JPS6120409A - Manufacture of surface acoustic wave element - Google Patents

Abstract

PURPOSE:To prevent the deterioration in characteristic caused by disconnection, and to raise the manufacturing yield by connecting the first and the second bamboo blind-shaped electrode fingers, through a connecting electrode, when forming a bonding pad electrode part. CONSTITUTION:Bamboo blind-shaped electrode fingers A11, A21 arranged interdigitally and a connecting electrode D are formed on a piezoelectric substrate 1 by a photolithographic technique. The inside of a surface acoustic wave transducer A has the same potential since both the electrode fingers are connected electrically by the connecting electrode D. Subsequently, a bonding pad electrode B is prepared, and heat treatment is executed. In these processes, even if a charge is accumulated on the electrode surface of the electrode fingers concerned A11, A21, no current flows since the inside of the transducer A has the same potential. Therefore, disconnection of the electrode finger caused by a current is not generated. When cutting or removing the electrode D, a laser or a photolithographic technique is applied.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for manufacturing a surface acoustic wave element that converts an electrical signal into a surface acoustic wave and a surface acoustic wave into an electrical signal using a piezoelectric substrate. .

(Prior Art) FIG. 3 shows an example of the configuration of a conventional surface acoustic wave conversion element. 1
is a piezoelectric substrate, A is a surface acoustic wave transducer, A...

A21 indicates interdigital electrode fingers that excite or receive surface acoustic waves, and B indicates a bonding pad electrode. Interdigital electrode fingers A1. and A21 are arranged in an interdigital manner as shown. The surface acoustic wave C excited by the surface acoustic wave transducer A is perpendicular to the interdigital electrode fingers AH+ A21, and is transmitted to the left and right of the interdigital electrode fingers All.

It propagates under A21. Furthermore, since surface acoustic waves propagate concentrated near the surface of the substrate, they are easily influenced by the shape of one surface. If the electrode film thickness of the interdigital electrode fingers A1□ and A2 is increased,
The propagation loss of the surface acoustic wave C increases due to the mass loading effect of the electrode metal, and if the electrode film thickness is made thinner, the loss due to increased conductor resistance increases. Usually, interdigital electrode fingers Al7. A2
The electrode film thickness of No. 1 is set around ](XX)A. Wire bonding technology is also used when mounting surface acoustic wave devices on packages.

The metal film thickness required for wire bonding is 2CXX)A or more. Therefore, the surface acoustic wave element uses a two-layer electrode structure of interdigital electrode fingers A, . . . A21 and bonding pad electrodes B. Photolithography technology is used as an electrode manufacturing method, and in the pretreatment process, it is also necessary to raise the substrate temperature to around 50°-1(1)°C.

(Problems to be Solved by the Invention) However, current flows when forming the bonding pad electrode. Due to this current, the interdigital electrode fingers A,..., A2
．． is the movement (migration) of the crystal grain boundaries of the electrode metal,
Alternatively, wire breakage may occur due to burnout.

Further, after the interdigital electrode fingers A11+A21 and the bonding band electrode B are created, heat treatment may be performed in order to increase the adhesion between the piezoelectric substrate and the electrode metal. Also in this heat treatment process, for the above-mentioned reason, the interdigital electrode fingers A,
, A2. Disconnection may occur. Interdigital electrode fingers A, A2. Due to the disconnection of the wire, the desired frequency characteristics cannot be obtained, and the yield rate also deteriorates.

Therefore, an object of the present invention is to solve the above-mentioned problems, prevent deterioration of characteristics due to wire breakage, and improve manufacturing yield.

(Technical means for solving the problems) The technical means of the present invention for solving the above problems is to interdigitally arrange first and second interdigital electrode fingers on a piezoelectric substrate, and to forming a connecting electrode that electrically connects the electrode fingers, then forming first and second bonding panod electrodes that partially cover the first and second interdigital electrode fingers, respectively; The method of manufacturing a surface acoustic wave device includes cutting or removing the connection electrode.

(Operation) The above technical means operates as follows. During the step of forming the bonding panode electrode section, the first and second interdigital electrode fingers are electrically connected via the connection electrode. Therefore, when creating the bonding pad electrode section,
Since the first and second interdigital electrode fingers are kept at the same potential, the above problem is solved. Further, the above-mentioned problems in heat treatment are also solved in the same way.

(Example) The present invention will be described below based on an example with reference to the drawings.

FIG. 1 shows a first embodiment of the present invention, in which 1 is a piezoelectric substrate, A
is a surface acoustic wave transducer, A) 1r A21 is an interdigital electrode finger that excites or receives surface acoustic waves, and D is a connecting electrode.

According to the first embodiment, first of all, the interdigitated electrode fingers A, .
2. and connecting electrodes are formed by photolithography. In this case, the interdigital electrode fingers A11°A2 and the connecting electrode fingers are usually created at the same time, but they may be created separately. Inside the surface acoustic wave transducer A, interdigital electrode fingers Al
Since 1 and A21 are electrically connected via the connecting electrode, they are at the same potential. Next, a bonding panode electrode is created using the same photolithography technique, and even if charge is accumulated on the electrode surface of A21, no current will flow because the inside of surface acoustic wave transducer A is at the same potential. . Interdigital electrode fingers A11゜A2□ caused by current
This has the advantage that no disconnection occurs. Interdigital electrode finger A
,,, Since A21 is electrically short-circuited by the connecting electrode, it does not have the function of exciting and receiving surface acoustic waves. In order to excite (receive) surface acoustic waves, it is necessary to cut or remove the connecting electrodes and electrically separate the electrode fingers A11+A21.

As a method for cutting or removing the connecting electrode layer, it is possible to apply a laser or photolithography technique.

In the first embodiment, a connecting electrode was laid on the surface acoustic wave propagation path, but as shown in FIG. The inside of the surface acoustic wave transducer has the same potential, and the above-mentioned effect is not lost. In addition, at the same time as making the surface acoustic wave device into a chip,
If you cut the connecting electrode (■), the interdigital electrode finger A11+
A21 is electrically isolated, and there is no need to cut the connection electrodes using a laser or the like after the surface acoustic wave element is made into a chip.

(Effects of the Invention) As explained above, according to the present invention, since the inside of the surface acoustic wave transducer is at the same potential during the bonding band electrode creation and heat treatment process, pyroelectric effect and electrostatic induction The advantage is that no current flows inside the surface acoustic wave transducer, and there is no disconnection of the surface acoustic wave excitation electrode finger due to migration or burnout caused by the current.As a result, the yield is improved, and in particular, the electrode finger width is reduced. This is effective for surface acoustic wave devices in increasingly narrow high frequency bands.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the first embodiment of this invention,
FIG. 2 is a diagram for explaining a second embodiment of the invention,
and FIG. 3 are configuration examples of conventional surface acoustic wave elements. 1... Piezoelectric substrate, A... Surface acoustic wave transducer,
A11+ A21... interdigital electrode fingers, B11. Bonding band electrode 1 C...Surface acoustic wave, D...Connection electrode, E...
Conductor for scribe.

Claims (1)

[Claims] First and second interdigital electrode fingers are interdigitally arranged on the piezoelectric substrate, and a connecting electrode is formed to electrically connect the first and second interdigital electrode fingers. 1. A method of manufacturing a surface acoustic wave device, comprising: forming first and second bonding pad electrodes that partially cover each of the contact electrodes, and then cutting or removing the connection electrodes.