JPS61251593A - Crucible for production of high-purity semiconductor single crystal - Google Patents

Abstract

PURPOSE:To provide the titled crucible free of leaching of impurities and resistant to peeling off of the coating layer even after repeated heating and cooling cycles, by coating the surface of graphite substrate with a thermally decomposed BN via an SiC film. CONSTITUTION:A graphite having excellent processability and available at a low cost is used as a substrate and is coated with an SiC film having high melting point and high corrosion resistance to molten semiconductor to obtain the core of a formed crucible. The surface of the core is coated with a thermally decomposed BN of usually about 0.01-1.0mm thick by CVD process to obtain the objective crucible. Since graphite coated with SiC layer is used as the base of the crucible, the peeling off of the coating layer can be prevented even after repeated heating and cooling cycles. A large-sized crucible having thin wall thickness can be produced because of high strength of the base, and the production cost of the crucible can be reduced. It is especially suitable as a crucible for the production of high-purity GaAs semiconductor for IC, e.g. VLSI.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a crucible coated with boron nitride, and more particularly to a crucible for producing high-purity semiconductor single crystals.

[Prior art]

In the semiconductor industry, it is important to first manufacture single crystals of high-purity silicon, germanium, gallium arsenide (GaAs), etc. in order to produce semiconductor products that receive quality awards.

In other words, it is important not only to prevent impurities from being mixed into the raw materials, but also to prevent damage to the equipment itself when manufacturing large-diameter single crystals by melting and pulling the obtained semiconductor material. It is necessary to prevent it from becoming an impurity and being mixed into the single crystal.

In the method of obtaining a single crystal from a molten semiconductor material by the pulling method, the crucible for melting should be made of a high-purity material that is not reactive with the semiconductor material, and various ceramics, precious metal materials, etc. can be used. ing. However, because these crucible materials contain various sintering agents and have some reactivity, they are difficult to manufacture when producing high-purity semiconductor single crystals, especially GaA3 semiconductor single crystals for VLSI. A serious problem is that the crucible material becomes an impurity and mixes into the single crystal. In addition, in the recent large semiconductor wafer manufacturing industry, large-capacity crucibles are required, so the amount of crucible material used has increased, and in order to safely accommodate the large-capacity contents! The strength of the pot material must also be increased.

By the way, boron nitride has excellent electrical insulation, thermal conductivity, and thermal shock resistance, as well as chemical stability at high temperatures, oxidation properties, and lubricity, so it is used in many fields. Although it has been widely praised, it is also being used as a suitable crucible for the production of semiconductors.

Methods for producing boron nitride include reducing nitridation of boron oxide with carbon in ammonia and a method of reacting boron halide and ammonia in a gas phase at high temperature (CVD method), but the latter method is based on a gas phase reaction. Then, pyrolytic boron nitride (P
BN) and is of high purity, it is particularly suitable for use in crucibles for semiconductor manufacturing.

However, manufacturing using the CVD method is not easy;
The cost of manufacturing large-scale products is enormous, and it is practically impossible.

Furthermore, crucibles for semiconductor manufacturing are made of quartz, graphite, silicon carbide, precious metals, etc.
Although crucibles that are suitable in terms of strength have been provided, there is a problem in that it is difficult to obtain high-quality semiconductor single crystals as a result of the crucible materials often being introduced into semiconductors as impurities when the contents are melted.

On the other hand, crucibles or boats for generating metal vapor for vapor deposition made of gutphite (graphite) coated with a thick film of PBN are known (for example,
Publication No. 192 - In this case, the PEN film is used as a protective film,
It serves to prevent the gutphite from being eroded by the molten metal for generating metal vapor, and at the same time to prevent the molten metal from being contaminated by impurities leached from the gutphite. However, when attempting to use this known crucible for the production of high-purity semiconductor single crystals, problems arise due to some gutphite inevitably being introduced as an impurity into the PBN coating layer, and the adhesion between gutphite and PBN. sex is very weak and P
The EN film has a thermal expansion coefficient of -2.9X in the direction parallel to the film layer.
10 /℃, which is a negative expansion, and the coefficient of thermal expansion of the gutphite substrate and the PBN thin film is significantly different, so heating -
There is a problem that when subjected to cooling psyche, a peeling phenomenon occurs immediately.

Therefore, in order to manufacture crucibles that can be used as practical products, it is necessary to use PB
The situation is such that N is deposited in a thick layer over a long period of time, and in fact the gutsphite substrate must also be coated in a thick layer.

[Purpose of the invention]

Therefore, the present invention was completed in order to solve the above problems, and its purpose is to provide a crucible for manufacturing high-purity semiconductor single crystals that is large in size, has sufficient strength, and is relatively low in cost. It is about providing.

[Means to solve the problem]

According to the present invention, there is provided a crucible for producing a high-purity semiconductor single crystal, characterized in that the surface of a crucible-shaped molded base made of graphite is coated with pyrolytic boron nitride through a silicon carbide film.

The mandrel of the crucible-shaped molded body base of the present invention is made of graphite, which is low cost and has excellent workability, as a base, and has a high melting point on this,
It is made by forming a silicon carbide film that has good corrosion resistance against molten semiconductors, and the surface of this metal core is coated with pyrolytic boron nitride (
PBN) (by 4D method, usually 0.01 to 1.0 m
coated to some degree.

According to the mandrel according to the present invention, the strength is greater than that using only graphite, the strength of the crucible is sufficient even if the wall thickness is made relatively thin, and the crucible can be made lightweight and large. can. The thermal conductivity of graphite is about 15Q W/mlc, which is about twice that of silicon carbide, which has excellent thermal conductivity, so it is especially useful for molten semiconductors in large crucibles. This has the effect of reaching a predetermined temperature evenly and quickly.

Further, according to the present invention, when a silicon carbide film is coated with PBN, a reaction layer is generated at the interface, so that the adhesion of the PEN film is significantly improved.

The present invention is particularly suitable as a y-crucible for manufacturing high-purity GaAs semiconductors used in ultra-LSI manufacturing processes, and there is no leaching of impurities from the crucible, and
It has the advantage that the PBN coating layer does not peel off due to heating/cooling cycles, has sufficient strength, and is inexpensive to manufacture.

In the present invention, it is important to interpose a silicon carbide film as described above, and this film may be formed by using the well-known CVD method, and the surface of the base made of graphite may be silicified by a vapor phase chemical reaction. A silicon carbide film can also be formed by applying.

〔Example〕

Next, examples of the present invention will be described.

(Example 1) A crucible-shaped molded body made of highly dense graphite and having a diameter of 2 cm, a height of 20 cm, and a wall thickness of 0.5 cm was prepared.

Next, this molded body was placed in a reaction chamber, and the molded body was heated for 12 hours.
The temperature was set at 00°C, and 5IH4 gas was introduced into the reaction chamber at a pressure of 3Q TOrr, and a silicification reaction was carried out for 1 hour. As a result, silicon carbide was formed on the entire surface of the graphite compact to a thickness of 1000 μm.

After that, the molded body (mandrel) was placed in a CVD reaction chamber at a temperature of 1300°C, and BCIs gas, NH3 gas, and H2 gas were supplied in the reaction chamber at 50CQ/m, respectively.
A pressure cuff, Q Torr, was introduced at a flow rate of 200 QQ/lin and 1000 QC/lin, and a contact reaction was carried out for 10 hours, leaving a thickness of 50 μm on the entire surface of the silicon carbide film.
PBN coating of sea bream was applied.

The obtained product of the present invention is made into a semiconductor GaAs by a pulling method.
As a result of using it as a single crystal manufacturing crucible, it was used 10 times (
Even after one heating-cooling cycle), the PBN coating film did not peel or crack, and no impurities were mixed into the GaA3 melt from the crucible, making it possible to produce a high-purity semiconductor GaAs single crystal of good quality. could be manufactured.

In addition, the crucible is not a simple one that exhibits good corrosion resistance due to the PBN coating film, and the core made of graphite coated with a silicon carbide film has excellent thermal conductivity, so the temperature of the entire crucible can be maintained uniformly at all times, and the sample in the crucible is uniformly dissolved, making it suitable for producing high-quality single crystals.

(Example 2) The graphite crucible shaped body used in Example 1 was placed in a CVD reaction chamber at a temperature of 1400°C, and CH45l-C
200 am
A silicon carbide film with a thickness of .

Then, in the same manner as in Example 1, 50 swt thick PB was applied to the entire surface.
N coating was applied.

The obtained product of the present invention is made into a semiconductor GaAs by a pulling method.
When used as a crucible for producing a single crystal, the PBN coating film did not peel or crack, and no impurities were mixed into the GaA3 melt from the crucible, resulting in a high purity semiconductor GaAs single crystal.

In addition, the temperature of the entire crucible can always be kept constant at -I/c, Ii, and the sample in the crucible is uniformly melted, which is suitable for producing high-quality single crystals.

〔Effect of the invention〕

The crucible of the present invention is suitable as a crucible for manufacturing high-purity semiconductor single crystals, and is particularly suitable as a crucible for manufacturing high-purity GaAS semiconductors used in ultra-LSI engineering C. Molecular beam epitaxy (MB) 1il is a method for creating group semiconductors and It-VI group semiconductors.
y), π, m, v in Kufster ion plating method (Eng CB), etc.

It can also be used as a spit to evaporate group (2) alloys.

Furthermore, according to the present invention, since graphite coated with a silicon carbide film is used for the substrate, there is no leaching of impurities from the crucible, and since the substrate and PBN have good adhesion, it can be easily removed even during heating and cooling cycles. The PBN coating layer does not peel off. And since the base is high strength, even if the wall thickness of the crucible is thinned, it can still be strong enough, lightweight, and large.In addition to using inexpensive graphite, the thickness of the PBN layer can be increased. Since there is no need to do this, there is an excellent advantage that manufacturing costs can be reduced.

Claims (1)

[Claims] A crucible for producing a high-purity semiconductor single crystal, characterized in that the surface of a crucible-shaped molded base made of graphite is coated with pyrolytic boron nitride via a silicon carbide film.