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

Abstract

A piezoelectric film device (90) is provided with: a substrate (80) having a lower surface (81) and an upper surface (82) facing in opposite directions; a support part (41) that supports the lower surface (81) and is fixed to the installation surface; and a piezoelectric film (12) provided on the upper surface (82) and displaced in the vertical direction together with the substrate (80) in response to application of a bias voltage and a drive voltage, the substrate (80) having a first region (81x) supported by the support part (41) and a second region (81y) not supported by the support part (41) as regions of the lower surface (81), and the piezoelectric film (12) being displaced in the vertical direction together with the substrate (80) in a state in which the bias voltage and the drive voltage are not applied. The substrate (80) is formed in a warped manner such that the second region (81y) is positioned closer to the installation surface side (lower side) than the first region (81x).

Description

Technical Field

[0001] The present disclosure relates to a piezoelectric film device, a transducer, and a method for manufacturing the piezoelectric film device. Background Art

[0002] Japanese Patent Gazette No. 2021-52305 describes a transducer comprising: a supporting body having a cavity; a vibrating membrane arranged opposite to the cavity and capable of vibrating in a relative direction thereof; and a piezoelectric element formed on a surface of the vibrating membrane on the opposite side of the cavity, and forming a cantilever having a fixed end and a free end. Summary of the invention

[0003] Here, in the cantilever transducer as described above, since the restriction portion constitutes only the base portion of the cantilever, the vibration can be increased. On the other hand, in the cantilever transducer, the influence of sound leakage may become greater on the free end side.

[0004] The present disclosure provides a piezoelectric film device, a transducer, and a method for manufacturing the piezoelectric film device that can sufficiently vibrate and suppress sound leakage.

[0005] A piezoelectric film device on one side of the present invention comprises: a substrate having a first surface and a second surface facing opposite directions; a supporting portion which supports the first surface and is fixed to a setting surface; and a piezoelectric film which is set on the second surface and displaces in a first direction together with the substrate in response to application of a bias voltage and a drive voltage, wherein the substrate has a first region supported by the supporting portion and a second region which is not supported by the supporting portion and serves as a region of the first surface, and when no bias voltage and drive voltage are applied, the substrate is warped in such a manner that the second region is located closer to the setting surface side in the first direction than the first region. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 It is a top view of the acoustic wave generating device according to this embodiment.

[0007] Figure 2 It is a bottom view of the acoustic wave generating device according to this embodiment.

[0008] Figure 3 It is along Figure 1 The longitudinal cross-sectional view of the acoustic wave generating device taken along line III-III in FIG. 1 is a longitudinal cross-sectional view of the acoustic wave generating device to which no bias voltage is applied.

[0009] Figure 4 is a longitudinal cross-sectional view of the acoustic wave generating device to which a bias voltage is applied.

[0010] Figure 5 It is a longitudinal cross-sectional view of the acoustic wave generating device to which a bias voltage and a driving voltage are applied.

[0011] Figure 6 (a) is a diagram showing the displacement when the bias voltage is set to 0 and the driving voltage is applied. Figure 6 (b) indicates that the bias voltage is set to V a And the displacement when the driving voltage is applied.

[0012] Figure 7 It is a longitudinal cross-sectional view showing the process of manufacturing steps of the acoustic wave generating device.

[0013] Figure 8 It means next Figure 7 A longitudinal cross-sectional view of the process shown.

[0014] Fig. 9 It means next Figure 8 A longitudinal cross-sectional view of the process shown.

[0015] Fig.10 It means next Fig. 9 A longitudinal cross-sectional view of the process shown.

[0016] Fig.11 It means next Fig.10 A longitudinal cross-sectional view of the process shown.

[0017] Fig.12 It means next Fig.11 A longitudinal cross-sectional view of the process shown.

[0018] Fig.13 It means next Fig.12 A longitudinal cross-sectional view of the process shown.

[0019] Fig.14 It means next Fig.13 A longitudinal cross-sectional view of the process shown.

[0020] Fig.15 (a) is a diagram illustrating a sound wave generating device of a comparative example, Fig.15 (b) is a diagram illustrating an acoustic wave generating device of another comparative example.

[0021] Fig.16 This is a diagram showing an example of the sound pressure level corresponding to the state when the bias voltage is applied.

[0022] Fig.17 It is a diagram for explaining further effects of the acoustic wave generating device of this embodiment.

[0023] Fig.18 It is a top view of the acoustic wave generating device of a modified example.

[0024] Fig.19It is along Fig.18 A longitudinal cross-sectional view of the acoustic wave generating device taken along line XIX-XIX in FIG.

[0025] Fig. 20 It is a top view of an acoustic wave generating device 1B according to a modified example.

[0026] Fig.21 is from Fig. 20 The acoustic wave generating device 1B is shown in a perspective view as viewed from the upper side.

[0027] Fig. 22 is from Fig. 20 The acoustic wave generating device 1B is shown in a perspective view as viewed from the bottom side.

[0028] Explanation of symbols

[0029] 1, 1A, 1B...acoustic wave generating device; 2, 2B...substrate assembly; 2A...substrate assembly semi-finished product; 3...auxiliary frame; 3a...storage recess; 3b...through hole; 4, 4B...support substrate; 5, 5B...chamber; 6, 6B...vibration membrane forming layer; 7, 7B (7Ba to 7Bf)...vibration membrane; 8, 8B...frame; 9...slit; 9a...first part; 9b...second part; 9c...third part; 10, 10B (10Ba to 10Bf)...piezoelectric element; 11...lower 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 ... supporting portion; 42 ... first portion; 43 ... 2nd part; 44...3rd part; 53...opening; 80...substrate; 81...lower surface; 81x...1st region; 81y...2nd region; 82...upper surface; 90, 90Ba~90Bf...piezoelectric film device; 101...processing object member; 101a...one end face; 101b...other end face; 111...lower electrode film; 112...piezoelectric material film; 113...upper electrode film; 131...1st part; 132...2nd part; 133...3rd part; 134...connecting part; 14 0...hydrogen barrier film; 181...support frame; 182...part 1; 183...part 2; 184...part 3; 308...slit; 309...slit; 310...slit; 400...support substrate; 500, 600...acoustic wave generating device; 590, 690...piezoelectric film device; 701...part 1; 702...part 2; 703...part 3; 704...part 4; 801...first frame; 802...second frame; 803...third frame; 804...fourth frame. DETAILED DESCRIPTION

[0030] Hereinafter, the embodiments will be described with reference to the drawings. In the description, the same reference numerals are given to elements having the same elements or the same functions, and repeated descriptions are omitted.

[0031] Figure 1 1 is a top view of the acoustic wave generating device (transducer) according to the present embodiment. Figure 2 It is a bottom view of the acoustic wave generating device according to this embodiment. Figure 3 It is along Figure 1The longitudinal cross-sectional view of the acoustic wave generating device taken along line III-III in FIG. 1 is a longitudinal cross-sectional view of the acoustic wave generating device to which no bias voltage is applied.

[0032] The sound wave generating device 1 is, for example, a device including a 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 can 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 domains used are different in the audible region and the ultrasonic region. The piezoelectric film device 90 is, for example, a MEMS (Micro Electro Mechanical Systems) device that utilizes piezoelectric properties. Below, the sound wave generating device 1 is described as a speaker.

[0033] like Figure 1 to Figure 3 As shown, the acoustic wave generating device 1 includes a substrate assembly 2 and an auxiliary frame 3. The substrate assembly 2 includes a supporting substrate 4, a vibration film forming layer 6, and a piezoelectric element 10.

[0034] The support substrate 4 is a quadrilateral (roughly rectangular) when viewed from above. In the following, the long side direction of the support substrate 4, which is roughly rectangular when viewed from above, is set as the X direction, the short side direction is set as the Y direction, and the direction intersecting the X direction and the Y direction (that is, the thickness direction of the support substrate 4) is set as the Z direction for description. In the Z direction, the direction in which the piezoelectric element 10 is located with respect to the support substrate 4 is set as "up", and the direction in which the support substrate 4 is located with respect to the piezoelectric element 10 is set as "down" for description.

[0035] 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 formed on the surface thereof as a BOX layer, and a silicon (Si) layer 34 formed on the surface thereof as an active layer. In the structure of the present embodiment, a silicon oxide (SOI2) film 35 is formed on the surface of the silicon layer 34. In addition, in the support substrate 4, these include 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.

[0036] The support substrate 4 has a cavity (hole) 5 formed by a through hole penetrating in the Z direction. The cavity 5 has a rectangular parallelepiped shape with a quadrilateral opening 53 on the lower surface (bottom surface) side of the cavity 5 as a bottom surface in a plan view.

[0037] The support substrate 4 is configured to include a support portion 41, a first portion 42, a second portion 43, and a third portion 44. The support portion 41 supports the lower surface 81 of the substrate 80 as described later and is fixed to the installation surface. The support portion 41 and the second portion 43 extend along the Y direction in a manner of sandwiching the cavity 5 between each other in the X direction. The first portion 42 and the third portion 44 extend along the X direction in a manner of sandwiching the cavity 5 between each other in the Y direction. That is, the support portion 41, the first portion 42, the second portion 43, and the third portion 44 are arranged in a manner of surrounding the cavity 5. In the following, the direction in the X direction in which the second portion 43 is located with respect to the support portion 41 is set as "front", and the direction in which the support portion 41 is located with respect to the second portion 43 is set as "rear" for explanation.

[0038] The vibration film forming layer 6 is formed on the support substrate 4. The vibration film forming layer 6 is composed 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 film thickness of the silicon layer 34 is, for example, about 20 μm, and the film thickness of the silicon oxide film 35 is, for example, about 0.5 μm.

[0039] The vibration film forming layer 6 includes a vibration film 7 facing the cavity 5 in a plan view and a frame portion 8 formed so as to surround the cavity 5. The vibration film 7 is substantially in a rectangular shape similar to the cavity 5 in a plan view. The frame portion 8 is configured to include a support frame body 181 (see Figure 3 ), Part 1, 182 (ref. Figure 1 )、Part 2, 183 (refer to Figure 3 ) and Part 3, 184 (cf. Figure 1 ). The support frame 181 constitutes a part of the substrate 80 described later, and is supported by the 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.

[0040] In the manufacturing process, the slit 9 is formed before the cavity 5 is formed on the support substrate 4 (details will be described later). In the step of forming the slit 9, the slit 9 is formed to penetrate the vibration film 7 from the surface of the interlayer insulating film 15 (described later) formed on the vibration film forming layer 6 and reach the support substrate 4.

[0041] like Figure 1As shown, the slit 9 is composed of a first portion 9a formed along the X direction, a third portion 9c, and a second portion 9b formed along the Y direction. The first portion 9a is formed along a side extending along the X direction at one end side of the chamber 5 in the Y direction. The third portion 9c is formed along a side extending along the X direction at the other end side of the chamber 5 in the Y direction. The second portion 9b is formed so as to connect the front end portion of the first portion 9a and the front end portion of the third portion 9c.

[0042] The piezoelectric element 10 is formed after the hydrogen barrier film 14 is formed on the vibration film forming layer 6. In detail, the piezoelectric element 10 is formed so that at least a part thereof is arranged on the vibration film 7. In the present embodiment, the entire piezoelectric element 10 is arranged 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.

[0043] 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 thickness of the lower electrode 11 is about 200 nm, and the thickness of the upper electrode 13 is about 80 nm.

[0044] The piezoelectric film 12 is composed of, for example, lead zirconate titanate (PZT). The piezoelectric film 12 may also be composed of a niobium-doped lead zirconate titanate (PNZT) film, a lanthanum-doped lead zirconate titanate (PLZT) film, a strontium barium titanate (BST) film, a strontium bismuth tantalate (SBT) film, a strontium barium niobate (SBN) film, a lithium niobate (LiNbO3) film, a barium titanate (TiBaO3) film, a lanthanum strontium cobalt oxide (LSCO) film, a potassium dihydrogen phosphate (KDP) film, a potassium tantalate niobate (KTN) film, a lead magnesium niobate-lead titanate (PMN-PT) ceramic film, a lead zinc niobate-lead titanate (PZN-PT) ceramic film, aluminum nitride (AIN), zinc oxide (ZnO), lead titanate (PbTiO3), etc. The film thickness of the piezoelectric film 12 is, for example, about 2 μm.

[0045] A hydrogen barrier film 14 is formed on the vibration film 7 and the frame 8 constituting the vibration film forming layer 6. The hydrogen barrier film 14 is formed so as to cover the piezoelectric element 10 on the vibration film 7. The hydrogen barrier film 14 is composed of, for example, Al2O3 (aluminum oxide). The thickness of the hydrogen barrier film 14 is about 20nm to 100nm. The hydrogen barrier film 14 is provided to prevent performance degradation caused by hydrogen reduction of the piezoelectric film 12.

[0046] An interlayer insulating film 15 is stacked on the hydrogen barrier film 14. The interlayer insulating film 15 is composed of, for example, a film (TEOS film) containing tetraethoxysilane (TEOS). The interlayer insulating film 15 may also be composed 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.

[0047] An upper wiring 18 and a lower wiring 19 are formed on the interlayer insulating film 15 (see Figure 1 ). The upper wiring 18 and the lower wiring 19 are provided at the X-direction end (rear end) of the side where the support portion 41 is provided in the interlayer insulating film 15. The upper wiring 18 and the lower wiring 19 extend in the X-direction at intervals from each other in the Y-direction. The upper wiring 18 and the lower wiring 19 may also 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.

[0048] The front end of the upper wiring 18 is arranged above the rear end of the upper electrode 13. A contact hole 16 is formed between the upper wiring 18 and the upper electrode 13 and continuously penetrates the hydrogen barrier film 14 and the interlayer insulating film 15 (see Figure 1 and Figure 3 ). 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 in 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 arranged on the support frame 181 of the frame portion 8.

[0049] The front end of the lower wiring 19 is arranged above the rear end of the lower electrode 11. A contact hole 17 is formed between the lower wiring 19 and the lower electrode 11, which continuously penetrates the hydrogen barrier film 14 and the interlayer insulating film 15 (see Figure 1 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 in 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 arranged on the support frame 181 of the frame portion 8.

[0050] 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 composed of, for example, a film (TEOS film) containing tetraethoxysilane (TEOS). The passivation film 20 may also be composed 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. An upper pad opening 21 for exposing a portion of the upper pad portion 18a and a lower pad opening 22 for exposing a portion of the lower pad portion 19a are formed in the passivation film 20 (see FIG. 1 ). Figure 1 ) 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 .

[0051] In the substrate assembly 2, a substrate 80 having a rectangular shape in a plan view is formed by the vibration membrane 7 and the support frame 181 of the frame portion 8. The substrate 80 has a lower surface 81 (first surface) and an upper surface 82 (second surface) facing 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. In the substrate 80, the region serving as the lower surface 81 includes a first region 81x supported by the support portion 41 and a second region 81y not supported by the support portion 41.

[0052] The first region 81x is supported on the upper surface of the oxide film layer 33 of the support portion 41 and fixed to the upper surface. Supported on (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 components and being supported by the support portion 41. Fixed to the support portion 41 means, for example, being fixed to the support portion 41 directly or via some components, and being in a state of not being separated from the support portion 41. Fixed to the support portion 41 may be, for example, integrated with the support portion 41 or joined to the support portion 41. In addition, in the substrate 80, the entire region supported by the support portion 41 may not necessarily be fixed to the support portion 41, and only a portion of the supported region may be fixed to the support portion 41.

[0053] The piezoelectric film 12 is provided on the upper surface 82 of the substrate 80 (i.e., the upper surface of the silicon oxide film 35) via the lower electrode 11, and is displaced in the vertical direction (first direction) together with the substrate 80 in response to the application of a bias voltage and a drive voltage described later. The substrate 80, the support portion 41, and the piezoelectric element 10 are sometimes collectively referred to as a piezoelectric film device 90.

[0054] The piezoelectric film device 90 is configured as 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, in response to the application of the bias voltage and the drive voltage, the piezoelectric film 12 is displaced in the vertical direction, and the free end side (front end side) of the substrate 80 is displaced in the vertical direction together with the piezoelectric film 12.

[0055] like Figure 3As shown, in a state where no bias voltage and drive voltage are applied to the piezoelectric film 12, the substrate 80 is warped in such a manner that the second region 81y is located on the lower side (the side of the setting surface in the vertical direction) than the first region 81x. That is, in the piezoelectric film device 90 formed into a cantilever structure, in a position (neutral position) in a state where the piezoelectric film 12 is not deformed by an input electrical signal, the free end side of the substrate 80 is maintained in a warped posture in such a manner that it droops toward the chamber 5 side relative to the fixed end side. In a state where no bias voltage and drive voltage are applied to the piezoelectric film 12, the difference in the position of the front end portions of the first region 81x and the second region 81y in the vertical direction can be set to be greater than 100μm and less than 500μm, for example, when the length of the piezoelectric film device 90 in the X direction of the cantilever structure is about 3mm. In addition, the difference in the position of the first region 81x and the second region 81y can also be greater than the thickness of the silicon layer 34 constituting the substrate 80.

[0056] Moreover, if Figure 4 As shown, in a state where only a bias voltage is applied to the piezoelectric film 12 (a state where the bias voltage is applied and the driving voltage is not applied), the difference in the vertical direction between the front end portions of the first region 81x and the second region 81y may be 50 μm or less (i.e., substantially horizontal). In a state where only a bias voltage is applied to the piezoelectric film 12 (a state where the bias voltage is applied and the driving voltage is not applied), the difference in the vertical direction between the front end portions of the first region 81x and the second region 81y may be less than the thickness of the substrate 80 in the vertical direction (i.e., substantially horizontal).

[0057] And, by Figure 4 The substrate 80 shown in the figure is set in a substantially horizontal state, and a driving voltage is applied, and the free end side (front end side) of the substrate 80 is displaced in the vertical direction (refer to Figure 5 ). When the driving voltage is applied, the bias voltage is set constant (fixed value).

[0058] In terms of the performance of the piezoelectric film 12, in order to increase the vibration (sound) determined by the displacement, it is preferred that the operating voltage range does not span 0V and operates only on the positive side or the negative side. In the structure of the present embodiment, a bias voltage is applied in such a way that the operating voltage range of the piezoelectric film 12 becomes only on the positive side. Specifically, the bias voltage is set to more than half of the maximum driving voltage, and the operating voltage range of the piezoelectric film 12 is only on the positive side.

[0059] Figure 6 (a) is a diagram showing the displacement when the bias voltage is set to 0 and the driving voltage is applied. Figure 6 (b) indicates that the bias voltage is set to V α The displacement when the driving voltage is applied is shown in Figure 2. Figure 6As shown in (a), the bias voltage is set to 0 and the drive voltage (applied electric field) is set to 2V α In the case of α ~+V α , so the displacement of the piezoelectric film 12 is small, here d α On the other hand, Figure 6 As shown in (b), when the bias voltage is set to V α The driving voltage (applied electric field) is 2V α In the case of α The center is 0~2V α In this case, the displacement amount of the piezoelectric film 12 becomes greater than that in the case where the bias voltage is set to 0. α Big D β . In this way, even if V pp Similarly, by appropriately setting the bias voltage, the displacement of the piezoelectric film 12 can be increased, and the vibration (sound) of the acoustic wave generating device 1 can be increased.

[0060] Furthermore, in the acoustic wave generating device 1, the warping amount of the substrate 80 in the state where the bias voltage and the driving voltage are not applied (specifically, the downward drooping amount of the free end side of the substrate 80) is set so that the substrate 80 becomes substantially horizontal when the bias voltage and the driving voltage are not applied. Thus, at the moment when the driving voltage starts to be applied (in the state where only the bias voltage is applied), the substrate 80 can be brought into an appropriately horizontal state. Figure 3 to Figure 5 By comparing the various states of the substrate 80, it can be seen that the horizontal state of the substrate 80 refers to the state in which the gap between the front end portion (the end portion on the free end side) of the substrate 80 and the second portion 183 of the frame 8 is the smallest. Based on this state, the substrate 80 moves up and down in response to the application of the driving voltage, thereby minimizing the size of the gap when the substrate 80 moves up and down, and suppressing the influence of sound leakage.

[0061] like Figure 1 and Figure 3 As shown, the auxiliary frame 3 is, for example, composed of a silicon substrate having a silicon oxide film (not shown) formed on the lower surface and the upper surface. The auxiliary frame 3 is arranged on the substrate assembly 2 in a manner covering the piezoelectric film device 90. The auxiliary frame 3 is bonded to the frame portion 8 via an adhesive (not shown). The auxiliary frame 3 is configured to include a first portion 131, a second portion 132, a third portion 133, and a connecting portion 134, all of which are arranged upright in the Z direction. Figure 1As shown, the first portion 131 is formed along the X direction above the first portion 182 of the frame 8. The second portion 132 is formed along the Y direction above the second portion 183 of the frame 8. The third portion 133 is formed along the X direction above the third portion 184 of the frame 8. The connecting portion 134 is formed along the Y direction above the support frame 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 the storage recess 3a for storing the piezoelectric film device 90. A through hole 3b that functions as an emission port for the sound generated by the sound wave generating device 1 is formed above the storage recess 3a.

[0062] By providing the auxiliary frame 3, air leakage is prevented, and the sound performance of the sound wave generating device 1 is improved. In addition, by providing the auxiliary frame 3, the cantilever structure piezoelectric film device 90 can be protected. In addition, by providing the auxiliary frame 3, the rigidity of the chip is improved.

[0063] In such an acoustic 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 due to 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 serving as a fixed end as a fulcrum. If a voltage corresponding to a sound signal is continuously applied between the lower electrode 11 and the upper electrode 13, the piezoelectric film device 90 vibrates in a manner such that the free end side of the substrate 80 reciprocates in the up and down directions. By the vibration of such a piezoelectric film device 90, the air around the piezoelectric film device 90 is vibrated, generating acoustic waves. The acoustic waves propagate to the external space via the through hole 3b of the auxiliary frame 3. In addition, acoustic waves are also generated in the opposite direction.

[0064] Next, refer to Figure 7 to Figure 14 , an example of a manufacturing process of the acoustic wave generating device 1 of the present embodiment is described. Figure 7 to Figure 14 Yes means Figure 1 1 is a longitudinal sectional view (or a plan view) showing a manufacturing step of the acoustic wave generating device 1 according to the present embodiment.

[0065] First, if Figure 7As shown, the SOI substrate is subjected to thermal oxidation. 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. By thermal oxidation, a silicon oxide film 35 is formed on the surface of the silicon layer 34 opposite to the oxide film layer 33, and a silicon oxide film 31 is formed on the surface of the silicon substrate 32 opposite to the oxide film layer 33. Thus, a processing object member 101 having one end face 101a (the upper surface of the silicon oxide film 35) and the other end face 101b (the lower surface of the silicon oxide film 31) facing opposite directions is prepared (preparation step). In this way, the preparation step includes a step of obtaining the processing object member 101 by thermally oxidizing the SOI substrate. In the step of obtaining the processing object member, the film thickness of the processing object member 101 (specifically, the film thickness of the silicon oxide film 31 and the silicon oxide film 35) based on thermal oxidation may be controlled in such a manner that the free end side of the substrate 80 is formed in a state of being warped (drooped) downward in the state where each step is completed. The silicon substrate 32 and the oxide film layer 33 constitute the support substrate 4 , and the silicon layer 34 and the silicon oxide film 35 constitute the vibration film forming layer 6 .

[0066] Then, if Figure 8 As shown, after the hydrogen barrier film 14 is formed on one end surface 101a (upper surface of the silicon oxide film 35) of the processing target member 101, a lower electrode film 111 as a material film of the lower electrode 11, a piezoelectric material film 112 as a material film of the piezoelectric film 12, and an upper electrode film 113 as a material film of the upper electrode 13 are sequentially formed. Then, the upper electrode film 113, the piezoelectric material film 112, and the lower electrode film 111 are sequentially patterned by, for example, photolithography and etching, thereby forming the upper electrode 13, the piezoelectric film 12, and the lower electrode 11. Thus, the piezoelectric film 12 and the electrodes (the lower electrode 11 and the upper electrode 13) are formed on one end surface 101a of the processing target member 101, thereby forming the piezoelectric element 10 (film forming step).

[0067] Then, if Fig. 9 As shown in FIG. 1 , a hydrogen barrier film 140 is formed to cover the exposed surface of the piezoelectric element 10. The hydrogen barrier film 140 is composed of, for example, an aluminum oxide film. Then, an interlayer insulating film 15 is formed on the entire surface of the hydrogen barrier film 140. Further, by continuously etching the hydrogen barrier film 140 and the interlayer insulating film 15, contact holes 16 and 17 are formed (see FIG. 1 ). Figure 1 ). At this time, the interlayer insulating film 15 and the hydrogen barrier film 14 in the slit portion are also etched.

[0068] Then, a wiring film as a material film of the upper wiring 18 and the lower wiring 19 is formed on the interlayer insulating film 15 including 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 (see Figure 1 ). 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 composed of, for example, a TEOS film containing tetraethoxysilane (TEOS). The interlayer insulating film 15 and the passivation film 20 may also be composed of, for example, silicon nitride (SiN) or the like.

[0069] Then, if Fig.10 As shown, by photolithography and etching, an upper pad opening 21 for exposing a portion of the upper pad portion 18a and a lower pad opening 22 for exposing a portion of the lower pad portion 19a are formed in the passivation film 20 (see FIG. 1 ). Figure 1 ). By photolithography and etching, an opening 23 is formed in the interlayer insulating film 15 and the passivation film 20. The opening 23 may not be formed or may be partially opened. Then, by photolithography and etching, the vibration film forming layer 6 (silicon oxide film 35 and silicon layer 34) and the oxide film layer 33 are continuously penetrated to form a slit 9 reaching the silicon substrate 32. By forming the slit 9, the peripheral portion of the vibration film forming layer 6, i.e., the frame portion 8, and the central portion of the vibration film forming layer 6, i.e., the vibration film 7, are obtained, and the substrate assembly semi-finished product 2A before the cavity 5 is formed is obtained.

[0070] Then, if Fig.11 As shown, an adhesive (not shown) is applied to the opposite surface of the substrate assembly semi-finished product 2A in the auxiliary frame 3, and the auxiliary frame 3 is fixed to the substrate assembly semi-finished product 2A.

[0071] Then, if Fig.12 As shown, a support substrate 400 is temporarily attached to the upper surface of the auxiliary frame 3, and the silicon oxide film 31 and the silicon substrate 32 on the other end surface of the substrate assembly semi-finished product 2A (the processing target component after film formation) are polished, thereby thinning the silicon substrate 32.

[0072] Furthermore, if Fig.13 As shown, a resist mask (not shown) corresponding to the area where the cavity 5 is to be formed (more specifically, the area where the opening 53 is to be formed) is formed on the lower surface of the silicon substrate 32, and the silicon substrate 32 is etched from the lower surface. Thus, the acoustic wave generating device 1 is formed, which has the cavity 5 and includes the substrate 80, the support portion 41, and the piezoelectric film device 90 of the piezoelectric film 12 (forming process).

[0073] In a state where the steps so far are completed, the substrate 80 is warped so that the second region 81y is located lower than the first region 81x (the side of the installation surface in the vertical direction). In this way, the free end side of the substrate 80 is maintained in a warped posture in a drooping manner relative to the fixed end side. For example, the film thickness of the silicon oxide film 35 in the thermal oxidation treatment can be controlled as described above, and the film thickness of the insulating film 30 on the vibration film 7 can also be controlled. Alternatively, the residual film stress of the vibration film forming layer 6, the piezoelectric element 10, and the insulating film 30 can also be controlled by changing the film forming conditions or partially adding openings.

[0074] Finally, if Fig.14 As shown, by peeling off the supporting substrate 400 , the piezoelectric film device 90 becomes drivable, and the manufacture of the acoustic wave generating device 1 is completed.

[0075] Next, the effects of the piezoelectric film device 90 , the acoustic wave generating device 1 , and the method for manufacturing the piezoelectric film device 90 according to the present embodiment will be described.

[0076] First, refer to Fig.15 (a) and Fig.15 (b), the piezoelectric film device 590 ( Fig.15 (a)) and the piezoelectric film device 690 ( Fig.15 (b)) is explained. Fig.15 (a) is a diagram illustrating an acoustic wave generating device 500 of a comparative example, Fig.15 (b) is a diagram illustrating another comparative example of an acoustic wave generating device 600. Fig.15 (a) and Fig.15 In (b), for the sake of convenience of explanation, the structure of the acoustic wave generating devices 500 and 600 is greatly simplified, and the illustration of structures other than the piezoelectric film devices 590 and 690 schematically shown is omitted.

[0077] exist Fig.15 In the acoustic wave generating device 500 shown in (a), both ends of the piezoelectric film device 590 in the X direction are constrained. Since such a piezoelectric film device 590 does not have a free end, no gap is generated during vibration, and the influence of sound leakage can be suppressed. However, by constraining both ends of the piezoelectric film device 590 in the X direction, the vibration of the piezoelectric film device 590 becomes smaller.

[0078] On the other hand, Fig.15In the sound wave generating device 600 shown in (b), the piezoelectric film device 590 is made into a cantilever structure, and only the front end in the X direction is a free end. Such a piezoelectric film device can increase vibration. However, in the piezoelectric film device 590 with a cantilever structure, a gap is generated on the free end side, so the influence of sound leakage may become larger. In the piezoelectric film device 590 with a cantilever structure, when no bias voltage and drive voltage are applied, the vibrating substrate becomes approximately horizontal. If a bias voltage is applied from this state and then a drive voltage is applied, the piezoelectric film device 590 will bend greatly upward, so the above-mentioned gap becomes larger and the influence of sound leakage becomes larger. Therefore, a piezoelectric film device that can suppress sound leakage while fully vibrating is required.

[0079] like Figure 3 As shown, the piezoelectric film device 90 of the present embodiment includes: a substrate 80 having a lower surface 81 and an upper surface 82 facing opposite directions; a support portion 41, which supports the lower surface 81 and is fixed to a setting surface; and a piezoelectric film 12, which is disposed on the upper surface 82 and displaced in the up-down direction together with the substrate 80 in response to application of a bias voltage and a drive voltage, wherein the substrate 80 has a first region 81x supported by the support portion 41 and a second region 81y not supported by the support portion 41 as an area of ​​the lower surface 81, and when no bias voltage and drive voltage are applied, the substrate 80 is warped in such a manner that the second region 81y is located closer to the setting surface side (lower side) than the first region 81x.

[0080] As described above, if the substrate is set to a horizontal state when no bias voltage is applied, then if a bias voltage is applied thereafter, the substrate will bend upward and the gap will become larger. Furthermore, if a drive voltage is applied based on this state, the state with a large gap will continue and the influence of sound leakage will become larger. In this regard, as in the piezoelectric film device 90, when no bias voltage and drive voltage are applied, the free end side of the substrate 80 is configured to hang downward, whereby, if a bias voltage is applied thereafter, the substrate 80 will be displaced upward, and by setting the bias voltage, for example, a state in which the substrate 80 is approximately horizontal (a state in which a bias voltage is applied) can be set as a reference. The horizontal state of the substrate 80 refers to a state in which the gap is minimized (refer to Figure 4 ), so by applying a driving voltage based on this state, the influence of leakage sound can be suppressed in the piezoelectric film device 90 with a cantilever structure. That is, according to the piezoelectric film device 90 of this embodiment, compared with a general piezoelectric film device with a cantilever structure (a piezoelectric film device 690 in which the substrate is in a substantially horizontal state when no bias voltage is applied), the influence of leakage sound can be suppressed. Moreover, according to the piezoelectric film device 90 with a cantilever structure, the vibration can be increased compared with the piezoelectric film device 590 in which both ends are constrained. As described above, according to the piezoelectric film device 90 of this embodiment, it is possible to fully vibrate and suppress leakage sound.

[0081] Reference Fig.16 A description will be given of a case where sound leakage is most suppressed and the sound pressure level increases when the substrate 80 is in a horizontal state when a bias voltage is applied. Fig.16 This is a diagram showing an example of the sound pressure level corresponding to the state when the bias voltage is applied. Since the sound leakage is most affected by the bass, the sound pressure level at 20 Hz is used as an indicator. Fig.16 In FIG. 1 , the horizontal axis represents the bias voltage, the vertical axis (left) represents the warping amount of the free end side of the piezoelectric film device 90 of the cantilever structure from the horizontal position, and the vertical axis (right) represents the sound pressure level at 20 Hz of the bass. Fig.16 In the example shown, the sound pressure level is maximum (sound leakage is minimum) when the bias voltage is set to 13 V and the warpage amount on the free end side of the piezoelectric film device 90 is set to 0 (i.e. horizontal). Thus, it can be said that when the substrate 80 is in a horizontal state, sound leakage is suppressed to the maximum extent and the sound pressure level increases.

[0082] In a state where no bias voltage and drive voltage are applied, the difference in position between the first region 81x and the second region 81y in the vertical direction may be greater than the thickness of the silicon layer 34 constituting the substrate 80, or may be greater than 100 μm and less than 500 μm. By setting the droop amount to this degree, the substrate 80 can be placed in an appropriately horizontal state when a bias voltage is applied.

[0083] When the bias voltage is applied and the driving voltage is not applied, the difference in position between the first region 81x and the second region 81y in the vertical direction may be less than the vertical thickness of the substrate 80. According to such a structure, the substrate 80 becomes substantially horizontal when the bias voltage is applied, so that sound leakage can be appropriately suppressed.

[0084] When the bias voltage is applied and the drive voltage is not applied, the vertical position difference between the first region 81x and the second region 81y may be 50 μm or less. With such a structure, the substrate 80 becomes substantially horizontal when the bias voltage is applied, so that sound leakage can be appropriately suppressed.

[0085] When the driving voltage is applied, the bias voltage may be set to a fixed value, thereby making it possible to stably operate the piezoelectric film device 90 under pre-set conditions.

[0086] like Figure 1 As shown, the acoustic wave generating device 1 of the present embodiment is configured to include one piezoelectric film device 90. In such an acoustic wave generating device 1, since the piezoelectric film device 90 is included, the piezoelectric film device 90 can be sufficiently vibrated and sound leakage can be suppressed.

[0087] The manufacturing method of the piezoelectric film device 90 of the present embodiment includes: a step of preparing a processing object member 101 having one end face 101a and another end face 101b facing opposite directions; a step of forming a piezoelectric film 12 and electrodes (upper electrode 13, lower electrode 11) on one end face 101a of the processing object member 101; and a step of forming a substrate 80 and a support portion 41 by processing the other end face of the processing object member 101 after the film formation, that is, the silicon oxide film 31 and the silicon substrate 32. When each step is completed, the substrate 80 is warped in a manner that the second region 81y is located closer to the setting surface side (below) than the first region 81x. According to such a manufacturing method, the piezoelectric film device 90 that plays the above role can be appropriately manufactured.

[0088] The preparation step includes a step of obtaining the processing object member 101 by thermally oxidizing the SOI substrate. In the step of obtaining the processing object member, the film thickness of the processing object member 101 by thermal oxidation can be controlled so that the substrate 80 is formed to be warped downward in the state where each step is completed. According to such a manufacturing method, the piezoelectric film device 90 having the substrate 80 formed to be warped downward can be easily manufactured by controlling the film thickness during thermal oxidation.

[0089] The effects of the acoustic wave generating device 1 of the present embodiment are not limited to those described above. For example, the acoustic wave generating device 1 of the present embodiment can improve the damage resistance compared to the acoustic wave generating device including the piezoelectric film device of the cantilever structure of the comparative example. Fig.17 It is a diagram for explaining further effects (improvement of damage resistance) of the acoustic wave generating device 1 of the present embodiment. Fig.17 (a) schematically shows the operation of the piezoelectric film device 90 having a cantilever structure according to the present embodiment. Fig.17 (b) schematically shows the operation of the cantilever structure piezoelectric film device of the comparative example. As described above, the piezoelectric film device has three states: no application (no bias voltage and drive voltage applied), bias voltage applied (bias voltage applied and drive voltage not applied), and bias voltage applied and driven (bias voltage and drive voltage applied). Fig.17 As shown in (b), if the substrate of the piezoelectric film device is in a horizontal state when no voltage is applied, the substrate will bend upward when the bias voltage is applied, and the substrate will be further warped upward when the bias voltage is applied and driven. As a result, stress is concentrated at the fixed end of the piezoelectric film device, and the piezoelectric film device may be damaged by the driving voltage.

[0090] Regarding this, Fig.17As shown in (a), in the piezoelectric film device 90 of the present embodiment, as described above, the free end side of the piezoelectric film device 90 hangs downward in the non-applied state, so even if the bias voltage is applied or the bias voltage is applied and driven, the warping amount of the substrate 80 is smaller than that of the above-mentioned comparative example. Therefore, the stress concentration at the fixed end can be alleviated, and the piezoelectric film device can be appropriately suppressed from being destroyed by the driving voltage.

[0091] The embodiments of the present invention are described above, but the present invention is not limited to the above embodiments. For example, in the above embodiments, the acoustic wave generating device 1 includes a piezoelectric film device 90, but the structure of the acoustic wave generating device is not limited to this. The acoustic wave generating device may include a plurality of (for example, a pair of) piezoelectric film devices.

[0092] Fig.18 It is a top view of an acoustic wave generating device 1A according to a modified example. Fig.19 It is along Fig.18 A longitudinal cross-sectional view of the acoustic wave generating device 1A taken along line XIX-XIX in FIG. Fig.18 and Fig.19 As shown, the acoustic wave generating device 1A includes two (a pair of) piezoelectric film devices 90, 90. The structure of the piezoelectric film device 90 may also be as described above. The pair of piezoelectric film devices 90, 90 is arranged, for example, so that the free end sides face each other.

[0093] In addition, application examples of the piezoelectric film device are not limited to sound wave generating devices (speakers or ultrasonic transducers), and for example, the piezoelectric film device may be other various transducers, a MEMS mirror, or an inkjet head.

[0094] In addition, in the above embodiment, the case where the acoustic wave generating device 1 includes the substrate assembly 2 and the auxiliary frame 3 is described, but the present invention is not limited thereto, and the acoustic wave generating device may not include the auxiliary frame.

[0095] Fig. 20 It is a top view of an acoustic wave generating device 1B according to a modified example. Fig.21 is from Fig. 20 The acoustic wave generating device 1B is shown in a perspective view as viewed from the upper side. Fig. 22 is from Fig. 20 The acoustic wave generating device 1B is shown in a perspective view viewed from the bottom. The acoustic wave generating device 1B does not include an auxiliary frame, but includes only a substrate assembly 2B. The substrate assembly 2B includes a support substrate 4B, a vibration film forming layer 6B, and a piezoelectric element 10B.

[0096] The support substrate 4B is quadrilateral (roughly rectangular) in plan view. The support substrate 4B is made of, for example, a portion of an SOI substrate. The support substrate 4B may also be configured to include a silicon substrate and an oxide film layer. The support substrate 4B has a cavity (hole) 5B in a regular hexagonal shape in plan view at its center (see Fig. 22 ). The chamber 5B is, for example, in the shape of a hexagonal prism. The support substrate 4B includes a first portion 701, a second portion 702, a third portion 703, and a fourth portion 704, which are arranged to surround the chamber 5B. The first portion 701 and the third portion 703 extend along the Y direction so as to sandwich the chamber 5B in the X direction. The second portion 702 and the fourth portion 704 extend along the X direction so as to sandwich the chamber 5B in the Y direction.

[0097] The vibration film forming layer 6B is formed on the supporting substrate 4B. The vibration film forming layer 6B can be composed of a laminated film in which a silicon layer and a silicon oxide film are laminated. The vibration film forming device 6B includes a vibration film 7B opposite to the chamber 5B when viewed from above, and a frame portion 8B formed in a manner to surround the chamber 5B. The vibration film 7B is a regular hexagonal shape roughly similar to the chamber 5B when viewed from above. The frame portion 8B is configured to include 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 part 701. The second frame body 802 is supported by the second part 702. The third frame body 803 is supported by the third part 703. The fourth frame body 804 is supported by the fourth part 704.

[0098] The piezoelectric element 10B is formed so as to be arranged on the vibration film forming layer 6B, more 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.

[0099] Here, in the sound wave generating device 1B, slits 308, 309, and 310 are formed that penetrate the piezoelectric element 10B and the vibrating membrane 7B. The slit 308 extends in the Y direction. Considering the extending direction of the slit 308, the slits 309 and 310 extend respectively in a manner that the area of ​​the piezoelectric element 10B is divided into six equal parts. That is, the slits 308, 309, and 310 extend respectively in a manner that the area of ​​the piezoelectric element 10B is divided 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 vibrating membrane 7B is separated into six vibrating membranes 7Ba to 7Bf. As a result, the sound wave generating device 1B has six piezoelectric film devices 90Ba to 90Bf.

[0100] In each of such piezoelectric film devices 90Ba to 90Bf, when no bias voltage and drive voltage are applied, the "substrate" is warped in such a manner that the second region is located closer to the setting surface than the first region, which can also achieve the same effect as the structure of the embodiment.

[0101] Various embodiments in the present disclosure can be defined as the following supplementary notes.

[0102] (Note 1, implementation method, Figure 3 )

[0103] A piezoelectric film device, characterized in that it comprises: a substrate having a first surface and a second surface facing in opposite directions;

[0104] a supporting portion that supports the first surface and is fixed to the installation surface; and

[0105] a piezoelectric film disposed on the second surface and displaced in the first direction together with the substrate in response to application of a bias voltage and a drive voltage;

[0106] The substrate has, as regions of the first surface, a first region supported by the support portion and a second region not supported by the support portion.

[0107] In a state where the bias voltage and the drive voltage are not applied, the substrate is warped so that the second region is located closer to the installation surface side in the first direction than the first region.

[0108] (Note 2, implementation method, Figure 3 )

[0109] The piezoelectric film device according to Supplement 1, wherein, when the bias voltage and the drive voltage are not applied, the difference in position between the first region and the second region in the first direction is greater than the thickness in the first direction of the active layer constituting the substrate.

[0110] (Appendix 3, Implementation Method, Figure 3 )

[0111] The piezoelectric film device according to Supplementary Note 1 or 2, wherein, in a state where the bias voltage and the drive voltage are not applied, a positional difference between the first region and the second region in the first direction is greater than or equal to 100 μm and less than or equal to 500 μm.

[0112] (Appendix 4, Implementation Method, Figure 4 )

[0113] A piezoelectric film device according to any one of Notes 1 to 3, wherein, when the bias voltage is applied and the driving voltage is not applied, the difference between the positions of the first region and the second region in the first direction is less than the thickness of the substrate in the first direction.

[0114] (Note 5, Implementation method, Figure 4 )

[0115] The piezoelectric film device according to any one of Supplementary Notes 1 to 4, wherein, in a state where the bias voltage is applied and the drive voltage is not applied, a positional difference between the first region and the second region in the first direction is 50 μm or less.

[0116] (Supplementary Note 6, Implementation Method)

[0117] The piezoelectric film device according to any one of Supplementary Notes 1 to 5, wherein the bias voltage is a fixed value when the driving voltage is applied.

[0118] (Appendix 7, Implementation Method, Figure 3 )

[0119] A transducer comprising the piezoelectric film device according to any one of Supplementary Notes 1 to 6.

[0120] (Appendix 8, Implementation Method, Figure 7 to Figure 14 )

[0121] The method for manufacturing the piezoelectric film device as described in any one of Supplementary Notes 1 to 6 comprises:

[0122] A step of preparing a workpiece having one end surface and another end surface facing in opposite directions to each other;

[0123] a step of forming the piezoelectric film and the electrode on one end surface of the member to be processed; and

[0124] The step of forming the substrate and the support portion by processing the other end surface of the processing target member after film formation,

[0125] In a state where each step is completed, the substrate is warped so that the second region is located closer to the installation surface side in the first direction than the first region.

[0126] (Appendix 9, Implementation Methods, Figure 7 )

[0127] The manufacturing method according to Supplementary Note 8, wherein the preparation step includes a step of obtaining the processing target member by thermally oxidizing a substrate containing silicon,

[0128] In the step of obtaining the member to be processed, the film thickness of the member to be processed by thermal oxidation is controlled so that the substrate is formed to be warped in a state where each step is completed.

Claims

1. A piezoelectric film device, in, include: A substrate having a first surface and a second surface facing in opposite directions; a supporting portion that supports the first surface and is fixed to the installation surface; and a piezoelectric film disposed on the second surface and displaced in the first direction together with the substrate in response to application of a bias voltage and a drive voltage, The substrate has, as regions of the first surface, a first region supported by the support portion and a second region not supported by the support portion. In a state where the bias voltage and the drive voltage are not applied, the substrate is warped so that the second region is located closer to the installation surface side in the first direction than the first region.

2. The piezoelectric film device according to claim 1, wherein: In a state where the bias voltage and the drive voltage are not applied, a difference in position between the first region and the second region in the first direction is equal to or greater than a thickness in the first direction of an active layer constituting the substrate.

3. The piezoelectric film device according to claim 1 or 2, wherein: In a state where the bias voltage and the drive voltage are not applied, a positional difference between the first region and the second region in the first direction is greater than or equal to 100 μm and less than or equal to 500 μm.

4. The piezoelectric film device according to any one of claims 1 to 3, wherein: In a state where the bias voltage is applied and the drive voltage is not applied, a difference between the positions of the first region and the second region in the first direction is equal to or less than a thickness of the substrate in the first direction.

5. The piezoelectric film device according to any one of claims 1 to 4, wherein: In a state where the bias voltage is applied and the drive voltage is not applied, a positional difference between the first region and the second region in the first direction is 50 μm or less.

6. The piezoelectric film device according to any one of claims 1 to 5, wherein: When the driving voltage is applied, the bias voltage is a fixed value.

7. A transducer, wherein: A piezoelectric film device comprising any one of claims 1 to 6.

8. A method for manufacturing a piezoelectric film device, wherein: The piezoelectric film device is the piezoelectric film device according to any one of claims 1 to 6, The manufacturing method comprises: A step of preparing a workpiece having one end surface and another end surface facing in opposite directions to each other; a step of forming the piezoelectric film and the electrode on one end surface of the member to be processed; and The step of forming the substrate and the support portion by processing the other end surface of the processing target member after film formation, In a state where each step is completed, the substrate is warped so that the second region is located closer to the installation surface side in the first direction than the first region.

9. The manufacturing method according to claim 8, wherein: The preparation step includes a step of obtaining the processing target member by thermally oxidizing a substrate containing silicon. In the step of obtaining the processing target member, the film thickness of the processing target member by thermal oxidation is controlled so that the substrate is warped in a state where each step is completed.

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