JP2011124738A - Method of manufacturing piezoelectric device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a piezoelectric device capable of separating a piezoelectric substrate without problems even when several locations around the piezoelectric substrate are fixed with a fixation jig in manufacturing a piezoelectric composite substrate by a smart cut method. <P>SOLUTION: Manufacturing the piezoelectric device includes a step of forming a concave part at a location at which the fixation jig around the piezoelectric substrate is installed, a step of installing the fixation jigs at each of the plurality of concave parts to fix the piezoelectric substrate, a step of injecting ion from an ion injection surface of the piezoelectric substrate to form an ion injection layer inside the piezoelectric substrate, a step of bonding a supporting body to the ion injection surface of the piezoelectric substrate, a step of heating the piezoelectric substrate in which the ion injection layer is formed to separate a piezoelectric thin film from the piezoelectric substrate, and a step of generating a composite piezoelectric substrate comprising the piezoelectric thin film and the supporting body. The concave part becomes an ion non-injection part, and ion is injected into the separated part to reliably separate the thin film. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a piezoelectric device using a piezoelectric single crystal thin film.

  Currently, piezoelectric devices using single crystal materials having piezoelectricity are manufactured and used. Among them, there are SAW, F-BAR, and the like as piezoelectric devices. However, for the reason that it corresponds to a high-frequency Lamb wave device, an ultrathin film type piezoelectric device in which a piezoelectric material is further thinned has been developed. There are a plurality of methods of manufacturing a piezoelectric thin film for forming such an ultrathin film type piezoelectric device. For example, a method has been devised as shown in Patent Document 1.

The manufacturing method of the composite piezoelectric substrate described in Patent Document 1 uses a so-called smart cut method. In the smart cut method, for example, a LiNbO ₃ [lithium niobate] substrate (hereinafter referred to as an LN substrate) or a LiTaO ₃ [lithium tantalate] substrate (hereinafter referred to as an LT substrate) is used as the piezoelectric material. Thus, a composite piezoelectric substrate is generated by the following steps.

(1) By performing ion implantation on the piezoelectric substrate under predetermined conditions, an ion implantation layer is formed at a position where it is desired to form a piezoelectric thin film from the surface of the piezoelectric substrate.
(2) A support is bonded to the piezoelectric substrate on which the ion implantation layer is formed.
(3) By heating the composite member composed of the piezoelectric substrate and the support, the piezoelectric thin film is peeled from the piezoelectric substrate with the ion implantation layer as a peeling surface.
(4) Thereafter, various pattern electrodes are formed on the piezoelectric thin film.

International Publication No. 2009/081651 Pamphlet

  FIG. 1 is a manufacturing process diagram of a conventional piezoelectric device. In the smart cut method, before performing ion implantation by irradiating the piezoelectric substrate 301 with the ion beam 321, as shown in FIG. 1A, several places around the piezoelectric substrate 301 (three places in the figure) are fixed jigs. It is fixed with 311A-fixing jig 311C. When the piezoelectric substrate 301 is fixed with a jig in this way, as shown in FIG. 1B, during ion implantation, the ion beam is shielded in a part of the piezoelectric substrate 301 by the fixing jig 311A to the fixing jig 311C. Ion cannot be implanted. Therefore, as shown in FIG. 1C, when the piezoelectric thin film 303 is peeled after the piezoelectric substrate 301 is bonded to the support substrate 305, the portion of the ion implantation layer 302 is peeled off without any problem. However, the portion of the piezoelectric substrate 301 where ions could not be implanted does not peel off, and the piezoelectric substrate 301 is damaged together with the support substrate 305 as shown in FIG. 1D, or the piezoelectric substrate 301 is damaged as shown in FIG. There was a problem that the thin film 303 was bent in the middle and the end 301A became convex.

  Therefore, the present invention provides a method of manufacturing a piezoelectric device that can peel a piezoelectric substrate without any problem even when a piezoelectric composite substrate is manufactured by a smart cut method, even if several places around the piezoelectric substrate are fixed with a fixing jig. The purpose is to do.

  The present invention relates to a method for manufacturing a piezoelectric device. This method for manufacturing a piezoelectric device includes a recess forming step, a joining step, and a peeling step. In the recess forming step, the ion implantation surface is formed in a region corresponding to a non-implanted portion where ions are not implanted in the ion implantation surface with respect to the piezoelectric substrate in which the ion implantation layer is formed by ions implanted from the ion implantation surface. A recess deeper than the ion-implanted layer is generated on the basis of the above. In the bonding step, a support is bonded to the ion-implanted surface of the piezoelectric substrate after forming the recess and the ion-implanted layer. In the peeling process, the piezoelectric thin film is heated and peeled from the piezoelectric substrate to which the support is bonded.

  When the piezoelectric substrate is fixed with a jig, at the time of ion implantation, a part of the injection surface of the piezoelectric substrate is shielded by the fixing jig, so that this portion cannot be ion-implanted and becomes an ion non-implanted portion. In this manufacturing method, a recess deeper than the ion-implanted layer is generated with reference to the ion-implanted surface in a region corresponding to the non-implanted portion where ions are not implanted on the ion-implanted surface of the piezoelectric substrate. For this reason, the other portion of the ion implantation surface where the recess is not formed becomes an ion implantation portion, and since the recess is deeper than the ion implantation layer with respect to the ion implantation surface, the piezoelectric thin film is thermally peeled in the peeling process. Can be performed reliably. Further, since only the non-implanted portion of the ion is dug to form the recess, the effective area of the piezoelectric thin film that becomes the element after separation can be obtained to the maximum. Further, since the non-implanted portion of the piezoelectric substrate does not become a convex portion after the piezoelectric film is peeled off, the substrate remaining after the peeling can be reused.

  The present invention includes a fixing step and an ion implantation step. In the fixing step, a fixing jig is attached to the recess to fix the piezoelectric substrate. In the ion implantation step, ions are implanted from the ion implantation surface to form the ion implantation layer in the piezoelectric substrate. And it has a recessed part formation process in the front | former stage of a fixing process, and has a joining process in the back | latter stage of an ion implantation process.

  In this manufacturing method, the recess forming step, the fixing step, the ion implantation step, the bonding step, and the peeling step are performed in this order. In this manufacturing method, the portion where the concave portion of the ion implantation surface is formed can be an ion non-implanted portion, and the other portion of the ion implanted surface is an ion implanted portion, so that the piezoelectric thin film can be reliably separated. it can.

  The present invention includes a fixing step and an ion implantation step. In the fixing step, a fixing jig is attached to the recess to fix the piezoelectric substrate. In the ion implantation step, ions are implanted from the ion implantation surface to form the ion implantation layer in the piezoelectric substrate. And it has a recessed part formation process in the back | latter stage of an ion implantation process.

  In this manufacturing method, the fixing step, the ion implantation step, the recess forming step, the joining step, and the peeling step are performed in this order. In this manufacturing method, a part of the injection surface of the piezoelectric substrate is shielded by a fixing jig, and a recess is formed in an ion non-implanted portion where ions cannot be implanted, so that the conventional fixing jig is not modified. Since the ion non-implanted portion is removed at the time of peeling, the thin film can be reliably separated.

  In this invention, the recess forming step includes a step of forming a non-mask portion by photolithography and a step of forming a recess in the non-mask portion by etching. In this manufacturing method, the concave portion can be formed with high accuracy by forming the non-mask portion by photolithography. In addition, since the portions other than the non-mask portion that forms the recess are masked with the resist, damage to the surface of the piezoelectric substrate can be suppressed when the recess is formed by etching.

  In the present invention, the piezoelectric substrate is made of lithium tantalate or lithium niobate. Piezoelectric substrates made of lithium tantalate or lithium niobate are fragile and easily cracked, but this manufacturing method forms a recess in the non-ion-implanted portion, so that the piezoelectric substrate may be cracked when heat-peeled after ion implantation. It can be peeled off smoothly. Further, since the peeled piezoelectric substrate can be reused, a plurality of piezoelectric devices can be manufactured from one piezoelectric substrate, and an expensive piezoelectric substrate can be saved.

  According to the present invention, when a piezoelectric composite substrate is manufactured by the smart cut method, even if several places around the piezoelectric substrate are fixed with a fixing jig to form an ion non-implanted portion, the piezoelectric substrate is peeled off without any problem. it can.

It is a manufacturing process figure of the conventional piezoelectric device. It is a flowchart which shows the manufacturing method of the thin film type piezoelectric device which concerns on the 1st Embodiment of this invention. It is a figure which shows typically the manufacturing process of the thin film type piezoelectric device formed with the manufacturing flow shown in FIG. It is a figure which shows typically the manufacturing process of the thin film type piezoelectric device formed with the manufacturing flow shown in FIG. It is a figure which shows typically the manufacturing process of the thin film type piezoelectric device formed with the manufacturing flow shown in FIG. It is a figure which shows typically the manufacturing process of the thin film type piezoelectric device formed with the manufacturing flow shown in FIG. It is a flowchart which shows the manufacturing method of the thin film type piezoelectric device which concerns on 2nd Embodiment of this invention. It is a figure which shows typically the manufacturing process of the thin film type piezoelectric device formed with the manufacturing flow shown in FIG. It is a figure which shows typically the manufacturing process of the thin film type piezoelectric device formed with the manufacturing flow shown in FIG.

  A method for manufacturing a piezoelectric device according to a first embodiment of the present invention will be described with reference to a schematic diagram of a manufacturing process of a piezoelectric device along the steps shown in the flowchart. In the following description, a thin film type piezoelectric device for F-BAR using a piezoelectric single crystal material (hereinafter referred to as a piezoelectric single crystal substrate) will be described as an example of the piezoelectric device.

  FIG. 2 is a flowchart showing a method for manufacturing a thin film piezoelectric device according to the first embodiment of the present invention. 3-6 is a figure which shows typically the manufacturing process of the thin film type piezoelectric device formed with the manufacturing flow shown in FIG.

  In the present embodiment, before the periphery of the piezoelectric single crystal substrate is fixed by the fixing jig, a recess for attaching the fixing jig is formed in the piezoelectric single crystal substrate. First, a piezoelectric single crystal substrate 1 having a predetermined thickness is prepared. As shown in FIG. 3A, a resist film 14 is formed on one surface 12 of the piezoelectric single crystal substrate 1 that becomes the gap side when the membrane structure is formed (FIG. 2: S101).

  As shown in FIG. 3B, non-mask portions 15A to 15C are formed in the resist film 14 on the outer peripheral portion of the one surface 12 by photolithography (FIG. 2: S102). The non-mask portion 15A to the non-mask portion 15C are for creating the concave portion, and are approximately the same size as the tip portion of the fixing jig so that the fixing jig can be inserted into the concave portion. By using the photolithography method as described above, the non-mask portion can be formed with high accuracy.

  As shown in FIG. 3C, the non-mask portion 15A to the non-mask portion 15C are dug by the RIE (Reactive Ion Etching) method to form the concave portions 16A to 16C. The resist film 14 is completely removed (FIG. 2: S103). The recesses 16A to 16C are generated deeper than the ion implantation layer 100 formed in step S105, which will be described later, with the one surface 12 (ion implantation surface) as a reference. Since the portion other than the non-mask portion that forms the recess is masked with a resist, damage to the surface of the piezoelectric substrate can be suppressed when the recess is formed by etching.

  As shown in FIGS. 3D and 3E, fixing jigs 21A to 21C are attached to the recesses 16A to 16C to fix the piezoelectric single crystal substrate 1 (FIG. 2: S104).

As shown in FIG. 3E, hydrogen ions are implanted from one side 12 (corresponding to an ion implantation surface) to form an ion implantation layer 100 in the piezoelectric single crystal substrate 1 (FIG. 2: S105). For example, when an LT substrate is used as the piezoelectric single crystal substrate 1 and hydrogen ion implantation is performed with an implantation energy of 150 keV and a dose (ion implantation density) of 9.0 × 10 ¹⁶ atoms / cm ² , the depth from the one surface 12 is approximately An ion implantation layer 100 in which hydrogen ions are distributed at a position of 1 μm is formed. In addition to the LT substrate, an LN substrate, an LBO (Li ₂ B ₄ O ₇ ) substrate, or a langasite (La ₃ Ga ₅ SiO ₁₄ ) substrate may be used as the piezoelectric single crystal substrate 1. Ion implantation is performed under the conditions. In addition, the implanted ions may be changed to helium ions, argon ions, or the like depending on the type of substrate.

  In the above process, steps S104 to S105 may be performed first, and then steps S101 to S103 may be performed. That is, the piezoelectric single crystal substrate 1 is first fixed with a fixing jig as shown in FIG. 1A, and ion implantation is performed as shown in FIG. 1B. Subsequently, as shown in FIG. 3A, a resist film 14 is formed on one surface 12 of the piezoelectric single crystal substrate 1. Further, the non-mask portion 15A to the non-mask portion 15C are formed by the photolithography method in the portion where the fixing jigs 21A to 21C on the one surface 12 of the piezoelectric single crystal substrate 1 are overlapped and ions cannot be implanted. Then, as shown in FIG. 3C, the non-mask portion 15A to the non-mask portion 15C are dug by the RIE (Reactive Ion Etching) method to form the recesses 16A to 16C. Subsequently, all the resist film 14 is removed. Thereby, it is possible to prevent the piezoelectric substrate from being damaged or broken during peeling without modifying the fixing jig.

  As shown in FIG. 4A, a lower electrode 20 having a predetermined thickness is formed on one surface 12 of the piezoelectric single crystal substrate 1 after the ion implantation layer 100 is formed (FIG. 2: S106). The electrode material may be Mo, W, Al, Ni, or a multilayer structure thereof in accordance with required device characteristics. Moreover, it is good to form using EB vapor deposition, sputtering, CVD, etc. according to the kind of electrode material.

  A diffusion prevention layer 30A is formed on one surface 12 on which the lower electrode 20 is formed (FIG. 2: S107). A material that suppresses diffusion between the sacrificial layer material such as SiN, the piezoelectric film, and the lower electrode 20 may be selected for the diffusion preventing layer 30A.

A sacrificial layer 40 and a sacrificial layer 41 are formed on the diffusion preventing layer 30A (FIG. 2: S108). The sacrificial layer 40 and the sacrificial layer 41 may be made of any material that can remove only the sacrificial layer 40 and the sacrificial layer 41 without affecting the diffusion preventing layer 30 </ b> A by a removal process described later. As a material of the sacrificial layer 40 and the sacrificial layer 41, Cu, Al, Ni, ZnO, W, Mo, SiO ₂ or the like is used. The sacrificial layer 40 and the sacrificial layer 41 are preferably formed by EB vapor deposition, sputtering, CVD, or the like depending on the type of material.

A membrane support layer 32B is formed on the sacrificial layer 40 and the sacrificial layer 41, and the surface of the membrane support layer 32B is planarized by CMP (Chemical Mechanical Planarization) (FIG. 2: S109). As a material for the membrane support layer 32B, SiO ₂ , SiN, or the like is used. Further, the stress of the thin film, which causes film peeling, should be kept as low as possible.

A support substrate 30B (corresponding to a support) is prepared. As the material of the support substrate 30B, LT (LiTaO ₃ ), LN (LiNbO ₃ ), Si, glass, or the like is used. Then, the membrane support layer 32B and the support substrate 30B are directly bonded in a vacuum using a cleaning bonding technique to generate the composite piezoelectric substrate 2 as shown in FIG. 4C (FIG. 2: S110). . Clean bonding is a bonding method in which Ar ions or the like are irradiated in a vacuum and the bonding surfaces are activated, and does not require heating.

  The composite piezoelectric substrate 2 is heated in a reduced pressure atmosphere (FIG. 2: S111). At this time, a microcavity is generated along the surface of the ion-implanted layer into which hydrogen ions are implanted (depth of 1 μm from the surface of the LT substrate), and this cavity is grown by heating, as shown in FIG. In addition, the composite piezoelectric substrate 2 including the piezoelectric thin film 10 having a thickness of 1 μm and the piezoelectric single crystal substrate (LT substrate) 1 (not shown) are separated. As described above, since the concave portions 16A to 16C are formed in the outer peripheral portion of the piezoelectric single crystal substrate 1 in step S3, the piezoelectric thin film 10 is smoothly separated without damaging the piezoelectric single crystal substrate 1.

  The surface of the piezoelectric thin film 10 of the composite piezoelectric substrate 2 and the surface of the piezoelectric single crystal substrate 1 from which the piezoelectric thin film 10 has been peeled are rough with a mean square roughness (RMS roughness) of about 1 to 10 nm. Therefore, the surface is polished and smoothed by about 100 nm by CMP to form a mirror surface (FIG. 2: S112). Thus, the characteristic of a piezoelectric device can be improved by making a piezoelectric material surface into a mirror surface.

  The piezoelectric single crystal substrate 1 from which the piezoelectric thin film 10 has been peeled is reused as a material for creating another composite piezoelectric substrate 2.

  The composite piezoelectric substrate 2 is subjected to a substrate heating process for restoring piezoelectricity (FIG. 2: S113). For example, a conductive liquid such as a lithium chloride solution is applied to the other surface 13 of the piezoelectric thin film 10 to form a liquid polarization upper electrode 50 (not shown). Then, the polarization upper electrode 50 and the sacrificial layers 40 and 41 are connected by an electric field application circuit 55 (not shown), and a pulse electric field is applied. Thereby, the polarization treatment is performed on the piezoelectric thin film 10 between the polarization upper electrode 50 and the sacrificial layers 40 and 41, particularly between the polarization upper electrode 50 and the sacrificial layer 40.

Heating at 450 ° C. or higher is desirable in order to relieve the distortion of crystals received by ion implantation. Moreover, in order to take crystal distortion, it is desirable to make it 100 degreeC or more lower than Curie temperature in order to avoid cancellation of polarization. In the case where the piezoelectric thin film 10 is an LT substrate, the implanted ions H ⁺ substituted for the Li sites are removed during the ion implantation, and the piezoelectricity is restored by returning Li to the sites.

  Upper electrode patterns such as the upper electrode 60 and the pad electrode 61 are formed on the other surface 13 of the piezoelectric thin film 10 (FIG. 2: S114). As with the lower electrode 20, the electrode material may be selected according to the required device characteristics.

  Next, as shown in FIG. 5A, a resist film 70 is formed on the surface of the piezoelectric thin film 10 on which the upper electrode 60 is formed (FIG. 2: S115). Then, using a photolithography technique, as shown in FIG. 5B, an etching window 71 for removing the sacrificial layers 40 and 41 is formed in the resist film 70 (FIG. 2: S116). In FIG. 5, the etching window is formed only at the position of the sacrificial layer 40. However, an etching window may be further formed at a position between the adjacent piezoelectric devices in the sacrificial layer 41.

  Next, by introducing an etching gas or an etchant from the etching window 71, the sacrificial layer 40 and the sacrificial layer 41 are removed as shown in FIG. 5C (FIG. 5: S117). As a result, the space in which the sacrificial layer 40 corresponding to the region where the lower electrode 20 and the upper electrode 60 of the single thin film type piezoelectric device are formed becomes a void 80. It is preferable to select a wet etching solution or etching gas that does not affect the piezoelectric membrane, the upper electrode 60, and the lower electrode 20.

  After the sacrificial layers 40 and 41 are removed, the resist film 70 is removed as shown in FIG. 5D (FIG. 1: S118).

  Next, as shown in FIG. 6A, bumps 90 are formed on the pad electrode 61 (FIG. 1: S119). Then, as shown in FIG. 6B, individual thin film piezoelectric devices are cut out from the multi state. By such a manufacturing process, an F-BAR type thin film piezoelectric device can be manufactured.

  Next, a method for manufacturing a piezoelectric device according to a second embodiment of the present invention will be described with reference to a schematic diagram of the manufacturing process of the piezoelectric device along the steps shown in the flowchart.

  In the following description, as a piezoelectric device, a plate wave device having vibration displacement on both surfaces of a piezoelectric single crystal material (hereinafter referred to as a piezoelectric single crystal substrate) and generating a wave propagating in a plane direction will be described as an example. To do.

  FIG. 7 is a flowchart showing a method for manufacturing a thin film piezoelectric device according to the second embodiment of the present invention. 8 and 9 are diagrams schematically showing the manufacturing process of the thin film piezoelectric device formed by the manufacturing flow shown in FIG.

  In the piezoelectric device manufacturing method according to the second embodiment, the steps (steps S201 to S205) until the ion implantation layer 100 is formed are the same as steps S101 to S105 of the piezoelectric device manufacturing method according to the first embodiment. is there.

  That is, as shown in FIG. 3A, a resist film 14 is formed on one surface 12 of the piezoelectric single crystal substrate 1 (FIG. 7: S201).

  As shown in FIG. 3B, non-mask portions 15A to 15C are formed in the resist film 14 on the outer peripheral portion of the one surface 12 by photolithography (FIG. 7: S202). The non-mask portion 15A to the non-mask portion 15C are for creating the concave portion, and are approximately the same size as the tip portion of the fixing jig so that the fixing jig can be inserted into the concave portion. By using the photolithography method as described above, the non-mask portion can be formed with high accuracy.

  As shown in FIG. 3C, recesses 16A to 16C are formed in the non-mask portions 15A to 15C by RIE (Reactive Ion Etching), and the resist film 14 is removed (FIG. 7: S203). ). The recesses 16A to 16C are generated deeper than the ion implantation layer 100 formed in step S205, which will be described later, with the one surface 12 (ion implantation surface) as a reference. Since the portion other than the non-mask portion that forms the recess is masked with a resist, damage to the surface of the piezoelectric substrate can be suppressed when the recess is formed by etching.

  As shown in FIGS. 3D and 3E, the fixing jig 21A to the fixing jig 21C are attached to the recesses 16A to 16C to fix the piezoelectric single crystal substrate 1 (FIG. 7: S204). .

  As shown in FIG. 3E, hydrogen ions are implanted from the one surface 12 side to form the ion implantation layer 100 in the piezoelectric single crystal substrate 1 (FIG. 7: S205).

  In the above steps, similarly to the first embodiment, steps S204 to S205 may be performed first, and then steps S201 to S203 may be performed.

As shown in FIG. 8A, a sacrificial layer 45 having a predetermined thickness is formed on one surface 12 of the piezoelectric single crystal substrate 1 (FIG. 7: S206). The material of the sacrificial layer 45, Cu, Al, Ni, ZnO, W, Mo, or the like SiO _2, EB evaporation suit material species, sputtering, when formed using a CVD.

As shown in FIG. 8B, a membrane support layer 33B is formed on the sacrificial layer 45 and the one surface 12 of the piezoelectric single crystal substrate 1, and planarization is performed by CMP (S207). At this time, SiO ₂ or SiN is used as the membrane support layer 33B. The membrane support layer 33B is formed under a reduced pressure atmosphere. The stress of the thin film that causes film peeling should be kept as low as possible.

  As shown in FIG. 8C, the support substrate 35B is bonded to the membrane support layer 33B (FIG. 7: S208).

  Next, as shown in FIG. 8D, the composite piezoelectric substrate 3 composed of the piezoelectric single crystal substrate 1 on which the membrane support layer 33B and the support substrate 35B are disposed is heated, and the ion implantation layer 100 is used as a release surface. Peeling is performed (FIG. 7: S209). As a result, the piezoelectric thin film 10 with the sacrificial layer 45 supported by the support substrate 35B and provided with the membrane support layer 33B and the piezoelectric single crystal substrate (LT substrate) 1 (not shown) are separated. At this time, the heating temperature can be lowered by heating in a reduced pressure atmosphere.

  Next, the other surface 13 of the piezoelectric thin film 10 thus peeled and the surface of the piezoelectric single crystal substrate 1 from which the piezoelectric thin film 10 has been peeled are polished by CMP or the like so that the surface roughness Ra becomes 1 nm or less. Flattening is performed (FIG. 7: S210). Thereby, the characteristic of an elastic wave device can be improved.

  The piezoelectric single crystal substrate 1 from which the piezoelectric thin film 10 has been peeled is reused as a material for creating another composite piezoelectric substrate 3.

  Subsequently, polarization electrodes are formed on the upper and lower surfaces of the composite piezoelectric substrate 3 including the piezoelectric thin film 10, the membrane support layer 33B, and the support substrate 35B, and a polarization process is performed by applying a predetermined voltage. Is recovered (FIG. 7: S211). At this time, the sacrificial layer 45 may be used as a conductive material for a polarization electrode.

  After passing through the steps so far, the composite is annealed (FIG. 7: S212). By performing such an annealing treatment, the crystallinity of the piezoelectric thin film 10 that has undergone crystal damage in the ion implantation process can be recovered, and the elongation and warpage of the piezoelectric thin film 10 are suppressed. Thereby, even if the void 85 is formed in the subsequent removal process of the sacrificial layer 45, damage to the portion of the piezoelectric thin film 10 (piezoelectric membrane portion) in contact with the void 85 can be suppressed.

  Next, as shown in FIG. 8E, the IDT electrode 50P, the routing electrodes 51L1, 51L2 (not shown), and the pad electrodes 51U, 51UD, 51C (not shown) are provided on the other surface 13 of the piezoelectric thin film 10. It forms (FIG. 7: S213). The electrode material may be Al, Ni, Cr, Cu, Ti, Pt, or a multilayer structure thereof in accordance with the required device characteristics. It is good to form using EB vapor deposition, sputtering, etc. according to the kind of material.

  As shown in FIG. 9A, a predetermined film thickness is formed on each of the pad electrodes 51U, 51UD, 51C and on the other surface 13 of the piezoelectric thin film 10 excluding the gaps 85 by using sputtering, photolithography, dry etching or the like. A protective layer (dielectric layer) 75 is formed. In this case, at least the IDT electrode 50P is covered with the protective layer 75. The pad electrodes 51U, 51UD, 51C are formed so as to be exposed from the protective layer 75 (FIG. 7: S214).

  Next, as shown in FIG. 9A, an etching window 76 for removing the sacrificial layer 45 is formed in the piezoelectric thin film 10 (FIG. 7: S215). At this time, the etching window 76 is formed near the end of the sacrificial layer 45 formation region in the piezoelectric thin film 10. The etching window 76 is formed by dry etching using, for example, photolithography. For this dry etching, NLD (Neutral Loop Discharge) -RIE or SWP (Surface Wave Plasma) -RIE may be used.

  Next, the sacrificial layer 45 is removed by flowing an etching gas or an etchant through the etching window 76 (FIG. 7: S216). As a result, the space in which the sacrificial layer 45 is formed becomes a void 85 as shown in FIG.

  Then, bumps are formed on the pad electrodes 51U, 51UD, and 51C, and solder balls 95 are formed on the bumps (FIG. 7: S217). In this manner, a piezoelectric device of an elastic wave device using Lamb waves, plate waves, or the like is formed.

  By using the manufacturing method as described above, the piezoelectric thin film 10, the membrane support layer 33 </ b> B, and the support substrate 35 </ b> B described above are layered, and a piezoelectric device having a membrane structure can be manufactured with high reliability and excellent characteristics. Furthermore, the piezoelectric device can be manufactured without increasing the process load.

  Further, when lithium tantalate or lithium niobate is used as the material of the piezoelectric substrate, the piezoelectric substrate is brittle and easily cracked. However, in the above manufacturing method, since the concave portion is formed in the non-ion-implanted portion, the piezoelectric substrate is not cracked when the heat-separation is performed after the ion implantation, and can be smoothly separated. Moreover, since the peeled piezoelectric substrate can be reused as described above, a plurality of piezoelectric devices can be manufactured from one piezoelectric substrate, and an expensive piezoelectric substrate can be saved.

  In addition, the manufacturing method of the piezoelectric device which concerns on embodiment of this invention is applicable to various piezoelectric devices other than F-BAR and a plate wave device. For example, it can be applied to a piezoelectric vibration motor, a gyro, and the like.

1-piezoelectric single crystal substrate, 2,3-composite piezoelectric substrate, 10-piezoelectric thin film, 15A-15C-non-mask part, 16A-16C-recess, 20-lower electrode, 21A-21C-fixing jig, 30A-diffusion Prevention layer, 40, 41, 45-sacrificial layer, 60-upper electrode, 70-resist film, 71,76-etching window, 75-protection layer, 90-bump, 100-ion implantation layer

Claims (5)

A method of manufacturing a piezoelectric device comprising a piezoelectric thin film supported by a support,
With respect to a piezoelectric substrate in which an ion implantation layer is formed by ions implanted from the ion implantation surface, a region corresponding to an ion non-implanted portion where ions are not implanted on the ion implantation surface, with reference to the ion implantation surface. A recess forming step for generating a recess deeper than the ion implantation layer;
A bonding step of bonding a support to the ion-implanted surface of the piezoelectric substrate after forming the recess and the ion-implanted layer;
A peeling step of thermally peeling the piezoelectric thin film from the piezoelectric substrate to which the support is bonded;
A method of manufacturing a piezoelectric device having A fixing step of fixing the piezoelectric substrate by attaching a fixing jig to the recess;
An ion implantation step of implanting ions from the ion implantation surface to form the ion implantation layer in the piezoelectric substrate;
Have
2. The method of manufacturing a piezoelectric device according to claim 1, wherein the concave portion forming step is provided before the fixing step, and the joining step is provided after the ion implantation step. A fixing step of fixing the piezoelectric substrate by attaching a fixing jig to the outer periphery of the ion implantation surface;
An ion implantation step of implanting ions from the ion implantation surface to form an ion implantation layer in the piezoelectric substrate;
The method for manufacturing a piezoelectric device according to claim 1, further comprising the step of forming the recesses after the ion implantation step. The recess forming step includes
Forming a non-mask portion by photolithography,
Forming a recess in the non-mask portion by etching;
A method for manufacturing a piezoelectric device according to claim 1, comprising:   The method for manufacturing a piezoelectric device according to claim 1, wherein the piezoelectric substrate is made of lithium tantalate or lithium niobate.

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