JPS61236685A - Crucible for growing compound semiconductor - Google Patents

Abstract

PURPOSE:To provide the title crucible for preparing a compound semiconductor having long life and high quality wherein said crucible comprises a specified boron nitride prepd. by thermal cracking. CONSTITUTION:Boron nitride is formed by chemical vapor deposition from a gaseous mixture consisting of boron halide and ammonia at >=1,850 deg.C deposition temp. at >=400mum/hr vapor deposition velocity. Thus, a crucible for growing a compound semiconductor is obtd. from boron nitride having <=6.90Angstrom lattice constant of the C axis, >=20Angstrom size of crystalline in the direction of the C axis, >=2.1g/cm<3> density and <=50ppm content of Si.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pyrolytic boron nitride crucible for growing compound semiconductors.

[Conventional technology and its problems]

Pyrolytic boron nitride (hereinafter referred to as PBhJ) is a high-purity, high-quality boron nitride (BN) that is an industrial material used in a wide range of applications, including crucibles for manufacturing semiconductors and special alloys.

Various proposals have been made regarding PBN-made rutsuho and its manufacturing method. For example, as disclosed in US Pat. No. 3,152,006, a boron halide such as boron trichloride (BCl) and ammonia are used as gaseous raw materials at a temperature of 1450 to 2300°C and a pressure of less than I Torr to 50 BN on the surface of a suitable substrate under conditions of Torr.
It is obtained by a so-called chemical vapor deposition method (hereinafter referred to as CVD method), in which . By appropriately selecting the base material and CVD process conditions, the deposited PBN film can be separated from the base material to obtain a self-supporting P-BN article, such as a crucible.

PBN products have excellent corrosion resistance, thermal stability, and high purity, so they are used as crucibles for growing compound semiconductors, and are essential for growing compound semiconductor single crystals with low impurities and excellent electrical properties. It is the material of

However, since PBN is produced by the CVD method as mentioned above, the C plane of the crystal f foi is parallel to the base material surface.
1-7) has a layered structure oriented in a Goryeo layer. Therefore, when used repeatedly as a crucible, there are problems in that layers tend to peel off, the lifespan is short, and it is difficult to obtain a product with a constant lifespan. There is also the problem that metal impurities contained in the PBN crucible get mixed into the PBN crucible during growth of the compound semiconductor, significantly degrading its electrical properties.

As a result of various studies conducted by the present inventors in order to solve the problems of the PBW crucible, we found that there is a close relationship between the failure of the PBW crucible, the quality of the compound semiconductor grown from it, and the physical properties of the PBW crucible. We have found that by controlling the physical properties within a specific range, the life of the crucible can be extended and stabilized, and the quality of the compound semiconductor grown can be improved. Among the physical properties, important factors include, for example, the following.

(1) C-axis lattice constant (co) of the BN crystal (hexagonal crystal) constituting the crucible (2) Size in the C-axis direction of the BN crystallite constituting the crucible Lc 1 (3) Density of the crucible (4) The silicon concentration (1) contained in the crucible is B
It represents the degree of N crystallinity, and as this value decreases, that is, as it approaches the theoretical value, it indicates that crystallization progresses. (2) represents the size of the crystal, and a large value indicates that the crystal is growing.

(3) is considered to be a measure of not only the size of the BN crystal lattice but also the way in which it is stacked, and the larger this value is, the more highly crystallized the crystals are stacked up.

[Means for solving problems]

The present invention provides a PBN rutsuho obtained by chemical vapor deposition using boron halide and ammonia as raw materials, in which the lattice constant of the C axis of the PBN is 6.90 angstroms or less, and the size of crystallites in the C axis direction. is 20 angstroms or more, and its density is 2.1 El/
This is a PBN rutsuho for compound semiconductor growth, which is made of a material having a cd or more and a silicon content of 50 ppm or less.

The present invention will be further explained in detail below.

In the crucible for growing compound semiconductors, the P that makes up the crucible
BN with a C-axis lattice constant of more than 6.90 angstroms, a crystallite size in the C-axis direction of less than 20 angstroms, and a crucible density of 2.1F.
If it is less than /d, the mechanical properties and thermal shock resistance are significantly lowered, and when used repeatedly as a crucible, the layers tend to peel off, resulting in a significantly short life span of the crucible. The reason for this is thought to be that the microstructure of PBN is affected by undeveloped BN crystals (1-), extremely small crystals, or crystals that are not stacked closely.

The specific CVD conditions to obtain N like this are:
Deposition temperature: 1850°C or higher; deposition rate: f: 400 μm/h
It is preferable to make it below r.

In addition, when growing compound semiconductor single crystals such as QaAs, the silicon content in the crucible is 50 ppp.
If a material exceeding m is used, its specific resistance will be 1 x 107Ω.
It is less than m, which is not preferable.

The reason why we focused on silicon as an impurity that can be included in the crucible is that when making the crucible, the boiling point of boron trichloride used is close to the boiling point of silicon chloride, so silicon chloride, which cannot be separated by distillation, is It is often contained in large amounts in boron chloride, and as a result, PBN crucibles tend to contain particularly large amounts of silicon among metal impurities. PBN crucible silicon te50 ppm
In order to achieve the following, it is preferable to use boron trichloride with an ash content of 99.91 or more (silicon concentration of 50 ppm or less) as a raw material, and graphite with an ash content of 0.1 or less by weight as a base material.

The physical properties of PBH can be easily changed by the method shown below. That is, by increasing the CVD conditions when producing PBN, such as increasing the precipitation temperature, it is possible to decrease the lattice constant co of the C axis and increase the size and density of crystallites. When the number of raw materials supplied per sweet time is increased, that is, when the deposition rate is increased, the lattice constant Co of the C axis increases, the crystallite size Lc decreases, and the density tends to decrease.

Naturally, the amount of impurities in PBN is closely related to the purity of the raw material gas and the purity of the base material, and can be easily changed by changing these purities.

Examples of CVD conditions for efficiently obtaining a PBN crucible according to the present invention include a deposition temperature of 1900°C or higher, and a deposition rate of 3.
00μm/hr or less, and purity 9 as raw material.
Examples include using boron trichloride with a concentration of 9.91 or more (811 m% degree, 50 ppm or less) and graphite with an ash content of 0.1 or less by weight as a base material.

Example 10 Using six graphite plates of T-In width x 60 m length x 1 cm thickness, a hexagonal reaction chamber was formed on the top surface of the graphite plate (bottom plate) with a diameter of 30 m. A hole is made in the center of the bottom plate for gas introduction, and a graphite tube 2 coated with PBN in advance is used as the raw material gas introduction tube.
I connected the books so that they were coaxial. A crucible-shaped graphite base material with a diameter of 96 m+ and a length of 100 sardines was suspended from the upper end of the hexagonal body, and the entire reaction chamber was placed in a resistance heating vacuum furnace (F was charged. The furnace was evacuated to 1 O-" Torr [ After 7
Heated to precipitation temperature. Under a pressure of 0.75 Torr, boron trichloride and ammonia diluted with nitrogen gas were introduced, and after vapor deposition for a predetermined period of time, it was cooled, and the generated PBN was removed to obtain a PBN crucible with a wall thickness of 1 m.

Three types of PBN rutsuho were produced. For the three types of crucibles prepared, the lattice constant (co) of the C axis of PBN and the size of crystallites in the C axis direction (Lc) were determined by X-ray diffraction, the density fa) was determined by Archimedes method, and the density fa) was determined by emission spectrometry. The silicon content in the crucible was measured.

Furthermore, the inner surface of each crucible prepared under the same conditions was
After polishing the crucible by about 50 μm with emery paper, the crucible was washed with ethanol and dried. With these crucibles, each Ga
The As single crystal was grown repeatedly by the liquid sealing 1F Czochralski method using B and 0° as the sealing agent 11-1 until the melt was broken. The number of times the crucible was grown before it was damaged, and the GaAs grown when using each crucible.
The average resistivity values of single crystals are shown in the table.

The experiment shown in Example 7 was conducted three times using the same procedure, but the obtained results were the same.

Table: The PBN crucible according to the present invention has a long life of more than 20 times.
It is clear that the specific resistance value of the GaA1+ single crystal grown from such a crucible is also moderately insulating, with a resistivity value of 2xlO'Ωm or more.

〔Effect of the invention〕

Simultaneously satisfies the physical properties of the four factors shown in the present invention (9)
In the PBN crucible, crystallization progresses, the crystallites are large, they are stacked closely together, and there are very few metal impurities contained therein. Therefore, if the PBN crucible of the present invention is used when growing a compound semiconductor, it will not cause layer delamination, will have a long life, and will be stable, and will be excellent because there will be less impurities mixed in from the crucible. The advantage is that compound semiconductors with electrical properties can be grown.

Claims (1)

[Claims] In a pyrolytic boron nitride crucible for compound semiconductor growth obtained by chemical vapor deposition using boron halide and ammonia as raw materials, the pyrolytic boron nitride has a C-axis lattice constant of 6.90 angstroms or less in the C-axis direction. A pyrolytic boron nitride crucible for growing compound semiconductors, the crucible having a crystallite size of 20 angstroms or more, a density of 2.1 g/cm^3 or more, and a silicon content of 50 ppm or less.