JPH01129958A - Formation of titanium nitride film having high adhesive strength - Google Patents

Abstract

PURPOSE:To modify the surface of a material to be treated and to form a titanium nitride film excellent in adhesive strength and wear resistance by forming a nitriding layer and a nitrogen diffused layer on the surface of a material to be treated and then producing plasma and evaporating titanium. CONSTITUTION:A nitrogen gas or a gaseous mixture of nitrogen and hydrogen is introduced into a vacuum vessel 1, and a voltage is impressed on a high-frequency coil 2 to initiate plasma discharge. A D.C. voltage is impressed between a cathode (material to be treated) 10 and an anode to produce glow discharge, and ionized nitrogen is accelerated and the surface of the material 10 to be treated is bombarded with the above ionized nitrogen, by which a nitriding layer and nitrogen are formed. subsequently, plasma is interrupted and gas is stopped, and a gaseous mixture of nitrogen and hydrogen is introduced. Titanium 5 in an evaporation source 4 is evaporated by the actuation of an electron gun 6, by which a titanium nitride film is formed on the surface of the material 10 to be treated. By this method, a thick film practically free from peeling and excellent in adhesive strength can be formed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for forming a highly adhesive titanium nitride film, which is particularly suitable for modifying the surface of an industrial wear-resistant material that is subjected to sliding or mounding. It provides:

BACKGROUND ART Surface modification techniques for industrial members are being converted from plating, which is a conventional wet method, to dry methods such as physical vapor deposition and chemical vapor deposition. This dry method surface modification technology is
Films are formed in a gas phase, and in recent years, they have been attracting attention, especially in the electronics industry, because they can form dense, high-quality films, and there is no risk of causing pollution problems during waste liquid treatment.

Such vapor phase film formation is generally said to have excellent adhesion, but this is only when the film thickness is 1 to 2 μm.
As the film becomes thicker, it tends to peel off easily, so the film thickness is limited to 5 to 10 μm at most.
It is used at a thickness of about 3 μm. For this reason, it is unsuitable for parts that require wear resistance over a long period of time or those that are subject to impact, and the fields of application are limited.

The causes of peeling due to thicker films are the difference in linear expansion coefficient between the base material and the film, large thermal stress, and large residual stress. Attempts may also be made to reduce the

Another method for preventing peeling is to provide a multilayer structure by coating the material with a material having a similar coefficient of linear expansion as a buffer material as an intermediate coating. Or vacuum the particles you want to add.

There is an ion implantation method in which elements are ionized inside the chamber, accelerated by an electrostatic field, and then implanted into the surface of the object to be deposited.This method allows elements to be added and mixed without chemical restrictions, and it is possible to combine the object and the film. Although the feature is that no interface is created between the layers, it is difficult to increase the thickness of the film, which is only about 0.1 μm at most, and no drastic measures have been taken yet.

[Problem that the invention seeks to solve]

The above-mentioned conventional technology does not give sufficient consideration to the problem of peeling and thickening of the film, and is limited to applications that take advantage of only the characteristics of a thin film. For this reason, it has been almost impossible to apply it as a wear-resistant member that is subjected to long-term sliding or impact.

An object of the present invention is to modify the surface of a workpiece to form a thick film with excellent adhesion and wear resistance.

[Means for Solving the Problems] The above purpose is to generate plasma in a nitrogen gas atmosphere or a mixed gas atmosphere of nitrogen gas and hydrogen gas, and to ionize and accelerate the nitrogen gas by glow discharge to ionize and accelerate the process. After colliding with the surface of the object to be treated to form a nitrided layer and a nitrogen diffusion layer on the surface of the object.

This is achieved by generating plasma in the atmosphere and then evaporating titanium to form a titanium nitride film on the surface of the object to be processed.

[Effect]

Nitrogen or a mixed gas of nitrogen and hydrogen is introduced into a vacuum atmosphere to generate plasma, and by applying a negative bias to the object to be processed, a glow discharge is caused and the nitrogen gas is ionized. The ionized N positive ions and NH positive ions are accelerated in the cathode descending section and collide with the surface of the object to be treated, where they exchange nitrogen and the atoms of the parent material that are ejected by the sputtering action form a plasma. It combines with nitrogen ions inside to form nitride, and a portion of it is precipitated again on the surface of the object to be treated, and nitridation progresses on one surface while sequentially changing into a lower-order nitride.

This nitride layer is used as a base treatment layer, and since low-order nitrides are particularly hard and have excellent toughness, if a titanium nitride film is formed after forming this nitride, the nitride layer also acts as a buffer material and has good adhesion. This makes it possible to increase the thickness of the film.

〔Example〕

FIG. 1 shows the overall configuration of a high frequency ion blating apparatus for forming the highly adhesive film of the present invention.

This device is a general ion brating device that uses high-frequency excited plasma, and a vacuum chamber 1 includes a high-frequency coil 2, a gas supply pipe 3, an evaporation source (crucible) 4. There is an evaporated metal (titanium) 5, and an electron gun 6 is connected to a DC power supply control system 7 via a feedthrough 9.

Further, the object to be processed 10 can be attached in close contact with the substrate holder 11, and a heater 1 for heating the substrate is provided above the substrate holder 11.
There are 2. Furthermore, the negative side of the substrate holder 11 is connected to a DC bias power supply 13 for accelerating positive ions of ionized nitrogen and metal, so as to form an electric field.

Next, the high frequency coil 2 for plasma generation includes matching circuits 14 and 13, and a 56 MHz high frequency oscillator 15.
It is connected to the. Also, the gas supply pipe 3.

It is connected to nitrogen and hydrogen gas cylinders 16 used for nitriding processing and titanium nitride film formation, and is also connected to an argon gas cylinder used for bombardment processing. The pressure inside the vacuum container 1 is reduced to 1 to 10 Torr, nitrogen gas alone or a mixed gas of nitrogen and hydrogen is introduced into the container, and a voltage is applied to the high frequency coil 2 to cause plasma discharge. In the normal ion nitriding method, a cathode (workpiece) and an anode are provided in a low pressure (nitrogen or nitrogen + hydrogen) gas atmosphere of about 1 to 10 Torr, and a DC voltage of 100 to 1500 V is applied between the two electrodes. Generate electrical discharge. Nitrogen ionized by glow discharge is accelerated near the surface of the object to be processed due to rapid cathode fall, and collides with the surface of the object to be processed. At this time, the object to be treated is heated by the high kinetic energy of the ions, and the nitriding process is performed.

The present invention utilizes not only DC glow discharge but also high frequency discharge. Further, since the ions are accelerated by applying a bias voltage in addition to the cathode fall, the ionization rate is higher than that of glow discharge, and since heating is also performed, efficient nitriding can be performed.

Here, the ion nitriding process and the production of a titanium nitride film when 5US304 is used as the object to be treated will be described.

That is, in a mixed gas atmosphere of nitrogen:hydrogen=1:1,
The vacuum was maintained at T o r r, and the object to be treated was heated to 500° C. not only by the collision energy of nitrogen ions but also by a heater. Plasma was generated under these conditions, and a bias voltage of minus 2 to 3 KV was applied to the object to be processed. The ionized N positive ions are accelerated in the NH positive cathode descending section and collide with the surface of the object to be treated.
During the heat transfer process of the nitrogen, the iron atoms ejected by the sputtering action combine with the nitrogen in the plasma to form FeN, which again penetrates into the base material from the surface of the workpiece and nitridation progresses. do. After continuing this treatment for 3 hours, the next ion blating treatment was started. That is, after cutting off the plasma and stopping the gas, switching from vacuuming with a rotary pump to a diffusion pump and maintaining it at a level of 10 Torr, nitrogen: hydrogen = 95:
5 is introduced to generate plasma, and the electron gun 6
was operated to evaporate titanium, and a so-called titanium nitride film formation process was performed.

FIG. 2 is a metallographic diagram after the ion nitriding treatment and titanium nitride film formation obtained in this manner.

On the surface of 5US304, there is a nitrogen diffusion layer of about 50 μm, 2~
There is a 3μm nitride layer, and about 10μm of titanium nitride is added on top of this.
M film was formed, but it was for a wide boundary and there was no clear interface. Therefore, a film with excellent adhesion that was difficult to peel off was formed.

The nitriding treatment conditions are 500 mL in a vacuum of 5 to 6 Torr.
When heated to ~600℃ for 3 to 4 hours, the hardening range is 600μm (surface Hv200) for 815C material, 50M
440 material, 200 μm (surface Hv 620), S
957zm with US 304 material (surface Hv1200)
It is known that this can occur to a certain extent.

Figure 3 is a chart comparing this example and the conventional example, with the horizontal axis representing the film thickness from the base material to the titanium nitride film on the surface and the vertical axis representing the coefficient of linear expansion. This is a chart comparing the present example and the conventional example, with the film thickness from the base material toward the titanium nitride film on the surface taken as the vertical axis, and the hardness taken as the vertical axis. With conventional methods, titanium nitride films change rapidly and are prone to peeling, but when combined with ion nitriding, titanium nitride films can be produced.

The distribution curve becomes gentle, and a film with excellent adhesion that is difficult to peel off can be formed.

Although the case of steel, stainless steel, etc. is exemplified here, it is also possible to use non-ferrous metals, especially aluminum.

〔Effect of the invention〕

According to the present invention, the nitride layer formed on the surface of the workpiece by the surface diffusion method of nitrogen ions and the titanium nitride formed by vapor-depositing titanium on the nitride layer form a wide boundary, so that peeling is possible. A film with excellent adhesion that is difficult to peel is formed, and because the adhesion is improved, it becomes possible to form a thick film of titanium nitride, which was previously impossible, and it is possible to form a film that has long-term wear resistance.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram of a high-frequency ion brating device showing an embodiment of the present invention, Fig. 2 is a metallographic diagram of a film structure according to the present invention, and Fig. 3 is a diagram showing the relationship between film thickness and coefficient of linear expansion. , FIG. 4 is a chart showing the relationship between film thickness and hardness. DESCRIPTION OF SYMBOLS 1... Vacuum container, 2... High frequency coil, 3... Gas supply pipe, 4... Evaporation source, 5... Evaporation metal, 11...
・Substrate holder, 13...DC bias power supply

Claims (1)

[Claims] Plasma is generated in a nitrogen gas atmosphere or a mixed gas atmosphere of nitrogen gas and hydrogen gas, and the nitrogen gas is ionized by glow discharge, accelerated, and collided with the surface of the workpiece to nitride the surface of the workpiece. A method for forming a highly adhesive titanium nitride film, which comprises forming a titanium nitride film on the surface of the object to be treated by generating plasma in the atmosphere and then evaporating titanium after forming a nitrogen diffusion layer and a nitrogen diffusion layer.