JPH0756927B2 - Method for manufacturing surface acoustic wave element - Google Patents

Description

The present invention relates to a method of manufacturing a surface acoustic wave device, and more particularly to a method including a step of facilitating measurement of characteristics in a wafer state.

[Conventional technology]

As is well known, a surface acoustic wave element has a structure in which an electrode pattern for forming an interdigital transducer, a reflector, or the like is formed on a piezoelectric substrate, and a sound absorbing material is added to both sides in the propagation direction of the surface wave. Have. In the actual manufacturing, prepare a wafer made of piezoelectric material, form electrode patterns for forming many surface wave elements on the wafer, add a sound absorbing material by baking, etc., and then The wafer is cut to obtain the device.

[Technical problem to be solved by the invention]

However, when the sound absorbing material is added by baking, electric charges are generated on the piezoelectric substrate due to the pyroelectric phenomenon due to the heat during baking. As a result, there is a problem that the electrode pattern for forming the surface acoustic wave element is broken due to the discharge based on the electric charge, or in the extreme case, the wafer is cracked.

Therefore, in order to cancel the charge by the pyroelectric effect,
As shown in FIG. 2, a method of electrically connecting all of the electrode patterns 2 for forming the surface acoustic wave device formed on the wafer 1 by the connection electrodes 3 formed on the wafer 1 is used. Has been.

Since all the electrode patterns 2 are electrically connected by the connection electrodes 3, even if a sound absorbing material is added by baking in that state, it is possible to effectively generate electric charges based on the pyroelectric effect due to heat during baking. Can be prevented.

However, when the connection electrode 3 as described above is formed, it is very difficult to measure and check the characteristics of each surface acoustic wave device in the state of the wafer 1. That is, in order to perform the measurement, it is necessary to cut the connection electrode 3 and make the electrode pattern independent for each surface acoustic wave element. Such cutting is performed by half-cutting the wafer. Therefore, the complicated work of measuring the characteristics of each surface acoustic wave element after half-cutting and then cutting the wafer again to obtain individual surface acoustic wave elements has been required.

In addition, there is a problem that the electrode pattern is scratched at the time of cutting for obtaining each surface acoustic wave device.

Therefore, it is an object of the present invention to provide a method of manufacturing a surface acoustic wave device, which can measure characteristics on a wafer as it is and effectively prevent electrode destruction due to a pyroelectric effect.

[Means for solving technical problems]

In the method of manufacturing a surface acoustic wave device according to the present invention, first, a wafer made of a piezoelectric material is prepared. On one side of this wafer,
A grid-like electrode pattern, at least one surface acoustic wave electrode pattern in each region surrounded by the grid-like electrode pattern, and at least the non-ground side electrode of the surface acoustic wave element electrode pattern is the grid-like electrode pattern. The electrode pattern is formed so as not to be connected to the electrode pattern. Next, on one surface of the wafer, with the grid-shaped electrode pattern being grounded, a sound absorbing material is added to the vicinity of each surface acoustic wave element electrode pattern by a method involving heating. Next, the characteristics of each surface acoustic wave device are measured on the wafer. Finally, a plurality of surface acoustic wave elements are manufactured by cutting the wafer into individual surface acoustic wave element units.

[Action]

The surface acoustic wave element electrode pattern for forming the interdigital transducer or the reflector is formed in each region surrounded by the grid electrode pattern. That is, the surface acoustic wave element electrode pattern is not electrically connected to the grid electrode pattern. Therefore, after the sound absorbing material is added, the characteristics of each surface acoustic wave element portion can be measured without performing any electrode cutting work in a wafer state.

Further, since the grid electrode pattern is formed so as to surround the surface acoustic wave element electrode pattern, even if the sound absorbing material is added by an additional method involving heating such as baking by grounding the grid electrode pattern. , All the potentials of the grid-shaped electrode pattern are ground potentials. Therefore,
The potential of the surface acoustic wave element electrode pattern that is not electrically connected to the grid-like electrode pattern rises to some extent due to the pyroelectric effect, but the circumference is surrounded by the grid-like electrode pattern and is fixed to the ground potential. Therefore, the increase in the potential of the surface acoustic wave element electrode pattern is suppressed. Therefore, the discharge phenomenon due to the pyroelectric effect can be effectively prevented.

[Explanation of Examples]

Hereinafter, a manufacturing method according to an embodiment of the present invention will be described with reference to the drawings.

First, a wafer 11 made of a piezoelectric material such as 36 ° Y-LiTaO ₃ or 128 ° Y-LiNbO ₃ is prepared.

Next, as shown in FIG. 1, on one surface of the wafer 11, in each of the lattice-shaped electrode patterns 12 and in each region surrounded by the lattice-shaped electrode patterns 12, one surface acoustic wave element As an electrode pattern, the interdigital transducer 13
Form a, 13b. The grid-shaped electrode pattern 12 and the surface acoustic wave element electrode pattern can be formed by any thin film forming method such as vapor deposition and baking, and the grid-shaped electrode pattern 12 and the surface acoustic wave element electrode pattern can be formed. The formation may be done separately or at the same time.

It should be pointed out that the electrical take-out portions of the interdigital transducers 13a and 13b are schematically illustrated.

Next, as shown in FIG. 3, sound absorbing materials 14 and 15 are added to both sides of the interdigital transducers 13a and 13b.
The sound absorbing materials 14 and 15 are added by baking a sound absorbing material such as silicon rubber or butyl rubber onto the wafer 11. In this case, the wafer 11 is heated by baking.
However, if the grid-shaped electrode pattern 12 is grounded, the pyroelectric phenomenon caused by heating the wafer 11 can be suppressed. Therefore, the pyroelectric effect effectively prevents the electrode patterns of the interdigital trussducers 13a and 13b from being destroyed.

Next, the electrical characteristics of each surface acoustic wave element portion are measured in the state of FIG. In this case, the electrode pattern for the surface acoustic wave element, that is, the interdigital transducer
Since 13a and 13b are not connected to the grid-shaped electrode pattern 12, the characteristics of each surface acoustic wave element portion can be easily measured without any electrode cutting work.

After the measurement, the wafer 11 is cut along the grid electrode pattern 12 to obtain the individual surface acoustic wave elements 17 shown in FIG. At the time of this cutting, if the width of the grid electrode pattern 12 is made narrower than the cutting width by the dicer, the grid electrode pattern 12 can be removed at the same time as the cutting.

However, the grid-like electrode pattern 12 may remain after cutting the wafer 11 into individual surface acoustic wave device units, and in that case, the remaining grid-like electrode pattern 12 is used as an electrode connected to the ground potential. Just connect it.

Further, in the above-described embodiment, the grid electrode pattern 12 is
Although one surface acoustic wave element is formed in each area surrounded by the grid electrode pattern 12, two or more surface acoustic wave elements are formed in each area surrounded by the grid electrode pattern. As formed, a grid electrode pattern may be formed. For example, as shown in FIG. 5, even if each surface acoustic wave element electrode pattern is formed so that two surface acoustic wave elements are formed in each area surrounded by the grid-like electrode pattern 12. Good. Even in this case, even if the wafer 11 is heated when the sound absorbing materials 14 and 15 are added, it is possible to effectively prevent the discharge due to the pyroelectric phenomenon due to the heating.

In addition, part of the interdigital transducers 13a and 13b may be electrically connected to the grid electrode pattern 12 within a range that does not hinder the measurement before cutting. For example, even if only the comb-teeth electrode connected to the electric potential on one side of the interdigital transducer 13a in FIG. 1 is connected to the grid-shaped electrode pattern 12, it can be measured without any problem if the side is measured as the ground potential during measurement. .

The electrode pattern for forming each surface acoustic wave element is the interdigital trussducer 13a,
It should be pointed out that it is not limited to 13b, and can be appropriately changed according to the desired surface acoustic wave element.

〔The invention's effect〕

As described above, according to the present invention, since at least one surface acoustic wave element electrode pattern is formed in each region surrounded by the grid-like electrode pattern, the wafer state can be maintained as it is.
The electrical characteristics of each surface acoustic wave device can be measured without performing any electrode cutting work. Therefore, it is possible to omit the complicated processing step of performing half-cut for measurement and further cutting the wafer as in the conventional example, so that the manufacturing cost of the surface acoustic wave element can be reduced. Not only that, the damage of the electrodes due to the complicated cutting process is unlikely to occur.

Moreover, since each surface acoustic wave element electrode pattern is surrounded by the grid-shaped electrode pattern, the potential of the surface acoustic wave element electrode pattern rises due to the pyroelectric effect when the wafer is heated when the sound absorbing material is added. The grid-shaped electrode pattern is suppressed by being fixed to the ground potential. Therefore, it is possible to reliably prevent electrode breakage and wafer cracking due to the pyroelectric phenomenon due to the heat.

[Brief description of drawings]

FIG. 1 is a partially cutaway plan view showing a state in which a grid-like electrode pattern and an electrode pattern for a surface acoustic wave element are formed in an embodiment of the manufacturing method of the present invention, and FIG. 2 is a surface acoustic wave element on a wafer in a conventional example. FIG. 3 is a plan view showing a state in which a working electrode pattern and connection electrodes are formed, FIG. 3 is a partially cutaway plan view showing a state in which a sound absorbing material is added in one embodiment of the present invention,
FIG. 4 is a plan view of a surface acoustic wave device obtained according to an embodiment of the present invention, and FIG. 5 is a partial cutaway plan view for explaining another embodiment of the present invention. In the figure, 11 is a wafer, 12 is a grid electrode pattern, and 13
Reference numerals a and 13b denote interdigital transducers as surface acoustic wave element electrode patterns, and 14 denotes a sound absorbing material.

Claims (1)

[Claims] 1. A step of preparing a wafer made of a piezoelectric material, and a grid-like electrode pattern on one surface of the wafer, and at least one surface acoustic wave element in each region surrounded by the grid-like electrode pattern. A step of forming an electrode pattern so that at least the non-ground side electrode of the surface acoustic wave element electrode pattern is not connected to the grid-like electrode pattern; In a state in which the electrode pattern of is grounded, a step of adding a sound absorbing material in the vicinity of each surface acoustic wave element electrode pattern by a method involving heating, a step of measuring the characteristics of each surface acoustic wave element on the wafer, And a step of cutting the wafer into individual surface acoustic wave element units.