JPH10140335A - Formation of chromium nitride film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of forming chromium nitride film high in productivity and furthermore high in adhesion and smoothness. SOLUTION: An arc type evaporating source 14 for melting a cathode by arc discharge having a cathode 16 consisting of chromium is used. Then, gaseous nitrogen 6 is introduced into a vacuum vessel 2, and furthermore, while negative bias voltage is applied to a substrate 8, and also, while a nitrogen-contg. gas 22 is sprayed on the surface of the cathode 16, the cathode 16 is melted by arc discharge to form chromium nitride film on the surface of the substrate 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for improving mechanical parts such as automobile parts, and more specifically, abrasion resistance, seizure resistance and sliding property of sliding parts. And a method for forming a smooth and highly adherent chromium nitride film on the surface of a substrate.

[0002]

2. Description of the Related Art Chromium nitride CrNx (x =
0.5-1) Typical methods of forming a film include an arc ion plating method and an electron beam ion plating method.

The arc-type ion plating method uses an arc-type evaporation source that dissolves a cathode by arc discharge, while introducing nitrogen gas into a vacuum vessel and applying a negative bias voltage to a base material to remove chromium from chromium. In this method, the cathode is melted by arc discharge, and chromium nitride, which is a reaction product of the cathode material and the atmospheric gas, is deposited on the surface of the substrate to form a film.

[0004] The electron beam ion plating method,
While introducing nitrogen gas into the vacuum vessel and applying a negative bias voltage to the base material, the evaporating material made of chromium is heated and evaporated by the electron beam extracted from the electron gun, and the reaction between the evaporating substance and the atmospheric gas is generated. In this method, chromium nitride is deposited on the surface of a substrate to form a film.

[0005]

In the arc ion plating method, the cathode is directly melted by an arc.
In addition, since the arc current can be easily increased, the ionized particles are contained in a large proportion in the cathode material which is highly productive and is evaporated from the arc-type evaporation source, and this is reduced by the negative bias voltage. It has the advantage that a film with high adhesion can be formed because it can be accelerated toward the substrate and collide with the substrate, but on the other hand, a large mass of cathode material together with fine cathode material from the cathode (This is called a droplet) also occurs at the same time, and adheres to the surface of the base material, so that there is a disadvantage that the smoothness of the film surface is poor (that is, the surface roughness of the film is poor).

On the other hand, the electron beam ion plating method has an advantage that the surface of the film is good because the generation of droplets is small and, on the other hand, the ionization rate of the vaporized material is low and the vaporized material is negatively charged. Since the bias voltage cannot accelerate sufficiently toward the base material, the adhesion of the film is low. It is necessary to convert the input power into an electron beam once with an electron gun, and easily increase the power of the electron beam. However, there is a drawback that productivity is low because the process cannot be performed.

Accordingly, an object of the present invention is to provide a method capable of forming a chromium nitride film having high productivity and high adhesion and smoothness.

[0008]

According to a method of forming a chromium nitride film of the present invention, an arc evaporation source for melting a cathode by arc discharge having a cathode made of chromium is used. While introducing a gas and applying a negative bias voltage to the substrate and blowing a nitrogen-containing gas onto the surface of the cathode, the cathode is melted by arc discharge to form a chromium nitride film on the surface of the substrate. Features.

Since the above method is basically an arc ion plating method, a chromium nitride film having high productivity and high adhesion can be formed as described above.

In addition, when a nitrogen-containing gas is blown onto a cathode made of chromium of an arc evaporation source at the time of film formation, a large number of cathode spots of arc discharge are formed on the cathode surface, causing arc branching near the surface of the cathode. Chromium and nitrogen react with each other to form chromium nitride, a high melting point compound, on the cathode surface, which suppresses the spread of the molten zone on the cathode surface, and forms a coarse molten zone on the cathode surface. Of the cathode material is prevented from scattering. As a result, a highly smooth chromium nitride film can be formed on the surface of the base material.

[0011]

FIG. 1 is a sectional view showing an example of an arc ion plating apparatus used for carrying out a method for forming a chromium nitride film according to the present invention.

The apparatus includes a vacuum vessel 2 evacuated by a vacuum evacuator (not shown), a holder 10 provided in the vacuum vessel 2 for holding a substrate 8, and a holder 10 facing the substrate 8. And an arc evaporation source 14 attached to the wall surface of the vacuum vessel 2. In the vacuum vessel 2,
A nitrogen gas 6 is introduced from the gas inlet 4.

The arc-type evaporation source 14 causes the cathode 16 to be locally melted by an arc discharge between the cathode 16 and the vacuum vessel 2 serving as the anode, thereby evaporating the cathode material 18. Between the cathode 16 and the vacuum vessel 2, for example, several tens to several hundreds of volts are supplied from a DC arc power supply 24 with the former being on the negative side.
An arc discharge voltage of the order of magnitude is applied. The arc evaporation source 14 further includes a gas blowing mechanism 2 that blows a nitrogen-containing gas 22 onto the surface of the cathode 16 (more specifically, onto the front surface thereof).
It has 0. It should be noted that a trigger electrode and the like for starting the arc are not shown.

The holder 10 and the base material 8 held thereon
From the DC bias power supply 26, for example, several hundred V to the potential of the vacuum vessel 2 (ground potential in this example).
A negative bias voltage of about several kV is applied.

The film formation using such an apparatus is performed as follows. That is, a cathode made of, for example, chromium is used as the cathode 16 of the arc evaporation source 14, and the inside of the vacuum vessel 2 is evacuated to, for example, about 10 ⁻⁶ Torr. Arc discharge is performed in the arc evaporation source 14 while applying a negative bias voltage from 8 to the bias power source 26 and blowing nitrogen-containing gas 22 from the gas blowing mechanism 20 onto the surface of the cathode 16. Thereby, the cathode material 18 (chromium in this case) is evaporated from the cathode 16. This cathode material 18
Are ionized, which are attracted to and collide with the substrate 8 to which the negative bias voltage is applied,
It combines with the surrounding nitrogen gas 6, thereby forming a chromium nitride CrNx (x = 0.5 to 1) film on the surface of the base material 8.

Such a film forming method is basically an arc-type ion plating method as described above, and the productivity is high because the arc-type evaporation source 14 is used. Moreover, since the ionized evaporating substance 18 can be accelerated toward the base material 8 by the bias voltage, a chromium nitride film having high adhesion can be formed.

Furthermore, when a nitrogen-containing gas 22 is blown from the gas blowing mechanism 20 to the cathode 16 during film formation, a large number of cathode spots of arc discharge are formed on the cathode surface and arc branching occurs near the surface of the cathode 16. Chromium and nitrogen react on the surface of the cathode to form chromium nitride (CrNx), which is a high melting point compound, on the cathode surface, which suppresses the spread of the molten portion on the cathode surface. The formation of a coarse fusion zone is suppressed, and the scattering of large lumps of cathode material (ie, droplets) is prevented. As a result, a highly smooth chromium nitride film can be formed on the surface of the substrate 8.

In the above arc type evaporation source 14,
Instead of the cathode 16 made of chromium, a cathode 16 made of chromium and a smaller amount of titanium may be used, so that titanium chromium nitride (CrTiNx) having a higher melting point than chromium nitride is formed on the cathode surface. ) Is formed, so that scattering of droplets can be further suppressed. As a result, a chromium nitride film with higher smoothness (more strictly, a titanium-containing chromium nitride film) can be formed on the surface of the substrate 8.

In this case, the cathode 16 may be an alloy of chromium and titanium, or a mixture of both. The reason for making titanium smaller than chromium is to minimize the formation of the chromium nitride film, which is the original purpose, as much as possible.

As the nitrogen-containing gas 22 blown from the gas blowing mechanism 20 to the cathode 16, a nitrogen gas, an ammonia (NH ₃ ) gas, a mixed gas of ammonia and hydrogen, or the like can be used. Among them, it is preferable to use a mixed gas of ammonia and hydrogen. In such a case, active NH radicals are generated near the surface of the cathode 16 by the arc discharge, and the active NH radicals are mixed with the cathode constituent material (that is, chromium or chromium). Chromium nitride or titanium chromium nitride is likely to be formed on the cathode surface. As a result, the scattering of the droplets can be more reliably prevented, and a chromium nitride film with higher smoothness can be formed on the surface of the substrate 8.

[0021]

【Example】

<Embodiment 1> In the apparatus shown in FIG. 1, while using a cathode 16 made of chromium and spraying a mixed gas of ammonia and hydrogen as a nitrogen-containing gas 22 at a flow rate of 200 sccm on the surface thereof, nitrogen gas 6 was introduced into the vacuum vessel 2. The partial pressure 10 ^-3
By flowing while maintaining Torr, a chromium nitride film having a thickness of 2 μm was formed on the surface of the substrate 8 made of SKD61. At this time, the bias voltage of the base material 8 was -300V.

For comparison, a conventional arc ion plating method and a conventional electron beam ion plating method, in which the above-mentioned mixed gas is not sprayed on the cathode 16, were subjected to the same conditions as above except for the evaporation method. Thus, a chromium nitride film was formed.

As a result, in the film formation by the conventional arc ion plating method, the average surface roughness (Ra) was 0.2 μm worse than the surface roughness of the substrate 8 before the film formation. On the other hand, in the film formation by the method of the example, the average surface roughness deteriorated only by 0.04 μm.

Further, the adhesion between the film and the substrate 8 is such that the critical load in the scratch test is 70 when the film is formed by the method of the embodiment.
N (Newton), which was about 1.7 times as large as that in the case of film formation by the conventional electron beam ion plating method.

<Embodiment 2> In the apparatus shown in FIG.
A titanium-containing chromium nitride film was formed on the surface of the base material 8 under the same conditions as in Example 1 except that a cathode 16 in which titanium was mixed with 10% by weight of chromium was used.

For comparison, a conventional arc ion plating method and a conventional electron beam ion plating method, in which the above-mentioned mixed gas is not sprayed on the cathode 16, were subjected to the same conditions as above except for the evaporation method. Thus, a titanium-containing chromium nitride film was formed.

As a result, in the film formation by the method of the embodiment,
Regarding the surface roughness of the film, the maximum surface roughness (Rmax) and the average surface roughness (Ra) were almost the same as those of the base material 8 before film formation, and no deterioration in smoothness was observed.

In the film adhesion by the method of the embodiment, the critical load in the scratch test was 69 N,
Again, it was about 1.7 times that in the case of film formation by the conventional electron beam ion plating method.

[0029]

Since the present invention is configured as described above, it has the following effects.

The invention according to claim 1 is basically an arc ion plating method, and has high productivity because an arc evaporation source is used. In addition, since the ionized cathode material can be accelerated toward the substrate by the negative bias voltage, a chromium nitride film having high adhesion can be formed.

Furthermore, by spraying a nitrogen-containing gas onto the cathode surface, the formation of a coarse molten portion on the cathode surface is suppressed, and the scattering of large lumps of the cathode material is prevented. A chromium nitride film having a high density can be formed.

According to the second aspect of the present invention, titanium chromium nitride having a higher melting point than chromium nitride is formed on the surface of the cathode, so that scattering of droplets can be further suppressed. As a result, a chromium nitride film having higher smoothness can be formed on the surface of the base material.

According to the third aspect of the present invention, active NH radicals are generated in the vicinity of the surface of the cathode, and the reactivity between the active NH radicals and the constituent materials of the cathode is increased. Therefore, chromium nitride or titanium chromium nitride is generated on the surface of the cathode. It will be easier. As a result, scattering of droplets can be more reliably prevented, and a chromium nitride film having higher smoothness can be formed on the surface of the base material.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of an arc ion plating apparatus used for carrying out a method for forming a chromium nitride film according to the present invention.

[Explanation of symbols]

 2 Vacuum container 6 Nitrogen gas 8 Base material 10 Holder 14 Arc-type evaporation source 16 Cathode 20 Gas spraying mechanism 22 Nitrogen-containing gas 26 Bias power supply

Claims (3)

[Claims] 1. An arc evaporation source for melting a cathode by arc discharge having a cathode made of chromium, introducing nitrogen gas into a vacuum vessel and applying a negative bias voltage to a substrate. A method for forming a chromium nitride film, comprising: dissolving a cathode by arc discharge while spraying a nitrogen-containing gas onto the surface of the cathode while forming a chromium nitride film on the surface of the substrate. 2. The method for forming a chromium nitride film according to claim 1, wherein in the arc evaporation source, a cathode made of chromium and a smaller amount of titanium is used instead of a cathode made of chromium. 3. The method according to claim 1, wherein the nitrogen-containing gas is a mixed gas of ammonia and hydrogen.