JPS626511A - Manufacture of surface acoustic wave device - Google Patents

Abstract

PURPOSE:To obtain a device with stable characteristic by forming a interdigital electrode finger or an open strip reflecting electrode and a bonding pad on a piezoelectric substrate with photo-etching and connecting the electrodes with lift-off so as to attain stable wire bonding. CONSTITUTION:The interdigital electrode finger 2, the open strip reflecting electrode 3 and the bonding pad 4 are formed on the piezoelectric substrate 1 by photo etching. In this case, the flow of an etching liquid is blocked partially at etching and no variance is caused in the wire width. Moreover, a pattern 5 connecting the electrode finger 2 and the bonding pad 4 and a pattern 6 connecting the electrodes 3 are formed. Thus, after the electrode finger 2, the electrode 3 and the bonding pad 4 apart from the electrode finger 2 are formed, the pattern connecting the electrode finger 2 and the pad 4 or the electrodes 3 is formed to form even a fine pattern with high accuracy and stable bonding is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of manufacturing surface acoustic wave devices used in video equipment, communication equipment, etc.

Background of the Invention In recent years, surface acoustic wave devices have been increasingly used as equipment has become higher frequency.
The field of application is expanding to high frequencies in the 00 MHz to I GHz band.

In the 60 MHz band surface acoustic wave filter used in the conventional VIP circuit, the line width of the comb-shaped electrode is relatively large, about 10 μm, so there was no particular problem with etching.

Problems to be Solved by the Invention However, when the frequency is close to 1 GHz, the line width of the comb-shaped electrode becomes close to 1 μm, so variations in the line width within the wafer or within the chip are likely to occur due to differences in the flow of the etching solution on the wafer surface. , has a large impact on characteristics.

On the other hand, creating a comb-shaped electrode by lift-off improves the precision of the comb-shaped electrode, but since the substrate cannot be heated when depositing the electrode metal, the adhesion of the metal to the wafer becomes weak and wire bonding becomes difficult. It had the disadvantage of being unstable. The present invention aims to eliminate the above-mentioned conventional drawbacks, and provides a method for manufacturing a surface acoustic wave device in which wire bonding can be performed stably and the characteristics are also stable.

Means for Solving the Problem In order to solve this problem, the method for manufacturing a surface acoustic wave device of the present invention includes forming comb-shaped electrode fingers or open strip reflective electrodes on a piezoelectric substrate by photo-etching, and separating them from the comb-shaped electrode fingers. After forming bonding pads at the same positions, the comb-shaped electrode fingers and the bonding pads or the oven strip reflective electrodes are connected together by lift-off. In a pattern where the bonding pad and the etching pad are connected, the flow of the etching solution becomes poor at the joint, and differences in etching speed tend to occur at that part. The same thing also happens with short strip electrodes. On the other hand, when only comb-shaped electrode fingers are made independently, or when open strip electrodes are made, there is nothing that obstructs the flow of the etching solution, so etching can be carried out stably.

Furthermore, since the bonding pads are also created by photoetching, the substrate can be heated during electrode metal deposition, and bonding will not become unstable as in the case of lift-off.

Comb-shaped electrode fingers etc. were formed. If a pattern connecting the comb-shaped electrode fingers and the bonding pattern or the oven strip reflective electrode is formed later by lift-off, a pattern similar to that obtained by the conventional method can be obtained.

Embodiment Hereinafter, regarding one embodiment of the present invention, a pattern diagram of a chip of an elastic wave oscillator will be shown with reference to the drawings. Figure 1 1
are made by photo-etching, 2, 1 is a piezoelectric substrate, 2 is a comb-shaped electrode finger, 3 is an oven strip reflective electrode, 4 is a bonding pad, 5 is a comb-shaped electrode finger 2 and a bonding panod 4 in a Tsunaku pattern, 6
is a pattern that connects the oven strip reflective electrodes 3.

First, a comb-shaped electrode finger 2, an IJ tube reflective electrode 3, and a bonding pad 4 are formed on a piezoelectric substrate 1 by photoetching. In this state, the comb-shaped electrode fingers 2 and the oven strip reflective electrode 3 are just long and thin patterns lined up, so the flow of the etching solution is not partially obstructed during etching, and variations in line width do not occur. Etching can be performed with high precision. Furthermore, a pattern 5 connecting the comb-shaped electrode fingers 2 and the bonding pads 4 and a pattern 6 connecting the oven strip reflective electrodes 3 are formed by lift-off, thereby forming a surface acoustic wave oscillator chip having predetermined characteristics. Obtainable.

Effects of the Invention As described above, according to the present invention, after the comb-shaped electrode fingers, the oven strip reflective electrode, and the bonding pad separated from the comb-shaped electrode fingers are formed by photoetching, the comb-shaped electrode fingers, the bonding pad, or the oven strip are separated by lift-off. By forming a pattern that connects the strip reflective electrodes, even fine patterns can be made with high precision, and bonding can be performed stably.

Furthermore, at high frequencies, the electrode film thickness is made thinner in order to eliminate the reflection of surface acoustic waves within the comb-shaped electrode, but if it is made too thin, the electrical resistance of the deposited metal increases, resulting in a large insertion loss. However, according to the method of the present invention, by increasing the thickness of the electrode formed by lift-off, the electrical resistance from the bonding part to the electrode finger becomes smaller, so it is possible to reduce the increase in insertion loss.
Its practical effects are significant.

In one embodiment of the method, the surface acoustic wave oscillator tinopupa p-
1 is a diagram showing a pattern 1 formed by photoetching, and a chip pattern is completed by carefully lifting off the pattern 1.

1...Piezoelectric substrate, 2...Comb-shaped electrode fingers,
3...Open strip reflective electrode, 4...
・・・Bonding pattern, 5...Comb-shaped electrode fingers and pumping points (RAD connection pattern, 6...
...A pattern that connects oven strip reflective electrodes.

Claims (1)

[Claims] Comb-shaped electrode fingers are formed on the piezoelectric substrate by photo-etching.
Alternatively, the surface elasticity is characterized by forming an open strip reflective electrode and a bonding pad at a position apart from the comb-shaped electrode fingers, and then connecting the comb-shaped electrode fingers and the bonding pad, or the open strip reflective electrodes, by lift-off. Method of manufacturing wave devices.