JPS62143811A - Synthesis of molybdenum or tungsten silicide - Google Patents

Abstract

PURPOSE:A mixture of high-purity Mo or W powder with high-purity Si powder is combined with synthesized silicide powder, then allowed to react with each other to give the titled silicide which can be readily powdered, because the particles are hardly sintered. CONSTITUTION:An Mo or W powder of high purity is mixed with an Si powder of high purity, preferably at a molar ratio of 1:(2-3.5), further the mixture is combined with a silicide powder which has been synthesized and crushed in an amount of about 2-40wt% based on the mixture. They are thoroughly mixed and heated at about 800-1,400 deg.C in a hydrogen or vacuum atmosphere to give the titled silicide. The addition of the synthesized silicide almost prevents the product from sintering to keep it readily crushable. Thus, the crushing costs are reduced. Moreover, the contamination of the product in the crushing is remarkably decreased to give the product of high quality. Thus, the product is satisfactorily used to make targets for semiconductor devices.

Description

DETAILED DESCRIPTION OF THE INVENTION High purity raw material silicon powder and raw molybdenum or tungsten powder are used. In particular, for the production of targets used in the electronic industry, it is desirable to have a low content of radioactive elements, alkali metals, and transition metals. High purity silicon powder is easily available commercially. Regarding molybdenum and tungsten, technology has been established to prepare high-purity products with few impurities, and furthermore,
Several methods have been proposed for this improvement.

Such molybdenum or tungsten powder and silicon powder are already synthesized at a molar ratio of 1:2 to 55, and the pulverized synthetic silicide powder is added to the mixture in an amount of 2 to 5 of the above mixed powder amount.
Add 40% by weight and mix these thoroughly. Mixing is performed using, for example, a V-type mixer. Repeated synthetic silicide powder becomes silicide, that is, Mo (W)
812.0 w Mo(W) St 3.5 may be used, but it is preferable to use one having the same molar ratio as the mixed powder to be added. As the already synthesized and pulverized synthetic silicide powder referred to in the present invention, previously synthesized powder may be used repeatedly, or newly synthesized powder may be used.

Synthesis is performed in hydrogen or vacuum atmosphere at 800 to 1400
It is carried out by heating to °C. In this case, silicon tetrachloride may be used as a catalyst, in which case about 95
Synthesis is possible at 0°C. Synthesis conditions are not specified in the present invention.

The more the amount of synthetic silicide powder is repeatedly added, the more silicide with good pulverizability will be synthesized. By adding 2%, pulverization can be easily achieved by grinding, and the effect of the addition is observed. Therefore, in the present invention, 2% is set as the lower limit of the amount of repeated addition. By adding 15% or more, silicide can be obtained that easily becomes powder even if it crumbles. However, if the amount of repeated addition is too large, the synthesis reaction will be hindered, the pulverization effect will also be saturated, and the manufacturing cost will increase. As a result of experiments, the upper limit was set at 40%.

In this way, a synthetic silicide with good pulverizability is obtained. For your reference, to briefly describe the subsequent process, synthetic silicide is pulverized using a ball mill or other pulverizer.
It is classified into 35 to 45 mesh under to produce synthetic silicide powder.

Conventionally, this pulverization step was difficult, leading to increased costs and the introduction of contaminants, but the present invention dramatically reduces the burden of the pulverization process □ After this, the powder is sent to the target forming process, where it is compacted and vacuum sintered. Alternatively, a silicide sintered body is produced by pressure sintering and then finished into a final target by machining.

Effects of the invention t The grinding time is shortened, the cost of the grinding process is reduced,
The final product target becomes cheaper accordingly.

2. Contamination during crushing is drastically reduced, making it possible to manufacture targets that require high quality, especially for semi-4.4-body devices.

Example High purity molybdenum powder and high purity silicon powder in a molar ratio of 1:
The silicide powders blended in 2.2 and already synthesized are shown in Table 1.
Add as shown and mix in a V-type mixer, 10-”)-
The synthesis was carried out at a vacuum atmosphere width of about 1250°C. Synthetic silicide powder was pulverized in a mortar to examine the ease of pulverization. A similar experiment was conducted with tungsten. Table 1 shows the results.
Shown below.

Table 1 ×: Poor crushability.

○: Good grindability, can be ground into powder.

◎: Very good grindability, can be ground into powder by pounding.

,・−2′1 Agent's name Motohiro Kurauchi 1 1-　-' Same as Hiroshi Kazama゛）

Claims (1)

[Claims] 1) In a method of synthesizing molybdenum silicide or tungsten silicide from molybdenum powder or a mixed powder of tungsten powder and silicon powder, a silicide with good crushability is synthesized by adding synthesized silicide powder to the mixed powder. A method for synthesizing molybdenum or tungsten silicide, characterized by: