JP2844771B2 - Plasma CVD equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a plasma CVD apparatus suitable for coating the inner surface of a tubular substrate, particularly a tubular substrate having a complicated shape.

[Prior art] In recent years, it has been active to improve the corrosion resistance and abrasion resistance of the substrate surface by coating the inner surface of the tubular substrate with ceramics, metal, etc., and to improve the safety and reliability of the substrate. As it has been done, this coating has been carried out in an apparatus as shown in FIG. In the figure, reference numeral 10 denotes a vacuum container, and a nozzle 3 connected to the tip of a source gas supply pipe protrudes from the bottom of the vacuum container 10 at the center thereof. As shown in the figure, a plurality of fine holes 3 ′ which are arranged in a pipe shape and communicate with the inside and outside of the nozzle 3 are arranged radially and vertically in a pipe-shaped manner from the upper end to the lower end of the substrate 1 as shown in the figure. Formed uniformly. An insulator 7 is installed coaxially around the nozzle 3 having the plurality of pores 3 ′ at the bottom of the vacuum vessel 10, and the substrate 1 to be coated is placed on the insulator 7. Support 5
Is fixed. Reference numeral 4 denotes a heater provided outside the vacuum vessel 10, and reference numeral 11 denotes an exhaust pipe provided at the bottom of the vacuum vessel 10.

The nozzle 3 is made of metal and is grounded, and the conductive support 5 is connected to a high frequency power supply 8.

The substrate 1 to be coated is placed on the insulated support 5.
Is placed, the vacuum container 10 is closed, vacuum is evacuated through the exhaust pipe 11, the raw material gas is supplied from the nozzle 3, this is blown out from the fine hole 3 ', and the high frequency power supply 8 is applied.
And the nozzle 3 become an electrode to generate glow discharge, react and decompose the raw material gas introduced through the pores 3 ′,
A thin film can be formed on the inner surface of the substrate.

Further, as another method, there is a method in which a thin film is coated while giving a rotating motion to a tubular substrate to be coated in plasma.

[Problems to be Solved by the Invention] In the conventional plasma CVD apparatus, the source gas is excited and activated by glow discharge generated between the high-frequency electrode (tubular substrate to be coated) and the counter electrode (nozzle). Therefore, in order to obtain a high quality thin film,
If the activation is to be increased, the intensity of the glow discharge must be increased, which has the disadvantage of requiring a very high input power. On the other hand, if the input power is increased, the substrate to be coated is heated by the glow discharge, and there is a problem that the substrate to be coated is thermally damaged.

Means for Solving the Problems The present invention has been made to solve the above problems, and reacts and decomposes a gas introduced from a nozzle by a glow discharge in a vacuum vessel to form a substrate surface to be coated. In the plasma CVD apparatus for forming a thin film, the nozzle has a pipe shape protruding from the center of the vacuum vessel, and a plurality of fine holes are formed radially and uniformly in the vertical direction, and surround the nozzle. A mesh electrode is arranged coaxially, and further, a substrate to be coated is placed coaxially around the outer periphery of the mesh electrode, the nozzle is grounded, the mesh electrode is connected to a high-frequency power source, and A DC power source is connected to the substrate to be coated so that a negative potential can be applied to the mesh electrode, and a heater is provided outside or inside the vacuum vessel. is there.

Hereinafter, the present invention will be described with reference to the embodiment shown in FIG. The figure shows an example of a schematic diagram of the device of the present invention, and the same parts as those in FIG. Vacuum container as shown
The nozzle 3, the mesh electrode 2, and the substrate to be coated support 5 are coaxially arranged in this order from the center of the inside of 10. The nozzle 3 is connected to the tip of the source gas supply pipe, has a pipe shape having a large number of pores 3 'like the conventional apparatus shown in FIG. 2, and is arranged so as to protrude from the center of the vacuum vessel. A conductive mesh electrode support 6 supported by an insulator 7 from the bottom of the vacuum vessel is mounted coaxially around the nozzle 3, and a metal mesh electrode is placed on the support 6. 2 is fixed. A conductive coated substrate support 5 fixed on an insulator 7 is arranged on the outer periphery of the mesh electrode so that the tubular coated substrate can be placed coaxially.

One terminal of the high frequency power supply 8 is connected to the mesh electrode support 6, and the other terminal is grounded. The negative terminal of the variable voltage DC power supply 9 is connected to the substrate 5 to be coated, and the positive terminal is grounded. The nozzle 3 is grounded as shown in the figure.

The vacuum vessel equipped with these components is configured so that the temperature can be raised and maintained to a predetermined temperature by a heater 4 provided outside the vacuum container. A glow discharge occurs between the electrode 2 and the substrate 1, and a pore 3 ′ provided in the nozzle 3
The raw material gas blown out passes through the mesh of the mesh electrode 2 and is excited and activated to reach the surface of the substrate 1 to form a thin film.

[Operation] As described above, the nozzle 3 has a large number of pores 3 ′, and the supply of ions, free electrons, and the like is actively performed from the pore walls, so that the excitation of the source gas and the high Activation is achieved. In addition, during coating, a high-frequency voltage is applied to the mesh electrode, a negative voltage is applied to the substrate to be coated, and a glow discharge is caused between them. Thermal damage can be avoided.

By the way, regarding the mesh size of the mesh electrode, if the size is too large, a mesh pattern is formed on the thin film. Therefore, it is appropriate to use an eye size of 50 mm or less on one side.

Also, the ratio between the distance d ₂ between the distance d ₁ and the mesh electrode and the nozzle of the coating base material and the mesh electrode is Ikase the effect of hollow cathode discharge, and it is the degree of mesh pattern is not formed on the thin film.

In this regard, experiments were conducted on the adhesion and color tone of the TiN coating by changing the ratio.

50mm diameter, 44mm inner diameter, length as substrate to be coated
A 500 mm stainless steel pipe was used, the mesh electrode mesh size was 5 mm, and TiCl ₄ and NH ₃ were used as source gases. Then, changing the ratio, 0.3 Torr
In a container evacuated to -10,
A DC voltage of 0 V is applied, and an output of 13.
The adhesion and color tone of the TiN film coated by applying a high frequency power of MHz were evaluated under each condition. Table 1 shows the results.

As shown in Table 1, when the ratio of d ₁ to d ₂ is 1:20 to 20: 1, a high-quality thin film having a high adhesion and a glossy golden color in appearance is formed. I understand. The ratio is 1:
In the case of 30, the adhesion is low and the color tone is poor, and a mesh pattern is formed on the thin film. Contrary to the above, when the ratio was 30: 1, no mesh pattern was formed on the thin film, but the adhesion was low and the color tone was poor.

[Trial Production Example] A trial production example of a TiN film by the plasma CVD apparatus of the present invention will be described below.

A stainless steel pipe having a length of 500 mm, an outer diameter of 50 mm, and an inner diameter of 44 mm was used as a substrate to be coated, and a metal mesh electrode having a diameter of 30 mm and an eye size of 5 mm was used in a ratio of d ₁ : d ₂ of 1: 1.
After being set on the supports 7 and 6 respectively so that
The high frequency power supply was connected to the mesh electrode support, the DC power supply was connected to the support for the substrate to be coated on which the stainless steel pipe was mounted, and the nozzle was grounded.

The inside of the container is evacuated to 0.3 Torr, and the temperature is raised to a predetermined temperature by an external heater. Before coating,
Ar gas was introduced up to 0.1 Torr through a nozzle, −1000 V was applied to the stainless steel pipe, and the inside of the pipe was cleaned by DC discharge. After cleaning, a high frequency of 13.56 MHz was applied to the mesh electrode while applying a DC voltage of minus 100 V to the stainless steel pipe, and TiCl ₄ and NH ₃ were supplied as raw material gases from the nozzle to perform TiN coating. The surface temperature of the stainless steel pipe at this time was 50
It was 0 ° C.

As a result of performing the TiN coating in this manner, the film thickness is a uniform thickness of 2 to 3 μm, and has a golden golden appearance, and the adhesion is as high as 30 ± 5 N over the entire length of the stainless steel pipe. Indicated.

When TiN coating is performed by glow discharge between the substrate to be coated and the nozzle as in the conventional device without using a mesh electrode, the thin film has uneven gloss due to the influence of the electric field, and the degree of adhesion is 20 N or less. there were.

[Effects of the Invention] As described above, since the supply of ions, free electrons, and the like is actively performed from the pores formed in the nozzle, the source gas is excited and highly activated. Is applied, a negative voltage is applied to the substrate to be coated, and a glow discharge is performed between them, so that the substrate to be coated has a low temperature and thermal damage can be avoided. For this reason, compared to a conventional plasma CVD device that applies a high frequency to the substrate to be coated and causes glow discharge between the nozzle and the nozzle to perform coating, the substrate to be coated is kept at a lower temperature with the same power consumption. A high quality thin film having high adhesion, high hardness and good color tone can be formed.

In particular, even when the substrate to be coated has a complicated tubular shape, a high-quality thin film can be formed by the present invention.

[Brief description of the drawings]

FIG. 1 is a schematic view of an apparatus according to an embodiment of the present invention, and FIG. 2 is a schematic view of a conventional apparatus. 1 ... substrate to be coated, 2 ... mesh electrode, 3 ...
... nozzle, 3 '... pore, 4 ... heater, 5 ... substrate to be coated, 6 ... mesh electrode support, 7
…… Insulator, 8… High frequency power supply, 9… DC power supply, 10…
... Vacuum container, 11 ... Exhaust pipe.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yo Doi 1-1-1, Konokita, Itami-shi, Hyogo Pref. Itami Works, Sumitomo Electric Industries, Ltd. (58) Fields surveyed (Int. Cl. ⁶ , DB name) C23C 16/00-16/56

Claims (1)

(57) [Claims] In a plasma CVD apparatus for reacting and decomposing a gas introduced from a nozzle by glow discharge in a vacuum vessel to form a thin film on a surface of a substrate to be coated, a large number of pores are radially formed in the vacuum vessel. A pipe-shaped nozzle formed uniformly in the length direction is arranged, a mesh electrode is arranged coaxially around the nozzle, and a substrate to be coated can be arranged coaxially outside the mesh electrode. ,
The nozzle is grounded and a high-frequency power supply is connected to the mesh electrode so that a negative potential is applied to the substrate to be coated, a heater is provided outside or inside the vacuum vessel, and the mesh size of the mesh of the mesh electrode is reduced. A plasma CVD apparatus characterized in that the ratio of the distance between the substrate to be coated and the mesh electrode and the distance between the mesh electrode and the nozzle is 20: 1 to 1:20.