JPS5916406B2 - Semiconductor supporting electrode plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor supporting electrode plate, and particularly to a supporting electrode plate made of a copper-carbon fiber composite material.

The semiconductor device includes a semiconductor substrate having at least one pn junction and a support electrode plate supporting the semiconductor substrate. The properties required of the supporting electrode plate are mainly that it has high thermal conductivity and electrical conductivity, and that it has a coefficient of thermal expansion that is equal or approximately equal to that of the semiconductor substrate.

5. Silicon, which is commonly used as a semiconductor substrate, has a coefficient of thermal expansion of about 3.5 x 16-6/°C, and tungsten or molybdenum has conventionally been used as the material for supporting electrode plates.

However, tungsten or molybdenum are not necessarily the best. Their coefficient of thermal expansion is 4.
The coefficient of thermal expansion is in the range of 5 to 5.5 x 10-6/°C, and although it is close to the thermal expansion coefficient of silicon compared to general conductive materials such as copper, silver, and aluminum, it is also quite different from silicon. be. Support electrode plates made of copper-carbon fiber composites have recently been discovered as an alternative to i5 tungsten or molybdenum.

The thermal expansion coefficient and electrical conductivity of this supporting electrode plate can be adjusted by changing the amount and arrangement of carbon fibers. Further, it can be made to have higher electrical conductivity and lower coefficient of thermal expansion than tungsten and molybdenum. The supporting electrode plate made of the copper-carbon fiber composite material can be manufactured by, for example, bundling several thousand copper-plated carbon fibers with a diameter of several μm, wrapping them around a mandrel in many layers, and hot pressing. can.

The bundle of hot-pressed carbon fibers exists in a spiral shape, and the copper-plated comrades are welded and integrated at the interface between the bundles. Through a series of studies, it has been found that when the semiconductor substrate is a disk, it is best to arrange the carbon fibers in a spiral pattern or in a plurality of concentric rings. In a conventional supporting electrode plate made of a copper-carbon fiber composite material, both the inner and outer rings of the spiral or ring have the same pi carbon content.

Note that in the following, when we refer to a ring, we also include a spiral unless otherwise specified. However, in a supporting electrode plate made of a copper-carbon fiber composite material, the arrangement of carbon fiber bundles is likely to be disordered during manufacture of the composite material, and as a result, the radial coefficient of thermal expansion of the supporting electrode plate may vary depending on the measurement position. It was easy to vary.

An object of the present invention is to provide a structure suitable for suppressing variations in the coefficient of thermal expansion in the radial direction of a supporting electrode plate made of a copper-carbon fiber composite material.

The present invention provides a supporting electrode plate made of a copper-carbon fiber composite material in which carbon fiber bundles are arranged in a ring, in which the outermost ring of the ring has a higher carbon concentration than the innermost ring.

The present invention has investigated the following points regarding the conventional supporting electrode plate in which the amount of carbon shedding is the same for both the inner and outer rings of the ring, and as a result,
This led to the invention.

(1) Disturbances in the arrangement of carbon fiber bundles are rare in the outer ring.

(2) Those with a large amount of carbon fiber generally have less disordered arrangement than those with a small amount of carbon.

(3) Since it can be said that the variation in the coefficient of thermal expansion in the radial direction is mostly determined by the disorder in the arrangement of the outer ring, the carbon concentration of the ring made of a bundle of carbon fibers can be determined by comparing the inner ring and the outer ring. By changing the number of outer rings and increasing the number of outer rings, the disorder in the arrangement of the outer rings is reduced.

In the present invention, as long as the outermost ring of the carbon fiber bundle ring has a larger carbon content than the innermost ring, the purpose can be achieved.

However, desirably, the carbon content should be increased continuously or intermittently from the inner ring to the outer ring. In this way, the disorder in the arrangement of the rings can be reduced toward the outer ring, and the effect of suppressing variations in the coefficient of thermal expansion in the radial direction of the supporting electrode plate, that is, anisotropy, can be enhanced. . In a method of manufacturing a support electrode plate by arranging copper-coated carbon fiber bundles in a spiral shape, when forming the outermost ring part, the copper-covered fiber bundles having a carbon content of 45 to 60% by volume are used. It is preferable to wrap it.

More preferably, the carbon content of the copper-coated carbon fiber bundle is 60
All rings should be formed using no more than vol%. If the carbon content exceeds 60% by volume, hot-pressing becomes difficult, and boards occur between bundles of carbon fibers, resulting in poor thermal conductivity and electrical conductivity. Carbon content is 45
If it is less than % by volume, the arrangement of the rings becomes disordered and the shape of the rings becomes wavy. According to the present invention, while reducing the amount of carbon fiber in the supporting electrode plate as a whole compared to the conventional one,
Furthermore, variations in the coefficient of thermal expansion can be suppressed.

Therefore, thermal conductivity can be increased compared to conventional ones. Furthermore, it is possible to increase the thermal conductivity of the central portion of the supporting electrode plate compared to other portions. FIG. 1 is a plan view showing an ideal arrangement of carbon fiber bundles in a supporting electrode plate 1 made of a copper-carbon fiber composite material.

As already mentioned, the carbon fiber bundle 2 is made up of several thousand carbon fibers each having a diameter of several μm. 3 is copper.

This supporting electrode plate 1 has the same coefficient of thermal expansion in both the X direction and the Y direction because the arrangement of the carbon fiber bundles 2 is not disordered. FIG. 2 shows a case where the arrangement of carbon fiber bundles 2 is disordered.

In this case, the radial thermal expansion coefficient of the supporting electrode plate 1 will vary depending on the measurement position. As described above, when a supporting electrode plate having a variation in thermal expansion coefficient is used, the heat cycle characteristics and thermal fatigue characteristics of the semiconductor device are significantly deteriorated. Comparative Example 6,000 carbon fibers with a diameter of 6 to 9 μm and copper plating of approximately 1 μm were bundled and passed through a slurry containing copper powder and an aqueous methyl cellulose solution, so that the amount of carbon fibers was 53% by volume. A copper-carbon fiber composite wire was obtained.

This composite wire has a diameter of 3r! r! Wrap it in a spiral shape around an nφ stainless steel rod and heat it at 350 to 400℃ for 1 hour.
Temporary sintering was performed by heating in hydrogen for an hour. The dimensions of the temporary sintered body are 35 mφ in diameter and 120 wr in thickness! It was n. Next, the stainless steel rod was pulled out, the hole was filled with copper powder, and the rod was placed in a graphite mold and hot pressed. The hot press conditions were: temperature 850-1000°C, holding time 1 hour, pressure 2501Cf/Cr! i and hydrogen atmosphere. Thickness after hot pressing is approximately 30mm 1 diameter is 35r1r1nφ
The thickness was shrunk to about 1/4. From now on, the diameter is 32
Four supporting electrode plates each having a diameter of mφ and a thickness of 3 rfr1n were collected.
The arrangement of carbon fiber bundles is disordered as shown in Figure 2, and the coefficient of thermal expansion in the diametrical direction is 3.6 to 7.
．． It varied widely within the range of 3×10″6/°C.
Two types of supporting electrode plates in which the amount of carbon shedding increases from the inner ring to the outer ring of the spiral O were manufactured using the same manufacturing method as in the Examples and Comparative Examples.

One of the spirals of the carbon fiber bundle has 4 windings, and the other has 7 windings.
It is heavily rolled. The carbon content of the outer ring is 53% by volume for both types.
The amount was decreased by 7% by volume toward the inside.
The amount of carbon was reduced by reducing the amount of copper plating and the amount of copper powder in the slurry. In addition to this, the number of carbon fibers may be changed. The gap between the spirals of the carbon fiber bundle is approximately 4 for a quadruple winding! Frlnl 7-fold roll is approximately 2.3
I was disappointed. In all of the manufactured supporting electrode plates, the carbon fibers near the center of the electrode plate were slightly deformed into a wave-like shape, but the area near the outer ring was a relatively concentric undulation. The radial thermal expansion coefficients of these supporting electrode plates are all 3.6 to 4.4X.
It was confirmed that the coefficient of thermal expansion was between 10-6/°C, had less variation, and had a lower coefficient of thermal expansion than that shown in the comparative example. The electrical conductivity is 45 to 551 for the 4-layered one.
The ACS% was 50 to 551 ACS% for the seven-fold roll.

As is clear from the above embodiments, according to the present invention, it is possible to control the anisotropy of the coefficient of thermal expansion of a support electrode plate made of a copper-carbon fiber composite material and in which carbon fibers are arranged in a spiral or annular manner. I can do it.

[Brief explanation of drawings]

FIG. 1 is a plan view showing a preferred example of a supporting electrode plate made of a copper-carbon fiber composite material, and FIG. 2 is a plan view showing an unfavorable example of the supporting electrode plate. 11... Support electrode plate, 2... Carbon fiber bundle, 3... Erosion.

Claims (1)

[Scope of Claims] 1. A semiconductor supporting electrode plate comprising a plurality of rings of carbon fiber bundles arranged concentrically in copper or a copper alloy, in which the outermost ring of the rings has a higher carbon concentration than the innermost ring. A semiconductor supporting electrode plate characterized by having: 2. The semiconductor supporting electrode plate according to claim 1, characterized in that the carbon concentration increases continuously or intermittently from the inner ring to the outer ring of the ring. 3. The semiconductor supporting electrode plate according to claim 1, wherein the number of carbon fiber bundles in the outermost ring is greater than the number of carbon fiber bundles in the innermost ring. 4. The semiconductor supporting electrode plate according to claim 1, wherein the plurality of rings are spirally wound.