JPH01201481A - Method and apparatus for vapor phase synthesis of high-pressure phase boron nitride - Google Patents

Abstract

PURPOSE:To grow high-pressure phase BN in a vapor phase on an arbitrary substrate at a high film forming speed by blowing a cooling gas to a plasma jet formed from gases by electric discharge to rapidly cool the plasma jet and bringing the formed nonequil. plasma into contact with the substrate. CONSTITUTION:The discharge gases 3 contg. a boron compd. such as H2B6 and nitrogen compd. such as NH3 is supplied as a raw material compd. for vapor growth to a hot plasma generator and is converted to radicals by the arc 11 of the electric discharge, by which the hot plasma is formed. This plasma is ejected from a nozzle 4 to form the plasma jet 5. The cooling gas such as H2 is vigorously blown from an ejection port 6 to the plasma jet 5 to rapidly cool the hot plasma. The active nonequil. plasma 12 which contains the radical product of the above-mentioned raw material compd. and has the high concn. thereof is thereby formed. The substrate 8 to be treated is brought into contact with this nonequil. plasma 12. The BN film 9 chemically vapor-grown from the hot plasma is thereby vapor-grown on the substrate 8, by which the high- pressure phase BN is vapor-grown.

Description

Detailed Description of the Invention [Summary] The present invention relates to a method and apparatus for vapor-phase synthesis of high-pressure phase boron nitride (BN), and relates to a method and apparatus for vapor-phase synthesis of high-pressure phase boron nitride (BN) on an arbitrary substrate at a high film formation rate. The purpose of this method is to supply a gas to a thermal plasma generator, turn the gas into radicals through electric discharge, create thermal plasma, and eject the generated thermal plasma from a nozzle at the tip of a torch as a plasma jet. , the thermal plasma is rapidly cooled by blowing a cooling gas onto the plasma jet, and contains at least radical products generated by radicalization of boron compound gas and nitrogen compound gas, which are raw material compounds for vapor phase growth supplied to the plasma jet. The device is configured to generate an active non-equilibrium plasma with a high concentration of radicals, bring a substrate into contact with the non-equilibrium plasma, and grow a high-pressure boron nitride film on the substrate using thermal plasma chemical vapor deposition (CVD). do.

[Industrial Application Field] The present invention relates to a method for continuously vapor-phase synthesis of high-pressure phase boron nitride (BN) at a high film forming rate.

High-pressure phase BN (cubic BN (hereinafter referred to as c-BN), wurtzite type BN (hereinafter referred to as w-BN)) has high thermal conductivity and hardness comparable to diamond, and also exceeds diamond in heat resistance. Therefore, it is expected to be used in a wide range of fields, such as heat sinks for semiconductor devices, high-density mounting boards, and even high-hardness coating films for various tools.

[Conventional technology]

Conventionally, the IBD method (ionized vapor deposition), HCD-ARE method (hollow cathode activated chemical vapor deposition), and IVD method (combined ion vapor deposition method) are known as vapor phase synthesis methods for high-pressure phase BN. The BN obtained by this method contains low-pressure phase BN (h-BN) with a graphite structure and amorphous components, and the film forming speed is slow at less than 1 μm/h, resulting in poor quality, cost, productivity, etc. In both respects, it was far from practical application.

Recently, the present inventors have focused on the high chemical activity of thermal plasma, and have rapidly cooled the thermal plasma to freeze the high gas dissociation rate at high temperatures. After the idea of supplying plasma onto a substrate, a DC plasma jet CVD method, a high frequency induced plasma jet CVD method, or an optical plasma jet CVD method was discovered earlier. This method is a method in which thermal plasma generated by DC arc discharge, photoarc discharge, or high-frequency induced discharge is quenched by hitting a water-cooled substrate as a plasma jet, thereby rapidly synthesizing high-pressure phase BN on the substrate. . In this method, 10
Although extremely high film forming speeds of μm/h or more can be obtained, the substrate must be sufficiently cooled in order to increase the quenching effect of the thermal plasma, which places strong constraints on the substrate.
For example, the substrate had high thermal conductivity and could only be thin.

[Problems to be Solved by the Invention] The present invention solves the problems of the prior art described above, and
It is an object of the present invention to provide a method for vapor phase growth of N on any base substrate at a high deposition rate.

[Means to solve the problem]

According to the present invention, the above problem can be solved by supplying gas to a thermal plasma generator, converting the gas into radicals by direct current arc discharge between electrodes to generate thermal plasma, and then applying the generated thermal plasma as a plasma jet to a nozzle at the tip of a torch. A cooling gas is blown onto this plasma jet to cool the thermal plasma and generate radicals generated by radicalization of boron compound gas and nitrogen compound gas, which are the raw material compounds for vapor phase growth supplied to the plasma jet. An active non-equilibrium plasma containing at least products and a high concentration of radicals is generated, a substrate is brought into contact with the non-equilibrium plasma, and a film of high-pressure phase boron nitride is formed on the substrate by thermal plasma chemical vapor deposition (CVD). The problem is solved by a thermal plasma vapor phase synthesis method of high pressure phase boron nitride grown in vapor phase. Thermal plasma generators include, for example, a DC plasma torch that radicalizes the supplied gas to generate thermal plasma by direct current arc discharge between an anode and a cathode, and a DC plasma torch that radicalizes the supplied gas to generate thermal plasma by arc discharge using high-frequency induction. It is possible to use a device that generates thermal plasma by radicalizing the supplied gas by photoarc discharge using a focused high-power laser beam.

According to the present invention, there is further provided a plasma torch in which a thermal plasma jet ejection nozzle is opened, gas supplied from a discharge gas introduction tube is turned into thermal plasma by electric discharge, and the generated thermal plasma is ejected from the nozzle as a plasma jet. a raw material gas supply system that supplies a gaseous raw material compound for vapor phase growth to the plasma jet; and a raw material gas supply system that blows a cooling gas onto the plasma jet to rapidly cool the thermal plasma to supply the raw material compound for vapor phase growth to the plasma jet. A cooling gas supply system having a cooling gas outlet disposed close to the nozzle of the plasma torch, which generates an active non-equilibrium plasma with a high radical concentration and containing at least radical products generated by radicalization of a compound. and a substrate support mechanism for supporting a substrate in the non-equilibrium plasma and depositing a thermal plasma chemical vapor deposition (CVD) boron nitride film on the substrate. An apparatus for vapor phase synthesis of boron is provided.

[For production]

In the present invention, as a means for rapidly cooling the thermal plasma, a method of blowing gas onto the plasma jet (gas cooling method) is used instead of colliding the thermal plasma jet with a cooled substrate to cool it.

This method of the present invention instantly cools the thermal plasma by forcibly mixing the plasma jet with a gas at about room temperature, so that a non-equilibrium plasma can be created completely independent of the substrate. Therefore, simply by adjusting and holding the workpiece in this non-equilibrium plasma at a temperature at which high-pressure phase BN can be generated, high-pressure phase BN can be synthesized on the surface of the workpiece at high speed.

FIG. 1 is a diagram showing the principle of high-pressure phase BN synthesis by the DC plasma jet CVD method using gas cooling according to the present invention. 1st
In figure (a), (1) is the cathode, (2) is the anode, (3
) is a discharge gas, (4) is a nozzle, (5) is a plasma jet, (6) is a cooling gas outlet, (7) is a cooling gas, (
8) is a substrate, (9) is a high-pressure phase BN film, (10) is an arc power source, (11) is an arc, and (12) is a non-equilibrium plasma. As the plasma torch 13, one having a single pole as shown in FIG. 1(b), a multi-pole as shown in FIG. 1(c), etc. can be used.

While flowing a discharge gas (3) consisting of hydrogen gas and raw material gas, a DC voltage is applied between the cathode (1) and the anode (2) to cause an arc discharge (11), whereby the discharge gas is rapidly heated. , a thermal plasma of 5000°C or more is generated near the nozzle (4). At this time, due to the volume expansion caused by the rapid temperature rise, the thermal plasma becomes a supersonic plasma jet (
5) and is ejected from the nozzle (4).

By forcefully blowing hydrogen gas as a cooling gas (7) onto this plasma jet (5) and forcing the mixture, the thermal plasma is rapidly cooled and a non-equilibrium plasma (12) is generated. The substrate (8) is placed in this non-equilibrium plasma (12).
(and a high-pressure phase BN film (9) grows on its surface.

As described above, in the present invention, compared to the conventional DC plasma jet 1-CVD method, the thermal plasma can be rapidly cooled completely independent of the substrate, so there is no restriction on the substrate, and high-pressure phase BN can be rapidly deposited on any substrate. can be grown to.

In the present invention, any material gas may be used as long as it contains nitrogen and boron, but Nlh and Nz are preferable as the nitrogen source, and BtHh is preferable as the boron source. Further, the raw material gas may be introduced as a cooling gas instead of as a discharge gas.

An inert gas such as Ar or lie may be mixed with the discharge gas or cooling gas. In this case, although the stability of the plasma is improved, the film forming rate is reduced.

In addition, non-high pressure phase B such as amorphous BN is added to the discharge gas or cooling gas.
0□ to increase the etching effect of N.

A small amount of oxidizing gas such as H2O, H20□, and CO may be mixed.

Since hydrogen, which has a high ionization potential and is difficult to discharge, is used as the discharge gas, the electrode material should preferably have high heat resistance. Tungsten to which rare earth element oxides such as lanthanum oxide, yttrium oxide, and cerium oxide are added is excellent as an electrode material. Furthermore, if contamination with impurities from the electrode is to be avoided, it is preferable to use a high-purity carbon electrode.

FIG. 2 is a principle diagram of high-pressure phase BN synthesis by RF plasma jet CVD method using gas cooling according to the present invention. (1
3) is a high frequency coil, (14) is a water-cooled plasma tube, (15) is a discharge gas, (16) is a plasma jet,
(17) is a cooling gas outlet, (18) is a cooling gas, (1
9) is a substrate, (20) is a high-pressure phase BN film, (21) is a high frequency power source, (22) is an arc, (23) is a non-equilibrium plasma, and (24) is a torch nozzle.

By flowing a discharge gas (15) consisting of hydrogen gas and raw material gas into a water-cooled plasma tube (14) and causing an arc discharge (22) by high-frequency induction, the discharge gas is rapidly heated and heated inside the water-cooled plasma tube (4). 5000°C
It becomes a thermal plasma. At this time, the thermal plasma becomes a supersonic plasma jet (16) due to volume expansion due to the rapid temperature rise, and is ejected from the torch nozzle (24).

By forcefully blowing hydrogen gas as a cooling gas (18) into this plasma jet and forcibly mixing it, the thermal plasma is rapidly cooled and a non-equilibrium plasma (23) is generated. When a substrate (19) is placed in this nonequilibrium plasma, a high-pressure phase BN film (20) grows on its surface.

As described above, in the present invention, compared to the conventional RF plasma jet CVD method, the thermal plasma can be rapidly cooled completely independent of the substrate, so there is no restriction on the substrate, and high-pressure phase BN can be grown at high speed on any substrate. can be done.

FIG. 3 is a diagram showing the principle of high-pressure phase BN synthesis by the photoplasma torch (CVD) method using gas cooling according to the present invention. (25
) is a high-power laser, (26) is a laser beam, (
27) is a condensing lens, (28) is a discharge gas, (29)
is nozzle cooling water, (30) is water-cooled torch nozzle, (31
) is plasma jet, (32) is cooling gas, (33)
(34) is a condensing cone, (35) is a non-equilibrium plasma, (36) is a substrate, (37) is a high pressure phase BN film, and (38) is an arc.

A discharge gas (28) consisting of hydrogen gas and source gas is flowed into a condensing cone (34), and a focused laser beam (2
6) to cause a light arc discharge near the torch nozzle, the discharge gas is rapidly heated and becomes thermal plasma at a temperature of 5000°C or more. At this time, due to the volume expansion caused by the rapid temperature rise, the thermal plasma becomes a supersonic plasma jet (3
1) and is ejected from the nozzle (30).

By forcefully blowing hydrogen gas as a cooling gas (32) into this plasma jet and forcibly mixing it, the thermal plasma is cooled and a non-equilibrium plasma (35) is generated. When the substrate (36) is placed in this nonequilibrium plasma,
A high-pressure phase BN film (37) grows on its surface.

As described above, in the present invention, compared to the conventional optical plasma jet CVD method, thermal plasma can be generated and cooled completely independently of the substrate, so there are no restrictions on the substrate (high-pressure phase BN can be deposited on any substrate). Can be grown quickly.

[Example I]

FIG. 4 shows a high-pressure BN vapor phase synthesis apparatus using the gas-cooled DC plasma jet CVD method according to the present invention, in which (39) is a plasma torch, (40) is a discharge gas supply pipe, and (41) is a Arc power supply, (42) is cooling water pipe for torch, (43) is board holder, (44) is board, (45)
) is the vacuum chamber, (46) is the exhaust system, (47) is the torch manipulae, (48) is the mff1 meter, (49) is the gas cylinder, (50) is the cooling gas outlet, and (51) is the substrate manipulae. be.

Both the anode and cathode of the plasma torch (39) are 2% by weight.
It is made of tungsten with yttrium oxide and has a water-cooled structure. The plasma torch 39 and the substrate holder 40 are
Since the position and orientation can be controlled by the manipulators 47 and 51, it is possible to uniformly grow a high-pressure phase BN film even on a large-area substrate or a workpiece with a complicated surface shape. Further, although not shown in FIG. 4, the substrate holder 43 may be equipped with a heater for heating the substrate or a water cooling mechanism in order to control the temperature of the substrate.

[Example 1-11 As the substrate 8, 5 x 5 x 0.2 +nra Si
Using a wafer, the inside of the vacuum chamber 19 is heated to 2Xl0-3T.
After exhausting to orr, hydrogen was used as a discharge gas at a pressure of 1 kg/cm at 201/l1in.

B, II, at a pressure of 1 kg/c+a 80
Flow at a flow rate of mff1/win, hydrogen as a cooling gas at a pressure of 1 kg/c barge at 20f/+++in, ammonia NH, at a pressure of 1kg/a11 at a pressure of 200111f.
fi/min, the pressure inside the vacuum chamber is 200 Torr.
was held at The cooling gas was ejected toward the plasma jet from four cooling gas ejection ports installed below 3M of the torch nozzle. A current of IOA was applied to the torch from a constant current arc power source and maintained for about 5 minutes until the voltage became constant. The voltage at this time was 65V. Slowly bring the board closer to the torch and set the distance between the nozzle and the board to 511II! It was fixed at +, and film formation was performed in this state for 10 minutes.

The resulting high-pressure phase BN was then examined using a scanning electron microscope (SEM).
Evaluation was made by X-ray diffraction and hardness measurement.

The resulting high-pressure phase BN film has a thickness of 10 μm and a thickness of 60 μm/
High-pressure phase BN could be synthesized at an extremely high film forming rate of h. X
In the line diffraction results, peaks of only c-BN and w-BN were detected, and no heater of h-BN was detected at all. Also, the Vickers hardness is approximately 40 at a load of 500g.
00kg/c+fl, c synthesized by high pressure method
-The value was equivalent to BN.

From the above results, it can be seen that the synthesized high-pressure phase BN is a high-quality polycrystalline film. In addition, the film forming speed is 60 μm
/ h.

(Example 1-2) Synthesis of c-BN Hydrogen was used as a discharge gas at a pressure of 1 kg/c+M.
01/min,,B,Il,l kg/afl
100-/min at a pressure of 1k of hydrogen as a cooling gas.
2042/min, NH, 1k at a pressure of g/crM
When BN was synthesized under the same conditions as in Example 1, except for the flow rate of 1ffi/min at a pressure of g/CTII,
approximately 15 μm thick c containing wurtzite BN (w-BN)
- A film of BN was formed. No h-BN having a graphite structure was detected in this film by X-ray diffraction.

In the above embodiment, as a means to rapidly cool the thermal plasma and generate an active non-equilibrium plasma with a high concentration of radicals, an example is given in which cooling gas is blown onto the plasma from four cooling gas outlets in the thermal plasma jet. Although mentioned above, the cooling gas may be ejected from the circumferential direction toward the axial center of the plasma jet.

Note that when it is desired to have a temperature distribution or a distribution in radical temperature, the cooling gas may be ejected from only one direction to the plasma jet.

[Example ■] Figure 5 is a schematic diagram of a high-pressure phase BH synthesis apparatus by the gas-cooled RF plasma jet CvD method in which the present invention is implemented.
52) is a plasma torch, (53) is a discharge gas supply pipe,
(54) is a high frequency power supply (55) is a cooling water pipe for the torch, (56) is a substrate holder, (57) is a substrate, (58) is a vacuum chamber, (59) is an exhaust system, and (60) is a torch manu- facture. The plate (61) is a flow meter, (62) is a gas cylinder, (63) is a cooling gas outlet, and (64) is a substrate manipulator plate.

The plasma torch (52) has a structure in which a high-frequency coil of water-cooled copper pipe is wound around a water-cooled quartz plasma tube. Since the positions and orientations of the plasma torch and substrate holder can be controlled by manipulating, it is possible to uniformly grow BNlil even on a large-area substrate or a workpiece with a complex surface shape. Also,
Although not shown in this schematic diagram, a heater water cooling mechanism for heating the substrate may be attached to control the substrate temperature.

[Example ■-1] Base) Using a 5 x 5 x 0.2 mm Si wafer as a substrate,
After evacuating the chamber to 2 X 10-3 Torr, hydrogen was evacuated as a discharge gas at a pressure of 1 kg/c++1.
min,, B2t16 at a pressure of 1 kg/a+1 and 50++ fl/min% hydrogen as a cooling gas for 1k
101/min at a pressure of g/aa, 1 k of NO3
The flow rate was 90 mfl/min at a pressure of g/crA. Cooling gas was ejected toward the plasma jet from a four-piece nozzle installed below 3M of the torch nozzle. A high frequency power of 27.12 ML and 1 kW was applied to the high frequency coil from a high frequency power source to generate a plasma jet.

Next, the substrate was slowly brought closer to the torch, the distance between the nozzle and the substrate was fixed at 5 mm, and film formation was performed for 10 minutes in this state. The resulting high-pressure phase BN was then examined using a scanning electron microscope (SEM).
), X-ray diffraction, and hardness measurement.

The synthesized high-pressure phase BN film has a thickness of about 10 μm, and in X-ray diffraction, peaks of only c-BN and w-BN were detected, and h
-BN was not detected. Further, the Vickers hardness was approximately 4000 kg/C at a load of 500 g, which is a value equivalent to that of c-BN synthesized by the high-pressure method.

From the above results, it can be seen that the synthesized high-pressure phase BN is a high-quality polycrystalline film. In addition, the film forming speed is 60 μm/
It can be seen that it has reached h.

(Example ■) Fig. 6 is a schematic diagram of a gas phase synthesis apparatus using the gas-cooled light plasma jet CvD method in which the present invention is implemented, (65) is a plasma torch, (66) is a discharge gas supply pipe, (67) is the laser, (68) is the cooling water pipe for the torch, (69) is the substrate holder, (70) is the substrate, (71) is the vacuum chamber, (72) is the exhaust system, (73) is the laser beam, (7
4) is a flow meter, (75) is a gas cylinder, (76) is a cooling gas outlet, and (77) is a substrate manipulator.

As a light source, the oscillation frequency is 10.6μm, and the output is 20kW.
.

A flow type C (h laser) with a beam diameter of 80 mm was used, and the condensing lens had an aperture of 80 mm, fl, 5. The position and orientation of the substrate holder can be controlled by a manipulator, so it is possible to handle large-area substrates or complex substrates. The target substance can be grown uniformly even on the surface of the workpiece. Although not shown in this schematic diagram, a heater for heating the substrate and a water cooling mechanism are installed to control the substrate temperature. It's okay to be beaten.

[Example ■-1] Using a 5 x 5 x O, 2 mm Si wafer as the substrate, the chamber was evacuated to 2 x 10-' Torr, and then hydrogen was added as a discharge gas at a pressure of 1 kg/c+a.
01/min, B2H6 at a pressure of 1 kg/cJ
0m1/ll1in, hydrogen as cooling gas 1kg/c
+Il pressure 101/min, Nt13 1k
90 relatives/min at a pressure of g/cd? I did JL. Cooling gas was ejected toward the plasma jet from four ejection ports installed 3 mm below the torch nozzle. A laser beam with an output of 10 kHz was irradiated using a laser transmitter to cause a photoarc discharge and generate a plasma jet. Next, the substrate was slowly brought closer to the torch, the distance between the nozzle and the substrate was fixed at 511 IITl, and film formation was performed for 10 minutes in this state. The resulting high-pressure phase BN was then examined using a scanning electron microscope (
SEM), X-ray diffraction, and hardness measurement.

The synthesized high-pressure phase BN film had a thickness of about 10 μm, and in X-ray analysis, peaks of only c-BN and w-BN were detected, and h-BN was not detected. Further, the Vickers hardness was approximately 4000/cffl at a load of 500 g, which was a value equivalent to that of c-B and N synthesized by the high-pressure method.

From the above results, it can be seen that the synthesized high-pressure phase BN is a high-quality polycrystalline film. In addition, the film forming speed is 60 μm/
It can be seen that it has reached h.

[Effect] According to the gas-cooled plasma torch (CVD method) of the present invention,
High-quality high-pressure phase BN can be formed at a fast film-forming speed of about 60 μm/h without cooling the substrate.
The range of coating applications can be greatly expanded.

In addition, we also offer high-pressure phase BN heat sinks and high-pressure phase B heat sinks for semiconductors.
We were able to make great progress in realizing the N circuit board.

[Brief explanation of the drawing]

1(a), (b), and (c) are diagrams of the principle of the DC plasma vapor phase synthesis method of the present invention; FIG. 2 is a diagram of the principle of the RF plasma vapor phase synthesis method of the present invention; 3 is a diagram showing the principle of the optical plasma vapor phase synthesis method of the present invention, FIG. 4 is a drawing showing the gas-cooled DC plasma jet vapor phase synthesis apparatus of the present invention, and FIG. 5 is a diagram showing the gas-cooled RF synthesis apparatus of the present invention. 6 is a drawing showing a plasma vapor phase synthesis apparatus, and FIG. 6 is a drawing showing an optical plasma vapor synthesis apparatus of the present invention. DESCRIPTION OF SYMBOLS 1...Cathode, 2...Anode, 3...Discharge gas, 4...Torch nozzle, 5...Plasma jet rod 6...Cooling gas outlet, 7...Cooling gas, - Substrate, 9... High pressure phase BN film, 10... Arc power supply, 11... Arc, 12... Nonequilibrium plasma, 13... High frequency coil, 14... Water-cooled plasma tube, 15. ...discharge gas, 16...plasma jet, 17...cooling gas outlet, 18...cooling gas,
19...Substrate, 20...High pressure phase BN film,
21... High frequency power supply, 22... Arc, 23.
...Non-equilibrium plasma, 24...Torch nozzle, 25.
...High power laser, 26...Laser beam, 27
...Condensing lens, 28...Discharge gas, 29...
・Nozzle cooling water, 30...Water-cooled torch nozzle, 31
... Plasma jet, 32... Cooling gas, 33... Cooling gas outlet, 34... Condensing cone, 35... Non-equilibrium plasma, 36... Substrate, 37... High pressure phase B.N.
Film, 38... Arc, 39... Plasma torch, 40... Discharge gas supply pipe, 41... Arc power source 42... Cooling water piping for torch, 43... Substrate holder, 45...・Vacuum chamber,
46... Exhaust system, 47... Torch manipulator, 48... Flow meter, 49... Gas supply system, 5
0... Cooling gas outlet, 51... Board manipulator. 52... Plasma torch, 53... Discharge gas supply pipe, 54... High frequency power supply, 55... Cooling water piping for torch, 56... Substrate holder, 57... Substrate,
58... Vacuum chamber, 59... Exhaust system 60...
・Torch manipulator, 61...Flow meter, 62...Gas cylinder, 6
3... Cooling gas outlet, 64... Substrate manifold, 65... Plasma torch, 66... Discharge gas supply pipe, 67... Laser, 68... Cooling water piping for torch, 69 ...Substrate holder, 70...Substrate, 71...Vacuum chamber, 72...Exhaust system, 7
3... Laser beam, 74... Flow meter, 75...
・Gas cylinder, 76...Cooling gas outlet, 77・
・Substrate manipula 1・ Cathode 4・ Nozzle 5 ・Norazumanoe, Toro・ Cooling gas ejection lower ・・Cooling gas 1o ・・Arc power supply 11 ・・Arc 12 ・・Non-equilibrium plasma (b) (C) Go- ÷ 1 time gas cooling light arczolazuyanoenoto Principle diagram of CVD method Figure 3 25 Laser 26... Laser beam 27 ・Condensing lens 28... Discharge gas 31・ Plasma 36... ・Ground to be treated 37° High pressure phase BN film 38 Arc

Claims (1)

[Claims] 1. Gas is supplied to a thermal plasma generator, the gas is radicalized by electric discharge to form thermal plasma, and the generated thermal plasma is ejected from a nozzle at the tip of a torch as a plasma jet. Cooling gas is blown onto the jet to rapidly cool the thermal plasma to reduce the concentration of radicals, including at least radical products generated by radicalization of boron compound gas and nitrogen compound gas, which are raw material compounds for vapor phase growth supplied to the plasma jet. High-pressure phase nitriding is characterized by generating a highly active nonequilibrium plasma, bringing a substrate into contact with this nonequilibrium plasma, and growing a boron nitride film on the substrate by thermal plasma chemical vapor deposition (CVD). A method for vapor phase synthesis of boron. 2. Claim 1 in which the thermal plasma generator is a DC plasma torch that radicalizes the supplied gas and generates thermal plasma by direct current arc discharge between an anode and a cathode.
Method described. 3. The method according to claim 1, wherein the thermal plasma generating device is a device that generates thermal plasma by radicalizing the supplied gas by arc discharge using high-frequency induction. 4. The method according to claim 1, wherein the thermal plasma generating device is a device that generates thermal plasma by radicalizing the supplied gas by optical arc discharge using a focused high-power laser beam. 5. The method according to any one of claims 1 to 4, wherein the discharge gas or the cooling gas or both contain hydrogen. 6. The method according to any one of claims 1 to 4, wherein the raw material gas for the raw material compound for vapor phase growth is supplied into the plasma jet as the discharge gas or the cooling gas. 7. Claim 6, wherein the boron compound gas is hydrogen boride.
Method described. 8. The method according to claim 6, wherein the nitrogen compound gas is ammonia. 9. Inert gas such as Ar, He and O_2, H_2O,
5. The method according to claim 1, wherein at least one oxidizing gas such as H_2O_2 is mixed into the discharge gas or the cooling gas or both. 10. The method according to claim 2, wherein a gas containing hydrogen and a gaseous raw material compound is supplied between the electrodes of the thermal plasma generator. 11. The method according to claim 2, wherein a gas containing hydrogen is supplied between the electrodes of a thermal plasma generator having an anode and a cathode, and the gas containing a gaseous raw material compound is supplied to the thermal plasma jet ejected from between the electrodes. . 12. The method according to claim 2, wherein DC arc discharge is performed using a carbon electrode or a tungsten electrode containing a rare earth element oxide as anode and cathode materials. 13. A plasma torch that opens a thermal plasma jet ejection nozzle, turns gas supplied from a discharge gas introduction tube into thermal plasma by discharge, and ejects the generated thermal plasma from the nozzle as a plasma jet; a raw material gas supply system that supplies boron compounds and nitrogen compounds as raw material compounds for vapor phase growth; A cooling gas supply system having a cooling gas outlet disposed close to the nozzle of the plasma torch, which generates an active non-equilibrium plasma with a high radical concentration and containing at least radical products generated by radicalization of a compound. and a substrate support mechanism for supporting a substrate in the non-equilibrium plasma and growing a thermal plasma chemical vapor deposition (CVD) boron nitride film on the substrate in vapor phase. This is a high-pressure boron nitride vapor phase synthesis device.