JPH04314865A - Method for synthesizing cubic boron nitride - Google Patents

Abstract

PURPOSE:To selectively remove hexagonal BN and amorphous BN by etching and to form a cubic BN film on the surface of a substrate. CONSTITUTION:Gaseous BCl3 2 and gaseous N2 3 as gaseous starting materials are mixed with gaseous H2 4 as assist gas, irradiated with UV light from excimer laser 8 as a light source and passed through a thermoelectron radiating material 11 set near a substrate 1. A cubic BN film is formed on the surface of the substrate 1 heated to 300-1300 deg.C.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for synthesizing cubic boron nitride, which can be used as tool materials such as cutting tools and electronic materials such as heat sinks.

0002

[Prior Art] Cubic boron nitride (c-BN) has hardness and thermal conductivity second only to diamond, is extremely chemically stable to iron group alloys, and is durable for cutting tools, molds, etc. A wide range of applications can be considered, including applications to improve performance, semiconductor devices, light emitting devices, etc.

Conventionally, cubic boron nitride (c-
The method for synthesizing BN) is described in Japanese Patent Application Laid-Open No. 63-134662
As disclosed in the publication, a boron atom-containing gas and a nitrogen atom-containing gas are decomposed and excited by an excimer laser, and then passed through a high-frequency plasma to
A method is known in which c-BN is introduced onto the surface of a substrate heated to 00° C. to precipitate c-BN. Furthermore, a method is disclosed in which the ratio of the number of boron atoms in the boron atom-containing gas to the number of nitrogen atoms in the nitrogen atom-containing gas is set in a range of B/N=0.1 to 10, and no hydrogen is used as the reaction gas.

[0004] Furthermore, as a method for synthesizing cubic boron nitride using a thermionic emitting material, as disclosed in JP-A-60-277766, a boron atom-containing gas and a nitrogen atom-containing gas are reacted separately. Introduced into the system, only the nitrogen atom-containing gas is passed through a microwave non-polar discharge, mixed with a boron atom-containing gas, and then passed through a thermionic emissive material that has been heated to over 1000°C. let, 300~20
A method is known in which c-BN is introduced onto the surface of a substrate heated to 00° C. to precipitate c-BN. Further, a method is disclosed in which the ratio B/N of the number of boron atoms in the boron atom-containing gas to the number of nitrogen atoms in the nitrogen atom-containing gas is in the range of 0.0001 to 10,000.

[0005]

[Problems to be Solved by the Invention] Generally, on a substrate heated to a high temperature, when only the raw material gas is introduced, c-B
Along with the N structure, h-BN and a-BN structures are formed. For this reason, hydrogen gas or inert gas is mixed into the raw material gas for the purpose of selectively etching away BN structures other than the c-BN structure.

However, the conventional method disclosed in JP-A-60-134662 does not mix hydrogen gas or inert gas into the raw material gas, so there is a problem that it is difficult to obtain the desired structure consisting only of c-BN. Ta. Furthermore, with conventional excitation methods, even when hydrogen gas or inert gas is mixed, it is difficult to generate active species such as atomic hydrogen, which is said to contribute to the selective formation of c-BN structures. there were.

On the other hand, even in the conventional method disclosed in JP-A No. 60-277766, which is a synthesis method using a thermionic emitting material, hydrogen gas or inert gas is not mixed into the raw material gas; There were problems similar to the method in the publication.

The present invention has been made in view of the above-mentioned conventional problems, and it is an object of the present invention to provide a method for synthesizing c-BN which is advantageous for c-BN formation in a vapor phase chemical precipitation method.

[0009]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a method for synthesizing cubic boron nitride by a vapor phase chemical vapor deposition method using a boron atom-containing gas and a nitrogen atom-containing gas as material gases. , mixing at least one of hydrogen or an inert gas into the raw material gas,
We decided to irradiate ultraviolet light from an excimer laser or low-pressure mercury lamp, and then pass it through a thermionic emitter placed near the substrate, forming a cubic boron nitride film on the substrate surface heated to 300 to 1300 degrees Celsius. .

Further, in the present invention, hydrogen and an inert gas are passed through the thermionic emitting material, and then introduced into the chamber together with the source gas and irradiated with the ultraviolet light to form a cubic boron nitride film on the surface of the substrate. may be formed.

[0011]

[Operation] In the present invention, a boron atom-containing gas and a nitrogen atom-containing gas are used as raw material gases, and hydrogen or an inert gas is mixed therein. These gases are excited when exposed to ultraviolet light and diffuse into the vicinity of the substrate as active species, mainly radicals. After that, the thermionic emitter placed just in front of the substrate further decomposes it into active species of ions, resulting in 300 ~
An active reaction occurs near the surface of the substrate heated to a high temperature of 1300° C., and highly crystalline cubic boron nitride is precipitated on the substrate.

A feature of the present invention is that ultraviolet light is irradiated with an excimer laser or a low-pressure mercury lamp, and activation is performed with a thermionic emitter.

It is known that the generation of active species such as atomic hydrogen and nitrogen molecular ions is essential for the formation of the c-BN structure. Therefore, the present invention uses a combination of activation means that have relatively different properties, ie, radical generation by ultraviolet light irradiation and ion generation by a thermionic emitting material, thereby eliminating the need for precursors that can form the desired film. ,
It is selectively generated at a high concentration and favors the formation of c-BN. In particular, it is known that atomic hydrogen is generated at a high concentration by thermionic emitting materials, and interaction with active species excited by ultraviolet light is effective in forming only the c-BN structure.

As described above, since the present invention uses a combination of excitation means that are relatively different in the state of the active species, the amount of each active species produced can be controlled by adjusting the power of the light source and the current of the electron emitting material. It is possible to set the optimum conditions for the c-BN film. Therefore, the desired composition, that is, the desired B/
Cubic boron nitride with an N ratio can be produced.

[0015]

Example 1 A c-BN film was formed using the synthesis apparatus shown in FIG. A silicon wafer was used as the substrate 1, BCl3 gas 2 and N2 gas 3 were used as source gases, and H2 gas 4 was used as the assistant gas. The substrate 1 was placed on the susceptor 5, and the pressure inside the chamber 7 was reduced by the exhaust system 6.

BCl3 gas 2, N2 gas 3 and H2 gas 4 were supplied in advance at 1 cc/min and 1 cc/min, respectively.
The mixture was mixed at a flow rate of 0 cc/min and 100 cc/min, introduced into the chamber 7, irradiated with ultraviolet light through a quartz window 9 by an excimer laser 8 provided outside the chamber 7, and then placed directly above the substrate 1. The portion of the thermionic emitting material 11 that had been heated was allowed to pass through. The pressure inside the chamber 7 was 15 Torr, and the temperature of the substrate 1 was set to 900° C. by a heater 13 connected to a DC power source 12. Then, the reaction was carried out for 2 hours, and a film having a thickness of 1 μm was formed on the surface of the substrate 1. Note that 14 in the figure is a DC power supply connected to the thermionic radiation material 11.

When this film was examined by FT-IR (Fourier transform infrared absorption spectrum), it showed significant absorption at 1050 cm-1. Thereby, formation of the c-BN film could be confirmed.

[0018]

Example 2 A c-BN film was formed in the same manner as in Example 1 using the synthesis apparatus shown in FIG. A silicon wafer is used as the substrate 1, and BCl3 gas 2, N as the raw material gas.
H3 gas 15 and Ar gas 16 were used as assist gas. The substrate 1 was placed on the susceptor 5, and the pressure inside the chamber 7 was reduced by the exhaust system 6.

BCl3 gas 2 was introduced into the chamber 7 at a flow rate of 2 cc/min, and ultraviolet light was irradiated through the quartz window 9 by a low-pressure mercury lamp 17 provided outside the chamber 7. On the other hand, NH3 gas 15, Ar
Gas 16 at 2cc/min and 50cc/mi respectively
The thermionic emissive material 1 in the chamber 7 is mixed at a flow rate of n.
It was introduced just before 1. Then, BC was irradiated with ultraviolet light.
13 gas 2, NH3 gas 15, and Ar gas 16 were mixed in the chamber 7 and passed through the thermionic emitter 11 placed directly above the substrate 1. The pressure inside the chamber 7 was 10 Torr, the temperature of the substrate 1 was 900° C., and the region where the above gases were mixed was heated to 200 to 300° C. using a heating furnace 18 provided outside the chamber 7. Then, after reacting for 2 hours, 1
．． A film with a thickness of 5 μm was formed.

[0020] When this film was examined by FT-IR, it was found that 10
Remarkable absorption was observed at 50 cm −1 , confirming the formation of a c-BN film.

[0021]

Example 3 A c-BN film was formed in the same manner as in Example 1 using the synthesis apparatus shown in FIG. A silicon wafer is used as the substrate 1, and B2H6 gas 20 is used as the raw material gas.
, NH3 gas 15, H2 gas 4 as assist gas
was used. The substrate 1 was placed on the susceptor 5, and the pressure inside the chamber 7 was reduced by the exhaust system 6.

[0022] B2 H6 gas 20, NH3
Gases 15 were mixed together at a flow rate of 1 cc/min and introduced into the chamber 7, and ultraviolet light was irradiated through the quartz window 9 by an excimer laser 8 provided outside the chamber 7. On the other hand, the flow rate of H2 gas 4 was set to 100cc/min.
The sample was introduced into the chamber 7 by passing through the thermionic emitting material 11 in advance. The pressure inside chamber 7 is 2
The temperature of the substrate 1 was 850° C. at 0 Torr. Then, the reaction was carried out for 1 hour, and a film having a thickness of 1 μm was formed on the surface of the substrate 1.

When this film was examined by FT-IR, it was found that 10
Remarkable absorption was observed at 50 cm −1 , and formation of a c-BN film could be confirmed.

[0024]

As described above, according to the c-BN synthesis method of the present invention, hydrogen or an inert gas is mixed into the raw material gas, irradiated with ultraviolet light, and passed through a thermionic emitting material. Since we decided to use a combination of activation means with different comparative properties, radical generation and ion generation, c
- A BN film can be selectively formed.

Furthermore, by adjusting the power of the light source and the current of the electron emitting material, a cubic boron nitride film having a desired B/N ratio can be produced.

[0026] Therefore, cubic boron nitride films, which could previously only be synthesized under ultra-high pressure and high temperature like diamond, can be artificially synthesized into thin films using inexpensive equipment and materials.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration of a synthesis apparatus used in Example 1 of the present invention.

FIG. 2 is a schematic configuration diagram of a synthesis apparatus used in Example 2 of the present invention.

FIG. 3 is a schematic configuration diagram of a synthesis apparatus used in Example 3 of the present invention.

[Explanation of symbols]

1 Board 2 BCl3 gas 3 N2 gas 4 H2 gas 7 Chamber 8 Excimer laser 11 Thermionic emissive material 15 NH3 gas 16 Ar gas 17 Low pressure mercury lamp 20 B2 H6 gas

Claims (2)

[Claims] 1. A method for synthesizing cubic boron nitride by a vapor phase chemical vapor deposition method using a boron atom-containing gas and a nitrogen atom-containing gas as source gases, wherein the source gas is at least one of hydrogen or an inert gas. is mixed with ultraviolet light from an excimer laser or a low-pressure mercury lamp as a light source, and then passed through a thermionic emitter placed near the substrate to form a cubic boron nitride film on the substrate surface heated to 300 to 1300°C. A method for synthesizing cubic boron nitride, characterized by forming cubic boron nitride. 2. Forming a cubic boron nitride film on the surface of the substrate by passing hydrogen and an inert gas through a thermionic emitting material, and then introducing the material into a chamber together with the source gas and irradiating the ultraviolet light. A method for synthesizing cubic boron nitride according to claim 1.