JPS63199872A - Method for synthesizing high hardness boron nitride - Google Patents

Abstract

PURPOSE:To deposit high hardness cubic boron nitride from a vapor phase by leading a preheated gaseous mixture contg. B and N to the surface of a substrate after passing through DC discharge. CONSTITUTION:A gaseous mixture of a B-contg. gas with an N-contg. gas is fed to a reaction chamber 6 and excited by preheating with a thermoelectron radiating material 7. The excited gaseous mixture is passed through the space between DC discharge electrodes 10, 10' to form cubic boron nitride on a heated substrate 9.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention not only has extremely high hardness, but also has excellent thermal conductivity, is chemically stable, and, unlike diamond, has resistance to iron group metals. The present invention relates to a method for depositing cubic boron nitride, which is used as tool materials such as cutting tools and wear-resistant tools, as well as electronic materials such as heat sinks, on the surface of a dielectric substrate in a vapor phase because of its excellent properties.

[Conventional technology]

Conventionally, methods for producing cubic boron nitride have been known, such as the following methods (1) to (2).

As shown in Japanese Patent Publication No. 181262, a boron component is evaporated onto a substrate from an evaporation source containing boron, and the ion fik is deposited onto the substrate from an ion source that generates ionic species containing at least nitrogen. A method for producing a boron nitride film, the method comprising: irradiating the substrate to produce boron nitride on the substrate.

■ “Journal of Materials Science Letters”
lanoe 1etters), , a(19a5
) 51, page N54, a method of producing cubic boron nitride by chemically transporting boron using H2+N2 plasma.

■ [9th Ion Engineering (Ion 8ouroa Io
As shown in the proceedings of the nAgilated Technology Symposium (Tokyo, 1985), ``Ion Sources and Ion-Based Application Technologies'', HOD
N from the hollow anode while vaporizing the boron with a gun.
2 is ionized and radiated to the substrate, and a high frequency is applied to the substrate to eliminate the self-bias effect and generate cubic boron nitride.

■ [Leakage; “Vacuum” Vol. 28 No. 7 (1985) 2
As shown in [pages 9 to 34], boron is evaporated by applying an electron beam (ES) to a solid containing boron atoms, and a gas containing nitrogen atoms is poured into it to simultaneously ionize boron and nitrogen. A method of producing cubic boron nitride on the substrate surface.

[Problem that the invention seeks to solve]

However, method (1) has a disadvantage that the ion beam generating device and its focusing device are expensive.

The above method (■) uses high-output R? Since it is used for plasma gold deposition, impurities from the reaction system are likely to mix in.

The method (2) has the same disadvantages as the method (2) in that the ion beam generating device and its focusing device are expensive, and the atoms of the inert gas are incorporated into the precipitated cubic boron nitride.

In the method (2) above, since boron has a relatively low melting point, boron tends to cause bumping, and therefore it is difficult to control the film thickness using KB.

As mentioned above, all methods (1) to (2) have various drawbacks.

The present invention was developed in view of the current situation, and is a method of depositing cubic boron nitride from the gas phase, which has excellent thermal shock resistance, thermal conductivity ratio, hardness, wear resistance, and resistance to iron group metals at high temperatures. The purpose of this study is to propose a new synthetic method that can

[A precautionary measure to resolve the problem]

In synthesizing high-strength cubic boron nitride, the present inventors have conducted extensive research into ways to provide energy to bring boron and nitrogen into an excited state sufficient to form sp5 bonds with each other. It has been found that a method that uses two excitation means together, heating with a material or the like and direct current plasma discharge, is suitable.

The present invention relates to a method for synthesizing boron nitride by chemical vapor deposition, in which a mixed gas consisting of a boron atom-containing gas and a nitrogen atom-containing gas is preheated with a thermionic emitter and then passed through a pressure and direct current discharge. This is a method for synthesizing high-hardness boron nitride, which is characterized in that it is introduced onto the surface of a heated substrate to cause thermal decomposition and reaction, thereby precipitating high-hardness boron nitride.

In the present invention, the ratio a/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
It is preferable to carry out the heating in the range of 0.0 CI O1 to 10,000, and to carry out the preheating with a thermionic emitting material having a temperature of 10,000 or more, since particularly good results can be obtained.

This will be explained below with reference to the drawings. FIG. 1 is a schematic sectional view showing an embodiment of the present invention, in which the boron atom-containing gas and the nitrogen atom-containing gas supplied from the boron atom-containing gas supply device 1 and the nitrogen atom-containing gas supply device 2 are mixed. The mixed gas is supplied to the reaction chamber 6 as a mixed gas. A carrier gas from the carrier gas supply device 3 may be mixed with this mixed gas. By first passing this mixed gas through the heated thermionic emitter 7, excited boron atom-containing gas and nitrogen atom-containing gas are generated in the mixed gas. By passing the mixed gas thus formed through the DC discharge electrodes 10 and 10', the mixed gas is decomposed and excited, and Sp bonds are generated with each other on the substrate 9 heated by the heater 8. Cubic boron nitride can be produced on the substrate surface. Note that the first
In the figure, 4 is a filament power supply, 5 is a heater power supply, 1
1 is a DC power supply, 12 is a cock, 13 is an exhaust device, and 14 is an exhaust port. The temperature of the thermionic emission material used for preheating is preferably 1ooot:' or more in order to excite the source gas. The upper limit is 25 due to the high temperature resistance of the material.
Can be used up to about 00C. Examples of thermionic emitting materials include tungsten filaments, thorium-containing tungsten filaments, and tantalum filaments that can withstand high temperatures.

In the present invention, direct current plasma discharge is used as a total film forming means, but this method easily generates discharge and does not require combining the input wave and reflected wave unlike high frequency or microwave. This is because it has the advantage of not disappearing.

The DC discharge output is preferably 100W or more and 600W or less. If the output is less than 100 W, it is not preferable because there is insufficient energy to decompose and excite the boron atom-containing gas and the nitrogen atom-containing gas, which are the raw material gases.

In the present invention, the ratio B/N of the number of boron atoms in the boron atom-containing gas and the number of nitrogen atoms in the nitrogen atom-containing gas, which is the raw material gas, is preferably in the range of 0.0001 to 10,000. When B/N is less than 0.0001, amorphous boron nitride is likely to precipitate <, B/N is 10000
If this value is exceeded, boron becomes excessive and amorphous boron is likely to be formed. Furthermore, not only a boron atom-containing gas and a nitrogen-containing gas, but also hydrogen gas, argon gas, and the like may be used as all carrier gases.

When hydrogen gas is used as a carrier gas, H in the excited or atomic state reacts with nuclei with Sp and sp2 hybrid orbitals, which are responsible for the growth of non-cubic boron nitride, converting them into Sp bonds. It promotes the production of cubic boron nitride, or produces boron hydride or hydrogen nitride, and plays a cleaning role in the production of high hardness boron nitride.

The reaction system pressure is 0.001 to maintain DC discharge stability.
A range of ˜400 Torr is preferred.

Examples of raw material gases used in the present invention include B2H6, B
Examples of the nitrogen atom-containing gas include N2. Examples include NH3.

In the present invention, the temperature of the substrate is preferably adjusted to 300 to 2000C.

〔Example〕

Examples 1.2 and Comparative Example 1 described below were carried out using the apparatus having the configuration shown in FIG.

Example 1 Using a C-SZ substrate as a substrate, a boron nitride film was synthesized and coated according to the present invention. B2H6 as raw material gas
, N2. N2'it: 10 cc/mln each
.

A flow rate of 10 cc/mzn and 100 cc/ml was adjusted to adjust the pressure inside the reaction tube to I Torr, and the reaction was carried out for 4 hours under the conditions of a DC glazma discharge output of 500 W, a substrate temperature of 1000 G, and a preheated tungsten filament temperature of 2000 C. As a result, a thickness of 8 μm was formed on the surface of the substrate.
A certain amount of boron nitride film was deposited.

As a result of using X-ray diffraction as a means of evaluating this film, 21
A sharp peak was detected near F=43.2°, and it was identified as cubic boron nitride. This proves that cubic boron nitride can be successfully synthesized by the method of the present invention.

Example 2 Using a quartz plate as a substrate, a boron nitride film was synthesized and coated according to the present invention. BBr3. NH5,
N2 at 8 cc/m1n and 20 cc/m1n, respectively
mxn, 50 cc/m1n flowed. The pressure inside the reaction tube was adjusted to TOrr K, and the DC plasma discharge output was 6.
The reaction was carried out for 3 hours under the conditions of 00W, substrate temperature of 900C, and tantalum filament temperature of 2300C.

As a result, a boron nitride film with a thickness of 7 μm and a thickness of 8 degrees was deposited on the surface of the substrate.

As a result of evaluating this film by Raman analysis, it was found that 1055Cr
Sharp peaks were detected near -1 and 1310 ff1-', and it was identified as cubic boron nitride.

Comparative Example 1 An O-31 substrate was used as the substrate, and a boron nitride film coating was performed according to the method of the present invention except that the raw material gas was not passed through the DC plasma discharge. B2H6, N2. 15cc/m of N2 each:
cn, 10cc/m1n, 100cc/m1n
It flowed. The pressure inside the reaction tube was adjusted to 5 Torr, and the reaction was carried out for 5 hours at a tantalum filament temperature of 2200C. As a result, a boron nitride film with a thickness of about 6 μm was deposited on the surface of the substrate.

As a result of evaluating this film by X-ray diffraction, peaks were detected near 2a=26.7° and 45.2°, and it was identified that cubic boron nitride and hexagonal boron nitride were present together.

Performance Evaluation Test 1 Since boron nitride films could not be synthesized under the above conditions of Example 1.2 and Comparative Example 10, a cemented carbide chip product was coated using these conditions, and the resulting Cutting tests were conducted on the coated chips. Comparative tests were also conducted on chips without lick coating and chips coated with TICf using the OVD method. The chip used is 5NGN120408
(Wc-based cemented carbide, the thickness of the coating layer is uniformly 2 μm. The cutting test conditions are as shown below.

Cutting speed: 300 m/m1n feed, j): 0.2 tm/ray Depth of cut: o, 3111 Rigid material: 5KD11 The results of the cutting test are as shown in Table 1, and from this data, boron nitride The coated chips (A1 to Ya3) are superior to the uncoated chips (A5) and those made by the OVD method (Ban 4), but especially the cubic boron nitride of the present invention that does not contain hexagonal boron nitride. Chip with coating layer (A
It can be seen that Samples I and 2) have extremely excellent wear resistance.

Table 1 Note 1) OBN: Cubic boron nitride Note 2) hBN: Hexagonal boron nitride Performance evaluation test 2 (cutting performance in cast iron turning) TNMG
322 (spheroidal graphite cast iron) chip coated with a cubic boron nitride film of 3 μm according to the present invention (Al, by CVN method). 0), cut the rigid material FOD50? and cut the cutting speed (m
/mln) and lifetime time (mln) was investigated. The results are as shown in the graph of FIG. 2, and it can be seen that the coating according to the present invention is very superior.

Evaluation test 3 (cutting performance in steel turning) TNMG331
The chips were coated with the cubic boron nitride film of the present invention (DJ, those coated with pTIN II by the cvp method (E), and the chips as they were without coating (Fl), the work material was 50M435. (chromium molybdenum steel),
Cutting speed 250m/mzn, feed 0.3w/rev,
The relationship between cutting time and flank wear amount was investigated under the condition of a depth of cut of 0.21. The results are shown in FIG. 5, and it is clear that (D) of the present invention is extremely superior.

〔Effect of the invention〕

As explained above, the present invention is a novel method for precipitating cubic boron nitride from the gas phase, which has excellent thermal shock resistance, thermal conductivity, hardness, wear resistance, and resistance to iron group metals at high temperatures. .

[Brief explanation of the drawing]

FIG. 1 is a sectional view schematically explaining an embodiment of the present invention. Figure 2 shows the cutting performance of the inventive product and comparative product in cast iron turning in terms of cutting speed (m/mln) and life time (min).
Figure 3 is a graph showing the wear resistance in steel turning of the product of the present invention and the comparative product in terms of the relationship between time (m1n) and flank wear amount (rn).

Claims (3)

[Claims] (1) In a method for synthesizing boron nitride by chemical vapor deposition, a mixed gas consisting of a boron atom-containing gas and a nitrogen atom-containing gas is preheated with a thermionic emitter and then passed through a DC discharge, A method for synthesizing high-hardness boron nitride, which is characterized in that the high-hardness boron nitride is then introduced onto the surface of a heated substrate to cause thermal decomposition and reaction, thereby precipitating high-hardness boron nitride. (2) The atomic ratio B/N of boron atoms in the boron atom-containing gas and nitrogen atoms in the nitrogen atom-containing gas is 0.000.
Claim No. 1 to 10,000
Synthesis method of high hardness boron nitride described in section ). (3) A method for synthesizing high-hardness boron nitride according to claim (1), which is carried out at a temperature of the thermionic emitting material of 1000° C. or higher.