JPS62243770A - Method for synthesizing high hardness boron nitride - Google Patents

Abstract

PURPOSE:To stably produce and deposit high hardness cubic boron nitride by irradiating excimer laser light on a gaseous starting material to decompose the starting material and by bringing the resulting excited boron and nitrogen atoms into a reaction on a heated substrate. CONSTITUTION:A reaction chamber 5 is evacuated and a gaseous starting material contg. boron and nitrogen atoms is introduced into the chamber 5 from a gas feeding system 3 through a gas feeding pipe 4. A substrate 8 is heated to about 300-2,000 deg.C with a heater 7 and then laser light is introduced into the chamber 5 from excimer laser device 1 through the window 2 to decompose the gaseous starting material. The resulting excited boron and nitrogen atoms are brought into a reaction on the substrate 8 to produce and deposit a cubic boron nitride film. By this method, high hardness boron nitride giving a high quality film of a uniform thickness can be synthesized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a novel method for synthesizing high-hardness boron nitride, in which cubic boron nitride is deposited on the surface of a substrate from a gas phase. Cubic boron nitride is not only extremely hard, but also highly thermally conductive, chemically stable, and unlike diamond, has excellent resistance to iron group metals, making it useful for example in cutting tools and wear-resistant materials. It is extremely suitable for use as tool materials such as tools, and furthermore as electronic materials such as heat sinks.

[Conventional technology]

As methods for synthesizing cubic boron nitride from the gas phase, there are, for example, the following three known techniques.

1. Described in Japanese Patent Publication No. 6G-181262,
Boron is evaporated onto the substrate from an evaporation source containing boron, and the substrate is irradiated with ion species containing at least nitrogen from an ion generation source to generate boron nitride on the substrate. Method for manufacturing crystalline boron nitride film.

2.H! A method for producing cubic boron nitride on a substrate by chemically transporting boron using +N-rich plasma [Reference 1: Komatsu et al., Journal on Materials Science Letters, Journal of Ma
terials 5ciance letters, 4(
19E15) p, 51-54].

5 HCD, (Hol'low Cathode Di
While evaporating boron with a charge (hollow cathode discharge) gun, N2 is ionized from the hollow cathode and radiated onto the substrate, a high frequency is applied to the substrate to create a self-bias effect, and cubic nitriding is performed on the substrate. Method for producing boron [Reference 2: Inagawa et al., Flossiedinges on 9th Symposium on Io/Source
Io, Assisted Chikunoroshii, Proceed
ingaof 9th 87mp081um Onko
n 5source IonAsgigted Tech
nology, 'B5, Tokyo, p-29
9-302. (1985)].

[Problem that the invention seeks to solve]

However, method 1 has the disadvantage that the ion generator and focusing device are expensive. Said 2
Since the method uses high-power RF plasma for film formation, it has the disadvantage that impurities from the reaction system are likely to be mixed in. Like method 1, method 3 has the drawback that the ion beam generator and focusing device are expensive, and in addition, atoms of the inert gas are incorporated into the deposited boron nitride.

The present invention eliminates the drawbacks of these conventional methods and enables the production and production of highly pure cubic boron nitride on the surface of a substrate using less expensive equipment.
This study aims to develop a new method for synthesizing high-hardness boron nitride that can be precipitated.

[Means for solving problems]

The present inventors decomposed and excited the raw material gas by using an excimer laser with high output in the short wavelength region, and by heating the substrate, we created cubic crystals from the gas phase on the substrate. We came up with the idea of precipitating boron nitride and arrived at the present invention.

That is, the present invention irradiates a raw material gas consisting of a boron atom-containing gas and a nitrogen atom-containing gas with excimer laser light to bring it into a decomposed and excited state, and causes the gas to react on the heated substrate surface, thereby causing the substrate to react. This is a method for synthesizing high hardness boron nitride, which is characterized by precipitating cubic boron nitride on the surface.

A particularly preferred embodiment of the present invention includes the above method, wherein 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 [11≦B/N≦10; The above-mentioned method includes irradiating the substrate with excimer laser light in parallel.

Hereinafter, the present invention will be specifically explained with reference to the drawings. 1st
The figure is a diagram illustrating an embodiment of the present invention, and shows a reaction chamber 5.
The atmosphere inside is exhausted by the exhaust pump 11 and the exhaust port 12], and the boron atom-containing gas and the nitrogen atom-containing gas, which are raw material gases, are passed from the gas supply system 3 through the raw material gas supply pipe 4,
into the reaction chamber 5. A substrate 8 is placed on a substrate support stand 6 in the reaction chamber 5 . The substrate 8 is the heater 7
is heated to a temperature in the range of 300 to 2000C. In such a state, the excimer laser device 1,
When a laser beam is introduced into the reaction chamber 5 through the laser beam introduction window 2, the source gas is decomposed to produce excited boron atoms and nitrogen atoms, and cubic nitride atoms are deposited on the heated substrate 8. An elementary film is deposited.

Note that instead of heating with a heater, as shown in FIG.
It may also be introduced into the reaction chamber through the reactor and heated. In FIG. 2, the meanings of numbers 1 to 6 and 8 are the same as in FIG.

Examples of the boron atom-containing raw material gas used in the present invention include BIB@, BCl2 g BBrs.

Examples include BIN3H@. Further, examples of the nitrogen atom-containing gas include N! , MHI, etc.

In the present invention, an excimer laser is applied to the boron atom-containing gas and the nitrogen atom-containing gas as described above to decompose the raw material gas and generate excited boron atoms and nitrogen atoms.

Excimer lasers have an oscillation wavelength in the short wavelength (ultraviolet) region of 2 dOnm to 400 nm. Since the light energy E is expressed by the formula: E=h - λ (h is a blank constant, C: speed of light, λ: wavelength), the photon energy of an excimer laser is large. For example, the photon energy of ArF laser, which is a type of excimer laser, is 147.2 Kcal/mob.
In contrast, C has high output in the infrared region with longer wavelengths.
O! The photon energy of the laser is 2.7 Kcal/m
Very close to ob.

Therefore, an excimer laser has a greater power to break intermolecular bonds with a single photon than a CO laser.

The output of the excimer laser used in the present invention is 1 to 1
A range of 00W is preferred. If the output is less than 1 W, the film formation rate will be very low and the time required for film formation will be long. Furthermore, if the output is greater than 100 W, the lifetime of the medium gas will be shortened, so the output attenuation will be significant and it will be difficult to obtain a stable output. Excimer laser used in the present invention
Examples of the medium gas include ArF and KrF.

IP! Examples include gas.

Note that the direction of incidence of the laser is preferably parallel to the substrate as shown in FIG. 1 or 2. This is to prevent the laser from entering the substrate and damaging the substrate.

Excited boron atoms and nitrogen atoms generated by the excimer laser beam incidence form sp" bonds with each other with the help of thermal energy from the heated substrate, and cubic boron nitride is precipitated on the substrate. The substrate temperature at this time is 50
A range of 0 to 2000°C is preferred. This is because if the substrate temperature is less than 300° C., there is insufficient thermal energy to form an sps bond, and if it exceeds 2000° C., the formed boron nitride film will decompose and nitrogen will be extracted.

Further, in the present invention, 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 B /
M is preferably in the range α1≦B/N≦10. B/
This is because if N (α1), an amorphous boron nitride film is likely to precipitate, and if B/N>10, boron becomes excessive and amorphous boron is likely to be formed.

Note that the present invention does not require the presence of hydrogen gas.

The presence of hydrogen gas causes hydrogen to enter the El 8P' bonds of the 0BII (cubic boron nitride) film and inhibit the formation of cI3N, since B-H bonds are easier to bond than B-M bonds. However, the present invention is advantageous in that K c BN can be produced without requiring such hydrogen gas.

The substrate used in the present invention is not particularly limited, and includes, for example, a silicon substrate, a molybdenum substrate,
Various types of substrates can be used, including alloy substrates other than WCC cemented carbide.

Since the present invention uses a laser beam whose power remains constant once it oscillates as a film forming means, plasma O'V
Compared to methods such as D method, which are susceptible to external influences such as pressure and earth matching, it is possible to form a film very stably. In addition, as the laser beam, we use an excimer laser with a large photon energy, so
Does not require high power like CO, laser, 1~100W
Cubic boron nitride can be produced at such low output. Therefore, it is possible to extend the life of the device.

[Implementation ff1J] Example 1 According to the configuration shown in FIG. 1, a silicon wafer was used as the substrate, and 1 cc/mtn of diborane was used as the reaction raw material gas.
and nitrogen 4/win, and the pressure inside the reaction tube was Q,
I Torr was adjusted, and the substrate temperature was 800°C. As the excimer laser, a MurF' laser was used and the reaction was continued for 3 hours at an output of 10 W. As a result, a boron nitride film with a thickness of approximately (18 μm) was formed on the substrate surface.

When the obtained boron nitride film was subjected to X-ray diffraction using 0uKa rays, a (1,1,1) peak was detected near 2θ of 43°, which identified the film as cubic boron nitride. did it.

Example 2 According to the configuration shown in Fig. 1, a molybdenum substrate was used as the substrate, diborane 1 cc/min and nitrogen 4 cc/min were flowed as reaction raw material gases, and the pressure inside the reaction tube was [12T].
orr, and the substrate temperature was set to 1000°C. An ArF laser is used as the excimer laser, with an output of 1
When the reaction was continued for 4 hours at 5W, a boron nitride film with a thickness of about 1-1 was formed on the substrate surface.

When the obtained boron nitride film was subjected to X-ray diffraction, a (1,1,1) peak was detected as in Example 1, and it was identified as cubic boron nitride.

Example 5 According to the configuration shown in Fig. 2, a molybdenum substrate was used as the substrate, BCI, 5 CC/ml, and NH 35 cc/min were flowed as the reaction raw material gas, and the reaction tube internal pressure was αI.
Torr, and the infrared lamp intensity was adjusted so that the substrate temperature was 900°C. When a dirF laser was used as an excimer laser and the reaction was continued for 3 hours at an output of 20 W, a boron nitride film with a thickness of about 0.9 μm was formed on the substrate surface. The film was subjected to X-ray diffraction (1, 1, 1
) was detected, and it was identified as 9-cubic boron nitride.

Since cubic boron nitride could be obtained under the above implementation conditions, a chip was coated with it, and a cutting test was conducted on the resulting cubic boron 11-decide coated chip. Also, for comparison,
Aj! by uncoated chip and OVD method! O
, Cutting tests were also conducted on the coated chips.

The material of the chip is WCC cemented carbide.
A cutting tip of TNMG 532 (M-10 grade) was used, and the thickness of the coating layer was 3 μm in all cases.

The cutting test conditions are summarized in Table 1, and the results are summarized in Table 2.

From the results in Table 2, it can be seen that when the cubic boron nitride produced according to the present invention is used as a coating layer in a cutting tip, it has very excellent wear resistance.

Table 1 Table 2 [Effects of the Invention] As explained above, the present invention uses an excimer laser with high photon energy to stably produce cubic boron nitride at low output without requiring hydrogen gas, resulting in high quality. Thus, cubic boron nitride having a uniform film thickness can be obtained with lower equipment costs and production costs than conventional methods. Further, since the output of the laser beam is stable regardless of external influences, it is advantageous that various heating and excitation means can be selected.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating an embodiment of the present invention, and is a schematic cross-sectional view showing an example of heating with a heater. FIG. 2 is a schematic cross-sectional view showing another embodiment M of the present invention, in which heating is performed using infrared rays.

Claims (3)

[Claims] (1) A raw material gas consisting of a boron atom-containing gas and a nitrogen atom-containing gas is irradiated with an excimer laser beam to bring it into a decomposed and excited state, and the gas is reacted on the heated substrate surface,
A method for synthesizing high hardness boron nitride, which comprises depositing cubic boron nitride on the surface of the substrate. (2) 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 0.1≦B/
The method for synthesizing high hardness boron nitride according to claim (1), wherein N≦10. (3) The method for synthesizing high hardness boron nitride according to claim (1), wherein the excimer laser beam is irradiated parallel to the substrate.