JPS61219787A - Crucible for producing single crystal for high-purity semiconductor - Google Patents

Abstract

PURPOSE:To obtain the titled crucible which is large-sized and excellent in the strength without the leaching of the impurities by coating the surface of a crucible-shaped molded base material consisting of a specified nonoxide ceramic or a metallic material having high m.p. with the thermally decomposable boron nitride. CONSTITUTION:The thermally decomposable boron nitride is coated on the surface of a crucible-shaped molded body consisting of one or more kinds of nonoxide ceramics selected from among SiC, Si3N4, TiN and AlN, or one or more kinds of metallic materials having high m.p. selected from among Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W in about 0.01-1.0mm thickness by a CVD method.

Description

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

(Conventional technology and problems) In the semiconductor industry, when creating high-quality semiconductor products, the first step is to use high-purity silicon, dermanium, and arsenide.
It is important to produce single crystals such as GaAs.

In order to do this, it is necessary not only to prevent impurities from entering the raw materials, but also to prevent impurities from being introduced due to damage to the equipment itself when melting the obtained semiconductor material and manufacturing large-diameter single crystals by the pulling method. It is necessary to prevent this from becoming 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, it is difficult to manufacture high-purity semiconductor single crystals, especially GaAs semiconductor single crystals for fiLsI. A serious problem is that the crucible material becomes an impurity and mixes into the single crystal. In addition, the current large semiconductor wafer manufacturing industry requires large-capacity crucibles, which increases the amount of crucible material used, and also requires the strength of the crucible material to safely accommodate large-volume contents. Must be raised.

By the way, boron nitride has excellent electrical insulation, thermal conductivity, and thermal shock resistance, as well as chemical stability at high temperatures, oxidation resistance, and lubricity, so it has been used in many fields and has received awards. However, it is now being used as a suitable crucible for manufacturing the semiconductors.

There are several methods for producing boron nitride, such as reducing and nitriding boron oxide with carbon in ammonia, and reacting boron halide and ammonia in the vapor phase at high temperatures (CVD method). Pyrolytic boron nitride (P B N ) is obtained by the method, and it is highly pure.
It is particularly suitable for crucibles used in semiconductor manufacturing.

However, manufacturing using the CVD method is not easy, and manufacturing large-sized products requires enormous costs and is practically impossible.

Furthermore, crucibles for semiconductor manufacturing are made of quartz, graphite, silicon carbide, metal, etc., and the size and
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, metal vapor generation crucibles or boats for vapor deposition made of graphite coated with a thin film of PBN are known (for example, Japanese Patent Publication No. 59-19
No. 192), in this case the PBN thin film is used as an I-retaining film,
It serves to prevent the graphite from being attacked 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 graphite. However, high purity semiconductor single crystal! ! Crucible for Horse Making If you try to use this known crucible, there will be a problem that some graphite will inevitably be introduced into the PBN coating layer as an impurity, and the adhesion between graphite and PBN will be very poor. PBNIllJ has a thermal expansion coefficient of -2 in the direction parallel to the film layer.
, 9X10-8/''C, which is a negative expansion, and the thermal expansion coefficients of the graphite substrate and the PBN thin film are greatly different. Therefore, there is a problem that peeling occurs immediately when subjected to a heating-cooling cycle.

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 thickly over a long period of time, and in fact needs to be coated in a thicker layer than the graphite substrate.

(Means for Solving the Problem) In order to solve the above-mentioned problems, the present inventors, as a result of intensive research, have provided a crucible for manufacturing high-purity semiconductor single crystals that is large in size and has sufficient strength. It became possible.

That is, the present invention uses one or more non-oxide ceramics selected from silicon carbide, silicon nitride, titanium nitride, and aluminum nitride, or Ti, Zr%Hf, V, and Nb.

A crucible for producing a high-purity semiconductor single crystal, characterized in that the surface of a crucible-shaped molded body made of one or more high-melting point metal materials selected from T aSCr%Mo and W is coated with pyrolytic boron nitride. be.

In the present invention, non-oxide ceramic materials such as silicon carbide, silicon nitride, titanium nitride, and aluminum nitride, which have a high melting point and good corrosion resistance against molten semiconductors, as well as Ti, Zr, and HfCWa are used as the base of the crucible-shaped molded body. family)
, V t N b * T a (V a group), Cr
s M o *W (Vla group) metals are employed, and pyrolytic boron nitride (P B N ) is deposited on the surface of these substrates by the CVD method, usually in a concentration of 0.01 to 1. It is coated to the extent of On++a.

These base materials have high strength unlike graphite,
Even if the wall thickness is reduced, the strength of the crucible is sufficient, and the crucible can be made lightweight and large.

In particular, among the non-oxide ceramics for the base, silicon carbide is recommended as the most suitable material because it has very good adhesion to PBN and also has excellent thermal conductivity.

The present invention is particularly suitable as a crucible for manufacturing high-purity GaAs semiconductors used in ultra-LSI ICs, etc., and there is no leaching of impurities from the crucible, and the PBN coating layer is formed by heating and cooling cycles. It has the advantages of no peeling, sufficient strength, and low manufacturing cost.

(Examples) Example 1: A silicon carbide crucible-shaped molded body base having a diameter of 20 am, a height of 20 c++1, and a wall thickness of 11 a was prepared by immersion molding, drying, and firing.

The molded body substrate is placed in a furnace and heated to bring the temperature of the substrate to 1.
The temperature was set at 200° C., and B C1,, N H, were placed in the furnace.

Introducing a reaction gas consisting of H2 at a pressure of 20 Torr,
A contact reaction was carried out for 5 hours, and a pyrolytic boron nitride (P B N ) coating with a thickness of 0.1 ml was applied to the entire surface of the substrate.

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), no peeling or cracking occurred in the PBN coating film, and no impurities were mixed into the GaAs melt from the crucible, resulting in a high-purity semiconductor GaAs single crystal of good quality. si! I was able to build it.

In addition, this crucible not only exhibits good corrosion resistance due to the PBN coating film, but also because silicon carbide has excellent thermal conductivity, the temperature of the entire crucible can be maintained uniformly at all times, and therefore the inside of the crucible This sample is suitable for producing high-quality single crystals because it is uniformly dissolved.

Example 2: A diameter of 20 cm obtained by casting, drying, and firing.
A silicon nitride crucible-shaped molded body base having a height of 20 cm and a wall thickness of 1111 [+1] was prepared.

The molded body substrate is placed in a furnace and heated to bring the temperature of the substrate to 1.
The temperature was set at 200°C, and B, N, and H6 (borazole) were introduced into the furnace as reaction gases at a pressure of 20 Torr.
Over time, PB with a thickness of 0°11 was applied to the entire surface of the substrate.
N coating was applied uniformly.

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

This crucible not only exhibits good corrosion resistance due to the PBN coating film, but also silicon nitride has extremely high strength and excellent thermal shock resistance, so the crucible can be made large and can be heated. - Since it is resistant to cooling cycles, it is preferred as a large-diameter, high-quality crucible for producing single crystals.

(Effects 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 VLSI ICs, etc. Since graphite is not used in the process, there is no impurity leaching from the crucible, and since the substrate and PBN have good adhesion, even during heating and cooling cycles, PB
The N coating layer will not peel off. Since the base has high strength, even if the wall thickness of the crucible is made thinner, it can still be strong, lightweight, and large.
Since the N layer does not need to be a thick layer, the manufacturing cost is low, which is an excellent advantage.

Claims (1)

[Claims] One or more non-oxide ceramics selected from silicon carbide, silicon nitride, titanium nitride and aluminum nitride or T
i, Zr, Hf, V, Nb, Ta, Cr, Mo, W. A crucible for producing high-purity semiconductor single crystals.