MEMS transducer

Abstract

To provide a MEMS transducer in which warpage due to variations in the in-plane direction of residual stress is suppressed to a good degree.SOLUTION: A MEMS transducer (1) includes a support part (2) and a vibration part (32). The vibrating part is formed as a flat plate shape having a thickness direction along a directional axis (CA) and flexes and vibrates in a mode in which a belly of the vibration moves along the directional axis. The support part fixedly supports a fixed end part (32a), constituting a node of the vibration in the vibrating part. The vibrating part extends from the fixed end part toward the directional axis. The vibrating part includes a stress adjusting layer (36). The stress adjusting layer is provided along the in-plane direction so as to be capable of adjusting the variation of residual stress in the in-plane direction that intersects the directional axis. The stress adjusting layer is provided on the outermost layer side in the thickness direction of the vibrating part and is divided into a plurality of portions in the in-plane direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a MEMS transducer. MEMS stands for Micro Electro Mechanical Systems. [Background technology]

[0002] The MEMS transducer described in Japanese Patent No. 5936154 includes a substrate and multiple tapered transducer beams. In this MEMS transducer, each tapered transducer beam includes a piezoelectric layer that converts applied pressure into voltage and a pair of electrode layers sandwiching the piezoelectric layer. Each tapered transducer beam has a beam base end, a beam tip end, and a beam body. The tapered transducer beam is connected to the substrate in a cantilever configuration by attaching the beam base end to the substrate.

[0003] However, in this type of MEMS transducer, deformation such as warping caused by residual stress can become a problem. In this regard, Patent Document 1 discloses a technology for suppressing deformation of the cantilever structure and flattening it by providing a difference in average residual stress between the first piezoelectric layer and the second piezoelectric layer in a transducer having a first piezoelectric layer and a second piezoelectric layer provided on the first piezoelectric layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] US Patent Application Publication No. 2018 / 0159021 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in this type of configuration, stress variations can occur in the in-plane direction perpendicular to the thickness direction of the transducer due to film formation processes such as sputtering during manufacturing. Therefore, even if a planarization technique such as that described in Patent Document 1 is used, there is a possibility that deformation, i.e., warpage, cannot be sufficiently suppressed. The present invention has been made in consideration of the circumstances exemplified above. That is, the present invention provides, for example, a MEMS transducer in which warpage caused by variations in residual stress in the in-plane direction is effectively suppressed. [Means for solving the problem]

[0006] The MEMS transducer (1) according to claim 1 comprises: a vibration section (32) formed in a flat plate shape having a thickness direction along a directivity axis (DA) and configured to flexibly vibrate in a manner in which the antinode of vibration moves along the directivity axis; a support portion (2) provided to fixedly support a fixed end portion (32a) that constitutes a vibration node of the vibration portion; Equipped with The vibration unit is extending from the fixed end toward the pointing axis, a stress adjustment layer (36) provided along an in-plane direction intersecting the orientation axis so as to be able to adjust variations in residual stress in the in-plane direction, The stress adjustment layer is before The vibration part is provided on the outermost layer side in the thickness direction. R, and, The extension direction intersects with the in-plane direction from the fixed end toward the directional axis. the in-plane direction In the width direction, It is divided into several parts and is provided so that compressive residual stress and tensile residual stress are generated alternately in the width direction. are.

[0007] In addition, in each section of the application documents, each element may be assigned a reference symbol in parentheses. In this case, the reference symbol merely indicates an example of the correspondence between the element and the specific configuration described in the embodiment described below. Therefore, the present invention is not limited in any way by the description of the reference symbol. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a side cross-sectional view showing a schematic configuration of a MEMS transducer according to a first embodiment of the present invention. [Figure 2] 2 is a plan view showing a schematic configuration of a stress adjustment layer provided in the vibrating section shown in FIG. 1. FIG. [Figure 3] FIG. 4 is a side cross-sectional view showing a schematic configuration of a MEMS transducer according to a second embodiment of the present invention. [Figure 4] 4 is a plan view showing a schematic configuration of a stress adjustment layer provided in the vibrating section shown in FIG. 3. FIG. [Figure 5] FIG. 10 is a side cross-sectional view showing a schematic configuration of a MEMS transducer according to a third embodiment of the present invention. [Figure 6] 6 is a plan view showing a schematic configuration of a stress adjustment layer provided in the vibrating section shown in FIG. 5. DETAILED DESCRIPTION OF THE INVENTION

[0009] (Embodiment) Hereinafter, embodiments of the present invention will be described with reference to the drawings. Incidentally, if various modifications applicable to one embodiment are inserted in the middle of a series of descriptions relating to that embodiment, understanding of that embodiment may be hindered. Therefore, the modifications will not be inserted in the middle of a series of descriptions relating to that embodiment, but will be described together after that. Furthermore, the descriptions of the drawings and the corresponding device configurations, functions, or operations described below are simplified for the purpose of concisely explaining the contents of the present invention and do not in any way limit the contents of the present invention. Therefore, it goes without saying that the exemplary configurations shown in the drawings do not necessarily correspond to the specific configurations actually manufactured and sold. In other words, unless expressly limited by the applicant in the prosecution history of this application, the present invention should not be construed as being limited by the descriptions of the drawings and the corresponding device configurations, functions, or operations described below.

[0010] (First embodiment) A MEMS transducer 1 according to a first embodiment will be described with reference to FIGS. 1 and 2. For ease of explanation, a right-handed XYZ Cartesian coordinate system is set so that the Z axis is parallel to the directional axis DA, as shown in the figure. The directional axis DA is an imaginary line that serves as a reference for the directivity of the MEMS transducer 1 that transmits or receives sound waves or ultrasonic waves, and may also be referred to as the "center directional axis." The directional axis DA typically corresponds to an imaginary line that indicates the axial center of a three-dimensional shape, such as a substantially conical or spindle-shaped shape, representing the range of directivity, e.g., the range in which a predetermined gain or a predetermined sound level can be obtained. Specifically, for example, the directional axis DA is the central axis of the sound pressure half-angle. Hereinafter, the direction along the directional axis DA, i.e., the direction parallel to the directional axis DA, will be referred to as the "axial direction." Therefore, the axial direction is parallel to the Z axis in the drawings. Furthermore, a direction intersecting the axial direction, typically any direction perpendicular to the axial direction, will be referred to as the "in-plane direction." The "in-plane direction" is a direction parallel to the XY plane in the drawing. The "in-plane direction" may also be referred to as the "radial direction" in some cases. The "radial direction" is a direction perpendicular to the pointing axis DA and moving away from the pointing axis DA. In other words, the "radial direction" is the direction in which a half-ray extends when a half-ray is drawn in an imaginary plane perpendicular to the pointing axis DA, starting from the intersection of the pointing axis DA and the imaginary plane perpendicular to the pointing axis DA. In other words, the "radial direction" is the radial direction of a circle drawn in the imaginary plane with the intersection of the pointing axis DA and the imaginary plane perpendicular to the pointing axis DA as its center. The "in-plane direction" may also be referred to as the "circumferential direction" in some cases. The "circumferential direction" is the circumferential direction of a circle drawn in the imaginary plane with the intersection of the pointing axis DA and the imaginary plane perpendicular to the pointing axis DA as its center. Furthermore, viewing the MEMS transducer 1 and its components from above in FIG. 1 with a line of sight parallel to the negative Z-axis direction is referred to as a "planar view." That is, the shape of a certain component in a "planar view" corresponds to the shape of the same component when it is mapped onto the XY plane in the drawing.

[0011] The MEMS transducer 1 as an electroacoustic transducer is configured to perform a function of converting an electric signal to a sound wave vibration or an ultrasonic vibration. In this embodiment, the MEMS transducer 1 is configured as a so-called piezoelectric MEMS microphone. Specifically, as shown in FIG. 1, the MEMS transducer 1 includes a support portion 2 and a piezoelectric element portion 3.

[0012] The support part 2 is a cylindrical or annular member surrounding the pointing axis DA, and is formed, for example, from ceramics such as alumina or a silicon-based semiconductor substrate. In this embodiment, the support part 2 has a square cylindrical or annular shape with the pointing axis DA as its central axis. Specifically, the support part 2 has a structure in which four flat plate-shaped or four square rod-shaped wall members, each having predetermined dimensions in the axial and radial directions and arranged parallel to the pointing axis DA, are joined together seamlessly. Furthermore, the support part 2 has a square outer shape in a plan view.

[0013] The support portion 2 has an outer wall surface 21 that is parallel to the pointing axis DA and exposed radially outward, and an inner wall surface 22 that is parallel to the pointing axis DA and surrounds the pointing axis DA. A cavity 23, which is the space surrounded by the inner wall surface 22, is formed into a quadrangular prism that is square in plan view. The support portion 2 also has an upper end surface 24 that is the end surface on one side in the axial direction, i.e., the positive Z-axis side in the figure, and a lower end surface 25 that is the end surface on the other side in the axial direction, i.e., the negative Z-axis side in the figure. The upper end surface 24 and the lower end surface 25 are formed into flat planes with the axial direction as the normal direction. The upper end surface 24 is bonded to the piezoelectric element portion 3 via an oxide film 4.

[0014] The piezoelectric element portion 3 is formed in the shape of a thin plate having a thickness direction in the axial direction. In this embodiment, the piezoelectric element portion 3 is formed in a square shape in a plan view corresponding to the square outer shape of the support portion 2 in a plan view. The piezoelectric element portion 3 has a fixed portion 31 and a vibrating portion 32. The fixed portion 31 is the peripheral portion of the piezoelectric element portion 3, i.e., the outer edge portion in the radial direction, and is fixed to the support portion 2 by being bonded to the upper end surface 24 of the support portion 2 via an oxide film 4. The vibrating portion 32 is provided radially inward of the fixed portion 31. The vibrating portion 32 is formed in the shape of a flat plate having a thickness direction along the directional axis DA, and is configured to flexurally vibrate in a manner such that the antinode of vibration moves along the directional axis DA.

[0015] In this embodiment, the vibrating unit 32 is formed in a cantilever shape extending from the fixed unit 31 toward the pointing axis DA. Specifically, the vibrating unit 32 has a fixed end 32a and a free end 32b. The fixed end 32a constitutes a vibration node of the vibrating unit 32 and is provided at a position corresponding to the inner wall surface 22 of the support unit 2 in a plan view. That is, the vibrating unit 32 extends from the fixed end 32a toward the pointing axis DA so as not to be adjacent to the support unit 2 in an axial direction parallel to the pointing axis DA. In other words, the vibrating unit 32 is disposed adjacent to the cavity 23 in the axial direction. The free end 32b, which constitutes a vibration antinode of the vibrating unit 32, is the end of the vibrating unit 32 closest to the pointing axis DA and is provided slightly closer to the fixed end 32a than the pointing axis DA. That is, the pointing axis DA does not pass through the tip end, which is the end of the vibrating unit 32 on the free end 32b side, but passes through a slit 33 provided between a pair of adjacent vibrating units 32 in the radial direction. The vibration section 32, which is the vibration region of the piezoelectric element section 3, is provided so as to be vibrable in such a manner that its fixed end 32a is fixedly supported by the support section 2 while its free end 32b moves along the directional axis DA. As shown in FIG. 2, the vibration section 32 is formed so that its width narrows from the fixed end 32a to the free end 32b. Specifically, the vibration section 32 has a substantially isosceles triangular shape in plan view, with the fixed end 32a as its base and the free end 32b as its apex. The extension line LE shown in FIG. 2 is an imaginary line parallel to the extension direction of the vibration section 32, i.e., the positive direction of the X-axis in the figure. The width direction line LW shown in FIG. 2 is an imaginary line parallel to the width direction of the vibration section 32, i.e., the Y-axis direction in the figure.

[0016] In this embodiment, the piezoelectric element part 3 has a plurality of vibration parts 32. The plurality of vibration parts 32 are arranged at equal intervals in the circumferential direction. Fig. 1 shows an enlarged view of the periphery of one of the plurality of vibration parts 32 that extends in the positive direction of the X-axis. Each of the plurality of vibration parts 32 is divided in the in-plane direction by a slit 33 that is provided so as to penetrate the piezoelectric element part 3 in the thickness direction.

[0017] The piezoelectric element section 3 includes a piezoelectric layer 34, an electrode layer 35, and a stress adjustment layer 36, and has a configuration in which the piezoelectric layer 34, the electrode layer 35, and the stress adjustment layer 36 are stacked in the thickness direction. The piezoelectric layer 34 is formed as a thin film from a piezoelectric material such as scandium aluminum nitride. The electrode layers 35 are formed from a conductive material such as metal, and are provided on both sides of the piezoelectric layer 34.

[0018] In this embodiment, the piezoelectric element unit 3 has a multilayer structure in which multiple piezoelectric layers 34 are stacked in the axial direction. Specifically, the piezoelectric element unit 3 is configured by stacking a first piezoelectric layer 341, a second piezoelectric layer 342, an upper electrode 351, an intermediate electrode 352, and a lower electrode 353 in the thickness direction. The first piezoelectric layer 341 and the second piezoelectric layer 342 each have a pair of flat, planar principal surfaces with the axial direction as the normal direction. The "principal surfaces" refer to the surfaces of a plate-shaped, layer-shaped, or film-shaped part or member that are perpendicular to the thickness direction. The second piezoelectric layer 342 is disposed between the support unit 2 and the first piezoelectric layer 341 in the axial direction. The upper electrode 351 is formed on the upper surface of the first piezoelectric layer 341, i.e., on the principal surface facing the positive direction of the Z axis. The intermediate electrode 352 is disposed between the first piezoelectric layer 341 and the second piezoelectric layer 342. 1, the intermediate electrode 352 is provided so as to overlap with the neutral axis LA that passes through the center in the thickness direction of the vibrating section 32 and extends along the extension direction of the vibrating section 32 in a side cross-sectional view. The lower electrode 353 is formed on the bottom surface of the second piezoelectric layer 342, i.e., on the main surface facing the cavity 23.

[0019] The upper electrode 351 is provided so as to straddle the fixed portion 31 and the fixed end portion 32a in the extension direction of the vibrating portion 32. That is, the upper electrode 351 is provided so as to protrude from the inner wall surface 22 of the support portion 2 in the extension direction of the vibrating portion 32 in a plan view. Specifically, the upper electrode 351 extends from the fixed end portion 32a toward the free end portion 32b toward the vibrating portion 32 by a length of approximately 1 / 6 to 2 / 5 (more preferably approximately 1 / 4 to 1 / 3) of the beam length, which is the protruding length between the fixed end portion 32a and the free end portion 32b. The intermediate electrode 352 and the lower electrode 353 have a base electrode portion 354 and a movable electrode portion 355. The base electrode portion 354 is disposed at a position overlapping the upper electrode 351 in a plan view. That is, the base electrode portion 354 is provided so that its outer shape when projected onto the XY plane substantially matches the outer shape of the upper electrode 351. The movable electrode portion 355 is provided from a position slightly spaced from the base end electrode portion 354 to the free end portion 32b in the extension direction of the vibration portion 32. That is, the movable electrode portion 355 is disposed on the vibration portion 32.

[0020] The stress adjustment layer 36 is provided in the vibrating part 32. The stress adjustment layer 36 is provided along the in-plane direction so as to be able to adjust variations in the residual stress of the vibrating part 32 in the in-plane direction. The stress adjustment layer 36 is provided on the outermost layer side in the thickness direction of the vibrating part 32. Specifically, the stress adjustment layer 36 is formed on the main surface of the first piezoelectric layer 341 facing the positive direction of the Z axis. In other words, the stress adjustment layer 36 is provided in the same layer as the upper electrode 351 in the thickness direction.

[0021] The stress adjustment layer 36 has a configuration in which the residual stress can be adjusted by heat, and is formed of a material different from that of the intermediate electrode 352 and the lower electrode 353. Specifically, the stress adjustment layer 36 is formed of a material in which the stress can be varied at a lower temperature than the piezoelectric layer 34 and the electrode layer 35. More specifically, the stress adjustment layer 36 is formed of a metal material with a lower melting point than the piezoelectric layer 34 and the electrode layer 35, more preferably an amorphous metal material.

[0022] The stress adjustment layer 36 is divided into a plurality of parts in the in-plane direction. That is, the stress adjustment layer 36 has a plurality of unit adjustment portions 361 arranged in the in-plane direction. A groove portion 362 is formed between adjacent unit adjustment portions 361 in the in-plane direction. In this embodiment, as shown in FIGS. 1 and 2, the stress adjustment layer 36 is divided into a plurality of parts in the extension direction from the fixed end portion 32a to the directional axis DA, i.e., the free end portion 32b. Specifically, as shown in FIG. 2, the unit adjustment portion 361 is formed in a trapezoidal or isosceles triangular shape having a base parallel to the width direction line LW in a plan view. Each of the plurality of unit adjustment portions 361 is formed so that its dimensions in the extension direction are approximately equal. The groove portion 362 that separates adjacent unit adjustment portions 361 in the in-plane direction is formed parallel to the width direction line LW. Each of the plurality of unit adjustment portions 361 and groove portions 362 is formed with a substantially uniform width in the direction parallel to the extension line LE. Furthermore, each of the plurality of unit adjustment portions 361 and groove portions 362 is arranged at substantially uniform intervals in the direction parallel to the extension line LE. The stress adjustment layer 36 is divided into a plurality of portions in the in-plane direction, i.e., each of the plurality of unit adjustment portions 361, and is provided so as to be capable of individually adjusting stress. In other words, the stress adjustment layer 36 is configured so as to be capable of individually adjusting the heating or heat generation state in each of the plurality of unit adjustment portions 361, thereby adjusting the distribution of residual stress in the vibration portion 32 in the in-plane direction.

[0023] (effect) Below, an outline of the operation of the configuration of this embodiment will be described together with the effects achieved by the configuration, with reference to the drawings.

[0024] The MEMS transducer 1 according to this embodiment has a function of converting strain caused by flexural deformation when the free end 32b of the vibrating part 32 moves along the directional axis DA into a voltage between a pair of electrode layers 35 provided on both sides of the piezoelectric layer 34. That is, for example, flexural vibration of the vibrating part 32 caused by receiving sound waves or ultrasonic waves is extracted as an inter-electrode voltage. Alternatively, for example, application of an inter-electrode voltage from the outside causes the vibrating part 32 to flexurally vibrate, thereby transmitting sound waves or ultrasonic waves.

[0025] In the above-described structure for converting bending vibration and electrical signals in the flat vibrating portion 32, residual stress distribution in the thickness direction can disrupt the moment balance and cause warpage. In particular, when the vibrating portion 32 has a cantilever structure, such as the MEMS transducer 1 according to this embodiment, warpage widens the opening width of the aperture centered on the directivity axis DA. This results in loss of low-frequency sound, reducing sensitivity in the low-frequency range. Regarding this issue, Patent Document 1 proposes a technique for suppressing warpage in a cantilever structure by adjusting stress in the thickness direction. However, film formation processes such as sputtering during manufacturing can cause stress variations in the in-plane direction perpendicular to the thickness direction. Therefore, even if the planarization technique described in Patent Document 1 is used, warpage may not be sufficiently suppressed.

[0026] Therefore, in this embodiment, the vibrating section 32 includes a stress adjustment layer 36. The stress adjustment layer 36 is provided on the outermost layer side in the thickness direction of the vibrating section 32 and is divided into multiple sections in the in-plane direction. The stress adjustment layer 36 is provided so that each of the multiple sections divided in the in-plane direction, i.e., each of the multiple unit adjustment sections 361, can have its stress adjusted individually. The stress adjustment layer 36 has a configuration in which residual stress can be adjusted by heat. Specifically, the stress adjustment layer 36 is formed of a material whose stress can be varied at a lower temperature than the piezoelectric layer 34 and the electrode layer 35. That is, the stress adjustment layer 36 is formed of a material different from the intermediate electrode 352 and the lower electrode 353. More specifically, the stress adjustment layer 36 is formed of a metal material with a lower melting point than the piezoelectric layer 34 and the electrode layer 35. For example, if the intermediate electrode 352 and the lower electrode 353 are formed of molybdenum, the stress adjustment layer 36 can be formed of aluminum.

[0027] According to this configuration, by individually adjusting the heating or heat generation state of each of the multiple unit adjustment parts 361 arranged in the in-plane direction, it is possible to adjust the distribution of residual stress in the vibration part 32 in the in-plane direction. Specifically, for example, it is possible to individually control the irradiation state of electromagnetic waves such as laser light and the energization state of each of the multiple unit adjustment parts 361. This makes it possible to change the amount of stress fluctuation due to annealing above and below the neutral axis LA. Therefore, it is possible to reduce the moment and suppress the amount of warpage after checking the results. By subdividing the stress adjustment layer 36 in the in-plane direction, it is possible to finely adjust the warpage.

[0028] By forming the stress adjustment layer 36 from a material whose stress can be varied at a lower temperature than the piezoelectric layer 34 and the electrode layer 35, other film stresses do not change during annealing, making it possible to effectively control warpage. Furthermore, by forming the stress adjustment layer 36 from a metal material with a lower melting point than the piezoelectric layer 34 and the electrode layer 35, it is possible to adjust warpage over a wide range by using the large thermal expansion coefficient of the stress adjustment layer 36. Furthermore, by forming the stress adjustment layer 36 from an amorphous metal material, it is possible to effectively suppress oxidation during heating.

[0029] Second Embodiment The second embodiment will be described below with reference to FIGS. 3 and 4. In the following description of the second embodiment, differences from the first embodiment will be mainly described. In addition, identical or equivalent parts in the first and second embodiments are denoted by the same reference numerals. Therefore, in the following description of the second embodiment, the description of the first embodiment can be appropriately applied to components having the same reference numerals as those in the first embodiment, unless there is a technical contradiction or a special additional explanation. The same applies to the third embodiment described below.

[0030] In the first embodiment, as shown in Figures 1 and 2, the stress adjustment layer 36 is divided into multiple parts in the direction from the fixed end 32a to the free end 32b, i.e., toward the directional axis DA. In contrast, in the present embodiment, as shown in Figure 4, the stress adjustment layer 36 is divided into multiple parts in the width direction, which is an in-plane direction intersecting the extension direction of the vibration part 32. Specifically, in the example shown in Figure 4, multiple linear grooves 362 are formed radially from the free end 32b. The multiple grooves 362 are provided at equal intervals in the width direction.

[0031] This configuration can achieve the same effects as the first embodiment. Furthermore, it is possible to individually adjust the heating or heat generation state of each of the multiple unit adjustment portions 361 so that a rectangular wave-like or cosine wave-like stress distribution occurs along the width direction line LW, specifically, so that compressive residual stress and tensile residual stress alternate in the width direction. This increases the second moment of area, effectively stiffening the cantilever structure of the vibrating portion 32 while reducing warpage and flattening it.

[0032] (Third embodiment) A third embodiment will be described below with reference to FIGS. 5 and 6. In this embodiment, the stress adjustment layer 36 is divided into multiple parts in the extension direction and width direction of the vibrating section 32. This configuration not only achieves the same effects as the first and second embodiments, but also enables more precise stress adjustment in the in-plane direction. Specifically, for example, by confining the heated or heat-generating region to the distal end in the extension direction, the cantilever structure of the vibrating section 32 is effectively stiffened. This prevents deformation near the detection region surrounded by the two-dot chain line in FIG. 5, i.e., near the fixed end 32a, thereby suppressing sensitivity degradation. Furthermore, by heating near the fixed end 32a in a manner that reduces warping of the entire cantilever structure of the vibrating section 32, sensitivity can be improved.

[0033] (Variation) The present invention is not limited to the above-described embodiment. Therefore, the above-described embodiment can be modified as appropriate. Representative modifications will be described below. In the following description of the modifications, differences from the above-described embodiment will be mainly described. Furthermore, the same reference numerals are used for parts that are identical or equivalent to each other in the above-described embodiment and the modifications. Therefore, in the following description of the modifications, the description of the above-described embodiment can be used as appropriate for components that have the same reference numerals as the above-described embodiment, unless there is a technical contradiction or special additional explanation.

[0034] The present invention is not limited to the specific device configurations described in the above embodiments. That is, as mentioned above, the description of the above embodiments has been simplified to concisely explain the contents of the present invention. Therefore, it goes without saying that the exemplary configurations shown in the drawings do not necessarily match the specific configurations actually manufactured and sold. Specifically, for example, illustrations and descriptions of components typically provided in products actually manufactured and sold, such as casings, bonding materials, terminals, and wiring, have been omitted as appropriate in the above embodiments and corresponding drawings.

[0035] The support portion 2 may have a shape such as a cylindrical shape, an elliptical shape, a triangular shape, a pentagonal shape, a hexagonal shape, or an octagonal shape surrounding the pointing axis DA. Alternatively, the support portion 2 may have a shape such as a circular ring shape, an elliptical ring shape, a triangular ring shape, a pentagonal ring shape, a hexagonal ring shape, or an octagonal ring shape surrounding the pointing axis DA. Similarly, the piezoelectric element portion 3 may have a shape such as a circular shape, an elliptical shape, a triangular shape, a pentagonal shape, a hexagonal shape, or an octagonal shape in a plan view.

[0036] In the above embodiment, the piezoelectric element portion 3 is fixed to the upper end surface 24 of the support portion 2, but the present invention is not limited to this aspect. For example, the outer edge of the piezoelectric element portion 3 in the in-plane direction or the radial direction, which constitutes the fixed end portion 32a, may be fixed by a groove, adhesive layer, or the like provided on the inner wall surface 22 of the support portion 2. In other words, the fixed portion 31 of the piezoelectric element portion 3, which does not flexurally vibrate, may be omitted. In this case, the entire piezoelectric element portion 3 constitutes the vibrating portion 32 which flexurally vibrates.

[0037] There is no particular limitation on the number of cantilever-shaped vibration parts 32 provided on the piezoelectric element part 3. That is, for example, the piezoelectric element part 3 may have a pair of vibration parts 32 facing each other, similar to the configuration described in WO 2007 / 060768. Alternatively, for example, the piezoelectric element part 3 may have three or five or more vibration parts 32.

[0038] The vibrating section 32 is not limited to a cantilever structure. That is, for example, the vibrating section 32 may have a doubly supported beam structure. Alternatively, for example, the vibrating section 32 may have a diaphragm structure or a membrane structure that is fixedly supported by the support section 2 over the entire circumferential direction.

[0039] There is no particular limitation on the number of piezoelectric layers 34 or electrode layers 35. That is, for example, three or more piezoelectric layers 34 may be provided. In this case, multiple intermediate electrodes 352 are also provided.

[0040] The structure and arrangement of the stress adjustment layer 36 can also be modified as appropriate. Specifically, for example, a protective layer such as a coating layer covering the upper electrode 351 and the stress adjustment layer 36 can be provided. In this case, the stress adjustment layer 36 is not the "topmost layer" or "outermost layer" in the thickness direction of the vibrating section 32, but can be evaluated as being provided "on" the "side" of the topmost layer or "on" the "side" of the outermost layer in the thickness direction of the vibrating section 32. The stress adjustment layer 36 may also be provided so as to overlap the fixing section 31 in the in-plane direction. The stress adjustment layer 36 may also be provided in the same layer as the lower electrode 353 in the thickness direction of the piezoelectric element section 3, i.e., on the "side" of the outermost layer of the piezoelectric element section 3 that is closer to the support section 2 or the cavity 23. In this case, the upper electrode 351 can be provided so as to reach the free end 32b.

[0041] 2, the grooves 362 are formed in straight lines parallel to the width direction line LW. However, the present invention is not limited to this. For example, the grooves 362 may be formed in curved lines such as concentric circles.

[0042] 4, the plurality of linear grooves 362 are formed radially from the free end 32b. However, the present invention is not limited to this embodiment. That is, for example, the plurality of linear grooves 362 may be formed parallel to the extension line LE. Alternatively, the grooves 362 that overlap with the extension line LE in a plan view may be formed linearly, while the other grooves 362 may be formed in a curved shape, such as a hyperbolic shape, with the linear grooves 362 as an asymptote.

[0043] In the above description, multiple components that are formed seamlessly together may be formed by bonding separate members together. Similarly, multiple components that are formed by bonding separate members together may be formed seamlessly together.

[0044] In the above description, multiple components that are made of the same material may be made of different materials, and similarly, multiple components that are made of different materials may be made of the same material.

[0045] It goes without saying that the elements constituting the above-described embodiments are not necessarily essential unless they are particularly clearly stated as essential or are considered to be clearly essential in principle. Furthermore, when numerical values ​​such as the number, value, amount, range, etc. of components are mentioned, the present invention is not limited to those specific numbers unless they are particularly clearly stated as essential or are clearly limited to specific numbers in principle. Similarly, when the shape, direction, positional relationship, etc. of components are mentioned, the present invention is not limited to those shapes, directions, positional relationship, etc. unless they are particularly clearly stated as essential or are clearly limited to specific shapes, directions, positional relationship, etc. in principle.

[0046] The modified examples are not limited to the above examples. That is, for example, multiple embodiments may be applied in combination. In other words, a part of one embodiment may be combined with a part of another embodiment. There are no particular limitations on the number or manner in which multiple embodiments are combined. Furthermore, any one of the multiple embodiments and any one of the multiple modified examples may be combined with each other as long as there is no technical contradiction. Similarly, one of the multiple modified examples may be combined with another one of the multiple modified examples as long as there is no technical contradiction.

[0047] (Disclosure details) As is clear from the above description of the embodiments and modifications, this specification discloses at least the following matters. <Point 1> The MEMS transducer (1) a vibration section (32) formed in a flat plate shape having a thickness direction along a directivity axis (DA) and configured to flexibly vibrate in a manner in which the antinode of vibration moves along the directivity axis; a support portion (2) provided to fixedly support a fixed end portion (32a) that constitutes a vibration node of the vibration portion; Equipped with The vibration unit is extending from the fixed end toward the pointing axis, a stress adjustment layer (36) provided along an in-plane direction intersecting the orientation axis so as to be able to adjust variations in residual stress in the in-plane direction, The stress adjustment layer is provided on the outermost layer side in the thickness direction of the vibrating section, and is divided into a plurality of layers in the in-plane direction. <Point 2> In the first aspect, the stress adjustment layer is divided into a plurality of portions in the in-plane direction, and each portion is provided so as to be capable of individually adjusting stress. <Point 3> In the first and second aspects, the stress adjustment layer is divided into a plurality of parts in the direction from the fixed end toward the orientation axis. <Point 4> In terms of points 1 to 3, The stress adjustment layer is divided into a plurality of parts in the width direction, which is the in-plane direction, The width direction intersects with the extension direction, which is the in-plane direction from the fixed end toward the orientation axis. <Point 5> In a fourth aspect, the stress adjustment layer is provided so that compressive residual stress and tensile residual stress are generated alternately in the width direction. <Point 6> In aspect 2, the stress adjustment layer is divided into multiple parts in an extension direction, which is the in-plane direction from the fixed end toward the directional axis, and in a width direction, which is the in-plane direction intersecting the extension direction. <Point 7> In the first to sixth aspects, the stress adjustment layer has a configuration in which the residual stress can be adjusted by heat. <Point 8> In points 1 to 7, The vibration section has a configuration in which a piezoelectric layer (34), an electrode layer (35), and the stress adjustment layer are stacked in the thickness direction, The stress adjustment layer is made of a material whose stress can be varied at a lower temperature than the piezoelectric layer and the electrode layer. <Point 9> In an eighth aspect, the stress adjustment layer is made of a metal material having a lower melting point than the piezoelectric layer and the electrode layer. <Point 10> In a ninth aspect, the stress adjustment layer is amorphous. [Explanation of symbols]

[0048] 1 MEMS transducer 2 Support part 3 Piezoelectric element part 32 Vibration unit 32a Fixed end 32b Free end 34 Piezoelectric layer 35 Electrode layer 36 Stress adjustment layer DA directional axis

Claims

1. A MEMS transducer (1), comprising: a vibration section (32) formed in a flat plate shape having a thickness direction along a directivity axis (DA) and configured to flexibly vibrate in a manner in which an antinode of vibration moves along the directivity axis; a support portion (2) provided to fixedly support a fixed end portion (32a) that constitutes a vibration node of the vibration portion; Equipped with The vibration unit is extending from the fixed end toward the pointing axis, a stress adjustment layer (36) provided along an in-plane direction intersecting the orientation axis so as to be able to adjust variations in residual stress in the in-plane direction, The stress adjustment layer is provided on the outermost layer side in the thickness direction of the vibration section, and, The conductor is divided into a plurality of parts in a width direction, which is an in-plane direction intersecting with an extension direction, which is an in-plane direction from the fixed end portion toward the directional axis, and is provided so that compressive residual stress and tensile residual stress are generated alternately in the width direction. MEMS transducer.

2. The stress adjustment layer is divided into a plurality of portions in the in-plane direction, and each portion is provided so as to be capable of individually adjusting stress. The MEMS transducer of claim 1 .

3. The stress adjustment layer is divided into a plurality of parts in the extension direction. The MEMS transducer of claim 1 .

4. the stress adjustment layer has a configuration in which residual stress can be adjusted by heat; The MEMS transducer of claim 1 .

5. The vibration section has a configuration in which a piezoelectric layer (34), an electrode layer (35), and the stress adjustment layer are stacked in the thickness direction, the stress adjustment layer is formed of a material whose stress can be varied at a lower temperature than the piezoelectric layer and the electrode layer; The MEMS transducer of claim 1 .

6. the stress adjustment layer is formed of a metal material having a lower melting point than the piezoelectric layer and the electrode layer; The MEMS transducer of claim 5 .

7. the stress adjustment layer is amorphous; The MEMS transducer of claim 6 .

Images