JPH04207513A - Production of surface acoustic wave element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method of manufacturing a surface acoustic wave device.

[Prior Art] The structure of a conventional surface acoustic wave filter is shown in FIG. In the figure, reference numeral 10 indicates a surface acoustic wave filter, and 2
3 is a manual electrode, 3 is an output electrode, 5 is a piezoelectric substrate, and 7 is an end surface of the substrate.

Now, when an electric signal is input to the input electrode 2, the piezoelectric substrate 5
An excitation wave is generated, this excitation wave reaches the output electrode 3, and is converted into an electric signal again at the output electrode 3.

The input electrode 2 and the output electrode 3 are designed so that the excitation wave reaching the output electrode 3 has desired frequency characteristics.

In this case, in order to obtain the desired frequency characteristics, it is necessary to suppress the response of unnecessary waves other than the desired surface acoustic wave S1, and these unnecessary waves are those that are reflected from the substrate end face 7 and reach the output electrode 3. surface acoustic wave S2, which is radiated from the human-powered electrode 2 into the piezoelectric substrate 5, is reflected on the back surface of the piezoelectric substrate 5, and reaches the output electrode 3; and a resonant frequency that depends on the thickness of the piezoelectric substrate 5. There are resonant waves caused by thickness-shear wave resonance, etc.

These unnecessary waves deteriorate the frequency characteristics as shown in FIG. That is, the surface acoustic wave S2 that is reflected from the substrate end face 7 and reaches the output electrode 3 causes ripples on the passband characteristics (FIG. 5, part a), propagates inside the piezoelectric substrate 5 and reaches the output electrode 3. Due to the arriving bulk wave Bl, the high-frequency side stopband sidelobe level increases (FIG. 5, part b).

Furthermore, due to thickness-shear wave resonance, the low-frequency side stopband sidelobes become periodically large. Ripples occur in the band, deteriorating the characteristics (Fig. 5, part 0).

Among these, the passband characteristics and the stopband characteristics near the passband are important characteristics that determine the performance of the filter, and it is necessary to sufficiently suppress unnecessary waves that degrade these characteristics.

In order to suppress the above-mentioned unnecessary waves, a method of coating a surface wave absorbing material and defining grooves on the back surface of a piezoelectric substrate as shown in FIG. 6 has conventionally been used.

In FIG. 6, reference numeral 6 is a surface wave absorbing material for suppressing unnecessary surface waves, and 8a to 8h are grooves for suppressing thickness shear resonance.

Note that the same components as in FIG. 4 are given the same reference numerals.

In this case, the surface acoustic wave S2 reflected by the substrate end face 7 can be relatively easily treated by cutting the end face of the piezoelectric substrate 5 diagonally or by increasing the area where the surface wave absorbing material 6 is placed. It is possible to suppress it.

However, in order to suppress thickness shear wave resonance, the piezoelectric substrate 5
The grooves 8a to 8h on the back side of the plate are formed deeply, or
A method such as increasing the number of grooves 8a to 8h is required,
Groove 8 is cut using a cutting device used when cutting substrates, etc.
A method of cutting from a to 8h was used.

A schematic diagram of this cutting lFr device is shown in FIG.

In the figure, reference numeral 12 indicates a cutting device, which includes a stage 14 for fixing the piezoelectric substrate 5, a blade 16, and an arm 1.
8, and includes a drive source for the stage 14 and a drive source for the arm 18 (not shown).

In this case, the stage 14 to which the piezoelectric substrate 5 is fixed is displaced in the direction of the arrow X in FIG. 7 by the urging of a drive source for the stage 14 (not shown), and is positioned below the blade 16. Next, the arm 18 is displaced in the direction of the arrow 2 in FIG. 7 by the urging force of the drive source for the arm 18 (not shown), and the piezoelectric substrate 5 is cut by the blade 16 rotating at high speed, and a groove is formed in the back surface 20 of the piezoelectric substrate 5. 22 is formed.

Through such cutting, grooves 2 are formed on the back surface 20 of the piezoelectric substrate 5.
2, if the cutting speed is increased, microcracks will occur in the piezoelectric substrate 5, reducing its reliability as a surface acoustic wave element. Furthermore, if the piezoelectric substrate 5 has a large area and the grooves 22 are formed at a close pitch, there is a disadvantage that cutting the grooves 22 requires a lot of time. Since the bulk wave B1 is easily reflected, fine particles such as alumina or silicon carbide are sprayed by sandblasting to make the back surface 20 of the piezoelectric substrate 5 rough. In this method, the roughness of the back surface 20 of the piezoelectric substrate 5 can be changed by changing the size of the sprayed particles, but it is difficult to form very large irregularities. Therefore, although it is effective when the frequency of the bulk wave B1 is high and the wavelength is short, no effect could be expected when the frequency is low.

Furthermore, the surface acoustic wave filter 10 has a diameter of 3 to 4 inches.
It is manufactured by forming multiple identical patterns on a piezoelectric substrate 5 such as iTa03 or L+NbO3 by photolithography, but each chip of the surface acoustic wave filter 10 is usually small, and each chip is cut after pattern formation. A process is required. Normally, the cutting device shown in FIG. 7 is used to cut the piezoelectric substrate 5.

Among surface acoustic wave filters, multi-strip couplers (
An example of a type of filter using MSC) is shown in FIG.

In FIG. 8, reference numeral 30 is a piezoelectric substrate, 32 is a surface acoustic wave filter, 34 is an output electrode, 36 is a manual electrode, 3
8 indicates MSC.

Although this method can achieve good out-of-band characteristics, it has the disadvantage that the chip area becomes large because the input electrode 36 and the output electrode 34 have separate propagation paths.

In this case, a plurality of chips arranged as shown in FIG. 9a are cut by a cutting device, but if they are arranged as already shown in FIG. 9, the chip area can be reduced.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional technology, there is no cutting device capable of cutting the chip into the shape shown in FIG. 9, and the chip cannot be cut into the desired shape. There is a problem that the area cannot be reduced.

The present invention solves this kind of problem by using a mask made of metal or the like to form a desired pattern on a piezoelectric substrate, and a method such as sandblasting to spray small particles such as silicon carbide. It is possible to form irregularities on the back surface of a piezoelectric substrate in a short time, and furthermore, it is possible to cut the chip into a desired shape. It is an object of the present invention to provide a method for manufacturing a surface acoustic wave device, thereby manufacturing a surface acoustic wave device at low cost and with high performance.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a surface acoustic wave element that extracts a signal having a predetermined frequency by utilizing surface acoustic waves. The method is characterized in that the substrate is processed into a desired electrode finger shape by masking the substrate with a mask having a mask and spraying fine particles onto the mask.

[Function] In the method for manufacturing a surface acoustic wave device according to the present invention described above, a substrate is masked with a mask having a pattern of a desired shape, and fine particles such as silicon carbide are sprayed onto the mask to mask the substrate. This has the effect that it can be processed into a desired electrode finger shape.

[Example] The method for manufacturing a surface acoustic wave device according to the present invention will be described in detail below with reference to the accompanying drawings, by giving preferred examples in relation to the apparatus for implementing the method.

FIG. 1 shows a first embodiment. In the figure, reference numeral 40 indicates a piezoelectric substrate of a surface acoustic wave filter, 42 a mask made of metal or the like, 44 sandblasting, and 46 a slit provided in the mask 42.

The apparatus for carrying out the method for manufacturing a surface acoustic wave device according to this example is basically configured as described above. The action and effect will be explained.

First, the mask 42 is aligned with the piezoelectric substrate 40, and fine silicon carbide particles are sprayed onto the entire surface from the direction of the mask 42 by sandblasting 44.
The piezoelectric substrate 40 in the slit 46 portion is scraped off except for the portion covered by the slit 46 .

That is, it is possible to form grooves equivalent to the grooves of the piezoelectric substrate 40 obtained when cutting with a timing saw, and the shape of the mask 42 is directly transferred to the piezoelectric substrate 40, but the piezoelectric substrate 40 is Since the depth of the groove etched by the particles of the cutting tool can be determined by the time during which the particles are sprayed, this method can be used to form irregularities on the back surface of the piezoelectric substrate 40 or to cut the substrate. .

Next, a second example in which the shape of the hole of the mask is changed is shown in the second example.
As shown in the figure.

As shown in Figure Z a, the hole 4 consists of a plurality of circular shapes.
When a gap is provided between the mask 50 and the back surface of the piezoelectric substrate 52 using the mask 50 having the piezoelectric substrate 50 disposed therein, the outline of the formed unevenness becomes blurred, resulting in a concave portion 5 having a cross section as shown in FIG.
4 is formed. Since such a recess 54 has a varying thickness, it is effective in suppressing resonant waves due to thickness shear wave resonance.

In addition, a mask 5 having a hole 56 as shown in FIG.
If complete cutting is performed using the MSC 8, the chip area of the element 60 using the MSC can be reduced, as shown in FIG.

Effect 2 of the Invention As described above, the surface acoustic wave device manufacturing method according to the present invention has the following effects and advantages.

Processing the piezoelectric substrate of the surface acoustic wave filter using a metal mask and a device such as sandblasting that sprays small particles such as silicon carbide creates grooves or irregularities that change the texture on the back of the chip. can be formed in a short time, and a surface acoustic wave element with less thickness shear wave resonance and bulk wave spurious can be manufactured at low cost. Furthermore, there is an advantage that the chip can be cut into a desired shape, and a small, high-performance, and inexpensive surface acoustic wave element can be provided.

[Brief explanation of the drawing]

FIG. 1 is a perspective explanatory view showing one embodiment of the method for manufacturing a surface acoustic wave device according to the present invention, and FIG. 2 is a second embodiment of a mask used in the method for manufacturing a surface acoustic wave device according to the present invention. and a partial vertical cross-sectional view of a surface acoustic wave device manufactured using this mask. FIG. An explanatory diagram of a surface acoustic wave element cut using a mask, Figure 4 is a diagram explaining the operation of a conventional surface acoustic wave filter, and Figure 5 shows the frequency characteristics of a conventional surface acoustic wave filter. Figure 6 is an explanatory diagram of a conventional surface acoustic wave filter to which a method for suppressing unnecessary waves has been applied, Figure 7 is an explanatory diagram of processing of a surface acoustic wave element in a conventional example, and Figure 8 is an explanatory diagram of a conventional surface acoustic wave filter. FIGS. 9A and 9B are diagrams showing the pattern arrangement of a surface acoustic wave filter using MSC in a conventional example. FIGS. 40 Piezoelectric substrate 42 Mask 44 Sandblasting 46 Slit 48 Hole 50 Mask 52 Piezoelectric substrate 54 Recess 56 Hole 58 ...Mask 60... Device patent applicant Japan Radio Co., Ltd. Applicant agent Patent attorney Takehiro Chiba IGI FIG, 2a F IG, 2b FIG, 9
b

Claims (3)

[Claims] (1) In a surface acoustic wave element that uses surface acoustic waves to extract a signal having a predetermined frequency, masking the substrate with a mask having a pattern of a desired shape,
A method of manufacturing a surface acoustic wave device, comprising processing the substrate into a desired electrode finger shape by spraying fine particles onto the mask. (2) The method of manufacturing a surface acoustic wave device according to claim 1, further comprising forming irregularities in a shape defined by a mask on the back surface of the substrate. (3) A method for manufacturing a surface acoustic wave device according to claim 1 or 2, characterized in that the mask is positioned at a very small distance from the substrate and particles are sprayed onto the mask.