JP2010103920A - Surface acoustic wave device and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface acoustic wave device having a plurality of frequency characteristics different from one another and improved in a problem such as a short circuit between electrode fingers of an IDT electrode, and a method of manufacturing the same. <P>SOLUTION: The surface acoustic wave device 1 includes: a piezoelectric substrate 7; a first IDT electrode 9 formed on the piezoelectric substrate 7 and having a first film thickness; a second IDT electrode 13 formed on the piezoelectric substrate 7 and having a second film thickness larger than the first film thickness; and an insulation film 20 covering only the first IDT electrode 9 in the first IDT electrode 9 and the second IDT electrode 13. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a surface acoustic wave device and a method for manufacturing the same.

Conventionally, various surface acoustic wave devices have been proposed in which a plurality of IDT electrodes having different frequency characteristics are formed on a single piezoelectric substrate. For example, in the surface acoustic wave filter described in Patent Document 1, the first filter portion and the second filter portion are formed on one piezoelectric substrate, and the film thickness of the IDT electrode constituting the first filter portion, By making the film thickness of the IDT electrode constituting the filter portion different, two filter portions for extracting frequency signals in two different frequency bands are formed.
JP 2001-85967 A

  However, the surface acoustic wave filter disclosed in Patent Document 1 is sealed by housing the piezoelectric substrate on which the first filter portion and the second filter portion are formed in the package. However, the first filter portion and the second filter are sealed. The IDT electrodes constituting the respective parts are exposed in the internal space of the package. For this reason, there has been a problem that foreign matters mixed at the time of manufacture adhere to the IDT electrodes and short-circuit the electrode fingers of the IDT electrodes. In addition, the IDT electrode of the filter unit corresponding to the frequency band on the high frequency side often has a narrower interval between electrode fingers, and the above-described problem is remarkable.

  The present invention has been made to solve the above problems, and provides a surface acoustic wave device having a plurality of different frequency characteristics and improving problems such as a short circuit between electrode fingers of an IDT electrode and a method for manufacturing the same. The purpose is to do.

  The surface acoustic wave device according to the present invention includes a piezoelectric substrate, a first IDT electrode having a first film thickness formed on the piezoelectric substrate, and formed on the piezoelectric substrate and larger than the first film thickness. A second IDT electrode having a second film thickness; and an insulating film that covers only the first IDT electrode among the first IDT electrode and the second IDT electrode.

  A method for manufacturing a surface acoustic wave device according to the present invention is a method for manufacturing a surface acoustic wave device in which a first IDT electrode and a second IDT electrode are formed on a piezoelectric substrate. Forming the first IDT electrode having the first film thickness in the first region, forming the insulating film covering the first IDT electrode, and the first region on the piezoelectric substrate. Forming a conductive film having a second film thickness larger than the first film thickness in a second area different from the first area; and using the insulating film as an etching stopper, the conductive film in the first area Etching a film, and forming a second IDT electrode by etching the conductive film in the second region with a predetermined pattern.

  According to the present invention, it is possible to provide a surface acoustic wave device having a plurality of different frequency characteristics and improving problems such as a short circuit between electrode fingers of an IDT electrode and a method for manufacturing the same.

  Hereinafter, an embodiment of a surface acoustic wave device according to the present invention will be described with reference to the drawings.

  FIG. 1 is a plan view of the surface acoustic wave device according to the present embodiment. 2 is a cross-sectional view of the surface acoustic wave device of FIG. 1 taken along the line II-II. 3 is a cross-sectional view taken along the line III-III of the surface acoustic wave device of FIG. 4 is a cross-sectional view of the surface acoustic wave device of FIG. 1 taken along line IV-IV.

  As shown in FIGS. 1 to 4, the surface acoustic wave device 1 according to the present embodiment includes a surface acoustic wave element 3 and a base substrate 5 to which the surface acoustic wave element 3 is joined. In FIG. 1, the base substrate 5, an insulating film 20 (to be described later), and solder bumps 25 are not shown for convenience of explanation.

  The surface acoustic wave element 3 is, for example, a surface acoustic wave filter, a surface acoustic wave resonator, or the like, and includes a piezoelectric substrate 7, a first IDT electrode 9 formed on the piezoelectric substrate 7, a first electrode terminal 11, 2 IDT electrodes 13, a second electrode terminal 15, and a frame body 17. The piezoelectric substrate 7 is made of a piezoelectric material such as a lithium tantalate single crystal, a lithium niobate single crystal, or a lithium tetraborate single crystal.

  Two first IDT electrodes 9 are arranged side by side in the direction of arrow Y in FIG. Each first IDT electrode 9 is composed of two electrodes (hereinafter referred to as first comb-shaped electrodes) 19 and 19 formed in a comb-tooth shape. The first comb-shaped electrodes 19 and 19 are arranged so as to face each other and the electrode fingers 19a and 19a mesh with each other.

As shown in FIGS. 1 to 3, an insulating film 20 made of SiO ₂ that covers the first IDT electrode 9 is formed on the surface of the first IDT electrode 9. In FIG. 1, the formation range of the insulating film 20 is indicated by a broken line P. Hereinafter, a region on the piezoelectric substrate 7 corresponding to the region surrounded by the broken line P is referred to as a first region P.

  The first electrode terminal 11 is connected to the base end portion 19b of the first IDT electrode 9, and as shown in FIG. 2, is connected to an element connection electrode 21 provided on the base substrate 5 described later. It is like that.

  As with the first IDT electrode 9, two second IDT electrodes 13 are arranged side by side in the arrow Y direction in FIG. Each second IDT electrode 13 is composed of two electrodes 23 and 23 (hereinafter referred to as second comb-shaped electrodes) formed in a comb-like shape. The second comb-like electrodes 23 and 23 are arranged so as to face each other and the electrode fingers 23a and 23a mesh with each other.

  The second electrode terminal 15 is connected to the base end portion 23b of the second IDT electrode 13, and as shown in FIG. 2, is connected to an element connection electrode 21 provided on the base substrate 5 described later. It is like that.

  As shown in FIG. 2, the frame body 17 is provided along the peripheral edge of the piezoelectric substrate 7 so as to surround the first IDT electrode 9 and the second IDT electrode 13 together.

  The base substrate 5 is made of an insulating material such as ceramic or glass ceramic, and its peripheral portion is bonded to the upper surface of the frame body 17 by solder bumps 25 as shown in FIGS. By doing so, the surface acoustic wave element 3 is sealed by the frame body 17 and the base substrate 5.

  As shown in FIG. 2, a through hole 5 a penetrating the base substrate 5 is formed at a position corresponding to the first electrode terminal 11 and the second electrode terminal 15 in the base substrate 5. The through holes 5 a are provided with element connection electrodes 21, and each element connection electrode 21 is joined to the corresponding electrode terminals 11 and 15 by solder bumps 25. With this configuration, the surface acoustic wave element 3 bonded to the base substrate 5 can be electrically connected to an external drive circuit connected to the element connection electrode 21 of the base substrate 5.

  Next, cross-sectional configurations of the first IDT electrode 9, the second IDT electrode 13, the first electrode terminal 11, the second IDT electrode 13, and the frame body 17 configured as described above will be described in detail. .

  As shown in FIGS. 2 and 3, the first IDT electrode 9 is formed of a first conductive film 31 having a first film thickness. As shown in FIGS. 2 and 4, the second IDT electrode 13 is formed of a second conductive film 32 having a second film thickness that is larger than the first film thickness. By doing so, the film thickness of the second IDT electrode 13 is larger than the film thickness of the first IDT electrode 9, and the second IDT electrode 13 has a filter characteristic corresponding to the frequency band on the low frequency side. The first IDT electrode 9 has a filter characteristic corresponding to the frequency band on the high frequency side.

  As shown in FIGS. 2 to 4, the frame body 17 is formed by laminating a second conductive film 32 and a third conductive film 33. By doing so, the height of the frame body 17 becomes higher than the heights of the first IDT electrode 9 and the second IDT electrode 13, and the first IDT electrode 9 and the second IDT electrode 13, the base substrate 5, and the like. A gap is secured between the two.

  As shown in FIG. 2, the first electrode terminal 11 and the second electrode terminal 15 are formed by laminating a second conductive film 32 and a third conductive film 33, as in the frame body 17. By doing so, the height of the first electrode terminal 11 and the second electrode terminal 15 becomes the same as the height of the frame body 17, and when the surface acoustic wave element 3 is joined to the base substrate 5, the first electrode terminal 11 and the second electrode terminal 15 have the same height. The electrode terminal 11 and the second electrode terminal 15 can be joined to the element connection electrode 21 provided on the base substrate 5.

  The first conductive film 31, the second conductive film 32, and the third conductive film 33 are made of, for example, Al, Al alloy (for example, Al—Cu system, Al—Ti system), Cu, or Cu alloy (for example, Cu— It can be formed of a metal film such as Mg-based, Cu-Ti-based, Cu-Rd-based), Ag, or an Ag alloy (eg, Ag-Mg-based, Ag-Ti-based, Ag-Rd-based). The first conductive film 31, the second conductive film 32, and the third conductive film 33 are formed at different film formation timings, as will be described later.

  Next, a method for manufacturing the surface acoustic wave device 1 configured as described above will be described with reference to FIGS.

  First, a piezoelectric substrate 7 is prepared, and a first conductive film 31 is formed on the piezoelectric substrate 7 by using a crystal growth method such as a vapor deposition method, a sputtering method, or a CVD method, as shown in FIG. To do.

  Next, as shown in FIG. 5B, a resist R1 is applied on the first conductive film 31, and a predetermined pattern is exposed and developed by a photolithography method. Then, as shown in FIG. The first conductive film 31 is etched by a wet etching method. Thereafter, as shown in FIG. 5D, the resist R1 is peeled off.

Subsequently, as shown in FIG. 5E, a resist R2 is applied on the first conductive film 31, and a predetermined pattern is exposed and developed by a photolithography method. Then, as shown in FIG. The first conductive film 31 is etched by a dry etching method. At this time, for example, a mixed gas of BCl ₃ , Cl ₂ , and N ₂ is used as the etching agent. Thereafter, as shown in FIG. 5G, the resist R2 is peeled off. Thus, the first IDT electrode 9 is formed in the first region P on the piezoelectric substrate 7.

Next, as shown in FIG. 6 (h), CVD using tetraethoxysilane as a raw material for the first region P on the piezoelectric substrate 7 and the second region S, which is a region different from the first region P, is performed. The insulating film 20 made of SiO ₂ is formed by using a crystal growth method such as a method.

  Then, as shown in FIG. 6 (i), a resist R3 is applied on the insulating film 20, and a predetermined pattern is exposed and developed by a photolithography method. Then, as shown in FIG. 6 (j), a wet etching method is used. Thus, the insulating film 20 in the second region S is etched. Thereafter, as shown in FIG. 6 (k), the resist R3 is peeled off. Thus, the insulating film 20 that covers the first IDT electrode 9 is formed in the first region P on the piezoelectric substrate 7.

  Subsequently, as shown in FIG. 6L, the second conductive film is formed on the first region P and the second region S on the piezoelectric substrate 7 by using a crystal growth method such as vapor deposition, sputtering, or CVD. 32 is formed.

  Then, as shown in FIG. 6 (m), a resist R4 is applied on the second conductive film 32, a predetermined pattern is exposed and developed by photolithography, and then wet as shown in FIG. 6 (n). The second conductive film 32 in the first region P is etched by an etching method. At this time, an etchant having a lower etching rate of the insulating film 20 than the second conductive film 32 can be used. For example, an alkali developer containing tetramethylammonium hydroxide (manufactured by Tokyo Ohka Kogyo Co., Ltd., By using the product name: NMD-W), the second conductive film 32 is selectively etched using the insulating film 20 as an etching stopper. Thereafter, as shown in FIG. 7 (o), the resist R4 is peeled off.

Next, as shown in FIG. 7 (p), a resist R5 is applied to the first region P and the second region S on the piezoelectric substrate 7, and a predetermined pattern is exposed and developed by a photolithography method. As shown in (q), the second conductive film 32 in the second region S is etched by a dry etching method. At this time, for example, a mixed gas of BCl ₃ , Cl ₂ , and N ₂ is used as the etching agent. Thereafter, as shown in FIG. 7R, the resist R5 is peeled off. Thus, the second IDT electrode 13 is formed.

  Next, as shown in FIG. 8S, a resist R6 is applied to the first region P and the second region S on the piezoelectric substrate 7, and a predetermined pattern is exposed and developed by a photolithography method. As shown in (t), the third conductive film 33 is formed by sputtering or the like. Then, as shown in FIG. 8 (u), the resist R6 is removed, and the third conductive film 33 formed on the resist R6 is removed. By doing so, the first electrode terminal 11, the second electrode terminal 15, and the frame body 17, each of which is composed of a stacked body including the second conductive film 32 and the third conductive film 33, are formed.

  As described above, the surface acoustic wave device 3 according to this embodiment is manufactured.

  Then, as shown in FIG. 2, the surface acoustic wave element 3 is disposed so as to face the base substrate 5, and the peripheral portion of the base substrate 5 and the frame body 17 are joined by the solder bumps 25. The provided element connection electrode 21 is joined to the first electrode terminal 11 and the second electrode terminal 15. Thus, the surface acoustic wave device 1 according to this embodiment is manufactured.

  According to the surface acoustic wave device 1 according to the present embodiment, the first IDT electrode 9 is formed by the first conductive film 31 having the first film thickness, and the second IDT electrode 13 is larger than the first film thickness. The second conductive film 32 having two thicknesses is formed. Therefore, the film thickness of the second IDT electrode 13 is larger than the film thickness of the first IDT electrode 9, and the film thickness of the first IDT electrode 9 and the film thickness of the second IDT electrode 13 are different. Two filter sections for extracting frequency signals in two different frequency bands can be formed.

  Further, in the surface acoustic wave device 1, since the first IDT electrode 9 is covered with the insulating film 20, it is possible to prevent a short circuit due to adhesion of conductive foreign matter to the first IDT electrode 9. .

  In the surface acoustic wave device 1, only the first IDT electrode 9 out of the first IDT electrode 9 and the second IDT electrode 13 is covered with the insulating film 20, and the second IDT electrode 13 is insulated. Not covered by membrane. This is for the following reason.

  That is, the thickness of the second IDT electrode 13 is larger than that of the first IDT electrode 9 as shown in FIG. Therefore, when covering the second IDT electrode 13 with an insulating film, it is necessary to make the film thickness of the insulating film larger than that of the insulating film 20 covering the first IDT electrode 9 in consideration of coverage. Therefore, in this case, the second IDT electrode 13 is covered with an insulating film having a large mass, the vibration of the electrode finger is attenuated, and it becomes difficult to obtain a desired frequency characteristic. On the other hand, the first IDT electrode 9 has a small film thickness as shown in FIG. 3, so that the coverage is good even if the film thickness of the insulating film 20 is small. Therefore, the first IDT electrode 9 is covered with the insulating film 20 having a relatively small mass, and the influence on the frequency characteristics is small.

  The first IDT electrode 9 has a small film thickness and corresponds to a frequency band on the high frequency side. Usually, the interval between adjacent electrode fingers is smaller than that of the second IDT electrode 13. Therefore, the problem of a short circuit due to the adhesion of foreign matter is likely to occur.

  From the above, in the surface acoustic wave device 1, only the first IDT electrode 9 is covered with the insulating film 20.

  Also, according to the surface acoustic wave device 1, the first IDT electrode 9 is formed of the first conductive film 31, the second IDT electrode 13 is formed of the second conductive film 32, and each IDT electrode 9 is formed. , 13 are each composed of a single layer. Therefore, insertion loss can be reduced as compared with the case where the IDT electrode is formed of a stacked body in which a plurality of conductive films are stacked. That is, in this case, the resistance increases at the boundary surface of each layer of the stacked body constituting the IDT electrode, but when it is configured by a single layer, such a boundary surface does not exist and insertion loss can be reduced. .

  Further, according to the present embodiment, the frame body 17 is formed by laminating the third conductive film 33 on the second conductive film 32 that forms the second IDT electrode 13. Therefore, for example, when the second conductive film 32 is formed by the crystal growth method as described above, a part of the frame body 17 can be formed simultaneously with the formation of the second IDT electrode 13. Since the frame body 17 needs to be formed larger than the film thickness of the second IDT electrode 13, the manufacturing time can be shortened by forming a part of the frame body 17 at the same time as compared with the case where the frame body 17 is formed separately. can do.

  In the present embodiment, since the first IDT electrode 9 and the second IDT electrode 13 are collectively surrounded by one frame 17, the surface acoustic wave device can be downsized. .

  Further, according to the method for manufacturing the surface acoustic wave device 1 according to the present embodiment, after forming the first IDT electrode 9 as shown in FIG. ), The first IDT electrode 9 is protected by the insulating film 20. Therefore, in the subsequent steps, the first IDT electrode 9 is not exposed to a resist stripping solution or the like, and the formed electrode pattern is not damaged. In general, since the electrode pattern of the IDT electrode on the high frequency side is formed more finely than the electrode pattern of the IDT electrode on the low frequency side, problems such as disconnection or short circuit of the electrode fingers are likely to occur. By covering the first IDT electrode 9 on the high frequency side with the film 20, the occurrence of such a problem can be prevented.

  In addition, according to the method for manufacturing the surface acoustic wave device 1 according to the present embodiment, as shown in FIGS. 6M to 6N, the second conductive film in the first region P using the insulating film 20 as an etching stopper. 32 is etched. For this reason, the insulating film 20 covering the first IDT electrode 9 has both a function as a protective film and a function as an etching stopper. Therefore, a manufacturing process can be simplified compared with the case where each structure which fulfill | performs each function is formed separately.

As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, A various change is possible unless it deviates from the meaning. For example, in the above embodiment, the insulating film 20 is formed in the region surrounded by the broken line P. However, as long as only the first IDT electrode of the first IDT electrode 9 and the second IDT electrode 13 is covered, this is used. It is not limited. In the above embodiment, although an insulating film 20 with SiO _2, which has an insulating property, and not the etching rate than the second conductive film 32 is limited is as long as to a material decreases, For example, it may be formed of SiN _x or the like.

  Further, in the manufacturing method according to the above embodiment, after the second conductive film 32 in the first region P is etched in the steps shown in FIGS. 6 (m) to (n), the process shown in FIGS. In the illustrated process, the second conductive film 32 in the second region S is etched. However, the present invention is not limited to this. For example, the second conductive film 32 in the first region P and the second region S is simultaneously etched. You may make it do. In this case, for example, the pattern corresponding to the electrode pattern of the second IDT electrode 13 may be exposed and developed on the resist R4 in the second region S in the step shown in FIG.

  Moreover, in the said embodiment, the height of the 1st electrode terminal 11, the 2nd electrode terminal 15, and the frame 17 is higher than the 2nd IDT electrode 13, and the 2nd IDT electrode 13 is the 1st IDT electrode. The first IDT electrode 9, the first electrode terminal 11, the second IDT electrode 13, and the second electrode are configured so as to be higher than the height 9. The terminal 15 and the frame 17 may include one or more conductive films in addition to the conductive film layers exemplified above.

  In the above embodiment, the first electrode terminal 11, the second electrode terminal 15, and the frame body 17 may include an under bump metal layer including at least one layer including the third conductive film 33. For example, the under bump metal layer is formed by laminating a fourth conductive film and a fifth conductive film (not shown) in this order from the third conductive film 33 side between the third conductive film 33 and the solder bump 25 shown in FIG. The third conductive film 33, the fourth conductive film, and the fifth conductive film are used. At this time, for example, the third conductive film 33 is formed of Cr, Ni, Ti or the like, the fourth conductive film is formed of Ni, W, Ta, Ru, Pt, Ti, Pd, or the like, and the fifth conductive film is formed of Au or the like. . The under bump metal layer may be composed of a plurality of layers other than three layers or a single layer. In this case, Ni, W, Ta, Ru, Pt, Ti, Pd, or the like serving as a barrier layer against the solder bumps. It may be configured to include a layer.

  In the surface acoustic wave device 1 according to the embodiment, the film thickness of the insulating film 20 can sufficiently protect the first IDT electrode 9 and has little influence on the frequency characteristics of the first IDT electrode 9. For example, the frequency characteristic of the first IDT electrode 9 can be adjusted by the film thickness of the insulating film 20. In the surface acoustic wave device 1 according to the above embodiment, only the first IDT electrode 9 is covered with the insulating film 20, but the second IDT electrode 13 together with the first IDT electrode 9 is covered with the insulating film. The frequency characteristic of each IDT electrode is adjusted by setting the film thickness of the insulating film covering the first IDT electrode 9 and the film thickness of the insulating film covering the second IDT electrode 13. You can also

1 is a plan view of a surface acoustic wave device according to an embodiment of the present invention. It is the II-II sectional view taken on the surface acoustic wave apparatus of FIG. FIG. 3 is a cross-sectional view of the surface acoustic wave device of FIG. 1 taken along the line III-III. FIG. 4 is a cross-sectional view of the surface acoustic wave device of FIG. 1 taken along the line IV-IV. It is a figure explaining the manufacturing method of the surface acoustic wave apparatus of FIG. It is a figure explaining the manufacturing method of the surface acoustic wave apparatus of FIG. It is a figure explaining the manufacturing method of the surface acoustic wave apparatus of FIG. It is a figure explaining the manufacturing method of the surface acoustic wave apparatus of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Surface acoustic wave apparatus 3 Surface acoustic wave element 5 Base substrate 7 Piezoelectric substrate 9 1st IDT electrode 11 1st electrode terminal 13 2nd IDT electrode 15 2nd electrode terminal 17 Frame 20 Insulating film 25 Solder bump 31 First conductive film 32 Second conductive film 33 Third conductive film

Claims (4)

A piezoelectric substrate;
A first IDT electrode formed on the piezoelectric substrate and having a first thickness;
A second IDT electrode formed on the piezoelectric substrate and having a second thickness greater than the first thickness;
An insulating film that covers only the first IDT electrode of the first IDT electrode and the second IDT electrode;
A surface acoustic wave device.   The surface acoustic wave device according to claim 1, wherein each of the first IDT electrode and the second IDT electrode includes a single layer. A method of manufacturing a surface acoustic wave device in which a first IDT electrode and a second IDT electrode are formed on a piezoelectric substrate,
Forming the first IDT electrode having a first film thickness in a first region on the piezoelectric substrate;
Forming an insulating film covering the first IDT electrode;
Forming a conductive film having a second film thickness larger than the first film thickness in the first region on the piezoelectric substrate and a second region different from the first region;
Etching the conductive film in the first region using the insulating film as an etching stopper;
Forming a second IDT electrode by etching the conductive film in the second region with a predetermined pattern;
A method for manufacturing a surface acoustic wave device. The surface acoustic wave device manufacturing method according to claim 3, wherein each of the first IDT electrode and the second IDT electrode includes a single layer.

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