JPS63277590A - Boron nitride crucible - Google Patents

Abstract

PURPOSE:To prolong the working life of the crucible of multiple wall structure, by making it by the CVD process with reaction gases of stream rates over specific values and specifying the thicknesses of the first layer, second layer and the whole walls respectively. CONSTITUTION:The subject crucible is made by the CVD process in a reactor where reaction gases are allowed to flow over 50m/sec. The crucible is composed of alternative lamination with the first layer of 1-20mu thickness and the second layer with 1/50-1/2 thickness of the first layer and the total thickness of the wall is 0.5-3mm. In case of 50m/sec or less gas flow rate, the discrimination between individual layers becomes nuclear and layer peeling becomes difficult. When the first layer is less than 1mu thick, the working life becomes short, over 20mu cannot achieve satisfactory life-prolonging effect. When the second layer is thinner than the minimum limit, the layer-peeling behavior becomes wrong, while over upper-limit causes lamination with the first layer. Further, less than 0.5mm wall thickness induces unsatisfactory strength, over 3mm thickness increases internal stress to cause autogenous lamination.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention provides boron nitride crucibles with improved service life, particularly for metal and This invention relates to a boron nitride crucible for melting compounds.

[Conventional technology]

Pyrolytic boron nitride (PBN) is a high-purity, high-quality boron nitride (BN) that is used in a wide range of fields such as the production of compound semiconductors and special alloys. Especially Ga
AB Table In the production of compound semiconductors, PBN's excellent corrosion resistance and high purity are utilized to the maximum extent possible.
It is an essential material for growing compound semiconductor single crystals with few impurities and excellent electrical properties.

For example, in GaAs single crystal growth, PBN is
It is used as a crucible in the EC method and as a boat in the HB method (horizontal Grizzman method). In addition, Ga1-〇) on a GaAs single crystal wafer,
PBN is also almost exclusively used as a container for metal melting in the molecular beam epitaxy method, which is a method for growing mixed crystal compound semiconductors such as tzAa.

PBN As disclosed in U.S. Pat. No. 3,152,006, 811, boron trichloride (B
α3) Boron halide and ammonia are used as gaseous raw materials, and the temperature is 1,450°C to 2,300°C, the pressure is 5.
It is synthesized by so-called chemical vapor deposition (CCVD) in which BN is deposited on the surface of a suitable substrate under conditions of less than 0 torr. By appropriately selecting the substrate material and CVD conditions, the deposited PBN film can be separated from the substrate and a free-standing PBN article can be obtained.

The PBN obtained in this way has a structure in which the hexagonal BN OC planes are highly oriented in the direction perpendicular to the film growth direction, and therefore, when used repeatedly as a crucible in the LEC method, for example, Uneven layer peeling when removing boron oxide (B203) with an inhibitor
This has the disadvantage that it is easy to cause damage and therefore has a short lifespan, and it is difficult to guarantee that it will have a certain lifespan.

As a method to solve these drawbacks, a multi-walled crucible has been proposed, which is composed of a large number of individual walls with thicknesses in a specific range with an intervening intermediate wall (Japanese Patent Laid-Open No. 61
-285383).

In such a multi-wall structure crucible, for example, when removing B2O3 after crystal growth using the IJC method, exfoliation always occurs at the innermost wall layer of the crucible, and the partial exfoliation layer can be removed without deepening the exfoliation. It has the advantage that the lifespan of the crucible is significantly longer than that of conventional crucibles, and there is little variation in the lifespan between crucibles. Furthermore, in manufacturing such a multi-walled crucible, the molar ratio of ammonia to boron halide in the raw material gas is varied and film formation is repeated alternately, making it necessary to temporarily interrupt film formation. This method has the advantage that the crucible can be manufactured without requiring an unnecessarily long time.

In such a multi-walled crucible, the thinner the individual walls are, the longer the life will be.
According to the method described in Japanese Patent No. 285383, if the thickness of the first wall is less than 20 μm, the divisions between the individual walls become unclear, and the effect of the multi-wall structure as described above cannot be sufficiently obtained. There were many shortcomings.

[Problem that the invention seeks to solve]

As a result of various studies aimed at solving the above-mentioned drawbacks, the inventors of the present invention found that a crucible manufactured with a flow rate of raw material gas in the CVD reaction chamber of 50 m/s or more can be used even if the thickness of the first wall is less than 20 μm. We found that the division between the two was clear and completed the original BA.

[Means for solving problems]

That is, the present invention provides a boron nitride crucible manufactured by a chemical vapor deposition method with a flow rate of raw material gas in a reaction chamber of 50 m/s or more, and in which the thickness of one layer is 1 μm or more.
The first wall is less than 0 μm and the thickness of the first wall is less than 0 μm. −
1/2 of the second wall are laminated alternately with bonding to each other, and the total wall thickness is 0.5 to 3.
It is a boron nitride crucible with a multi-walled structure characterized by the shape of a dragon.

The present invention will be explained in more detail below.

In the multi-wall structure crucible of the present invention, the thickness of the first wall is 1 μm.
The range is less than 20 fine. If the thickness is less than 1 μm, the strength of the PBN film constituting the wall will be insufficient, resulting in a short life when used for single crystal growth.If the thickness is more than 20 μm, the structure will be the same as that of a conventional multi-walled crucible, resulting in a short life. The extension effect will not be sufficient. Next, the thickness of the second wall adjacent to the first wall is the thickness of the first wall. -It's a spoon. ification. If the thickness is thinner, the peelability of each layer will be poor, and the function as an intermediate wall will not be obtained sufficiently. Moreover, if it is thicker than a spoon, it is not preferable because it tends to cause lamination with the first wall. The overall wall thickness of the crucible is 0.5 to 6 mm. If the wall thickness is less than 0.5J11, the strength of the entire crucible will be insufficient, and if it exceeds 3 layers, internal stress will increase, resulting in spontaneous lamination, which is not preferable. The crucible of the present invention can have multiple walls approximately 10 to 100 times thicker than conventional crucibles because the thickness of each wall is thinner.

In the present invention, it is important that the flow rate of the raw material gas in the CVD reaction chamber when forming the individual walls is 50 m/s or more. When the flow rate is less than 50 m/s, the divisions between the individual walls become unclear, making it impossible to obtain a crucible with good layer-by-layer peelability. The reason why the separation between the walls becomes clearer by setting the flow velocity to 50 m/s or more is presumed to be that the source gas conditions can be changed quickly.

Next, the manufacturing method of the multi-wall structure crucible of the present invention will be explained. The individual walls forming the multi-wall structure PBN crucible are made of boron trichloride gas such as boron trichloride and ammonia gas as raw materials. It is formed by the CVD method, at a pressure of 5 torr' or less and a temperature of 1850℃.
'It is sufficient if it is 0 or more. When the pressure exceeds 5 torr f: fine particles of BN are generated as a by-product and are incorporated into the PBN film, which tends to impair the uniformity of the structure. temperature is 185
If the temperature is lower than 0°C, the strength of the PBN produced is low, and the strength for practical use as a crucible tends to be insufficient. In order to weakly bond the walls formed under these conditions to each other,
The first wall and the second wall (intermediate wall) adjacent thereto may be deposited at different molar ratios of ammonia to boron halide. That is, the molar ratio when forming the first wall is 2 to 10. The molar ratio of the second wall may be greater than or equal to 2 and less than 2.

In order to adjust the flow rate of the raw material gas in the CVD reaction chamber to 50 m/s or more, it is necessary to
This can be done by adjusting the cross-sectional area of the space between the walls of the p-reaction chamber, and the temperature and pressure of the C'VD reaction chamber.

Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

[Example Comparative example]

5c! ! L width x 60c IIl length x 1c * thickness graphite plate 8
A reaction chamber having an octagonal cross section was formed on the top surface of a graphite plate (bottom plate) with a diameter of 20α. In the center of the bottom plate, there was a hole with a diameter of 5 cm for gas introduction, and two graphite pipes (outside diameter 5 c!
L and 2.5cR) are connected coaxially, and the diameter is 5c from the top of the reaction chamber! A graphite substrate with rL1 length of 6 mm was suspended. The entire reaction chamber is placed in a high-temperature resistance heating vacuum furnace.
BCt3 is applied to the inner and outer tubes of the graphite pipe of the raw material gas introduction tube.
, Stainless steel gas piping was connected to supply NH3 gas. The vacuum furnace was heated to 1900'C while evacuating to 10''3 Torr.

Next, under a pressure of 1 torr, the first wall was deposited with a molar ratio of ammonia to boron trichloride of 4, and the second wall was deposited with a molar ratio of 1 as shown in the table, and the total wall thickness was 1. A related PBN crucible was prepared. Regarding the obtained crucible,
A lifespan test assuming single crystal growth by the LEC method was conducted using the following method.

That is, 50y of B2O3t- is placed in the crucible, and N2
It is heated to 1280° C. in a W atmosphere to melt B2O3, and then cooled to room temperature. B2O3 attached to the inner wall of the crucible is
The entire crucible is immersed in methanol and removed by ultrasonic cleaning for 20-40 minutes;
During the cooling contraction in step 3, a part of the inner wall surface of the PBN crucible adhering to B2O3 peels off. This was repeated until the crucible was damaged. The number of times until failure of each crucible is shown in the table.

From the table, it can be seen that all of the examples of the present invention have a lifespan of 40 times or more, and have a longer lifespan than the comparative examples.

〔Effect of the invention〕

The present invention's multi-walled boron crucible has MB
In the E method and the IJC method, the service life can be significantly extended, so the manufacturing cost of compound semiconductors can be reduced.

Claims (1)

[Claims] 1. A boron nitride crucible manufactured by chemical vapor deposition with a flow rate of raw material gas in the reaction chamber of 50 m/s or more, the first wall having a thickness of 1 μm or more and less than 20 μm, and the first wall having a thickness of 1 μm or more and less than 20 μm. The second wall, which is 1/50 to 1/2 of the first wall, is bonded to and alternately stacked, and the total wall thickness is 0.5 to 3 mm. A boron nitride crucible with a multi-walled structure.