JP2009267665A - Acoustic wave element, and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of an acoustic wave element on which a film for temperature compensation for suppressing variation of characteristics by temperature variation is formed, by which the film for temperature compensation is easily formed without causing complicatedness in a manufacturing process so much, and which can be miniaturized. <P>SOLUTION: The manufacturing method of the acoustic wave element is provided with processes of: preparing a piezoelectric wafer 1 having first and second main surfaces 1a, 1b opposite to each other; forming an IDT electrode 4 on the first main surface 1a of the piezoelectric wafer 1; forming the film for temperature compensation by an SOG method on the second main surface 1b; and dividing the piezoelectric wafer into a plurality of piezoelectric substrates. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an acoustic wave device used for, for example, a resonator, a bandpass filter, and the like, and a manufacturing method thereof. The present invention relates to an acoustic wave device provided with

Conventionally, acoustic wave elements have been widely used for resonators, bandpass filters, and the like. Surface acoustic wave elements are broadly classified into surface acoustic wave elements using surface acoustic waves and boundary acoustic wave elements using boundary acoustic waves. The acoustic wave element has a piezoelectric substrate and an IDT electrode formed on the piezoelectric substrate. A piezoelectric single crystal such as LiTaO ₃ or LiNbO ₃ is used as the piezoelectric substrate. LiTaO _{3 has} a thermal expansion coefficient of about 16 × 10 ⁻⁶ / K, and LiNbO _{3 has} a large thermal expansion coefficient of about 15 × 10 ⁻⁶ / K. For this reason, when LiTaO ₃ or LiNbO ₃ is used as the piezoelectric substrate, the change in frequency characteristics due to temperature change tends to be large. Therefore, conventionally, temperature compensation is performed by various methods so as to reduce the change of the frequency characteristic due to temperature.

  FIG. 11 is a front sectional view of a surface acoustic wave element provided with a conventional temperature compensation structure.

  The surface acoustic wave element 1001 includes a piezoelectric substrate 1002 and an inorganic thin film layer 1003 formed on the piezoelectric substrate 1002. An IDT electrode 1004 is formed on the inorganic thin film layer 1003.

The piezoelectric substrate 1002 is made of a piezoelectric single crystal such as LiTaO ₃ or LiNbO ₃ . Inorganic thin layer 1003 is composed of SiO _2. Since the inorganic thin film layer 1003 is made of SiO ₂ having a positive frequency temperature characteristic and LiTaO ₃ and LiNbO ₃ have a negative frequency temperature characteristic, changes in the frequency characteristic due to temperature are reduced.

On the other hand, the following Patent Document 2 discloses a surface acoustic wave device shown in FIG. In the surface acoustic wave device 1101, a surface acoustic wave element 1103 is accommodated in a package 1102. The surface acoustic wave element 1103 includes a piezoelectric substrate 1104 made of a piezoelectric single crystal such as LiTaO ₃ or LiNbO ₃ . An IDT electrode 1105 is formed on the lower surface of the piezoelectric substrate 1104.

An insulating substrate 1107 made of an insulating material such as alumina is bonded to the upper surface of the piezoelectric substrate 1104 with an adhesive 1106 made of a vitreous body. Since the heat capacity of the insulating substrate 1107 is larger than the heat capacity of the piezoelectric substrate 1104, pyroelectric breakdown of the IDT electrode is unlikely to occur. In Patent Document 2, the linear expansion coefficient of the adhesive 1106 made of a vitreous body and the linear expansion coefficient of the insulating substrate 1107 are 4 to 8 × 10 ⁻⁶ m / ° C., and the linear expansion coefficient of the piezoelectric substrate 1104 is It is described that the temperature characteristics are improved by being different from 10 to 40 × 10 ⁻⁶ m / ° C. That is, it is described that due to the difference in coefficient of linear expansion, the stress due to temperature change changes the surface wave propagation wavelength on the surface of the piezoelectric substrate 1104 where the IDT electrode 1105 is formed, thereby improving the temperature characteristics. Yes.
JP-A-6-326553 JP 2002-16468 A

In the surface acoustic wave element 1001 described in Patent Document 1, an inorganic thin film layer 1003 for temperature compensation made of SiO ₂ or the like is formed on the surface side of the piezoelectric substrate 1002 on which the IDT electrode 1004 is formed. Therefore, prior to the formation of the IDT electrode 1004, a process of forming the inorganic thin film layer 1003 had to be performed during manufacture. Therefore, the manufacturing process is complicated and the cost tends to be high.

  In the surface acoustic wave element 1103 described in Patent Document 2, the insulating substrate 1107 is bonded to the surface of the piezoelectric substrate 1104 opposite to the surface on which the IDT electrode 1105 is formed via the adhesive 1106. It was necessary to carry out a complicated process.

  Therefore, the manufacturing process is complicated and the cost tends to be high.

  In addition, since the insulating substrate 1107 made of alumina or the like is laminated on the piezoelectric substrate 1104 with an adhesive 1106, the surface acoustic wave element 1103 is thick, and the surface acoustic wave element can be reduced in size and size. There was a problem that it was difficult to turn off.

  The object of the present invention is to overcome the above-mentioned drawbacks of the prior art and to make it possible to reduce the thickness even though a temperature compensation material capable of reducing the change in characteristics due to a temperature change can be promoted. It is an object of the present invention to provide a surface acoustic wave element that can be manufactured in a simple manufacturing process and that can reduce costs, and a method for manufacturing the same.

  The acoustic wave device of the present invention includes a piezoelectric substrate having first and second main surfaces facing each other, an IDT electrode provided on the first main surface of the piezoelectric substrate, and the second of the piezoelectric substrate. And a temperature compensation film formed by SOG on the main surface of the substrate.

The temperature compensating film is formed of a material having various temperature compensating actions, but is preferably formed of a silicon oxide film. Since a piezoelectric single crystal such as LiTaO ₃ or LiNbO ₃ has a negative frequency temperature coefficient, a change in frequency characteristics due to a temperature change as a whole can be reduced by using a silicon oxide film having a positive frequency temperature coefficient. it can.

  The method for manufacturing an acoustic wave device according to the present invention is a method for manufacturing an acoustic wave device, comprising: preparing a piezoelectric wafer having first and second main surfaces facing each other; A step of forming an IDT electrode on the main surface, a step of forming a temperature compensation film on the second main surface of the piezoelectric wafer by an SOG method, and a step of dividing the piezoelectric wafer into a plurality of piezoelectric substrates. It is characterized by.

  In a specific aspect of the method for manufacturing an acoustic wave device according to the present invention, a step of forming a frame having a predetermined thickness on the second main surface side of the piezoelectric wafer, and a portion surrounded by the frame The method further includes the step of filling the temperature compensation film forming material by the SOG method and the step of forming the temperature compensation film by firing the filled temperature compensation film forming material. In this case, the temperature compensation film can be formed simply by filling the portion surrounded by the frame with the temperature compensation film forming material by the SOG method and baking it. That is, the temperature compensation film can be formed by a simple process. Further, the thickness of the temperature compensating film can be easily controlled only by controlling the thickness of the frame.

  In another specific aspect of the method for manufacturing an acoustic wave device according to the present invention, the frame is formed by patterning a resin by photolithography, whereby the frame made of a resin pattern material is the second It is formed on the main surface. In this case, the frame can be formed easily and with high accuracy.

  In still another specific aspect of the method of manufacturing an acoustic wave device according to the present invention, the recess is formed by injecting a temperature compensation film forming material into the second main surface of the piezoelectric wafer. The frame is formed on the second main surface side of the piezoelectric wafer by a part of the piezoelectric wafer around the periphery. In this case, since the frame is formed by a part of the piezoelectric wafer by forming the recess on the second main surface of the piezoelectric wafer, no extra material is required to form the frame.

  In another specific aspect of the method for manufacturing an acoustic wave device according to the present invention, the method further includes a polishing step of polishing the second main surface of the piezoelectric wafer so as to reduce the thickness of the piezoelectric wafer. The temperature compensating film is formed after the polishing process. In this case, since the temperature compensation film is formed after the thickness of the piezoelectric wafer is set to a target thickness, it is not necessary to perform a complicated polishing step after the temperature compensation film is formed.

  In still another specific aspect of the method for manufacturing an acoustic wave device according to the present invention, the IDT electrode is formed on the first main surface of the piezoelectric wafer before or after the polishing step. Thus, the IDT electrode may be formed at any stage before or after the polishing process.

  In still another specific aspect of the method for manufacturing an acoustic wave device according to the present invention, after the temperature compensation film is formed on the second main surface of the piezoelectric wafer, the thickness of the piezoelectric wafer is reduced. The method further comprises a step of polishing the first main surface of the piezoelectric substrate, and the IDT electrode is formed on the first main surface of the piezoelectric wafer after the polishing step. In this case, after the temperature compensation film is formed, the first main surface side may be polished to form the piezoelectric wafer to a desired thickness, and then the IDT electrode is formed on the first main surface. Therefore, an elastic wave element can be manufactured easily and with high accuracy.

  In the acoustic wave device according to the present invention, since the temperature compensation film is formed of SOG on the second main surface of the piezoelectric substrate, the temperature compensation film is easily and has a desired thickness using the SOG method. Thus, it can be formed with high accuracy. That is, it is not necessary to perform a complicated process of bonding an insulating substrate using an adhesive. Further, since the temperature compensation film may be formed on a surface different from the IDT electrode formation surface, the IDT electrode can be easily formed, and the temperature compensation film formation process is performed before or after the IDT electrode formation. It may be performed at any later stage. Accordingly, the degree of freedom in the manufacturing process can be increased.

  In addition, in the acoustic wave device obtained by the present invention, the temperature compensation film is formed by SOG on the second main surface of the piezoelectric substrate, so that the acoustic wave device has a structure in which the insulating substrate is bonded. It is also possible to reduce the thickness.

  Therefore, according to the present invention, it is possible to provide a thin and inexpensive acoustic wave device that is small in change in frequency characteristics due to temperature, without complicating the manufacturing process.

  Hereinafter, the present invention will be clarified by describing specific embodiments of the present invention with reference to the drawings.

  With reference to FIGS. 1A to 1F and FIGS. 2A to 2C, a method of manufacturing an acoustic wave device according to an embodiment of the present invention will be described.

In the present embodiment, first, a piezoelectric wafer 1 is prepared as shown in FIG. The piezoelectric wafer 1 has a disk shape, and is made of LiTaO _{3 in} this embodiment. However, the piezoelectric wafer 1 may be made of various piezoelectric single crystals such as LiNbO ₃ and quartz other than LiTaO ₃ .

  Next, the upper surface of the piezoelectric wafer 1 is polished by a sambra to prepare a disc-shaped piezoelectric wafer 1A having a thickness of 20 to 40 μm and a diameter of 100 mm as shown in FIGS. 1 (b) and 2 (a). The piezoelectric wafer 1A has a first main surface 1a and a second main surface 1b facing each other.

  In the present embodiment, the process of polishing the piezoelectric wafer 1 to reduce the thickness is performed by the sambra method, but other polishing methods such as a grinder may be used.

  Next, as shown in FIGS. 1C and 2B, an annular frame 2 is formed on the second main surface 1b of the piezoelectric wafer 1A.

  The frame body 2 is formed by applying a resin material such as a photoresist to the entire surface of the second main surface 1b of the piezoelectric wafer 1A, forming a resin layer, and then patterning by a photolithography technique. Can do.

  In the present embodiment, an annular frame 2 having a height of 300 μm and a width of 2 mm is formed by photolithography.

  In the present embodiment, the outer peripheral edge of the frame body 2 coincides with the outer peripheral edge of the disk-shaped piezoelectric wafer 1A, but the outer peripheral edge of the frame body 2 is located inside the second main surface 1b of the piezoelectric wafer 1A. You may do it. Preferably, the area of the region surrounded by the frame body 2 can be increased by matching the outer peripheral edge of the frame body 2 with the outer peripheral edge of the piezoelectric wafer 1A as in the present embodiment. Thereby, more elastic wave elements can be obtained.

  The planar shape of the frame 2 is not limited to an annular shape, and may be an appropriate shape such as a rectangular frame shape.

  Next, as shown in FIG. 1D, the region surrounded by the frame 2 is filled with the temperature compensation film-forming material 3 by SOG (Spin on Glass). Since the frame body 2 is provided, the thickness of the temperature compensation film forming material 3 is equal to the height of the frame body 2 when the liquid temperature compensation film forming material is filled. That is, a temperature compensation film having a thickness corresponding to the thickness of the frame 2 can be formed.

In the present embodiment, a liquid composition containing SiO ₂ and polysilazane is used as the temperature compensation film forming material 3. Thereafter, the temperature compensation film forming material 3 was baked by maintaining the temperature at 200 to 300 ° C. for 1 to 2 hours. In this way, as shown in FIGS. 1E and 2C, a temperature compensation film 3A made of a 300 μm thick SiO ₂ film was formed, and then the frame 2 was removed.

  Next, an electrode structure of a plurality of surface acoustic wave elements was formed on the first main surface 1a of the piezoelectric wafer 1A by photolithography. That is, a large number of electrode structures having at least one IDT electrode 4 were formed. FIG. 3A is a plan view schematically showing the first main surface 1a of the piezoelectric wafer 1A. In FIG. 3B, a plurality of division lines X indicating positions at the time of division performed later are shown. A rectangular region surrounded by a plurality of dividing lines Y corresponds to a portion constituting one surface acoustic wave element. As shown in FIG. 3B, the IDT electrode 4 and the reflectors 5 and 6 disposed on both sides of the surface acoustic wave propagation direction of the IDT electrode 4 are formed in the portion where the single surface acoustic wave element is formed. did. That is, an electrode structure having the IDT electrode 4 and the reflectors 5 and 6 was formed in each surface acoustic wave element formation region of FIG.

  In FIG. 1E, only the IDT electrode 4 is schematically shown with a reference number.

  In the present embodiment, Al is used as the electrode material for forming the IDT electrode 4 and the reflectors 5 and 6. However, the electrode material is not limited to the above-described Al, and an appropriate metal or alloy such as Al—Cu or Cu can be used. The electrode structure may be a structure in which a plurality of metal films are stacked.

  Next, as shown in FIG. 1F, the whole was polished by a grinder method so as to reduce the thickness of the temperature compensation film 3A. In this way, a temperature compensation film 3B having a thickness of 150 to 350 μm was obtained.

  Finally, the piezoelectric wafer 1A was divided by dicing or the like along the dividing lines X and Y shown in FIG. 3A to obtain individual surface acoustic wave elements.

  The obtained surface acoustic wave device is shown in a schematic perspective view in FIG. The IDT electrode 4 and the reflectors 5 and 6 are formed on the first main surface 1a of the piezoelectric substrate 1B obtained by dividing the piezoelectric wafer 1A, and the temperature compensation film 3B is formed on the second main surface 1b. A temperature compensation film 3C obtained by dividing is formed.

In the surface acoustic wave element 7 shown in FIG. 4, since the temperature compensation film 3C is formed on the second main surface 1b side of the piezoelectric substrate 1B, a change in frequency characteristics due to a temperature change can be reduced. That is, the linear expansion coefficient of the temperature compensation film 3C made of SiO ₂ is several ppm / ° C. smaller than LiTaO ₃ , and the piezoelectric substrate 1B is made of LiTaO ₃ , so the linear expansion coefficient is about 16 × 10 ⁻⁶ / K. is there. Stress due to the difference in linear expansion coefficient is applied during the temperature change, thereby suppressing the change in the frequency characteristics due to the temperature change as in the case of the surface acoustic wave device described in Patent Document 2.

  The thickness T of the temperature compensation film 3C is preferably set to a ratio of t / T <0.5 with respect to the thickness t of the piezoelectric substrate. If it is thin, it cannot be processed, and if it exceeds 0.5, TCF may deteriorate.

  By setting the roughness of the second main surface side of the piezoelectric wafer to the range of 0.2 to 0.4 in terms of the Ra value of the surface roughness of JISB0601, the influence of bulk waves can be suppressed.

  In the present embodiment, after the piezoelectric wafer 1A is prepared, the temperature compensation film 3A can be formed by a simple process of applying and baking the temperature compensation film forming material 3 by the SOG method. In addition, since the thickness of the temperature compensating film 3A can be controlled by the thickness of the frame body 2, the thickness of the temperature compensating film 3A and the finally prepared temperature compensating film 3C can be adjusted with high accuracy. It can also be easily controlled. Therefore, according to the present embodiment, it is possible to provide an inexpensive surface acoustic wave element that is less susceptible to changes in characteristics due to temperature changes. Moreover, since there are not so many processes heated, the reliability of the obtained acoustic wave element can be improved also by it.

  Preferably, prior to applying the temperature compensation film forming material 3 by SOG, the roughness of the second main surface of the piezoelectric wafer 1 or the piezoelectric wafer 1A is set to 0.4 μm in the Ra value of the surface roughness in JIS B0601. The following is preferable. Accordingly, it is possible to reliably form a temperature compensation film having an accurate thickness and to improve the adhesion between the temperature compensation film and the piezoelectric substrate.

  Preferably, the surface roughness of the temperature compensation film 3B after the formation of the temperature compensation film 3B is set to 0.4 μm or less in JIS B0601.

  Although FIG. 4 shows the surface acoustic wave element 7 using the surface acoustic wave, a boundary acoustic wave element may be formed by laminating dielectric layers as indicated by a dashed line C in FIG. That is, the present invention can be applied not only to the surface acoustic wave element but also to the production of the boundary acoustic wave element.

  In the above embodiment, the temperature compensation film 3A is formed after the frame 2 is formed. However, the process of forming the temperature compensation film can be variously modified.

  FIGS. 5A to 5E are front sectional views for explaining the first modification. In this modification, a piezoelectric wafer 1 is prepared as shown in FIG. 5A, and a frame-like resist 11 is formed on the upper surface of the piezoelectric wafer 1 as shown in FIG. The frame-like resist 11 has an annular shape and is formed of a material that can withstand sandblasting, for example, a resist for a sunbrush.

  Thereafter, the second main surface side of the piezoelectric wafer 1 is polished by sandblasting. In this way, a piezoelectric wafer 1D having a recess 1d shown in FIG. 5C is obtained. The depth of the recess 1d is selected to be the coating thickness of the temperature compensation film forming material to be filled.

  Next, as shown in FIG. 5D, the resist 11 is removed.

  Then, as shown in FIG. 5E, the temperature compensating film-forming material 3 is filled in the recess 1d. Thereafter, in the same manner as in the above-described embodiment, the temperature compensation film-forming material 3 is baked to form a temperature compensation film in the recess 1d of the piezoelectric wafer 1D.

  As in the present modification, the frame body 2 in the above embodiment may be formed by forming the concave portion 1d on the second main surface side of the piezoelectric wafer 1 and the piezoelectric wafer portion 1e surrounding the concave portion 1d. Also in this case, since the piezoelectric wafer portion 1e acts in the same manner as the frame 2, the coating thickness of the temperature compensation film forming material 3 can be easily set by controlling the depth of the recess 1d. .

  6A to 6C are front sectional views for explaining a second modification of the step of forming the temperature compensation film. In this modification, as in the above embodiment, a piezoelectric wafer is prepared and polished to obtain a piezoelectric wafer 1A. Next, the temperature compensation film forming material 3 is directly applied on the second main surface 1b of the piezoelectric wafer 1A by the SOG method so as to have a desired thickness. Thus, the frame body 2 does not necessarily have to be formed, and the frame body portion does not have to be formed around the periphery by forming the recess 1d.

  In the process shown in FIG. 6C, since the frame body 2 does not exist in the periphery, it is difficult to control the coating thickness with high accuracy when the temperature compensation film forming material 3 having a relatively low viscosity is used. It is. However, if the temperature compensation film forming material 3 having a relatively high viscosity is used, the thickness of the temperature compensation film can be controlled with high accuracy without forming the frame 2. In this case, since an extra process such as the formation of the frame 2 is not required, the process can be simplified.

  7A to 7E are schematic front sectional views for explaining a method for manufacturing a surface acoustic wave element according to the second embodiment of the present invention.

In the second embodiment, first, similarly to the first embodiment, a piezoelectric wafer 1 made of LiTaO ₃ having a thickness of 350 μm is prepared, and a polishing process is performed in the same manner as in the first embodiment. A piezoelectric wafer 1A thinned to about ˜40 μm is obtained.

  Next, in this embodiment, as shown in FIG. 7C, an electrode structure including the IDT electrode 4 is formed on the first main surface 1a of the piezoelectric wafer 1A by photolithography. That is, the order of steps is different from that of the first embodiment, and the IDT electrode 4 is formed prior to the application of the temperature compensation film forming material.

  The method for forming the electrode structure including the IDT electrode 4 is performed in the same manner as in the first embodiment.

  Next, as shown in FIG. 7D, the temperature compensation film forming material 3 is applied to the second main surface 1b of the piezoelectric wafer 1A by the SOG method. In this case, as in the first embodiment, the temperature compensation film forming material 3 may be filled after the frame 2 is formed.

  However, in the present embodiment, the temperature compensation film-forming material 3 is applied by the SOG method so as to be considerably thicker than the final temperature compensation film, for example, about 400 to 500 μm.

  Thereafter, the temperature compensation film-forming material 3 is maintained at a temperature of 200 to 300 ° C. for about 1 h to 2 h and fired. In this way, a thick temperature compensation film 3A is formed. Thereafter, polishing is performed by a sambra method to form a temperature compensation film 3B having a final thickness of about 150 to 350 μm. Finally, as in the first embodiment, individual surface acoustic wave elements can be obtained by dividing the piezoelectric wafer 1A.

  As in this embodiment, after the IDT electrode 4 is formed on the piezoelectric wafer 1A, the temperature compensation film forming material 3 may be applied and baked.

  8A to 8E are schematic front sectional views for explaining the manufacturing method according to the third embodiment of the present invention.

  In the present embodiment, after preparing the thick piezoelectric wafer 1, an electrode structure including the IDT electrode 4 is then formed on the first main surface 1 a of the piezoelectric wafer 1. The electrodes can be formed by the same method as in the first embodiment. Thereafter, the piezoelectric wafer 1 is polished from the second main surface side by a samba and grind method to obtain a piezoelectric wafer 1A having a thickness of 150 to 350 μm. Thus, contrary to the second embodiment, the piezoelectric wafer 1 may be polished after the electrode structure including the IDT electrode 4 is formed.

  Subsequent steps are performed in the third embodiment in the same manner as in the second embodiment. That is, as shown in FIG. 8D, a thick temperature compensation film-forming material 3 is applied by the SOG method and then baked, and finally polished by polishing as shown in FIG. A film 3B for temperature compensation of thickness is obtained.

  FIGS. 9A to 9E are schematic front sectional views for explaining a method for manufacturing a surface acoustic wave device according to the fourth embodiment of the present invention.

  In the fourth embodiment, after the piezoelectric wafer 1 is prepared, the piezoelectric wafer 1 is polished from the second main surface side in the same manner as in the first and second embodiments, and the thin piezoelectric wafer 1A is obtained. obtain.

  In the fourth embodiment, after obtaining the piezoelectric wafer 1A, the temperature compensation film-forming material 3 is first applied on the second main surface 1b by the SOG method. In this case, the temperature compensation film forming material 3 is applied to be considerably thicker than the final temperature compensation film. Thereafter, the temperature compensation film forming material 3 is fired in the same manner as in the first to third embodiments to obtain a temperature compensation film.

  Next, similarly to the second and third embodiments, the obtained temperature compensating film is polished by a samba and grind method so as to reduce the thickness. In this manner, as shown in FIG. 9D, a thin temperature compensation film 3B having a small thickness is formed on the second main surface 1b of the piezoelectric wafer 1A. Thereafter, an electrode structure including the IDT electrode 4 is formed on the first main surface 1a side of the piezoelectric wafer 1A. As in this embodiment, the electrode structure including the IDT electrode 4 may be formed after the formation of the temperature compensation film 3B.

  FIGS. 10A to 10E are schematic front sectional views for explaining the manufacturing method according to the fifth embodiment of the present invention.

  In this embodiment, after the piezoelectric wafer 1 is prepared, the temperature compensation film forming material 3 is applied thickly on the second main surface 1b of the piezoelectric wafer 1 by the SOG method as shown in FIG. To do.

  Thereafter, baking is performed to form a temperature compensation film 3A as shown in FIG. The piezoelectric wafer 1 is polished from the first main surface 1a side by a samba or grind method to obtain a piezoelectric wafer 1A having a thickness of 20 to 40 μm.

  Therefore, in this embodiment, the piezoelectric wafer 1 is polished and thinned from the first main surface 1a side.

  Next, as shown in FIG. 10D, an electrode structure including the IDT electrode 4 is formed on the first main surface 1a of the piezoelectric wafer 1A.

  Finally, the temperature compensation film 3A is polished by a sambra method to obtain a temperature compensation film 3B having a thickness of about 150 to 350 μm. The piezoelectric wafer may be polished after the temperature compensation film is formed as in this embodiment.

  Also in the second to fifth embodiments, the temperature compensation film is formed by applying the temperature compensation film forming material from the second main surface side of the piezoelectric wafer by the SOG method and baking it. Is called. Therefore, as in the case of the first embodiment, the thin film for temperature compensation 3B can be easily formed without obtaining a complicated process. Therefore, as in the case of the first embodiment, it is possible to provide an inexpensive and thin surface acoustic wave element without causing much trouble in the process. The second to fifth embodiments can be applied not only to a surface acoustic wave element but also to a method for manufacturing a boundary acoustic wave element.

As is clear from the first to fifth embodiments, according to the present invention, the order of each process such as formation of a temperature compensation film, formation of an electrode structure including an IDT electrode, and polishing of a piezoelectric wafer is variously changed. can do. Therefore, it is possible to increase the degree of freedom in manufacturing, and the cost can be reduced accordingly. The material constituting the temperature compensation film is not limited to SiO ₂ and may be any material having a low expansion coefficient that can be formed in the same manner.

(A)-(f) is each front sectional drawing for demonstrating the manufacturing method of the elastic wave element which concerns on the 1st Embodiment of this invention. (A)-(c) is each perspective view for demonstrating the manufacturing method of the elastic wave element which concerns on the 1st Embodiment of this invention. (A)-(d) is a schematic plan view for demonstrating the process of dividing | segmenting a piezoelectric wafer in the manufacturing method of 1st Embodiment, and the schematic which shows the electrode structure formed on one acoustic wave element. It is a top view. It is a perspective view which shows the elastic wave element obtained by the 1st Embodiment of this invention. (A)-(e) is each front sectional drawing for demonstrating the formation process of the film for temperature compensation in the modification of 1st Embodiment. (A)-(c) is each front sectional drawing for demonstrating each process of forming the film for temperature compensation on a piezoelectric wafer in the 2nd modification of 1st Embodiment. (A)-(e) is each front sectional drawing for demonstrating the manufacturing method of the surface acoustic wave element which concerns on the 2nd Embodiment of this invention. (A)-(e) is each front sectional drawing for demonstrating the manufacturing method of the surface acoustic wave element concerning the 3rd Embodiment of this invention. (A)-(e) is each front sectional drawing for demonstrating the manufacturing method of the surface acoustic wave element concerning the 4th Embodiment of this invention. (A)-(e) is each front sectional drawing for demonstrating the manufacturing method of the surface acoustic wave element which concerns on the 5th Embodiment of this invention. It is front sectional drawing which shows the conventional surface acoustic wave element. It is front sectional drawing which shows an example of the conventional surface acoustic wave apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Piezoelectric wafer 1A ... Piezoelectric wafer 1B ... Piezoelectric substrate 1D ... Piezoelectric wafer 1a ... 1st main surface 1b ... 2nd main surface 1d ... Recess 1e ... Piezoelectric wafer part 2 ... Frame body 3 ... For film formation for temperature compensation Materials 3A to 3C ... Temperature compensation film 4 ... IDT electrode 5, 6 ... Reflector 7 ... Surface acoustic wave element 11 ... Resist

Claims (9)

A piezoelectric substrate having first and second main surfaces facing each other;
An IDT electrode provided on the first main surface of the piezoelectric substrate;
An acoustic wave device comprising: a temperature compensation film formed of SOG on the second main surface of the piezoelectric substrate.   The acoustic wave device according to claim 1, wherein the temperature compensation film is a silicon oxide film. A method for manufacturing an acoustic wave device, comprising:
Preparing a piezoelectric wafer having first and second major surfaces facing each other;
Forming an IDT electrode on the first main surface of the piezoelectric wafer;
Forming a temperature compensation film on the second main surface of the piezoelectric wafer by the SOG method;
And a step of dividing the piezoelectric wafer into a plurality of piezoelectric substrates. Forming a frame having a predetermined thickness on the second main surface side of the piezoelectric wafer;
Filling a portion surrounded by the frame with a material for forming a temperature compensation film by an SOG method;
The method for producing an acoustic wave device according to claim 3, further comprising a step of forming a temperature compensation film by firing the filled temperature compensation film forming material.   5. The acoustic wave element according to claim 4, wherein the frame body is formed by patterning a resin by photolithography, whereby a frame body made of a resin pattern material is formed on the second main surface. 6. Production method.   By forming a recess for injecting a temperature compensation film forming material on the second main surface of the piezoelectric wafer, the second main surface of the piezoelectric wafer is formed around the recess by a part of the piezoelectric wafer. The method for manufacturing an acoustic wave device according to claim 4, wherein the frame is formed on a side.   7. A polishing step of polishing the second main surface of the piezoelectric wafer so as to reduce the thickness of the piezoelectric wafer is further provided, and the temperature compensation film is formed after the polishing step. The manufacturing method of the elastic wave element of any one of these.   The method for manufacturing an acoustic wave device according to claim 7, wherein the IDT electrode is formed on the first main surface of the piezoelectric wafer before or after the polishing step.   Polishing the first main surface of the piezoelectric substrate so as to reduce the thickness of the piezoelectric wafer after the temperature compensation film is formed on the second main surface of the piezoelectric wafer; The method for manufacturing an acoustic wave element according to claim 4, wherein the IDT electrode is formed on the first main surface of the piezoelectric wafer after the polishing step.

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