JPH0251284B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a surface acoustic wave element by forming a predetermined electrode pattern on a piezoelectric substrate.

A surface acoustic wave element is constructed by forming a predetermined electrode pattern such as an interdigital electrode made of a metal thin film or a grating reflector on a piezoelectric substrate. In addition, it is possible to simultaneously form multiple surface acoustic wave elements of the same type or different types from a single substrate.
Batch processing is possible.

Figure 1 shows the manufacturing process of a surface acoustic wave device. First, as shown in a, a metal thin film 2, such as an aluminum thin film, is uniformly deposited on a piezoelectric substrate 1, and a resist 3 is formed on top of it. After exposure and development, the metal thin film 2 is etched as shown in b and c to form a predetermined electrode pattern. By the way, during mass production, in order to reduce the short-circuit defect rate in electrode patterns, for example, interdigital electrode parts, etching is finished when the metal thin film 2 has just been etched to the surface of the substrate 1, as shown in FIG. 1c. Rather than doing so, he intentionally continues etching further. At this time, side etching is performed on the metal thin film 2 as shown in FIG. 1d.

However, in this case, since each electrode pattern on the substrate 1 is electrically insulated, the amount of side etching will vary even on the same substrate. This is because charges are generated on the substrate due to the piezoelectric or pyroelectric effect of the substrate 1, and the stress distribution and temperature gradient vary on the substrate, so the charge distribution is not uniform. That is, in cases where charges are concentrated, side etching progresses more rapidly than in other locations, resulting in variations in the amount of side etching depending on the charge distribution. As a result, the line width of the electrode pattern becomes non-uniform, resulting in deviations in resonance frequency, electrode capacitance, etc.

The present invention has been made in view of these points, and it is an object of the present invention to provide a method for manufacturing a surface acoustic wave element that can reduce deviations in characteristics by uniformizing the amount of side etching of an electrode pattern on a piezoelectric substrate.

In the present invention, when or before etching a metal thin film uniformly deposited on a piezoelectric substrate to form a predetermined electrode pattern, or before etching a metal thin film uniformly deposited on a piezoelectric substrate, a short-circuit thin wire surrounding the electrode pattern is etched into the metal thin film. By forming the short-circuit thin wire, the distribution of charges on the piezoelectric substrate is made uniform, and the amount of side etching is made uniform.

Hereinafter, the present invention will be explained in detail with reference to the drawings. Figure 2 shows a surface acoustic wave resonator designed for the RF converter of a videotape recorder, in which a transducer for electrical signal-surface acoustic wave conversion is constructed in the center of a piezoelectric substrate 11. An interdigital electrode 12 is formed, and grating reflectors 13 and 14 are formed adjacent to both sides thereof. The interdigitated comb electrodes of the interdigital electrode 12 are electrically insulated, while the adjacent electrodes of the grating reflectors 13, 14 are electrically shorted.

When such a surface acoustic wave resonator is manufactured by the method shown in FIG. 1, the amount of side etching differs greatly between the interdigital electrode 12 and the electrodes of the grating reflectors 13 and 14, and the degree of the difference is This causes variations even on the same piezoelectric substrate. Therefore, a second piezoelectric substrate can be placed on the same piezoelectric substrate.
When a large number of sets of electrode patterns as shown in the figure are formed for mass production, the resonant frequency of each surface acoustic wave resonator varies greatly, resulting in a decrease in yield.

Therefore, in the present invention, when manufacturing such a surface acoustic wave resonator, as shown in FIG.
At the same time as etching the electrode patterns 3, 14, etc., a lattice-shaped short-circuit thin wire 15 is formed so as to surround the electrode pattern corresponding to each surface acoustic wave resonator.
The metal thin film that will become the electrode pattern is formed by etching. Specifically, this can be achieved by changing the shape of the glass mask used when exposing the resist. In this case, as shown in the figure, a pair of comb-shaped electrodes constituting each of the interdigital electrodes 12 are connected to a short-circuit thin wire 15 and short-circuited via the short-circuit thin wire 15.

In this way, even in the etching steps after FIG. 1c, the charge distribution on the substrate 11 becomes uniform like a mask, and the amount of side etching of each electrode pattern becomes almost uniform.

After the etching process is completed and the resist is removed, the piezoelectric substrate 11 is removed as shown by the dashed line.
The short-circuited thin wire 15 is cut by a dicing method or the like to divide it into individual surface acoustic wave resonators. In this step, by making the cutting width larger than the line width of the shorting bus bar 15, the interdigital electrode 12
Since the pair of comb-shaped electrodes constituting the resonator are electrically isolated, it is possible to perform proper operation as a surface acoustic wave resonator.

In the above description, the shorting thin wire 15 is formed by etching at the same time as the interdigital electrode 12 and the electrode patterns of the grating reflectors 13, 14, etc., but the electrode pattern may be etched first.

The effects of the present invention will be described below based on examples.
LiTaO ₃ (lithium tantalate), X-cut, 1.2μmt on piezoelectric substrate 11 with rotation 112° and propagation in Y direction.
An aluminum vapor film was uniformly deposited thereon, and an electrode pattern consisting of interdigital electrodes 12, grating reflectors 13 and 14, and shorting thin wires 15 were formed by photoetching, as shown in FIG. The line width of the electrode pattern is 9.0μm, and the pitch is 18μm.
m, and the resonant frequency is 91.250MHz.

FIGS. 4 and 5 show approximately 100 yen formed on the same piezoelectric substrate by the conventional method and the method of the present invention described above.
The actual measurement results of the resonance frequency deviations of 50 surface acoustic wave resonators are shown as histograms. It can be seen that while the conventional method has a variation of about ±50kHz, the method according to the present invention has an extremely small variation of about ±10kHz. Note that similar effects were observed for deviations in other main performances as a resonator, such as electrode capacitance, resonance resistance, and Q value other than the resonance frequency. All of these results are due to a reduction in the variation in the amount of side etching on the same piezoelectric substrate during etching. This reduction in variations in the resonant frequency and performance deviations of the resonator means that it is significantly effective in improving yield during mass production.

As described above, according to the present invention, it is possible to significantly improve the manufacturing yield of surface acoustic wave devices without making any major changes to the manufacturing process.

In addition, especially in the case of fine patterns (high frequency), the electrodes are easily damaged due to discharge between the electrodes due to the pyroelectric effect, but according to the present invention, since the interdigital electrodes and the reflector are at the same potential, the interdigital electrodes and the reflector are at the same potential. No damage will occur.

In addition, in the example, the number of interdigital electrodes is 1.
Although we have explained the surface acoustic wave resonator of the pair, it is also possible to use a two-terminal pair surface acoustic wave resonator with two sets of interdigital electrodes used as input and output transducers, or a surface acoustic wave filter, a delay line, or a surface acoustic wave resonator. A similar effect can be expected in the case of manufacturing, and it is possible to reduce deviations between elements such as center frequency, insertion loss, electrode capacitance, and delay time.

Furthermore, in the examples, electrode patterns corresponding to a plurality of surface acoustic wave elements were formed on the same piezoelectric substrate, but the present invention can also be applied when forming an electrode pattern corresponding to one surface acoustic wave element. It is possible to apply.

Furthermore, although photo etching has been described in the embodiment, the etching method is not limited to this, and for example, electron beams, X-rays, etc. may be used for exposure, and either wet or dry etching may be used.

[Brief explanation of the drawing]

Fig. 1 is a diagram for explaining the manufacturing process of a surface acoustic wave device, Fig. 2 is a plan view showing the basic configuration of a surface acoustic wave resonator, and Fig. 3 is a diagram for explaining an embodiment of the present invention. The plan view, FIGS. 4 and 5 are diagrams showing actual measurement results of resonance frequency deviations of surface acoustic wave resonators obtained by the conventional method and the method of the present invention. 11...Piezoelectric substrate, 12...Interdigital electrode, 13, 14...Grating reflector, 15...Short-circuit thin wire.

Claims (1)

[Scope of Claims] 1. When manufacturing a surface acoustic wave element by uniformly depositing a conductive thin film on a piezoelectric substrate and etching it to form a predetermined electrode pattern, when forming the electrode pattern, Alternatively, a method for manufacturing a surface acoustic wave device, comprising etching the conductive thin film to form a short-circuit thin line surrounding the electrode pattern before that. 2. The electrode pattern consists of an interdigital electrode and a grating reflector that constitute a surface acoustic wave resonator, and the shorting thin wire is formed to electrically short-circuit between a pair of comb-shaped electrodes that constitute the interdigital electrode. A method of manufacturing a surface acoustic wave device according to claim 1, characterized in that: 3. After uniformly depositing a conductive thin film on the same piezoelectric substrate and etching it to form multiple sets of predetermined electrode patterns, the substrate is cut into multiple sets corresponding to these electrode patterns. When simultaneously manufacturing a plurality of surface acoustic wave devices by dividing, the conductor thin film is etched to form short-circuit thin wires in a lattice shape surrounding each electrode pattern during or before forming the electrode pattern. . A method of manufacturing a surface acoustic wave device, characterized in that the substrate is then cut on the short circuit busbar to divide the substrate into a plurality of pieces. 4. The electrode pattern consists of interdigital electrodes and grating reflectors that constitute a surface acoustic wave resonator, and the short-circuit thin wires electrically short-circuit between the pair of comb-shaped electrodes that constitute the interdigital electrodes during etching, and piezoelectric 4. The method of manufacturing a surface acoustic wave device according to claim 3, wherein the interdigital electrodes are formed so as to be electrically open when cutting the flexible substrate.