JP2012151583A - Piezoelectric type actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric type actuator capable of providing a large output with a small mounting area.SOLUTION: The piezoelectric type actuator includes a plurality of first flexible parts arrayed in a first direction parallel to each other, a second flexible part which, with two first flexible parts coupled as a pair, connects one end parts in thickness direction of the first flexible parts for each pair, a third flexible part which, with two first flexible parts that adjoin each other but belong to a different pair, among the pairs of the first flexible parts connected by the second flexible part, as a pair, connects the other end parts together in thickness direction of the first flexible parts for each pair, a piezoelectric element in a piezoelectric layer made of two electrode layers and an inorganic piezoelectric material sandwiched with the piezoelectric layers, formed on the surface parallel to the main surface of one substrate of the third flexible part and the second flexible part, and a frame part, in square frame shape, combined to both ends of the first flexible part, both ends of the second flexible part, and both end of the third flexible part, in the thickness direction and a second direction orthogonal to the first direction, on a pair of inner wall surfaces, facing each other.

Description

  The present invention relates to a piezoelectric actuator.

  Patent Document 1 has a corrugated vibrating membrane composed of stretchable portions alternately provided so as to be front and rear with respect to the sound radiation direction and rising portions that connect end portions of adjacent stretchable portions. A piezoelectric membrane speaker in which electrodes are formed on both sides is described. Patent Document 2 describes a speaker using a piezoelectric film that is sandwiched between electrodes on the front and back surfaces and shaped so that the cross section has a corrugated shape.

JP 2005-286690 A JP 2004-282187 A

In Patent Documents 1 and 2, a polymer resin piezoelectric material such as polyvinylidene fluoride (PVDF) is used for the diaphragm, and there is a problem that a large sound pressure cannot be obtained as compared with an inorganic piezoelectric material. Further, in Patent Document 2, since each intermediate portion of the waveform shape is held by a holding body for preventing the vibration of the portion, the amount of displacement becomes small and a large sound pressure cannot be obtained. In the piezoelectric film speaker of Patent Document 1, since a single piezoelectric sheet is formed to create a corrugated shape, stress remains and performance and yield are not stable. Also, miniaturization is difficult.
The present invention has been made in view of the above problems, and an object thereof is to provide a piezoelectric actuator that can obtain a large output with a small mounting area.

  (1) A piezoelectric actuator for achieving the above object is a thin plate-like first flexible portion in a first direction parallel to the main surface of the substrate orthogonal to the thickness direction of the substrate, and is parallel to each other. A plurality of first flexible portions arranged in the first direction and two adjacent first flexible portions as a set, and one set of the first flexible portions in the thickness direction (of the substrate). Two adjacent first belongings belonging to different sets in the combination of the second flexible part that connects one end in the thickness direction) and the first flexible part that the second flexible part connects. A third flexible part that connects the other ends of the first flexible part in the thickness direction (thickness direction of the substrate) one by one with the flexible part as a set, and the second flexible part And at least one of the third flexible portions formed on a plane parallel to the main surface of the substrate, and two electrode layers and the two electrode layers A piezoelectric element having a piezoelectric layer made of an sandwiched inorganic piezoelectric material and a frame portion in the form of a rectangular frame, and a pair of inner wall surfaces facing each other in the thickness direction (thickness direction of the substrate) and the first A frame portion coupled to both end portions of the first flexible portion, both end portions of the second flexible portion, and both end portions of the third flexible portion in a second direction orthogonal to the direction.

  According to the present invention, since the surface in the thickness direction of the substrate can also be used as the diaphragm, the area of the vibration surface can be widened even with a small mounting area. Therefore, it is easy to reduce the size of the piezoelectric actuator. In addition, when applied to a speaker, the sound pressure in the low range can be improved even if it is small. Further, downsizing increases the number of piezoelectric actuators that can be manufactured from one wafer, contributing to cost reduction. In addition, since a piezoelectric layer made of an inorganic piezoelectric material is used, a large output can be obtained as compared with the case of using an organic piezoelectric material.

(2) In the piezoelectric actuator for achieving the above object, the length in the second direction of the surface of the second flexible part or the third flexible part on which the piezoelectric element is formed is the piezoelectric It may be longer than the length of the element in the second direction.
When the length in the second direction of the surface of the second flexible portion or the third flexible portion on which the piezoelectric element is formed is the same as or shorter than the length in the second direction of the piezoelectric element, the first flexible portion contracts or expands. Stress concentrates on the joint portion between the second flexible portion or the third flexible portion and the frame portion, and breaks easily. Therefore, it is difficult to increase the deformation amount of the piezoelectric element. According to the configuration of the present invention, it is possible to prevent the stress from concentrating on the coupling portion, so that the piezoelectric element can be greatly deformed compared to the case described above, and the displacement width of each flexible portion can be increased. it can.

(3) In the piezoelectric actuator for achieving the above object, the first flexible portion is configured such that the silicon layer constituting the substrate is anisotropic from both the main surface side and the other main surface side of the substrate. It may be configured to include a thin plate formed by deep digging by reactive etching.
In this case, since the residual stress of the first flexible portion is small, the performance and yield are stabilized.

(4) In the piezoelectric actuator for achieving the above object, the first flexible portion may be composed of a film of an inorganic compound or an organic compound formed by a vapor deposition polymerization method or a CVD method.
Since a thinner film can be used in the vibration direction (first direction) of the first flexible portion, the displacement width of the first flexible portion can be increased.

(1A) is a top view of the piezoelectric speaker according to the first embodiment, and (1B) and (1C) are sectional views thereof. (2A) is a bottom view of the piezoelectric speaker according to the first embodiment, and (2B) is an enlarged view. (3A) to (3D) are cross-sectional views for explaining the operation of the piezoelectric speaker. FIGS. 4A to 4E are cross-sectional views illustrating a method for manufacturing the piezoelectric speaker according to the first embodiment. FIGS. (5A) is a top view of the piezoelectric speaker according to the second embodiment, and (5B) and (5C) are cross-sectional views thereof. 6A to 6D are cross-sectional views illustrating a method for manufacturing a piezoelectric speaker according to a second embodiment. (7A) and (7B) are sectional views according to other embodiments.

  Hereinafter, embodiments of the present invention will be described in the following order with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected to the corresponding component in each figure, and the overlapping description is abbreviate | omitted.

1. First embodiment (Configuration)
1 and 2 are views showing a piezoelectric speaker according to an embodiment of the present invention. 1A is a top view of the piezoelectric speaker, FIG. 1B is a cross-sectional view taken along line 1B-1B in FIG. 1A, and FIG. 1C is a cross-sectional view taken along line 1C-1C in FIG. 1A. 2A is a bottom view of the piezoelectric speaker, and FIG. 2B is an enlarged view of a region 2B surrounded by a dashed ellipse in FIG. 1A. In each figure, xyz axes orthogonal to each other are defined for convenience of explanation. The thickness direction of the substrate corresponds to a direction parallel to the z axis, the first direction corresponds to a direction parallel to the x axis, and the second direction corresponds to a direction parallel to the y axis. The xy plane corresponds to a plane parallel to the main surface of the substrate.

  A piezoelectric speaker, which is a Heil-type speaker, is a laminated structure formed using a MEMS manufacturing process. A laminated structure constituting a piezoelectric speaker is mainly formed by laminating a plurality of layers described below. The base layer 10 is made of silicon (Si) having a thickness of 625 μm. The first insulating layer 11 and the second insulating layer 12 are made of silicon oxide having a thickness of 1 μm. The first SOI layer 13 and the second SOI layer 14 are made of silicon having a thickness of 10 μm. The third insulating layer 15 and the fourth insulating layer 16 are made of silicon oxide having a thickness of 0.5 μm.

  The piezoelectric speaker includes a frame portion S, a plurality of first flexible portions F1, a plurality of second flexible portions F2, a plurality of third flexible portions F3, and a plurality of piezoelectric elements P. . The frame portion S has a rectangular frame shape. The frame S includes a third insulating layer 15, a first SOI layer 13, a first insulating layer 11, a base layer 10, a second insulating layer 12, a second SOI layer 14, and a fourth insulating layer 16. The first flexible portion F1 is thin in the x-axis direction, and a plurality of first flexible portions F1 are arranged in the x-axis direction. The first flexible portions F1 are arranged in parallel to each other. Both end portions in the y-axis direction of the first flexible portion F1 are coupled to a pair of inner wall surfaces parallel to the xz plane of the frame portion S. The first flexible portion F <b> 1 includes a first insulating layer 11, a base layer 10, and a second insulating layer 12.

  The second flexible portion F2 is thin in the z-axis direction. The second flexible portion F2 connects two first flexible portions F1 adjacent to each other, and connects one end of the first flexible portion F1 in the z-axis direction one by one. Further, both end portions of the second flexible portion F2 in the y-axis direction are coupled to a pair of inner wall surfaces parallel to the xz plane of the frame portion S. Adjacent second flexible portions F2 are separated by a groove H1. The second flexible portion F <b> 2 includes the second SOI layer 14 and the fourth insulating layer 16.

  The 3rd flexible part F3 is two adjacent 1st flexible parts F1, Comprising: In the combination which the 2nd flexible part F2 connects, two 1st flexible parts F1 which belong to a different set are made into one set. The other ends of the first flexible part F1 in the z-axis direction are connected one by one. That is, the first flexible part F1, the second flexible part F2, and the third flexible part F3 form a heil type structure. The third flexible portion F3 connects the outermost first flexible portion F1 and the inner wall surface parallel to the yz plane of the frame portion S. Further, both end portions in the y-axis direction of the third flexible portion F3 are coupled to a pair of inner wall surfaces parallel to the xz plane of the frame portion S. Adjacent third flexible portions F3 are separated by a groove H2. The third flexible portion F3 is thin in the z-axis direction. The third flexible portion F <b> 3 includes the third insulating layer 15 and the first SOI layer 13.

  The length in the y-axis direction of the grooves H1, H2, that is, the length in the y-axis direction of the second flexible portion F2 and the third flexible portion F3 is preferably longer than the length in the y-axis direction of the piezoelectric element P. . As a result, when the second flexible part F2 or the third flexible part F3 is displaced as will be described later, it is possible to make it difficult to prevent the movement. Further, as shown in FIG. 2B, a surface facing the groove portion H1 of a portion (referred to as an extension portion) of the second flexible portion F2 extended from the length of the piezoelectric element P in the y-axis direction, and a surface facing the groove portion H1 The inner wall surface of the frame portion S has a corrugated shape having a curved surface. The surface facing the groove portion H2 of the extension portion of the third flexible portion F3 and the inner wall surface of the frame portion facing the groove portion H2 may similarly have a corrugated shape. As a result, the second flexible portion F2 and the third flexible portion F3 can be further easily displaced.

  A piezoelectric element P is formed on the surface of the second flexible portion F2 that is parallel to the surface coupled to the first flexible portion F1. The piezoelectric element P is formed by laminating a first electrode layer 17, a piezoelectric layer 18, and a second electrode layer 19 in this order. The first electrode layer 17 and the second electrode layer 19 are made of, for example, platinum (Pt) having a thickness of 0.1 μm. The piezoelectric layer 18 is made of lead zirconate titanate (PZT) having a thickness of 3 μm. The wiring part 21a connects the second electrode layers 19 of the piezoelectric elements P to each other. The wiring part 21 a is insulated from the first electrode layer 17 by the fifth insulating layer 20. The wiring part 21b connects the first electrode layers 17 of the piezoelectric elements P to each other. The wiring part 21a and the wiring part 21b are made of aluminum (Al) having a thickness of 0.5 μm.

(Operation)
FIG. 3 is a diagram for explaining the operation of the piezoelectric speaker. Each figure is a simplified cross-sectional view of a plane parallel to the xz plane near the center in the y-axis direction. The piezoelectric layer 18 expands or compresses depending on the polarity of the voltage applied to the first electrode layer 17 and the second electrode layer 19. When the piezoelectric layer 18 expands, the second flexible portion F2 bends so as to be convex in the + z direction as shown in FIGS. 3A and 3B. By bending the second flexible portion F2 in this way, the first flexible portion F1 is bent so that the width of the groove portion H1 in the x-axis direction is widened. As the first flexible part F1 bends in this way, the third flexible part F3 bends so as to be convex in the + z direction. When each flexible part deforms in this way, air is sucked into the groove part H1 from the outside, and air is discharged to the outside from the groove part H2.

  When the piezoelectric layer 18 is compressed, the second flexible portion F2 is bent so as to be convex in the −z direction as shown in FIGS. 3C and 3D. As the second flexible portion F2 is bent in this manner, the first flexible portion F1 is bent so that the width of the groove portion H2 in the x-axis direction is widened. As the first flexible part F1 bends in this way, the third flexible part F3 bends so as to be convex in the −z direction. When each flexible part is deformed in this way, air is discharged to the outside from the groove part H2, and air is sucked into the groove part H2 from the outside.

  As described above, by periodically changing the polarity of the voltage applied to the piezoelectric element P, it is possible to generate atmospheric pressure vibration and to function as a speaker. In addition, since the surface in the thickness direction of the substrate can also function as a diaphragm, the speaker can be downsized. Furthermore, since a piezoelectric layer made of an inorganic piezoelectric material is used, a larger sound pressure can be obtained than when a piezoelectric layer made of an organic piezoelectric material is used.

(Production method)
A method of manufacturing the piezoelectric speaker according to this embodiment will be described with reference to FIG. 4 is a cross-sectional view corresponding to the line 1B-1B in FIG. 1A. First, as shown in FIG. 4A, the third insulating layer 15 and the fourth insulating layer 16 are formed on both the front and back surfaces of the SOI substrate 100. The SOI substrate 100 is laminated in order on the base layer 10, the first insulating layer 11 and the first SOI layer 13 that are sequentially laminated on one main surface of the base layer 10, and the other main surface of the base layer 10. The second insulating layer 12 and the second SOI layer 14. The third insulating layer 15 and the fourth insulating layer 16 are silicon oxide layers formed by thermally oxidizing the SOI substrate 100.

  Subsequently, as shown in FIG. 4B, a first electrode layer 17, a piezoelectric layer 18, and a second electrode layer 19 are sequentially formed on the surface of the fourth insulating layer 16. As the first electrode layer 17 and the second electrode layer 19, a platinum (Pt) layer having a thickness of 0.1 μm is formed by sputtering. As the piezoelectric layer 18, a PZT film having a thickness of 3 μm is formed by sputtering or hydrothermal synthesis. Subsequently, as shown in FIG. 4C, the second electrode layer 19, the piezoelectric layer 18, and the first electrode layer 17 are etched one by one in order, and the first electrode layer 17, the piezoelectric layer 18, and the second electrode layer 19 are laminated. A plurality of piezoelectric elements are formed. Specifically, the second electrode layer 19 is etched by a milling method using Ar ions, for example, using a protective layer made of a photoresist (not shown), and the protective layer is removed after the etching. The piezoelectric layer 18 and the first electrode layer 17 are also etched by the same method.

Subsequently, as shown in FIG. 1C and FIG. 4D, the fifth insulating layer 20 is formed at one end in the y direction of the piezoelectric element P, and then the second electrode 21 b that connects the first electrode layers 17 of the piezoelectric element P to each other A wiring portion 21a that connects the electrode layers 19 is formed. As the fifth insulating layer 20, for example, photosensitive polyimide having a thickness of 5 μm is used. In addition, for example, a silicon dioxide film may be formed by a CVD (Chemical Vapor Deposition) method and then etched using a protective layer made of a photoresist (not shown). Moreover, you may form the 5th insulating layer 20 in the area | region which covers the end of the y-axis direction of a piezoelectric element using a screen printing method. For the wiring layer 21, for example, a wiring layer 21 made of aluminum (Al) having a thickness of 0.5 μm is formed by sputtering, and a wiring layer 21 is formed using Cl ₂ gas using a protective layer made of a photoresist (not shown). Is formed by reactive ion etching. After the etching, the protective layer is removed.

Subsequently, as shown in FIG. 4E, the fourth insulating layer 16, the second SOI layer 14, the second insulating layer 12, the base layer 10 and the first insulating layer 11 are etched using a protective layer (not shown) made of a photoresist. A groove H1 is formed. For example, as the etching of the fourth insulating layer 16, the second insulating layer 12, and the first insulating layer 11, a reactive ion etching method using CHF ₃ gas is used. For etching the second SOI layer 14, a reactive ion etching method using CF ₄ gas and O ₂ gas is used. In addition to the reactive ion etching method, a wet etching method using hydrofluoric acid or buffered hydrofluoric acid may be used. Deep-RIE (Reactive Ion Etching) of the base layer 10 uses a so-called Bosch process in which the steps of passivation (C ₄ F ₈ plasma) and etching (SF ₆ plasma) are repeated alternately. After the etching is completed, a protective layer (not shown) is removed. The top view at this point is shown in FIG. 1A. Depending on the shape of the protective layer used when forming the groove portion H1, a corrugated shape can be formed on the surface of the extension portion facing the groove portion H1 and the inner wall surface of the frame portion S facing the groove portion H1. .

  Subsequently, the third insulating layer 15, the first SOI layer 13, the first insulating layer 11, the base layer 10, and the second insulating layer 12 are etched using a protective layer (not shown) made of photoresist as a mask, and FIG. And as shown to FIG. 2A, the groove part H2 is formed. Etching the third insulating layer 15, the first insulating layer 11, and the second insulating layer 12 can be performed by the same method as the etching of the fourth insulating layer 16, the second insulating layer 12, and the first insulating layer 11. The etching of the first SOI layer 13 can be performed by the same method as the etching of the second SOI layer 14. Etching of the base layer 10 can also be performed in the same manner as in the step of FIG. 4E. After the etching, the protective layer is removed. Thereafter, the wafer is diced and mounted on a ceramic (or metal, silicon) package.

  Through the above steps, the piezoelectric speaker shown in FIGS. 1 and 2 can be manufactured. Since the surface in the thickness direction of the substrate can also function as a diaphragm, the speaker can be miniaturized. As a result, many speaker elements can be manufactured from one wafer, which can contribute to cost reduction.

2. Second embodiment (Configuration)
The configuration of the piezoelectric speaker according to the second embodiment of the present invention will be described with reference to FIG. 5A is a top view of the piezoelectric speaker, FIG. 5B is a cross-sectional view taken along line 5B-5B in FIG. 5A, and FIG. 5C is a cross-sectional view taken along line 5C-5C in FIG. The frame S includes a first SOI layer 13, a first insulating layer 11, a base layer 10, a second insulating layer 12, a second SOI layer 14, a fourth insulating layer 16, and a sixth insulating layer 22. The sixth insulating layer 22 is made of silicon nitride (SiN) having a thickness of 3 μm. The first flexible portion F <b> 1 is composed of the sixth insulating layer 22. The second flexible portion F <b> 2 includes the second insulating layer 12, the second SOI layer 14, and the fourth insulating layer 16. The third flexible portion F3 is composed of the sixth insulating layer 22. A piezoelectric element P is formed on the surface of the second flexible portion F2.

(Operation)
By applying a predetermined voltage whose polarity is periodically reversed to the piezoelectric element P, each flexible portion can be vibrated similarly to the first embodiment, and can function as a speaker. Moreover, since the 1st flexible part F1 can be formed thinly with the manufacturing method mentioned later, the displacement width | variety can be enlarged.

(Production method)
A method for manufacturing a piezoelectric speaker according to the second embodiment will be described with reference to FIG. As shown in FIG. 6A, an SOI substrate 100 similar to that of the first embodiment is prepared, and a third insulating layer 15 and a fourth insulating layer 16 are formed on both the front and back surfaces of the SOI substrate 100. Note that an SOI substrate in which the base layer 10, the second insulating layer 12, and the second substrate layer 14 are laminated in this order is prepared, and Tempax glass having a thickness of 0.2 mm is bonded to the base layer 10 by anodic bonding. Also good. Subsequently, similarly to the steps shown in FIGS. 4B and 4C of the first embodiment, the first electrode layer 17, the piezoelectric layer 18, and the second electrode layer 19 are formed on the surface of the fourth insulating layer 16. A plurality of piezoelectric elements P are formed by etching.

Subsequently, as shown in FIG. 6B, the fourth insulating layer 16, the second SOI layer 14, the second insulating layer 12, the base layer 10, and the first insulating layer 11 are used using a protective layer (not shown) made of a photoresist as a mask. Is etched to form the groove H1. For the etching of each layer, a method similar to the method described in FIG. 4E can be used. Thereafter, the protective layer is removed. Subsequently, as shown in FIG. 6C, the sixth insulating layer 22 is conformally formed, and the contact hole H3 is formed by etching the sixth insulating layer 22 using a protective layer (not shown) as a mask. The layer 19 and the first electrode layer 17 are exposed. As the sixth insulating layer 22, a silicon nitride (SiN) film having a thickness of 3 μm is formed by, eg, CVD. For example, when a CVD apparatus “HiDep” manufactured by BMR is used, Si ₃ N ₄ can be formed at a process temperature of less than 100 ° C. An SiO ₂ film may be formed by CVD using ozone (O ₃ ) and tetraethoxysilane (TEOS) instead of SiN. Note that case, the lower surface of the SiO ₂ film (i.e. before forming the SiO ₂ film) it is desirable that the SiN film is formed thinly. An organic film may be used instead of an inorganic film such as SiN or SiO ₂ . For example, a polyimide film may be formed using a vapor deposition polymerization method. Alternatively, the parylene film may be formed using a CVD method. For the etching of the sixth insulating layer 22, for example, a reactive ion etching method using CHF ₃ gas is used. After the etching, the protective layer is removed.

Subsequently, as shown in FIG. 6D, wiring portions 21a and 21b are formed. Specifically, for example, Al is deposited with a thickness of 1 μm using a metal mask. Alternatively, the wiring portions 21a and 21b may be formed by screen printing using Ag paste. Moreover, you may form wiring part 21a, 21b by the inkjet method using Ag nano ink. Subsequently, a third insulating layer 15 is formed using a protective layer made of a photoresist (not shown) (a protective layer that covers the back surface of the frame S and exposes an entire area inside the frame S) as a mask. The trench H2 is formed by removing the first SOI layer 13, the first insulating layer 11, and the base layer 10 by etching. Specifically, for example, a reactive ion etching method using CHF ₃ gas is used for etching the third insulating layer 15 and the first insulating layer 11. For the etching of the first SOI layer 13, a reactive ion etching method using CF ₄ gas and O ₂ gas is used. In addition to the reactive ion etching method, a wet etching method using hydrofluoric acid or buffered hydrofluoric acid may be used. Deep-RIE (Reactive Ion Etching) of the base layer 10 uses a so-called Bosch process in which the steps of passivation (C ₄ F ₈ plasma) and etching (SF ₆ plasma) are repeated alternately. Since the sixth insulating layer 22 is made of a material (SiN film or organic film) having etching selectivity with respect to each of the layers etched using the above etching method, the sixth insulating layer 22 may remain. it can. Further, a protective layer in which one opening is formed so as to cover the back surface of the frame portion S and expose the entire inner region of the frame portion S is used for each etching. Therefore, compared with the case of using a protective layer in which an opening is formed in accordance with the formation region of each groove H2, the protective layer of the present embodiment does not need to be so high with respect to the positional accuracy of photolithography. It also leads to reduction. After etching, the protective layer is removed and dicing is performed to manufacture the piezoelectric speaker shown in FIG.

3. Other Embodiments The technical scope of the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the scope of the present invention. For example, the materials, shapes, dimensions, film formation methods, and pattern transfer methods shown in the above embodiment are merely examples, and the addition and deletion of processes and the replacement of process order that are obvious to those skilled in the art are described. It is omitted. The present invention can be applied not only to a speaker but also to various actuators.

Each part constituting the piezoelectric speaker may be composed of layers as shown in FIG. 7A. The frame portion S includes a first insulating layer 11, a base layer 10, and a second insulating layer 12. The first flexible part F <b> 1 is made of the base layer 10. The second flexible part F <b> 2 is made of the second insulating layer 12. The third flexible portion F3 is made of the second insulating layer 12.
In the above-described embodiment, the configuration in which the piezoelectric element P is provided on the surface of the second flexible portion F2 has been described. However, the piezoelectric element P is provided in both the second flexible portion F2 and the third flexible portion F3. May be provided. When the piezoelectric elements P are provided on both sides, the displacement width of the first flexible portion F1 can be increased, and a large sound pressure can be obtained.
In addition to PZT, barium titanate (BaTiO ₂ ), lithium niobate (LiNbO ₂ ), or the like may be used as the inorganic piezoelectric material.

  F1: first flexible part, F2: second flexible part, F3: third flexible part, H1: groove part, H2: groove part, P: piezoelectric element

Claims (4)

A plurality of first flexible portions, which are thin plate-like first flexible portions in a first direction parallel to the main surface of the substrate perpendicular to the thickness direction of the substrate, and are arranged in the first direction parallel to each other. And
A pair of two adjacent first flexible portions, a second flexible portion that connects one end of the first flexible portion in the thickness direction one by one;
In the combination of the first flexible parts to which the second flexible part is connected, two adjacent first flexible parts belonging to different sets are taken as one set, and the thickness of the first flexible part is set one by one. A third flexible portion that connects the other ends in the direction;
At least one of the second flexible part and the third flexible part is formed on a plane parallel to the main surface of the substrate, and is sandwiched between two electrode layers and the two electrode layers A piezoelectric element having a piezoelectric layer made of a piezoelectric material;
A rectangular frame-shaped frame portion, in a pair of opposed inner wall surfaces, both end portions of the first flexible portion and the second flexible portion in a second direction orthogonal to the thickness direction and the first direction Frame portions coupled to both end portions of the third flexible portion and both end portions of the third flexible portion;
A piezoelectric actuator comprising: The length in the second direction of the surface on which the piezoelectric element of the second flexible part or the third flexible part is formed is longer than the length of the piezoelectric element in the second direction.
The piezoelectric actuator according to claim 1. The first flexible part includes a thin plate formed by deeply digging a silicon layer constituting the substrate from both the main surface side and the other main surface side of the substrate by anisotropic etching. It is configured,
The piezoelectric actuator according to claim 1 or 2. The first flexible portion is made of an inorganic compound or organic compound film formed by vapor deposition polymerization or CVD.
The piezoelectric actuator according to claim 1 or 2.

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