JPS5843607A - Manufacture of surface acoustic wave filter - Google Patents

Abstract

PURPOSE:To obtain a surface acoustic wave filter of high yield, which causes no electric discharge between metallic cross electrodes, by providing a discharge preventing pattern by which metallic films constituted of plural cross electrodes are at the same potential. CONSTITUTION:A main pattern part 3 consists of a transducer part, a reflector part and a multistrip coupler part, and a line and a space constitute a cross electrode of 1.0-1.2mum, respectively. On its circumference, electrodes 4-7 forming a bonding pad are provided. Also, in a scribing area or timing areas 8, 9, or crossing these areas, discharge preventing patterns 10-13 are provided. According to such a constitution, charge of a substrate, which is generated by a temperature rise process can be neutralized by the discharge preventing patterns 10-13, therefore, no fine metallic pattern is fused by discharge, and it is possible to manufacture a surface acoustic wave filter with high yield.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a surface acoustic wave filter! I),
! Another object of the present invention is to provide a high-yield manufacturing method in which discharge is prevented.

Conventionally, in the manufacturing method of surface acoustic wave (SAW) filters, rounding, processing that slows down the heating rate, and process treatments have been used to reduce charging on the dielectric substrate surface during various ascending processes and processes that involve mechanical stress. By keeping the temperature low and handling as carefully as possible, we kept the charge caused by the current collection effect to a low level. However, as the size of metal cross electrodes becomes finer to about 1 μm, there is a drawback that the charging potential differs within the crystal surface, which discharges through the narrow gap of the cross electrodes and ruptures the HT electrode.

It is an object of the present invention to provide a high-yield method for manufacturing a SAW filter in which no discharge occurs between metal crossing electrodes.

The dielectric substrate used as the material for SAW filters is
Comparatively, the current collection rate P is also large. Therefore, in the present invention, by providing an electrode pattern for preventing discharge with the same potential K''-7- between metal films, which is composed of a plurality of crossed electrodes, the electrostatic charge generated in various processes is neutralized. This prevents the electrode from melting due to discharge.

Hereinafter, one embodiment of the present invention will be explained with reference to the drawings.

That is, 800MHg low loss, band pass! An example will be given of the ll8AW filter. Substrate 1 is LITaOs B6°X
-Y-cut single crystal plate, size 35cm x 30cm, thickness α
4 ■ One side mirror polished, back side finished to 600 0
Next, At as a metal film is vacuum-deposited to a thickness of 1000 nm on the crystal surface, and then a positive resist (AZ-1350J) is applied and prebaked at 90G for 20 minutes. Furthermore, the desired mask or reticle is rotated and exposed by contact exposure method or reduction projection exposure method, etc., and the phenomenon and post-bake (12
0G.

20 minutes) 11. Form pattern 2 by etching with a phosphoric acid-based chemical etching solution or by dry etching. After that, as a post-process, dicing,
Perform wire bonding and then wire bonding to complete the assembly.

The figure shows an example of the pattern of the filter. Main pattern part 3
The transducer part (the part that converts the input/output power into surface acoustic waves), the reflector part (the ninth part that reflects the surface acoustic waves generated in the transducer part), and the multi-strip coupler part. (For branching part of the surface wave to other parts) etc. 11. A, and 8. , 28, 8□□,
0 to □, 2 μm cross electrodes. Electrodes 4, 5, 6.7 constituting a bonding pad are provided around it. Further, a scribe area (a boundary line dividing each element) or a dicing pattern 10-18 for preventing discharge according to the present invention is provided. The discharge countermeasure pattern in this example is that after being divided into chips by dicing, etc., they are separated into chips and are divided into 8AW.
There is no effect on the original performance of the filter.

In order to investigate the effect of introducing the discharge countermeasure pattern, as an experiment,
As a result of examining the burnout of the At pattern and traces of discharge between the electrodes before and after heating the sample on a heating table at 200C for 10 minutes, the improvement rate was 20% for the discharge countermeasure pattern of 1 μm, 40% for the 2 μm pattern, and 3 μm further. In Batanes, it was 80%.

As explained above, according to the present invention, since the charge on the substrate caused by the step 1 process can be neutralized by the discharge prevention butter 7, an 8AW filter can be manufactured with a high yield rate without melting due to discharge of the fine metal pattern. is now possible.

In this example, after being divided into filter elements,
I have shown an example of a discharge prevention pattern or a slam designed to break up or disappear, but in applications where the operating frequency is relatively high,
By using an inductance tape or providing resonance conditions so that the impedance of the discharge prevention pattern becomes high at that frequency, it is also possible to create a pattern in which the various electrodes of i1 are short-circuited in terms of direct current. In this case, the discharge prevention pattern can be left as is even after the filter element is divided, so that discharge accidents caused by various tests once the element is completed can be prevented.

[Brief explanation of the drawing]

The figure is a diagram for explaining one embodiment of the present invention, and shows an example of a button of a surface acoustic wave filter provided with a discharge prevention pattern.

Claims (1)

[Claims] In a method for manufacturing a surface acoustic wave filter in which a plurality of intersecting metal finger electrodes are provided on a dielectric plate, a discharge prevention pattern is provided to make the potential between different electrodes the same. A method for manufacturing a surface acoustic wave filter for imaging.