JPS60149214A - Electrode of surface acoustic wave element - Google Patents

Abstract

PURPOSE:To attain easily a high output and a long lifetime for an electrode of a surface acoustic wave element by providing a conductor different from the electrode material or an insulator layer on the surface of the electrode. CONSTITUTION:An aluminum electrode 1 of 1,000Angstrom thickness is formed on an LiTaO3 substrate 2. Then a surface oxide film 3 having larger thickness than a natural oxide film is formed by a heat oxidation process. Therefore a layer formed on the aluminum surface suppresses the movement of atoms on the surface of the electrode 1 as well as the swelling of atoms on the surface. This attains a high output and a long lifetime easily for a surface acoustic wave element.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an electrode for a surface acoustic wave device, and particularly provides an electrode suitable for a high-output device.

[Background of the invention]

It has been found that it is effective to add several inches of copper to suppress electrode deterioration. It has been reported that this method can produce approximately 10 times more output than pure aluminum electric lamps. However, the output level is still insufficient.

Furthermore, at the final stage of deterioration, a discharge occurs between the electrodes, destroying the device, but the cause of this is not clear.

[Purpose of the invention]

The present invention has been made for the purpose of suppressing discharge between the electrodes of a surface acoustic wave element and prolonging its lifespan until destruction, thereby making the element capable of withstanding high output.

[Summary of the invention]

It is well known that holes and protrusions are formed on the electrodes when the device is operated, but in addition to this, protrusions are formed between the electrodes towards the opposing electrodes, which can induce electrical discharges that can lead to destruction. , was discovered through detailed observation of the deterioration process.

It is thought that the life of the electrode can be improved by suppressing the occurrence of such protrusions on the side of the electrode.

[Embodiments of the invention]

An aluminum electrode with approximately 1,000 layers of aluminum or copper added to it is formed on an LjTaOs substrate, and a center frequency of 610 MH2 is formed by normal photoetching.
A surface acoustic wave filter was fabricated. Then, for surface coating, we used thermal oxidation to form a surface oxide film that was thicker than the natural oxide film, and selective chemical vapor deposition to deposit a tungsten layer only on the very surface of the stain. did.

The tank sten layer has a thickness of approximately 200 mm and is uniformly formed on the side surfaces of the electrode. After the tungsten was deposited, the sample was heat-treated (400C x 1 h).

Two types were fabricated, one with and one without (hydrogen atmosphere).

In the case of the heat-treated one, a compound layer of tungsten and aluminum was formed. The life of five of each of the devices thus prepared was measured at room temperature under a 6W high power input condition. The results are shown in Table 1.

For those with a surface oxide film (up to 50 people), the average lifespan improves by about twice as much, but the loss hardly increases. For those with tungsten coated on the surface, the average lifespan is 4 to 5.
It will double, but the losses will also increase. When this is heat treated, this tendency becomes even more remarkable. Although it is possible to reduce loss by optimizing electrode placement, thickness, etc., it seems that the negative correlation between average life and loss will not change. Therefore, a balance must be struck between the two.

As explained above, the layer provided on the surface of aluminum or aluminum-copper alloy suppresses the movement of atoms on the surface, and it is thought that the mound of atoms from the surface suppresses the particles. Therefore, substances having similar effects are not limited to those described here.

Furthermore, if an insulating material exists between the electrodes, there is no risk of short circuiting, but stress is exerted on the L' TaOs surface, leading to increased loss and fluctuations in characteristics. Therefore, it is desirable to form an insulating layer only on the electrode surface as much as possible.

Table 1 Lifespan and loss of various electrodes [Effects of the invention] As detailed above, according to the present invention, it is possible to easily achieve higher output and longer life of a surface acoustic wave element.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of the wiring part of a conventional surface acoustic wave device, and Figure 2-
FIG. 4 is a sectional view of the wiring portion of a surface acoustic wave device according to an embodiment of the present invention. 1... Aluminum or aluminum/copper alloy,
2...IjTaOs substrate, 3...Aluminum oxide, 4...Tungsten, 5...ht-w compound, mainly between Fig. 1, Fig. 2, Fig. 3, Fig. 4

Claims (1)

[Claims] An electrode for a surface acoustic wave device in which a conductor or insulator layer different from the electrode material is provided on the surface of the electrode.