JP2565880B2 - Manufacturing method of surface acoustic wave device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a method for manufacturing a surface acoustic wave device, and in particular to Li ₂ B.
_{The present} invention relates to a method of manufacturing a surface acoustic wave device using ₄ O ₇ as a substrate.

The (prior art) generally surface acoustic wave device, LiTaO ₃ as shown in FIG. 2, L
Formed by vapor-depositing Al on a piezoelectric substrate (22) made of iNbO ₃ , crystal, etc., then forming a comb-shaped electrode (21) using photolithography, and then cutting it into each surface acoustic wave device by dicing. To do.

By the way, a surface acoustic wave device using a substrate made of Li ₂ B ₄ O ₇ has better temperature characteristics than a surface acoustic wave device made of a LiTaO ₃ substrate and is more coupled than a surface acoustic wave device made of a quartz substrate. Due to its good coefficient, it has been spotlighted and commercialized today.

When a plurality of surface acoustic wave devices are formed on this Li ₂ B ₄ O ₇ wafer and cut (diced) into individual devices, as shown in FIG. 3, a blade (31) for cutting and a substrate ( To prevent heating with (32), cool with water (33). Incidentally, (34) is a wafer chuck.

By the way, as the properties of the Li ₂ B ₄ O ₇ single crystal material itself,
It has the property of dissolving water. Therefore, in this dicing process, as shown in FIG. 4 (a), water is dissolved in the portion (43) where the piezoelectric substrate (42) between the electrode fingers (41) is exposed, and the portion shown in FIG. Undesired grooves or groups (44) are formed as shown in (b). Therefore, in the surface acoustic wave device obtained by dicing, the same effect as that when the film thickness of the electrode finger is increased by the depth of the groove is produced, and the problem that the frequency deviated from the design frequency is prominently seen. .

(Problems to be Solved by the Invention) In view of the above-mentioned problems, the present invention provides a surface acoustic wave device that prevents the formation of grooves in a substrate made of Li ₂ B ₄ O ₇ by cooling water during dicing. The purpose is to do.

[Structure of Invention]

(Means for Solving the Problems) In order to achieve the above-mentioned object, the method for manufacturing a surface acoustic wave device of the present invention comprises forming a plurality of electrodes on a Li ₂ B ₄ O ₇ wafer and then forming a protective film. The basic structure is to form on this wafer, cut the wafer while adding water, and cut to each surface acoustic wave device.

(Operation) By taking the above-mentioned means, the protective film prevents water from coming into direct contact with the wafer, thereby preventing the Li ₂ B ₄ O ₇ wafer from being dissolved.

(Examples) Examples of the present invention will be described below with reference to FIGS. 1 (a) to 1 (e).

Li ₂ B with electrode (1) formed as shown in FIG. 1 (a).
_A photoresist or the like is coated on the ₄ O ₇ wafer (2) by a spinner to form a protective film (3) as shown in FIG. 1 (b). Then, using the dicing device shown in FIG. 3, water is added to prevent heating of the blade and the wafer, and the surface acoustic wave device (4) is cut into individual surface acoustic wave devices (4) as shown in FIG. 1 (c). To do. At this time, by the protective film (3),
The cooling water does not touch the surface of the wafer (2). Then, as shown in FIG. 1 (d), when exposed to O ₂ plasma and the resist protective film (3) is removed by ashing,
A surface acoustic wave device is obtained as shown in FIG.

Next, the effect of the surface acoustic wave device produced by the above-described embodiment will be described.

The inventors of the present invention compared the case where the above-described process was used and the case where the conventional technology was used for the prototype of the 200 MHz band resonator using the Li ₂ B ₄ O ₇ substrate.

Then, when the dicing was performed by the conventional technique, a groove having a depth of about 600 Å was formed at the end of the dicing, and the frequency was decreased by about 0.5 MHz. However, when dicing is performed using the process of the above-described embodiment, no groove is formed at the end of dicing,
It was confirmed that there was no frequency fluctuation.

If the protective film is formed on a surface other than the main surface on which the electrode is formed, it is possible to prevent the other surface from being dissolved by water.

〔The invention's effect〕

As described above, the present invention prevents welding of the Li ₂ B ₄ O ₇ substrate by cooling water that prevents heating of the blade and wafer during dicing, thereby preventing frequency fluctuations because no groove is formed. be able to.

[Brief description of drawings]

1 (a) to 1 (e) are simplified process diagrams for explaining an embodiment of the present invention, FIG. 2 is a schematic diagram for explaining a surface acoustic wave device, and FIG. 3 is a dicing device. A simplified diagram of
4 (a) and 4 (b) are schematic process diagrams for explaining the conventional technique. (1) …… Electrode (2) …… Li ₂ B ₄ O ₇ wafer (3) …… Protective film (4) …… Surface acoustic wave device

Claims (1)

(57) [Claims] 1. A first step of forming a plurality of electrodes on a wafer made of L _{i 2} B ₄ O ₇ , and a resist is applied on a main surface of a wafer on which at least a plurality of these electrodes are formed to form a protective film. A second step of forming, a third step of forming a plurality of surface acoustic wave devices by cutting the wafer while adding water, and a second step of exposing to O ₂ plasma and ashing and removing the resist protective film. 4. A method of manufacturing a surface acoustic wave device, comprising at least the step 4).