JPS60248703A - Plasma cvd device - Google Patents

Abstract

PURPOSE:To improve controllability of plasma, and to stabilize film-forming conditions, by making plasma exist in the vicinity of a plasma outlet of a plasma generation pipe. CONSTITUTION:The plasma generation pipe 23 having the plasma outlet 32 in a tapered shape at the end is inserted into the vacuum tank 21, the induction coil 27 is wound round the outside face 24 in atmosphere to set a means to provide high-frequency power, and one or more of the gas inlet pipes 29 are set in the outside face 28 in vacuum of the plasma generation pipe 23. And the cylindrical can 33 is laid in the vicinity of the plasma outlet 32, and coating is carried out on the surface of the sheet 35 transferring along the peripheral face 34 of the cylindrical can 33 by gaseous-phase growth of plasma chemistry. USE:Suitable for surface protecting coating of a sheet substrate such as magnetic recording medium, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a plasma CVD apparatus for applying a surface protective coating to a sheet-like substrate such as a magnetic recording medium.

Conventional Structure and Problems As a thin film forming technology for LSI manufacturing process, discharge plasma CVD method using RF plasma excitation has recently been put into practical use as a highly reliable pansivation film technology for silicon nitride films and the like. On the other hand, this technology is also being applied to surface protective coatings for tape magnetic recording media and disk-shaped magnetic recording media that require durability, abrasion resistance, lubricity, etc.

The RF discharge plasma CVD method can be divided into two types: (1) parallel plate electrode structure type and (2) induction coil type. In the former case, the substrate to be coated is placed on one of the flat electrodes, and as the substrate is directly exposed to the plasma, the surface of the substrate may be damaged due to impact from ions in the plasma or heating due to the injection of electrons. However, there were drawbacks such as a decrease in vapor deposition efficiency due to the lack of etching action. Furthermore, the deposited substance also adheres to the electrode surface, and the electrical conditions of the parallel plate electrodes that form a capacitance in the electrical circuit change as the film adheres, resulting in a drawback that the discharge conditions change over time. Furthermore, when applying this to a surface protective coating on a sheet-like substrate, it can be applied to a wide range of areas, from the sparse area at the periphery of the plasma generated between parallel plate electrodes to the high density area of the plasma at the center. Since the moving sheet is exposed, the film forming conditions cannot be kept constant.

The present invention belongs to the latter of the above two categories of RF discharge plasma CVD methods, that is, the induction coil type. Although this induction coil type also has less change in electrical conditions over time than the parallel plate electrode type, The structure has the same drawbacks as above. Figures 1 and 2 show examples of conventional configurations of such induction coil types, with Figure 1 having the induction coil 1 in a vacuum, and Figure 2 having the induction coil 11 outside the vacuum. This is an example of having Vacuum tank 2 (or reaction tube 12)
is evacuated by the exhaust system 3 (13), and a reactive gas is introduced into the vacuum from the gas introduction valve 4 (, 14).
Discharge is performed under a reactive gas pressure of about o-2 to 10' Torr. The discharge is carried out by induction coil 1 (11), which connects the output of high frequency radio wave 5 (16) through matching circuit 6 (16).
) is carried out by The pressure inside the vacuum chamber or reaction tube is known by the vacuum gauge 8 (18) connected to the vacuum gauge 7 (17). By placing the substrate 9 (19) at a predetermined location in a vacuum chamber or reaction tube, a film is formed on the surface of the substrate by plasma chemical vapor deposition. In such a conventional configuration, as described above, there are inconveniences caused by the substrate being in direct contact with plasma, and it is difficult to maintain constant film forming conditions when forming a film on a moving tape.

Purpose of the Invention The present invention solves the drawbacks shown in the conventional examples, and provides a plasma CVD method which is convenient for coating sheet-like substrates such as magnetic recording media and which can stabilize film-forming conditions.
It provides equipment.

Structure of the Invention The present invention involves inserting a plasma generation tube having a plasma outlet with a narrowed tip into a vacuum chamber from outside the vacuum chamber, and winding an induction coil around the outer surface of the plasma generation tube in the atmosphere to generate high-frequency power. The plasma generating tube has a reactive gas inlet on the outer surface in vacuum, and a cylindrical can is disposed near the plasma outlet, and a reactive gas inlet is provided on the outer surface of the plasma generating tube in vacuum. It is characterized by applying a coating to the surface of the sheet that moves along it by plasma chemical vapor deposition.

DESCRIPTION OF EMBODIMENTS A detailed description will now be given according to embodiments of the present invention. Third
The figure shows a plasma CVD apparatus showing an embodiment of the present invention, in which a vacuum chamber 21 is evacuated by an exhaust system 22 consisting of an oil rotary pump, a mechanical booster, an oil diffusion pump, and a cooling trap. An induction coil 27 connected to a high frequency power source 25 and a matching circuit 26 is wound around the outer surface 24 of the generation tube 23 in the atmosphere.
Supply high frequency power to the plasma generation tube. A reactive gas inlet 29 is provided on the outer surface 28 of the plasma generating tube inside the vacuum.
is provided, and the reactive gas that has passed through the gas introduction valve 30 is introduced into the plasma generation tube through the tube 31. There is a plasma outlet 22 in the shape of a constricted tube at the tip of the plasma generating tube inside the vacuum chamber, and a sheet 3 moves along the circumferential side surface 34 of a cylindrical can 32 arranged near this outlet.
A coating is applied to the surface of 6 by plasma chemical vapor deposition. The sheet is fed to the supply roller 36. Post roller 37
, a can 33 and a take-up roller 38. The gas pressure inside the plasma generation tube is measured by vacuum gauge 3.
9 is connected to the vacuum gauge 40, and if necessary, an inert gas is introduced from the other gas introduction valve 41 and introduction port 42 provided in the plasma generation tube to adjust the discharge conditions.

In the example, organic monomer gas C4F was used as the reactive gas.
By introducing 8 and polymerizing a Teflon-based organic polymer film on the surface of the magnetic sheet, a protective film with a large contact angle with water and excellent running performance under environments such as high temperature and high humidity, and room temperature and low humidity is created. was able to form. PET as a magnetic sheet
A metal vapor-deposited sheet with a width of 150 trah on which Co-Ni was vapor-deposited was moved along a cylindrical can with a diameter of 500 m, and a 135 m x 12 mm plasma generation tube was placed at the tip of a plasma generation tube made of quartz glass with a tube diameter of 140 m. A rectangular opening was provided and placed close to the magnetic surface of the magnetic sheet. Factors that determine film forming conditions include the type of reactive gas, the mixing ratio of inert gases if used together, and the gas pressure in the plasma generation tube.

These include the RF power supply, gas flow rate, the shape of the outlet of the plasma generating tube, and the positional relationship between the can and the like. Once the exhaust capacity of the vacuum device and the shape and arrangement of the plasma generation tube in the 7-door configuration are determined, a steady flow of gas is generated by introducing the gas, and a constant pressure difference is created between the plasma generation tube and the vacuum chamber. arise. In this example, the ratio of the pressure inside the plasma generation tube to the pressure inside the vacuum chamber was about 10 times. Because of this pressure difference, even under conditions where plasma is generated inside the plasma generation tube, the plasma outlet of the plasma generation tube Since the inside of the vacuum chamber is a dilute gas pressure atmosphere except for the vicinity of , plasma is not generated, and the plasma involved in film formation can be limited to the vicinity of the outlet of the plasma generation tube.

When the above-mentioned film-forming conditions are kept constant in this way, a film of constant quality and quantity can be formed as long as the introduced gas pressure and the supplied power are determined. FIG. 4 shows actual measurement data of film thickness versus gas pressure when plasma polymerization of a Teflon polymer film using C4F8 gas was performed using the plasma CVD apparatus of this example. To facilitate film thickness evaluation, a thick film was formed on the side window while the sheet remained stationary for a certain period of time (5 minutes), and the film thickness was measured using an ellipsometer. There is a gas pressure condition that provides the maximum film thickness, and at higher gas pressures, the film thickness decreases approximately in proportion to the gas pressure. This is thought to be because the mean free path of ions and electrons near the outlet decreases as the pressure increases, making it difficult for plasma involved in polymerization to reach the sheet surface. Further, at a pressure lower than the gas pressure condition that gives the maximum film thickness, the film thickness decreases rapidly and no film can be formed, but this is thought to be because the plasma density decreases as the gas pressure decreases. In the region where the power is low, the film thickness increases almost in proportion to the power supplied; when the limit is exceeded, etching begins to occur and the film tends to saturate; when excessive power is applied, etching progresses and the film partially disappears. There will be parts that are missing.

It is known that etching occurs under such high power conditions as a phenomenon unique to the polymerization of fluorine gases. The above relationship between film thickness and gas pressure and supplied power shows good reproducibility as long as the hard conditions are constant. Furthermore, no deformation of the substrate due to thermal effects was observed within a range where the supplied power was not excessively large.

Effects of the Invention As described above, according to the present invention, by localizing the plasma involved in film formation near the plasma outlet of the plasma generation tube, the controllability of the plasma is good, and therefore, certain film formation conditions can be stabilized. Plasma CVD is particularly suitable for surface protective coating of sheet-like substrates such as magnetic recording media.
It provides a device that has great practical value.

[Brief explanation of drawings]

Figures 1 and 2 are a principle diagram of an induction coil type plasma CVD apparatus in a conventional example, Figure 3 is a principle diagram of a plasma CVD apparatus in an embodiment of the present invention, and Figure 4 is a gas pressure diagram of the same apparatus. FIG. 3 is a characteristic diagram showing the relationship of film thickness to . 21... Vacuum chamber, 23... Plasma generation tube, 27... Induction coil, 29... Gas inlet, 32... Plasma blower Exit, 33...
...Cylindrical can, 35... Seat. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 4

Claims (3)

[Claims] (1) It has a plasma generation tube inserted into a vacuum chamber, and has means for supplying high-frequency power by winding an induction coil around the outer surface of the plasma generation tube in the atmosphere, and the plasma generation tube has a vacuum At least one gas inlet on the outside surface of the inside,
A cylindrical can is disposed near the plasma outlet in the vacuum chamber, and the surface of the sheet moves along the circumferential side of the cylindrical can. A plasma CVD apparatus characterized in that a coating is applied by plasma chemical vapor deposition of an introduced gas. (2) The plasma CVD apparatus according to claim 1, wherein the introduced gas is an organic monomer gas, and a polymer film is formed on the surface of the sheet by plasma polymerization. (3) The plasma CV according to claim 2, wherein the introduced gas is a fluorine-containing organic monomer gas.
D device.