JPS62260063A - Method for synthesizing high hardness boron nitride - Google Patents

Abstract

PURPOSE:To obtain chemically stable BN having high hardness and satisfactory heat conductivity by heating a gaseous mixture of a gas contg. B with a gas contg. N with a heated thermoelectron emitting material and by leading the mixture to the surface of a heated substrate so as to bring the mixture into thermal decomposition and reaction. CONSTITUTION:A gaseous mixture of a gas contg. B such as B2H6 or BCl3 with a gas contg. N such as N2 or NH3 is heated with a thermoelectron emitting material heated to >=1,000 deg.C to produce an excited gas contg. B, an excited gas contg. N and atomic H. The excited gases are led to the surface of a substrate heated to 300-2,000 deg.C. The gases are thermally decomposed and the resulting free B and N are brought into SP<3> bond to each other to produce cubic BN. 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. This relates to a method for depositing cubic boron nitride, which has excellent resistance to metals and 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 substrates from the gas phase. It is.

[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. 60-181262, a boron component is evaporated onto a substrate from an evaporation source containing boron, and the ion species are deposited onto the substrate from an ion source that generates an ion ridge containing at least nitrogen. A method for producing a boron nitride film, which comprises irradiating the substrate for 30 minutes to produce boron nitride on the substrate.

■ Journal of Materials Science Letters
science 1etters), 4 (1985) 5
As shown on pages 1-54, H! A method for producing cubic boron nitride by chemically transporting boron using +Nt plasma.

■ Proceedings of the 9th Ion Engineering Symposium (1985, Tokyo), [Ion sources and ion-based applied technologies]
As shown in , while boron is evaporated with an HCD gun, N is ionized from the hollow anode and radiated to the substrate, and a high frequency is applied to the substrate to create a self-biasing effect to form cubic nitridation. How to produce boron.

■ (Syneresis; “Vacuum” Vol. 28, No. 27 (1985)
As shown in pages 29 to 54, boron is evaporated by applying an electron beam (EB) to a solid containing boron atoms, and a gas containing nitrogen atoms is poured into it to simultaneously ionize boron and nitrogen. , a method for producing cubic boron nitride on a substrate surface.

[Problem that the invention seeks to solve]

However, the method (2) has the drawback 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 atoms of the inert gas are incorporated into the deposited cubic boron nitride.

In the method (1) above, since the melting point and boiling point of boron are close to each other,
12B tends to cause bumping, which is difficult to control.

The purpose of the present invention is to provide a novel method for producing cubic boron nitride that solves the drawbacks and difficulties of the conventional methods, and includes stably depositing hard boron nitride on the surface of a substrate from the gas phase. For example, it can be coated on tools etc. to provide excellent machinability,
The object of the present invention is to provide a method for producing hard boron nitride that can provide wear resistance and chipping resistance.

[Means for solving problems]

As a result of intensive research into a method for synthesizing cubic boron nitride by chemical vapor deposition, the present inventors have found that a mixed gas consisting of a boron atom-containing gas and a nitrogen atom-containing gas according to the present invention is
After preheating with a thermionic emitter at 00°C or higher, the heated mixed gas is introduced onto the surface of the substrate heated to 500 to 2000°C to cause thermal decomposition and reaction, thereby converting high hardness boron nitride. A method for synthesizing high-hardness boron nitride, which is characterized by precipitation, has been achieved. In a particularly preferred embodiment of the present invention, the atomic ratio B/N of the boron atom gas in the boron atom-containing gas and the nitrogen atom gas in the nitrogen atom-containing gas is 0.1≦B/N≦10. Examples include the above methods.

In the present invention, by preheating a mixed gas of a boron atom-containing gas, a nitrogen atom-containing gas, and hydrogen as a thermoelectron emitting material heating body, the boron atom-containing gas and nitrogen atom-containing gas and atoms in an excited state are heated. Produces hydrogen in the form of hydrogen.

When this excited state boron atom-containing gas and nitrogen atom-containing gas are thermally decomposed on the heated substrate surface, the resulting free boron atoms and nitrogen atoms form SP" bonds with each other, producing cubic boron nitride. Since hydrogen gas is not used in the present invention, there is no concern that a B-)I compound will be formed, and only a B-N compound can be obtained.

Examples of the thermionic emitting material used in the present invention include tungsten filaments, thorium-containing tungsten filaments, etc. that can withstand high heat. In order to cause the formation, the temperature is preferably 1000°C or higher.

Examples of the boron atom-containing gas used in the present invention include B
,! '16, BCl3, EBr3, B, N, H4
Examples of the nitrogen atom-containing gas include H7, N
H, etc. are mentioned. The atomic ratio B/N of boron atoms in the boron atom-containing gas and nitrogen atoms in the nitrogen atom-containing gas used as the raw material gas of the present invention is preferably 0.1≦B/N≦1°. This is because when B/N < α1, an amorphous boron nitride film is likely to be deposited, and B/N
>1o, the boron content is excessive and amorphous boron is likely to be formed.

The substrate temperature in the present invention is preferably within the range of 300° C. to 2000° C. in order to thermally decompose the excited state boron [Toyo-containing gas and nitrogen atom-containing gas and cause them to react with each other. If the substrate temperature is less than 500°C, there will be insufficient energy to deposit cubic boron nitride on the substrate, and if it exceeds 2000°C, nitrogen will be extracted from the formed boron nitride film, resulting in non-cubic boron nitride. It becomes boron nitride. Note that the substrate used in the present invention is not particularly limited, and may include, for example, metal, alloy, 07Si, and AI.
Nitrides such as H, carbides, silicides, quartz, diamond, and other known substrate materials capable of forming a hard cap on their surfaces can be used.

In addition, in the present invention, the pressure inside the reaction tube is 0.1 to A O
It is preferable to adjust to a range of OTorr.

FIG. 1 is an explanatory diagram of an example of an apparatus used for synthesizing high-hardness boron nitride of the present invention, in which 1 is a reactor;
is an exhaust device, 3 (-i reaction gas supply device, 4 is a substrate support rod, 5 is a substrate support stand, 66-i reaction tube, 7 and 8 are cocks, 9 is a mixed gas supply tube, 10 is a thermionic radiation material , 11 is an exhaust port, and 12 is a substrate. In FIG. 1000 in the reaction tube 6.
The mixed gas ? After preheating, this heated mixed gas is introduced onto the surface of the substrate 12 heated to 500 to 2000° C., and the boron atom-containing gas and the nitrogen atom-containing gas are decomposed and reacted to precipitate cubic boron nitride. At this time, the pressure inside the reaction tube 6 is adjusted by the exhaust device 2 and the exhaust port 12.

〔Example〕

Examples 1 to 3 below are all examples in which high hardness boron nitride was synthesized according to the present invention in accordance with the configuration shown in FIG.

Example 1 A silicon wafer was used as the substrate, and 5 cc/sin of diborane gas and 20 cc/zin of ammonia gas were flowed as raw material gases. Reaction tube internal pressure 10
The temperature of the substrate was adjusted to Tnrr, the temperature of the substrate was 900 tl, the temperature of the Gesten filament was 2000° C., and the reaction was carried out for 5 hours. As a result, a boron nitride film with a thickness of approximately 2 μm was deposited on the surface of the substrate.

When X-ray diffraction was performed on the boron nitride film, the strongest CI of cubic boron nitride, 1.1), was the peak.
Since a sharp peak was detected at 2θ=452°, this boron nitride was identified as cubic boron nitride.

Example λ A molybdenum substrate was used, and the raw material gases were boron chloride gas 10 cc/min and ammonia gas 20 cc/min.
min'z (N, reaction tube internal pressure 8 Torr.

Substrate temperature 1000℃, tungsten filament temperature 2
The reaction was continued for 4 hours at 300°C.

As a result, a boron nitride film of about 3 μm was deposited on the surface of the substrate. When this film was subjected to X-ray diffraction, it was identified as cubic boron nitride, as in Example 1.

Example 5 Silicon wafer was used as base material, diborane gas 5 CC/min and nitrogen gas 50 CC/min as Kyoshi gas.
CC/min flow, reaction tube internal pressure j5 Torr, substrate temperature 800°C, and thorium-containing tungsten filament temperature 2200°C for 5 hours. continued.

As a result, a boron nitride film (approximately 1.8 μm thick) was deposited on the substrate surface, and this film was also observed by
Similarly, it was identified as cubic boron nitride.

As described above, cubic boron nitride could be synthesized under the conditions of Examples 1 to 3, so the cutting tip was coated with a cubic boron nitride film under the conditions of each example, and the resulting coated chip (Example A1~& corresponding to conditions 1~3
3), a cutting test was conducted. The base chip is l50-M-10 grade cemented carbide (model number 5N
0120408) A cutting tip was used, and the film-forming time was adjusted so that the coating layer thickness was approximately 3 μm. For comparison, the same substrate chip was coated with 511 m of TiN by the conventional method as Mu4, and the same base chip was coated with no coating as Mu5, and cutting tests were conducted in the same manner.

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,
It can be seen that the cut Ml chips coated with cubic boron nitride as a coating layer according to the present invention have extremely superior wear resistance compared to conventional TiN coated and uncoated chips.

Table 1 Table 2 Cutting performance of tips coated with cubic boron nitride according to the present invention, tips coated with TiC or JR,03, and tips without coating.

The results of comparing wear resistance and chipping resistance are shown in graphs in FIGS. 2, 5, and 4. In both comparisons, the same chip was coated with the same thickness. Cubic boron nitride is abbreviated as cBM.

FIG. 2 shows a comparison of cutting performance in steel turning, and is a diagram showing the relationship between cutting speed (+m) and life time when the workpiece material is SCM 455 and the tip is SNG A52.

Figure 3 shows a comparison of wear resistance in cast iron turning, work material: FOA5, tip: TNG 522, cutting speed =
250? It is a relationship diagram between the time (min) at FL/In1n and the amount of wear on the exposed surface (rWn).

Figure 4 shows a comparison of fracture resistance, work material: SNG 45
5. Chip: FCD 50, cutting speed = 500m/cut 1n, number of counterattacks and cutting time until breakage (min
).

As is clear from the above FIGS. 2, 5, and 41, the hard boron nitride-coated insert according to the present invention has excellent cutting performance, wear resistance, and chipping resistance. .

〔Effect of the invention〕

The present invention provides a novel method for precipitating cubic boron nitride from the gas phase using variable synthesis conditions, which has excellent thermal shock resistance, thermal conductivity, hardness, wear resistance, and resistance to iron group metals at high temperatures. It is. 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 poor thermal shock resistance, thermal conductivity, hardness and wear resistance, and resistance to iron group metals at high temperatures, so it can be used in cutting parts, wear-resistant parts, etc. It has great effects when used as a coating for heat-resistant members.

[Brief explanation of drawings]

FIG. M1 is a configuration diagram schematically explaining an embodiment of the present invention. Figures 2 to 4 are diagrams showing a comparison of the characteristics of the tip coated with the present invention and a conventional product. Figure 2 is a diagram showing a comparison of cutting performance, and Figure 3 is a diagram showing a comparison of wear resistance. FIG. 4 is a diagram showing a comparison of fracture resistance.

Claims (2)

[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 heated to 1000°C or higher, and then the Heating mixed gas 300~2
1. A method for synthesizing high-hardness boron nitride, which comprises introducing the high-hardness boron nitride onto the surface of a substrate heated to 000° C. for 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 0.1≦B
The method for synthesizing high hardness boron nitride according to claim (1), wherein /N≦10.