JPH03197678A - Method for synthesizing cubic boron nitride - Google Patents

Abstract

PURPOSE:To synthesize the cubic boron nitride from an inexpensive boron source with a device of simple structure by using a boron atom-contg. solid and a nitrogen atom-contg. gas as the raw material and depositing cubic boron nitride on the surface of a substrate heated to a specified temp. by a microwave electroless discharge. CONSTITUTION:The substrate 20 consisting of an Si wafer is placed on a susceptor 19 in a reaction chamber 15, and an NaBH4 powder 21 is provided close to the substrate 20. The reaction chamber 1 is evacuated through an exhaust pipe 22, and gaseous NH3 and gaseous N2 are supplied to the reaction chamber 1 respectively from a gaseous NH3 feeder 14 and a gaseous N2 feeder 16 to control the pressure to a specified value. An electroless discharge is then generated in the reaction chamber 1 by a microwave cavity 17 connected to a microwave oscillator 18 to heat the substrate 20 to 300-1300 deg.C, and a film is formed on the surface of the substrate 20. Consequently, excellent c-BN film is synthesized by using the inexpensive and safe raw material and simple reactor under wide synthetic conditions.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for synthesizing cubic boron nitride, which is used as a tool material for cutting tools and the like, and as an electronic material for heat sinks and the like.

[Conventional technology]

Cubic boron nitride (c-BN) has hardness and thermal conductivity second only to diamond, and is extremely chemically stable against iron group alloys, making it suitable for use in improving the durability of cutting tools, molds, etc. Alternatively, a wide range of uses can be considered, such as application to semiconductor devices, light emitting devices, etc.

Conventionally, as a method for synthesizing c-BN using microwaves,
For example, a technique disclosed in Japanese Unexamined Patent Publication No. 62-205277 is known. Such a synthetic method is carried out using a reaction apparatus shown in FIG. 4 or FIG. 5.

In FIGS. 4 and 5, reference numeral 1 indicates a boron atom-containing gas and nitrogen atom-containing gas supply device, which supplies the gases into the reaction chamber 2. In FIG.

Furthermore, a hydrogen gas supply device 3 for supplying hydrogen gas into the reaction chamber 2 is provided separately from the gas supply device 1 . A waveguide 4 is installed outside the reaction chamber 2, and this waveguide 4 is connected to a microwave oscillator 5. On the other hand, a susceptor 6 is installed in the reaction chamber 2, and a substrate 7 is placed on the susceptor 6. Further, an exhaust device 8 that exhausts the inside of the reaction chamber 2 is connected to the reaction chamber 2 . 9 is an exhaust port provided in the exhaust device 8. 10, 11, and 12 each indicate a cock.

In the reaction apparatus shown in FIG. 5, a resistance heating furnace 13 is installed around the outer periphery of the reaction chamber 2. This is because in the reaction apparatus shown in FIG. 5, the substrate 7 is present outside the microwave plasma, so it is provided to heat the substrate 7.

According to the reaction apparatus shown in FIG. 4, all the reaction gases are mixed from each gas supply device 1 and 3, introduced into the reaction chamber 2, passed through a microwave electrodeless discharge, and heated to a temperature of 300 to 1300°C.
C-BN is deposited on the surface of the substrate 7 heated to .

On the other hand, according to the reaction apparatus shown in FIG. 5, first, only hydrogen gas is passed through the microwave electrodeless discharge, and then a boron atom-containing gas and a nitrogen atom-containing gas are mixed to form a reaction chamber 2.
C-BN is introduced into the substrate 7 to deposit C-BN on the surface of the substrate 7.

[Problem to be solved by the invention]

However, in conventional synthesis methods, the concentration and ratio of reactant gases,
The synthesis conditions such as substrate heating temperature and reaction system pressure are narrow, and the reproducibility of the film formation state is poor. Furthermore, films formed by conventional techniques were obtained only as a mixed crystal of cubic and hexagonal crystals, and did not have good performance.

In order to form a c-BN thin film with good reproducibility, it is necessary to use a reactant having a bond close to the SP3 bond of c-BH and having an advantageous structure in terms of energy. Here, when a boron atom-containing gas is used as a boron source, the raw materials are limited, and there are almost no gases that are structurally and energetically advantageous. BCf i BFs+ BBr3
These gases are not common, expensive, and dangerous.

In addition, since boron atom-containing gas is often more easily decomposed than nitrogen atom-containing gas, it is necessary to install a double cylindrical tube in the equipment and introduce the boron atom-containing gas just before the substrate. However, this method had the disadvantage that the structure of the reaction tube was complicated.

The present invention has been made in view of such conventional problems, and uses a boron atom-containing solid as a boron source that is advantageous for cubic crystal formation and is relatively easy to obtain and inexpensive in a chemical vapor deposition method. It is an object of the present invention to provide a method for synthesizing c-BN that can synthesize good c-BN and has a simple structure of a reaction apparatus.

[Means for Solving the Problems] In order to achieve the above object, the present invention uses boron atoms as a raw material in depositing c-BN on the surface of a substrate heated to 300 to 1300°C by microwave electrodeless discharge. A solid containing nitrogen atoms and a gas containing nitrogen atoms were used.

In addition, boron atom-containing solids, nitrogen atom-containing gases, hydrogen gas, or inert gases may be used as raw materials; furthermore, boron atom-containing solids, nitrogen atom-containing gases,
Hydrogen gas and inert gas may also be used.

[For production]

In the method for synthesizing c-BN with the above configuration, a boron atom-containing solid is evaporated by induction heating using microwaves or resistance heating installed independently of a microwave waveguide, and then passed through microwave plasma to bring it into an excited state. A gas containing boron atoms is generated. This is thermally decomposed and reacted with excited nitrogen gas near the heated substrate surface.
Desired c-BN is deposited on a substrate heated to 00 to 1300°C.

In the present invention, since a boron atom-containing solid is used as a boron source, raw material B, which is structurally and energetically advantageous for forming a C-BN film, is 0. and easily available and inexpensive raw material H3BO.
3+ NaB)In can be used for film formation, and film formation with good reproducibility can be realized. Furthermore, since microwave plasma is used as the excitation method, it is possible to generate a large amount of ions that have a high spatial energy density and contribute to the formation of cubic crystals.

(Example) (First Example) Figure 1 shows the reaction apparatus used in this example.
4 indicates N in the reaction chamber 15 of the NHsHe gas supply device.
113 gas. Also, 20N) 13
Separately from the gas supply device 14, N! is supplied into the reaction chamber 15. A microwave cavity 17 is installed around the outer periphery of the reaction chamber 15 in which an N2 gas supply device 16 for supplying gas is provided, and this microwave cavity 17 is connected to a microwave oscillator. On the other hand, a susceptor 19 is installed in the reaction chamber 15, and a substrate 20 made of a Si wafer is placed on the susceptor 19. Furthermore, NaBHa powder (solid containing boron atoms) 21 is provided on the susceptor 19 near the group @20. Reference numeral 22 indicates an exhaust pipe.

c-BNli was formed using a reaction apparatus having such a configuration.

The reaction system is depressurized using an exhaust bag f (not shown), and NH,
The flow rates of gas, N, and gas were 5 cc/win and 100 cc/inch, respectively, and the pressure in the reaction system was 20 T.
orr, an electrodeless discharge was generated using a 2450 MH2 microwave oscillator 18, the temperature of the substrate 20 was raised to 850 to 950°C, and the reaction was continued for 3 hours.

As a result, a 2μ-thick c-BN layer is deposited on the surface of the substrate 200.
IA was deposited.

When this c-BN film was examined by FT-IR (Fourier transform infrared absorption spectrum), it showed remarkable absorption at 101050C', confirming the formation of a c-BN film.

(Second Example) Figure 2 shows the reaction apparatus used in this example.
3 is an H8 gas supply device, and a microwave oscillator 18 is installed in the middle of this H gas introduction system. In addition, near the susceptor 19 in the reaction chamber 15,
t(JOi (solid containing boron atoms)) 24 is provided. A W filament 25 is provided at a position corresponding to the HJOs 24 outside the reaction chamber 15.

Further, an electric furnace 26 is installed around the outer periphery of the reaction chamber 15 so as to surround the substrate 20 .

A c-BN film was formed using a reaction apparatus having such a configuration.

The reaction system is reduced in pressure using an exhaust device (not shown), and then H
, BO, 24 was resistance heated to several hundred degrees with a W filament 25. Then, Ht gas (flow rate 100cc/5in) is excited and decomposed, and this and MHI gas (flow rate 5cc/5i
A mixed gas with n) was introduced onto the substrate 20 which was heated to 850 to 950°C in an electric furnace 26. After 3 hours of film formation, a 2 μm thick c-BN film was formed on the surface of the substrate 200.

When this c-BN film was examined by FT-IR, it was found that 1050
A remarkable absorption was observed at cm-1, and the formation of c-BNW4 was confirmed.

(Third Example) Figure 3 shows the reaction apparatus used in this example.
7 is a He gas supply device. On the substrate 20, B20. Powder (solid containing boron atoms) 28 is uniformly dispersed.

A c-BN film was formed using a reaction apparatus having such a configuration.

The reaction system was reduced in pressure using an exhaust device (not shown), and then N
HK gas (flow rate 5cc/win) and He gas (flow rate 1
00 cc/win) is flowed into the reaction system, microwaves are oscillated near the substrate 20, and the reactants are excited, decomposed, and reacted by electrodeless discharge.
The substrate 20 was heated by induction. As a result of film formation for 3 hours, c-BN with a thickness of 1.5 μm was deposited on the surface of the substrate 20.

When I checked this with FT-IR, it was 1050c++-
', and the formation of c-BNII@ was confirmed.

〔Effect of the invention〕

As described above, according to the c-BN synthesis method of the present invention,
Until now, it was under ultra-high pressure like diamond.

c-BN, which could only be created at high temperatures,
It can be successfully synthesized using inexpensive and safe materials under a wide range of synthesis conditions, and the structure of the reactor can be simplified.

[Brief explanation of drawings]

1 to 3 are c-BNs according to the present invention, respectively.
FIGS. 4 and 5 are schematic diagrams showing the reaction apparatuses used in the first to third examples of the synthesis method, and FIGS. 4 and 5 are schematic diagrams showing the reaction apparatuses used in the conventional method, respectively. 14...NH3 gas supply device 15...Reaction chamber 16...N2 gas supply device 18...Microwave oscillator 20...Substrate 21-NaB)In powder 23...H Yogas supply device 24. ...)lsBOs 26...Electric furnace 27...He gas supply device 28...B20. powder

Claims (4)

[Claims] (1) Using a boron atom-containing solid and a nitrogen atom-containing gas as raw materials, 300~
A method for synthesizing cubic boron nitride, which comprises depositing cubic boron nitride on the surface of a substrate heated to 1300°C. (2) Cubic boron nitride is deposited on a substrate surface heated to 300 to 1300°C by microwave electrodeless discharge using a boron atom-containing solid, a nitrogen atom-containing gas, and hydrogen gas as raw materials. Synthesis method of crystalline boron nitride. (3) Using a boron atom-containing solid, a nitrogen atom-containing gas, and an inert gas as raw materials, cubic boron nitride is deposited on a substrate surface heated to 300 to 1300°C by microwave electrodeless discharge. Synthesis method of cubic boron nitride. (4) Using a boron atom-containing solid, a nitrogen atom-containing gas, hydrogen gas, and an inert gas as raw materials, cubic boron nitride is deposited on a substrate surface heated to 300 to 1300°C by microwave electrodeless discharge. Characteristic method for synthesizing cubic boron nitride.