JP3247838B2 - Pyrolytic boron nitride crucible and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pyrolytic boron nitride crucible used for a molecular beam source crucible of a molecular beam epitaxy apparatus and a method for producing the same.

[0002]

2. Description of the Related Art In a molecular beam epitaxy method (hereinafter abbreviated as MBE method), a thin film growth chamber is set to an ultra-high vacuum of 10 ^-6 to 10 ^-11 Torr, and a small amount of a desired metal is charged into a molecular beam source crucible. This is attached to a molecular beam generator called K-cell,
An epitaxy film is formed by heating a crucible to 1000 to 1500 ° C and applying a molecular beam generated from the molten metal to a heated substrate, making it possible to produce a thin film controlled to several atomic layers. . This is widely used especially for manufacturing an epitaxial film of a compound semiconductor such as GaAs.
As the molecular beam source crucible, a pyrolytic boron nitride (hereinafter abbreviated as PBN) crucible manufactured by a chemical vapor deposition (hereinafter abbreviated as CVD) reaction in terms of purity, heat resistance, strength, and the like. Used. This crucible is usually cylindrical with a horizontal lip and is about 1 mm thick.

[0003]

However, the PBN crucible manufactured by the conventional CVD reaction of ammonia (NH ₃ ) and boron trichloride (BCl ₃ ) has a large infrared transmittance.
When used as a molecular beam source crucible, it can be heated uniformly to a certain level of the melt of the crucible, but there is a problem that the temperature near the opening where there is no melt is lowered because infrared rays are transmitted. . As a method of improving this, a PBN crucible coated with graphite or carbon has been disclosed (see Japanese Utility Model Application Laid-Open No. 63-199172), but the number of manufacturing steps increases, the cost increases, and there is a risk of contamination of impurities such as carbon. There are problems. Therefore, it can be heated uniformly over the entire crucible, and is low in cost for molecular beam sources.
Supply of BN crucibles is desired.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and is directed to a PBN crucible used for a molecular beam source crucible of an MBE apparatus, which is supplied into a CVD reactor.
Molar ratio between ammonia and boron trichloride (NH ₃ / BCl ₃ )
Is formed in the range of 0.2 to 1.0, the wave number of 3700 to 6500
Infrared transmittance in the range of cm ^-1 is 1.0% or less (including 0%)
It is intended to subject matter that is, molecules of the crucible
When used for the molecular beam source of the X-ray epitaxy device, uniform heating can be achieved over the entire crucible, and a drop in temperature near the crucible opening generates droplets such as Ga, causing crystal defects in the GaAs thin film. Can be prevented. Also this P
The manufacturing method of BN crucible is as follows: NH ₃ and BCl ₃ are put in a CVD reactor.
The molar ratio (NH ₃ / BCl ₃ ) is supplied in the range of 0.2 to 1.0,
Pyrolytic boron nitride is deposited on the thermal core metal, cooled, and
The purpose is to extract the sediment from the material.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The temperature in the process of producing an epitaxy film of a group III-V compound semiconductor single crystal is usually about 800 to 1600 ° C., and the maximum energy heat transfer wavelength λmax.
λmax. · T = 2,898 (μm · K) (T: absolute temperature) (1) Since it is expressed by the equation (1), the wave number of 3,700 to 6,500 cm
A range of ^-1 is obtained. Therefore, if a PBN crucible with low infrared transmittance in this wavelength range is used, the transmittance of infrared light from the crucible in the epitaxy film manufacturing process will be significantly reduced, and the heating of the melt by the radiant heat within the crucible will be difficult. Since it is performed uniformly, crystal defects of the obtained epitaxy film are extremely reduced. The infrared transmittance in the range of the wave number of 3,700 to 6,500 cm ^-1 should not exceed 1.0% (including 0%) because uniform heating cannot be obtained if it exceeds 1.0%. Is preferably 0.2% or less.

[0006] If the thickness of the crucible is too small, there is a problem that the strength is reduced and the crucible is not practical. If the thickness is too large, infrared transmittance is reduced but layer separation easily occurs.
2.02.0 mm, preferably 0.8-1.5 mm. The shape and dimensions of the crucible may be known ones.

[0007] Regarding the optical characteristics of boron nitride (BN), the band gap (Eg) is 5.8 eV (see Research Report No. 27 of the Research Institute for Inorganic Materials, No. 27, p. 26). 1,380 cm ^-1 and 810 cm ^-1 [DNBose, HKHe
53, p.281 (1970)], it is assumed that PBN has absorption in the range of 3,700 to 6,500 cm ^-1 due to the mixture of turbostratic crystals with disordered crystals. It is considered. We have a wave number of 3,700-6,50
It has been found that the infrared transmittance of PBN at 0 cm ^-1 depends on the production conditions of PBN.

In other words, the present inventors focused on the molar ratio of NH ₃ to BCl ₃ (NH ₃ / BCl ₃ ) of the raw material gas in the crucible manufacturing process by the CVD method in order to reduce the infrared transmittance of the crucible, It has been found that a PBN crucible having a wave number of 3,700 to 6,500 cm ^{-1 and} an infrared transmittance as low as 1% or less can be obtained as a result of making the molar ratio significantly smaller than the practiced molar ratio of 2 to 5. If the molar ratio between NH ₃ and BCl ₃ is less than 0.1, P
The strength of the BN film decreases, and if it exceeds 2.0, the infrared transmittance will decrease.
Since it exceeds 1.0%, it is necessary to set it to 0.1 to 2.0, and preferably 0.2 to 1.0. At this time, the appearance of the crucible changed from yellow-brown to black-brown as the molar ratio became smaller from 2.0 to 0.2. In the method of manufacturing a PBN crucible according to the present invention, a heat-resistant core having a predetermined shape and dimensions is prepared, and
Installed in a CVD reactor, the pressure is 0.01 to 0.1 Torr, the reaction temperature is 1650 to 2000 ° C., and the NH ₃ gas and BCl ₃ gas have a molar ratio (NH ₃ / BCl ₃ ) of 0.1 to 2.0 , preferably 0.2 to 1.0. The reactor is maintained at a reaction pressure of 0.5 to 10 Torr, PBN is deposited on the core until a predetermined thickness is reached, and after the reaction is completed, the laminate is cooled and the laminate is taken out from the core, and Manufacture crucibles.

When this crucible is incorporated into an MBE apparatus and used as a molecular beam source crucible for Ga, uniform heating of the crucible becomes possible, and generation of crystal defects in the thin film due to scattering of Ga droplets can be prevented. It is possible to manufacture a simple device.

[0010]

[Example] Example 1 A graphite core metal having an outer diameter of 30 mm and a length of 150 mm was placed in a CVD furnace, the pressure was reduced to 0.1 torr or less, the temperature was raised to 1900 ° C, and NH ₃
And the molar ratio of BCl ₃ to 0.5, NH ₃ gas 0.5 liter /
Then, 1 liter / min of BCl ₃ gas was supplied, and 1 mm of PBN was deposited on the graphite core metal while reducing the pressure so as to maintain the inside of the furnace at 2 Torr. After the reaction was completed and cooled, the PBN deposit was extracted from the core metal to produce a PBN crucible having an outer diameter of 32 mm, a length of 105 mm, and a thickness of 1 mm.

Examples 2 to 5 The molar ratio of NH ₃ to BCl ₃ was changed to 0.1 (Example 2), 0.2 (Example 3), 1.0 (Example 4), 2.0 (Example 5) and
_A PBN crucible was manufactured under the same conditions as in Example 1 except that ₃ gas and BCl ₃ gas were supplied.

Comparative Example The molar ratio of NH ₃ to BCl ₃ was 3.0, and 3 liters of NH ₃ gas /
A PBN crucible was manufactured under the same conditions as in Example 1 except that the supply was performed while supplying 1 liter / minute of BCl ₃ gas.

The infrared transmittance of these crucibles at a wave number of 4000 cm ^-1 and the MBE device (model number MBE32F manufactured by Riber)
The temperature difference Δt between the bottom of the crucible and the opening when the metal material Ga was heated to 1000 ° C. and the number of crystal defects formed on the GaAs thin film were evaluated. The results shown in Table 1 were obtained. Obtained. In the evaluation of defects in the table, the number of crystal defects is indicated by ○: less than 10 / cm ² and Δ: 200 / cm ² or more. The infrared transmittance was determined by the following equation (2) at a wave number of 4000 cm ^-1 . Transmittance = (I / I ₀ ) × 100 (2) (where, I ₀ : intensity of light before transmission, I: intensity of light after transmission)

[0014]

[Table 1]

[0015] As shown in Table 1, it was found that P
It was found that the BN crucible can be heated more evenly and crystal defects on the GaAs film can be prevented.

[0016]

According to the present invention, a PBN crucible having a small amount of impurities and a low infrared transmittance can be obtained at low cost, and when this crucible is used for a molecular beam source cell of an MBE apparatus , the entire crucible can be obtained.
, An epitaxy film with few crystal defects can be obtained, and a good device can be manufactured.

Continuation of front page (72) Inventor Noboru Kimura 2-13-1 Isobe, Annaka-shi, Gunma Shin-Etsu Chemical Co., Ltd. Precision Functional Materials Laboratory (56) References JP-A-61-285383 (JP, A) JP-A-3-56674 (JP, A) JP-A-8-34684 (JP, A) JP-A-2-204391 (JP, A) JP-A-4-231459 (JP, A) JP-A-63-277590 (JP, A) JP-A 63-199172 (JP, U) JP-A 3-22067 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) C30B 1/00-35 / 00 H01L 21/203

Claims (3)

(57) [Claims] An ammonia supplied into a CVD reactor and
The molar ratio of boron trichloride (NH ₃ / BCl ₃ ) is in the range of 0.2 to 1.0.
A pyrolytic boron nitride crucible formed as an enclosure, having an infrared transmittance of 1.0% or less (including 0%) in a wave number range of 3700 to 6500 cm ^-1 . 2. The pyrolytic boron nitride crucible according to claim 1, wherein said crucible is a molecular beam source crucible used in a molecular beam epitaxy apparatus. Wherein the molar ratio of ammonia and three boron chloride containing the CVD reaction furnace (NH ₃ / BCl ₃₎ was supplied in the range of 0.2 to 1.0
Deposit pyrolytic boron nitride on the heat-resistant core metal and cool
A method for producing a pyrolytic boron nitride crucible, wherein the deposit is subsequently extracted from the cored bar .