JPS62260062A - Method for synthesizing high hardness boron nitride - Google Patents

Abstract

PURPOSE:To deposit chemically stable BN having high hardness on the surface of a substrate by passing a gaseous mixture of a gas contg. B with a gas contg. N through microwave electrodeless discharge and by leading the mixture to the surface of the substrate heated to a specified temp. so as to bring the mixture into thermal decomposition and reaction. CONSTITUTION:A gaseous mixture of a gas contg. B such as B2H6, BCl3 or BBr3 with a gas contg. N such as N2 or NH3 is passed through microwave electrodeless discharge to excite the gases. The gaseous mixture of the excited gases is then led to the surface of a substrate heated to 300-1,300 deg.C. The mixture is brought into thermal decomposition and reaction to deposit BN on the surface of the substrate. Thus, cubic BN having superior thermal shock resistance, heat conductivity, hardness and wear resistance and also having superior resistance to iron group metals at high temp. can be deposited from the vapor phase under variable synthesis conditions.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention not only has extremely high hardness, but also has high thermal conductivity and is chemically stable. In addition, unlike diamond, it is an iron-free metal. The present invention relates to a method for depositing cubic boron nitride, which is used in tool materials such as cutting tools and wear-resistant tools, as well as electronic materials such as heat sinks, on the surface of substrates from the gas phase due to its excellent resistance to .

[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. 6Ω-181262, a boron component is evaporated onto a substrate from an evaporation source containing boron, and at the same time, an ion source that generates ionic species containing at least nitrogen is deposited on the substrate. A method for producing a boron nitride film, which comprises irradiating the substrate with boron nitride to produce boron nitride on the substrate.

■ “Journal of Materials Science
Letters (Journal of material
sscience 1ettθrday), 4(1
985) pp. 51-54, a method for producing cubic boron nitride by chemically transporting poron using H20N plasma.

■ Proceedings of the 9th Ion Engineering Symposium (1985, Tokyo), "Ion sources and ion-based applied technologies"
As shown in , while evaporating poron with a Hol: gun, N2 is ionized from the hollow anode and radiated to the substrate, and a high frequency is applied to the substrate to create a self-bias effect and ionize the cubic boron nitride. How to generate.

■ [Namba; [Vacuum] No. 28 @ No. 27 (1985)
As shown in pages 29 to 54, boron is evaporated by exposing a boron atom-containing solid to an electron beam (F, B), and a nitrogen atom-containing gas is poured into it to simultaneously ionize boron and nitrogen. In particular, a method for producing cubic boron nitride on the surface of a substrate.

[Problem that the invention seeks to solve]

However, the disadvantage of method (2) is that the ion beam generating device and its focusing device are expensive. Since the method (2) uses high-power RF plasma for film formation, impurities from the reaction system are likely to be mixed in. Like method (2), method (2) has the disadvantages that the ion beam generating device and its focusing device are expensive, and that the atoms of the inert gas are absorbed into the precipitated cubic boron nitride. have In the method (2) above, since the melting point and boiling point of boron are close to each other, bumping tends to occur when 1B is applied, and it is difficult to control this.

The purpose of the present invention is to provide a novel method for producing cubic boron which solves the drawbacks and difficulties of the conventional method, and allows hard boron nitride to be stably deposited on the substrate surface from the gas phase, for example. It is an object of the present invention to provide a method for fabricating hard boron nitride that can be coated on tools and the like to provide excellent machinability, wear resistance, and chipping resistance.

[Means for solving problems]

In the present invention, a mixed gas consisting of a boron atom-containing gas and a nitrogen atom-containing gas is passed through a microwave non-polar discharge and then introduced onto the surface of a substrate heated to 500 to 1500°C. This is a method for synthesizing high hardness boron nitride, which is characterized by thermal decomposition and reaction to precipitate boron nitride on the surface of the substrate. In a particularly preferred embodiment of the present invention, the ratio B/N (atomic ratio) of boron atoms in a boron atom-containing gas to nitrogen atoms in a nitrogen Toyo-containing gas is provided.
l, [11≦B/N≦10.

The present invention allows a mixed gas consisting of a boron atom-containing gas and a nitrogen atom-containing gas to pass through a microwave non-polar discharge to produce a mixed gas consisting of an excited state boron atom-containing gas and an excited state nitrogen atom-containing gas. is introduced onto the heated substrate surface, thermally decomposed on the substrate surface, and the B-N s
By providing enough energy to cause p” bonds,
This method produces cubic boron nitride on the surface of the substrate.

Since hydrogen gas is not used in the present invention, there is no concern that a B-H compound will be formed (only a B-N compound can be obtained).

In the present invention, it is preferable to employ microwave nonpolar discharge in order to sustain stable discharge. In the case of direct current discharge, since electrodes are used, it is difficult to generate continuous discharge for a long time.

The pressure inside the tube that generates the non-polar discharge is preferably in the range of α05 Torr to A OOTorr in order to maintain stable discharge.

As the boron atom-containing gas used in the present invention,
For example, B, H,, BCIs, BBr, , BsN
5Ha, and examples of the nitrogen atom-containing gas include Nt r NH3+. It goes without saying that in order to maintain the plasma, a gas that does not participate in this reaction at all, such as argon gas, can be added as appropriate. The number of boron atoms in the boron atom-containing gas and the nitrogen atomic number ratio E/N in the nitrogen atom-containing gas are cL1≦B/
The range of N≦10 is preferable. This is because when B/N < α1, an amorphous boron nitride film tends to precipitate, and E/N
>10, the amount of boron is excessive and amorphous boron is likely to be formed.

In the present invention, the temperature of the substrate is 300-15007:
Preferably, the temperature is heated to .

When the substrate temperature is less than 300° C., there is insufficient energy for excited boron atoms and nitrogen atoms to form θp3 bonds with each other to form cubic boron nitride. Furthermore, when the substrate temperature exceeds 1300°C, boron nitride 1 precipitates.
Nitrogen is extracted from the surrounding area, resulting in a non-cubic boron nitride film.

Next, a detailed explanation will be given with reference to the method sections of the present invention. FIG. 1 is a diagram showing an embodiment of synthesizing high hardness boron nitride according to the present invention, in which 1 and 2 are boron atom-containing gas and nitrogen atom-containing gas supply devices, 3 is a wave guide, and 4 is a microwave excavator, 5 is a reaction chamber, and 6 is a microwave excavator.
10 and 11 are cocks, and 12 is an exhaust port.

The boron atom-containing gas and the nitrogen atom-containing gas supplied from the gas supply devices 1 and 2 via the cocks 10 and 11 are introduced into the reaction chamber 5 as a mixed gas, and the microwave excavator 4
The substrate 7 is heated to 300 to 1500° C. after being passed through a microwave non-polar discharge by the wave guide 5.
is introduced onto the surface of the substrate 7 and reacted to precipitate cubic boron nitride on the surface of the substrate 7. In addition, the inside of the reactor 5 is 005~"!0 due to the exhaust system including the cock 9, the exhaust device 6, and the exhaust port 12.
Set the pressure to 0 Torr.

In addition, in the method shown in Fig. 1, since the substrate 7 is present during the microwave discharge, there is a force 1 that can change the substrate temperature depending on the intensity of the microwave plasma, and the resistance is increased by keeping the substrate outside the microwave plasma. The substrate may be heated separately using a heating furnace or the like.

The substrate used in the present invention is not particularly limited, and may be formed with, for example, metal 2 alloy, a-8i, A/N, other nitrides, carbides, silicide 2 quartz, diamond, or other known hard coatings. Substrate materials can be used.

[Execution e2] Example 1 High hardness boron nitride according to the present invention was synthesized according to the structure shown in FIG. A silicon wafer was used as the substrate, and a mixed gas of diborane gas 2 CC/ml and ammonia gas 5 ω/min was flowed as the reaction gas.

The pressure inside the reaction tube was adjusted to 20 Torr, and the substrate temperature was adjusted to 9
The temperature was 00°C. As a result of continuing the reaction for 5 hours with a microwave output of 300W, a thickness of about 0.8μ was formed on the silicon substrate surface.
A boron nitride film of m was formed. When we performed X-ray diffraction on this film, we detected a very strong peak near 2θ = 452°, which is the peak of cubic boron nitride (f, 1.j). It was identified as a crystalline boron nitride film.

Example 2 According to the structure shown in FIG. 1, boron nitride was synthesized according to the present invention using a molybdenum substrate. The reaction gases were diborane gas 1 cc/ml and nitrogen gas 3 cc/ml.
ffl1n was flowed, and the pressure inside the reaction tube was 80 Torr.

Substrate @850℃, microwave output a　o　o　w.

The reaction was continued for 4 hours. As a result, a thickness of approximately 0 on the substrate surface is obtained.
．． When a 9 μm boron nitride film was deposited and X-ray diffraction was performed, a very strong peak of (1,1,1) could be detected as in Example 1, indicating that the film was a cubic boron nitride film. I was able to identify that there was one.

Example 5 According to the structure shown in FIG. 1, boron nitride was synthesized according to the present invention using a silicone wafer as a substrate. Boron fluoride gas 2 CC/min and ammonia gas A CC/min were flowed as reaction gases, and the pressure inside the reaction tube was 50 To
rr, substrate temperature 1000℃, microwave output 550W
, the film formation time was 3 hours. As a result, a boron nitride film with a thickness of approximately α9 μm was deposited on the substrate surface, and this film was also identified as a cubic boron nitride film by X-ray diffraction.

As described above, cubic boron nitride was synthesized under the conditions of Examples 1 to 5. Using these conditions, a cutting chip was coated with a cubic boron nitride film, and the resulting coated chip was subjected to a cutting test. I did it. The base chip is made of So-M-10 grade cemented carbide (model number 5N).
G120408) Using a cutting tip, the coating layer thickness is 2 μm
The film-forming time of each example was changed so that
5). In addition, for comparison, 2 TiC was prepared using the conventional method.
The one coated to a μ-thickness was labeled A4, and the one without coating was labeled 5. The conditions of the cutting test are summarized in Table 1, and the results of the cutting test are summarized in Table 2. As is clear from Tables 1 and 2, the cutting tip coated with the cubic boron nitride film according to the present invention as a coating layer has extremely excellent wear resistance.

Table 1. Cutting test condition table λ Cutting test results In addition, wear resistance, cutting performance, and fracture resistance of tips coated with cubic boron nitride according to the present invention, tips coated with TiC and/or AZto, and tips without coating The results of the comparison are shown in graphs in FIGS. 2, 3, and 4.

In both comparisons, the same chip was coated with the same thickness. Cubic boron nitride is abbreviated as CEN.

Figure 2 shows a comparison of wear resistance in steel turning, with workpiece material: BCM AS5, tip: TNG 522, cutting speed 2300 @/'In1n time (win) and amount of wear on the exposed surface (dark). It is a relationship diagram.

Figure 3 shows a comparison of cutting performance in cast iron turning, when work material: Fe12, tip: 19NG 452,
It is a relationship diagram of cutting speed (habituation) and life time.

Figure 4 shows a comparison of fracture resistance, work material: SCM 45
5. Chip: SCMG 12040B, cutting speed: 2
It is a figure of the number of counterattacks and the cutting time (min) until breakage at the time of 00 yg/min.

As is clear from the above figures 2, 3, and 4, the hard boron nitride-coated insert according to the present invention has excellent wear resistance, cutting performance, and chipping resistance. .

〔Effect of the invention〕

The present invention uses cubic boron nitride, which has excellent thermal shock resistance, thermal conductivity, hardness, wear resistance, and resistance to iron group metals at high temperatures! lx Since the synthesis conditions are thus variable, the method of the present invention is very advantageous for forming cubic boron nitride coatings on cutting members, wear-resistant members, heat-resistant members, and the like.

The cubic boron nitride obtained by the method of the present invention has excellent thermal shock resistance, thermal conductivity, hardness and wear resistance, and resistance to iron group metals at high temperatures, so it can be used for cutting parts, wear-resistant parts, and heat-resistant parts. It has great effects when used as a coating film.

[Brief explanation of drawings]

FIG. 1 is a block diagram schematically explaining an embodiment of the present invention. Figures 2 to 4 are diagrams showing a comparison of characteristics between the tip coated with the present invention and a conventional product. Figure 2 is a diagram showing a comparison of wear resistance, and Figure 5 is a comparison of cutting performance. Figure 4 showing
The figure shows a comparison of fracture resistance.

Claims (2)

[Claims] (1) A mixed gas consisting of a boron atom-containing gas and a nitrogen atom-containing gas is passed through a microwave non-polar discharge, and then introduced onto the substrate surface heated to 300 to 1300°C to thermally decompose the mixed gas. A method for synthesizing high hardness boron nitride, which comprises reacting and depositing boron nitride on the surface of the substrate. (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 0.1≦B
The method for synthesizing high hardness boron nitride according to claim (1), wherein /N≦10.