JPS6239827B2 - - Google Patents

Abstract

PURPOSE:To enhance the material yield in the manufacture of a semiconductor simply by composing a tungsten slag of sintered tungsten containing less than 0.5wt% of Ni. CONSTITUTION:Ultrafine amount of Ni is added to metal tungsten powder of stock material, is activated and sintered at 1,800-1,950 deg.C of relatively low temperature, thereby obtaining a sintered material of high density capable of sufficiently enduring against use as a semiconductor tungsten slag. In this case, the Ni adding amount may be that to be activated and sintered, but when it exceeds 0.5wt%, the growth of the crystal grains becomes remarkable, and it affects adverse influence to the physical properties of the tungsten slag.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tungsten slag used in semiconductor devices.

Tungsten slag has conventionally been manufactured by the following method. That is, metal tungsten powder is press-molded to form a compact, which is then electrically heated to a high temperature of approximately 3000°C to form a rod-shaped sintered body (ingot), which is then subjected to swaging processing and other necessary processes. If so, wire drawing is performed to obtain a wire or rod of a predetermined thickness. Next, the wire or rod thus obtained was subjected to straight-down processing, then centerless ground to a desired outer diameter dimension, and then cut to a predetermined dimension to form a tungsten slug.
However, such a conventional manufacturing method requires grinding margins and cutting margins, resulting in poor material yield, and also requires a long manufacturing process, resulting in high manufacturing costs.

The present invention improves the above-mentioned drawbacks of conventional tungsten slags and provides a tungsten slag for semiconductors that is excellent in economy and resource saving, and will be described below.

The tungsten slag according to the present invention is characterized in that it consists of a sintered body of tungsten containing 0.5% by weight or less of nickel. When pure tungsten powder without the addition of nickel is press-molded and sintered, the specific gravity is only about 90% of the true specific gravity even when heated to about 3000°C, as mentioned above, and it cannot be used as tungsten slag for semiconductors. However, by adding a small amount of nickel to the raw material tungsten powder, so-called activated sintering can be performed.
Even when sintered at a relatively low temperature of 1950°C, a high-density sintered body that can be used as a tungsten slag for semiconductors can be obtained. In this way, it can be manufactured by sintering at a relatively low temperature, which is extremely advantageous in terms of industrial production. In this case, the amount of nickel (Ni) added may be such that activated sintering is carried out, but if the amount of nickel added exceeds 0.5% by weight, the growth of crystal grains will be significant and the physical damage of the tungsten slag will occur. It will have a negative impact on your character. According to experimental results, the preferred amount of nickel added is 0.03 to 0.5% by weight, and the more preferred range is 0.05 to 1% by weight.

Next, an example of the method for producing tungsten slag according to the present invention will be described.

FIG. 1 is a flowchart illustrating the manufacturing process of tungsten slag according to the present invention. In the figure, first, metallic tungsten powder and metallic nickel powder are mixed using a V-type mixer or the like. In this case, by adding and mixing an aqueous solution of nickel salt such as nitrate to metallic tungsten powder, drying, and then heating in a hydrogen atmosphere,
Nickel can also be added. If necessary, vinyl resin or the like is added as a granulating agent by dissolving it in an organic solvent, but it is desirable that the granulating agent has strong adhesive strength and a low evaporation temperature.
Next, this is granulated using a granulator, dried to remove the organic solvent, and then pressure-molded using a mechanical press to obtain a molded body. The molded body is pre-sintered and the granulating agent is completely volatilized before sintering.
As a finishing treatment, this sintered body is polished with a barrel polisher and then finished with a tumbler polisher to obtain a tungsten slag having the shape shown in FIG.

Next, embodiments of the present invention will be described.

Example 0.06% by weight of metallic nickel powder having an average particle size of 4 to 7 μm was added to a metallic tungsten powder having an average particle size of 0.5 to 2.0 μm and mixed to obtain a mixed powder. A vinyl resin dissolved in methanol was sprinkled onto this and thoroughly mixed. The amount of vinyl resin as a granulating agent added was 1% by weight based on the above mixed powder. Next, granulation was performed using a granulating agent to volatilize and remove methanol. The obtained granules were pressure-molded using a rotary press at a molding pressure of 2 to 3.5 t/cm ² to form small cylindrical compacts. This was placed in a hydrogen furnace and the temperature was gradually raised from room temperature to 1100°C to completely volatilize the granulating agent and perform pre-sintering. This processing time is 2 hours and 30 minutes,
It was held at 1100°C for 30 minutes. Instead of the above process,
The compact was directly inserted into a hydrogen atmosphere furnace maintained at around 400℃, held at 400℃ for 30 minutes to completely volatilize the granulation agent, and then held at 1100℃ for 30 minutes to perform pre-sintering. It is also possible to do so. Subsequently, the pre-sintered compact was heated in a hydrogen furnace at 1830°C for 3 hours to obtain a tungsten sintered body.

This was polished with a barrel polisher, and further polished with a tumbler polisher to obtain the desired tungsten slag. The specific gravity of the obtained tungsten slag was 18.3 to 18.4. For reference, the microscopic structures (×
150) is shown in Figure 3. From the same figure, nickel (Ni)
It can be seen that as the amount added increases, the crystal structure gradually becomes coarser.

Next, as shown in FIG. 4, lead wires 2 made of copper were spot-welded to the tungsten slag 1 obtained in the above manner, thereby producing a glass mold diode 3 as shown in FIG. 5. In this diode, a silicon wafer 4 is held between tungsten slugs 1 and 1 to which a lead wire 2 is connected.
A glass mold 5 is provided around it. The obtained glass molded diode had almost the same performance as the conventional one, and was sufficiently usable.

As is clear from the above description, the tungsten slag according to the present invention is easy to manufacture, has a high material yield, and is highly practical as an excellent semiconductor component.

[Brief explanation of the drawing]

FIG. 1 is a manufacturing process diagram illustrating the manufacturing process of a tungsten slag according to the present invention. Figure 2 is an external view of tungsten slag, Figure 3 a, b,
c, d, and e are micrographs of the tungsten slag, and FIGS. 4 and 5 are illustrations of how to use it. 1...Tungsten slug, 2...Lead wire, 3...
Glass mold diode, 4... silicon wafer, 5... glass mold.

Claims (1)

[Scope of Claims] 1. A tungsten slag for semiconductors comprising a sintered body of tungsten containing 0.5% by weight or less of nickel. 2. The tungsten slag for semiconductors according to claim 1, wherein the nickel content is 0.03 to 0.5% by weight.