JPS6192022A - Surface wave filter - Google Patents

Abstract

PURPOSE:To eliminate defect of stage due to the bent of a substrate and defect of crystal (zinc oxide) by constituting a surface wave filter comprising of a comb line electrode, a piezoelectric material and an opposed electrode to one side of a glass substrate and providing the same piezoelectric material or a material having a thermal expansion coefficient close to the former material to the other side. CONSTITUTION:A zinc oxide thin film 2 is provided to one major plane of the glass substrate 1 by the sputtering or the like and an SiO2 film 3 is provided by the sputtering so as to avoid the zinc oxide thin film 2 from being etched at the post etching process. Then aluminum is vapor-deposited to the major plane of the front side, the aluminum-made comb line electrode 4 is provided by the photo lithography, the zinc oxide thin film 5 is provided on it by the sputtering, the aluminum opposed electrode 6 is vapor-deposited on it, then the zinc oxide on the pad electrode connected to the comb line electrode is removed finally by etching to complete the wafer. Since the zinc oxide thin films 2, 5 are formed on both sides of the glass substrate line this way, the difference of thermal expansion due to temperature change hardly takes place and the bent of the glass substrate is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a surface wave filter used in video equipment, communication equipment, etc.

Conventional Structure and Problems Conventionally, this type of surface wave filter has a structure as shown in FIG. 6, in which an aluminum comb-shaped electrode (4) is provided on one main plane of a glass substrate (1). Zinc oxide (5) is applied thereon in a polycrystalline state by a method such as sputtering, and then an aluminum counter electrode (
6) was provided by a method such as vapor deposition.

According to this method, the glass substrate (1) and the zinc oxide thin film are repeatedly subjected to temperature cycles during various processing steps (for example, when the resist solution is hardened in the photolithography process, it is placed in a dryer at 150°C). (5) Due to the difference in expansion coefficient, the sea urchin has the disadvantage of warping as shown in Figure 7, and there is a problem that the sea urchin cannot be vacuum chucked in the cutting process of scribing or dicing. There is.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a surface acoustic wave filter that is free from warping, and is free from process defects and crystal (zinc oxide) defects caused by warping.

Structure of the Invention The surface acoustic wave filter of the present invention includes a surface acoustic wave filter section including a comb-shaped electrode, a piezoelectric material, and a counter electrode on one main plane of a glass substrate.

The present invention is characterized in that a material having the same coefficient of expansion as the piezoelectric material or close to that of the piezoelectric material is attached on the other main plane to prevent warping of the substrate.

DESCRIPTION OF EMBODIMENTS Hereinafter, one embodiment of the present invention will be described based on FIGS. 1 to 5.

As shown in FIG. 2, a zinc oxide thin film (2) is provided on one main plane of the glass substrate (1) in FIG.
) is not etched, a Sun film (3) is provided by a method such as sputtering as shown in FIG. This completes the configuration of the back side principal plane. Next, aluminum is vapor-deposited on the main plane of the front side, and aluminum comb-shaped electrodes (4) are provided using photolithography as shown in Fig. 4. Zinc oxide is sputtered on top of the comb-shaped electrodes (4) as shown in Fig. 5. Zinc oxide thin rS (
5), and further, an aluminum counter electrode (6) is vapor deposited on the zinc oxide thin film (5) and made by photolithography. Finally, the zinc oxide on the pad electrodes connected to the interdigitated electrodes is removed by etching to complete the wafer.

In this way, a thin film of 1iA of zinc oxide was applied to both sides of the glass substrate (1).
By adding (2) and (5), firstly, differences in expansion caused by temperature changes are less likely to occur, and the glass substrate (wafer) no longer warps.

In the above embodiment, a surface wave filter section was formed on one main plane of the glass substrate, and zinc oxide as a piezoelectric material used in the surface wave filter section was attached on the other main plane. A similar effect can be obtained if the material has a similar expansion coefficient to the piezoelectric material of the wave filter section.

As described in the detailed description of the invention, the surface wave filter of the present invention comprises a surface wave filter section consisting of a comb-shaped electrode, a piezoelectric material, and a counter electrode on one main plane of a glass substrate, and a surface wave filter section consisting of a comb-shaped electrode, a piezoelectric material, and a counter electrode on one main plane of a glass substrate. Since a material having the same coefficient of expansion as the piezoelectric material or close to that of the piezoelectric material is attached to the glass substrate, warping of the glass substrate is eliminated and the following effects are obtained.

■No more loss or destruction of chips due to wafer warping during scribing and dicing processes.

■Mask positioning in step 1 of the Dew Method is now easier, and scratches caused by "rubbing" of the resist are eliminated.

[Brief explanation of the drawing]

vinegar. (1)...Glass substrate, (2)(5)...Zinc oxide [piezoelectric material], (3)...S io2, (4)...
Comb-shaped electrode, (5)...Zinc oxide, (6)...Counter electrode representative Yoshi Morimoto French Book 1 Illustration / Diagram Z

Claims (1)

[Claims] 1. A surface wave filter section consisting of a comb-shaped electrode, a piezoelectric material, and a counter electrode is formed on one main plane of the glass substrate, and a surface wave filter section consisting of a comb-shaped electrode, a piezoelectric material, and a counter electrode is formed on the other main plane. Surface wave filter with similar materials.