JPH08167826A - Surface acoustic wave element - Google Patents

Abstract

PURPOSE: To prevent the generation of a damage caused by the discharge of electrostatic charge from electrodes formed on a surface acoustic wave element by preventing the damage of the element due to static electricity and gradually discharging charge accumulated in the electrodes. CONSTITUTION: Resistors 9, 9' are formed on a piezoelectric substrate 10 and both ends of the resistors 9, 9' are connected to crossing digital electrodes 1 to 4 in parallel. The resistors 9, 9' are formed by an organic material containing a thin film metal or a conductive material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface acoustic wave element for preventing electrostatic breakdown of a surface acoustic wave device.

[0002]

2. Description of the Related Art A surface acoustic wave device is usually constructed by forming interdigital electrodes made of an aluminum thin film on the surface of a voltage material. This interdigitated electrode interval is a minute interval of about 1 μm in the 900 MHz band, for example. It is known that if static electricity is generated or applied between the input terminals and between the output terminals in such a state, it is destroyed at about several hundreds of volts. Further, since the piezoelectric material used for the surface acoustic wave device has a high pyroelectric property, if the temperature changes during or after the device manufacturing process, electric charges are generated on the surface of the substrate, and the electrodes are destroyed by this discharge. Sometimes.

In order to prevent such destruction, for example, as shown in Japanese Patent Application No. 403953/1990, there is a technique of enclosing a gas having a high electric insulation strength in an airtight package. It cannot prevent electrostatic damage.
Also, as disclosed in Japanese Patent Application No. 3-79462, there is a technique of covering the back and side surfaces of a surface acoustic wave element with a conductive film to prevent discharge breakdown due to the pyroelectric effect.
There is a drawback that the number of steps formed on the side surface is large and the cost is high.

On the other hand, Japanese Patent Application No. 59-36539 proposes a technique for lowering the insulation resistance value between the input / output terminals of the package and the case in order to release static electricity after the device is mounted on the package. It has a drawback that it cannot prevent electrostatic breakdown during the process.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to prevent the destruction of the interdigitated electrodes due to static electricity generated in the surface acoustic wave element during the manufacturing process and after completion of the element.

[0006]

In order to achieve the above-mentioned object, the surface acoustic wave device of the present invention comprises a resistor formed on a piezoelectric substrate, and both ends of the crossed finger-shaped electrodes cross each other. The electrodes of are connected in parallel.

By adopting such a configuration, the resistance value between the interdigitated electrodes becomes the resistance value of the thin film resistor.
It is possible to prevent breakage of the interdigital electrode.

[0008]

The present invention will be described below with reference to the drawings.

FIG. 1 shows a plan view of an element of a surface acoustic wave device according to an embodiment of the present invention. Interdigital electrodes 1, 2, 3, 4 and wire bonding pads 5, 6, 7, 8 are formed on the piezoelectric substrate 10 by an aluminum thin film. A thin film resistor 9 is formed between the crossed finger-shaped electrodes 1 and 2 which intersect with each other, and a resistor 9 ′ is formed between 3 and 4. This thin film resistor may be a metal thin film different from aluminum such as titanium, tungsten and copper,
It may be an organic material containing a conductor. It may also be a semiconductor material.

Of the metals, aluminum can also be used. When aluminum is used, the material is the same as the electrode forming material, and therefore, there is an advantage that the thin film deposition apparatus may be the same. When using a metal having high electric conductivity such as copper or aluminum, the thin film needs to have a thickness of several A to several tens of A.

FIG. 2 shows another embodiment of the present invention. As a thin-film resistor, a thin thin-film pattern has a wavy shape and is lengthened to keep the resistance value above a certain value. The material for forming the wavy pattern of this thin film is the same as in FIG.
A conductive material such as a metal or a conductive organic material can be used.

The features of the embodiment of the present invention shown in FIG.
By making the line width sufficiently thin and making the length of the wavy pattern sufficiently long, this resistor is made of the same aluminum as the electrode forming material. Therefore, by making the film the same thickness as the electrodes, the interdigital electrodes,
It can be formed simultaneously with a bonding pad or the like.

By forming a resistor between the interdigital electrodes as shown in FIGS. 1 and 2, static electricity applied to or generated in the surface acoustic wave element during or after the manufacturing process of the surface acoustic wave element is Since it is gradually discharged through this resistor, there is an effect that the element can be protected from damage such as electrode destruction due to discharge between the interdigitated electrodes.

The resistance value of the resistor varies depending on the application of the surface acoustic wave device, and varies from a case where it can be used at several tens of times its input / output impedance (for example, 50Ω system) to a case where it is necessary at several hundred times. Designed individually.

[0015]

As described above, according to the present invention, the thin film resistor is formed on the surface acoustic wave element and the electrodes are connected in parallel with each other so that the static electricity on the element is gradually discharged. It has the effect of preventing the destruction of the electrode pattern due to discharge.

[Brief description of drawings]

FIG. 1 is a plan view of an embodiment of a surface acoustic wave device of the present invention.

FIG. 2 is a plan view of a second embodiment of the present invention.

[Explanation of symbols]

 1, 2, 3, 4 Interdigitated electrodes 5, 6, 7, 8 Bonding pads 9, 9'Thin film resistor 10 Voltage substrate

Claims (4)

[Claims] 1. A surface acoustic wave element formed on a voltage substrate, a resistor formed on the substrate, and a cross finger electrode connected in parallel to both ends of the resistor so as to cross each other. A surface acoustic wave device comprising: 2. The surface acoustic wave device according to claim 1, wherein the resistor is formed of a metal thin film. 3. The surface acoustic wave device according to claim 1, wherein the resistor is made of an organic material containing a conductive material. 4. The surface acoustic wave device according to claim 1, wherein the resistor is made of a semiconductor material.