piezoelectric devices

Abstract

The stacked portion (120) includes, at least above the opening (113), a first single-crystal piezoelectric layer (130), a second single-crystal piezoelectric layer (140), an intermediate electrode layer (150), a lower electrode layer (160), and an upper electrode layer (170). The first single-crystal piezoelectric layer (130) is made of a material that generates an etching rate difference between the positive and negative sides of the polarization charge. The polarization charge of the first single-crystal piezoelectric layer (130) is positive on the side of the intermediate electrode layer (150) and negative on the side of the lower electrode layer (160).

Description

Technical Field

[0001] This invention relates to piezoelectric devices. Background Technology

[0002] International Publication No. 2019 / 102951 (Patent Document 1) discloses the structure of a piezoelectric device. The piezoelectric device described in Patent Document 1 includes a piezoelectric single crystal, an upper electrode, a lower electrode, and a support substrate. The piezoelectric single crystals have the same polarization state. The upper electrode is disposed on the upper surface of the piezoelectric single crystal. The lower electrode is disposed on the lower surface of the piezoelectric single crystal. The support substrate is disposed below the piezoelectric single crystal. A recess is provided that extends from the lower surface of the support substrate into the lower surface of the piezoelectric single crystal.

[0003] Prior art literature

[0004] Patent documents

[0005] Patent Document 1: International Publication No. 2019 / 102951 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] The piezoelectric device described in Patent Document 1 has only one single-crystal piezoelectric layer. When it is desired to increase the amplitude of the piezoelectric device during excitation, the area of ​​the single-crystal piezoelectric layer increases when viewed from a direction orthogonal to the single-crystal piezoelectric layer, thus increasing the area occupied by the piezoelectric device.

[0008] Furthermore, if through-holes are formed in the lower electrode layer due to over-etching when forming holes for electrical connection with the lower electrode layer by etching, the electrical connection with the lower electrode layer becomes insufficient, thereby reducing the excitation characteristics of the piezoelectric device.

[0009] The present invention was made in view of the above-mentioned problems, and its object is to provide a piezoelectric device that can suppress the reduction of excitation characteristics due to the increase of the occupied area of ​​the piezoelectric device and the insufficient electrical connection with the lower electrode layer, while increasing the amplitude of the piezoelectric device during excitation.

[0010] Technical solutions for solving the problem

[0011] The piezoelectric device according to the present invention includes a base and a laminated portion. The base includes a main surface and another main surface located on the side opposite to the main surface, and has an opening formed on one main surface. The laminated portion is laminated on one main surface side of the base and covers the opening from above. The laminated portion includes, at least above the opening, a first single-crystal piezoelectric layer, a second single-crystal piezoelectric layer disposed above the first single-crystal piezoelectric layer, an intermediate electrode layer disposed between the first single-crystal piezoelectric layer and the second single-crystal piezoelectric layer, a lower electrode layer disposed below the first single-crystal piezoelectric layer and opposite the intermediate electrode layer through the first single-crystal piezoelectric layer, and an upper electrode layer disposed above the second single-crystal piezoelectric layer and opposite the intermediate electrode layer through the second single-crystal piezoelectric layer, and has a diaphragm portion as a portion covering the opening. Viewed from a direction orthogonal to the aforementioned main plane, in the stacked portion, at the outer position of the opening, a hole is formed that penetrates the first single-crystal piezoelectric layer, the intermediate electrode layer, and the second single-crystal piezoelectric layer, reaching the lower electrode layer. An exit electrode is provided inside the hole; this exit electrode is insulated from the intermediate electrode layer but connected to the lower electrode layer, and extends to the upper surface of the second single-crystal piezoelectric layer. The first single-crystal piezoelectric layer is composed of a material that generates an etching rate difference between the positive and negative sides of the polarization charge. The polarization charge of the first single-crystal piezoelectric layer is positive on the intermediate electrode layer side and negative on the lower electrode layer side.

[0012] The effects of the invention

[0013] According to the present invention, it is possible to suppress the increase in the occupied area of ​​the piezoelectric device and the reduction in the excitation characteristics of the piezoelectric device due to poor connection with the lower electrode layer, while increasing the amplitude of the piezoelectric device during excitation. Attached Figure Description

[0014] Figure 1 This is a longitudinal sectional view of the piezoelectric device according to Embodiment 1 of the present invention.

[0015] Figure 2 This is a cross-sectional view showing the state in which a lower electrode layer is provided on the lower surface of the first single-crystal piezoelectric layer in the manufacturing method of the piezoelectric device according to Embodiment 1 of the present invention.

[0016] Figure 3 This is a cross-sectional view showing a state in which an intermediate layer is provided on the lower surface of both the lower electrode layer and the first single-crystal piezoelectric layer in the manufacturing method of the piezoelectric device according to Embodiment 1 of the present invention.

[0017] Figure 4 This illustrates that in the manufacturing method of the piezoelectric device according to Embodiment 1 of the present invention, the base is to be bonded to... Figure 3 A cross-sectional view showing the state of multiple layers.

[0018] Figure 5This is a cross-sectional view showing the state after the base is bonded to the lower surface of the intermediate layer in the manufacturing method of the piezoelectric device according to Embodiment 1 of the present invention.

[0019] Figure 6 This is a cross-sectional view showing the state after the upper surface of the first single-crystal piezoelectric layer has been removed in the manufacturing method of the piezoelectric device according to Embodiment 1 of the present invention.

[0020] Figure 7 This is a cross-sectional view showing the state in which an intermediate electrode layer is provided on the upper surface of the first single-crystal piezoelectric layer in the manufacturing method of the piezoelectric device according to Embodiment 1 of the present invention.

[0021] Figure 8 This illustrates the method for manufacturing a piezoelectric device according to Embodiment 1 of the present invention, in which a second single-crystal piezoelectric layer is bonded to... Figure 7 A cross-sectional view showing the state of multiple layers.

[0022] Figure 9 This is a cross-sectional view showing the state after the upper surface of the second single-crystal piezoelectric layer has been removed in the manufacturing method of the piezoelectric device according to Embodiment 1 of the present invention.

[0023] Figure 10 This is a cross-sectional view showing the state in which an upper electrode layer is provided on the upper surface of the second single-crystal piezoelectric layer in the manufacturing method of the piezoelectric device according to Embodiment 1 of the present invention.

[0024] Figure 11 This is a cross-sectional view showing the state in which holes are formed in the laminated portion during the manufacturing method of the piezoelectric device according to Embodiment 1 of the present invention.

[0025] Figure 12 This is a cross-sectional view showing the state in which an insulating film is formed inside the hole formed in the laminate in the manufacturing method of the piezoelectric device according to Embodiment 1 of the present invention.

[0026] Figure 13 This is a cross-sectional view showing the state of the central portion of the bottom of the insulating film removed in the manufacturing method of the piezoelectric device according to Embodiment 1 of the present invention.

[0027] Figure 14 This is a cross-sectional view showing the state in which lead-out electrodes are formed in the manufacturing method of the piezoelectric device according to Embodiment 1 of the present invention.

[0028] Figure 15 This is a cross-sectional view showing the state of each of the first and second lead wires formed in the manufacturing method of the piezoelectric device according to Embodiment 1 of the present invention.

[0029] Figure 16 This is a longitudinal sectional view of the piezoelectric device according to Embodiment 2 of the present invention. Detailed Implementation

[0030] (Implementation Method 1)

[0031] Figure 1 This is a longitudinal sectional view of the piezoelectric device according to Embodiment 1 of the present invention. Figure 1 As shown, the piezoelectric device 100 according to Embodiment 1 of the present invention includes a base 110 and a laminated portion 120.

[0032] The base 110 includes a main surface 111 and another main surface 112 located on the side opposite to the main surface 111. The base 110 has an opening 113 formed on the main surface 111. In this embodiment, the opening 113 extends from one main surface 111 to the other main surface 112. However, the opening 113 may also be formed from the side of the main surface 111 without reaching the other main surface 112. Alternatively, the opening 113 may be formed from the side of the other main surface 112 to a position close to one main surface 111 without reaching the main surface 111. The opening 113 is covered from above by a stacked portion 120 stacked on the side of one main surface 111 of the base 110.

[0033] In this embodiment, the base 110 is made of Si. However, the material constituting the base 110 is not limited to Si.

[0034] The stacked portion 120 includes, at least above the opening 113, a first single-crystal piezoelectric layer 130, a second single-crystal piezoelectric layer 140, an intermediate electrode layer 150, a lower electrode layer 160, and an upper electrode layer 170.

[0035] The laminate 120 has a diaphragm portion Mb that covers the opening 113. Viewed from a direction orthogonal to a main surface 111, the diaphragm portion Mb is the portion of the laminate 120 located inside the opening end of the opening 113.

[0036] Viewed from a direction orthogonal to a main surface 111, in the stacked portion 120, a hole H is formed outside the opening 113, penetrating the first single-crystal piezoelectric layer 130, the intermediate electrode layer 150, and the second single-crystal piezoelectric layer 140 to reach the lower electrode layer 160. An insulating film 194 is formed on the inner peripheral surface of the hole H. A lead-out electrode 193 is provided inside the hole H. This lead-out electrode 193 is insulated from the intermediate electrode layer 150, connected to the lower electrode layer 160, and leads out to the upper surface of the second single-crystal piezoelectric layer 140.

[0037] The first single-crystal piezoelectric layer 130 is located above the base 110. A portion of the first single-crystal piezoelectric layer 130 is located above the opening 113. The upper and lower surfaces of the first single-crystal piezoelectric layer 130 are each flat.

[0038] The second single-crystal piezoelectric layer 140 is located above the first single-crystal piezoelectric layer 130. A portion of the second single-crystal piezoelectric layer 140 is located above the opening 113. The upper and lower surfaces of the second single-crystal piezoelectric layer 140 are both flat.

[0039] The second single-crystal piezoelectric layer 140 has a hole 141. The hole 141 extends vertically through the second single-crystal piezoelectric layer 140. In this embodiment, the hole 141 is located above a main surface 111 of the base 110, and not above the opening 113.

[0040] The first single-crystal piezoelectric layer 130 is made of a material that generates an etching rate difference between the positive and negative sides of the polarization charge. The second single-crystal piezoelectric layer 140 is made of a material that generates an etching rate difference between the positive and negative sides of the polarization charge. The second single-crystal piezoelectric layer 140 may be made of the same material as the first single-crystal piezoelectric layer 130, or it may be made of a different material than the first single-crystal piezoelectric layer 130.

[0041] In this embodiment, the first single-crystal piezoelectric layer 130 and the second single-crystal piezoelectric layer 140 are each composed of lithium niobate (LiNbO3) or lithium tantalate (LiTaO3). Alternatively, the first single-crystal piezoelectric layer 130 and the second single-crystal piezoelectric layer 140 may each be composed of niobate compounds or tantalate compounds of alkali metals other than K and Na.

[0042] The polarization charge of the first single-crystal piezoelectric layer 130 is positive on the side of the intermediate electrode layer 150 and negative on the side of the lower electrode layer 160. The polarization charge of the second single-crystal piezoelectric layer 140 is positive on the side of the intermediate electrode layer 150 and negative on the side of the upper electrode layer 170. Alternatively, the polarization charge of the second single-crystal piezoelectric layer 140 may also be negative on the side of the intermediate electrode layer 150 and positive on the side of the upper electrode layer 170.

[0043] An intermediate electrode layer 150 is located between the first single-crystal piezoelectric layer 130 and the second single-crystal piezoelectric layer 140. The intermediate electrode layer 150 is sandwiched between the upper surface of the first single-crystal piezoelectric layer 130 and the lower surface of the second single-crystal piezoelectric layer 140. A portion of the intermediate electrode layer 150 is located above the opening 113. Both the upper and lower surfaces of the intermediate electrode layer 150 are flat. The intermediate electrode layer 150 can also be constructed by stacking two electrode layers. In this embodiment, the thickness of the intermediate electrode layer 150 is thicker than the thicknesses of the lower electrode layer 160 and the upper electrode layer 170. However, the thickness of the intermediate electrode layer 150 can also be less than the thicknesses of the lower electrode layer 160 and the upper electrode layer 170.

[0044] The intermediate electrode layer 150 is made of a metal such as Al or Pt. Alternatively, the intermediate electrode layer 150 may be made of Si, which has low resistivity and is doped with As. In this case, the intermediate electrode layer 150 is preferably made of Si with a resistivity of 20 mΩcm or less. Alternatively, the intermediate electrode layer 150 may also be made of a conductive oxide such as LaNiO3, SrRuO3, or RuO2.

[0045] Alternatively, a close-bonding layer made of Ti or the like may be disposed between the intermediate electrode layer 150 and the first single-crystal piezoelectric layer 130. A close-bonding layer made of Ti or the like may also be disposed between the intermediate electrode layer 150 and the second single-crystal piezoelectric layer 140.

[0046] The lower electrode layer 160 is disposed below the first single-crystal piezoelectric layer 130, and faces the intermediate electrode layer 150 across the first single-crystal piezoelectric layer 130. A portion of the lower electrode layer 160 is located above the opening 113. Another portion of the lower electrode layer 160 is located below the hole H formed in the first single-crystal piezoelectric layer 130. The other portion of the lower electrode layer 160 covers the hole H from below.

[0047] The lower electrode layer 160 is made of metals such as Al or Pt. The lower electrode layer 160 may also be made of conductive oxides such as LaNiO3, SrRuO3, or RuO2. The lower electrode layer 160 may also be an epitaxial growth film formed by epitaxial growth of a conductive material.

[0048] The upper electrode layer 170 is disposed above the second single-crystal piezoelectric layer 140 and is opposite to the intermediate electrode layer 150 across the second single-crystal piezoelectric layer 140. A portion of the upper electrode layer 170 is located above the opening 113.

[0049] The upper electrode layer 170 is made of a metal such as Al or Pt. The upper electrode layer 170 may also be an epitaxial growth film formed by epitaxial growth of a conductive material. Alternatively, a close-fitting layer made of Ti or the like may be disposed between the upper electrode layer 170 and the second single-crystal piezoelectric layer 140.

[0050] Lead-out electrodes 193 are formed all over the upper surface of the second single-crystal piezoelectric layer 140, the inner peripheral surface of the insulating film 194, and the upper surface of a portion of the lower electrode layer 160 exposed through the hole H. Lead-out electrodes 193 are made of metals such as Al or Pt. The insulating film 194 is made of an insulating material such as SiO2.

[0051] The stacked portion 120 also includes an intermediate layer 180. The intermediate layer 180 sandwiches a lower electrode layer 160 between itself and the first single-crystal piezoelectric layer 130. An opening 183 communicating with an opening 113 of the base portion 110 is formed on the lower surface of the intermediate layer 180. The opening 183 is located above the opening 113. Through the opening 183, a portion of the lower surface of the lower electrode layer 160 is exposed. The portion of the lower surface of the lower electrode layer 160 exposed through the opening 183 constitutes the lower surface of the diaphragm portion Mb.

[0052] The intermediate layer 180 is composed of SiO2. The material of the intermediate layer 180 is not limited to SiO2, as long as it is an insulating material. For example, the intermediate layer 180 can also be composed of an organic material with electrical insulation and thermal insulation properties.

[0053] The piezoelectric device 100 also includes a first lead wire 191 and a second lead wire 192. The first lead wire 191 is disposed on the upper side of the upper electrode layer 170. The second lead wire 192 is disposed within the hole 141 on the upper side of the intermediate electrode layer 150.

[0054] Thus, the stacked portion 120 includes at least above the opening 113 a first single-crystal piezoelectric layer 130, a second single-crystal piezoelectric layer 140, an intermediate electrode layer 150, a lower electrode layer 160, and an upper electrode layer 170.

[0055] In this embodiment, when viewed from a direction orthogonal to a main surface 111, the opening 113 has a rectangular shape. However, when viewed from a direction orthogonal to a main surface 111, the shape of the opening 113 is not limited to a rectangle; it can also be a polygon or a circle other than a rectangle.

[0056] According to the above structure, by applying a voltage between the lower electrode layer 160 and the middle electrode layer 150, the first single crystal piezoelectric layer 130 expands and contracts, and by applying a voltage between the upper electrode layer 170 and the middle electrode layer 150, the second single crystal piezoelectric layer 140 expands and contracts. On the other hand, the upper electrode layer 170, the middle electrode layer 150 and the lower electrode layer 160 do not expand or contract, so the diaphragm portion Mb bends and vibrates up and down.

[0057] The manufacturing method of the piezoelectric device according to Embodiment 1 of the present invention will be described below.

[0058] Figure 2 This is a cross-sectional view showing the state in which a lower electrode layer is provided on the lower surface of the first single-crystal piezoelectric layer in the manufacturing method of the piezoelectric device according to Embodiment 1 of the present invention. The thickness of the first single-crystal piezoelectric layer 130 during formation is thicker than the thickness of the first single-crystal piezoelectric layer 130 ultimately included in the piezoelectric device 100 according to this embodiment.

[0059] The polarization charge of the first single-crystal piezoelectric layer 130 is positive on the upper surface and negative on the lower surface. The first single-crystal piezoelectric layer 130 is made of a material that produces an etching rate difference between the positive and negative polarization charge sides.

[0060] like Figure 2 As shown, a lower electrode layer 160 is formed on the lower surface of the first single-crystal piezoelectric layer 130 by methods such as lift-off, plating, or etching. When the lower electrode layer 160 is composed of a conductive oxide, the conductive oxide, formed by oxidizing the metal contained in the target, is deposited on the lower surface of the first single-crystal piezoelectric layer 130 by reactive sputtering, thereby forming the lower electrode layer 160. When the lower electrode layer 160 is an epitaxially grown film, a conductive film is formed on the lower surface of the first single-crystal piezoelectric layer 130 by heteroepitaxial growth, and the conductive film is patterned to form the lower electrode layer 160.

[0061] Figure 3 This is a cross-sectional view showing a state in which an intermediate layer is provided on the lower surface of both the lower electrode layer and the first single-crystal piezoelectric layer in the manufacturing method of the piezoelectric device according to Embodiment 1 of the present invention. Figure 3 As shown, an intermediate layer 180 is formed on the lower surface of the lower electrode layer 160 and the first single crystal piezoelectric layer 130 by chemical vapor deposition (CVD) or physical vapor deposition (PVD), and then the lower surface of the intermediate layer 180 is flattened by chemical mechanical polishing (CMP).

[0062] Figure 4 This illustrates that in the manufacturing method of the piezoelectric device according to Embodiment 1 of the present invention, the base is to be bonded to... Figure 3 A cross-sectional view showing the state of multiple layers. Figure 5 This is a cross-sectional view showing the state in which the base is bonded to the lower surface of the intermediate layer in the manufacturing method of the piezoelectric device according to Embodiment 1 of the present invention.

[0063] like Figure 4 and Figure 5 As shown, the substrate 110, which has no opening 113, is bonded to the lower surface of the intermediate layer 180 by surface activation bonding or atomic diffusion bonding. Alternatively, the opening 113 may be pre-formed in the base 110.

[0064] Figure 6 This is a cross-sectional view showing the state after the upper surface of the first single-crystal piezoelectric layer has been removed in the manufacturing method of the piezoelectric device according to Embodiment 1 of the present invention. Figure 6 As shown, the upper surface of the first single-crystal piezoelectric layer 130 is removed by CMP or similar methods to achieve the desired thickness. Alternatively, a release layer can be formed beforehand on the upper surface of the first single-crystal piezoelectric layer 130 by ion implantation. In this case, the release layer is removed before the upper surface of the first single-crystal piezoelectric layer 130 is removed by cutting or CMP, thereby facilitating the adjustment of the thickness of the first single-crystal piezoelectric layer 130. The thickness of the first single-crystal piezoelectric layer 130 is adjusted to obtain the desired excitation of the first single-crystal piezoelectric layer 130 caused by the application of voltage.

[0065] Figure 7 This is a cross-sectional view showing a state in which an intermediate electrode layer is provided on the upper surface of a first single-crystal piezoelectric layer in the manufacturing method of the piezoelectric device according to Embodiment 1 of the present invention. Figure 7 As shown, an intermediate electrode layer 150 is formed on the upper surface of the first single-crystal piezoelectric layer 130 by means of peeling, plating or etching.

[0066] When the intermediate electrode layer 150 is made of Si, which has low resistivity, a Si substrate doped with As or the like is bonded to the upper surface of the first single-crystal piezoelectric layer 130 by surface activation bonding or atomic diffusion bonding. Then, the upper surface of the Si substrate is removed by CMP or the like to achieve the desired thickness. Alternatively, a release layer can be formed on the upper surface of the Si substrate beforehand by ion implantation. In this case, the release layer is removed before the upper surface of the Si substrate is removed by cutting or CMP, making it easier to adjust the thickness of the Si substrate. When the intermediate electrode layer 150 is made of a conductive oxide, the conductive oxide, formed by oxidizing a metal contained in a target, is deposited on the upper surface of the first single-crystal piezoelectric layer 130 by reactive sputtering, thereby forming the intermediate electrode layer 150.

[0067] Figure 8 This illustrates the method for manufacturing a piezoelectric device according to Embodiment 1 of the present invention, in which a second single-crystal piezoelectric layer is bonded to... Figure 7 A cross-sectional view showing the state of multiple layers. (See also...) Figure 8 As shown, the second single-crystal piezoelectric layer 140 is bonded to the upper surface of the intermediate electrode layer 150 by surface activation bonding or atomic diffusion bonding. The thickness of the second single-crystal piezoelectric layer 140 during formation is thicker than the thickness of the second single-crystal piezoelectric layer 140 ultimately included in the piezoelectric device 100 according to this embodiment.

[0068] In this embodiment, the polarization charge of the second single-crystal piezoelectric layer 140 is negative on the upper surface and positive on the lower surface. The second single-crystal piezoelectric layer 140 is made of a material that generates an etching rate difference between the positive and negative polarization charge sides.

[0069] Figure 9 This is a cross-sectional view showing the state after the upper surface of the second single-crystal piezoelectric layer has been removed in the manufacturing method of the piezoelectric device according to Embodiment 1 of the present invention. Figure 9 As shown, the upper surface of the second single-crystal piezoelectric layer 140 is removed by CMP or similar methods to achieve the desired thickness. Alternatively, a release layer can be formed beforehand on the upper surface of the second single-crystal piezoelectric layer 140 by ion implantation. In this case, the release layer is removed before the upper surface of the second single-crystal piezoelectric layer 140 is removed by cutting or CMP, thereby facilitating the adjustment of the thickness of the second single-crystal piezoelectric layer 140. The thickness of the second single-crystal piezoelectric layer 140 is adjusted to obtain the desired excitation of the second single-crystal piezoelectric layer 140 caused by the application of voltage.

[0070] Figure 10This is a cross-sectional view showing a state in which an upper electrode layer is provided on the upper surface of the second single-crystal piezoelectric layer in the manufacturing method of the piezoelectric device according to Embodiment 1 of the present invention. Figure 10 As shown, an upper electrode layer 170 is formed on the upper surface of the second single-crystal piezoelectric layer 140 by methods such as peeling, plating, or etching. When the upper electrode layer 170 is an epitaxially grown film, the upper electrode layer 170 is formed by forming a conductive film on the upper surface of the second single-crystal piezoelectric layer 140 through heteroepitaxial growth and patterning the conductive film.

[0071] Figure 11 This is a cross-sectional view showing a state in which holes are formed in the laminated portion during the manufacturing method of the piezoelectric device according to Embodiment 1 of the present invention. Figure 11 As shown, an etching method is used to form a hole H that penetrates the first single-crystal piezoelectric layer 130, the intermediate electrode layer 150, and the second single-crystal piezoelectric layer 140, reaching the lower electrode layer 160. Furthermore, an etching method is used to form a hole 141 that penetrates the second single-crystal piezoelectric layer 140, reaching the intermediate electrode layer 150.

[0072] Hole H and hole 141 are each formed by etching from the upper surface side of the second single-crystal piezoelectric layer 140. The second single-crystal piezoelectric layer 140 is made of a material that produces an etching rate difference between the positive and negative sides of the polarization charge. The etching rate is higher when etching is performed from the negative side of the polarization charge than when etching is performed from the positive side of the polarization charge. Since the polarization charge of the second single-crystal piezoelectric layer 140 is negative on the upper surface side and positive on the lower surface side, etching from the upper surface side of the second single-crystal piezoelectric layer 140 allows for etching at a high etching rate.

[0073] In this embodiment, since the thickness of the intermediate electrode layer 150 is greater than the thickness of the lower electrode layer 160 and the upper electrode layer 170, it is possible to suppress the hole portion 141 from penetrating the intermediate electrode layer 150 due to over-etching.

[0074] After the hole H penetrates the intermediate electrode layer 150, the first single-crystal piezoelectric layer 130 is etched from the upper surface side. The first single-crystal piezoelectric layer 130 is made of a material that produces an etching rate difference between the positive and negative sides of the polarization charge. The etching rate when etching from the positive side of the polarization charge is lower than the etching rate when etching from the negative side of the polarization charge. Since the polarization charge of the first single-crystal piezoelectric layer 130 is positive on the upper surface side and negative on the lower surface side, etching from the upper surface side of the first single-crystal piezoelectric layer 130 allows for etching at a low etching rate. This prevents the hole H from penetrating the lower electrode layer 160 due to over-etching.

[0075] Figure 12 This is a cross-sectional view showing a state in which an insulating film is formed inside the hole formed in the laminated portion during the manufacturing method of the piezoelectric device according to Embodiment 1 of the present invention. Figure 12 As shown, an insulating film 194 is formed on the inside of the hole H by sputtering or CVD.

[0076] Figure 13 This is a cross-sectional view showing the state of the central portion of the bottom of the piezoelectric device after the insulating film has been removed in the manufacturing method of the piezoelectric device according to Embodiment 1 of the present invention. Figure 13 As shown, by etching, a portion of the insulating film 194 located on the inner circumferential surface of the hole H is left, while the central portion of the bottom of the insulating film 194 is removed, thereby exposing a portion of the lower electrode layer 160.

[0077] Figure 14 This is a cross-sectional view showing the state in which the lead-out electrodes are formed in the manufacturing method of the piezoelectric device according to Embodiment 1 of the present invention. Figure 14 As shown, the second single-crystal piezoelectric layer 140 is formed on the upper surface of the second single-crystal piezoelectric layer 140, the inner peripheral surface of the insulating film 194, and the upper surface of a portion of the lower electrode layer 160 exposed through the hole H by sputtering, vapor deposition, or plating.

[0078] Figure 15 This is a cross-sectional view showing the state of each of the first and second lead wires formed in the manufacturing method of the piezoelectric device according to Embodiment 1 of the present invention. Figure 15 As shown, a first lead wire 191 is formed on the upper surface of the upper electrode layer 170 by means of stripping, plating or vapor deposition, and a second lead wire 192 is formed on the upper surface of a portion of the intermediate electrode layer 150 exposed through the hole 141.

[0079] Finally, an opening 113 is formed on the base 110 and an opening 183 is formed on the intermediate layer 180 by etching. However, it is not always necessary to form the opening 183. Through the above processes, a product is manufactured as shown... Figure 1 The piezoelectric device 100 shown is related to Embodiment 1 of the present invention.

[0080] In the piezoelectric device 100 according to Embodiment 1 of the present invention, a diaphragm portion Mb is provided. This diaphragm portion Mb has two single-crystal piezoelectric layers: a first single-crystal piezoelectric layer 130 sandwiched between an intermediate electrode layer 150 and a lower electrode layer 160, and a second single-crystal piezoelectric layer 140 sandwiched between an intermediate electrode layer 150 and an upper electrode layer 170. Therefore, compared to a piezoelectric device having only one single-crystal piezoelectric layer, the amplitude of the piezoelectric device during excitation can be increased without increasing the area of ​​the single-crystal piezoelectric layer. As a result, the amplitude of the piezoelectric device 100 during excitation can be increased while suppressing an increase in the occupied area of ​​the piezoelectric device 100.

[0081] In the piezoelectric device 100 according to Embodiment 1 of the present invention, the first single-crystal piezoelectric layer 130 is made of a material that generates an etching rate difference between the positive and negative sides of the polarization charge. The polarization charge of the first single-crystal piezoelectric layer 130 is positive on the side of the intermediate electrode layer 150 and negative on the side of the lower electrode layer 160. Therefore, when forming the hole H for electrical connection with the lower electrode layer 160 by etching, the first single-crystal piezoelectric layer 130 can be etched at a low etching rate, thus suppressing the formation of through holes in the lower electrode layer 160 due to over-etching. As a result, it is possible to suppress the reduction of the excitation characteristics of the piezoelectric device 100 due to insufficient electrical connection with the lower electrode layer 160.

[0082] In the piezoelectric device 100 according to Embodiment 1 of the present invention, the thickness of the intermediate electrode layer 150 is greater than the thicknesses of the lower electrode layer 160 and the upper electrode layer 170. This prevents the formation of through-holes in the intermediate electrode layer 150 due to over-etching during the etching process to form the hole portion 141. Consequently, it prevents insufficient electrical connection between the intermediate electrode layer 150 and the second lead-out wiring 192 from degrading the excitation characteristics of the piezoelectric device 100.

[0083] In the piezoelectric device 100 according to Embodiment 1 of the present invention, the intermediate electrode layer 150 may also be made of Si. In this case, since Si is crystallized and stable, it does not react with each of the piezoelectric layers 130 and 140, thereby suppressing the degradation of the characteristics of the first single-crystal piezoelectric layer 130 and the second single-crystal piezoelectric layer 140 due to mutual reactions with each of the piezoelectric layers 130 and 140.

[0084] In the piezoelectric device 100 according to Embodiment 1 of the present invention, since the second single-crystal piezoelectric layer 140 is made of a material that generates an etching rate difference between the positive and negative sides of the polarization charge, the polarization charge of the second single-crystal piezoelectric layer 140 is positive on the side of the intermediate electrode layer 150 and negative on the side of the upper electrode layer 170. Therefore, by etching from the upper surface side of the second single-crystal piezoelectric layer 140, the second single-crystal piezoelectric layer 140 can be etched at a high etching rate. As a result, the time required for etching the second single-crystal piezoelectric layer 140 can be shortened.

[0085] In the piezoelectric device 100 according to Embodiment 1 of the present invention, the first single-crystal piezoelectric layer 130 and the second single-crystal piezoelectric layer 140 are each composed of a niobate compound or a tantalate compound of an alkali metal other than K and Na, and are lead-free, thus reducing the environmental burden. The first single-crystal piezoelectric layer 130 and the second single-crystal piezoelectric layer 140 are each composed of lithium niobate (LiNbO3) or lithium tantalate (LiTaO3), thereby improving the piezoelectric characteristics of the piezoelectric device 100.

[0086] In the piezoelectric device 100 according to Embodiment 1 of the present invention, at least one of the lower electrode layer 160 and the intermediate electrode layer 150 may also be made of a conductive oxide. When the lower electrode layer 160 is made of a conductive oxide, when dry etching the first single-crystal piezoelectric layer 130 to form the hole H, increasing the etch selectivity ratio between the first single-crystal piezoelectric layer 130 and the lower electrode layer 160 can suppress the formation of through-holes in the lower electrode layer 160 due to over-etching. When the intermediate electrode layer 150 is made of a conductive oxide, when dry etching the second single-crystal piezoelectric layer 140 to form the hole 141, increasing the etch selectivity ratio between the second single-crystal piezoelectric layer 140 and the intermediate electrode layer 150 can suppress the formation of through-holes in the intermediate electrode layer 150 due to over-etching.

[0087] In the piezoelectric device 100 according to Embodiment 1 of the present invention, at least one of the lower electrode layer 160 and the upper electrode layer 170 may be an epitaxially grown film. The epitaxially grown film has good crystallinity, thus it can suppress migration and improve the power handling characteristics of the lower electrode layer 160 and the upper electrode layer 170 respectively.

[0088] (Implementation Method 2)

[0089] Hereinafter, the piezoelectric device according to Embodiment 2 of the present invention will be described with reference to the accompanying drawings. The only difference between the piezoelectric device according to Embodiment 2 of the present invention and the piezoelectric device 100 according to Embodiment 1 of the present invention is that a lower electrode layer for reinforcement is provided. Therefore, the same structure as the piezoelectric device 100 according to Embodiment 1 of the present invention will not be described again.

[0090] Figure 16 This is a longitudinal sectional view of the piezoelectric device according to Embodiment 2 of the present invention. Figure 16 As shown, in the piezoelectric device 200 according to Embodiment 2 of the present invention, a reinforcing lower electrode layer 260 is provided on the lower side of the portion of the lower electrode layer 160 located below the hole H.

[0091] The lower electrode layer 260 for reinforcement is made of metals such as Al or Pt. The lower electrode layer 260 for reinforcement may also be made of conductive oxides such as LaNiO3, SrRuO3, or RuO2. Alternatively, the lower electrode layer 260 for reinforcement may be an epitaxially grown film formed by epitaxially growing a conductive material.

[0092] Specifically, the reinforcement lower electrode layer 260 is formed on the lower surface of the lower electrode layer 160 by methods such as stripping, plating, or etching. When the reinforcement lower electrode layer 260 is composed of a conductive oxide, the conductive oxide, after oxidation of the metal contained in the target, is deposited on the lower surface of the lower electrode layer 160 by reactive sputtering, thereby forming the reinforcement lower electrode layer 260. When the reinforcement lower electrode layer 260 is an epitaxially grown film, a conductive film is formed on the lower surface of the lower electrode layer 160 by homoepitaxial growth, and the conductive film is patterned to form the reinforcement lower electrode layer 260.

[0093] In the piezoelectric device 200 according to Embodiment 2 of the present invention, by providing a reinforcing lower electrode layer 260 on the lower side of the portion of the lower electrode layer 160 located below the hole H, it is possible to suppress the formation of through holes in the lower electrode layer 160 and the reinforcing lower electrode layer 260 due to over-etching when the hole H is formed by etching.

[0094] Furthermore, when the formation of through-holes caused by over-etching is prevented by making the lower electrode layer 160 thicker overall, the piezoelectric device's excitation characteristics decrease due to the stress generated in the lower electrode layer 160 causing warping of the diaphragm portion Mb. However, by providing a reinforcing lower electrode layer 260 only on the lower side of the portion of the lower electrode layer 160 located below the hole portion H, the decrease in the piezoelectric device's excitation characteristics due to warping of the diaphragm portion Mb can be suppressed.

[0095] In the description of the above embodiments, the structures that can be combined can also be combined with each other.

[0096] The embodiments disclosed herein should be considered illustrative rather than restrictive in all respects. The scope of the invention is set forth not by the foregoing description but by the claims, which are intended to encompass all modifications within the meaning and scope of the claims.

[0097] Description of Reference Numerals

[0098] 100, 200: Piezoelectric device; 110: Base; 111, 112: Main surface; 113, 183: Opening; 120: Stacked portion; 130: First single-crystal piezoelectric layer; 140: Second single-crystal piezoelectric layer; 141, H: Hole; 150: Intermediate electrode layer; 160: Lower electrode layer; 170: Upper electrode layer; 180: Intermediate layer; 191: First lead-out wiring; 192: Second lead-out wiring; 193: Lead-out electrode; 194: Insulating film; 260: Lower electrode layer for reinforcement; Mb: Film portion.

Claims

1. A piezoelectric device comprising: A base comprising a main surface and another main surface located on the side opposite to the main surface, and having an opening formed in the main surface; and The laminated portion, which is stacked on one of the main surfaces of the base, covers the opening from above. The stacked portion includes, at least above the opening, a first single-crystal piezoelectric layer, a second single-crystal piezoelectric layer disposed above the first single-crystal piezoelectric layer, an intermediate electrode layer disposed between the first single-crystal piezoelectric layer and the second single-crystal piezoelectric layer, a lower electrode layer disposed below the first single-crystal piezoelectric layer and separated from the first single-crystal piezoelectric layer and opposite to the intermediate electrode layer, and an upper electrode layer disposed above the second single-crystal piezoelectric layer and separated from the second single-crystal piezoelectric layer and opposite to the intermediate electrode layer, and has a diaphragm portion covering the opening. Viewed from a direction orthogonal to the main surface, in the stacked portion, at a position outside the opening, a hole is formed that penetrates the first single-crystal piezoelectric layer, the intermediate electrode layer, and the second single-crystal piezoelectric layer to reach the lower electrode layer. An output electrode is provided inside the hole. This output electrode is insulated from the intermediate electrode layer but connected to the lower electrode layer, and extends to the upper surface of the second single-crystal piezoelectric layer. The first single-crystal piezoelectric layer is composed of a material that generates an etching rate difference between the positive and negative sides of the polarization charge. The polarization charge of the first single-crystal piezoelectric layer is positive on the middle electrode layer side and negative on the lower electrode layer side.

2. The piezoelectric device according to claim 1, wherein, The thickness of the intermediate electrode layer is greater than the thickness of both the lower electrode layer and the upper electrode layer.

3. The piezoelectric device according to claim 1 or 2, wherein, The intermediate electrode layer is made of Si.

4. The piezoelectric device according to claim 1, wherein, The second single-crystal piezoelectric layer is composed of a material that generates an etching rate difference between the positive and negative sides of the polarization charge. The polarization charge of the second single-crystal piezoelectric layer is positive on the middle electrode layer side and negative on the upper electrode layer side.

5. The piezoelectric device according to claim 2, wherein, The second single-crystal piezoelectric layer is composed of a material that generates an etching rate difference between the positive and negative sides of the polarization charge. The polarization charge of the second single-crystal piezoelectric layer is positive on the middle electrode layer side and negative on the upper electrode layer side.

6. The piezoelectric device according to claim 3, wherein, The second single-crystal piezoelectric layer is composed of a material that generates an etching rate difference between the positive and negative sides of the polarization charge. The polarization charge of the second single-crystal piezoelectric layer is positive on the middle electrode layer side and negative on the upper electrode layer side.

7. The piezoelectric device according to claim 1, wherein, The first single-crystal piezoelectric layer and the second single-crystal piezoelectric layer are each composed of lithium niobate (LiNbO3) or lithium tantalate (LiTaO3).

8. The piezoelectric device according to claim 2, wherein, The first single-crystal piezoelectric layer and the second single-crystal piezoelectric layer are each composed of lithium niobate (LiNbO3) or lithium tantalate (LiTaO3).

9. The piezoelectric device according to claim 3, wherein, The first single-crystal piezoelectric layer and the second single-crystal piezoelectric layer are each composed of lithium niobate (LiNbO3) or lithium tantalate (LiTaO3).

10. The piezoelectric device according to claim 4, wherein, The first single-crystal piezoelectric layer and the second single-crystal piezoelectric layer are each composed of lithium niobate (LiNbO3) or lithium tantalate (LiTaO3).

11. The piezoelectric device according to claim 5, wherein, The first single-crystal piezoelectric layer and the second single-crystal piezoelectric layer are each composed of lithium niobate (LiNbO3) or lithium tantalate (LiTaO3).

12. The piezoelectric device according to claim 6, wherein, The first single-crystal piezoelectric layer and the second single-crystal piezoelectric layer are each composed of lithium niobate (LiNbO3) or lithium tantalate (LiTaO3).

13. The piezoelectric device according to claim 1, wherein, At least one of the lower electrode layer and the middle electrode layer is composed of a conductive oxide.

14. The piezoelectric device according to claim 2, wherein, At least one of the lower electrode layer and the middle electrode layer is composed of a conductive oxide.

15. The piezoelectric device according to claim 3, wherein, At least one of the lower electrode layer and the middle electrode layer is composed of a conductive oxide.

16. The piezoelectric device according to claim 4, wherein, At least one of the lower electrode layer and the middle electrode layer is composed of a conductive oxide.

17. The piezoelectric device according to claim 5, wherein, At least one of the lower electrode layer and the middle electrode layer is composed of a conductive oxide.

18. The piezoelectric device according to claim 6, wherein, At least one of the lower electrode layer and the middle electrode layer is composed of a conductive oxide.

19. The piezoelectric device according to claim 7, wherein, At least one of the lower electrode layer and the middle electrode layer is composed of a conductive oxide.

20. The piezoelectric device according to claim 8, wherein, At least one of the lower electrode layer and the middle electrode layer is composed of a conductive oxide.

21. The piezoelectric device according to claim 9, wherein, At least one of the lower electrode layer and the middle electrode layer is composed of a conductive oxide.

22. The piezoelectric device according to claim 10, wherein, At least one of the lower electrode layer and the middle electrode layer is composed of a conductive oxide.

23. The piezoelectric device according to claim 11, wherein, At least one of the lower electrode layer and the middle electrode layer is composed of a conductive oxide.

24. The piezoelectric device according to claim 12, wherein, At least one of the lower electrode layer and the middle electrode layer is composed of a conductive oxide.

25. The piezoelectric device according to claim 1, wherein, At least one of the lower electrode layer and the upper electrode layer is an epitaxial growth film.

26. The piezoelectric device according to claim 2, wherein, At least one of the lower electrode layer and the upper electrode layer is an epitaxial growth film.

27. The piezoelectric device according to claim 3, wherein, At least one of the lower electrode layer and the upper electrode layer is an epitaxial growth film.

28. The piezoelectric device according to claim 4, wherein, At least one of the lower electrode layer and the upper electrode layer is an epitaxial growth film.

29. The piezoelectric device according to claim 5, wherein, At least one of the lower electrode layer and the upper electrode layer is an epitaxial growth film.

30. The piezoelectric device according to claim 6, wherein, At least one of the lower electrode layer and the upper electrode layer is an epitaxial growth film.

31. The piezoelectric device according to claim 7, wherein, At least one of the lower electrode layer and the upper electrode layer is an epitaxial growth film.

32. The piezoelectric device according to claim 8, wherein, At least one of the lower electrode layer and the upper electrode layer is an epitaxial growth film.

33. The piezoelectric device according to claim 9, wherein, At least one of the lower electrode layer and the upper electrode layer is an epitaxial growth film.

34. The piezoelectric device according to claim 10, wherein, At least one of the lower electrode layer and the upper electrode layer is an epitaxial growth film.

35. The piezoelectric device according to claim 11, wherein, At least one of the lower electrode layer and the upper electrode layer is an epitaxial growth film.

36. The piezoelectric device according to claim 12, wherein, At least one of the lower electrode layer and the upper electrode layer is an epitaxial growth film.

37. The piezoelectric device according to claim 1, wherein, A reinforcing lower electrode layer is provided on the lower side of the portion located below the hole in the lower electrode layer.

38. The piezoelectric device according to claim 2, wherein, A reinforcing lower electrode layer is provided on the lower side of the portion located below the hole in the lower electrode layer.

39. The piezoelectric device according to claim 3, wherein, A reinforcing lower electrode layer is provided on the lower side of the portion located below the hole in the lower electrode layer.

40. The piezoelectric device according to claim 4, wherein, A reinforcing lower electrode layer is provided on the lower side of the portion located below the hole in the lower electrode layer.

41. The piezoelectric device according to claim 5, wherein, A reinforcing lower electrode layer is provided on the lower side of the portion located below the hole in the lower electrode layer.

42. The piezoelectric device according to claim 6, wherein, A reinforcing lower electrode layer is provided on the lower side of the portion located below the hole in the lower electrode layer.

43. The piezoelectric device according to claim 7, wherein, A reinforcing lower electrode layer is provided on the lower side of the portion located below the hole in the lower electrode layer.

44. The piezoelectric device according to claim 8, wherein, A reinforcing lower electrode layer is provided on the lower side of the portion located below the hole in the lower electrode layer.

45. The piezoelectric device according to claim 9, wherein, A reinforcing lower electrode layer is provided on the lower side of the portion located below the hole in the lower electrode layer.

46. ​​The piezoelectric device according to claim 10, wherein, A reinforcing lower electrode layer is provided on the lower side of the portion located below the hole in the lower electrode layer.

47. The piezoelectric device according to claim 11, wherein, A reinforcing lower electrode layer is provided on the lower side of the portion located below the hole in the lower electrode layer.

48. The piezoelectric device according to claim 12, wherein, A reinforcing lower electrode layer is provided on the lower side of the portion located below the hole in the lower electrode layer.

49. The piezoelectric device according to claim 13, wherein, A reinforcing lower electrode layer is provided on the lower side of the portion located below the hole in the lower electrode layer.

50. The piezoelectric device according to claim 14, wherein, A reinforcing lower electrode layer is provided on the lower side of the portion located below the hole in the lower electrode layer.

51. The piezoelectric device according to claim 15, wherein, A reinforcing lower electrode layer is provided on the lower side of the portion located below the hole in the lower electrode layer.

52. The piezoelectric device according to claim 16, wherein, A reinforcing lower electrode layer is provided on the lower side of the portion located below the hole in the lower electrode layer.

53. The piezoelectric device according to claim 17, wherein, A reinforcing lower electrode layer is provided on the lower side of the portion located below the hole in the lower electrode layer.

54. The piezoelectric device according to claim 18, wherein, A reinforcing lower electrode layer is provided on the lower side of the portion located below the hole in the lower electrode layer.

55. The piezoelectric device according to claim 19, wherein, A reinforcing lower electrode layer is provided on the lower side of the portion located below the hole in the lower electrode layer.

56. The piezoelectric device according to claim 20, wherein, A reinforcing lower electrode layer is provided on the lower side of the portion located below the hole in the lower electrode layer.

57. The piezoelectric device according to claim 21, wherein, A reinforcing lower electrode layer is provided on the lower side of the portion located below the hole in the lower electrode layer.

58. The piezoelectric device according to claim 22, wherein, A reinforcing lower electrode layer is provided on the lower side of the portion located below the hole in the lower electrode layer.

59. The piezoelectric device according to claim 23, wherein, A reinforcing lower electrode layer is provided on the lower side of the portion located below the hole in the lower electrode layer.

60. The piezoelectric device according to claim 24, wherein, A reinforcing lower electrode layer is provided on the lower side of the portion located below the hole in the lower electrode layer.

61. The piezoelectric device according to claim 25, wherein, A reinforcing lower electrode layer is provided on the lower side of the portion located below the hole in the lower electrode layer.

62. The piezoelectric device according to claim 26, wherein, A reinforcing lower electrode layer is provided on the lower side of the portion located below the hole in the lower electrode layer.

63. The piezoelectric device according to claim 27, wherein, A reinforcing lower electrode layer is provided on the lower side of the portion located below the hole in the lower electrode layer.

64. The piezoelectric device according to claim 28, wherein, A reinforcing lower electrode layer is provided on the lower side of the portion located below the hole in the lower electrode layer.

65. The piezoelectric device according to claim 29, wherein, A reinforcing lower electrode layer is provided on the lower side of the portion located below the hole in the lower electrode layer.

66. The piezoelectric device according to claim 30, wherein, A reinforcing lower electrode layer is provided on the lower side of the portion located below the hole in the lower electrode layer.

67. The piezoelectric device according to claim 31, wherein, A reinforcing lower electrode layer is provided on the lower side of the portion located below the hole in the lower electrode layer.

68. The piezoelectric device according to claim 32, wherein, A reinforcing lower electrode layer is provided on the lower side of the portion located below the hole in the lower electrode layer.

69. The piezoelectric device according to claim 33, wherein, A reinforcing lower electrode layer is provided on the lower side of the portion located below the hole in the lower electrode layer.

70. The piezoelectric device according to claim 34, wherein, A reinforcing lower electrode layer is provided on the lower side of the portion located below the hole in the lower electrode layer.

71. The piezoelectric device according to claim 35, wherein, A reinforcing lower electrode layer is provided on the lower side of the portion located below the hole in the lower electrode layer.

72. The piezoelectric device according to claim 36, wherein, A reinforcing lower electrode layer is provided on the lower side of the portion located below the hole in the lower electrode layer.

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