JPS61236672A - Pyrolytic boron nitride coated products and manufacture - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to pyrolytic boron nitride (hereinafter referred to as PBN).
Punched products, especially PBN-covered products in which carbon is used as the base material and the PBN-covered skin is tightly sealed, and valley packaging for growing single crystals of compound conductors such as GaAS and InP during the manufacturing process thereof. Regarding Jikyo and its manufacturing.

[Conventional technology and points of interest]

PBN is a high purity boron distillate (BN) from Takashinaga.
It is a wide material used in crucibles for manufacturing semiconductors and special alloys.

For example, the liquid stabilization method (hereinafter referred to as LEC) is a method for growing compound crystals such as GaAs.
In addition to being used in the current industry, free-standing PBN rubber is currently used in the industry, especially when growing semi-insulating commercial compound single crystals for IC substrates. When carbon is mixed into the crystal, the impurity carbon forms an impurity level and deteriorates the electrical properties of the crystal. Therefore, it is necessary to apply PBN coating to the optical surface of each carbon member used in a single crystal refining furnace. Attempts have been made to prevent the incorporation of carbon into grown crystals.

Freestanding PBN and PBN covered AI? One product, as disclosed in U.S. Pat. No. 3,152.006, for example, uses a boron halide such as boron trichloride (B (2 g)) and ammonia as gaseous raw materials and is heated at a temperature of 14
Manufactured by the so-called chemical vapor deposition method (hereinafter referred to as CVD method) in which BN is deposited on the surface of an appropriate base material such as carbon under conditions of 50 to 2300 ° C. and a pressure of 5 Q Torr with no drops. However, if the base material is removed, a self-supporting PBN layered product can be obtained, and if the base material is left as is, a PBN coated article can be obtained.
N If the coated article is used under conditions in which heating and cooling are repeated in a single crystal gasification furnace for compound semicircular solids, like a fence jig, the heating and cooling may be repeated only a few times, or in extreme cases, the first heating and cooling may be repeated. During the cooling cycle, PBN i&111 may crack or the PBN cover may peel off or fall off from the base material, making it unusable, and its reliability is extremely low. In particular, when using PBN-coated carbon parts for compound semiconductor crystal furnaces, if the cracks that occur in the PBN layer are minute,
The occurrence of cracks is not noticed visually, and therefore carbon impurities are mixed into the WG crystal through these minute cracks, but such defects are not detected during crystal growth or when taking out the crystal, and are processed through the grinding process. The problem is that a large amount of raw materials and labor are wasted because the electrical characteristics of the wafer cannot be determined until the electrical characteristics of the wafer are determined, or the characteristics of the product after it has been made into an IC, and its variations are determined. was there.

The Ministry of the Invention and others have conducted various studies to overcome the shortcomings of the above, and have found that in order to obtain an article coated with a PBN layer that has excellent adhesion and is difficult to peel off even after repeated heating and cooling, The present invention was achieved by discovering that the density of the base material (carbon), the precipitation temperature of the PBN layer, and the thickness of the PBN layer need to be within specific ranges.

[Means for solving problems]

The first invention of the present invention is a pyrolytic boron nitride dehydrogenation method in which PBN is deposited and coated on the surface of a base carbon by a chemical vapor phase pyrolysis method using a borogenide gas and ammonia gas as raw materials. An Enoki article, in which the apparent specific gravity of the (+) base carbon is 1.95 to - or less,
and (II) the PBN coating layer has a temperature of 1500 to 1920
℃, and the thickness of the ゛(III) PBN coating layer is 10 μm to 3-
The second invention is a PB'N coated article characterized in that when a PBN coating layer is formed on the surface of the base carbon by a CVD method using boron halide gas and ammonia gas as raw materials, 50 Torrσ ] Under pressure, PBN is precipitated at a pressure of 0.5 to 50 TorrS using a base carbon having a desired shape with an apparent specific gravity of 1.95 f/CI4 or less, and the thickness of the coating layer is 10 μm.
This is a method for producing a PBN-coated article characterized by having ~3 fins.

The present invention will be explained in more detail below.

In the present invention, the base carbon has an apparent specific gravity of 1.9.
It must be less than 5t/-.

The reason for this is that if carbon with an apparent specific gravity exceeding 1.95 t/cd is used as a base material, the adhesion of the PBN layer to the carbon base material will be insufficient, no matter how you choose the precipitation temperature described below. □This is because it is not possible to obtain a PBN S article with excellent PBNI adhesion, which is the object of the present invention.In addition, when the apparent specific gravity of the base carbon is 1.95 f/d or less and exceeds it, The reason why there is a difference in the adhesion strength of the PBN layer is as follows.
The force is also thought to be due to the difference in anchoring effect in the surface pores of the base carbon.

The reason why the precipitation temperature of the PBN coating layer is limited to 1500 to 1920°C is to optimize the strength of the layer to be laminated and the adhesion to the base material. On the other hand, if the precipitation temperature is less than 1500℃, the crystallinity of the PBN layer formed will be low, and the strength of the coated layer itself will be low, and the stress generated by repeated heating and cooling will cause cracks in the PBN layer. This is because it becomes dark. Furthermore, when the precipitation temperature exceeds 1920°C, the adhesion force between the carbon and PBN interface decreases rapidly and the PBN layer is It becomes easy to peel off from the carbon base.

For this reason, the temperature at which the PBN layer is precipitated must be 1500-1920°C, but in order to increase the strength of the PBN layer and to obtain the same and stable layering force, it is especially necessary to set the temperature at 1600-1920°C. It is important to precipitate at a temperature of °C.

The thickness of the PBN overlay must be between 10 μm and 3111I+. If the thickness is less than 10 μm, the thickness of the layer to be laminated is so thin that the base carbon will diffuse into the PBN layer and escape to the outside, and the effect of the PBN layer will not be sufficiently obtained. When the thickness exceeds 3, the residual stress in the PBN a-layer increases and spontaneous peeling of PBN 11 occurs.The latter phenomenon occurs when the thickness of the precipitated PBN layer increases. Later, the thickness of the PBN layer was reduced to 3W!a by mechanical grinding.
Even if the residual stress is large (and therefore non-explosion ψ), in the manufacture of products, the precipitation and precipitation by-products of PBNI must be determined so that the thickness of the deposited film is 3 fins or less. It won't happen.

The PBN-grade product produced by the manufacturing method of the present invention has a high adhesion force of the PBN layer to the base carbon, and the strength of the PBN layer is also high, so the carbon does not evaporate even when heated, and Even after repeated cooling, the PBN material does not exhibit any cracks, cracks or dissolution.

〔Example〕

Example 1 A graphite cylindrical reaction tube with an inner diameter of 10 crn% and a length of 40 m.
It is installed in a resistance heating type hollow heating furnace, and one side of the reaction tube has two
Connect two PBNN gas inlet tubes, each with gaseous BCl
2 and NH3 were flowed. The height in the reactor tube is 0.5 am.
A graphite substrate of various sizes of X 5 cm X 5 cm was placed and heated at 1450 to 196 mm under a pressure of 2 Torr.
100μm/100μm of PBN on graphite substrate at various temperatures of 0°C.
PB was deposited to a thickness of 0.5 hr at a evaporation rate of 0.5 hr.
Testing of graphite plate under N condition was carried out. The sample obtained in this way is
First, the state of the PBN S-covered layer was investigated, and then tests were repeated in which the sample was heated to a temperature of 1400° C. in an ambient atmosphere and then cooled to a temperature of 1,400° C., and the state of each sample was investigated. Table 1 shows the results.
Shown below.

(c) Experiments Nα1 to Nα5 are examples, and experiments m4 to m6 are comparative examples.

Example 2゜P under the same conditions as Experiment 2 of Example 1 except for the precipitation time.
PBN and lead-covered graphite plates with varying thicknesses of the BN layer were cracked. Set each sample in a 1w1JK nitrogen furnace and
' It was heated in a negative Torr atmosphere at a gravitas of 1600° C. for 5 hours, and the weight change before and after the vacuum heat treatment was measured. The results are shown in Figure 2.

Cloth 2 ■ Experiment N [L7-8 are examples, Experiments 9-10 are comparative examples.

〔Effect of the invention〕

As is clear from the above examples, in the PBN article of the present invention, the strength of the PBN I- is high (and the adhesion to the base carbon is strong), so even after repeated heating and cooling, the PBNI&al/- There will be no cracking or peeling or falling off of the PBNa layer (
It can be stably used over long periods of time under thermal cycles. In particular, when the PBN-coated parts of the present invention are used in the carbon heater or susceptor of a compound semiconductor single crystal growth furnace, the electrochronicity of the grown single crystal will not deteriorate because PBN157- prevents carbon evaporation ( Moreover, it has the effect of being able to be used repeatedly over a period of time.

Claims (2)

[Claims] (1) A pyrolytic boron nitride-coated article obtained by coating the surface of a base carbon with boron nitride by a chemical vapor phase pyrolysis method using boron halide gas and ammonia gas as raw materials, and the base carbon The apparent specific gravity of
/cm^3 or less, and the pyrolytic boron nitride coating layer is deposited at a temperature of 1500 to 1920°C, and the pyrolytic boron nitride coating layer has a thickness of 10 μm to 3 mm. Boron nitride coated articles. (2) When a pyrolytic boron nitride coating layer is formed on the surface of the base carbon by a chemical vapor phase pyrolysis method using boron halide gas and ammonia gas as raw materials, an apparent specific gravity of 1.
Using a carbon base material with a desired shape of 95 g/cm^3 or less, pressure 0.5 to 50 Torr, temperature 1500 to 1920
℃ conditions, (a) depositing pyrolytic boron nitride;
A method for producing a pyrolytic boron coated article, characterized in that the thickness of the coating layer is 10 μm to 3 mm.