Piezoelectric device

Abstract

Provided is a piezoelectric device having functional electrodes with high heat dissipation properties. This piezoelectric device comprises: a piezoelectric layer that has a thickness in a first direction and has a first main surface and a second main surface which is a surface on the reverse side from the first main surface; a support member that is provided on the second main surface side of the piezoelectric layer; a first functional electrode that is provided on the first main surface and / or the second main surface of the piezoelectric layer; a substrate member that faces the first main surface of the piezoelectric layer while being separated therefrom in the first direction, has a second functional electrode, and has a thickness in the first direction; and a shield that is provided between the piezoelectric layer and the substrate member. The shield is provided in a position at least partially overlapping the first functional electrode in plan view in the first direction. The distance from the center of the shield to the piezoelectric layer is smaller than the distance from the center of the shield to the substrate member.

Description

Piezoelectric Devices

[0001] The present invention relates to a piezoelectric device.

[0002] Patent Documents 1 and 2 disclose piezoelectric devices having two substrates facing each other at a distance from each other, with a shield provided between the two substrates to cover a functional electrode provided on one of the substrates.

[0003] JP 2005-252175 A JP 2018-014717 A

[0004] In the piezoelectric devices disclosed in Patent Documents 1 and 2, there is a possibility that the heat generated by the operation of the functional electrodes cannot be sufficiently dissipated.

[0005] The present invention has been made to solve the above-mentioned problems, and has an object to provide a piezoelectric device in which the heat dissipation properties of the functional electrodes are high.

[0006] A piezoelectric device according to one aspect of the present invention comprises: a piezoelectric layer having a thickness in a first direction and having a first main surface and a second main surface opposite the first main surface; a support member provided on the second main surface side of the piezoelectric layer; a first functional electrode provided on at least one of the first main surface and the second main surface of the piezoelectric layer; a substrate member facing the first main surface of the piezoelectric layer at a distance in the first direction, having a second functional electrode, and having a thickness in the first direction; and a shield provided between the piezoelectric layer and the substrate member, wherein the shield is provided at a position at least partially overlapping with the first functional electrode when viewed in a plane in the first direction, and the distance from the center of the shield to the piezoelectric layer is smaller than the distance from the center of the shield to the substrate member.

[0007] According to the present invention, a piezoelectric device having a functional electrode with high heat dissipation properties can be provided.

[0008] FIG. 1 is a schematic cross-sectional view showing an example of a piezoelectric device according to the first embodiment. FIG. 2 is a schematic plan view of the piezoelectric device according to the first embodiment, taken along line A-A in FIG. 1. FIG. 3 is a schematic plan view of the piezoelectric device according to the first embodiment, taken along line A-A in FIG. 1. FIG. 4 is a plan view showing a modified example of the piezoelectric device according to the first embodiment. FIG. 5 is a diagram illustrating a method for manufacturing the piezoelectric device according to the first embodiment. FIG. 6 is a diagram illustrating a method for manufacturing the piezoelectric device according to the first embodiment. FIG. 7 is a diagram illustrating a manufacturing process for the piezoelectric device according to the first embodiment. FIG. 8 is a schematic cross-sectional view showing an example of a piezoelectric device according to a second embodiment. FIG. 9 is a schematic cross-sectional view showing an example of a piezoelectric device according to a third embodiment.

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. However, the present disclosure is not limited to these embodiments. Note that each embodiment described in the present disclosure is an example, and in the second and subsequent embodiments, a description of modifications in which partial substitution or combination of configurations is possible between different embodiments, and of matters common to the first embodiment will be omitted, and only the differences will be described. In particular, similar effects resulting from similar configurations will not be mentioned in each embodiment.

[0010] 1 is a schematic cross-sectional view showing an example of a piezoelectric device according to a first embodiment. The piezoelectric device 1 according to the first embodiment includes a first element 100, a second element 200, a shield 310, and a sealing material 320. In the following description, the thickness direction of the first element 100 and the second element 200 is referred to as the Z direction, the direction perpendicular to the Z direction is referred to as the X direction, and the direction perpendicular to the Z direction and the Y direction is referred to as the Y direction. The first element 100 and the second element 200 face each other and are spaced apart in the Z direction.

[0011] Fig. 2 is a schematic plan view of the piezoelectric device according to the first embodiment, seen from a cross section taken along line A-A in Fig. 1. More specifically, Fig. 2 is a plan view of the first element 100, seen from the Z direction. The first element 100 is a piezoelectric element that utilizes bulk waves, i.e., a BAW (Bulk Acoustic Wave) element. As shown in Figs. 1 and 2, the first element 100 includes a support member 110, a piezoelectric layer 120, a first functional electrode 130, wiring electrodes 133 and 134, and through electrodes 141 to 143.

[0012] The piezoelectric layer 120 is a flat layer having a first main surface 120a and a second main surface 120b opposite to the first main surface 120a. The first main surface 120a faces the second element 200 in the Z direction. In the first embodiment, the piezoelectric layer 120 is made of lithium niobate (LiNbO ３ ), lithium tantalate (LiTaO ３ ), and the substrate is made of a single crystal such as quartz that can excite bulk waves.

[0013] 2, a through hole 121 is provided in the piezoelectric layer 120. The through hole 121 is a hole that penetrates the piezoelectric layer 120 in the Z direction. When viewed from above in the Z direction, the through hole 121 is provided at a position that overlaps with a space portion 113, which will be described later. Note that the through hole 121 is not limited to the example in FIG. 2 as long as it is provided at a position that overlaps with the space portion 113, and may, for example, also penetrate an upper electrode 131 and a lower electrode 132, which will be described later.

[0014] The first functional electrode 130 has an upper electrode 131 and a lower electrode 132. As shown in FIG. 1 , the upper electrode 131 is provided on the first main surface 120a of the piezoelectric layer 120, and the lower electrode 132 is provided on the second main surface 120b of the piezoelectric layer 120. The upper electrode 131 has a circular main electrode portion 131a and an extension portion 131b extending from the main electrode portion 131a in the X direction. Similarly, the lower electrode 132 has a circular main electrode portion 132a and an extension portion 132b extending from the main electrode portion 132a in the X direction. The upper electrode 131 and the lower electrode 132 are made of a metal or alloy such as aluminum (Al), platinum (Pt), copper (Cu), tungsten (W), or molybdenum (Mo). The upper electrode 131 and the lower electrode 132 may have an adhesive layer made of titanium (Ti), a nickel-chromium alloy (NiCr), or the like.

[0015] In the first embodiment, the circular main electrode portion 131a of the upper electrode 131 and the circular main electrode portion 132a of the lower electrode 132 overlap each other in a planar view in the Z direction. In other words, the piezoelectric layer 120 is sandwiched between the circular main electrode portion 131a of the upper electrode 131 and the circular main electrode portion 132a of the lower electrode 132. As a result, bulk waves are propagated in the region between the circular main electrode portion 131a of the upper electrode 131 and the circular main electrode portion 132a of the lower electrode 132. Note that the shapes of the upper electrode 131 and the lower electrode 132 are merely examples and are not limited thereto. In the following description, the region where the upper electrode 131 and the lower electrode 132 overlap each other in a planar view in the Z direction may be described as the excitation region of the first functional electrode 130.

[0016] 2, a wiring electrode 133 of the upper electrode is provided in the Z direction of the extension portion 131b. The wiring electrode 133 of the upper electrode is provided on the first main surface 120a side of the piezoelectric layer 120. The wiring electrode 133 of the upper electrode is made of a metal or alloy such as aluminum (Al), platinum (Pt), copper (Cu), tungsten (W), or molybdenum (Mo). The wiring electrode 133 of the upper electrode may have an adhesion layer made of titanium (Ti), a nickel-chromium alloy (NiCr), or the like.

[0017] 2, a wiring electrode 134 of the lower electrode is provided in the Z direction of the extension portion 132b. The wiring electrode 134 of the lower electrode is provided on the second main surface 120b side of the piezoelectric layer 120. The lower electrode 132 and the wiring electrode 134 of the upper electrode are made of a metal or alloy containing Al, Pt, Cu, W, Mo, or the like. The lower electrode 132 and the wiring electrode 134 of the upper electrode may have an adhesion layer made of Ti, NiCr, or the like.

[0018] The support member 110 is provided facing the second main surface 120b of the piezoelectric layer 120. In the first embodiment, the support member 110 includes a support substrate 111 and an intermediate layer 112. The support substrate 111 is a substrate made of silicon (Si), quartz, or the like. The intermediate layer 112 is a layer made of silicon oxide, or the like. The intermediate layer 112 is provided on the piezoelectric layer 120 side of the support substrate 111. Note that the support member 110 does not necessarily have to include the intermediate layer 112, and the support substrate 111 may be provided so as to be in contact with the second main surface 120b side of the piezoelectric layer 120.

[0019] The support member 110 has a space 113. In the example of FIG. 2, the space 113 is a space inside a recess provided on the piezoelectric layer 120 side of the intermediate layer 112. The space 113 is provided so as to overlap with the excitation region of the first functional electrode 130 in a plan view in the Z direction. This makes it possible to suppress leakage of bulk wave energy. Note that the space 113 is not limited to the example of FIG. 1, and may penetrate the intermediate layer 112 or may be provided on the piezoelectric layer 120 side of the support substrate 111. In addition, in the example of FIG. 2, the shape of the outer wall of the space 113 is rectangular, but this is merely an example and is not limited thereto, and may be other shapes, such as circular.

[0020] The through electrodes 141 and 142 are extraction electrodes of the first element 100 and are made of a conductor such as copper (Cu). The through electrode 141 is electrically connected to the upper electrode 131 via the wiring electrode 133. Similarly, the through electrode 142 is electrically connected to the lower electrode 132 via the wiring electrode 134. The through electrode 141 penetrates the support member 110 and the piezoelectric layer 120 in the Z direction. The through electrode 142 penetrates the support member 110 in the Z direction. This allows the first element 100 to be connected to an external element by providing bumps on the ends of the through electrodes 141 and 142 that are not connected to the upper electrode 131 or the lower electrode 132. Note that when multiple resonators are connected in series or in parallel, one through electrode per resonator may be connected to a functional electrode, or no through electrodes may be connected.

[0021] The through electrode 143 is an extraction electrode of the sealing material 320, which will be described later, and is made of a conductor such as copper (Cu). The through electrode 143 is electrically connected to the sealing material 320. The through electrode 143 penetrates the support member 110 and the piezoelectric layer 120 in the Z direction. This allows the through electrode 143 to be grounded by providing a bump on the end of the through electrode 143 that is not connected to the sealing material 320. Note that in the example of FIG. 2, a plurality of through electrodes 143 are provided spaced apart at positions overlapping the second portion 322 of the sealing material 320, but this is merely an example and is not limiting. Furthermore, if the sealing material 320 is made of an insulator, the through electrode 143 may not be provided.

[0022] It should be noted that the through electrodes provided in the first element 100 are not limited to the above-described through electrodes 141 to 143. For example, a through electrode electrically connected to a second functional electrode 230 (described later) may be further provided.

[0023] Fig. 3 is a schematic plan view of the piezoelectric device according to the first embodiment, seen from a cross section taken along line A-A in Fig. 1. More specifically, Fig. 3 is a plan view of the second element 200, seen from the Z direction. The second element 200 is a SAW (Surface Acoustic Wave) element having an IDT (Interdigital Transducer) electrode. As shown in Figs. 1 and 3, the second element 200 includes a substrate member 210, a second functional electrode 230, and a through electrode 241.

[0024] The substrate member 210 is provided to face the piezoelectric layer 213 at a distance in the Z direction. The substrate member 210 according to the first embodiment has a support substrate 211, an intermediate layer 212, and the piezoelectric layer 213.

[0025] The support substrate 211 is a substrate made of silicon (Si), quartz crystal, or the like.

[0026] The intermediate layer 212 is a layer made of silicon oxide or the like. The intermediate layer 212 is provided on the piezoelectric layer 213 side of the support substrate 211. Note that the intermediate layer 212 is not an essential component.

[0027] The piezoelectric layer 213 is made of lithium niobate (LiNbO ３ ), lithium tantalate (LiTaO ３ The piezoelectric layer 213 is a flat layer made of a single crystal, such as quartz, that can excite bulk waves. The piezoelectric layer 213 is provided on the side of the intermediate layer 212 opposite the support substrate 211. The piezoelectric layer 213 has a first main surface 213a and a second main surface 213b opposite the first main surface 213a. The first main surface 213a faces the first element 100 in the Z direction.

[0028] The second functional electrode 230 is a comb-shaped electrode. The second functional electrode 230 is made of a metal or alloy such as aluminum (Al), platinum (Pt), copper (Cu), tungsten (W), or molybdenum (Mo). The second functional electrode 230 may have an adhesion layer made of titanium (Ti), a nickel-chromium alloy (NiCr), or the like.

[0029] The second functional electrode 230 is a pair of comb-shaped electrodes connected to different potentials. As shown in FIG. 3 , the second functional electrode 230 includes first electrode fingers 231, second electrode fingers 232, a first bus bar 233, and a second bus bar 234. The first electrode fingers 231 extend in the X direction, and one end in the X direction is connected to the first bus bar 233. The first bus bar 233 extends in the Y direction. The second electrode fingers 232 extend in the X direction, and one end in the X direction is connected to the second bus bar 234. The second bus bar 234 extends in the Y direction. In the first embodiment, the first electrode fingers 231 and the first bus bar 233 are connected to a hot potential via one of the through electrodes 241, and the second electrode fingers 232 and the second bus bar 234 are connected to a ground potential via the other through electrode 241. As a result, a resonator is formed by the second functional electrode 230 and the substrate member 210.

[0030] The first electrode finger 231 and the second electrode finger 232 have a rectangular shape and a length direction. The first electrode finger 231 and the second electrode finger 232 adjacent to the first electrode finger 231 face each other in a direction perpendicular to the length direction. The length direction of the first electrode finger 231 and the second electrode finger 232 and the direction perpendicular to the length direction of the first electrode finger 231 and the second electrode finger 232 are directions that intersect with the thickness direction of the piezoelectric layer 213. Therefore, it can be said that the first electrode finger 231 and the second electrode finger 232 adjacent to the first electrode finger 231 face each other in a direction that intersects with the thickness direction of the piezoelectric layer 213.

[0031] In the following description, the region where adjacent first electrode fingers 231 and second electrode fingers 232 overlap when viewed in the opposing direction will be described as the excitation region of the second functional electrode 230. Here, "the first electrode fingers 231 and the second electrode fingers 232 are adjacent" does not mean that the first electrode fingers 231 and the second electrode fingers 232 are arranged in direct contact with each other, but rather that the first electrode fingers 231 and the second electrode fingers 232 are arranged with a gap therebetween. Furthermore, when the first electrode fingers 231 and the second electrode fingers 232 are adjacent to each other, no electrodes connected to hot electrodes or ground electrodes, including other first electrode fingers 231 and second electrode fingers 232, are arranged between the first electrode fingers 231 and the second electrode fingers 232. The number of pairs does not need to be an integer number of pairs and may be 1.5 pairs, 2.5 pairs, or the like.

[0032] 3 , the Y-direction end of the second bus bar 234 is electrically connected to the second portion 322 of the sealing material 320. As a result, the second bus bar 234 is connected to the reference potential. Note that the second bus bar 234 does not have to be connected to the second portion 322. Alternatively, the first bus bar 233 may be connected to the second portion 322.

[0033] The shield 310 is a plate-shaped member that blocks electromagnetic waves. The shield 310 is provided between the piezoelectric layer 120 and the piezoelectric layer 213. In the first embodiment, the shield 310 is provided at a distance between the excitation region of the first functional electrode 130 and the excitation region of the second functional electrode 230 in a plan view in the first direction. This makes it possible to prevent electromagnetic waves generated by the operation of one of the first functional electrode 130 and the second functional electrode 230 from affecting the operation of the other functional electrode.

[0034] The through electrode 241 is an extraction electrode of the second element 200 and is made of a conductor such as copper (Cu). The through electrode 241 is electrically connected to the second functional electrode 230. In the example of FIG. 1 , one through electrode 241 is connected to each of the first bus bar 233 and the second bus bar 234. The through electrode 241 penetrates the support substrate 211, the intermediate layer 212, and the piezoelectric layer 213 in the Z direction. This allows the second element 200 to be connected to an external element by providing a bump on the end of the through electrode 241 on the side not connected to the second functional electrode 230. Note that when multiple resonators are connected in series or in parallel, one through electrode per resonator may be connected to a functional electrode, or no through electrode may be connected.

[0035] The distance from the center C of the shield 310 to the piezoelectric layer 120 is shorter than the distance from the center C of the shield 310 to the substrate member 210 of the second element 200. Here, the center C of the shield 310 refers to a position overlapping with the geometric center of the excitation region of the first functional electrode 130 in a planar view in the Z direction. In the example of FIG. 2 , the geometric center of the excitation region of the first functional electrode 130 refers to the center of the circle of the main electrode portions 131a and 132a. Furthermore, if the shape of the main electrode portions is rectangular in a planar view in the Z direction, the geometric center of the excitation region of the first functional electrode refers to the intersection of the diagonals of the rectangle of the main electrode portions. Furthermore, the distance from the center C of the shield 310 to the piezoelectric layer 120 refers to the distance in the Z direction from the surface of the center C of the shield 310 facing the piezoelectric layer 120 to the first main surface 120a of the piezoelectric layer 120. Furthermore, the distance from the center C of the shield 310 to the substrate member 210 of the second element 200 refers to the distance in the Z direction from the surface of the shield 310 at the center C facing the second element 200 to the main surface (first main surface 213a) of the substrate member 210 of the second element 200 facing the first element. This facilitates conduction of operating heat from the first functional electrode 130 to the shield 310, thereby improving the heat dissipation of the first functional electrode 130 even when the space 113 is provided. Here, the distance from the center C of the shield 310 to the piezoelectric layer 120 and the distance from the center C of the shield 310 to the substrate member 210 of the second element 200 can be measured, for example, by observing a cross section of the piezoelectric device 1 along the Z direction with a scanning electron microscope (SEM).

[0036] The shield 310 is made of a conductor. This allows the shield 310 to block electromagnetic waves. The shield 310 is preferably made of a metal with high thermal conductivity, such as aluminum (Al), copper (Cu), gold (Au), or silver (Ag). This allows the heat dissipation of the first functional electrode 130 to be improved.

[0037] In the first embodiment, the shield 310 is electrically connected to ground. In the example of FIG. 1 , one end of the shield 310 in the X direction is provided on the first main surface 213 a of the piezoelectric layer 213, and the other end of the shield 310 in the X direction is provided on the Z direction side of the second bus bar 234 of the second functional electrode 230, which is connected to ground. However, this is merely an example and is not limiting. For example, one end of the shield 310 in the X direction may be provided on the first main surface 120 a of the piezoelectric layer 120 of the first element 100, and the other end of the shield 310 in the X direction may not be provided on the second functional electrode 230.

[0038] In the first embodiment, the shield 310 has an arched shape that is curved convexly toward the first main surface 120a of the piezoelectric layer 120 when viewed in a plan view from the X direction. This shape can improve the strength of the shield 310. In the example of FIG. 1 , the shield 310 has a flat shape near the center C. In other words, the shield 310 is provided so as to cover the second functional electrode 230. In addition, a space 311 is present between the shield 310 and the first main surface 213a of the piezoelectric layer 213.

[0039] In the first embodiment, the shield 310 is flat in the Y direction. That is, the space 311 between the shield 310 and the first main surface 213 a of the piezoelectric layer 213 has an open end in the Y direction, and communicates with the space 330 between the piezoelectric layer 120 and the substrate member 210 of the second element 200.

[0040] In the example of FIG. 3, the shield 310 has a rectangular shape with a missing vertex when viewed in a plan view in the Z direction, but this is merely an example and is not limiting.

[0041] The sealing material 320 seals the space between the piezoelectric layer 120 and the substrate member 210. In the first embodiment, the sealing material 320 is a frame-shaped member, and surrounds the first functional electrode 130 and the second functional electrode 230 in plan view in the Z direction. This makes the space 330 surrounded by the piezoelectric layer 120, the substrate member 210, and the sealing material 320 a closed space.

[0042] In the first embodiment, the space 330 is airtight. The pressure within the space 330 is higher than atmospheric pressure. Here, atmospheric pressure refers to the pressure under standard conditions, which is 101,325 Pa. This promotes heat dissipation through convection, thereby improving the heat dissipation effect within the space 330. The space 330 is preferably filled with an inert gas atmosphere made of a light element such as helium (He). This can further improve the heat dissipation effect of the first functional electrode 130 while suppressing deterioration of the excitation characteristics of the first functional electrode 130.

[0043] In the first embodiment, the sealing material 320 has a first portion 321, a second portion 322, and a bonding portion 323. The first portion 321 is provided on the first main surface 120a of the piezoelectric layer 120. The second portion 322 is provided on the first main surface 213a of the piezoelectric layer 213 at a position overlapping the first portion 321 in a planar view in the Z direction. The bonding portion 323 is provided between the first portion 321 and the second portion 322 in the Z direction and bonds the first portion 321 and the second portion 322 together. The sealing material 320 is made of, for example, a metal, an insulator, or the like. More specifically, the first portion 321 and the second portion 322 are made of, for example, aluminum (Al), and the bonding portion 323 is made of, for example, gold (Au).

[0044] The piezoelectric device according to the first embodiment is not limited to the above-described one.

[0045] FIG. 4 is a plan view showing a modified example of the piezoelectric device according to the first embodiment. More specifically, FIG. 4 is a plan view showing a second element 200A according to a modified example of the piezoelectric device according to the first embodiment. As shown in FIG. 4 , the shield 310 may overlap multiple resonators provided in the second element. In the example of FIG. 4 , two resonators adjacent in the X direction are formed by the second functional electrode 230A and the substrate member 210, but this is merely an example. For example, the shield 310 may overlap three or more resonators, or may overlap two or more resonators adjacent in the Y direction. In addition, in the example of FIG. 4 , the bus bars on the X-direction outer sides of the two resonators are electrically connected to ground by connecting the Y-direction to the second portion 322 of the sealing material 320, but this is merely an example. In addition, in the example of FIG. 4 , the X-direction end of the shield 310 contacts the Z-direction of the bus bars on the X-direction outer sides of the two resonators, but this is merely an example, and it is sufficient that the shield 310 is electrically connected to ground potential.

[0046] Although the above description has been given using an example in which the first element is a BAW element and the second element is a SAW element, the combination of the first element and the second element is not limited to this. That is, the first element may be another device using a ferroelectric, and the second element may be an element that does not use a piezoelectric material. For example, the first element may be a BAW element, a SAW element, or a MEMS (Micro Electro Mechanical Systems) high-frequency element, and the second element may be an LSI (Large Scale Integration). In this case, providing the shield 310 can prevent the parasitic capacitance of the first element using a ferroelectric from affecting the second element that does not use a ferroelectric.

[0047] The shield may also overlap multiple resonators provided in the first element. In this case, the center of the shield refers to the geometric center of the excitation region of each resonator when viewed in a plane in the Z direction. That is, the shield may have multiple centers. In this case, the distance from the center of each of the multiple shields to the piezoelectric layer is shorter than the distance from the center of each of the shields to the substrate member 210 of the second element. Here, the excitation region of the resonator refers to the region where the functional electrodes overlap when viewed in a plane in the Z direction if the resonator is a BAW or MEMS high-frequency element, and refers to the region where the comb-teeth portions of the IDT electrodes overlap when viewed in a direction in which they face each other when the resonator is a SAW including an IDT electrode.

[0048] As described above, the piezoelectric device according to the first embodiment includes the piezoelectric layer 120 having a thickness in a first direction and a first main surface 120a and a second main surface 120b opposite the first main surface 120a, the support member 110 provided on the second main surface 120b side of the piezoelectric layer 120, the first functional electrode 130 provided on either the first main surface 120a or the second main surface 120b of the piezoelectric layer 120, the substrate member 210 facing the first main surface 120a of the piezoelectric layer 120 at a distance in the first direction, having the second functional electrode 230, and the shield 310 provided between the piezoelectric layer 120 and the substrate member 210. The shield 310 is provided at a position at least partially overlapping with the first functional electrode 130 in a planar view in the first direction. The distance from the center C of the shield 310 to the piezoelectric layer 120 is shorter than the distance from the center C of the shield 310 to the substrate member 210. This allows the operating heat of the first functional electrode 130 to be easily conducted to the shield 310, thereby improving the heat dissipation properties of the first functional electrode 130.

[0049] In a desirable aspect, the support member 110 has the space 113 in a position where, in plan view in the first direction, the support member 110 at least partially overlaps with the first functional electrode 130. Even in this case, it is possible to improve the excitation characteristics of the first functional electrode 130 while suppressing a decrease in the heat dissipation performance of the first functional electrode 130.

[0050] In a preferred aspect, the shield 310 is provided at a position where, in plan view in the first direction, it at least partially overlaps with the second functional electrode 230. This makes it possible to prevent electromagnetic waves generated by the operation of the first functional electrode 130 from affecting the operation of the second functional electrode 230.

[0051] In a preferred embodiment, the piezoelectric element further includes a sealing material 320 provided between the piezoelectric layer 120 and the substrate member 210. The first functional electrode 130 is provided in an area surrounded by the sealing material 320 in a plan view in the first direction. A space 330 surrounded by the piezoelectric layer 120, the substrate member 210, and the sealing material 320 is airtight. The pressure within the space 330 is greater than atmospheric pressure. This promotes heat dissipation by thermal convection, thereby further improving heat dissipation performance.

[0052] Next, a method for manufacturing the piezoelectric device according to this embodiment will be described. Figures 5 to 7 are views illustrating the manufacturing process of the piezoelectric device according to the first embodiment. The method for manufacturing the piezoelectric device according to this embodiment includes the steps of forming the first element 100 (steps ST11 to ST19), forming the second element 200 (steps ST21 to ST28), and bonding the first element 100 and the second element 200 together (step ST30).

[0053] 5A to 5C are diagrams illustrating the steps of manufacturing the first element 100. The steps of forming the first element 100 (steps ST11 to ST19) will be described below with reference to FIG.

[0054] 5, a lower electrode 132 and a wiring electrode 134 are formed on the second main surface 120b of the piezoelectric layer 120 (step ST11). The lower electrode 132 and the wiring electrode 134 are formed by, for example, a vapor deposition lift-off method. That is, in step ST11, a resist pattern is formed on the second main surface 120b of the piezoelectric layer 120 by photolithography, and metal is vapor-deposited. The resist is then removed, and the remaining metal film forms the lower electrode 132 and the wiring electrode 134.

[0055] Next, a sacrificial layer 113S is formed on the second main surface 120b of the piezoelectric layer 120 (step ST12). The sacrificial layer 113S is provided in a region where the space 113 of the support member 110 (intermediate layer 112) is to be formed. In other words, the sacrificial layer 113S is provided so as to cover the main electrode portion 132a of the lower electrode 132. The sacrificial layer 113S is formed by sputtering using a material such as zinc oxide (ZnO).

[0056] Next, the intermediate layer 112 is formed on the second main surface 120b of the piezoelectric layer 120, covering the lower electrode 132 and the sacrificial layer 113S (step ST13). The intermediate layer 112 is formed by sputtering using a material such as silicon oxide. An adhesion layer made of Ti, NiCr, or the like may be provided between the lower electrode 132 and the intermediate layer 112. Furthermore, the surface of the intermediate layer 112 opposite the piezoelectric layer 120 may be planarized by chemical-mechanical polishing (CMP) as necessary.

[0057] Next, the support substrate 111 is bonded to the second main surface 120b of the piezoelectric layer 120. This bonds the support substrate 111 to the piezoelectric layer 120 (step ST14). The support substrate 111 is bonded to the piezoelectric layer 120 by direct bonding, plasma activated bonding, atomic diffusion bonding, or the like.

[0058] Next, the piezoelectric layer 120 is ground and polished to thin it (step ST15). The piezoelectric layer 120 is polished, for example, by mechanical polishing or CMP. As a result, the thickness of the piezoelectric layer 120 is reduced to approximately 1 μm or less. In step ST15, the method for thinning the piezoelectric layer 120 is not limited to polishing. For example, the piezoelectric layer 120 may be thinned by forming a damaged layer inside the piezoelectric layer 120 by ion implantation, and then peeling off a layer on the first principal surface of the damaged layer.

[0059] Next, an upper electrode 131 and a wiring electrode 133 are formed on the first main surface 120a of the piezoelectric layer 120 (step ST16). The upper electrode 131 and the wiring electrode 133 are formed, for example, by a vapor deposition lift-off method, similar to the above-described lower electrode 132. That is, in step ST16, a resist pattern is formed on the first main surface 120a of the piezoelectric layer 120 by photolithography, and metal is vapor-deposited. The resist is then removed, and the remaining metal film forms the upper electrode 131 and the wiring electrode 133.

[0060] Next, the sacrificial layer 113S is removed to form the space 113 in the intermediate layer 112 (step ST17). The sacrificial layer 113S is removed by wet etching. In this case, an etchant that dissolves the sacrificial layer 113S is injected through the through-holes 121 formed in the piezoelectric layer 120 by a method such as RIE.

[0061] Next, through electrodes 141 to 143 are formed so as to penetrate the support member 110 (step ST18). In the first embodiment, a plurality of holes are formed so as to penetrate in the Z direction from the main surface of the support member 110 opposite the piezoelectric layer 120 to the upper electrode 131, the wiring electrode 134, and the first main surface 120a, and the formed holes are filled by filling plating to form the through electrodes 141 to 143. In the first embodiment, the holes in which the through electrodes 141 to 143 are provided are formed by DRIE (Deep RIE).

[0062] Then, the first portion 321 of the sealing material 320 and the bonding portion 323 are formed on the first main surface 120a of the piezoelectric layer 120 (step ST19). The first portion 321 of the sealing material 320 and the bonding portion 323 are formed by a vapor deposition lift-off method. That is, in step ST19, a resist pattern is formed on the first main surface 120a of the piezoelectric layer 120 by photolithography, and metal is vapor-deposited. The resist is then removed, and the remaining metal film forms the first portion 321 and the bonding portion 323.

[0063] The first element 100 of this embodiment can be manufactured through the above steps. Note that the steps shown in Fig. 5 are merely schematic and can be modified as appropriate.

[0064] 6A to 6C are diagrams illustrating the steps of forming the second element 200. The steps of forming the second element 200 (steps ST21 to ST28) will be described below with reference to FIG.

[0065] 6, an intermediate layer 212 is formed on the second main surface 213b of the piezoelectric layer 213 (step ST21). The intermediate layer 212 is formed by sputtering using a material such as silicon oxide. The surface of the intermediate layer 212 opposite to the piezoelectric layer 213 may be planarized by CMP, if necessary.

[0066] Next, the support substrate 211 is bonded to the second main surface 213b of the piezoelectric layer 213. This bonds the support substrate 211 to the piezoelectric layer 213 (step ST22). The support substrate 211 is bonded to the piezoelectric layer 213 by direct bonding, plasma activated bonding, atomic diffusion bonding, or the like.

[0067] Next, the piezoelectric layer 213 is ground and polished to thin the piezoelectric layer 213 (step ST23). The piezoelectric layer 213 is polished, for example, by mechanical polishing or CMP. As a result, the thickness of the piezoelectric layer 213 is reduced to approximately 1 μm or less. In step ST23, the method for thinning the piezoelectric layer 213 is not limited to polishing. For example, the piezoelectric layer 213 may be thinned by forming a damaged layer inside the piezoelectric layer 213 by ion implantation and peeling off a layer on the first principal surface of the formed damaged layer.

[0068] Next, the second functional electrode 230 is formed on the first main surface 213a of the piezoelectric layer 213 (step ST24). The second functional electrode 230 is formed by, for example, a vapor deposition lift-off method. That is, in step ST24, a resist pattern is formed on the first main surface 213a of the piezoelectric layer 213 by photolithography, and metal is vapor-deposited. The resist is then removed, and the metal film in the remaining portion forms the second functional electrode 230.

[0069] Next, the through electrodes 241 are formed so as to penetrate the substrate member 210 (step ST29). In the first embodiment, a plurality of holes are formed so as to penetrate in the Z direction from the main surface of the substrate member 210 opposite the piezoelectric layer 213 to the second functional electrode 230, and the formed holes are filled by filling plating to form the through electrodes 241. In the first embodiment, the holes in which the through electrodes 241 are provided are formed by DRIE.

[0070] Next, a sacrificial layer 311S is formed on the first main surface 213a of the piezoelectric layer 213 (step ST25). The sacrificial layer 311S is provided in a region where the space 311 is to be formed within the shield 310. In other words, the sacrificial layer 311S is provided so as to cover a part of the second functional electrode 230. The sacrificial layer 311S is formed by sputtering using a material such as zinc oxide (ZnO).

[0071] Next, the shield 310 is formed so as to cover the sacrificial layer 311S (step ST26). The shield 310 is formed, for example, by a vapor deposition lift-off method. That is, in step ST26, a resist pattern is formed on the first main surface 213a of the piezoelectric layer 213 by photolithography, and metal is vapor-deposited. The resist is then removed, and the metal film in the remaining portion forms the shield 310. Note that an adhesive layer of Ti, NiCr, or the like may be provided between the shield 310 and the sacrificial layer 311S.

[0072] Next, the sacrificial layer 311S is removed to form the space 311 within the shield 310 (step ST27). The sacrificial layer 311S is removed by wet etching. In this case, an etchant that dissolves the sacrificial layer 311S is injected from between the Y-direction end of the shield 310 and the first main surface 213a of the piezoelectric layer 213.

[0073] Then, the second portion 322 and the bonding portion 323 of the sealing material 320 are formed on the first main surface 213a of the piezoelectric layer 213 (step ST28). The second portion 322 and the bonding portion 323 of the sealing material 320 are formed by a vapor deposition lift-off method. That is, in step ST28, a resist pattern is formed on the first main surface 213a of the piezoelectric layer 213 by photolithography, and metal is vapor-deposited. The resist is then removed, and the remaining metal film forms the second portion 322 and the bonding portion 323.

[0074] The second element 200 of this embodiment can be manufactured through the above steps. Note that the steps shown in FIG. 6 are merely schematic and can be modified as appropriate. For example, the step of forming the through electrode 241 (step ST29) may be performed after the step of forming the shield 310 (step ST26).

[0075] FIG. 7 is a diagram illustrating the process of bonding the first element 100 and the second element 200. After the first element 100 and the second element 200 are manufactured through the above process, the first element 100 and the second element 200 are bonded together as shown in FIG. 7 (step ST30). The first element 100 and the second element 200 are bonded together by metal bonding, for example, by Au-Au bonding, at the bonding portions 323. In the first embodiment, step ST30 is performed in an inert gas atmosphere with a pressure higher than atmospheric pressure. This allows the pressure in the space 330 between the first element 100 and the second element 200 to be higher than atmospheric pressure. Note that when the sealing material 320 is made of an insulator, the first and second portions of the sealing frame are bonded together by, for example, plasma activated bonding.

[0076] The piezoelectric device 1 of this embodiment can be manufactured through the above steps. Note that the steps shown in Fig. 7 are merely schematic and can be modified as appropriate.

[0077] As described above, the method for manufacturing the piezoelectric device according to the first embodiment includes the steps of forming the first functional electrode 130 on at least one of the first main surface 120a and the second main surface 120b, which are the other surfaces in the first direction of the piezoelectric layer 120 (steps ST11 and ST16), joining the support member 110 to the second main surface 120b, which is one surface in the first direction of the piezoelectric layer 120 (step ST13), grinding and thinning a portion of the piezoelectric layer 120, which has a thickness in the first direction (step ST15), providing the shield 310 between the piezoelectric layer 120 and the substrate member 210 (step ST26), and providing the substrate member 210, which has a thickness in the first direction, so as to face the first main surface 120a of the piezoelectric layer 120 and be spaced apart in the first direction (step ST30). The shield 310 is provided at a position that at least partially overlaps with the first functional electrode 130 in a planar view in the first direction. The distance from the center C of the shield 310 to the piezoelectric layer 120 is smaller than the distance from the center C of the shield 310 to the substrate member 210. This makes it easier for the operating heat of the first functional electrode 130 to be conducted to the shield 310, thereby improving the heat dissipation properties of the first functional electrode 130.

[0078] In a preferred embodiment, the method further includes a step (step ST24) of providing the second functional electrode 230 on the substrate member 210. The shield 310 is provided at a position where it at least partially overlaps with the second functional electrode 230 in a plan view in the first direction. This makes it possible to prevent electromagnetic waves generated by the operation of the first functional electrode 130 from affecting the operation of the second functional electrode 230.

[0079] In a preferred embodiment, the method further includes steps of providing a sealant 320 between the piezoelectric layer 120 and the substrate member 210 (steps ST19 and ST28). In the steps of providing the sealant 320 (steps ST19 and ST28), the sealant 320 is provided so as to surround the first functional electrode 130 in a planar view in the first direction. In the step of providing the substrate member 210 (step ST30), the substrate member 210 is bonded to the piezoelectric layer 120 via the sealant 320 so that the space surrounded by the piezoelectric layer 120, the substrate member 210, and the sealant 320 is airtight. The step of providing the substrate member 210 (step ST30) is performed in an atmosphere with a pressure higher than atmospheric pressure. This allows the pressure in the space 330 to be higher than atmospheric pressure, promoting heat dissipation by thermal convection and further improving heat dissipation.

[0080] 8 is a schematic cross-sectional view showing an example of a piezoelectric device according to a second embodiment. As shown in Fig. 8, the piezoelectric device 1A according to the second embodiment differs from the first embodiment in that the distance from the shield 310A to the piezoelectric layer 120 is different between the center C of the shield 310A and a position other than the center C of the shield 310A.

[0081] 8 , in the second embodiment, the distance from the center of the shield 310A to the piezoelectric layer 120 is shorter than the distance from any position other than the center C of the shield 310A to the piezoelectric layer 120. That is, the distance between the shield 310A and the first main surface 120a of the piezoelectric layer 120 is smallest at the center C. This can further improve the heat dissipation performance of the first functional electrode 130.

[0082] As described above, in the piezoelectric device according to the second embodiment, the distance from the shield 310A to the piezoelectric layer 120 is different between the center C of the shield 310A and positions other than the center C of the shield 310A. The distance from the center of the shield 310A to the piezoelectric layer 120 is shorter than the distance from positions other than the center C of the shield 310A to the piezoelectric layer 120. This improves heat dissipation at the geometric center of the excitation region of the first functional electrode 130, where a large amount of operating heat is generated.

[0083] 9 is a schematic cross-sectional view showing an example of a piezoelectric device according to a third embodiment. As shown in FIG. 9, the piezoelectric device 1B according to the third embodiment differs from the first embodiment in that a coating layer 312 is provided on the surface of the shield 310.

[0084] The covering layer 312 is a layer that covers the shield 310. In the example of FIG. 9 , the covering layer 312 covers both sides of the shield 310 in the Z direction. The covering layer 312 is made of a material that has lower electrical conductivity than the shield 310 and higher thermal conductivity and / or emissivity (radiation rate) than the shield 310. Here, the material of the covering layer 312 does not have to be a material that blocks electromagnetic waves. In the third embodiment, since the shield 310 is made of a metal such as Al, Cu, Au, or Ag, the covering layer 312 is made of a carbon material such as graphene, iron (Fe), or the like. This can improve the heat dissipation properties of the first functional electrode 130.

[0085] As described above, the piezoelectric device 1B according to the third embodiment further includes the coating layer 312 provided on the surface of the shield 310. The coating layer 312 has lower electrical conductivity and higher thermal conductivity than the shield 310. This can further improve the heat dissipation properties of the first functional electrode 130.

[0086] Furthermore, the piezoelectric device 1B according to the third embodiment further includes a coating layer 312 provided on the surface of the shield 310. The coating layer 312 has lower conductivity and higher emissivity than the shield 310. This can further improve the heat dissipation properties of the first functional electrode 130.

[0087] The above-described embodiments are provided to facilitate understanding of the present invention and are not intended to limit the present invention. The present invention may be modified or improved without departing from the spirit and scope of the present invention, and equivalents thereof are also included in the present invention.

[0088] The present disclosure may also have the following configurations.

[0089] (1) A piezoelectric device comprising: a piezoelectric layer having a thickness in a first direction and having a first main surface and a second main surface opposite to the first main surface; a support member provided on the second main surface side of the piezoelectric layer; a first functional electrode provided on at least one of the first and second main surfaces of the piezoelectric layer; a substrate member facing the first main surface of the piezoelectric layer at a distance in the first direction, the substrate member having a second functional electrode and a thickness in the first direction; and a shield provided between the piezoelectric layer and the substrate member, wherein the support member has a space at a position at which the support member at least partially overlaps with the first functional electrode in a planar view in the first direction, the shield is provided at a position at which the shield at least partially overlaps with the first functional electrode in a planar view in the first direction, and the distance from the center of the shield to the piezoelectric layer is shorter than the distance from the center of the shield to the substrate member. (2) The piezoelectric device according to (1), wherein the support member has a space at a position at which the support member at least partially overlaps with the first functional electrode in a planar view in the first direction. (3) The piezoelectric device according to (1) or (2), wherein the shield is provided at a position that at least partially overlaps with the second functional electrode in a planar view in the first direction. (4) The piezoelectric device according to any one of (1) to (3), further comprising a sealing material provided between the piezoelectric layer and the substrate member, wherein the first functional electrode is provided in a region surrounded by the sealing material in a planar view in the first direction, wherein a space surrounded by the piezoelectric layer, the substrate member, and the sealing material is airtight, and wherein pressure in the space is greater than atmospheric pressure. (5) The piezoelectric device according to any one of (1) to (4), wherein a distance from the shield to the first main surface of the piezoelectric layer is different between a center of the shield and a position other than the center of the shield, and wherein the distance from the center of the shield to the piezoelectric layer is shorter than a distance from a position other than the center of the shield to the piezoelectric layer. (6) The piezoelectric device according to any one of (1) to (5), further comprising a coating layer provided on a surface of the shield, the coating layer having lower electrical conductivity than the shield and higher thermal conductivity and emissivity than the shield.(7) The piezoelectric device according to any one of (1) to (6), further comprising a coating layer provided on a surface of the shield, the coating layer having lower conductivity than the shield and higher emissivity than the shield.

[0090] 1, 1A, 1B Piezoelectric device 100 First element 110 Support member 111 Support substrate 112 Intermediate layer 113 Space portion 113S Sacrificial layer 120 Piezoelectric layer 120a First main surface 120b Second main surface 121 Through hole 130 First functional electrode 131 Upper electrode 131a Main electrode portion 131b Extension portion 132 Lower electrode 132a Main electrode portion 132b Extension portion 133, 134 Wiring electrodes 141 to 143 Through electrodes 200, 200A Second element 210 Substrate member 211 Support substrate 212 Intermediate layer 213 Piezoelectric layer 213a First main surface 213b Second main surface 230, 230A Second functional electrode 231 First electrode finger 232 Second electrode finger 233 First bus bar 234 Second bus bar 241 Through electrode 310, 310A Shield 311 Space 311S Sacrificial layer 312 Covering layer 320 Sealing material 321 First portion 322 Second portion 323 Joint portion 330 Space C Center

Claims

1. A piezoelectric device comprising: a piezoelectric layer having a thickness in a first direction, and having a first main surface and a second main surface opposite to the first main surface; a support member provided on the second main surface side of the piezoelectric layer; a first functional electrode provided on at least one of the first main surface and the second main surface of the piezoelectric layer; a substrate member facing the first main surface of the piezoelectric layer at a distance in the first direction, having a second functional electrode and having a thickness in the first direction; and a shield provided between the piezoelectric layer and the substrate member, wherein the shield is provided at a position at least partially overlapping with the first functional electrode when viewed in a plane in the first direction, and the distance from the center of the shield to the piezoelectric layer is shorter than the distance from the center of the shield to the substrate member.

2. The piezoelectric device according to claim 1, wherein the support member has a space at a position where it at least partially overlaps the first functional electrode when viewed in a plane in the first direction.

3. The piezoelectric device according to claim 1 or 2, wherein the shield is disposed at a position at which it at least partially overlaps the second functional electrode when viewed in a plane in the first direction.

4. A piezoelectric device as described in any one of claims 1 to 3, further comprising a sealing material provided between the piezoelectric layer and the substrate member, the first functional electrode being provided in an area surrounded by the sealing material when viewed in a plane in the first direction, the space surrounded by the piezoelectric layer, the substrate member and the sealing material being airtight, and the pressure within the space being greater than atmospheric pressure.

5. A piezoelectric device as described in any one of claims 1 to 4, wherein the distance from the shield to the first main surface of the piezoelectric layer is different between the center of the shield and a position other than the center of the shield, and the distance from the center of the shield to the piezoelectric layer is smaller than the distance from the position other than the center of the shield to the piezoelectric layer.

6. A piezoelectric device according to any one of claims 1 to 5, further comprising a coating layer provided on a surface of said shield, said coating layer having a lower electrical conductivity than said shield and a higher thermal conductivity than said shield.

7. The piezoelectric device according to any one of claims 1 to 6, further comprising a coating layer provided on a surface of the shield, the coating layer having a lower electrical conductivity than the shield and a higher emissivity than the shield.

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