JPS61236683A - Crucible for pulling single crystal - Google Patents

Abstract

PURPOSE:To obtain the title crucible having long life comprising a self-supporting crucible formed of boron nitride prepd. by the thermal cracking having a specified roughness of the internal surface and a specified radius of curvature at the corner of the bottom surface. CONSTITUTION:A mold having a specified shape and made of a highly pure material (e.g. graphite) having high heat resistance and high corrosion resistance with surface roughness Rmax<=500mum is disposed in a resistance heating vacuum furnace. Gaseous mixture obtd. by mixing boron halide with ammonia in 1:1-4 molar ratio is fed to the mold. The born halide is decomposed thermally at 1,850-2,100 deg.C under <=50Torr. Thus, a self-supporting crucible 1 having 0.5-5mm thickness, >=15mm radius of curvature (R) at the corner of the bottom surface, and 5-350mum internal surface roughness (Rmax) is obtd.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a crucible for pulling single crystals, particularly a self-supporting crucible made of pyrolytic boron nitride (hereinafter referred to as PBN). This invention relates to a rutsuho for pulling compound semiconductor single crystals (hereinafter referred to as single crystals for compound semiconductors).

(Prior Art and Problems) PBN crucibles have been conventionally used for pulling compound semiconductor single crystals.

The crucible conventionally used in this field is, for example, a free-standing type with a diameter of 4 ψ (approximately 100 ψ) and a thickness of about 1 snow. However, when this stiff PBN crucible is used to pull a compound semiconductor single crystal, the PBN in the crucible
The layers peel off, and the number of times the noodles can be used repeatedly is limited to about 10 times. Normally, a compound semiconductor single crystal is produced by putting a compound semiconductor single crystal raw material into a resistance heating vacuum furnace, and furthermore, the surface thereof is B, 0. It is produced by heating the crystal at high temperatures while coating it with silica to pull the single crystal. The inventor conducted various studies to improve the number of times PBN crucibles can be used, and found that the inner surface roughness (Rmax) of the PBN crucible and the radius of curvature (R) of the bottom corner
The present invention was arrived at based on the knowledge that this affects the lifespan of PBN rutsuho.

(Means for Solving the Problems) The present invention is a self-supporting Ruho made of PBN,
Moreover, the inner surface roughness (Rmax) of the crucible is 5 to 350 μm1, and the radius of curvature (R
This is a crucible t-f for pulling compound semiconductor single crystals of II=Vl group and ■-■ group elements where 1 is 15■ or more.

The present invention will be further explained in detail below.

To manufacture the product of the present invention, a mold made of a heat-resistant and corrosion-resistant high-purity material such as graphite having a desired shape is placed in a resistance heating vacuum furnace. Note that the surface roughness of the mold Rrnax <,
500 tlm (according to JIS B, O+601) is used. The reason for this is that a deposited film of PBN is easily formed. Next, a mixed gas of boron halide such as boron trichloride and ammonia in a 70 molar ratio of about 1:1 to 4, respectively, is supplied to the above-mentioned furnace, and the mixture is heated at a temperature of 1850 to 2100°C and a pressure of 50 Torr or less. The film is processed to a desired thickness, for example, 0.5 to 5 cm.

In addition, in the present invention, the radius of curvature of the bottom corner of the crucible (
R) should be 15w or more, but since it is also related to the diameter of the crucible, it is desirable that the diameter is 100- or more and the radius of curvature of the bottom corner of the crucible is 1/3 or less of the diameter.

By using a mold with such a structure, the stress at the corner part of PBN is alleviated, and the concentration of stress in B2O3 is also reduced when removing B2O3 after use, and the PBN
The number of times of use is more than twice that of conventional products with a radius of curvature of the bottom corner (R1 of 2 to 10 m).Next, the furnace is cooled and the graphite mold is taken out of the furnace.
When the N-deposited film is removed from the graphite mold, a PBN crucible is obtained.

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is an explanatory sectional view of a PBN crucible as an example of the present invention, and FIG. 2 is an explanatory sectional view of a PBN crucible as a comparative example.

The fraction 1 indicates the crucible, 2 indicates the bottom corner, and 3 indicates the wall thickness.

First, as shown in FIG. 1, the product of the present invention is composed of a PBN crucible 1, the bottom corner portion 2 of which has a radius of curvature of 201 RM or more, a wall thickness 3 of 1 mm, and an inner surface roughness of Rmax 200 μm.

On the other hand, the radius of curvature of the bottom corner part 2 of the commercially available comparative product is about 2 to 10+ m, and the inner surface roughness R
The maximum thickness is approximately 50 μm.

PBN Rutsut like the above! Assuming GaA single crystal growth by the liquid-phase sealed Czochralski method using
Above, the comparison product was used about 10 times.

(Embodiments of the invention) Example 1 A hexagonal reaction chamber was formed on the top surface of the graphite plate (bottom plate) with a diameter of 30 cm using six graphite plates of 1 ocrn width x 60 ctn length x 16n thickness. A hole for gas introduction was made in the center of the bottom plate, and two graphite tubes coated with PBN in advance were coaxially connected as raw material gas introduction tubes. A #Y-shaped graphite substrate with a radius of curvature of 20 mm at the bottom corner with a diameter of 96 mm and a length of 110 mm is suspended from the upper end of the hexagonal body, and the entire reaction chamber is charged into a resistance heating type vacuum furnace. 17. 1 furnace
(After exhausting to 1" Torr, it was heated to a temperature of 1875°C. At that time, the temperature of the raw material gas introduction pipe was 200°C at the reactor inlet and 1850°C at the graphite reaction chamber inlet.
．． Under a pressure of 5 Torr, boron trichloride and ammonia diluted with nitrogen gas were introduced, and after being vapor-deposited for a predetermined period of time, it was cooled, and the generated PBN was removed from the graphite base material, and a PBN with a thickness of 1 m was formed.

I got a pot. The inner surface of this rutsuho was polished with ≠500 sandpaper to give an Rmax of 50 μm.

For comparison, a crucible prepared in the same manner as in Example 1 was prepared.40. When polished with sandpaper, Rmax
A sample with a thickness of 370 μm was obtained.

Using these crucibles, a life test was conducted assuming GaAa single crystal growth using the LEC method.

That is, 200 g of B, O,'i was melted in a fulgon atmosphere at a temperature of 13,000 degrees Celsius in a crucible, and cooled in a room tm "t. Since B and 03 were stuck to the inner wall of the crucible, the whole was placed in methanol. and apply ultrasound to B, 0. and P.
Methanol was permeated into the BN adhesion interface to separate most of the adhering parts and remove the remaining B, 03 lumps.

This cycle was repeated, and the state of wear and tear on the crucible was checked each time. The results are shown in the table. (Experiments 1 and 2 are examples, and Experiment Na3 is a comparative example.) Table Example 2 Used 1.7 Except for using sandpaper of #1500 and having a surface roughness of nmaxl and 0 μm.

[Brief explanation of drawings]

The drawings are cross-sectional views for explaining PBN Rutsuho, and FIG. 1 shows an example, and FIG. 2 shows a comparative example. No. 0 1...Rutsu/hill, 2...Bottom corner part, 3.
・Wall thickness, 4... Solidification B, 08° Patent applicant Denki Kagaku Kogyo Co., Ltd.'$1 Figure 2

Claims (1)

[Claims] A free-standing crucible made of pyrolytic boron nitride, and furthermore, the crucible has an inner surface roughness (Rmax) of 5.
~350 μm, and the radius of curvature (R) of the bottom corner
A crucible for pulling compound semiconductor single crystals having a diameter of 15 mm or more.