JPS6177691A - Apparatus for manufacturing pyrolytic boron nitride formed body - 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 an apparatus for manufacturing a molded body such as a crucible for pulling an m-v group compound semiconductor single crystal using pyrolytic boron nitride (p-BN).

"Prior Art" Conventionally, a CVD method using NH3 gas and BCl3 or BF3 gas as a reaction gas is known as a method for manufacturing a pyrolytic boron nitride molded body. The compact obtained by this CVD method had high density and high purity, and was excellent as a crucible for a single crystal pulling furnace, for example. This CV
In method D, as shown in Figure 1, a graphite substrate C is held in a reaction chamber surrounded by a heater a on the outer periphery, and B C13 or BF3 gas and NH3 gas are introduced independently from above the reaction chamber. Pyrolytic boron nitride is produced by introducing the two gases through a tube and reacting them at high temperatures! : This conventional technology was used to produce molded bodies.
rsan, J-Composite Matsria
ls, 9 (1975) 22B.

"Problems to be Solved by the Invention" When producing a pyrolytic boron nitride molded body by the CVD method, unreacted B G13 and NH3, which tend to react with each other, were introduced from the upper part of the reaction chamber. YaNH
3 flows downward into the reaction chamber, there was a problem in that only the upper part of the molded body could be molded, and the lower part could hardly be molded.

Therefore, prior to the present invention, the inventors of the present invention
An attempt was made to introduce the gas independently from the bottom of the reaction chamber to the outer periphery of the substrate, but among the reaction gases introduced into the reaction chamber, NH3, which has a light specific gravity, rose into the void above the reaction chamber. The wall thickness of the lower part of the molded product produced was still thin, and the molded product contained too much B and turned brown. Furthermore, if Gutiphite is used as the reaction gas introduction tube, NH3 gas and graphite will react at high temperatures of 1400°C or higher, or BN will adhere to the outer periphery of the introduction tube, causing damage due to thermal stress due to its thermal expansion coefficient being different from that of graphite. There was a problem with that.

"Means for Solving the Problems" The present invention solves the above problems, and includes a rotatable substrate holder placed in the reaction chamber, a heater provided around the outer periphery of one reaction chamber, and Install an M shield plate on the NH
A BCl3 or BF) gas introduction pipe and an NH3 gas introduction pipe are arranged around the outer periphery of the substrate holding table to prevent the rise of the three gases.
By reacting BCl3 or BF3 with NH3, pyrolytic boron nitride was deposited on the outer circumferential surface of the substrate, thereby making it possible to produce a molded body. Further, the gas introduction pipe was formed of a BN sintered body to prevent corrosion by NH3 and to prevent damage.

B (When the lx gas introduction tube passes through the upper part of Matsufuru, the BOh gas is preheated and introduced into the reaction chamber, so its decomposition is more active.BClx
When both the gas introduction tube and the NHt gas introduction tube are introduced from the lower part of the reaction chamber, each introduction tube can be easily removed, which is convenient for replacing the introduction tube.

Next, the present invention will be explained in more detail with reference to FIGS. 2 and 3. A reaction chamber 1 is formed in the center of the cylindrical matuffle 2, and a holding table 3 is placed in the lower part of the reaction chamber 1. The holding table 3 holds a graphite base 4 on its upper surface, and this holding table has a shaft 5.
It is formed to be rotatable by a rotating device (not shown) via the.

A shielding plate 6 made of graphite is provided at the top of the reaction chamber 1 to partition the inside of the Matsufuru 2, and an N Hx gas introduction pipe 7 and a B (lx or BFx gas introduction pipe 8) are connected to the outer peripheral position of the holding table 3. The MHI gas introduction pipe 7, which is arranged in the vertical direction of the chamber 1, is formed of a sintered body of boron nitride (BN) to prevent it from being exposed to NH3 when the temperature rises, and to
3 or the introduction pipe 8 of BF3 may be made of graphite,
Introductory tube 8, which is preferably made of BN like introductory tube 7
When graphite is used, BN is added to the inlet pipe by CVD.
A thick film is formed with good adhesion, and because the thermal expansion coefficients of graphite and BN are different, the pipe will break due to temperature cycles1.
．． A large number of injection holes 7a and 8a are provided in the vertical direction at the tip of each of the four tubes 7.8. The NH3 introduction pipe 7 supplies N into the reaction chamber 1 from the injection hole 7a.
In the case of the present invention, in which Hx gas can be injected at a rate of 10'O to 2500 cc/min, since the holding table 3 rotates, two B C13 inlet pipes 8 are provided on both sides of the NH3 inlet pipe 7. Although both gases were made to circulate well in the reaction chamber, when the holding table is not rotated, it is sufficient to install a large number of inlet pipes 7.8 around the holding table.

The introduction pipe 8 for BCh or BF3 passes through a through hole 10 surrounded by a heat insulating material (described later) in the upper part of Matsuful through a through hole 9 provided in the shielding plate 6;
This section is sufficiently preheated so that its decomposition is carried out even more actively, so that BC13 can be introduced into the reaction chamber 1 at a rate of 20 to 500 cc/min. In addition, H2 or A'' is introduced as a carrier gas into the introduction tube 8 of B C10, and can be injected into the reaction chamber from the injection hole 8a at a rate of 100 to IQOOcc/min together with B C13. , B
The pressure in the reaction chamber 1 into which Gh, H2, or At is introduced is set to 1 to 20 mmHg, which is a desirable state for producing a pyrolytic boron nitride compact. The reason for introducing the carrier gas is to uniformly introduce 8013 gas throughout the reaction chamber since B C13 is less than NH3.

A graphite heater 11 is installed around the outer periphery of the Matsufuru that forms the reaction chamber 1.
It can be heated to 0°C. The outer periphery of the heater 11 and the outer periphery of the mer, upper and lower parts of the heater 11 are covered with a heat insulating material 12, and a heat insulating material 1 is also provided inside the mats full and at the upper part of the reaction chamber.
3 are provided, and the entire outer periphery thereof is covered with a heat-resistant case 14.

In the explanation in Section 1, the introduction pipe 8 for BCl3 or BFx gas is passed through the shielding plate 6, and BCh or Bx is introduced from the upper part of the reaction chamber.
Although Ft gas was introduced, the one shown in Fig. 4 is B C1
The introduction pipe 8 for the three gases was introduced from below the reaction chamber 1 without penetrating the shielding plate 6. In this case as well, a large number of injection holes 8a are provided at the tip of the introduction tube 8, and B
In the case of this configuration in which CIx gas flows, unlike the case shown in FIG. 3, the inlet pipe 7.
8 is easy to remove, it is easy to remove the BN film attached to the introduction tube, and it is easy to replace the introduction tube when it is damaged.

"Function" When B C1x gas and NH3 gas are introduced into the reaction chamber 1 from the respective introduction pipes 7.8 while rotating the substrate holding table 3, the NH3 gas rises inside the reaction chamber, but the upper shielding plate 6
Because of this, the upper part of reaction chamber 1 is immediately filled with NH3,
NHz sufficiently spreads to the lower part of the reaction chamber, so the two gases react in the reaction chamber heated to high temperature by the heater 11.

Pyrolytic boron nitride adheres to the entire outer circumferential surface of the base 4 to produce a molded body. The produced molded body is B Oh gas and NH
Since the y gas is distributed from the top to the bottom of the reaction chamber 1, the molded body has a substantially uniform thickness.

"Example" Next, an example in which a pyrolytic boron nitride molded body was actually manufactured using the manufacturing apparatus of the present invention will be described. Inner diameter 753 mm, depth 75 mm, thickness 0.5 m + *c7) A crucible-shaped base 4 made of graphite for the purpose of creating a crucible.
was placed in a graphite Matsufuru Z with an inner diameter of 150 IIrm and a graphite heater 11 was placed on the outside thereof, and after first performing vacuum evacuation, it was heated to 1800° C. by the heater 11. B while keeping it at 1800℃
BCl3 or BF3 gas (200c
c/min) and NH3 gas (1000 cc/min) were flowed into the reaction chamber 1, and at the same time, H2 gas (IHOcc/min) was flowed together with BCl3 gas as a carrier. The pressure was maintained at 10 Torr by adjusting the displacement of the vacuum pump. BOh gas and NH3 gas were introduced into the reaction chamber 1 in the Matsufuru in the following manner. As shown in Figure 3, BO
h gas is applied from above Matsuful 2 to the outer circumference of base 4 with an inner diameter of 6 m.
The mixture was introduced into a graphite introduction tube 8 having a diameter of 1.5 mm and flowed toward the substrate 4 through an injection hole 8a having a diameter of 1.5 m. The purpose of introducing BOh gas from the top of Matsufuru 2 is to sufficiently preheat BClz gas before introducing it into the reaction chamber l.
This is to make the decomposition more active. NH3 gas is supplied from below Matsuful through BN with an inner diameter of 6rxm.
The gas was introduced to the outer periphery of the substrate 4 through an inlet tube 7, and flowed toward the substrate through an injection hole 7a with a diameter of 1.5 mm. It was installed approximately 30 degrees apart from tube 7.

CVD was carried out for 5 hours, and after cooling to room temperature, the substrate 4 was taken out. The thickness of the milky white BN film attached to the outer peripheral surface of the base is 0.6 mm on the upper surface of the base and 0.7 mm on the upper part of the peripheral wall of the base.
IIm and 0.8 IIm at the lower part of the substrate peripheral wall, which was almost uniform.

Here, an example in which a pyrolytic boron nitride molded body was actually manufactured using the manufacturing apparatus shown in FIG. 4 will be described.

In order to create a crucible with an inner diameter of 100 ta layers, a depth of 100 mm, and a thickness of 1 mm, a crucible-shaped base 4 was prepared with an inner diameter of 1 mm.
The reaction gas was placed in the reaction chamber 1 in a 50 mm graphite Matsufuru, heated to 1950°C, and subjected to CVD. The injection holes 7a and 8a having an inner diameter of 1.5 arms provided in the introduction tube lead to the outer periphery of the base body 4.
Gas was flowed towards. 1 wooden NH3 gas introduction pipe 7
BCl3 or BF3 approximately 30' apart circumferentially on either side of
Two gas introduction pipes 8 were installed, and CVD was performed for 20 hours. The reaction gas flow rate at this time is 2
50 cc/min, NH3 gas at 1500 cc/min, H2 as carrier at 1000 cc/min, and the reaction pressure was 5
It was set to Torr. The thickness of the milky white BN film attached to the outer peripheral surface of the base 4 is 1.0 ms+ on the upper surface of the base, 1.2 ml on the upper part of the peripheral wall of the base, and 0.0 ml on the lower part of the peripheral wall of the base. θ
am, it became almost uniform.

"Effects of the Invention" According to the apparatus of the present invention, NH3 introduced into one reaction chamber is prevented from rising by the upper shielding plate, so that it sufficiently reaches the lower part of the substrate, reacts with NH, and is completely absorbed. A pyrolytic boron nitride molded body having a substantially uniform wall thickness is formed. Also B
Since the C1z and NHJ inlet pipes are made of boron nitride, they will not corrode even at high temperatures.

[Brief explanation of the drawing]

ft51 is a schematic diagram of a conventional apparatus for producing a pyrolytic boron nitride compact, FIG. 2 is a sectional view of the apparatus for producing a pyrolytic boron nitride compact of the present invention, and FIG. 3 is an enlarged view of the main parts of FIG. 2. FIG. 4 is a sectional view of a main part of the second embodiment. 1; reaction chamber 3; holding table 4; base 6; shielding plate 7; introduction tube 8; introduction tube 11; heater

Claims (4)

[Claims] (1) A rotatable substrate holder is placed inside the reaction chamber, a heater is provided around the outer periphery of the reaction chamber, a shielding plate is provided at the top of the reaction chamber, and an NH_3 gas introduction pipe and BCl_3 or BF_3 are placed on the outer periphery of the substrate holder. This is a production device for pyrolytic boron nitride molded bodies, in which gas inlet pipes and gas inlet pipes are arranged in the upper and lower directions of a reaction chamber, respectively. (2) The NH_3 gas introduction pipe is introduced into the reaction chamber from below the reaction chamber, and the BCl_3 or BF_3 gas introduction pipe is introduced into the reaction chamber from above the shielding plate.
An apparatus for producing a pyrolytic boron nitride molded body according to 2. (3) NH_3 gas introduction pipe and BCl_3 or BF_3
The apparatus for producing a pyrolytic boron nitride molded body according to claim 1, wherein the gas introduction pipe is introduced into the reaction chamber from below the reaction chamber. (4) Claim 1 in which each introduction pipe for NH_3 gas and BCl_3 or BF_3 gas is formed of a BN sintered body.
An apparatus for producing a pyrolytic boron nitride molded body according to 2.