JPH0310064A - Formation of nitride film - Google Patents

Abstract

PURPOSE:To form a nitride film excellent in surface roughness on the surface of a base material by allowing metallic ions produced from a cathode made of metallic material by means of arc discharge to react with nitrogen gas introduced together with trace amounts of oxygen gas. CONSTITUTION:In a vacuum vessel 1 in which evacuation is exerted via an exhaust hole 2, a cathode 3 composed of metallic material, such as Ti, and a base material 4, such as steel material, fitted on a holder 5 are disposed in a manner to be opposed to each other. Subsequently, arc discharge is produced between the above cathode 3 and the inner wall of the vessel 1 by means of an arc electric power source 6 via a trigger electrode 8, by which the metallic ions of the above metallic material are produced from the cathode 3. The above metallic ions are accelerated by a bias voltage impressed from a bias electric power source 7 on the holder 5. These metallic ions are allowed to react with nitrogen gas fed through a gas-introducing hole 9, by which a nitride film of TiN, etc., is formed on the base material 4. At this time, trace amounts og oxygen gas are introduced together with the above nitrogen gas. By this method, evaporated grains generated from the cathode 3 can be refined, and the surface roughness of the above nitride film can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming a nitride film such as a titanium nitride film used as a wear-resistant coating film for cutting tools, for example.

[Conventional technology]

Figure 1 shows a vacuum arc discharge type P V D (Physical Vapor D) used in the vacuum arc evaporation method.
FIG. 2 is a conceptual diagram showing an eposit4on) device. Nitrogen gas is introduced from the gas introduction port 9 into the vacuum container 1, which is evacuated from the exhaust port 2 by a vacuum pump (not shown), and the gas pressure is adjusted to 0.5 to 505 Torr. Inside the vacuum container 1, a base material 4 on which a nitride film is to be formed is fixedly placed on a holder 5, and a cathode 3 made of a metal such as Tl that forms the nitride film is placed opposite to this base material 4. It is provided. A trigger electrode 8 is provided near the cathode 3, and an arc voltage from an arc power source 6 is applied between the trigger electrode 8 and the cathode 3.

During film formation, the trigger electrode 8 is brought into contact with/separated from the cathode 3 to generate an arc discharge.
An arc discharge is caused between the vacuum vessel l and the cathode 3, which are at the same potential. This arc discharge causes the cathode 3
The metal constituting the ion is ionized, and the ionized metal is transferred to the bias 1 between the negative 8iii3 and the holder 5.
It is accelerated by the bias voltage applied from ltfi7 and guided to the surface of the base material 4. In this way, cathode 3
A nitride film is formed on the surface of the base material 4 by causing a reaction between the metal forming the base material 4 and the nitrogen gas from the gas inlet 9 on the surface of the base material 4 . In this nitride film, metal ions are accelerated and guided to the surface of the base material 4, so that it has good adhesion to the base material 4 and can be formed at a high film formation rate.

[Problem to be solved by the invention] When arc discharge occurs between the cathode 3 and the vacuum vessel 1,
Metal melts and explodes in a region called a cathode spot near the cathode 3, and most of this evaporated metal is ionized as described above. However, some neutral atoms are present in the exploded metal, and when these molten particles (droplets) of neutral atoms fly in the direction of the base material 4 and adhere to the surface of the base material 4, the base material 4 The roughness of the nitride film formed on the surface deteriorates. In other words, due to the adhesion of the drone bullet, the base material 4
Particles with a diameter of several μm are scattered on the surface. Therefore, if the base material 4 is used in sliding contact with a magnetic tape, such as a rotating cylinder of a VTR, problems such as damage to the magnetic tape may occur. Become.

An object of the present invention is to provide a method for forming a nitride film in which a good nitride film can be formed by significantly improving the surface roughness.

[Means to solve the problem]

In the present invention, in the vacuum arc evaporation method using the configuration shown in FIG. 1, oxygen gas is introduced from the gas inlet 9 together with nitrogen gas.

[Effect]

With the configuration shown in FIG. 1, if an appropriate amount of inert gas such as A, R, or He, nitrogen gas, or oxygen gas is introduced into the vacuum vessel l during the vapor deposition of the metal material from the cathode 3, this The surface of the cathode 3 is contaminated by the introduced gas,
As a result, the work function of the metal material constituting the cathode 3 decreases, making arc discharge more likely to occur. Therefore, in the cathode 3, the number of cathode spots is increased compared to the case where no gas is introduced, and the current per cathode spot is thereby reduced. This will reduce the size of the evaporated particles. As a result, the size of droplets adhering to the surface of the base material 4 is reduced, and the surface roughness of the nitride film on the surface of the base material 4 is improved.

Although this effect differs depending on the type of gas introduced into the vacuum vessel l, it is
The inventor of the present invention has found that this is remarkable when oxygen gas of That is, by introducing oxygen gas together with nitrogen gas into the vacuum container 1, a good nitride film can be formed on the surface of the base material 4.

If a large amount of oxygen gas is introduced together with the nitrogen gas, the film formed on the surface of the base material 4 will contain a large amount of oxygen, and the cathode 3 will absorb oxygen and become an insulator, making it stable. A problem arises in that it is no longer possible to cause arc discharge to occur.

In addition, when oxygen gas is low, it is not possible to sufficiently reduce the size of the Droplet adhering to the surface of the base material 4, and the surface roughness of the nitride film cannot be made sufficiently good. .

For this reason, the flow rate of oxygen gas introduced into the vacuum container l is as follows: PMt≧5×1, where the partial pressures of nitrogen gas and oxygen gas are respectively Put and Po.
0-'Torr, and the partial pressure POz of oxygen gas is lXl0-'~l
X 10-”Torr, and P () z
It is preferable that the condition <K P di is satisfied.

〔Example〕

A titanium nitride film was formed on the surface of the base material using the PVD apparatus shown in FIG. 1 under the following conditions.

Cathode: Tl Base material: 5KH51 (1,000 U tin-based high-speed tool steel) (Surface roughness R□80.2 μm) Gas pressure crab l X I Q-' ~ 3 X I 0-
3Torr arc current: 60A Bias voltage knee 2oov Film thickness: lIIm When film formation is performed by changing the partial pressure P W z of nitrogen gas and the partial pressure Po of oxygen gas under these conditions,
The measurement results of the roughness of the base material surface are shown in FIG. In this Figure 2, regarding surface roughness, symbol 'O
J indicates that the maximum height R□8 is 0.5 μm or less, and symbol “Δ” indicates that R1 is 1 to 34 m. In addition, the symbol "・" indicates that the film formed was mainly composed of titanium oxide, and the symbol "×"
" indicates that the arc discharge between the vacuum vessel 1 and the cathode 3 could not be stably performed.

From the measurement results shown in FIG. 2, it is understood that a titanium nitride film with good surface roughness is formed in the region S surrounded by the two-dot chain line in FIG. That is, the partial pressure P//2 of nitrogen gas is 5X10-'Torr or more, and the partial pressure PO2 of oxygen gas is lX10-'~IX1
0-”Torr, and P Oz < +/
In the case of 2P M 2 , a good titanium nitride film is formed using titanium nitride as a living body.

The film in region S in FIG. 2 is slightly browner in color than when only nitrogen gas is introduced into the vacuum vessel 1, and contains a relatively large amount of oxygen.
Its hardness is comparable to that of a film whose stoichiometric composition is TiN.

〔Effect of the invention〕

As described above, according to the method for forming a nitride film of the present invention,
A good nitride film with significantly improved surface roughness, that is, a smooth surface, can be formed on the surface of the base material. This prevents damage to the magnetic tape, for example, when the base material coated with the nitride film is used as a member that comes into sliding contact with a magnetic tape or the like.

[Brief explanation of drawings]

Fig. 1 is a conceptual diagram showing the basic configuration of a vacuum arc discharge type PVD apparatus, and Fig. 2 shows the surface roughness of a titanium nitride film formed according to an embodiment of the present invention and the partial pressures of nitrogen gas and oxygen gas. FIG. DESCRIPTION OF SYMBOLS 1... Vacuum container, 3... Cathode, 4... Base material, 9...
・・Gas inlet

Claims (1)

[Claims] Metal ions of the metal material are generated from the cathode by arc discharge between a vacuum container and a cathode made of a metal material, and the metal ions and the nitrogen gas introduced into the vacuum container are combined with each other. A method for forming a nitride film in which a nitride film of the metal material is formed on the surface of a substrate by the reaction described above, the method comprising: introducing oxygen gas together with nitrogen gas into the vacuum container.