Piezoelectric devices

Abstract

The stacked portion (120) includes, at least above the opening portion (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 produces an etching rate difference between the positive side and the negative side of the polarization charge. The polarization charge of the first single crystal piezoelectric layer (130) is negative on the intermediate electrode layer (150) side and positive on the lower electrode layer (160) side.

Description

Technical Field

[0001] The present invention relates to piezoelectric devices. Background Art

[0002] As a document that discloses the structure of a piezoelectric device, there is International Publication No. 2019 / 102951 (Patent Document 1). The piezoelectric device described in Patent Document 1 includes a piezoelectric single crystal, an upper electrode, a lower electrode, and a supporting substrate. The polarization state of the piezoelectric single crystal is the same. The upper electrode is arranged on the upper surface of the piezoelectric single crystal. The lower electrode is arranged on the lower surface of the piezoelectric single crystal. The supporting substrate is arranged below the piezoelectric single crystal. A recess is provided that is recessed from the lower surface of the supporting substrate to the lower surface of the piezoelectric single crystal.

[0003] Prior art literature

[0004] Patent Literature

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

[0006] Problems to be solved by the invention

[0007] The piezoelectric device described in Patent Document 1 has only one single crystal piezoelectric layer. When the amplitude of the piezoelectric device during excitation is to be increased, the area occupied by the piezoelectric device increases because the area of ​​the single crystal piezoelectric layer when viewed from a direction perpendicular to the single crystal piezoelectric layer increases.

[0008] When the amplitude of the piezoelectric device during excitation is increased by providing two single-crystal piezoelectric layers, the etching time required to form the hole for electrical connection with the lower electrode layer increases, thereby reducing the production efficiency of the piezoelectric device.

[0009] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a piezoelectric device that can increase the amplitude of the piezoelectric device when excited while suppressing an increase in the occupied area of ​​the piezoelectric device and a decrease in the production efficiency of the piezoelectric device.

[0010] Technical solutions to problems

[0011] The piezoelectric device according to the present invention comprises a base and a stacked portion. The base comprises a principal surface and another principal surface located on the side opposite to the principal surface, and has an opening formed on the principal surface. The stacked portion is stacked on the principal surface side of the base, covering the opening from above. The stacked portion comprises, at least above the opening, a first single-crystal piezoelectric layer, a second single-crystal piezoelectric layer arranged above the first single-crystal piezoelectric layer, an intermediate electrode layer arranged between the first single-crystal piezoelectric layer and the second single-crystal piezoelectric layer, a lower electrode layer arranged on the lower side of the first single-crystal piezoelectric layer and opposite to the intermediate electrode layer across the first single-crystal piezoelectric layer, and an upper electrode layer arranged on the upper side of the second single-crystal piezoelectric layer and opposite to the intermediate electrode layer across the second single-crystal piezoelectric layer, and has a diaphragm portion as a portion covering the opening. When viewed from a direction perpendicular to the aforementioned principal surface, a hole is formed in the laminated portion at a position outside the opening, penetrating the first single-crystal piezoelectric layer, the intermediate electrode layer, and the second single-crystal piezoelectric layer and reaching the lower electrode layer. An extraction electrode is provided inside the hole, insulated from the intermediate electrode layer while connected to the lower electrode layer, and extending to the upper surface of the second single-crystal piezoelectric layer. The first single-crystal piezoelectric layer is composed of a material that produces 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 negative on the intermediate electrode layer side and positive on the lower electrode layer side.

[0012] Effects of the Invention

[0013] According to the present invention, it is possible to increase the amplitude of the piezoelectric device during excitation while suppressing an increase in the occupied area of ​​the piezoelectric device and a decrease in the production efficiency of the piezoelectric device. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a longitudinal sectional view of the piezoelectric device according to the first embodiment of the present invention.

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

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

[0017] Figure 4 In the method for manufacturing a piezoelectric device according to the first embodiment of the present invention, the base portion is bonded to the Figure 3 A cross-sectional view of the state of the multiple layers shown.

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

[0019] Figure 6 This is a cross-sectional view showing a state after the upper surface of the first single-crystal piezoelectric layer is scraped off in the method for manufacturing the piezoelectric device according to the first embodiment of the present invention.

[0020] 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 method for manufacturing a piezoelectric device according to the first embodiment of the present invention.

[0021] Figure 8 The present invention is a method for manufacturing a piezoelectric device according to the first embodiment of the present invention, wherein the second single crystal piezoelectric layer is bonded to the Figure 7 A cross-sectional view of the state of the multiple layers shown.

[0022] Figure 9 This is a cross-sectional view showing a state after the upper surface of the second single-crystal piezoelectric layer is scraped off in the method for manufacturing the piezoelectric device according to the first embodiment of the present invention.

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

[0024] Figure 11 This is a cross-sectional view showing a state where a hole portion is formed in a laminated portion in the method for manufacturing a piezoelectric device according to the first embodiment of the present invention.

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

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

[0027] Figure 14 This is a cross-sectional view showing a state where extraction electrodes are formed in the method for manufacturing the piezoelectric device according to the first embodiment of the present invention.

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

[0029] Figure 16 It is a longitudinal sectional view of a piezoelectric device according to Embodiment 2 of the present invention. DETAILED DESCRIPTION

[0030] (Implementation Method 1)

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

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

[0033] In this embodiment, the base portion 110 is made of Si. However, the material constituting the base portion 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 laminated portion 120 includes a membrane portion Mb that covers the opening 113. The membrane portion Mb is a portion of the laminated portion 120 located inside the opening end of the opening 113 when viewed from a direction perpendicular to the one main surface 111.

[0036] As viewed from a direction perpendicular to one principal surface 111, a hole H is formed in the laminated portion 120 at a position 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 circumferential surface of the hole H. An extraction electrode 193 is provided inside the hole H. This extraction electrode 193 is insulated from the intermediate electrode layer 150 and connected to the lower electrode layer 160, and is led 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 portion 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 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 flat.

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

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

[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 a niobate compound or a tantalate compound of an alkali metal other than K and Na.

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

[0043] The 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. The upper and lower surfaces of the intermediate electrode layer 150 are each flat. The intermediate electrode layer 150 can also be formed by stacking two electrode layers. In this embodiment, the thickness of the intermediate electrode layer 150 is thinner than the thickness of each of the lower electrode layer 160 and the upper electrode layer 170. However, the thickness of the intermediate electrode layer 150 can also be greater than the thickness of each of the lower electrode layer 160 and the upper electrode layer 170.

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

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

[0046] The lower electrode layer 160 is arranged 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 a metal such as Al or Pt. Alternatively, the lower electrode layer 160 may be made of a conductive oxide such as LaNiO 3 , SrRuO 3 , or RuO 2 . Alternatively, the lower electrode layer 160 may be an epitaxial growth film formed by epitaxially growing a conductive material.

[0048] The upper electrode layer 170 is disposed on the second single crystal piezoelectric layer 140 and faces the intermediate electrode layer 150 via 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 composed of a metal such as Al or Pt. Alternatively, the upper electrode layer 170 may be an epitaxially grown film formed by epitaxially growing a conductive material. Alternatively, a bonding layer composed of Ti or the like may be disposed between the upper electrode layer 170 and the second single crystal piezoelectric layer 140.

[0050] Extraction electrode 193 is formed over the upper surface of second single crystal piezoelectric layer 140, the inner peripheral surface of insulating film 194, and the upper surface of a portion of lower electrode layer 160 exposed through hole H. Extraction electrode 193 is made of a metal such as Al or Pt. Insulating film 194 is made of an insulating material such as SiO2.

[0051] The laminated portion 120 further includes an intermediate layer 180. The intermediate layer 180 sandwiches the lower electrode layer 160 between itself and the first single crystal piezoelectric layer 130. An opening 183 is formed on the lower surface of the intermediate layer 180, communicating with the opening 113 of the base portion 110. The opening 183 is located above the opening 113. A portion of the lower surface of the lower electrode layer 160 is exposed through the opening 183. 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 made of SiO 2 . The material of the intermediate layer 180 is not limited to SiO 2 , and any insulating material may be used. For example, the intermediate layer 180 may be made of an organic material having electrical and thermal insulation properties.

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

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

[0055] In this embodiment, the opening 113 has a rectangular shape when viewed from a direction perpendicular to the main surface 111. However, the opening 113 may have a polygonal shape or a circular shape when viewed from a direction perpendicular to the main surface 111.

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

[0057] Hereinafter, a method for manufacturing the piezoelectric device according to the first embodiment of the present invention will be described.

[0058] Figure 2 This is a cross-sectional view showing a state in which a lower electrode layer is provided on the lower surface of a first single-crystal piezoelectric layer in the method for manufacturing a 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 negative on the upper surface side and positive on the lower surface side. The first single crystal piezoelectric layer 130 is made of a material that produces a difference in etching rate between the positive side and the negative side of the polarization charge.

[0060] like Figure 2 As shown, the lower electrode layer 160 is provided on the lower surface of the first single-crystal piezoelectric layer 130 by lift-off, plating, etching, or the like. When the lower electrode layer 160 is composed of a conductive oxide, the conductive oxide is formed on the lower surface of the first single-crystal piezoelectric layer 130 by reactive sputtering, by oxidizing the metal contained in the target. When the lower electrode layer 160 is an epitaxially grown film, the lower electrode layer 160 is provided by heteroepitaxially growing a conductive film on the lower surface of the first single-crystal piezoelectric layer 130 and patterning the conductive film.

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

[0062] Figure 4 In the method for manufacturing a piezoelectric device according to the first embodiment of the present invention, the base portion is bonded to the Figure 3 A cross-sectional view of the state of the multiple layers shown. Figure 5 This is a cross-sectional view showing a state after the base portion is bonded to the lower surface of the intermediate layer in the method for manufacturing the piezoelectric device according to the first embodiment of the present invention.

[0063] like Figure 4 and Figure 5 As shown, a substrate serving as the base 110 without the opening 113 is bonded to the lower surface of the intermediate layer 180 by surface activated bonding or atomic diffusion bonding. Alternatively, the base 110 may have the opening 113 formed therein beforehand.

[0064] Figure 6 1 is a cross-sectional view showing a state after the upper surface of the first single crystal piezoelectric layer is scraped off in the method for manufacturing the piezoelectric device according to the first embodiment of the present invention. Figure 6 As shown, the upper surface of the first single-crystal piezoelectric layer 130 is shaved off by CMP or the like, so that the first single-crystal piezoelectric layer 130 has a desired thickness. Alternatively, a peeling layer may be formed in advance on the upper surface side of the first single-crystal piezoelectric layer 130 by ion implantation. In this case, the peeling layer is peeled off before the upper surface of the first single-crystal piezoelectric layer 130 is shaved off by cutting or CMP or the like, 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 so that the desired excitation of the first single-crystal piezoelectric layer 130 by application of a voltage can be obtained.

[0065] Figure 7 1 is a cross-sectional view showing a state where an intermediate electrode layer is provided on the upper surface of the first single crystal piezoelectric layer in the method for manufacturing a piezoelectric device according to the first embodiment of the present invention. Figure 7 As shown, the intermediate electrode layer 150 is provided on the upper surface of the first single crystal piezoelectric layer 130 by lift-off, plating, etching, or the like.

[0066] In the case where the intermediate electrode layer 150 is composed of Si with 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 activated bonding or atomic diffusion bonding, and then the upper surface of the Si substrate is shaved off by CMP or the like to obtain the desired thickness. Alternatively, a peeling layer may be formed in advance on the upper surface side of the Si substrate by ion implantation. In this case, the peeling layer is peeled off before the upper surface of the Si substrate is shaved off by cutting or CMP, thereby facilitating the adjustment of the thickness of the Si substrate. In the case where the intermediate electrode layer 150 is composed of a conductive oxide, a conductive oxide obtained by oxidizing the metal contained in the target is formed into a film on the upper surface of the first single crystal piezoelectric layer 130 by reactive sputtering, thereby providing the intermediate electrode layer 150.

[0067] Figure 8 The present invention is a method for manufacturing a piezoelectric device according to the first embodiment of the present invention, wherein the second single crystal piezoelectric layer is bonded to the Figure 7 A cross-sectional view of the state of the multiple layers shown. 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 activated 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 positive on the upper surface side and negative on the lower surface side. The second single crystal piezoelectric layer 140 is made of a material that produces a difference in etching rate between the positive and negative sides of the polarization charge.

[0069] Figure 9 : is a cross-sectional view showing a state after the upper surface of the second single crystal piezoelectric layer is scraped off in the method for manufacturing the piezoelectric device according to the first embodiment of the present invention. Figure 9 As shown, the upper surface of the second single-crystal piezoelectric layer 140 is shaved off by CMP or the like, so that the second single-crystal piezoelectric layer 140 has a desired thickness. Alternatively, a peeling layer may be formed in advance on the upper surface side of the second single-crystal piezoelectric layer 140 by ion implantation. In this case, the peeling layer is peeled off before the upper surface of the second single-crystal piezoelectric layer 140 is shaved off by cutting or CMP or the like, 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 so that the desired excitation of the second single-crystal piezoelectric layer 140 by the application of voltage can be obtained.

[0070] Figure 101 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 method for manufacturing a piezoelectric device according to the first embodiment of the present invention. Figure 10 As shown, the upper electrode layer 170 is provided on the upper surface of the second single crystal piezoelectric layer 140 by lift-off, plating, etching, etc. In the case where the upper electrode layer 170 is an epitaxial growth film, the upper electrode layer 170 is provided by forming a conductive film on the upper surface of the second single crystal piezoelectric layer 140 by heteroepitaxial growth and patterning the conductive film.

[0071] Figure 11 1 is a cross-sectional view showing a state where a hole portion is formed in a laminated portion in the method for manufacturing a piezoelectric device according to the first embodiment of the present invention. Figure 11 As shown, a hole H is formed by etching through 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. Furthermore, a hole 141 is formed by etching through the second single crystal piezoelectric layer 140 to reach the intermediate electrode layer 150.

[0072] Hole H and hole 141 are each formed by etching from the upper surface of the second single-crystal piezoelectric layer 140. The second single-crystal piezoelectric layer 140 is made of a material that produces a difference in etching rate 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. Because the polarization charge of the second single-crystal piezoelectric layer 140 is positive on the upper surface side and negative on the lower surface side, etching from the upper surface side of the second single-crystal piezoelectric layer 140 can be performed at a low etching rate. This prevents hole 141 from penetrating the intermediate electrode layer 150 due to overetching.

[0073] In this embodiment, since the thickness of the intermediate electrode layer 150 is thinner than the thicknesses of the lower electrode layer 160 and the upper electrode layer 170 , the time required for etching the intermediate electrode layer 150 when forming the hole H can be shortened.

[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 a difference in etching rate between the positive and negative sides of the polarization charge. The etching rate when etching from the negative side of the polarization charge is higher than the etching rate when etching from the positive side of the polarization charge. Since the polarization charge of the first single-crystal piezoelectric layer 130 is negative on the upper surface side and positive on the lower surface side, the first single-crystal piezoelectric layer 130 can be etched at a high etching rate by etching from the upper surface side of the first single-crystal piezoelectric layer 130. As a result, the time required to etch the first single-crystal piezoelectric layer 130 when forming the hole H can be shortened.

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

[0076] Figure 13 1 is a cross-sectional view showing a state in which the central portion of the bottom of the insulating film is removed in the method for manufacturing the piezoelectric device according to the first embodiment of the present invention. Figure 13 As shown, by etching, a portion of the insulating film 194 located on the inner peripheral surface of the hole H is left, and a 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 1 is a cross-sectional view showing a state where extraction electrodes are formed in the method for manufacturing a piezoelectric device according to the first embodiment of the present invention. Figure 14 As shown, it 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, evaporation or plating.

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

[0079] Finally, by etching, the opening 113 is formed in the base 110, and the opening 183 is formed in the intermediate layer 180. In addition, the opening 183 is not necessarily formed. Figure 1 The piezoelectric device 100 according to the first embodiment of the present invention is shown.

[0080] The piezoelectric device 100 according to the first embodiment of the present invention includes a diaphragm portion Mb having 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 the intermediate electrode layer 150 and the upper electrode layer 170. This allows the piezoelectric device to increase its amplitude during excitation without increasing the area of ​​the single-crystal piezoelectric layer, compared to a piezoelectric device having only one single-crystal piezoelectric layer. Consequently, the amplitude of the piezoelectric device 100 during excitation can be increased while suppressing an increase in the area occupied by the piezoelectric device 100.

[0081] In the piezoelectric device 100 according to the first embodiment of the present invention, the first single-crystal piezoelectric layer 130 is formed of a material that produces a difference in etching rate between the positive and negative sides of the polarization charge. The polarization charge of the first single-crystal piezoelectric layer 130 is negative on the intermediate electrode layer 150 side and positive on the lower electrode layer 160 side. Consequently, when etching to form the hole H for electrical connection with the lower electrode layer 160, the first single-crystal piezoelectric layer 130 can be etched at a high etching rate, thereby shortening the time required to etch the first single-crystal piezoelectric layer 130. Consequently, it is possible to suppress a decrease in the production efficiency of the piezoelectric device 100 due to the provision of two single-crystal piezoelectric layers.

[0082] In the piezoelectric device 100 according to the first embodiment of the present invention, the thickness of the intermediate electrode layer 150 is thinner than the thicknesses of the lower electrode layer 160 and the upper electrode layer 170. This shortens the time required to etch the intermediate electrode layer 150 when forming the hole H, thereby suppressing a decrease in the production efficiency of the piezoelectric device 100.

[0083] In the piezoelectric device 100 according to the first embodiment of the present invention, the intermediate electrode layer 150 may be made of Si. In this case, since Si has stable crystals, it does not react with either the first single-crystal piezoelectric layer 130 or the second single-crystal piezoelectric layer 140. Therefore, it is possible to suppress degradation of the characteristics of each of the first single-crystal piezoelectric layer 130 and the second single-crystal piezoelectric layer 140 due to mutual reaction with the first single-crystal piezoelectric layer 130 and the second single-crystal piezoelectric layer 140.

[0084] In the piezoelectric device 100 according to the first embodiment of the present invention, the second single-crystal piezoelectric layer 140 is made of a material that produces a difference in etching rate between the positive and negative sides of the polarization charge. The polarization charge of the second single-crystal piezoelectric layer 140 is negative on the intermediate electrode layer 150 side and positive on the upper electrode layer 170 side. Therefore, etching from the upper surface of the second single-crystal piezoelectric layer 140 allows the second single-crystal piezoelectric layer 140 to be etched at a low etching rate. Consequently, the hole 141 penetrating the intermediate electrode layer 150 due to overetching can be prevented. Consequently, insufficient electrical connection between the intermediate electrode layer 150 and the second lead wiring 192 can be prevented, which could degrade the excitation characteristics of the piezoelectric device 100.

[0085] In the piezoelectric device 100 according to the first embodiment 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 or tantalate compound of an alkali metal other than K and Na, and are lead-free, thereby 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 the first embodiment of the present invention, at least one of the lower electrode layer 160 and the intermediate electrode layer 150 may be made of a conductive oxide. When the lower electrode layer 160 is made of a conductive oxide, when the hole H is formed by dry etching the first single-crystal piezoelectric layer 130, the etching selectivity between the first single-crystal piezoelectric layer 130 and the lower electrode layer 160 is increased, thereby preventing the formation of through-holes in the lower electrode layer 160 due to overetching. When the intermediate electrode layer 150 is made of a conductive oxide, when the hole 141 is formed by dry etching the second single-crystal piezoelectric layer 140, the etching selectivity between the second single-crystal piezoelectric layer 140 and the intermediate electrode layer 150 is increased, thereby preventing the formation of through-holes in the intermediate electrode layer 150 due to overetching.

[0087] In the piezoelectric device 100 according to the first embodiment 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. Epitaxially grown films have good crystallinity, thus suppressing the occurrence of migration and improving the power handling characteristics of each of the lower electrode layer 160 and the upper electrode layer 170.

[0088] (Implementation Method 2)

[0089] The following describes a piezoelectric device according to a second embodiment of the present invention with reference to the accompanying drawings. The piezoelectric device according to the second embodiment of the present invention differs from the piezoelectric device 100 according to the first embodiment of the present invention only in that a lower reinforcing electrode layer is provided. Therefore, description of the same structures as those of the piezoelectric device 100 according to the first embodiment of the present invention will not be repeated.

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

[0091] The reinforcement lower electrode layer 260 is made of a metal such as Al or Pt. Alternatively, the reinforcement lower electrode layer 260 may be made of a conductive oxide such as LaNiO3, SrRuO3, or RuO2. Alternatively, the reinforcement lower electrode layer 260 may be an epitaxial growth film formed by epitaxially growing a conductive material.

[0092] Specifically, the reinforcing lower electrode layer 260 is formed on the lower surface of the lower electrode layer 160 by lift-off, plating, or etching. If the reinforcing lower electrode layer 260 is composed of a conductive oxide, the reinforcing lower electrode layer 260 is formed by reactive sputtering by oxidizing the metal contained in the target to form a film of the conductive oxide on the lower surface of the lower electrode layer 160. If the reinforcing lower electrode layer 260 is an epitaxially grown film, the reinforcing lower electrode layer 260 is formed by forming a conductive film on the lower surface of the lower electrode layer 160 by homoepitaxial growth and patterning the conductive film.

[0093] In the piezoelectric device 200 involved in 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 portion H, it is possible to prevent 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 portion H is formed by etching.

[0094] In addition, when the formation of through holes caused by over-etching is prevented by making the lower electrode layer 160 thicker as a whole, warping occurs in the diaphragm portion Mb due to the stress generated in the lower electrode layer 160, and the excitation characteristics of the piezoelectric device are reduced. 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 reduction in the excitation characteristics of the piezoelectric device 200 due to the warping of the diaphragm portion Mb can be suppressed.

[0095] In the description of the above embodiments, combinable structures may be combined with each other.

[0096] The embodiments disclosed herein are to be considered in all respects as illustrative and non-restrictive. The scope of the present invention is indicated by the claims rather than the above description, and is intended to include all modifications within the meaning and scope equivalent to 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 wiring, 192: second lead wiring, 193: lead electrode, 194: insulating film, 260: lower electrode layer for reinforcement, Mb: diaphragm portion.

Claims

1. A piezoelectric device comprising: a base portion including one main surface and another main surface located on the opposite side to the one main surface, and having an opening formed in the one main surface; and a laminated portion that is laminated on the one main surface side of the base portion and covers the opening portion from above, The stacked portion includes, at least above the opening portion, a first single-crystal piezoelectric layer, a second single-crystal piezoelectric layer arranged above the first single-crystal piezoelectric layer, an intermediate electrode layer arranged between the first single-crystal piezoelectric layer and the second single-crystal piezoelectric layer, a lower electrode layer arranged on the lower side of the first single-crystal piezoelectric layer and opposite to the intermediate electrode layer across the first single-crystal piezoelectric layer, and an upper electrode layer arranged on the upper side of the second single-crystal piezoelectric layer and opposite to the intermediate electrode layer across the second single-crystal piezoelectric layer, and has a diaphragm portion as a portion covering the opening portion, When viewed from a direction perpendicular to the one main surface, a hole portion is formed in the stacked portion at a position outside the opening portion, penetrating the first single crystal piezoelectric layer, the intermediate electrode layer, and the second single crystal piezoelectric layer and reaching the lower electrode layer. An extraction electrode is provided inside the hole, the extraction electrode being insulated from the intermediate electrode layer and connected to the lower electrode layer, and being led out to the upper surface of the second single crystal piezoelectric layer. The first single crystal piezoelectric layer is made of a material that produces a difference in etching rate between the positive side and the negative side of the polarization charge. The polarization charge of the first single crystal piezoelectric layer is negative on the middle electrode layer side and positive on the lower electrode layer side. The second single-crystal piezoelectric layer is made of a material that produces a difference in etching rate between the positive side and the negative side of polarization charge.

2. The piezoelectric device according to claim 1, wherein The thickness of the intermediate electrode layer is thinner than the thickness of each of 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 polarization charge of the second single crystal piezoelectric layer is negative on the middle electrode layer side and positive on the upper electrode layer side.

5. The piezoelectric device according to claim 2, wherein The polarization charge of the second single crystal piezoelectric layer is negative on the middle electrode layer side and positive on the upper electrode layer side.

6. The piezoelectric device according to claim 3, wherein The polarization charge of the second single crystal piezoelectric layer is negative on the middle electrode layer side and positive 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 made of lithium niobate (LiNbO 3 ) or lithium tantalate (LiTaO 3 ).

8. The piezoelectric device according to claim 2, wherein The first single crystal piezoelectric layer and the second single crystal piezoelectric layer are each made of lithium niobate (LiNbO 3 ) or lithium tantalate (LiTaO 3 ).

9. The piezoelectric device according to claim 3, wherein The first single crystal piezoelectric layer and the second single crystal piezoelectric layer are each made of lithium niobate (LiNbO 3 ) or lithium tantalate (LiTaO 3 ).

10. The piezoelectric device according to claim 4, wherein The first single crystal piezoelectric layer and the second single crystal piezoelectric layer are each made of lithium niobate (LiNbO 3 ) or lithium tantalate (LiTaO 3 ).

11. The piezoelectric device according to claim 5, wherein The first single crystal piezoelectric layer and the second single crystal piezoelectric layer are each made of lithium niobate (LiNbO 3 ) or lithium tantalate (LiTaO 3 ).

12. The piezoelectric device according to claim 6, wherein The first single crystal piezoelectric layer and the second single crystal piezoelectric layer are each made of lithium niobate (LiNbO 3 ) or lithium tantalate (LiTaO 3 ).

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

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

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

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

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

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

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

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

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

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

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

24. The piezoelectric device according to claim 12, wherein At least one of the lower electrode layer and the intermediate electrode layer is made 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 below a portion of the lower electrode layer located below the hole.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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