JP2003073829A - Method for manufacturing vessel of pyrolytic boron nitride - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a vessel for PBN (pyrolytic boron nitride) even with a complicated structure or a large size, in high yield, by a CVD method, without causing deformation and fracture in the vessel. SOLUTION: The method for manufacturing the vessel for pyloritic boron nitride comprises depositing pyloritic boron nitride on a heat-resistant base material by a chemical vapor deposition method (a CVD method) and separating the deposited pyloritic boron nitride layer from the above base material, and is characterized by making a relationship of heat expansion coefficient αA of the heat-resistant base material and heat expansion coefficient αB in a vertical direction (a direction (a)) to the growth direction of pyloritic boron nitride to be 0.1×10<-6> / deg.C<(αA-αB)<2.0×10<-6> / deg.C.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a crucible for pulling up a compound semiconductor, a crucible for vaporizing a metal for molecular beam epitaxy, a boat for growing a crystal, which is obtained by a chemical vapor deposition method (hereinafter referred to as a CVD method). The present invention relates to a method of manufacturing a container made of decomposed boron nitride.

[0002]

2. Description of the Related Art Pyrolytic boron nitride (hereinafter referred to as PBN) is a crucible for pulling up a compound semiconductor, a crucible for evaporating a metal for molecular beam epitaxy, and a jig for growing a crystal because of its excellent heat resistance and strength. It has been widely used as a material for heat sinks, parts for electrical insulation, and the like.

Generally, a PBN container is manufactured by a CVD method, and its shape is often a simple shape such as a rectangular shape, a cylindrical shape, or a plate shape due to restrictions in the manufacturing method. Figure 1 shows a cylindrical P
FIG. 2 is a cross-sectional explanatory view when manufacturing a BN container (crucible), and a method for manufacturing a PBN container will be briefly described below in accordance with this. First, as shown in FIG. 1 (a), PB at 1700 ° C. or higher is performed on a heat-resistant substrate 1 formed by a CVD method so as to obtain a container having a desired shape.
N is vapor-deposited to deposit the PBN layer 2, and after completion of the PBN vapor deposition reaction, they are cooled to room temperature and taken out of the furnace. During this cooling, a gap is created between the heat resistant base material and the PBN layer due to the difference in their respective thermal expansion coefficients. By utilizing this gap, as shown in FIG. 1B, the PBN layer can be pulled out and separated from the heat resistant base material, whereby a PBN container can be obtained.

For example, when a cylindrical PBN container is manufactured, the size of the gap generated between the heat resistant base material and the PBN layer by cooling can be calculated by the following formula. Size of gap = α _A × (reaction temperature−room temperature) × (outer diameter of base material at reaction temperature) −α _B × (reaction temperature−room temperature) × (inner diameter of PBN molded body at reaction temperature) where , Α _A is the coefficient of thermal expansion of the heat resistant substrate, α _B is the direction perpendicular to the growth direction of the pyrolytic boron nitride compact (direction a)
Represents the coefficient of thermal expansion of. The size of the gap represents the difference in the amount of thermal expansion.

By the way, a molecular beam epitaxy (Molecular Be) using such a PBN container is used.
am Epitaxy, abbreviated as MBE) is 10
^A raw material metal serving as a molecular beam source is charged into a crucible in an ultrahigh vacuum of ⁻⁶ to 10 ⁻¹¹ Torr, for example, 500 to 1500.
It is a method of producing a thin film by heating to evaporate and evaporating, and depositing an epitaxial film on the opposing substrate. In this way, the metal evaporation crucible used in the MBE method is heated to a high temperature in an ultra-high vacuum, so there is little degassing, it is chemically stable, and a metal melting crucible made of PBN with excellent heat resistance is the world standard. It is used as a typical component. The PBN container used in the MBE method is generally a cylindrical container or a container having a lip portion 5 at the open end as shown in FIG.

First, as shown in FIG. 2, the PBN container is mounted in an ultrahigh vacuum apparatus and a raw material metal is charged therein. After that, the PBN container is heated by the high melting point metal heater 6 surrounded by the heat shield plate 7. At this time,
The molten metal 3 melted by heating is propagated along the inner wall surface of the container by the action of surface tension and crawls up to the lip portion 5, and further wraps around the outside of the PBN container to approach the heater 6. At this time, when the molten metal 3 that has flown outside the PBN container 4 evaporates, it adheres to the heater 6, and as a result,
There was a problem that the heater 6 was corroded, deteriorated, or damaged. Further, when the PBN container is thermally deformed due to high heat, the molten metal wrapping around the outside of the container may come into contact with the heater, and the heater may be short-circuited and broken.

In order to solve such a problem, JP-A-9-170882 discloses a molecular beam source crucible for MBE in which the outer diameter end of the lip portion of the crucible is bent toward the main body. . This MBE molecular beam source crucible has an enclosure formed by bending to the container side at the outer diameter end of the lip part, and prevents the approach to the heater even if the molten raw material metal crawls along the inner wall of the crucible. As a result, it is possible to prevent damage to the heater and prevent troubles such as short-circuit of the heater.

However, when a PBN container having an outer periphery of such a lip portion is manufactured by the CVD method, as shown in FIG. 3 (a), a heat-resistant substrate 1 having a complicated shape is formed. The PBN layer 2 has to be deposited. Therefore, for example, P formed in the concave portion of the heat resistant substrate
When the BN layer was cooled, a compressive thermal stress was generated due to the difference in thermal expansion coefficient between the heat-resistant base material and PBN, resulting in deformation 8 of the PBN compact as shown in FIG. 3 (b).

Further, at this time, when the PBN container to be manufactured is large, the difference in the thermal expansion amount between the PBN layer and the heat resistant base material also becomes large, and as a result, damage is caused at the time of cooling, so that a desired amount is obtained. There was a manufacturing problem that a PBN container having a shape could not be manufactured.

[0010]

Therefore, the present invention has been made in view of the above problems, and the object of the present invention is to:
For example, a PBN container with a complicated structure, or a large PB
It is an object of the present invention to provide a manufacturing method capable of manufacturing a pyrolytic boron nitride container with a high yield, even if the container is made of N, by the CVD method without causing deformation or damage of the container.

[0011]

In order to achieve the above object, a method for producing a pyrolytic boron nitride container according to the present invention comprises a chemical vapor deposition method (CVD method) and a pyrolytic nitriding method on a heat resistant substrate. A method of manufacturing a pyrolytic boron nitride container by depositing boron and then separating the deposited pyrolytic boron nitride layer from the base material, comprising: a thermal expansion coefficient α _A of the heat resistant base material; The relationship of the coefficient of thermal expansion α _{B in} the direction perpendicular to the growth direction of boron (direction a) is 0.1 ×.
10 ⁻⁶ / ° C. <(α _A −α _B ) <2.0 × 10 ⁻⁶ / ° C.
In this way, the container made of pyrolytic boron nitride is manufactured (Claim 1).

Thus, the coefficient of thermal expansion α of the heat resistant substrate is_A
And the direction perpendicular to the growth direction of pyrolytic boron nitride (direction a)
Direction) thermal expansion coefficient α_BRelationship of 0.1 × 10^-6/ ° C <
(Α _A-Α_B) <2.0 × 10^-6/ ° C
To produce a complex structure by manufacturing a PBN container.
PBN container, or even a large PBN container,
To reduce the compressive thermal stress generated in the PBN layer during cooling.
Can reduce the deformation and damage of the container,
It is possible to manufacture pyrolytic boron nitride containers with high yield.
Wear.

At this time, it is preferable to use a graphite base material as the heat resistant base material (claim 2). As described above, by using the graphite base material as the heat resistant base material, not only the corrosion resistance and heat resistance are excellent, but also the thermal expansion coefficient α _A of the heat resistant base material and the thermal expansion of the pyrolytic boron nitride. The relationship of the coefficient α _B is 0.1 × 10 ⁻⁶ / ° C <
It can be easily adjusted such that (α _A −α _B ) <2.0 × 10 ⁻⁶ / ° C.

The container manufactured by the method for manufacturing a pyrolytic boron nitride container of the present invention has a structure in which at least an opening end of the container has a lip portion and an outer edge of the lip portion is folded back. Can (claim 3),
Further, even if the PBN container has a more complicated structure, the PBN container can be manufactured with a high yield without causing deformation or damage of the container.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The embodiments of the present invention will be described below, but the present invention is not limited thereto. Conventionally, when a PBN container having a complicated structure having a folded portion on the outside of the container is manufactured by a CVD method, when a PBN layer is deposited on a heat resistant substrate and then cooled, the heat resistant base material and the PBN are separated from each other. Due to the difference in the coefficient of thermal expansion, compressive thermal stress was generated in the PBN layer deposited in the recesses of the base material, and the PBN compact was deformed. Furthermore, when the PBN container to be manufactured is large, the difference in expansion amount between the PBN and the heat resistant base material becomes large, and as a result, the PBN layer is damaged,
There has been a problem that a PBN container having a desired shape cannot be manufactured.

Therefore, the present inventors deposited PBN on a heat-resistant substrate at a high temperature by the CVD method, cooled it, and then deposited PBN.
A method of manufacturing a PBN container by separating a BN layer from the base material, comprising a PBN having a complicated structure.
In order to enable the production of high-yield containers without causing deformation or damage, even in the case of large-scale PBN-made containers, the thermal expansion coefficient α _A of the heat-resistant base material and the growth direction of PBN By paying attention to the coefficient of thermal expansion α _B in the vertical direction (direction a), repeated intensive investigations and studies have led to the completion of the present invention.

That is, the relationship between the thermal expansion coefficient α _A of the heat resistant substrate and the thermal expansion coefficient α _{B in} the direction perpendicular to the growth direction of the pyrolytic boron nitride (direction a) is 0.1 × 10 ⁻⁶ / ° C. <
(Α _A −α _B ) <2.0 × 10 ⁻⁶ / ° C. By producing a pyrolytic boron nitride container,
It has been found that even if a PBN container having a complicated structure or a large PBN container is used, a pyrolytic boron nitride container can be manufactured with a high yield without causing deformation or damage of the container.

For example, the coefficient of thermal expansion α of the heat resistant substrate_AAnd P
Thermal expansion coefficient α of BN molded body in a direction _BDifference with (α_A-Α
_B) Is 2.0 × 10^-6If it exceeds / ° C, it will be
The gap between the heat resistant base material and the PBN layer becomes too large,
Deformation occurs when the PBN layer contracts. Especially made
The PBN container to be manufactured is the above-mentioned JP-A-9-17088.
No. 2 has a fold-back on the outer diameter end of the lip.
Crucibles that have
In the case of a PBN container, the shape of the heat resistant substrate becomes complicated,
During cooling, the PBN layer deposited in the recess of the heat resistant substrate
The shrinkage of the heat resistant substrate is too large for the shrinkage.
In addition, strong compressive thermal stress is applied to the PBN compact, causing it to deform or break.
It causes a loss. Therefore, the coefficient of thermal expansion of the heat resistant substrate
α_AAnd thermal expansion coefficient α of PBN compact in a direction_BDifference from
(Α_A-Α_B) 2.0 x 10^-6/ ° C or less,
1.0 x 10^-6/ ° C or less is preferable.

On the other hand, the value of (α _A -α _B ) is 0.1 × 10
^{When it is} less than ⁻⁶ / ° C., the difference in the amount of thermal expansion between the heat resistant base material and the PBN layer is too small, so that a sufficient gap cannot be obtained between the two, and the heat resistant base material and the PBN layer are not formed. It was found that in many cases, the PBN layer could not be separated from the heat resistant substrate due to the adhesion.

As a heat resistant substrate used in the present invention
It is preferable to use a graphite base material. Gu
Lafite substrate has only excellent corrosion resistance and heat resistance
Not with graphite, which exhibits isotropic thermal expansion.
The coefficient of thermal expansion is 4 × 10 ^-6~ 8 × 10^-6/ ° C
While the thermal expansion of PBN shows anisotropy,
The coefficient of thermal expansion in the direction perpendicular to the growth direction (direction a) is
0.1 x 10^-6~ 4 x 10^-6Since it is about / ° C,
Easily the coefficient of thermal expansion of heat resistant base material α_AAnd pyrolytic boron nitride
Expansion coefficient α in the direction perpendicular to the growth direction of_Bconnection of
(Α_A-Α_B) 0.1 x 10^-6/ ° C <(α_A−
α_B) <2.0 × 10^-6/ ° C range
it can.

As shown in FIG. 4A, the PBN container manufactured by the manufacturing method according to the present invention has a lip portion at least at the opening end of the container, and the outer edge of the lip portion is folded back. PBN with a complicated structure
It can be a container. Further, as shown in FIG. 4 (b), a P part having a structure in which the outer side of the lip portion formed by folding back the outer edge is folded back in the opposite direction once again.
A container made of BN, and further a PBN having a more complicated structure having third and fourth folds continuously on the outside thereof.
It can also be a container. Further, a PBN container having a structure in which the folds formed on the outer edge of the lip portion have a wavy shape as shown in FIG. 4C can be easily formed.

As described above, the PBN container, which is manufactured by the manufacturing method according to the present invention and has the folds at the outer edge of the lip portion, can prevent the molten metal from approaching the heater in the MBE method. It is possible to prevent deterioration of the heater made of a high melting point metal. Furthermore, by increasing the folding back of the outer edge of the lip, it is possible not only to further prevent molten metal from approaching the heater, but also to increase the strength of the lip, so deformation due to heat is suppressed to a small extent, and the molten metal and heater It is possible to avoid the risk of short circuit, disconnection, etc. caused by contact. Also,
A recess is formed on the outer side of the lip portion by a plurality of turns, and the molten metal crawling out of the container can be stored in the recess, and the molten metal can be reliably prevented from approaching the heater.

[0023]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples of the present invention, but the present invention is not limited thereto. (Examples and Comparative Examples) First, they have a shape as shown in FIG. 3, and their thermal expansion coefficients α _A are 4.30 and 5.3, respectively.
Prepare 4 types of graphite base materials, 0, 6.10, 7.20, and the PBN container manufactured has an outer diameter of 200 m.
Fig. 4 with m, inner diameter of 150 mm and lip width of 25 mm
The shape of the graphite base material was adjusted so as to have the shape shown in (b), and the graphite base material was placed in an electric furnace.

After that, ammonia was reacted with boron trichloride by the thermal CVD method and deposited on the graphite base material so as to have a thickness of 1 mm. At this time, set the reaction temperature to 17
PBN is obtained by reacting at various temperatures of 50 to 1850 ° C. and a reaction pressure of 50 to 150 Torr.
The coefficient of thermal expansion α _B in the a direction of was varied between 3.20 and 4.22. After PBN was deposited, these were cooled to room temperature and taken out of the furnace, and the graphite base material and the PBN layer were separated to manufacture a PBN container.

Table 1 shows the thermal expansion coefficient α _A of the graphite base material and the a of PBN in each PBN container prepared this time.
The relationship with the thermal expansion coefficient α _{B in the} direction is shown. Also, under each condition, 10 pieces of PBN containers were tried to be manufactured. At that time, the number of deformed PBN containers and the number of graphite base material and PBN that were adhered and could not be separated were examined. Also shown in Table 1.

[0026]

[Table 1]

[0027] As shown in Table 1, the relationship of 0.1 × ^{10 -6} / ℃ with a direction of the thermal expansion coefficient alpha _B in thermal expansion coefficient alpha _A and PBN container made of graphite substrate <(alpha _A- α _B )
When adjusted and manufactured so as to be <2.0 × 10 ⁻⁶ / ° C. (PBN containers (2) to (7), (9) and (1
0)), a PBN container could be obtained without adhesion of the PBN molded body to the heat resistant substrate and almost no deformation.

On the other hand, the relationship of (α _A -α _B ) is 0.
In the PBN container (1) manufactured at less than 1 × 10 ⁻⁶ / ° C., the PBN compact and the heat-resistant base material adhere to each other, and the relationship of (α _A −α _B ) is 2.0 × 10 ^−6. 1 for PBN container (8) in containers manufactured at temperatures above ℃ / ℃
3 out of 0 containers, 8 out of 10 containers (11), and all of the other containers (12) to (16) were deformed or damaged.

The present invention is not limited to the above embodiment. The above-described embodiment is merely an example, and it has substantially the same configuration as the technical idea described in the scope of claims of the present invention, and has the same operational effect.
Anything is included in the technical scope of the present invention.

For example, in the above, the production of the PBN container for metal evaporation used for molecular beam epitaxy has been described as an example, but the present invention is not limited to this, and the crucible for pulling up the compound semiconductor and the boat for crystal growth. The same can be applied to the case of manufacturing various containers such as.

[0031]

As described above, according to the present invention,
Even if a pyrolytic boron nitride container with a complicated structure or a large-sized pyrolytic boron nitride container is used, the pyrolytic boron nitride container can be manufactured with high yield without deformation or damage of the container during the production by the CVD method. A manufacturing method capable of manufacturing a container can be provided.

[Brief description of drawings]

FIG. 1 is a sectional explanatory view showing a manufacturing process of a conventional PBN container.

FIG. 2 is a schematic cross-sectional view when a PBN container is attached to the MBE device.

FIG. 3 is a schematic view showing the deformation of the container that occurs during cooling in the production of the PBN container.

FIG. 4 is a cross-sectional view showing the shape of a PBN container that can be manufactured according to the present invention.

[Explanation of symbols]

1 ... Heat resistant substrate, 2 ... Pyrolytic boron nitride (PBN)
Layer, 3 ... Molten metal, 4 ... Pyrolytic boron nitride (PBN)
Manufacturing container, 5 ... Lip part, 6 ... Heater, 7 ... Heat shield plate, 8 ... Deformation part.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Ryoji Nakajima             2-13-1, Isobe, Annaka-shi, Gunma Shin-Etsu             Gakuin Co., Ltd. Gunma Office F-term (reference) 4G077 AA03 BA01 DA07 EG01 HA20                       SC11                 4K030 AA03 AA13 BA39 CA05 DA08                       FA10

Claims (3)

[Claims] 1. A pyrolytic boron nitride is deposited on a heat-resistant substrate by a chemical vapor deposition method (CVD method), and then the deposited pyrolytic boron nitride layer is separated from the substrate. A method of manufacturing a container, wherein the thermal expansion coefficient α _A of the heat resistant substrate and the thermal expansion coefficient α _{B in} the direction (a direction) perpendicular to the growth direction of the pyrolytic boron nitride are 0.1 ×. 10 ⁻⁶ / ° C. <(Α _A −α _B ) <2.0 × 1
A method for producing a pyrolytic boron nitride container, comprising producing a pyrolytic boron nitride container at a temperature of 0 ⁻⁶ / ° C. 2. The method of manufacturing a pyrolytic boron nitride container according to claim 1, wherein a graphite base material is used as the heat resistant base material. 3. A method for manufacturing the pyrolytic boron nitride container according to claim 1, wherein the manufactured pyrolytic boron nitride container has a lip portion at least at an opening end of the container. A method for producing a pyrolytic boron nitride container, which has a structure in which an outer edge of the lip portion is folded back.