Piezoelectric actuator and method for manufacturing the same
The piezoelectric actuator design redistributes stress at the connection point by positioning the outer edge of the first layer closer to the support, improving reliability and displacement performance.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- ROHM CO LTD
- Filing Date
- 2024-11-19
- Publication Date
- 2026-05-29
AI Technical Summary
In piezoelectric actuators with a cantilever structure, stress concentrates at the connection point between the diaphragm and the support, leading to potential failure when the diaphragm displaces significantly during resonance.
A piezoelectric actuator design with a diaphragm, first support, thin film, and additional supports is engineered to distribute stress by positioning the outer edge of the first layer closer to the support rather than the connection point, achieved through selective etching of the side surfaces.
The stress on the connection point is reduced, enhancing the reliability and displacement capability of the diaphragm under voltage application, allowing for increased displacement or reduced failure risk.
Smart Images
Figure 2026088902000001_ABST
Abstract
Description
Technical Field
[0005]
[0001] Embodiments of the present disclosure relate to piezoelectric actuators and methods for manufacturing the same.
Background Art
[0002] Conventionally, a technology of a micro electro mechanical system (MEMS) for fabricating a mechanical structure on a semiconductor substrate such as silicon using semiconductor manufacturing technology has been provided. MEMS devices to which MEMS technology is applied include, for example, a piezoelectric actuator and a piezoelectric transducer that drive a diaphragm with a piezoelectric body. Some of these have a structure called a cantilever and are applied to heads of inkjet printers, speakers, ultrasonic elements, etc. (see Patent Document 1).
[0003] Also, the piezoelectric element of the MEMS device may be fabricated using a silicon on insulator (SOI) wafer in which a buried layer composed of a buried oxide (BOX) layer and an active layer is formed on the surface of the silicon substrate (see Patent Document 2).
Prior Art Documents
Patent Documents
[0004]
Patent Document 1
Patent Document 2
[0005] [Summary] However, in a piezoelectric actuator having a cantilever structure, stress concentrates at the connection portion between the diaphragm and the support portion during driving, and when the displacement of the diaphragm becomes large during resonance or the like, a large stress may be applied to the connection portion of the diaphragm.
[0006] The object of this disclosure is to provide a piezoelectric actuator having a structure that can relieve stress on the connection point between the diaphragm and the support, and a method for manufacturing the same.
[0007] One aspect of the present disclosure is a piezoelectric actuator comprising a diaphragm, a first support, a thin film including a piezoelectric film, a first layer, and a second support. The diaphragm has a first main surface. The first support has a second main surface oriented in the same direction as the first main surface and is connected to the diaphragm via a connection point. The thin film including the piezoelectric film is arranged on the first main surface. The first layer has a fourth main surface connected to a third main surface of the first support, which is oriented in the opposite direction to the second main surface. The second support has a sixth main surface connected to a fifth main surface of the first layer, which is oriented in the opposite direction to the fourth main surface, and supports the first support via the first layer. The diaphragm has a free end at a position opposite to the connection point. Viewed from the direction normal to the second main surface, the outer edge of the fourth main surface closest to the connection point is located on the side of the first support rather than the connection point.
[0008] Another aspect of the present disclosure is a method for manufacturing the piezoelectric actuator described above. The manufacturing method involves etching the side surface of the first layer that connects the fourth main surface and the fifth main surface, the side surface closest to the connection point, using etching with a selectivity ratio for the diaphragm, the first support part, and the second support part. The manufacturing method sets the position of the outer edge of the fourth main surface that is closest to the connection point, as viewed from the direction normal to the second main surface, on the side of the first support part that is closer to the connection point. [Brief explanation of the drawing]
[0009] [Figure 1A] Figure 1A is a plan view of the piezoelectric actuator according to the first embodiment, as seen from the top surface. [Figure 1B] Figure 1B is a plan view of the piezoelectric actuator according to the first embodiment, as seen from the bottom. [Figure 1C] Figure 1C is a plan view of the first and second layers of the piezoelectric actuator according to the first embodiment, as seen from the top surface. [Figure 2] Figure 2 is a cross-sectional view of the piezoelectric actuator according to the first embodiment along line II-II. [Figure 3]Figure 3 is a cross-sectional view of the piezoelectric actuator according to the first embodiment along line III-III. [Figure 4] Figure 4 shows the stress in the piezoelectric actuator according to the first embodiment. [Figure 5] Figure 5 shows the stress in a comparative piezoelectric actuator. [Figure 6] Figure 6 shows the relationship between the position of the outer edge of the first layer of the piezoelectric actuator according to the first embodiment and the stress. [Figure 7A] Figure 7A is a diagram illustrating the manufacturing process of a piezoelectric actuator according to the first embodiment. [Figure 7B] Figure 7B is a diagram illustrating the manufacturing process of a piezoelectric actuator according to the first embodiment. [Figure 7C] Figure 7C is a diagram illustrating the manufacturing process of a piezoelectric actuator according to the first embodiment. [Figure 7D] Figure 7D is a diagram illustrating the manufacturing process of a piezoelectric actuator according to the first embodiment. [Figure 7E] Figure 7E is a diagram illustrating the manufacturing process of a piezoelectric actuator according to the first embodiment. [Figure 7F] Figure 7F is a diagram illustrating the manufacturing process of a piezoelectric actuator according to the first embodiment. [Figure 8A] Figure 8A is a diagram illustrating the details of the cross-sectional shapes of the first and second layers of the piezoelectric actuator according to the first embodiment. [Figure 8B] Figure 8B is a diagram illustrating the details of the cross-sectional shapes of the first and second layers of the piezoelectric actuator according to the first embodiment. [Figure 8C] Figure 8C is a diagram illustrating the details of the cross-sectional shapes of the first and second layers of the piezoelectric actuator according to the first embodiment. [Figure 9] Figure 9 is a plan view of the piezoelectric actuator according to the second embodiment, as seen from the top surface. [Figure 10] Figure 10 is a cross-sectional view of the piezoelectric actuator according to the second embodiment, along XX. [Figure 11A] FIG. 11A is a diagram for explaining the manufacturing process of the piezoelectric actuator according to the second embodiment. [Figure 11B] FIG. 11B is a diagram for explaining the manufacturing process of the piezoelectric actuator according to the second embodiment. [Figure 11C] FIG. 11C is a diagram for explaining the manufacturing process of the piezoelectric actuator according to the second embodiment. [Figure 12] FIG. 12 is a cross-sectional view of the piezoelectric actuator according to the third embodiment.
[0010] [Detailed Description] Embodiments will be described with reference to the drawings. In the descriptions of the drawings below, the same or similar parts are denoted by the same or similar reference numerals and the description thereof will be omitted. The drawings are schematic.
[0011] Also, the embodiments shown below are examples of devices or methods for embodying the technical idea, and do not specify the materials, shapes, structures, arrangements, etc. of each component. Various changes can be made to this embodiment within the scope of the claims.
[0012] [First Embodiment] (Configuration of Piezoelectric Actuator) FIG. 1A is a plan view of the piezoelectric actuator 1 according to the first embodiment as viewed from the normal direction of the top surface. FIG. 1B is a plan view of the piezoelectric actuator 1 according to the first embodiment as viewed from the bottom surface. FIG. 1C is a plan view of a part of the layers included in the piezoelectric actuator 1 according to the first embodiment as viewed from the normal direction of the top surface. FIG. 2 is a cross-sectional view of the piezoelectric actuator 1 according to the first embodiment taken along line II-II of FIGS. 1A to 1C.
[0013] In the following description, an XYZ coordinate system, which is an example of a rectangular coordinate system, is used. That is, a plane parallel to the main surface of the diaphragm 11 constituting the piezoelectric actuator 1 is defined as the XY plane, and the normal direction perpendicular to the XY plane is defined as the Z direction. Also, the X axis and the Y axis are two perpendicular directions in the XY plane.
[0014] In Figure 1A, the piezoelectric actuator 1 comprises a diaphragm 11, a first support portion 21 connected to the diaphragm 11 via a connection point 18, and peripheral members 22 arranged around the diaphragm 11 with a gap 17 between them, excluding the connection point 18. The connection point 18 coincides with a line segment connecting both ends of the gap 17.
[0015] Here, the direction in which the line segment of connection point 18 extends is defined as the Y direction, and the direction perpendicular to the line segment of connection point 18 and pointing from the first support part 21 toward the diaphragm 11 is defined as the X direction. The shape of the diaphragm 11 is a rectangle with a length L in the X direction and a width W in the Y direction. Figure 1A illustrates the case where the length L of the diaphragm 11 is greater than the width W, but the shape of the diaphragm 11 is not limited to this, and the ratio of length L to width W may be, for example, in the range of L / W = 0.1 or more and 10 or less. The side of the outer edge of the diaphragm 11 that faces the connection point 18 is the free end 19 of the diaphragm 11.
[0016] In Figure 2, the diaphragm 11, the first support portion 21, and the peripheral member 22 are arranged at the same height in the Z direction, and as shown in Figure 1A, the first support portion 21 and the peripheral member 22 are connected by a straight line extending in the Y direction from the line segment of the connection point 18 of the diaphragm 11. The diaphragm 11, the first support portion 21, and the peripheral member 22 may contain, for example, silicon Si, or may be formed from, for example, a Si active layer in an SOI wafer.
[0017] Referring to Figures 1A and 2, the structure and shape of the top surface of the diaphragm 11, the first support portion 21, and the peripheral member 22 will be described.
[0018] In Figure 2, the top surface of the diaphragm 11 facing the Z direction is referred to as the first main surface 11a, and the top surface of the first support portion 21 facing the Z direction is referred to as the second main surface 21a. As shown in Figures 1A and 2, the piezoelectric actuator 1 further comprises a lower electrode 12 positioned on the first main surface 11a of the diaphragm 11 and the second main surface 21a of the first support portion 21, a piezoelectric film 13 positioned on the main surface of the lower electrode 12, and an upper electrode 14 positioned on the main surface of the piezoelectric film 13. Although not shown in Figure 1A, as shown in Figure 2, an insulating film 20 is positioned between the diaphragm 11 and the first support portion 21 and the lower electrode 12. Furthermore, the insulating film 20 is positioned on the portions of the lower electrode 12, piezoelectric film 13, and upper electrode 14 that are exposed when viewed from the normal direction of the first main surface 11a and the second main surface 21a.
[0019] The piezoelectric film 13 may contain, for example, lead zirconate titanate (PZT) or aluminum nitride (AlN). The lower electrode 12 and upper electrode 14 may contain, for example, conductive metals such as platinum (Pt), molybdenum (Mo), iridium (Ir), or titanium (Ti). The insulating film 20 may contain, for example, silicon dioxide (SiO2). The insulating film 20 serves as both an interlayer insulating film and a protective film.
[0020] A wiring electrode 15 is positioned on a portion of the upper surface of an insulating film 20 located on the upper surface of the lower electrode 12. A through-hole is provided in the insulating film 20 between the wiring electrode 15 and the lower electrode 12, and the wiring electrode 15 is connected to the lower electrode 12 through the through-hole. Additionally, a wiring electrode 16 is positioned on a portion of the upper surface of an insulating film 20 located on the upper surface of the upper electrode 14. A through-hole is provided in the insulating film 20 between the wiring electrode 16 and the upper electrode 14, and the wiring electrode 16 is connected to the upper electrode 14 through the through-hole.
[0021] Next, the structure and shape of the bottom side of the diaphragm 11, the first support part 21, and the peripheral member 22 will be described with reference to Figures 1A, 1B, 1C, and 2.
[0022] In Figure 2, the bottom surface of the first support portion 21 facing in the opposite direction to the second main surface 21a is referred to as the third main surface 21b. The piezoelectric actuator 1 further comprises a first layer 31 connected to the third main surface 21b of the first support portion 21, and a second support portion 42 connected to the first layer 31. The first layer 31 has a fourth main surface 31a connected to the third main surface 21b of the first support portion 21, and a fifth main surface 31b facing in the opposite direction to the fourth main surface 31a. The second support portion 42 has a sixth main surface 42a connected to the fifth main surface 31b of the first layer 31. The second support portion 42 supports the first support portion 21 via the first layer 31.
[0023] In Figure 2, the top surface of the peripheral member 22 facing the Z direction is referred to as the seventh main surface 22a, and the bottom surface facing the opposite direction from the seventh main surface 22a is referred to as the eighth main surface 22b. The piezoelectric actuator 1 further comprises a second layer 32 connected to the eighth main surface 22b of the peripheral member 22, and a third support portion 43 connected to the second layer 32. The second layer 32 has a ninth main surface 32a connected to the eighth main surface 22b of the peripheral member 22, and a tenth main surface 32b facing the opposite direction from the ninth main surface 32a. The third support portion 43 has an eleventh main surface 43a connected to the tenth main surface 32b of the second layer 32. The third support portion 43 supports the peripheral member 22 via the second layer 32.
[0024] As shown in Figure 1B, the second support portion 42 and the third support portion 43 are positioned to overlap with the first support portion 21 and the peripheral member 22 in Figure 1A, respectively, when viewed from the bottom surface of the piezoelectric actuator 1. In Figure 2, the second support portion 42 and the third support portion 43 are positioned at the same height in the Z direction, and as shown in Figure 1B, the second support portion 42 and the third support portion 43 are connected by a straight line extending in the Y direction from the straight line of the connection point 18 of the diaphragm 11. The second support portion 42 and the third support portion 43 may contain, for example, Si, and may be formed from, for example, a Si support substrate in an SOI wafer.
[0025] As described above with reference to Figure 2, the first layer 31 is positioned between the first support portion 21 and the second support portion 42, and the second layer 32 is positioned between the peripheral member 22 and the third support portion 43. The first layer 31 and the second layer 32 are positioned at the same height in the Z direction. Figures 1A and 1B show the positions where the first layer 31 and the second layer are positioned with dashed lines. Figure 1C shows a plan view of the piezoelectric actuator 1 with the first layer 31 and the second layer 32 extracted and viewed from the top surface. As shown in Figures 1B and 1C, the first layer 31 and the second layer 32 are connected by a straight line extending in the Y direction from the straight line of the connection point 18 of the diaphragm 11.
[0026] The first layer 31 and the second layer 32 may be, for example, insulating layers. The first layer 31 and the second layer 32 may contain, for example, SiO2, or may be formed from, for example, a BOX layer in an SOI substrate. Alternatively, the first layer 31 and the second layer 32 may contain an insulator such as silicon nitride Si3N4 or aluminum oxide Al2O3, or they may contain silicon Si.
[0027] Here, as shown by the dashed lines in Figure 1B, the first layer 31 and the second layer 32 have been trimmed in portions less than or equal to a distance D1 from the connection point 18 and the gap 17. The purpose and effect of this trimming will be explained later with reference to Figures 4 to 6.
[0028] In Figure 2, a gap 41 is provided on the bottom side of the diaphragm 11, facing in the opposite direction to the first main surface 11a. In Figure 1B, when the piezoelectric actuator 1 is viewed from the bottom, the diaphragm 11 is visible through the gap 41.
[0029] Figure 3 is a cross-sectional view of the piezoelectric actuator 1 according to the first embodiment, along line III-III in Figure 1. The same reference numerals are used for parts identical to those in Figure 2, and their descriptions are omitted.
[0030] As previously mentioned with reference to Figure 1A, in Figure 3, the width of the diaphragm 11 in the Y direction is W, and peripheral members 22 are arranged on both the positive and negative sides in the Y direction relative to the diaphragm 11, with gaps 17 in between. The 9th main surface 32a of the second layer 32 is connected to the 8th main surface 22b, which is the bottom surface of the peripheral member 22, and the 11th main surface 43a of the third support part 43 is connected to the 10th main surface 32b of the second layer 32. The third support part 43 supports the peripheral member 22 via the second layer 32. A gap 41 is provided on the bottom side of the diaphragm 11, facing in the opposite direction from the first main surface 11a.
[0031] Next, the operation of the piezoelectric actuator 1 according to the first embodiment, which has the structure and shape described above, will be explained.
[0032] When a voltage is applied between the wiring electrodes 15 and 16 shown in Figures 1A and 2, the respective voltages are transmitted to the lower electrode 12 and the upper electrode 14, and a voltage is applied between the upper and lower surfaces of the piezoelectric film 13. The piezoelectric film 13 expands and contracts due to the inverse piezoelectric effect, and by applying tensile or compressive stress to the diaphragm 11 on which the piezoelectric film 13 is placed, the diaphragm 11 warps, causing displacement in the Z direction at the free end 19 of the diaphragm 11. At this time, stress is applied to each part of the diaphragm 11, and a relatively large stress is applied to the connection point 18 with the first support part 21, which is the fulcrum of the diaphragm 11.
[0033] Figure 4 shows the stress in the piezoelectric actuator 1 when a voltage is applied to the piezoelectric film 13 of the piezoelectric actuator 1 according to the first embodiment. The stress shown in the plan view of Figure 4 was calculated by simulation using the finite element method, with Si set as the material for the diaphragm 11, the first support part 21, and the peripheral member 22.
[0034] As shown in the cross-sectional view of Figure 4, the piezoelectric film 13 contracts in the direction of the arrow, causing stress on the diaphragm 11 that causes it to bend downwards. The plan view of Figure 4 shows the stress intensity on each part of the piezoelectric actuator 1 in 10 stages, in the state shown in the cross-sectional view of Figure 4. The stress on the diaphragm 11 and the first support part 21 is weak at the free end 19 and strongest at the connection point 18.
[0035] As described above with reference to Figure 1B, in the piezoelectric actuator 1 according to the first embodiment, the portion of the first layer 31 that is less than or equal to a distance D1 from the connection point 18 and the gap 17 is removed. In other words, when viewed from the direction normal to the second main surface 21a, the outer edge of the fourth main surface 31a of the first layer 31 that is closer to the connection point 18 is located on the side of the first support portion 21 rather than the connection point 18.
[0036] In the plan view of Figure 4, by shifting the outer edge of the fourth main surface 31a of the first layer 31 toward the first support portion 21 relative to the connection point 18, the stress acting from the fourth main surface 31a of the first layer 31 toward the connection point 18 is reduced. In other words, a portion of the stress on the connection point 18 is distributed to the portion of the fourth main surface 31a of the first layer 31 that has been removed. As a result, in the piezoelectric actuator 1 according to the first embodiment, the stress on the connection point 18 between the diaphragm 11 and the first support portion 21 can be alleviated.
[0037] Here, in order to make it easier to understand the features of the embodiments of the present invention, a comparative piezoelectric actuator will be described. Figure 5 is a diagram showing the stress in the piezoelectric actuator 91 when a voltage is applied to the comparative piezoelectric actuator 91. The comparative piezoelectric actuator 91 differs from the piezoelectric actuator 1 according to the first embodiment in that, when viewed from the direction normal to the second main surface 21a, the outer edge of the fourth main surface 31a of the first layer 31 that is close to the connection point 18 is located at the same position as the connection point 18. The other configurations are the same as those of the piezoelectric actuator 1 according to the first embodiment, so a detailed explanation will be omitted.
[0038] The stresses shown in the plan view of Figure 5 were calculated using a finite element method simulation, similar to the plan view in Figure 4. The plan view of Figure 5 shows the stress intensity on each part of the piezoelectric actuator 91 in 10 stages, in the state of the cross-sectional view of Figure 5. The stress on the diaphragm 11 and the first support part 21 is particularly strong near the connection point 18.
[0039] Compared with the plan view showing the stress of the comparative example shown in Figure 5, the stress on the connection point 18 is reduced in the plan view showing the stress of the piezoelectric actuator 1 according to the first embodiment shown in Figure 4. As mentioned above, this stress reduction effect is obtained in the piezoelectric actuator 1 shown in Figure 4 by positioning the outer edge of the fourth main surface 31a of the first layer 31 that is closer to the connection point 18, when viewed from the direction normal to the second main surface 21a, on the side of the first support portion 21 rather than the connection point 18.
[0040] Figure 6 shows the relationship between the position of the outer edge of the fourth main surface 31a of the first layer 31 and the stress in the piezoelectric actuator 1 according to the first embodiment. The stresses shown in the graph of Figure 6 were calculated by simulation using the finite element method, similar to Figures 4 and 5. The length L of the diaphragm 11 is set to L = 1000 μm as an example.
[0041] The graph in Figure 6 plots the maximum stress when the outer edge of the fourth main surface 31a of the first layer 31, which is closest to the connection point 18, is shifted by xum in the opposite direction to the free end 19, relative to the connection point 18. The horizontal axis of the graph in Figure 6 shows the position of the outer edge of the fourth main surface 31a on the side of the connection point 18, with the position of the connection point 18 set to x=0 and the position when shifted by xum in the opposite direction to the free end 19 of the diaphragm 11 shown as -xum. The vertical axis of the graph in Figure 6 shows the maximum stress normalized by the maximum stress at x=0.
[0042] As shown in the graph in Figure 6, shifting the position of the outer edge of the fourth main surface 31a of the first layer 31 within the range of x=0 to x=-100um reduces the maximum stress. The stress reduction effect is maximized at approximately x=-100um, and the stress reduction effect saturates even when the position of the outer edge of the fourth main surface 31a is shifted further. This can be viewed as the ratio of the amount the outer edge of the fourth main surface 31a is shifted to the length L of the diaphragm 11. By shifting the position of the outer edge of the fourth main surface 31a of the first layer 31 that is close to the connection point 18 in the opposite direction to the free end 19 by a ratio of greater than 0% and less than or equal to 10% of the length L of the diaphragm 11, the stress on the connection point 18 can be effectively reduced.
[0043] The stress reduction effect of the piezoelectric actuator 1 described above can be obtained even when the first layer 31 is formed from a material other than SiO2. For example, the first layer 31 may be made of Si.
[0044] The piezoelectric actuator 1 described above may be applied, for example, to the head, speaker, and ultrasonic element of an inkjet printer.
[0045] (Manufacturing method for piezoelectric actuators) Next, a method for manufacturing the piezoelectric actuator 1 according to the first embodiment will be described. Figures 7A to 7F show the manufacturing process of the piezoelectric actuator 1 according to the first embodiment.
[0046] First, as shown in Figure 7A, an SOI wafer 50 is prepared having a Si active layer 51 which will become the diaphragm 11, the first support portion 21 and peripheral member 22, a BOX layer 52 which will become the first layer 31 and the second layer 32, and a Si support substrate 53 which will become the second support portion 42 and the third support portion 43. Then, an insulating film 20, a lower electrode 12, a piezoelectric film 13 and an upper electrode 14 are laminated on the top surface of the SOI wafer 50, that is, the top surface of the Si active layer 51.
[0047] Next, as shown in Figure 7B, the lower electrode 12, the piezoelectric film 13, and the upper electrode 14 are processed so that they are formed in an appropriate shape on the upper surfaces of the diaphragm 11 and the first support portion 21 of the piezoelectric actuator 1, respectively. Then, an insulating film 20 is formed as a protective film to cover the processed lower electrode 12, piezoelectric film 13, and upper electrode 14.
[0048] Next, as shown in Figure 7C, a portion of the insulating film 20 located on the upper surface of the upper electrode 14 is opened to form a contact between the upper electrode 14 and the wiring electrode 16 and the wiring electrode 16. Similarly, a portion of the insulating film 20 located on the upper surface of the lower electrode 12 is opened to form a contact between the lower electrode 12 and the wiring electrode 15 and the wiring electrode 15. Then, in the insulating film 20, the Si active layer 51, and the BOX layer 52, a first opening 23 is formed at the location of the void 17, and a second opening 24 is formed along the scribe line that will be the cutting allowance when the chip is pieced. The first opening 23 and the second opening 24 separate the Si active layer 51 into the diaphragm 11 and the first support portion 21 and the peripheral member 22, and separate the BOX layer 52 into the first layer 31 and the second layer 32.
[0049] Next, as shown in Figure 7D, the bottom surface of the Si support substrate 53 is ground down to reduce its thickness as needed. Then, the portion of the Si support substrate 53 located on the side of the bottom surface facing away from the first main surface 11a of the diaphragm 11 is removed by processing to form a gap 41. With the gap 41 provided in the Si support substrate 53 at the position of the first opening 23, the first opening 23 becomes a through-hole gap 17.
[0050] Next, as shown in Figure 7E, the first layer 31 and the second layer 32 formed by separating the BOX layer 52 are processed. The first layer 31 and the second layer 32, which are SiO2 films, are etched by performing wet etching or dry etching with a selectivity ratio for Si through the gap 41 from the side where the Si support substrate 53 is placed. The etching removes the first layer 31 connected to the bottom surface facing the opposite direction from the first main surface 11a of the diaphragm 11, and also removes the side surface connecting the fourth main surface 31a and the fifth main surface 31b of the first layer 31 sandwiched between the first support part 21 and the Si support substrate 53. Simultaneously, the etching removes the side surface in contact with the gap 41 among the side surfaces connecting the ninth main surface 32a and the tenth main surface 32b of the second layer 32 sandwiched between the peripheral member 22 and the Si support substrate 53.
[0051] After etching, the outer edge of the first layer 31 closest to the connection point 18 is located on the side of the first support part 21 rather than the connection point 18, when viewed from the direction normal to the second main surface 21a of the first support part 21. Similarly, after etching, the outer edge of the second layer 32 closest to the void 17 is located on the side of the peripheral member 22 rather than the void 17, when viewed from the direction normal to the seventh main surface 22a of the peripheral member 22. The detailed shapes of the first layer 31 and the second layer 32 after etching will be described later with reference to Figures 8A to 8C.
[0052] Next, as shown in Figure 7F, the chip is divided into individual pieces by dicing along the scribe line located at the second aperture 24. Either blade dicing or laser dicing may be used as the dicing method. Furthermore, when using blade dicing, the blade width may be wider or narrower than the width of the second aperture 24. Figure 7F shows, as an example, a case where blade dicing is used with a blade width wider than the width of the second aperture 24. Through dicing, the Si support substrate 53 is separated into a second support portion 42 and a third support portion 43.
[0053] In the piezoelectric actuator 1 according to the first embodiment, as shown in Figure 7F, the first support portion 21, peripheral member 22, first layer 31, second layer 32, and Si support substrate 53 are cut with a width wider than the second opening 24 during dicing. Therefore, when the cutting area by dicing is viewed from the direction normal to the second main surface 21a, the positions of the outer edges of the first support portion 21, first layer 31, and second support portion 42 are aligned. Also, when the cutting area by dicing is viewed from the direction normal to the seventh main surface 22a, the positions of the outer edges of the peripheral member 22, second layer 32, and third support portion 43 are aligned. However, as will be described later with reference to Figure 11C, if blade dicing, in which the blade width is narrower than the width of the second opening 24, or laser dicing is used as the dicing method, the positions of the outer edges of the first support portion 21 and the second support portion 42, and the positions of the outer edges of the peripheral member 22 and the third support portion 43 do not need to be aligned.
[0054] Figures 8A to 8C illustrate in detail the cross-sectional shapes of the first layer 31 and the second layer 32, which are produced by the processing of the first layer 31 and the second layer 32 shown in Figure 7E. Figures 8A to 8C show examples of the cross-sectional shapes of the first layer 31 and the second layer 32 obtained by etching the SiO2 film by wet etching or dry etching with a selectivity ratio for Si.
[0055] In Figure 8A, the side surface connecting the fourth main surface 31a and the fifth main surface 31b, the side surface closest to the connection point 18, is etched over a substantially equal distance in a direction perpendicular to the side surface, thereby becoming a plane substantially perpendicular to the fourth main surface 31a and the fifth main surface 31b. Figure 8A is a shape created by etching, for example, mainly anisotropic etching.
[0056] In Figure 8B, the side surface connecting the fourth main surface 31a and the fifth main surface 31b, the side surface closest to the connection point 18, is a curved surface that includes a cylindrical side surface that is substantially equal in distance from the outer edge of the sixth main surface 42a of the second support part 42 that is closest to the connection point 18. When the cross-sectional shape shown in Figure 8B is viewed from the direction normal to the second main surface of the first support part 21, the outer edge of the fifth main surface 31b is further from the connection point 18 than the outer edge of the fourth main surface 31a. Figure 8B is a shape created by etching, for example, mainly isotropic etching.
[0057] In Figure 8C, the side surface connecting the fourth main surface 31a and the fifth main surface 31b that is closest to the connection point 18 is a plane that intersects at an angle with the normal directions of the fourth main surface 31a and the fifth main surface 31b. When the cross-sectional shape shown in Figure 8C is viewed from the normal direction of the second main surface 21a of the first support part 21, the outer edge of the fifth main surface 31b is further from the connection point 18 than the outer edge of the fourth main surface 31a.
[0058] The shapes shown in Figures 8A to 8C are examples of the cross-sectional shapes of the first layer 31 and the second layer 32 after etching, and the shapes after etching may be other than those shown in Figures 8A to 8C.
[0059] As mentioned above, even if the first layer 31 in the piezoelectric actuator 1 is formed from a material other than SiO2, such as Si, a similar stress reduction effect can be obtained in a structure having a similar structure. However, if the diaphragm 11, the first support part 21, and the second support part 42 are made of Si, and the first layer 31 is also made of Si, it tends to be difficult to control the etching process of the first layer 31. Compared to making the first layer 31 out of Si, by making the first layer 31 out of the BOX layer 52 of the SOI wafer 50 and etching the first layer 31 by etching with a selectivity ratio with Si, it is possible to easily control the processing of the first layer 31.
[0060] (Effects of the first embodiment) According to the piezoelectric actuator 1, the stress on the connection point 18 between the diaphragm 11 and the first support part 21 can be relieved by shifting the outer edge of the fourth main surface 31a of the first layer 31 that is closest to the connection point 18 toward the first support part 21. According to the piezoelectric actuator 1, the stress on the connection point 18 can be effectively reduced by shifting the position of the outer edge of the fourth main surface 31a of the first layer 31 that is closest to the connection point 18 from the connection point 18 by a ratio greater than 0% and less than or equal to 10% of the length L of the diaphragm 11.
[0061] The piezoelectric actuator 1 can alleviate the stress on the connection point 18, thereby improving the reliability of the elements constituting the piezoelectric actuator 1 when using the same voltage. Alternatively, the piezoelectric actuator 1 can displace the diaphragm 11 more significantly by increasing the applied voltage within the margin of stress relative to the standard obtained by reducing the stress.
[0062] Furthermore, with the piezoelectric actuator 1, the first layer 31 is composed of the BOX layer 52 of the SOI wafer 50, and the first layer 31 is etched by etching with a selectivity ratio for Si, thereby making it easier to control the processing of the first layer 31.
[0063] [Second Embodiment] (Configuration of a piezoelectric actuator) Figure 9 is a plan view of the piezoelectric actuator 2 according to the second embodiment. Figure 10 is a cross-sectional view of the piezoelectric actuator 2 of Figure 9 along XX. The same parts as in Figures 1A to 1C and Figure 2 are denoted by the same reference numerals and their descriptions are omitted.
[0064] The piezoelectric actuator 2 according to the second embodiment shown in Figures 9 and 10 differs from the piezoelectric actuator 1 according to the first embodiment shown in Figures 1A to 1C and 2 in the following respects. The outer edge of the first layer 31 in Figures 9 and 10, near the outer edge of the piezoelectric actuator 2, has portions removed from the three edges that do not overlap with the straight line extending the line segment of the connection point 18 among the edges forming the outer edge of the first support portion 21, when viewed from the direction normal to the second main surface 21a, insofar as they are at a distance D1 or less. In other words, when viewed from the direction normal to the second main surface 21a, the outer edge of the fourth main surface 31a that is farther from the connection point 18 is located inward than the outer edge of the second main surface 21a that is farther from the connection point 18.
[0065] Furthermore, in Figures 9 and 10, the outer edge of the second layer 32 near the outer edge of the piezoelectric actuator 2 has portions that are less than or equal to a distance D1 from the three edges of the peripheral member 22, excluding the edge connected to the first support portion 21, when viewed from the direction normal to the seventh main surface 22a. In other words, when viewed from the direction normal to the seventh main surface 22a, at least a portion of the outer edge of the ninth main surface 32a that is close to the air gap 17 is located further from the diaphragm 11 than the air gap 17.
[0066] Furthermore, in Figure 9, when viewed from the top surface of the piezoelectric actuator 2, the outer edges of the second support portion 42 and the third support portion 43 are located outward from the edges forming the outer edges of the first support portion 21 and the peripheral member 22, excluding the edge where the first support portion 21 and the peripheral member 22 are connected. Therefore, when viewed from the top surface of the piezoelectric actuator 2, a portion of the sixth main surface 42a of the second support portion 42 and a portion of the eleventh main surface 43a of the third support portion 43 are visible.
[0067] The reason why, in the vicinity of the outer edge of the piezoelectric actuator 2 according to the second embodiment, the outer edges of the first layer 31 and the second layer 32 are shaved relative to the outer edges of the first support portion 21 and the peripheral member 22, and the outer edges of the second support portion 42 and the third support portion 43 are located outward, will be explained later with reference to Figures 11A to 11C. Here, it is not limited to the occurrence of both the shaving of the outer edges of the first layer 31 and the second layer 32 and the outward positioning of the outer edges of the second support portion 42 and the third support portion 43 occurring simultaneously, but either one may occur.
[0068] (Manufacturing method for piezoelectric actuators) Next, a method for manufacturing the piezoelectric actuator 2 according to the second embodiment will be described. Figures 11A to 11C show the manufacturing process of the piezoelectric actuator 2 according to the second embodiment.
[0069] Figure 11A is a cross-sectional view after the process from preparing the SOI wafer 50 to processing the bottom surface of the Si support substrate 53. Figure 11A corresponds to the cross-sectional view after the process shown in Figure 7D in the manufacturing process of the piezoelectric actuator 1 according to the first embodiment. The process prior to Figure 11A is the same as the manufacturing process of the piezoelectric actuator 1 described with reference to Figures 7A to 7C, so its description is omitted. In Figure 11A, the width of the second opening 24 may be relatively wider compared to the cross-sectional view of the piezoelectric actuator 1 shown in Figure 7D.
[0070] Next, as shown in Figure 11B, the first layer 31 and the second layer 32 formed by separating the BOX layer 52 are processed. In the piezoelectric actuator 2 according to the second embodiment, the first layer 31 and the second layer 32, which are SiO2 films, are etched through the gaps 17, 41 and the second opening 24 by wet etching or dry etching having a selectivity ratio with Si. The etching removes the first layer 31 connected to the bottom surface facing the opposite direction from the first main surface 11a of the diaphragm 11, and also removes the side surface connecting the fourth main surface 31a and the fifth main surface 31b of the first layer 31, and the side surface connecting the ninth main surface 32a and the tenth main surface 32b of the second layer 32.
[0071] Next, as shown in Figure 11C, dicing is performed along the scribe line at the position of the second aperture 24 to separate the chip into individual pieces. Blade dicing or laser dicing may be used as the dicing method. Furthermore, when using blade dicing, the blade width may be wider or narrower than the width of the second aperture 24. Figure 11C shows, as an example, the case where blade dicing with a blade width narrower than the width of the second aperture 24, or laser dicing, is used. Through dicing, the Si support substrate 53 is separated into the second support portion 42 and the third support portion 43. In the piezoelectric actuator 2, during dicing, the first support portion 21 and the first layer 31, and the peripheral members 22 and the second layer 32 are not cut, and the Si support substrate 53 is cut with a width narrower than the second aperture 24.
[0072] When the cutting point is viewed from the direction normal to the second main surface 21a, the positions of the outer edges of the first support portion 21 and the first layer 31 do not change due to dicing, and the outer edges of the first support portion 21, the first layer 31, and the second support portion 42 do not overlap at the cutting point. Of the outer edges of the first layer 31, the edges other than the edge connecting to the second layer 32 are located inward relative to the outer edge of the first support portion 21. Also, of the outer edges of the second support portion 42, the edges other than the edge connecting to the third support portion 43 are located outward relative to the outer edge of the first support portion 21.
[0073] Furthermore, when the cutting point is viewed from the direction normal to the seventh main surface 22a, the positions of the outer edges of the peripheral member 22 and the second layer 32 do not change due to dicing, and the outer edges of the peripheral member 22, the second layer 32 and the third support part 43 do not overlap at the cutting point. Of the outer edges of the second layer 32, the edges other than the edge connecting to the first layer 31 are located inward relative to the outer edge of the peripheral member 22. Also, of the outer edges of the third support part 43, the edges other than the edge connecting to the second support part 42 are located outward relative to the outer edge of the peripheral member 22. As explained above, if blade dicing with a blade width narrower than the width of the second opening 24 or laser dicing is used as the dicing method, the positions of the outer edges of the first support part 21 and the second support part 42, and the positions of the outer edges of the peripheral member 22 and the third support part 43 do not need to be aligned.
[0074] In the piezoelectric actuator 2 according to the second embodiment, the stress on the connection point 18 between the diaphragm 11 and the first support portion 21 can be relieved, similar to the piezoelectric actuator 1 according to the first embodiment. Furthermore, in the piezoelectric actuator 2, the first support portion 21 and the first layer 31, and the peripheral member 22 and the second layer 32 are not cut during dicing, thus reducing the impact of dicing on these members.
[0075] (Effects of the second embodiment) With the piezoelectric actuator 2, the stress on the connection point 18 between the diaphragm 11 and the first support part 21 can be relieved by shifting the outer edge of the fourth main surface 31a of the first layer 31 that is closest to the connection point 18 toward the first support part 21. Furthermore, with the piezoelectric actuator 2, the first support part 21 and the first layer 31, and the peripheral members 22 and the second layer 32 are not cut during dicing, thus reducing the impact of dicing on these members.
[0076] [Third Embodiment] (Configuration of a piezoelectric actuator) Figure 12 is a cross-sectional view of the piezoelectric actuator 3 according to the third embodiment. The plan view of the piezoelectric actuator 3 is the same as the plan view of the piezoelectric actuator 2 according to the second embodiment shown in Figure 9, so its description is omitted. Figure 12 is a cross-sectional view of the piezoelectric actuator 3 according to the third embodiment, taken along the same cutting line as XX of the piezoelectric actuator 2 in Figure 9. The same reference numerals are used for parts that are the same as those in Figures 9 and 10, and their descriptions are omitted.
[0077] The piezoelectric actuator 3 shown in Figure 12 differs from the piezoelectric actuator 2 according to the second embodiment shown in Figure 10 in that it further comprises a flat plate 44. The flat plate 44 has a 13th main surface 44a connected to a 12th main surface 42b that faces in the opposite direction to the 6th main surface 42a of the second support portion 42. In Figure 12, an example is shown where a part of the outer edge of the 13th main surface 44a overlaps with the free end 19 when viewed from the direction normal to the 1st main surface 11a of the diaphragm 11, but the outer edge of the 13th main surface 44a may enclose the free end 19. Alternatively, the flat plate 44 may be connected to the 3rd support portion 43 to cover the gap 41.
[0078] The support portion may be reinforced by applying a piezoelectric actuator 3, for example, by connecting the second support portion 42 and the third support portion 43 with a flat plate 44.
[0079] Alternatively, for example, a piezoelectric actuator 3 may be applied to configure a device in which the gap 41 is covered by a flat plate 44 except for a portion of the area, and the gas or liquid filled in the gap 41 is ejected from the area not covered by the flat plate 44 by the deformation of the diaphragm 11. For example, the piezoelectric actuator 3 may be applied to the head of an inkjet printer as follows: Specifically, the gap 41 is covered by a flat plate 44 except for the ink ejection holes, and the gap 41 is filled with ink. When a voltage is applied to the piezoelectric film 13, the diaphragm 11 deforms, pushing out the ink and ejecting it from the ejection holes. When no voltage is applied to the piezoelectric film 13, the ejection of ink is stopped by the surface tension acting on the ink surface of the ejection holes.
[0080] (Effects of the third embodiment) The piezoelectric actuator 3 can relieve the stress on the connection point 18 between the diaphragm 11 and the first support part 21. Furthermore, the piezoelectric actuator 3 can strengthen the support part by connecting the second support part 42 and the third support part 43 using a flat plate 44. In addition, the piezoelectric actuator 3 can be configured to cover the void 41 with the flat plate 44 except for a certain area, and to discharge the gas or liquid filled in the void 41 from the area not covered by the flat plate 44.
[0081] [Other embodiments] While several embodiments of this disclosure have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. One or more elements of one embodiment may be combined with one or more elements of another embodiment. These novel embodiments can be implemented in a variety of other forms, and various omissions, substitutions, and modifications are permitted without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention and in the scope of the invention and its equivalents as described in the claims.
[0082] For example, the piezoelectric actuators according to the first to third embodiments of this disclosure show an example having a structure called a cantilever, in which the diaphragm 11 is connected to a first support 21 via a connection point 18 and has a free end 19 at a position opposite to the connection point 18. However, the piezoelectric actuator may also have a structure called a double-supported beam, and in that case as well, it is possible to provide a piezoelectric actuator that has a structure that can relieve the stress on the connection point between the diaphragm and the support.
[0083] Furthermore, in the piezoelectric actuator according to the first to third embodiments of this disclosure, the shape of the diaphragm 11 is shown to be a rectangle having length L and width W. However, the shape of the diaphragm 11 is not limited to this, and may be a circle, for example.
[0084] Furthermore, in the piezoelectric actuators according to the first to third embodiments of this disclosure, examples have been given in which the piezoelectric film 13 includes, for example, lead zirconate titanate (PZT) or aluminum nitride (AlN). However, the piezoelectric film 13 may also include, for example, zinc oxide (ZnO), lithium niobate (LiNbO3), or lithium tantalate (LiTaO3).
[0085] Furthermore, the piezoelectric actuators according to the first to third embodiments of this disclosure are not limited to inkjet printer heads, speakers, and ultrasonic elements, but may also be applied to, for example, micromirrors.
[0086] (Note) The technical concepts that can be grasped from this disclosure are described below. Note that, not as an attempt to limit the scope but to aid understanding, the components described in the appendices are denoted by the corresponding reference numerals of the components in the embodiments. The reference numerals are provided as examples to aid understanding, and the components described in each appendice should not be limited to those indicated by the reference numerals.
[0087] (Note 1) The piezoelectric actuators 1 to 3 each include a diaphragm 11, a first support portion 21, a thin film including a piezoelectric film 13, a first layer 31, and a second support portion 42. The diaphragm 11 has a first main surface 11a. The first support portion 21 has a second main surface 21a facing the same direction as the first main surface 11a and is connected to the diaphragm 11 via a connection point 18. The thin film including the piezoelectric film 13 is arranged on the first main surface 11a. The first layer 31 has a fourth main surface 31a connected to a third main surface 21b of the first support portion 21 which faces the opposite direction to the second main surface 21a. The second support portion 42 has a sixth main surface 42a connected to a fifth main surface 31b of the first layer 31 which faces the opposite direction to the fourth main surface 31a, and supports the first support portion 21 via the first layer 31. The diaphragm 11 has a free end 19 at a position opposite to the connection point 18. Viewed from the direction normal to the second main surface 21a, the outer edge of the fourth main surface 31a that is closer to the connection point 18 is located on the side of the first support portion 21 rather than the connection point 18.
[0088] The piezoelectric actuators 1 to 3 can relieve the stress on the connection point 18 between the diaphragm 11 and the first support part 21.
[0089] (Note 2) In the piezoelectric actuators 1 to 3 described in Appendix 1, the distance between the outer edge of the fourth main surface 31a closest to the connection point 18 and the connection point 18, when viewed from the direction normal to the second main surface 21a, is greater than 0 and less than or equal to one-tenth of the distance between the free end 19 and the connection point 18. The piezoelectric actuators 1 to 3 can effectively reduce the stress on the connection point 18.
[0090] (Note 3) In the piezoelectric actuator 2 described in Appendix 1 or 2, when viewed from the direction normal to the second main surface 21a, the outer edge of the fourth main surface 31a that is furthest from the connection point 18 is located inward from the outer edge of the second main surface 21a that is furthest from the connection point 18.
[0091] (Note 4) The piezoelectric actuators 1 and 2 described in any one of the appendices 1 to 3 further comprise a peripheral member 22, a second layer 32, and a third support portion 43. The peripheral member 22 has a seventh main surface 22a facing the same direction as the first main surface 11a and is arranged around the diaphragm 11 with a gap 17, excluding the connection point 18. The second layer 32 has a ninth main surface 32a connected to the eighth main surface 22b of the peripheral member 22, which faces the opposite direction to the seventh main surface 22a. The third support portion 43 has an eleventh main surface 43a connected to the tenth main surface 32b of the second layer, which faces the opposite direction to the ninth main surface 32a. Viewed from the normal direction of the seventh main surface 22a, at least a portion of the outer edge of the ninth main surface 32a that is closer to the gap 17 is located further from the diaphragm 11 than the gap 17.
[0092] (Note 5) In the piezoelectric actuator 1 described in any one of the appendices 1 to 4, the thin film has a laminated structure of electrodes 12 and 14 and a piezoelectric film 13.
[0093] (Note 6) The piezoelectric actuator 3 described in any one of appendices 1 to 5 further comprises a flat plate 44. The flat plate 44 has a 13th main surface 44a connected to the 12th main surface 42b of the second support portion 42, which faces in the opposite direction to the 6th main surface 42a. Viewed from the direction normal to the 1st main surface 11a, the outer edge of the 13th main surface 44a encloses the free end 19.
[0094] (Note 7) In the piezoelectric actuator 1 described in any one of the appendices 1 to 6, the first layer 31 is an insulating layer.
[0095] (Note 8) In the piezoelectric actuator 1 described in any one of the appendices 1 to 7, the diaphragm 11 and the first support portion 21 contain silicon Si.
[0096] (Note 9) In the piezoelectric actuator 1 described in any one of the appendices 1 to 8, the second support portion 42 contains silicon Si.
[0097] (Note 10) In the piezoelectric actuator 1 described in any one of the appendices 1 to 9, the first layer 31 is made of the insulating layer of the BOX layer of the SOI substrate, and the diaphragm 11, the first support part 21, and the second support part 42 are made of silicon Si sandwiching the BOX layer. With the piezoelectric actuator 1, by making the first layer 31 of the BOX layer of the SOI substrate and etching the first layer 31 using the etching selectivity ratio, it is possible to easily control the processing of the first layer 31.
[0098] (Note 11) The method for manufacturing the piezoelectric actuator 1 described in Appendix 10 involves etching the side surface of the first layer 31 that connects the fourth main surface 31a and the fifth main surface 31b, the side surface closest to the connection point 18, using etching with a selectivity ratio relative to the diaphragm 11, the first support part 21, and the second support part 42. In the manufacturing method, the position of the outer edge of the fourth main surface 31a that is closest to the connection point 18, when viewed from the normal direction of the second main surface 21a, is set to be on the side of the first support part 21 rather than the connection point 18. According to the method for manufacturing the piezoelectric actuator 1, the stress on the connection point 18 between the diaphragm 11 and the first support part 21 can be relieved. According to the method for manufacturing the piezoelectric actuator 1, the first layer 31 is composed of a BOX layer of an SOI substrate, and by etching the first layer 31 using the selectivity ratio of etching, the processing of the first layer 31 can be easily controlled. [Explanation of Symbols]
[0099] 1, 2, 3 Piezoelectric actuators 11 Diaphragm 11a 1st main surface 12 Lower electrode 13 Piezoelectric film 14 Upper electrode 15, 16 Wiring electrode 17, 41 void 18 connection points 19 Free end 20 Insulating film 21 1st support part 21a 2nd principal surface 21b 3rd principal surface 22 Peripheral components 22a 7th main surface 22b 8th principal surface 31 1st layer 31a 4th principal surface 31b 5th principal surface 32 2nd layer 32a Ninth main surface 32b 10th principal surface 42 Second support part 42a Sixth main surface 42b 12th Main Surface 43 Third support part 43a Eleventh main surface 44 Flat plate 44a 13th Main Surface 50 SOI wafers 51 Si active layer 52 BOX layer 53 Si support substrate
Claims
1. A diaphragm having a first main surface, A first support portion having a second main surface facing the same direction as the first main surface and connected to the diaphragm via a connection point, A thin film including a piezoelectric film is disposed on the first main surface, A first layer having a fourth main surface connected to the third main surface of the first support portion which faces in the opposite direction to the second main surface, A second support portion has a sixth main surface connected to the fifth main surface of the first layer which faces in the opposite direction to the fourth main surface, and supports the first support portion via the first layer, Equipped with, The diaphragm has a free end at a position opposite to the connection point, Viewed from the direction normal to the second main surface, the outer edge of the fourth main surface that is closest to the connection point is located closer to the first support than to the connection point. Piezoelectric actuator.
2. When viewed from the direction normal to the second principal surface, the distance between the outer edge of the fourth principal surface closest to the connection point and the connection point is greater than 0 and less than or equal to one-tenth of the distance between the free end and the connection point. The piezoelectric actuator according to claim 1.
3. Viewed from the direction normal to the second principal surface, the outer edge of the fourth principal surface that is furthest from the connection point is located inward from the outer edge of the second principal surface that is furthest from the connection point. The piezoelectric actuator according to claim 1.
4. A peripheral member having a seventh main surface facing the same direction as the first main surface, and arranged around the diaphragm with a gap between it and the connection point, A second layer having a ninth main surface connected to the eighth main surface of the peripheral member which faces in the opposite direction to the seventh main surface, A third support portion having an eleventh main surface connected to the tenth main surface of the second layer which faces in the opposite direction to the ninth main surface, and supporting the peripheral member via the second layer, Furthermore, Viewed from the normal direction of the seventh main surface, at least a portion of the outer edge of the ninth main surface that is close to the void is located at a position further from the diaphragm than the void. The piezoelectric actuator according to claim 1.
5. The piezoelectric actuator according to claim 1, wherein the thin film has a laminated structure of an electrode and a piezoelectric film.
6. The present invention further comprises a flat plate having a 13th main surface connected to the 12th main surface of the second support portion, which faces in the opposite direction to the 6th main surface, Viewed from the direction normal to the first principal surface, the outer edge of the thirteenth principal surface encloses the free end. The piezoelectric actuator according to claim 1.
7. The piezoelectric actuator according to any one of claims 1 to 6, wherein the first layer is an insulating layer.
8. The piezoelectric actuator according to any one of claims 1 to 6, wherein the diaphragm and the first support portion include silicon.
9. The piezoelectric actuator according to any one of claims 1 to 6, wherein the second support portion contains silicon.
10. The piezoelectric actuator according to claim 7, wherein the first layer is composed of an insulating layer of the BOX layer of an SOI wafer, and the diaphragm, the first support portion, and the second support portion are composed of silicon sandwiching the BOX layer.
11. A method for manufacturing a piezoelectric actuator according to claim 10, The side surface of the first layer connecting the fourth main surface and the fifth main surface, the side surface closest to the connection point, is etched using etching with a selectivity ratio relative to the diaphragm, the first support part, and the second support part, and the position of the outer edge of the fourth main surface closest to the connection point, as viewed from the direction normal to the second main surface, is set to be closer to the first support part than to the connection point. A method for manufacturing a piezoelectric actuator.