JPH0657408A - Formation of boron nitride film - Google Patents

Abstract

PURPOSE:To form a cBN film highly adhesive even to a substrate of intricate shape. CONSTITUTION:The vapor 10 of boron 9 is deposited on a substrate 4A set in a vacuum chamber 1, and the deposit is simultaneously irradiated with the nitrogen ion or mixture of nitrogen and rare gas ions 7 from an ion source 5. In this case, an accelerating voltage of the ion 7 is firstly made higher than the case where a cubic carbon nitride film is formed, the substrate 4A is rotated, the substrate 4A is irradiated with the ion while gradually changing the irradiation direction from vertical to + or -90 deg. to form a compositionally gradient layer in which the surface consists of pure boron nitride, and then a boron nitride film consisting essentially of the cubic crystal is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a boron nitride film which has a cubic crystal structure and is formed on a substrate having a complicated shape with good adhesion.

[0002]

BACKGROUND OF THE INVENTION Cubic boron nitride is a hard, excellent in heat conductivity, electrical insulation and the like and has low reactivity, and is an excellent wear resistant material. Conventionally, as a method for forming a film of boron nitride (hereinafter, referred to as cBN) mainly containing cubic boron nitride on a substrate, a vapor deposition method using ions (hereinafter, referred to as an ion vapor deposition method), an ion plating method,
Alternatively, a plasma CVD (chemical vapor deposition) method or the like has been studied.

For example, a method for forming cBN by an ion vapor deposition method has been proposed (JP-A-2-259059). This forming method uses the apparatus shown in FIG.

In the apparatus shown in FIG. 6, the chamber 1 has an exhaust port 2, and the exhaust port 2 communicates with a vacuum source (not shown). A base material holder 3 attached to the ceiling is provided above the chamber 1, and a base material 4 is held on the base material holder 3. On the other hand, the ion source 5 installed so as to face the base material 4 is, for example, a microwave discharge type ion source. The ion source 5 ionizes the nitrogen gas or the mixed gas of nitrogen / rare gas supplied from the gas introduction pipe 6 and accelerates it by an electric field to irradiate the base material 4 as ions 7. Further, the evaporation source 8 arranged in the lower part of the chamber 1 and below the base material holder 3 is, for example, an electron beam evaporation source, and melts and evaporates the boron 9 which is an evaporation material held therein, The steam 10 is generated. Furthermore, a film thickness monitor 11 for measuring the evaporation rate of boron is provided above the chamber 1.

With such an apparatus, a cBN film can be formed on the substrate 4 by simultaneously vapor-depositing the vapor 10 of boron 9 and irradiating the ions 7 on the substrate 4.
An example of conditions for synthesizing a cBN film by this method is as follows: mixed gas composition and flow rate: 3 SCCM with Ar 65%, N ₂ 35%, accelerating voltage of mixed ions 0.5 kV, mixed ion current density 200 μA / cm. ^{2. The} deposition rate of boron is 0.5Å / s.

[0006]

However, the cBN film formed by the conventional method as described above has large internal stress and poor reactivity with the base material, and thus has poor adhesion. Therefore, even if a cBN film is formed on a base material such as metal or ceramics by such a method, there is a problem that peeling easily occurs.

Therefore, using a device as shown in FIG.
Before the formation of the BN film, the acceleration voltage of nitrogen ions or mixed ions of nitrogen / rare gases is increased to 5 to 200 kV and, at the same time, boron is vapor-deposited to allow nitrogen and boron atoms to penetrate into the base material for nitriding. A method of forming a graded composition layer of boron was also proposed together (Japanese Patent Laid-Open No. Hei 4-
120267).

Generally, practical tools, wear-resistant members, etc. are not limited to flat shapes, but complicated shapes such as combinations of curved surfaces and inclined surfaces. The above-mentioned method has a problem that the cBN film having good adhesion can be obtained on a flat substrate, but the formed cBN film is easily peeled off on a substrate having a complicated shape.

In view of such circumstances, it is an object of the present invention to provide a method for forming a boron nitride film capable of forming a cBN film having good adhesion even to a base material having a complicated shape.

[0010]

A method of forming a boron nitride film according to the present invention which achieves the above object, comprises depositing boron on a base material placed in a vacuum and at the same time introducing nitrogen ions or nitrogen / diluted nitrogen from an ion source. In a method of forming a boron nitride film whose crystal structure is mainly composed of cubic crystals on the substrate by an ion deposition method of irradiating a mixed ion of a gas, first, a boron nitride film mainly composed of cubic crystals is used as an acceleration voltage of the ions. From the inside of the base material by gradually changing the irradiation direction of ions to the base material within ± 90 degrees from the vertical direction by giving a motion such as rotation or swing to the base material. The concentration of boron nitride is continuously increased from zero to the surface to form a graded composition layer such that pure boron nitride is formed on the surface, and thereafter, the graded composition layer is mainly formed on the graded composition layer. And forming a boron nitride film made of cubic and.

[0011]

When the accelerating voltage of nitrogen ions or mixed ions of nitrogen / rare gases is set higher than the conditions for forming a boron nitride film mainly composed of cubic crystals, for example, 10 to 100 keV,
As the nitrogen atoms are injected into the substrate, the pushing of the substrate atoms and boron atoms into the substrate or the extrusion of the substrate atoms, boron atoms and nitrogen atoms occurs. At this time, if the density of ions to be irradiated and the deposition rate of boron are properly selected,
A gradient composition layer of boron nitride is formed in a depth range of about 2000 Å from the surface of the substrate. However, the formation of this gradient composition layer largely depends on the irradiation direction of the ions on the substrate, but the substrate is subjected to a motion such as rotation or swing to change the irradiation direction of the ions on the substrate from the vertical direction by ±. 90
Gradually changing between the degrees, the dependence of the ions on the irradiation direction is averaged, and a good graded composition layer is formed.

[0012]

EXAMPLES The present invention will be described below based on examples.

FIG. 1 shows an example of an apparatus for carrying out the method of the present invention. The members having the same functions as those in FIG. 6 are designated by the same reference numerals.

In the apparatus shown in FIG. 1, the chamber 1 has an exhaust port 2, and the exhaust port 2 communicates with a vacuum source (not shown). A base material holder 3A attached to the ceiling is provided above the chamber 1, and a base material 4A is held by the base material holder 3A. The base material holder 3A has a rotation drive mechanism, and can rotate the cylindrical base material 4A about an axis parallel to the surface of the base material holder 3A perpendicular to the irradiation direction of the ions 7. . On the other hand, the base material 4
The ion source 5 installed so as to face A is, for example, a microwave discharge type ion source. The ion source 5 ionizes the nitrogen gas or the mixed gas of nitrogen and rare gas supplied from the gas introduction pipe 6 and accelerates it by the electric field,
A is irradiated to A as ions 7. Further, the evaporation source 8 arranged in the lower part of the chamber 1 and below the base material holder 3A is, for example, an electron beam evaporation source, and melts and evaporates boron 9 which is an evaporation material held therein,
The steam 10 is generated. Furthermore, chamber 1
A film thickness monitor 11 for measuring the evaporation rate of boron is provided on the upper part of the
Is provided.

The base material 4A has an outer diameter of 10 mm and a length of 20 mm.
A cylindrical steel material having an outer peripheral surface coated with titanium nitride in a thickness of 3 μm is used. After this is attached to the base material holder 3A, the chamber 1 is evacuated to 1 × 10 ⁻⁶ torr. Then, pure nitrogen gas is introduced into the ion source 5 at a flow rate of 1 SCCM for ionization, and the ions 7 are accelerated with an acceleration voltage of 70 kV to form the ions 4 in the substrate 4.
Irradiate toward A. At this time, the ion current density is 20
It was μA / cm ² . At the same time, a vapor 10 of boron 9 was vapor-deposited from the vaporization source 8 at a vapor deposition rate of 0.4Å / s. While rotating the substrate 4A at a rotation speed of 1 rpm, this state was maintained for about 1 hour until the irradiation amount of nitrogen ions reached 1 × 10 ¹⁸ pieces / cm ² . At this time, the pressure in the chamber 1 is 1 ×
It was 10 ⁻⁶ torr. As a result, a gradient composition layer of boron nitride was formed on the surface of the base material 4A.

Next, the gas introduced into the ion source 5 is switched from pure nitrogen gas to a mixed gas of 64 vol% argon and 36 vol% nitrogen gas, the flow rate is set to 3 SCCM, the acceleration voltage is set to 0.5 kV, and the nitrogen-argon mixed ion is set. 7 was irradiated toward the base material 4A. At the same time, the vapor 10 of boron 9 was vapor-deposited from the vaporization source 8 at a vapor deposition rate of 0.5Å / s. At this time, the current density of the nitrogen-argon mixed ions is about 200 μA / cm ² , and the pressure in the chamber 1 is 1 × 1.
It was 0 ^-4 torr. By maintaining this state for about 3 hours while rotating the substrate 4A at 1 rpm, a boron nitride film having a thickness of about 1 μm was obtained.

The obtained film was confirmed by IR absorption spectrum and electron beam diffraction to be a boron nitride film mainly having a cubic crystal structure. The hardness of this cBN film is Vickers hardness of 4000 to 500 for a load of 10 gf.
It was 0 kg / mm ² . Also, peeling does not occur at all,
The scratch test showed a critical load of 20 to 50 N, and the adhesion was good.

Next, the ions 7 in the formation of the graded composition layer
Explain the test results on the dependence of the
It First, as shown in FIG. 2, for example, titanium nitride is used.
Angle θ between the normal o of the base material 4B and the irradiation direction of the ions 7
At 45 ° and nitrogen ion current density of 20 μA / cm ²，
Boron deposition rate is 0.4Å / s and ion dose is 1
× 10¹⁸Pieces / cm²The graded composition layer was formed under the conditions of. this
Depth composition profile by Auger analysis of graded composition layer
The file is shown in FIG. According to the figure, the depth of the graded composition layer is
It is about 2000Å and the outermost surface is almost pure boron nitride.
there were.

Then, gradient composition layers were formed under the same conditions except that θ was changed to 0 ° and 70 °. The composition profile in the depth direction is as shown in FIGS. 4 and 5. In the case of θ = 0 °, the effect of accelerating ions to eject the surface atoms of the base material 4B by the acceleration ions is smaller than that in the case of θ = 45 °. Has been formed. Also, θ = 70
In the case of °, since the repelling effect is larger than that in the case of θ = 45 °, titanium as a base material component is slightly detected on the surface, but about 1800Å and θ =
A gradient composition layer having a thickness close to that obtained at 0 ° and 45 ° is formed.

Therefore, under the above conditions, that is, under the condition that a gradient composition layer whose surface is pure boron nitride is formed in the case of θ = 45 °, the substrate 4B changes from 0 ° to 90 ° in a constant rate. When a graded composition layer of boron nitride was formed while rotating at a constant speed, for example, 1 rpm, a graded composition layer having almost the same composition profile as that shown in FIG. 3 was uniformly obtained.

Such a gradient composition has a moderate dependence of the repelling effect of surface atoms due to accelerated ions on the angle θ formed by the substrate surface normal and the ion irradiation direction, that is, the acceleration voltage is 10 to 100 kV. , Preferably 30 to 1
It is obtained in the range of 00 kV. If the accelerating voltage is lower than this, the repelling effect is too large and the gradient composition layer is hard to be formed.On the other hand, if the accelerating voltage is too large, the repelling effect is large and a layer having a large boron atom ratio to nitrogen is formed on the surface. This is because they are formed and both are not preferable. Then, when a cBN film is formed on the gradient composition layer thus formed by an ion deposition method, the cB film is removed from the base material.
Since the composition up to the N film is gentle, the adhesion is good.

In the above embodiment, the base material 4 made of a cylindrical steel material is used.
Since the gradient composition of boron nitride is formed by rotating A about its axis, the angle corresponding to θ shown in FIG.
The graded composition layer is formed while continuously changing in the range of 90 ° to ± 90 °. Therefore, its composition profile was similar to that shown in FIG. 3, and therefore the cBN film formed on this gradient composition layer had good adhesion.

Many practical tools, wear-resistant members and the like have complicated shapes such as a combination of curved surfaces and inclined surfaces. Even when the cBN film is formed using these as a base material, the present invention can be used. For example, by rotating the substrate, a gradient composition layer of boron nitride can be uniformly formed on any part of a complicated shape, and the cBN film is formed on the layer, so that uniform and good adhesion can be obtained. it can.

[0024]

As described above, according to the method for forming a boron nitride film according to the present invention, a boron nitride film mainly composed of cubic crystals having high adhesion and high hardness even on a substrate having a complicated shape. Since it can be formed, it can be applied to wear-resistant members such as tools and bearings, can withstand practical use, and has great industrial utility value.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of an apparatus for carrying out the method of the present invention.

FIG. 2 is an explanatory diagram illustrating a test example of the present invention.

FIG. 3 is an explanatory diagram showing a composition profile in the depth direction in a test example.

FIG. 4 is an explanatory diagram showing a composition profile in the depth direction in a test example.

FIG. 5 is an explanatory diagram showing a composition profile in the depth direction in a test example.

FIG. 6 is a schematic view showing an apparatus for carrying out a conventional method for forming a boron nitride film.

[Explanation of symbols]

 1 Chamber 2 Exhaust Port 3A Substrate Holder 4A, 4B Base Material 5 Ion Source 6 Gas Introducing Tube 7 Nitrogen Ion or Nitrogen / Rare Gas Mixed Ion 8 Evaporation Source 9 Boron 10 Vapor 11 Film Thickness Monitor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiya Watanabe 1-8-1, Koura, Kanazawa-ku, Yokohama, Kanagawa Prefecture Mitsubishi Heavy Industries, Ltd.

Claims (1)

[Claims] 1. A crystalline structure is mainly formed on a base material by an ion deposition method in which boron is vapor-deposited on a base material placed in a vacuum and at the same time, nitrogen ions or a mixed ion of nitrogen and a rare gas is irradiated from an ion source. In the method for forming a cubic boron nitride film, first, the accelerating voltage of the ions is increased above the conditions for forming the cubic boron nitride film, and a motion such as rotation or rocking is applied to the base material. By gradually changing the irradiation direction of ions to the base material within ± 90 degrees from the vertical direction, the concentration of boron nitride continuously increases from zero from the inside of the base material to the surface, and pure nitridation is performed on the surface. A boron nitride film characterized by forming a graded composition layer such as boron and then forming a boron nitride film mainly composed of cubic crystals on the graded composition layer. Forming method.