JPS6021862A - Target for high frequency sputtering - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a target porcelain for high frequency sputtering used for manufacturing filters and delay lines using surface acoustic waves used in video tape recorders, television receivers, etc. That is, the present invention relates to a high-frequency sputtering target for obtaining a thin film piezoelectric crystal of zinc oxide.

Conventional Structure and Problems Conventionally, zinc oxide target materials used in high-frequency sputtering have been zinc oxide powder or press-molded products thereof, and parallel plate targets have been used.

However, with these target materials and shapes, the area in which a vertical C-axis piezoelectric crystal film can be obtained is limited to only parallel to the target, making it difficult to mass-produce. However, it was not possible to obtain a piezoelectric crystal film of good quality. It was also difficult to obtain a crystalline film with a diameter of 1 0 μm or more. To address these problems, a target material in which lithium or manganese is added to zinc oxide has already been developed to improve C-axis orientation (Japanese Patent Laid-Open No.
-119996, Special Publication No. 57-1153) have been proposed. In order to obtain a thick film of 10 μm or more,
The sintered get is sintered to withstand high applied voltage, and the sintered density is approximately 95%, which is extremely dense. However, all of them were parallel plate type target porcelains, which lacked mass productivity.To address these problems, the present inventors have also proposed an improvement in the method of manufacturing target porcelains (Japanese Patent Laid-Open No. 53 -148706
issue). However, it has been difficult to produce target porcelain with a high yield with a complicated shape such as a curved surface that matches the cathode of the ivy device and has excellent dimensional accuracy. The yield rate of products using piezoelectric crystal films was 50 to 60% at most.Of course, there are many possible causes of product defects, but it cannot be denied that one of the causes is variation in the quality of the target porcelain itself. It was true.

OBJECTS OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a high-frequency sputtering target that can obtain an excellent piezoelectric crystal film at a high yield. There are two types of piezoelectric crystal films used in surface wave filters, etc.: thick ones of 10 μm or more and very thin ones of around 1 μm.The present invention has an advantage in obtaining thin piezoelectric crystal films of around 1 μm. The purpose is to obtain a target for high frequency sputtering.

Structure of the Invention The present invention uses zinc oxide as a main component and produces S through a pulverization process.
Using a powder containing 102 silicon and suppressing it to a maximum of 1.0 atoms, the density of the sintered body is 3.6 to 3.9 g/ct.
The present invention relates to a target ceramic for high frequency sputtering which is Il and has a fine and uniform crystal grain size of 0.5 to 2.0 μm.

Description of examples Examples of the present invention will be described below.

First, commercially available zinc oxide powder was calcined in air at 850°C, and then ground in a ball mill with agate cobbles.

At this time, S102 is mixed as an impurity. The particle size after pulverization is 1.6±0.2 μm.

After drying the slurry, adding a caking agent and granulating it,
It is formed into a hollow cylindrical shape as shown in FIG.

The density of the molded body 1 thus obtained is 3.1 to 3.
5, j9/Cf1. This molded body 1 was heated to 850°C.
The target porcelain was fired and solidified in the atmosphere at 1000° C. for about 2 hours to obtain a target porcelain having a density of 3.6 to 3.9 g/crA. The crystal grain size of this target ceramic is fine and uniform in the range of 0.5 to 2.0 μm.

By using the target ceramic thus obtained for sputtering, it was possible to obtain an excellent piezoelectric crystal film with a high yield rate. Table 1 below shows the density of the target porcelain and the yield rate for the target porcelain dimensions, as well as the yield rate of the surface acoustic wave filter manufactured using the piezoelectric crystal film obtained using the target 7) porcelain. Shown in the table.

(Samples with arrows are comparative samples and are outside the scope of the present invention.

Moreover, the target porcelain non-defective rate is about 20 pieces.

) Among the comparative samples, AS to A8 are not practical because the yield rate of the target magnetic heat l itself and the yield rate of the filling obtained using it are low. Furthermore, although the fill rate of flat 1 is relatively high, the strength of the target porcelain itself is poor because it is close to an unsintered state, and it is necessary to lower the voltage applied to the cathode.

Therefore, the sputtering rate required to form the piezoelectric crystal sword body is low, which is also not suitable for practical use. The flat plate 4 is a conventional target porcelain. Figure 2 shows the relationship between firing temperature and density; A4 is a porcelain obtained at a temperature where grain growth has just begun, and a density distribution curve is likely to occur in the target porcelain.

This non-uniform distribution of density caused non-uniform thermal expansion when a voltage was applied to the cathode to stop the temperature, leading to abnormal discharge and cracking of the target porcelain.

In this regard, A2 and A3 of the present invention have a uniform grain size of 0.5 to 2.0 μm and no abnormality was observed during use of the target porcelain.In addition, silicon was added to the zinc oxide sintered body as an impurity at a maximum of 1. This is because the inclusion of silicon lowers the axial self-direction of the piezoelectric crystal film and lowers the yield rate of filters. Therefore, it is limited to the permissible limit.

Effects of the Invention The present invention provides a target porcelain for high frequency sputtering, which has a high yield rate of target porcelain and can improve the yield rate of products manufactured using the target porcelain. It is something that can be done. At present, the correlation between the characteristics of the target device and the characteristics of products using piezoelectric crystal films is not necessarily clear.

FIG. 3 shows, as an example, the relationship between sintered body density and dielectric constant.
Although the dielectric constant of YTL target porcelain is low,
This relationship is currently under consideration.

As mentioned above, in the present invention, 3,6 to 3°9jj/ct
The sintered body density is d and the crystal grain size is 0.6 to 2.0μ
The target for high frequency sputtering of No. m is easy to manufacture, has a high yield rate, and has excellent durability, and by using this target ceramic, it is possible to improve the productivity of the final product. Currently, surface wave devices are becoming more widespread, and the number of products using piezoelectric crystal films of zinc oxide is also increasing, and the target porcelain of the present invention is expected to contribute to these application fields. .

[Brief explanation of drawings]

FIG. 1 is a half-sectional view of a hollow cylindrical target after molding in an example of the present invention, and FIG. 2 is a characteristic diagram showing the relationship between firing temperature and sintered body density of a zinc oxide target explaining the present invention. FIG. 3 is a characteristic diagram showing the relationship between the density and dielectric constant of the zinc oxide sintered body.

Claims (1)

[Claims] High frequency sputtering consisting of a zinc oxide sintered body containing a maximum of 1.0 atoms of silicon, with a sintered body density of 3.6 to 3.9 g/ctA and a crystal grain size of 0.5 to 2.0 μm. target.