JPS59136952A - Material for semiconductor substrate - Google Patents

Abstract

PURPOSE:To obtain a material, which satisfies both thermal conductivity and a thermal expansion coefficient and to which there is no problem, such as virulence, difficulty for acquistition, etc., by mixing and molding Cu powder at a specific rate and W powder, Mo powder or W-Mo alloy powder in specific grain size and baking the shape in a reducing atmosphere. CONSTITUTION:Cu Powder at a final product ratio of 5-20wt% and W powder, Mo powder or W-Mo alloy powder in 0.5-5mum mean grain size are mixed and molded, and baked in a reducing atmosphere. A Cu ratio is brought to 5- 20wt% in order to keep a thermal expansion coefficient within a range of 6-8 (X10<-6>/ deg.C). The mean grain size of W powder or Mo powder is brought to 0.5- 5mum because the bulk of powder is large and density on molding is difficult to increase owing to the air being contained among powder at pressing and molding at 0.5mum or less and the powder must be sintered at 1,500 deg.C or more in order to obtain a dense alloy with Cu, Cu disappears remarkably due to evaporation, the variability and variation of compositions are generated and an alloy of predetermined compositions is difficult to be acquired at 5mum or more.

Description

[Detailed Description of the Invention] In recent years, due to improvements in the operation speed of ICs, increases in the capacitance of transistors, and the appearance of Ga-As and FETs, it has become increasingly important to consider how to dissipate the heat generated in semiconductor devices when they are driven. This is a major problem as the particles are ejected through the package and out of the package. Therefore, it is preferable to use a material with high thermal conductivity for this substrate material.

Incidentally, in recent years, lamic packages using lamic have been frequently used as the package. In the case of this package, the substrate is a ceramic frame for taking out the electrodes (
or board). Therefore, A as a substrate material.
When using porcelain whose main component is l2O3, there is no problem because it is fired integrally with the ceramic frame (or plate) for taking out the electrodes, but in order to improve thermal conductivity, ceramics such as W or Mo are used for taking out the electrodes. When a material different from the frame (or board) is used as the substrate material, the following problems occur.

That is, when W, Mo, or the like is used as the substrate material, a brazing method using silver solder is usually used to join the ceramic frame (or plate) for taking out the electrode. In this case, since W, Mo, etc. have a large difference in coefficient of thermal expansion from ceramic, a problem arises in that the ceramic frame (or plate) is damaged due to thermal distortion during cooling after heating in the brazing process.

For this reason, a thin plate of Fe-Ni alloy or Fe-Ni-C0 alloy, which has a coefficient of thermal expansion close to that of ceramic, is interposed between the substrate and the ceramic frame (or plate).
Such a method is unfavorable in terms of heat conduction.

On the other hand, it has been considered to use BeO, which has good thermal conductivity and a coefficient of thermal expansion close to that of a seven-laminate frame (or board);
Since O is toxic, it is difficult to handle and manufacture, and furthermore, it is difficult to handle manually, making it impractical.

The present invention provides a semiconductor substrate material that satisfies both thermal conductivity and thermal expansion coefficient and is free from problems such as toxicity and difficulty in manual handling. W powder or tVI□ powder or W with an average particle size of 0.5 to 5μ
-Mo alloy powder is mixed and molded, and then fired in a reducing atmosphere.

In the present invention, the Cu ratio in the semiconductor substrate material is 5 to 20.
The coefficient of thermal expansion was set as wt% from 6 to 8 (XIO-”7°C
) to keep it within the range. That is, the coefficient of thermal expansion of heptaramic is 6.5 to 7.5 (XIO-6/"C),
This is because the coefficient of thermal expansion needs to be in the range of 6 to 8 (x 10-6/''C) in order to prevent damage during the above-mentioned brazing process.

In addition, Ga-As, which has been widely used as a semiconductor element in recent years,
When using Ga-As, the thermal expansion coefficient is 6.7 (XIO
-〇/ ``C) and is extremely brittle compared to Si, so it is necessary to make the coefficient of thermal expansion of the substrate on which the element is mounted close to that of the element. From this point of view, the coefficient of thermal expansion should be set to 6 to 8 ( X 10
-0/°C), and for that purpose the Cu ratio must be 5
It is necessary to set it to ~20wt%.

Next, the reason why the average particle size of W powder and MO coarse powder is set to 0.5 to 5μ is that when the particle size is less than 0.5μ, the bulk of the powder becomes large when the mixed powder with Cu is molded using the normal press molding method. It is difficult to increase the compaction density due to the air contained between the powders during compaction. This is because the fine powder that sinters adsorbs a large amount of oxygen and other gases on the powder surface and releases the adsorbed gas during firing, leaving many pores in the alloy after firing.

On the other hand, coarse particles W%Mo or W, M with an average particle size of 5μ or more.

In order to obtain a dense alloy with Cu using alloy powder of
It must be sintered at a high temperature of 500°C or higher.

However, at such high temperatures, Cu is rapidly lost by evaporation, resulting in variations and fluctuations in the composition, making it difficult to obtain an alloy with a predetermined composition. For this reason, the average particle size needs to be 5 microns or less.

However, in order to obtain a more preferable material in the present invention, the firing temperature is 1200°C to 1500°C and the firing time is 0.5°C to 1500°C.
It is preferable to bake at 2H.

That is, it is necessary for Cu to melt and fill the surroundings of the W particles during firing, and for the sintering of W, Mo, W, and Mo alloy particles to proceed, so the heating temperature is 1200°C or higher, preferably 1300°C or higher. Requires firing at high temperatures. However, as mentioned above (
It is undesirable to exceed 1500°C.

Moreover, it is difficult to obtain a stable alloy by firing outside of 0.5 to 2H.

Examples will be described below.

Example 0 WMo or W-Mo alloy powders having various average particle sizes as shown in Table 1 and copper powder of -325 mesh were blended into the composition shown in Table 1 and uniformly mixed for 3 hours using an Attrike mixer. The resulting powder was pressed into a size of 30 x 30 x 5/nIL at a pressure of 7 cm'', and then sintered in an H2 gas atmosphere under the hot sintering conditions (Table 1).

Note that sample numbers 7, 19, and 26 in Table 1 could not be obtained with a good stamped body by ordinary press molding, so they were sintered by isostatic pressing.

・Sample No. 11 in Table 1 is the same stamped body as sample No. 5, sintered at 1180°C This is a comparison sample that was repeatedly densified.

The thermal expansion coefficient and thermal conductivity of the thus obtained alloy were measured and the results are shown in Table 1.

Table 1 Sintered alloy Si of sample number 3.15.24 in Table 1
The IC parts used as the substrate material for the chip are IC
A7203 which is a Si chip or other surrounding group in the mounting process
Because the difference in coefficient of thermal expansion is small, no thermal distortion occurs, and the device has extremely good heat dissipation, so it was possible to obtain an IC with a long life and excellent reliability.

As described above, the semiconductor substrate obtained by the present invention is a material with excellent thermal conductivity and coefficient of thermal expansion, and there are no problems of toxicity or difficulty in obtaining it. This is a semiconductor substrate fee that can correspond to Daikichi Semiconductor.

Claims (1)

[Claims] (1) Cu powder with a final product ratio of 5 to 2 Uwt% and W powder or Mo powder or W-Mo alloy powder with an average particle size of 05 to 5 μ are mixed and molded, and then fired in a reducing atmosphere. semiconductor substrate materials.