JPH01263265A - Vacuum arc deposition method - Google Patents

Abstract

PURPOSE:To obtain a high quality film contg. no molten particles and having superior strength and durability by vacuum arc deposition by specifying the surface temp. of the cathode and the partial pressure of introduced gas and by forming a film on a substrate while forming a compd. having a high m.p. CONSTITUTION:Plasma particles are generated from an evaporating source (cathode) 2 in a vacuum chamber 1 by vacuum arc discharge and deposited on a substrate 8. In this vacuum arc deposition method, the surface of the cathode 2 is kept at 200 deg.C-the m.p. of the cathode material and the partial pressure of introduced gas for forming a compd. having a high m.p. is regulated to >=1X10<-4>Torr. A film is formed on the substrate 8 while forming the compd. on the surface of the cathode 2.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides a vacuum arc method for efficiently forming a high-quality film on a substrate with a small number of molten particles mixed in, and even if they are mixed, the particle size is small. It relates to vapor deposition methods.

[Prior art] Vacuum arc evaporation method uses vacuum arc discharge to generate cathode material particles from an evaporation source (cathode) in a vacuum chamber, and deposits them on a substrate to which a negative bias voltage is applied. In this method, high-energy cathode material atoms are emitted as a plasma beam from the cathode, which is an evaporation source, and are accelerated by the voltage applied between the cathode and the substrate, forming a film on the substrate. As described above, one of the features of the vacuum arc evaporation method is that the energy of the incident particles is high, so it is possible to obtain a film with high density and excellent strength and durability. Another contributing factor is that the strength of the substrate is kept low in comparison. The reason why the vacuum arc evaporation method is attracting attention for practical use is that it has a fast film formation speed, and is used for wear-resistant coatings on cutting tools, bearings, gears, etc., as well as electronic parts, printed circuits, optical equipment, etc. Its use in various fields, such as magnetic devices, is being considered.

[Problems to be Solved by the Invention] As publicly known techniques related to such vacuum arc evaporation technology, known methods such as Japanese Patent Publication No. 58-3033 and Japanese Patent Publication No. 52-14690 have been proposed. Namely, Special Public Interest Publication No. 58-303
3 is one of the fundamental inventions in this field.
An arc discharge is generated between the source material and the anode, and a beam of particles consisting of atoms and ions of the source material is ejected, and an arc discharge current is supplied to each particle.
There is a method that provides kinetic energy of 100 electron volts to deposit the particles on the surface of an object. In addition, in this patent publication, in order to improve beam directivity, the anode was formed into a truncated conical tube shape to determine the beam direction, and the beam width was regulated by controlling its aperture and diameter expansion angle. A device is disclosed, and it is stated that the use of a magnetic field is effective in further increasing directivity.

In addition, Japanese Patent Publication No. 52-14690 describes ``a metal cathode placed on a cooling bed, a trigger electrode that generates a cathode spot on the evaporation surface of the cathode,
In a vacuum metal coating apparatus equipped with an exhaust chamber and an arc power source, the anode is an envelope, the evaporation surface of the cathode faces the envelope space, and the cathode spot holding device limits the evaporation surface of the cathode and the cathode spot. This is a vacuum metal coating device that is arranged near the cathode so as to prevent the transition from the evaporation surface to the non-evaporation surface. By forming the shield member of the device to surround the non-evaporation surface of the cathode), transfer of the arc to the non-evaporation surface is prevented and the utilization rate of the cathode forming material is improved.

However, in conventional vacuum arc evaporation methods including the above two known techniques, in addition to plasma particles consisting of ions and neutrons generated from the cathode evaporation surface, molten particles (macro particles) of the cathode material are produced.

Macro droplets, etc.) are generated and mixed into the deposited film on the substrate, causing deterioration of the film surface roughness and reduction of adhesion.
Furthermore, in the case of a reactive coating film, it is unavoidable that molten particles are incorporated into the film without reacting.

The generation of such molten particles is largely dependent on the stability of the arc, and it is said that the generation can be significantly reduced by increasing the arc stability.

By the way, as stated in the above patent publication, l! The arc that occurs between the l pole and the cathode is caused by a current flowing through a small spot moving over the cathode, and this arc spot moves quickly over the cathode. On the other hand, the plasma particle ejection mechanism from the arc spot does not involve a molten pool, but a small melting point is formed in the arc spot, and during the instantaneous time until the arc spot reaches 8 lines. The molten material evaporates and ionizes to form plasma particles. As the melting point increases and expands, the generation of molten particles becomes significant. Therefore, in order to reduce the incorporation of molten particles into the film, it is desirable to reduce the melting point generated on the cathode surface as much as possible. From this point of view, a method is generally adopted in which the cathode is hung on a cooling bed and forcedly cooled from the back side to limit melting of the cathode surface. However, in spite of adopting these measures, in the conventional technology, the generation of molten particles and their incorporation into the film cannot be avoided, which worsens the film surface roughness and reduces the adhesion of the film, leading to deterioration of the film quality. was.

The present invention has been made in view of these circumstances, and it is possible to efficiently form a high-quality vapor deposited film on a substrate with a small number of mixed molten particles and, even if mixed, the particle size is small. The purpose is to provide a vacuum arc evaporation method.

[Means for Solving the Problems] According to the vacuum arc evaporation method of the present invention, an arc is generated between an anode and a cathode placed in a vacuum chamber, and plasma particles generated from the cathode surface are deposited on a substrate. In the vacuum arc evaporation method, the cathode surface temperature is set to 200°C or higher,
While keeping the temperature below the melting point of the cathode material, a gas that reacts with the cathode material to form a high melting point compound is introduced into the vacuum chamber at a partial pressure of 1 x 10''4 Torr or higher to form a high melting point compound on the cathode surface. The gist is that the film is deposited on the substrate while forming the layer.

[As mentioned above, it is common practice to use forced cooling of the cathode with a coolant such as water for the purpose of improving arc stability, and the cathode surface temperature is kept at around 50°C (at least 2
The temperature was kept low (down to 00°C). That is, when the cathode surface is heated to a high temperature, the cathode material melts due to the concentration of arc energy, and a large amount of melt is formed, resulting in an extremely large number of molten particles.

In contrast, in the present invention, a gas that reacts with the cathode material to form a compound having a higher melting point than the cathode material is introduced into the vacuum chamber to form a high melting point compound layer on the evaporation surface of the cathode material. . Moreover, in the present invention, by restricting the cooling of the cathode, the cathode surface temperature is controlled to 200° C. or more, preferably 500° C. or more, and below the melting point, thereby promoting the reaction between the cathode material and the introduced gas and the diffusion of the reaction product. In particular, in the present invention, since the cathode surface temperature is high, diffusion of the reaction product layer to the deep part proceeds sufficiently, and a thick high melting point compound layer is formed on the cathode surface. As a result, when plasma particles are generated from the arc spot, the molten area around the spot is reduced, and the number of molten particles generated can be significantly reduced without hindering the generation of plasma particles. The particle size can also be reduced.

In order to reliably obtain the effects of the present invention, the cathode surface temperature needs to be 200°C or higher (preferably 500°C or higher), and if it is lower than 200°C, the reaction between the cathode material and the gas and the diffusion of the reaction products will occur. becomes insufficient. On the other hand, if the cathode surface temperature is too high, the cathode material may melt or melt, so the cathode surface temperature must be limited to below the melting point of the cathode material. There are no particular restrictions on the means for controlling the cathode surface temperature, but as arc energy accumulates and the cathode temperature gradually rises, active heating is not necessary, and the degree of cathode cooling using a forced cooling mechanism, etc. It is only necessary to make adjustments, and as the control means, for example, means such as indirect cooling or the use of a cooling structure made of a material with poor thermal conductivity can be applied.

This can also be achieved by increasing the thickness of the cathode and increasing the heat flow resistance.

The pressure of the high melting point compound forming gas introduced into the vacuum chamber must be I x 10-4 Torr or more, excluding the air remaining in the vacuum chamber and the pressure of inert gas that may be introduced separately. , more preferably set to 1 x 1O-3Torr or more,
If the gas partial pressure is lower than this, a high melting point compound cannot be sufficiently formed due to the lack of reactive gas.

[Example] Example 1 Fig. 1 is a schematic diagram showing a vacuum arc evaporation apparatus for implementing the method of the present invention, in which a vacuum arc evaporation source A is installed in a vacuum chamber 1, and a substrate 8 is placed opposite to it. has been established. The vacuum arc evaporation source A consists of a cathode 2 made of Ti with an effective evaporation surface diameter of 50 mm, and a water-cooled cooling bed 6 attached to the back side of the cathode 2 through a heat transfer control plate 5 made of a stainless steel plate. An anode 3 is arranged near the substrate side. Note that 4 represents an arc confinement ring and 10 represents an insulator.

To perform vacuum arc deposition, after reducing the pressure in the vacuum chamber 1 to 1 x 10-4 Torr by an exhaust means (not shown), 1 ton of N2 is pumped from the gas cylinder 11.
x 10-2 Torr, and an arc was generated between the anode 3 and the cathode 2. In this state, increase the arc current to 18O
When held at A, the cathode surface becomes red hot in a few minutes, and the surface temperature reaches 5
00t: It has become more than that. And Ti generated from cathode 2
plasma particles are irradiated onto the substrate and the reactive gas N
2 to form a TiN coating film with a thickness of about 2 μm.

For comparison, a TiN coating film of approximately 2 μm was formed on the substrate using the conventional method of directly cooling the back surface of the cathode 2, and the quality of both films was observed using a scanning electron microscope (SEM). The results are shown in Table 1. was gotten.

Table 1 As shown in Table 1, a significant reduction in the number and size of molten particles could be observed in the examples.

Furthermore, when observing the state of the cathode surface after the coating process was completed, the cathode surface obtained using the conventional method was metallic in color and appeared to show the Ti substrate, whereas the cathode surface in the example was golden in color and the cathode surface It was confirmed that a TiN layer was formed on the surface. In addition, when the cathode surface was observed with an SEM at 300 times magnification after the coating process was completed, it was found that
On the cathode surface produced by the conventional method, the area that appears to be the trace of melting in the arc spot has a diameter of approximately 20 to 50 μm, whereas on the cathode surface produced by the present invention, the trace of the melted region is significantly miniaturized. , the diameter is about 10 μm, the largest one is 2
It was found that the thickness was about 5 μm. This is considered to be because the area melted by the arc spot became smaller due to the effect of the present invention.

By varying the introduced N2 pressure, the result was 1 x 10-4T.
It was clearly possible to obtain the same effect as above above orr. Also, regarding the arc current value, it was confirmed that the cathode surface temperature increased sufficiently within the range of 120 to 200 A.
Since a decrease in the number of molten particles in the film was observed, it can be said that it is desirable to adjust the arc current value within the above range, but the present invention is not limited thereto.

The reason why such excellent effects can be obtained is that, as mentioned above, a high melting point compound layer, which is a reaction product of the cathode material and the reactive gas, is formed on the surface of the cathode. Mere introduction of the compound does not sufficiently form a high melting point compound layer, and the generation of molten particles cannot be significantly suppressed.

However, as shown in the above example, the cathode surface temperature was set to 200
When the temperature is raised above 0.degree. C., the diffusion phenomenon becomes active and a high melting point compound layer with a large penetration depth is formed, and the generation of molten particles is significantly reduced.

In the above embodiment, a stainless steel plate was sandwiched between the cathode and the cooling bed as means for limiting cooling of the cathode, but the same effect can of course be obtained by other methods.

For example, it is effective to make the cooling bed from a material with a small heat transfer coefficient, such as stainless steel, or to use a vacuum arc evaporation source with a structure that reduces the contact area between the cathode and the cooling bed, as shown in Figure 2. It is also effective. It is also effective to increase the cathode surface temperature by increasing the thickness of the cathode itself or by making the cathode from a material with poor thermal conductivity to increase the temperature difference within the cathode itself.

Example 2 In Example 1, Ti was used for the cathode and N2 was used as the reactive gas, but the present invention uses all the cathode materials that can be evaporated by the vacuum arc evaporation method and all the cathode materials that can react with this to form a high melting point compound. It can be used for gases, and examples of cathode materials include Ti (melting point: 1953"K, the same applies hereinafter), Z
r (2123°K), Hf (2495°K), T
a (3273'K), N b (2693°K
).

Vb (2193'K) Nol Vb, a metal of the Vb group, and when reacted with a reactive gas such as N2, CH4, C2H2,02, TiN (3220°
K).

T i C (3340”K), ZrN (325
0'K), Z rC (3690"K), Hf
N (3580'K), Hf C (4220'K).

T a N (3360@K), T a C (427
0°K), NbC (3870°K), V N (
2450'K), V C (2921@K).

T i 02 (2113'K), Z r 02
(2950'K).

Since high melting point compounds such as T1CN and HfCN can be formed, the method of the present invention can be applied to the above combinations.

[Effects of the Invention] The present invention is configured as described above, and it is possible to efficiently form a high-quality film on a substrate with less contamination of molten particles.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an apparatus for carrying out the method of the present invention;
FIG. 2 is a schematic diagram showing another embodiment of the vacuum arc evaporation source. 1...Vacuum chamber 2...Cathode 3...Anode
4...Arc confinement ring 5...Cooling control board 6...Cooling bed 7...Cooling water 8
... Substrate 9 ... Arc power supply 10 ... Insulator 11 ... Gas cylinder Fig. 1 Fig. 2

Claims (1)

[Claims] In the vacuum arc evaporation method, in which an arc is generated between an anode and a cathode placed in a vacuum chamber, and plasma particles ejected from the cathode surface are deposited on a substrate, the cathode surface temperature is kept at 200°C or higher and below the melting point of the cathode material. At the same time, a gas that reacts with the cathode material to form a high melting point compound is introduced into the vacuum chamber at a partial pressure of 1 x 10^-^4 Torr or more to form a high melting point compound layer on the cathode surface. A vacuum arc evaporation method characterized by forming a film on a substrate.