of the silicon layer 34, and at the same time, the low Young's modulus material portion 88 can be created. In other words, the low Young's modulus material portion 88 can be easily created.

[0066] In the second step, after filling the recesses with the low Young's modulus material, excess low Young's modulus material may be ground away, thereby forming the silicon oxide film 35 and the low Young's modulus material portion 88 into the desired size and shape.

[0067] Although the embodiment according to the present disclosure has been described above, the present disclosure is not limited to the above embodiment. For example, in the above embodiment, the sound wave generating device 1 is described as including one piezoelectric film device 90, but the configuration of the sound wave generating device is not limited to this. The sound wave generating device 1 may include multiple (for example, a pair) piezoelectric film devices.

[0068] Fig. 17 is a plan view of a sound wave generating device 1A according to a modified example. Fig. 18 is a longitudinal sectional view of the sound wave generating device 1A taken along line XVIII-XVIII in Fig. 17. As shown in Figs. 17 and 18, the sound wave generating device 1A includes two (a pair) piezoelectric film devices 90, 90. The configuration of the piezoelectric film device 90 may be as described above. The pair of piezoelectric film devices 90, 90 are arranged, for example, such that the free ends face each other.

[0069] Furthermore, application examples of the piezoelectric film device are not limited to sound wave generating devices (speakers or ultrasonic transducers) and may be, for example, various other transducers, MEMS mirrors, inkjet heads, or the like.

[0070] In addition, in the above embodiment, the sound wave generating device 1 is described as including a substrate assembly 2 and a subframe 3, but this is not limited thereto, and the sound wave generating device may not include a subframe.

[0071] Fig. 19 is a plan view of a sound wave generating device 1B according to a modified example. Fig. 20 is a perspective view of the sound wave generating device 1B shown in Fig. 19 as viewed from above. Fig. 21 is a perspective view of the sound wave generating device 1B shown in Fig. 19 as viewed from below. The sound wave generating device 1B does not include a subframe, and includes only a substrate assembly 2B. The substrate assembly 2B includes a support substrate 4B, a vibration membrane forming layer 6B, and a piezoelectric element 10B.

[0072] The support substrate 4B has a quadrangular shape (approximately rectangular) in a plan view. The support substrate 4B is made of, for example, a part of an SOI substrate. The support substrate 4B may be configured to include a silicon substrate and an oxide film layer. The support substrate 4B has a cavity (hollow) 5B having a regular hexagonal shape in a plan view at its center. The cavity 5B is, for example, a hexagonal column shape. The support substrate 4B has a first portion 701, a second portion 702, a third portion 703, and a fourth portion 704 provided to surround the cavity 5B. The first portion 701 and the third portion 703 extend along the Y direction so as to sandwich the cavity 5B between them in the X direction. The second portion 702 and the fourth portion 704 extend along the X direction so as to sandwich the cavity 5B between them in the Y direction.

[0073] The vibration membrane forming layer 6B is formed on the support substrate 4B. The vibration membrane forming layer 6B may be composed of a laminated film in which a silicon layer and a silicon oxide film are laminated. The vibration membrane forming layer 6B includes a vibration membrane 7B facing the cavity 5B in a plan view, and a frame portion 8B formed to surround the cavity 5B. The vibration membrane 7B has a regular hexagonal shape that is almost similar to the cavity 5B in a plan view. The frame portion 8B includes a first frame body 801, a second frame body 802, a third frame body 803, and a fourth frame body 804. The first frame body 801 is supported by the first portion 701. The second frame body 802 is supported by the second portion 702. The third frame body 803 is supported by the third portion 703. The fourth frame body 804 is supported by the fourth portion 704.

[0074] The piezoelectric element 10B is formed so as to be disposed on the vibration film forming layer 6B, specifically, on the vibration film 7B. The piezoelectric element 10B may include a lower electrode formed on the vibration film 7B, a piezoelectric film formed on the lower electrode, and an upper electrode formed on the piezoelectric film.

[0075] Here, in the sound wave generating device 1B, slits 308, 309, and 310 are formed penetrating the piezoelectric element 10B and the vibration membrane 7B. The slit 308 extends along the Y direction. The slits 309 and 310 each extend so as to divide the area of ​​the piezoelectric element 10B into six equal parts, taking into account the extension direction of the slit 308. That is, the slits 308, 309, and 310 each extend so as to divide the area of ​​the piezoelectric element 10B into six equal parts. By forming such slits 308 and 309, the piezoelectric element 10B is separated into six piezoelectric elements 10Ba to 10Bf, and the vibration membrane 7B is separated into six vibration membranes 7Ba to 7Bf. As a result, the sound wave generating device 1B has six piezoelectric membrane devices 90Ba to 90Bf.

[0076] In each of such piezoelectric film devices 90Ba to 90Bf, a portion of the base of the cantilever structure is made of a low Young's modulus material having a lower Young's modulus than the material constituting the remaining parts of the substrate, thereby achieving the same effects as the configuration of the embodiment.

[0077] In addition, in the above embodiment, a cantilever structure is assumed, and a portion of the base of the cantilever structure is made of a low Young's modulus material, but this is not limited to this, and the configuration of the present disclosure can also be applied to sound wave generating devices other than a cantilever structure.

[0078] Fig. 22 is a perspective view of a sound wave generating device 1C according to a modified example, as viewed from above. Fig. 23 is a perspective view of the sound wave generating device 1C shown in Fig. 22, as viewed from below. The sound wave generating device 1C includes a support substrate 4C, a vibration membrane forming layer 6C, and a piezoelectric element 10C.

[0079] The support substrate 4C has a quadrangular shape (approximately rectangular) in a plan view. The support substrate 4C is made of, for example, a part of an SOI substrate. The support substrate 4C may be configured to include a silicon substrate and an oxide film layer. The support substrate 4C has a cavity (hollow) 5C (see FIG. 23) that is circular in a plan view at its center. The cavity 5C is, for example, cylindrical. The support substrate 4C has a first portion 701C, a second portion 702C, a third portion 703C, and a fourth portion 704C that are provided to surround the cavity 5C. The first portion 701C and the third portion 703C extend along the Y direction so as to sandwich the cavity 5C between them in the X direction. The second portion 702C and the fourth portion 704C extend along the X direction so as to sandwich the cavity 5C between them in the Y direction.

[0080] The vibration membrane forming layer 6C is formed on the support substrate 4C. The vibration membrane forming layer 6C may be composed of a laminated film in which a silicon layer and a silicon oxide film are laminated. The vibration membrane forming layer 6C includes a vibration membrane 7C facing the cavity 5C in a plan view, and a frame portion 8C formed to surround the cavity 5C. The vibration membrane 7C has a circular shape that is almost similar to the cavity 5C in a plan view. The frame portion 8C includes a first frame body 801C, a second frame body 802C, a third frame body 803C, and a fourth frame body 804C. The first frame body 801C is supported by the first portion 701C. The second frame body 802C is supported by the second portion 702C. The third frame body 803C is supported by the third portion 703C. The fourth frame body 804C is supported by the fourth portion 704C.

[0081] The piezoelectric element 10C is formed so as to be disposed on the vibration film forming layer 6C, specifically, on the vibration film 7C. The piezoelectric element 10C may include a lower electrode formed on the vibration film 7C, a piezoelectric film formed on the lower electrode, and an upper electrode formed on the piezoelectric film.

[0082] Here, in the sound wave generating device 1C, a slit penetrating the piezoelectric element 10C is not formed, and the device does not have a cantilever structure. In other words, the piezoelectric element 10C is not separated, and the piezoelectric element 10C is supported by a support substrate 4C or the like over its entire circumference. In the sound wave generating device 1C, the entire piezoelectric element 10C (particularly the central portion) vibrates so as to reciprocate in the vertical direction, vibrating the surrounding air and generating sound waves. In such a sound wave generating device 1C, a part of the portion supported by the support portion on the substrate is made of a low Young's modulus material having a lower Young's modulus than the material constituting the other portions of the substrate, and therefore, the same effect as the configuration according to the embodiment can be achieved.

[0083] Various embodiments of the present disclosure may be defined as follows:

[0084] (Supplementary Note 1, Embodiment, Figure 3, Figure 4) a substrate having a first surface and a second surface facing in opposite directions; A support portion that supports the first surface and is fixed to an installation surface; a piezoelectric film provided on the second surface and displaced together with the substrate in a first direction in response to application of a bias voltage; A piezoelectric film device, wherein a portion of the portion of the substrate supported by the supporting portion is made of a low Young's modulus material having a lower Young's modulus than a material constituting the remaining portion of the substrate.

[0085] (Supplementary Note 2, Embodiments, Figures 3 and 4) The substrate is The first surface has a first region supported by the support portion and a second region not supported by the support portion, and has a cantilever structure supported by the support portion only in the first region, A piezoelectric film device as described in Appendix 1, wherein a portion of a base portion of the cantilever structure is made of the low Young's modulus material.

[0086] (Appendix 3, embodiment, Figure 4) a region of the base portion on the second surface side is made of the low Young's modulus material, A piezoelectric film device as described in Appendix 1 or Appendix 2, wherein the region on the first surface side of the base portion is not made of the low Young's modulus material.

[0087] (Supplementary Note 4, embodiment, Fig. 5, Fig. 6) 4. The piezoelectric film device according to claim 1, wherein the low Young's modulus material is an oxide film.

[0088] (Appendix 5, embodiment) 5. The piezoelectric film device according to any one of claims 1 to 4, wherein the Young's modulus of the low Young's modulus material is half or less of the Young's modulus of the other portions.

[0089] (Supplementary Note 6, Embodiments, Fig. 3, Fig. 4) A transducer including the piezoelectric film device according to any one of claims 1 to 5.

[0090] (Appendix 7, embodiment, Figs. 5 to 15) A method for manufacturing the piezoelectric film device according to any one of Supplementary Note 1 to Supplementary Note 5, A first step of preparing a workpiece including a portion made of a first material, the portion made of the first material having a recess formed in a part of the portion; a second step of filling the recess with a low Young's modulus material having a Young's modulus lower than that of the first material; a third step of forming the piezoelectric film and an electrode on one end surface of the workpiece after the second step; A fourth step of forming the substrate and the support by processing the other end surface of the workpiece after the third step, In the fourth step, the other end surface of the workpiece is processed so that the region filled with the low Young's modulus material becomes a base portion of the cantilever structure.

[0091] (Appendix 8, embodiment, Fig. 6) 8. The manufacturing method according to claim 7, wherein in the second step, an oxide film of the low Young's modulus material is formed in the recess by thermally oxidizing the first material.

[0092] (Appendix 9, embodiment, FIG. 7) 9. The manufacturing method according to claim 7, wherein in the second step, after filling the recess with the low Young's modulus material, excess low Young's modulus material is ground off. [Explanation of symbols]

[0093] Reference Signs List 1, 1A, 1B, 1C...sound wave generating device, 2, 2B...substrate assembly, 2A...substrate assembly work in progress, 3...subframe, 3a...accommodating recess, 3b...through hole, 4, 4B, 4C...support substrate, 5, 5B, 5C...cavity, 6, 6B, 6C...vibration membrane forming layer, 7, 7B (7Ba to 7Bf)...vibration membrane, 8, 8B...frame, 9...slit, 9a...first portion, 9b...second portion, 9c...third portion, 10, 10B (10Ba to 10Bf), 10C...piezoelectric element, 11...lower electrode Electrode, 12...piezoelectric film, 13...upper electrode, 14...hydrogen barrier film, 15...interlayer insulating film, 16, 17...contact hole, 18...upper wiring, 18a...upper pad portion, 19...lower wiring, 19a...lower pad portion, 20...passivation film, 21...upper pad opening, 22...lower pad opening, 23...opening, 30...insulating film, 31...silicon oxide film, 32...silicon substrate, 33...oxide film layer, 34...silicon layer, 35...silicon oxide film, 41...support portion, 42...first portion, 43...second portion portion, 44...third portion, 53...opening, 80...substrate, 81...lower surface, 81x...first region, 81y...second region, 82...upper surface, 84...groove, 85...recess, 88...low Young's modulus material portion, 89...base portion, 90, 90Ba to 90Bf...piezoelectric film device, 101, 101A, 101B...workpiece, 101a...one end surface, 101b...other end surface, 111...lower electrode film, 112...piezoelectric material film, 113...upper electrode film, 131...first portion, 132...second portion, 133...third portion, 1 34...connecting portion, 140...hydrogen barrier film, 181...support frame, 182...first portion, 183...second portion, 184...third portion, 308...slit, 309...slit, 310...slit, 400...support substrate, 701, 701C...first portion, 702, 702C...second portion, 703, 703C...third portion, 704, 704C...fourth portion, 801, 801C...first frame, 802, 802C...second frame, 803, 803C...third frame, 804, 804C...fourth frame.

Claims

1. a substrate having a first surface and a second surface facing in opposite directions; A support portion that supports the first surface and is fixed to an installation surface; a piezoelectric film provided on the second surface and displaced together with the substrate in a first direction in response to application of a bias voltage; A piezoelectric film device, wherein a portion of the portion of the substrate supported by the supporting portion is made of a low Young's modulus material having a lower Young's modulus than a material constituting the remaining portion of the substrate.

2. the substrate has, as a region of the first surface, a first region supported by the support portion and a second region not supported by the support portion, and has a cantilever structure supported by the support portion only in the first region; The piezoelectric film device according to claim 1 , wherein a part of a base portion of the cantilever structure is made of the low Young's modulus material.

3. a region of the base portion on the second surface side is made of the low Young's modulus material, The piezoelectric film device according to claim 2 , wherein a region on the first surface side of the base portion is not made of the low Young's modulus material.

4. The piezoelectric film device according to claim 1 , wherein the low Young's modulus material is an oxide film.

5. 2. The piezoelectric film device according to claim 1, wherein the Young's modulus of the low Young's modulus material is equal to or less than half the Young's modulus of the other portions.

6. A transducer comprising the piezoelectric film device according to any one of claims 1 to 5.

7. A method for manufacturing the piezoelectric film device according to any one of claims 2 to 5, comprising the steps of: A first step of preparing a workpiece including a portion made of a first material, the portion being made of the first material and having a recess formed in a part of the portion; a second step of filling the recess with a low Young's modulus material having a Young's modulus lower than that of the first material; a third step of forming the piezoelectric film and an electrode on one end surface of the workpiece after the second step; A fourth step of forming the substrate and the support portion by processing the other end surface of the workpiece after the third step, In the fourth step, the other end surface of the workpiece is processed so that the region filled with the low Young's modulus material becomes a base portion of the cantilever structure.

8. The manufacturing method according to claim 7 , wherein in the second step, an oxide film of the low Young's modulus material is formed in the recess by thermally oxidizing the first material.

9. The manufacturing method according to claim 7 , wherein in the second step, after filling the recess with the low Young's modulus material, an excess of the low Young's modulus material is ground away.

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