JP2010028701A - Acoustic wave element and communication apparatus employing the same, and method of manufacturing acoustic wave element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve reliability in connection between conductors on an acoustic wave element. <P>SOLUTION: The acoustic wave element includes: a piezoelectric substrate 21; an interdigital electrode 22 and first, second and third conductors 23-25 disposed on the piezoelectric substrate 21; a resist layer 40 disposed on the piezoelectric substrate 21 so as to cover the third conductor 25; and a fourth conductor 26 disposed on the resist layer 40 and electrically connecting the first conductor and the second conductor. As described in this configuration, the present invention uses the resist layer 40 to be used for a manufacturing process as a means for insulating the third conductor 25 and the fourth conductor 26. Namely, since the resist layer 40 is tapered to be spread downward in the manufacturing process, an approximately right-angled corner is eliminated in the resist layer 40. Otherwise, this corner becomes an obtuse angle. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an acoustic wave device, a communication device using the same, and a method for manufacturing the acoustic wave device.

  The acoustic wave element is used as a high frequency filter for communication equipment such as a mobile phone. An example of the acoustic wave element is shown in FIG. 4A is a top view of the acoustic wave element, and FIG. 4B is a cross-sectional view taken along line AB of FIG. 4A. In FIG. 4A, the conventional acoustic wave element includes a piezoelectric substrate 1, a comb electrode 2, a first conductor 3, a second conductor 4, and a third electrode disposed on the piezoelectric substrate 1. A conductor 5 and a fourth conductor 6 disposed on the piezoelectric substrate 1 and electrically connecting the first conductor 3 and the second conductor 4 are provided. The third conductor 5 and the fourth conductor 6 are electrically insulated.

As shown in FIG. 4A, conductors other than the first to fourth conductors 3 to 6 are arranged on the piezoelectric substrate 1. That is, the conventional acoustic wave element has conductors 10, 11, and 12 as input terminals to which signals are input, conductors 5 and 7 as output terminals from which signals filtered in the comb electrode 2 are output, and ground potential. Conductors 13, 14, 15, 16, 3, 4, and 8 as ground terminals to be formed, and conductors 17, 18, 19, and 6 that electrically connect these conductors 13, 14, 15, 16, 3, 4, and 8 to each other. , 9 are provided on the piezoelectric substrate 1. Further, in FIG. 4 (b), the conventional acoustic wave element has a SiO ₂ layer 20 disposed to cover the third conductor 5 on the piezoelectric substrate 1, so as to cover the SiO ₂ layer 20 By disposing the fourth conductor 6 in the above, the third conductor 5 and the fourth conductor 6 are insulated.

For example, Patent Documents 1 and 2 are known as prior art document information relating to the invention of this application.
JP-A-5-167387 JP-A-5-235684

  However, in such a conventional acoustic wave device, the connection reliability of the fourth conductor 6 may be reduced. The reason for this will be described below.

The third conductor 5 has a substantially vertical surface and a horizontal surface with respect to the main surface of the piezoelectric substrate 1, and has a substantially perpendicular corner formed by the vertical surface and the horizontal surface. When SiO ₂ is deposited on the upper surface of the piezoelectric substrate 1 from above the piezoelectric substrate 1 in order to form the SiO ₂ film 20 covering the third conductor 5, the SiO ₂ film 20 becomes the third conductor. 5, the SiO ₂ film 20 also has a substantially perpendicular corner. For this reason, when the fourth conductor 6 is formed so as to cover the SiO ₂ film 20, there arises a problem that the connection reliability of the fourth conductor 6 is lowered by the corner portion.

  Accordingly, an object of the present invention is to improve the connection reliability between conductors on a piezoelectric substrate in an acoustic wave device.

  In order to achieve the above object, an acoustic wave device of the present invention includes a piezoelectric substrate, comb-shaped electrodes and first, second, and third conductors disposed on the piezoelectric substrate, and the piezoelectric substrate. A resist layer disposed so as to cover the third conductor, and a fourth conductor disposed on the resist layer and electrically connecting the first conductor and the second conductor. .

  As described above, the present invention uses the resist used in the manufacturing process as means for obtaining insulation between the third conductor and the fourth conductor. That is, since the resist forms a tapered shape that spreads downward in the manufacturing process, the substantially perpendicular corner portion is eliminated or the corner portion becomes an obtuse angle. As a result, the connection reliability of the fourth conductor formed on the resist layer can be improved.

(Embodiment 1)
Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1A is a schematic top view of the acoustic wave device according to the first embodiment, and FIG. 1B is a schematic cross-sectional view taken along the line AB of FIG.

  In FIG. 1A, the acoustic wave element includes a piezoelectric substrate 21, a comb electrode 22 disposed on the piezoelectric substrate 21, a first conductor 23, a second conductor 24, and a third conductor 25. And a fourth conductor 26 that is disposed on the piezoelectric substrate 21 and electrically connects the first conductor 23 and the second conductor 24. Further, the third conductor 25 and the fourth conductor 26 are electrically insulated.

  As shown in FIG. 1A, conductors other than the first to fourth conductors 23 to 26 are arranged on the piezoelectric substrate 21. That is, the acoustic wave element has conductors 30, 31, and 32 as input terminals to which signals are input, and conductors 25 and 27 as output terminals from which the signal filtered at the comb electrode 22 is output, and a ground that creates a ground potential. Conductors 33, 34, 35, 36, 23, 24, and 28 as terminals, and conductors 37, 38, 39, 26, and 29 that electrically connect these conductors 33, 34, 35, 36, 23, 24, and 28 to each other On the piezoelectric substrate 21.

  A communication device (not shown) equipped with this acoustic wave element includes this acoustic wave element and a radio circuit connected to the conductors 25 and 27 of the output terminal.

  Further, in FIG. 1B, the acoustic wave element has a resist layer 40 disposed on the piezoelectric substrate 21 so as to cover the third conductor 25, and the fourth element is formed so as to cover the resist layer 40. By arranging the conductor 26, the third conductor 25 and the fourth conductor 26 are insulated. The resist layer 40 is a resist for patterning the comb-teeth electrode 22 and contains an alkali-soluble resin such as phenol, cresol, xylenol, resorcinol, or bisphenol.

  As described above, in the acoustic wave device of the present invention, the resist layer 40 used in the manufacturing process is used as means for insulating between the conductors 25 and 26. That is, since the resist layer 40 has a tapered shape that spreads downward in the manufacturing process, the resist layer 40 has almost no right-angled corners, or the corners become obtuse. As a result, the connection reliability of the fourth conductor formed on the resist layer 40 can be improved.

  The acoustic wave element preferably includes a close contact conductor layer (not shown) disposed between the resist layer 40 and the fourth conductor 26. This adhesion conductor layer is, for example, Ti or Cr. Thereby, peeling of the 4th conductor 26 can be suppressed.

  Next, the manufacturing method of the elastic wave element of this Embodiment 1 is demonstrated using Fig.2 (a)-(g) and Fig.3 (a)-(f). FIG. 2 is a schematic cross-sectional view showing the manufacturing process of the acoustic wave device according to the first embodiment, and the cross-section of FIG. 2 is a cross-section taken along AB in FIG. The cross section of FIG. 3 becomes a cross section taken along the line CD of FIG.

  First, as shown in FIG. 2A, the first conductor 23, the second conductor 24, and the third conductor 25 are formed on the piezoelectric substrate 21, and the piezoelectric substrate 21 and the first conductor 23 are formed. Then, an image reversal resist 41 that is insoluble in the developer is applied on the second conductor 24 and the third conductor 25, masking is performed on the third conductor 25, and an image is formed from above the piezoelectric substrate 21. Patterning exposure is performed on the reversal resist 41. The image reversal resist 41 is a resist having a property of being changed from soluble to insoluble in a developer by baking and exposure. The image reversal resist 41 becomes a resist layer 40 in the acoustic wave device shown in FIG.

  That is, by the above process, as shown in FIG. 2B, the image reversal resist 41 other than the portion covering the third conductor 25 becomes soluble in the developer.

  Next, as shown in FIG. 2C, the entire acoustic wave element is baked to perform masking so that parts of the first conductor 23 and the second conductor 24 are exposed, and the piezoelectric element is exposed. Second patterning exposure is performed on the image reversal resist 41 from above the substrate 21.

  As a result, as shown in FIG. 2D, in the second patterning exposure, the portion of the image reversal resist 41 exposed from the mask becomes insoluble in the developer.

  Next, as shown in FIG. 2E, the image reversal resist 41 is developed to form a resist pattern. That is, a reverse taper-shaped resist pattern that extends from below to above is formed on a part of the first conductor 23 and a part of the second conductor 24 so as to cover the third conductor 25. A resist pattern having a forward taper shape extending from the top to the bottom is formed.

  Thereafter, as shown in FIG. 2 (f), a conductor film 42 is deposited on the piezoelectric substrate 21 and the resist pattern, and then lift-off is performed using a resist stripping solution as shown in FIG. 2 (g). Then, the resist pattern on the part of the first conductor 23 and the part of the second conductor 24 and the conductor film 42 thereon are removed. As a result, the fourth conductor 26 is formed so as to cover the image reversal resist 41 covering the third conductor 25, the end of the first conductor 23, and the end of the second conductor 24. 23 and the second conductor 24 are electrically connected.

  Note that even when a general positive resist is used instead of the image reversal resist 41, a resist pattern as shown in FIG. However, in that case, the resist pattern above the first conductor 23 and the second conductor 24 has a forward taper. As a result, in the conductor film formation step shown in FIG. 2 (f), the conductor film 42 adheres to the resist pattern side wall on a part of the first conductor 23 and a part of the second conductor 24. Thus, in the lift-off process shown in FIG. 2G, the resist stripping solution does not sufficiently penetrate into the resist pattern on part of the first conductor 23 and part of the second conductor 24 due to the adhesion. And the lift-off becomes difficult. Therefore, the lift-off process shown in FIG. 2G can be easily realized by using the image reversal type resist 41.

  Hereinafter, the subsequent steps will be described with reference to FIGS. FIG. 3 is a schematic cross-sectional view showing the manufacturing process of the acoustic wave device according to the first embodiment, and the cross-section of FIG. 3 becomes a cross-section taken along line CD in FIG.

  The process shown in FIG. 3A is the same as the process shown in FIG. 2G, and is in a state at the end of the lift-off process. In this state, the third conductor 25 and the fourth conductor 26 are in a state of being electrically connected. Therefore, a process of dividing these will be described below.

  First, as shown in FIG. 3B, a resist 43 is applied to the upper surface of the piezoelectric substrate 21. Then, as shown in FIG. 3C, masking is performed on the upper surface of the piezoelectric substrate 21 so as to expose the space between the third conductor 25 and the fourth conductor 26, and the resist 43 is formed from above the piezoelectric substrate 21. On the other hand, patterning exposure is performed.

  Next, as shown in FIG. 3D, the resist 43 is developed to expose the conductor connecting the third conductor 25 and the fourth conductor 26 from the resist 43.

  Next, as shown in FIG. 3E, the third conductor 25 and the fourth conductor 26 are electrically separated by etching such as dry etching from the upper surface of the piezoelectric substrate 21.

  Next, as shown in FIG. 3F, the resist masked in the step of FIG. 3C is removed using a resist stripping solution.

  As described above, the elastic wave element according to the first embodiment uses the resist layer 40 used in the manufacturing process as a means for insulating the third conductor 25 and the fourth conductor 26. That is, since the resist layer 40 has a forward tapered shape that spreads downward in the manufacturing process, the resist layer 40 has almost no right-angled corners, or the corners become obtuse. As a result, the connection reliability of the fourth conductor 26 formed on the resist layer 40 can be improved.

  The acoustic wave device according to the present invention can improve the connection reliability between conductors on the acoustic wave device, and can be applied to communication equipment and the like.

(A) is a schematic top view of the acoustic wave device according to Embodiment 1 of the present invention, and (b) is a schematic sectional view of the acoustic wave device. (A)-(g) is a cross-sectional schematic diagram which shows the manufacturing process of the same acoustic wave element. (A)-(f) is a cross-sectional schematic diagram which shows the manufacturing process of the same acoustic wave element. (A) is a schematic top view of a conventional acoustic wave device, and (b) is a schematic sectional view of the acoustic wave device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 21 Piezoelectric substrate 22 Comb electrode 23 1st conductor 24 2nd conductor 25 3rd conductor 26 4th conductor 40 Resist layer

Claims (8)

A piezoelectric substrate;
A comb electrode and first, second and third conductors disposed on the piezoelectric substrate;
A resist layer disposed on the piezoelectric substrate so as to cover the third conductor;
An elastic wave device comprising a fourth conductor disposed on the resist layer and electrically connecting the first conductor and the second conductor. The acoustic wave device according to claim 1, further comprising an adhesive conductor layer disposed between the resist layer and the fourth conductor. The acoustic wave device according to claim 1, wherein the resist layer has a forward tapered shape that spreads from the top to the bottom. The acoustic wave device according to claim 1, wherein the resist layer is an image reversal type resist. A communication device comprising the acoustic wave element according to claim 1 and a radio circuit connected to the acoustic wave element. The acoustic wave device according to claim 1, wherein the resist layer is a resist for patterning the comb electrode. Forming a resist on the piezoelectric substrate and on the first, second, and third conductors disposed on the piezoelectric substrate;
Masking at least the third conductor and exposing the resist; and
Developing the resist, and forming a forward tapered resist pattern that spreads from the top to the bottom so as to cover the third conductor;
A method of manufacturing an acoustic wave device comprising: depositing the fourth conductor so as to cover the resist pattern, a part of the first conductor, and a part of the second conductor. The method for manufacturing an acoustic wave device according to claim 7, wherein the resist layer is a resist for patterning the comb-tooth electrode.

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