JPH05251976A - Method for manufacturing electrode of surface acoustic wave element - Google Patents

Abstract

PURPOSE:To suppress a deviation in the electrode film thickness small when the electrode of an interdigital transducer and reflector of a surface acoustic wave element with a low frequency is made by the electronic beam vacuum vapor-deposition. CONSTITUTION:A metal film is added and formed in the step 1 when the film thickness is smaller than a permissible deviation in steps 31, 32 of a metal film thickness check process 3, and when the thickness is thicker than the permissible deviation, after the film thickness is made thin by the ion milling or the like in th etching step 5, the processing is restored to the film thickness check process 3 and an electrode of a prescribed pattern is formed to the film whose thickness is within the permissible deviation in the photo-lithography step 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an electrode of a surface acoustic wave device mainly used for communication equipment.

[0002]

2. Description of the Related Art FIG. 8 is a flow chart of a conventional electrode manufacturing method, and FIG. 9 is a plan view of a conventional surface acoustic wave device and FIG.
It is an A'sectional view. The numbers 1 to 4 in FIG. 8 are the step numbers of the respective steps, 10 in FIG. 9 is the piezoelectric substrate, 20 is the electrode of the interdigital transducer, and 30 is the electrode of the grating reflector. The electrode film thickness of the surface acoustic wave device of about 280 MHz is about 3000 Å, and the yield is about 50 to 60% when the allowable deviation is ± 2%. A method of manufacturing the electrodes 20, 30 such as interdigital electrodes and reflector electrodes provided on the piezoelectric substrate 10 will be described with reference to FIGS. Piezoelectric substrate 10
After cleaning the surface of the substrate by ultrasonic cleaning with an organic solvent such as acetone / isopropyl alcohol in a cleaning step 1, gold (Au) or aluminum (Al) is used as an electrode material on the entire surface of the piezoelectric substrate 10 in a metal film forming step 2. A metal film having high conductivity such as is formed into a thin film by electron beam vacuum deposition or the like. After inspecting the metal film thickness in the film thickness inspecting step 3, a desired electrode pattern is created in the photolithography step 4.

[0003]

However, in general, the characteristics of the surface acoustic wave element manufactured in this way vary depending on the variation in the electrode film thickness. When the electrode is formed by electron beam vacuum deposition, ± 2% to the desired electrode film thickness
In the case of a surface acoustic wave element of 89 MHz having a low frequency, the film thickness is about 8700 Å, and the yield decreases to about 10% when the allowable deviation is ± 2%. Therefore, it is necessary to increase the yield by setting the allowable deviation to ± 1%. An object of the present invention is to solve the above-mentioned problems, and to provide an electrode manufacturing method of a surface acoustic wave device having a small deviation in electrode film thickness and a high yield.

[0004]

According to the electrode manufacturing method of the present invention, the film thickness is measured after the formation of the entire surface metal film for electrodes and the variation with respect to the desired film thickness is inspected. The present invention is characterized in that a metal film having a small film thickness deviation is formed by a film thickness adjusting process for performing etching, and then a predetermined electrode is formed by a photolithography process.

[0005]

The present invention will be described in detail below with reference to the drawings. FIG. 1 is a flow chart showing an embodiment of the present invention. Figure 2
7 to 7 are cross-sectional views for explaining the processing method of the present invention. A thin metal film for electrodes of the surface acoustic wave device is formed on the piezoelectric substrate 10 by the conventional cleaning process 1 and metal film forming process 2. Next, in the film thickness inspection step 3, the metal film thickness is measured. Step 3
The film thickness is detected in 1 and if the film thickness is within the allowable deviation range, a predetermined electrode pattern is created in the next photolithography process 4. If it exceeds the allowable deviation range, it is determined in step 32 whether the deviation is larger or smaller than the desired range.
If it is thinner than the desired range as shown in step 1, the cleaning step 1 is performed again.
Then, in the metal film forming step 2, the additional metal film is formed in close contact with the metal film 22 having an insufficient film thickness by electron beam vacuum deposition or the like. When the surface of the metal film 21 is clean and the metal film 22 re-formed without performing the cleaning step 1 can obtain sufficient adhesion force with the metal film 21, the metal film forming step 2 may be performed.

When the film thickness is thicker than the allowable deviation as shown in FIG. 3, the metal film 23 having an over film thickness is removed by ion milling or the like in the etching step 5. 4, FIG. 5, FIG. 6 and FIG. 7 are sectional views showing other non-uniform electrode film thickness distribution states. In such a distribution state, the etching angle, the ion beam current density, etc. are adjusted and the portion exceeding the allowable deviation is removed by ion milling or the like to flatten it. Ion milling is also performed in the photolithography process 4, so new capital investment is not required. After the above steps, the metal film thickness is measured again in the film thickness inspection step 3, and when the film thickness falls within the allowable deviation range, the photolithography step 4 is performed.
To create the desired pattern.

[0007]

By implementing the present invention, it is possible to reduce the deviation (variation) in the electrode film thickness of the surface acoustic wave element, and to manufacture the surface acoustic wave element with a small yield and a high yield.

[Brief description of drawings]

FIG. 1 is a flow chart showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view when an additional metal film is formed when the metal film thickness is thin.

FIG. 3 is a cross-sectional view when etching is performed when the metal film thickness is large.

FIG. 4 is a cross-sectional view showing a metal film thickness distribution state.

FIG. 5 is a cross-sectional view showing a metal film thickness distribution state.

FIG. 6 is a cross-sectional view showing a metal film thickness distribution state.

FIG. 7 is a cross-sectional view showing a metal film thickness distribution state.

FIG. 8 is a flowchart showing a conventional method for manufacturing an electrode of a surface acoustic wave device.

9A and 9B are a plan view and a cross-sectional view showing a structural example of a surface acoustic wave element.

[Explanation of symbols]

 1 Cleaning Process 2 Metal Film Forming Process 3 Film Thickness Inspection Process 4 Photolithography Process 5 Etching Process 10 Piezoelectric Substrate 20, 30 Electrode 21 Metal Film 22 Reformed Metal Film 23 Etching Metal Film

Claims (1)

[Claims] 1. A metal film is formed on the entire surface of the piezoelectric substrate by electron beam vacuum deposition after cleaning the surface of the piezoelectric substrate in order to form electrodes of the interdigital transducer and the reflector having a predetermined film thickness on the piezoelectric substrate. A film is formed and the film thickness of the metal film is measured to determine whether the film thickness is within a desired deviation range. When the film thickness is within the desired deviation range, a predetermined electrode pattern is formed by photolithography. If it is smaller than the desired deviation range, the additional metal film is closely formed on it by the electron beam vacuum deposition to measure the film thickness. If it is larger than the desired deviation range, the film is etched by etching. A method for manufacturing an electrode of a surface acoustic wave device, wherein the thickness is reduced and the film thickness is measured.