JPS61281611A - Surface acoustic wave resonator - Google Patents

Abstract

PURPOSE:To attain fine adjustment of frequency by tilting a line tying each electrode finger tip of a grating reflector to a center axis of a surface acoustic wave resonator. CONSTITUTION:Assuming the tilt to the electrode finger tip in the propagation direction of a surface acoustic wave to be theta and the period to be Lr, then the number N of cuttings of electrode fingers is decided by deciding one point (y) on the Y axis. In moving a cutter along the straight line in parallel with the Z axis through the point (y), N set of electrode fingers are cut off. The trimming is applied with high accuracy by using a mechanical processing device so as to have only to set the moving quantity of the cutter in the direction of the Y axis and the original in advance in this way.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a surface acoustic wave resonator, and more specifically, the present invention relates to a surface acoustic wave resonator, and more particularly, a grating reflector having a common electrode portion formed by tilting with respect to an axis parallel to the propagation direction of a surface acoustic wave. This invention relates to a surface acoustic wave resonator that facilitates fine adjustment of frequency.

[Background of the invention]

The method of manufacturing a surface acoustic wave resonator is usually to form a thin film of At or the like on a piezoelectric substrate and create an electrode pattern using photoI+lithography technology.
In order to obtain desired frequency characteristics, it is important to create electrode patterns with high precision. However, for a multi-frequency, high-Q surface acoustic wave resonator, the film thickness, line width, etc. must be determined strictly, and it is extremely difficult to satisfy the required accuracy using current process technology. For example, in creating an electrode pattern with a line width of 1 μm, the current technological limit is a dimensional accuracy of about 0.1 μm. For this reason, fine adjustment of the frequency has been carried out as a means of improving the manufacturing yield in device manufacturing. A method was used in which the electrode fingers were trimmed by six points using a laser processing machine, and fine adjustments were made by electrically opening them (Japanese Patent Laid-Open No. 52-1057).
52 Publication 2% 1985 Publication 122217). At this time, the number of electrode fingers trimmed with a laser processing machine and the center frequency change Δfμ. For example, there is a relationship as shown in FIG. 2, and a predetermined frequency fine adjustment is performed by performing trimming according to the diagram. However, the conventional wave technique described above requires a laser processing machine with excellent trimming accuracy.
General machining equipment has a drawback in that it cannot be used accurately, and there has been a demand for a technique for performing simple and accurate trimming using these machining equipment in the manufacturing process.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a surface acoustic wave resonator whose frequency can be finely adjusted without the need for special equipment.

[Summary of the invention]

As shown in FIG. 6, the lines connecting the electrode finger ends of the grating reflector are inclined with respect to the central axis AE of the surface acoustic wave resonator, and the line connecting each electrode finger end of the grating reflector is extended from the central axis to the nearest reflector electrode finger end. The key point is that the distance FR is made equal to or larger than the distance W to the farthest end of the electrode pattern used for signal input/output of the comb-shaped electrodes. The advantages of forming the grating reflector as described above will be discussed below.

In general machining equipment, the cutting cutter moves or rotates in one direction at high speed during cutting, and the cutting position is determined by moving the table on which the sample to be processed is fixed or the cutter holder three-dimensionally. It is controlled and processed. Therefore, in order to perform the above-mentioned trimming, three-dimensional positioning must be carried out at high speed and with high precision during the cutting operation, and in terms of processing accuracy and throughput, it is necessary to rely on a laser processing machine. However, according to the present invention, as shown in the partially enlarged view of the grating reflector shown in FIG. Once y is determined, the number N of electrode fingers to be cut is determined. In other words, (A'-) Ll tanθ< 1 < (N+-) L
By setting y in the range of r tan θ and moving the cutter along a straight line passing through the y point and parallel to the Z axis as shown in FIG. 5, N electrode fingers can be cut. In addition, the shortest distance FM from the central axis to the end of the gray-threaded reflector and the distance W to the farthest pattern end of the comb-shaped electrode are set as FR≧Wl, so in order to avoid damaging the comb-shaped electrode, There is no need to move the cutter during cutting, and trimming can be performed with high precision by simply setting the origin of the position and the amount of movement of the cutter in the Y-axis direction in advance using a machining device.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 shows an embodiment of the present invention, in which the piezoelectric substrate 1 has an sr.
Using a cut quartz substrate, comb-shaped electrodes and a grating reflector were made from a thin aluminum film with a thickness of 0.6 μm. The center frequency is 90Hz. The inclination θ of the electrode finger end of the grating reflector was 15 degrees. FIG. 6 shows an example of 8g2 of the present invention, in which the inclination θ of the electrode finger end is reversed from that of the first example, and other conditions are the same as those of the first example.
This is the same as the embodiment. In Figure 7, one end of the electrode finger is opened from the beginning to form a grating reflector.
In the first and second embodiments described above, it was necessary to trim both sides of the electrode finger end, but in this embodiment, trimming is required only on one side, which has the effect of shortening the trimming time. ii1!8 factors and Figure 9 are examples in which the present invention is applied to a two-aperture resonator.
Needless to say, the same effects as in the above embodiment can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, there is an effect that the electrode fingers of the grating reflector can be trimmed simply, quickly, and accurately using a machining device without using a special device such as a laser beam machine.

[Brief Description of the Drawings] Fig. 1 is a plan view of a surface acoustic wave resonator trimmed with a conventional laser processing machine, and Fig. 2 shows the number of trimmed electrode fingers and frequency change Δf/f. 3 is a plan view showing the first embodiment of the present invention, FIG. 4 is a diagram illustrating the present invention, and FIGS. 8 and 9 are other embodiments of the present invention. FIG. Explanation of symbols 1... Piezoelectric substrate 2... Denya Kushigata 31.
32... Grating reflector 41. 42... Electrically open reflector 5... Cutter 6.
...Cutting line No. 1 Ward No. 2 Trimmed fermented potatoes $60 a <、Nin steamed
3 Figure 6 Figure 7 Figure 8 Figure stem q 圀

Claims (1)

[Claims] In a surface acoustic wave resonator having a structure in which comb-shaped electrodes and a grating reflector are provided on a piezoelectric substrate, the angle of the grating reflector is A line connecting the ends of each electrode finger is inclined, and in the grating reflector,
The closest distance from the axis to the end of the electrode finger in the perpendicular direction is equal to or greater than the distance from the axis to the farthest end of the electrode pattern used for inputting and outputting signals of the comb-shaped electrode. A surface acoustic wave resonator characterized in that: