JPH04150404A - Manufacture of surface acoustic wave device - Google Patents

Abstract

PURPOSE:To prevent electrode patterns from being damaged by a film forming mask by coating one of two electrode patterns with a protective film and aligning the film forming mask on the protective film while the other electrode pattern is exposed, and then, removing each protective and metallic film on the inside and outside of the mask after forming metallic films on the electrode pattern and exposed surface of the mask. CONSTITUTION:The first electrode pattern, namely, input-output interdigital electrodes 12 and 13 and the second electrode pattern, namely, input-output terminal electrodes 14 and 15 are formed on a piezo-electric substrate 11 by a photomechanical process. The first electrode pattern, namely, the electrodes 14 and 15 are exposed by aligning a film forming mask 17 of stainless steel to a negative photoresist pattern 16 and metallic films 18 and 19 of Al having a thickness of 8,000Angstrom are formed on the surfaces of the electrodes 14 and 15 and exposed surface of the mask 17 at a film forming temperature of 200 deg.C. After the films 18 and 19 are formed, the pattern 16 on the inside and outside of the mask 17 and film 19 are removed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing a surface acoustic wave device suitable for use, for example, in manufacturing a surface acoustic wave filter.

[Conventional technology]

Conventionally, a surface acoustic wave device manufactured by this type of manufacturing method has a structure as shown in FIG. This will be explained based on the figure. In the figure, what is indicated by the reference numeral 1 is a piezoelectric substrate made of, for example, a LiNb0z substrate,
2 is an input interdigital electrode, 3 is an input terminal electrode, 4 is an output interdigital electrode, and 5 is an output terminal electrode.

Next, a method for manufacturing the surface acoustic wave device configured as described above will be described. In addition, the surface acoustic wave device is
For example, the center frequency is 800 Mtli: a low-loss band-pass type surface acoustic wave filter.

First, a metal film with a thickness of 1000 mm is deposited on the surface of the piezoelectric substrate l.
Forms human ii membrane. Next, a desired electrode pattern is formed by ordinary photolithography.

In this way, a surface acoustic wave device can be manufactured.

By the way, in the case of a surface acoustic wave filter whose center frequency is near the Gl+z band, the film thickness of the interdigital electrode must be set to about 1000 mm to take measures against sobble within the passband.

However, when the film thickness of the input/output terminal electrodes is as small as about 1000, the wire bonding properties are extremely poor, and the reliability of wire bonding is reduced.

Therefore, generally only the film thickness of the input/output terminal electrodes is increased by a mask film forming method.

[Problem to be solved by the invention]

However, in the conventional manufacturing method of surface acoustic wave devices, the mask for film formation is brought into close contact with the electrode pattern (input/output interdigital electrode) during manufacturing, which can damage the electrode pattern and cause problems during device manufacturing. There was a problem that the trustworthiness of the people was decreasing.

The present invention has been made in view of the above circumstances, and provides a surface acoustic wave device that can prevent damage to the electrode pattern due to the use of a film-forming mask, thereby increasing reliability in device manufacturing. A manufacturing method is provided.

[Means to solve the problem]

The method for manufacturing a surface acoustic wave device according to the present invention involves forming two electrode patterns by photolithography on a substrate on which a metal film has been formed in advance, and then covering one of these electrode patterns with a protective film. Then, a film forming mask is positioned on this protective crotch to expose the other electrode pattern to the outside, and a metal film is formed on this electrode pattern and the externally exposed surface of the mask. The protective film and metal film are removed respectively.

[For production]

In the present invention, by interposing a protective film between the electrode pattern and the mask, the electrode pattern can be protected when the mask is used.

〔Example〕

EMBODIMENT OF THE INVENTION Hereinafter, the structure etc. of this invention will be explained in detail by the Example shown in the figure.

FIGS. 1(a) to 1(d) are cross-sectional views shown for explaining a method of manufacturing a surface acoustic wave device according to the present invention.

First, as shown in the same figure (al), for example, a thickness of 1000
A piezoelectric substrate 11 made of, for example, a LiNbO3 substrate, on which a metal film is formed to a degree of
Input/output interdigital electrodes as electrode patterns 12. L3 and input/output terminal electrodes 14 and 15 as a second electrode pattern are formed. Next, the second electrode pattern of these two electrode patterns, that is, the interdigital electrode 12, 13, is covered with a negative photoresist pattern 16 as a protective film, as shown in FIG. 3(b). After that, this negative photoresist pattern 16 is
As shown in 1, a mask 17 for film formation made of stainless steel
are aligned to expose the first electrode pattern, that is, the input/output terminal electrode 14.15, to the outside W5, and a film is formed on the externally exposed end surface of the input/output terminal electrode 14.15 and the mask 17 by, for example, a vacuum evaporation method or a sputtering method. temperature 20
8000mm thick Al metal film at 0℃ condition 18.19
After forming, the negative photoresist pattern 16 and the Al metal film 19 inside and outside the mask 17 are formed in the same figure (d).
Remove as shown in l. In this case, the negative photoresist pattern 16 is removed by a resist stripper.

In this way, the surface acoustic wave device of the present invention can be manufactured.

Therefore, in this embodiment, by interposing the negative photoresist pattern 16 between the input/output digital electrode 12.13 and the mask 17, the input/output digital electrode 12.13 can be protected when the mask is used.
Unlike conventional methods, the mask 17 for film formation does not come into close contact with the input/output interdigital electrodes 12.13 during manufacturing, and the mask 17
Input/output interdigital electrodes by use of 12.13
damage can be prevented.

The negative photoresist pattern 16 covers the surfaces of the interdigital electrodes 12, 13 and the piezoelectric substrate 11 during manufacture.

Although this embodiment shows the case where a negative photoresist pattern 16 is used as the protective film, the present invention is not limited to this, and as shown in FIG. There is no problem with that. In this case, the heat resistance is better than that of the negative photoresist pattern 16, and the film formation temperature can be set to a high temperature of 300°C to 350°C during additional film formation, which improves the adhesion of the additional film formation. be able to.

In addition, in this example, the case where the material for the additional film formation was 8ρ was shown, but in the present invention, for the purpose of improving the bonding property and the bonding speed, the additional film formation may be made of Au as in the example. Acoustic wave devices can be manufactured.

〔Effect of the invention〕

As explained above, according to the present invention, two electrode patterns are formed by photolithography on a substrate on which a metal film has been formed in advance, and then one of these electrode patterns is covered with a protective film, After that, a film-forming mask is positioned on this protective film to expose the other electrode pattern to the outside, and a metal film is formed on this electrode pattern and the externally exposed surface of the mask. Since the protective film and metal film are removed, the electrode pattern can be protected when using a mask. Therefore, since the film-forming mask does not come into close contact with the electrode pattern during manufacturing as in the past, damage to the electrode pattern due to the use of the film-forming mask can be prevented, and reliability in device manufacturing can be increased. .

[Brief explanation of drawings]

FIGS. 1 fal to (d) are cross-sectional views shown to explain the method of manufacturing a surface acoustic wave device according to the present invention, FIG. 2 is a cross-sectional view shown to explain another embodiment, and FIG. FIG. 2 is a cross-sectional view shown to explain a conventional method of manufacturing a surface acoustic wave device. 11... Piezoelectric substrate, 12... Input interdigital electrode, 13... Output interdigital electrode, 14... Input terminal electrode, 15... Output terminal electrode, 16... ...Negative photoresist pattern, 17.
···mask. Agent Masuo Oiwa

Claims (1)

[Claims] Two electrode patterns are formed by photolithography on a substrate on which a metal film has been formed in advance, then one of these electrode patterns is covered with a protective film, and then a film-forming film is applied on this protective film. Aligning the mask to expose the other electrode pattern to the outside, forming a metal film on this electrode pattern and the externally exposed surface of the mask, and then removing the protective film and the metal film on the inside and outside of the mask, respectively. A method for manufacturing a surface acoustic wave device characterized by: