CN1025353C - Plasma treatment method and apparatus - Google Patents

Abstract

A plasma chemical vapor deposition method and equipment are introduced. The device includes a vacuum chamber in which two pairs of electrodes are arranged. A high-frequency voltage is applied to one pair of electrodes to generate a plasma of a reactive gas in a vacuum chamber. The substrate to be coated is disposed between another pair of electrodes. A lower frequency voltage is applied to the other pair of electrodes. By means of this low-frequency voltage, the substrate is bombarded with plasma during the deposition process. The effect of the bombardment is to remove the softer parts of the deposited material.

Description

The invention relates to a plasma treatment method and equipment. More particularly, the present invention relates to, but not exclusively, a method of adhering a protective film of carbonaceous material to a relatively soft substrate to form a transparent, electrically insulating coating on the substrate.

So far, there are many ways to deposit hard and thin diamond-like carbonaceous films on substrates. The term "diamond-like carbon" here refers to carbon so hard that it can neither be cut with a razor blade nor scratched with steel wool, for example. The chemical bonding differs from the triangular bonding of graphite SP ² , and it appears that the diamond-like tetrahedral bonding of SP ³ predominates. Examination of diamond-like carbon films by X-rays may or may not show signs of crystallinity.

Japanese Patent Application Sho 56-146936 describes an example in which the carbon deposition process is carried out simultaneously with the bombardment of the deposited carbon material with accelerated ions, thereby selectively removing the soft material portion and Leaving the harder material behind, this method is technically superior in increasing the hardness of the carbon film thus deposited. But coating a substrate in this way to produce sputtering thereon requires biasing the substrate. The benefits of this approach are therefore somewhat reduced when the substrate is made of insulating material.

It is therefore an object of the present invention to provide a novel plasma processing apparatus and method.

In order to achieve the above and other purposes and advantages, as on both sides of a substrate such as a glass substrate to be processed, in addition to being provided with a pair of electrodes for generating plasma gas in the vacuum chamber, there are also vacuum chambers on both sides of the substrate. Set up another pair of auxiliary electrodes. A low-frequency voltage is applied between the auxiliary electrodes to make plasma ions bombard the substrate.

Hard films can be deposited by plasma treatment because the bombardment of the ions necessarily selectively removes the softer portions of the material deposited during the deposition process. When the carbonaceous film is formed with carbide gas, its hardness and resistivity can be controlled by adding fluoride gas. The fluorine contained in the deposited carbon film also functions to improve the waterproof performance of the carbon film. This carbon film is suitable for use as a protective coating on automotive windows.

Other substrates suitable for treatment with the present ^invention are made of insulating materials such as polyesters, alkyds, oil-free alkyds, unsaturated polyesters, acrylics and amino resin etc. In particular, acrylic varnishes, acrylic melanins and acrylic urethanes are suitable organic materials in the manufacture of automobiles.

The content of the present invention can be better understood by reading the following detailed description in conjunction with the accompanying drawings, in the accompanying drawings:

Fig. 1 is a schematic cross-sectional view of a plasma CVD (chemical vapor deposition) device according to an embodiment of the present invention;

Fig. 2A and 2 (B) are the vertical and horizontal sectional views of the automobile window glass that has been coated with carbon protective film of the present invention;

Fig. 2 (C) is a transverse sectional schematic view of a modification of the embodiment shown in Fig. 2 (A) and 2 (B);

Fig. 3 (A) and 3 (B) are the horizontal and perspective sectional schematic diagrams of a cylinder coated with the carbon protective film of the present invention;

4(A) and 4(B) are a perspective view and a sectional view of a ruler coated with a carbon protective film of the present invention;

5(A) and 5(B) are perspective and sectional views of a square coated with the carbon protective film of the present invention.

Referring now to FIG. 1, there is a schematic diagram of a chemical vapor deposition apparatus. This equipment comprises the following parts: a vacuum chamber 9, wherein a deposition space is formed, a vacuum system 25, comprising a rotary pump 25 and a turbomolecular pump 22, the two pumps are connected to the chamber 7 via a valve 21 , a gas supply system 30, including four gas supply pipelines, each pipeline is provided with a flow meter 29 and a valve 28 connected to the reaction chamber 7, a pair of two-shaped aluminum electrodes 3-1 and 3-2, placed in the deposition space The upper position and the lower position of; A power supply 40, supplying the usefulness that supplies power to mesh electrode 3-1 and 3-2; A plurality of substrate holders 20, for the usefulness of fixing substrate 1, each substrate holder is connected by capacitor 19 On the chamber 7; a plurality of mesh aluminum electrodes 50 (13-n, 13-n'), each electrode is interposed between adjacent substrates, and a bias voltage supply device 17 is supplied to add AC voltage between adjacent electrodes 50 For this purpose, the reaction chamber 7 is equipped with a gate valve 9 through which the substrate to be coated is disposed into the chamber 7 .

The power source 40 includes a first power source 15 - 1 , a second power source 15 - 2 and a phase adjuster 26 . The first power supply 15-1 supplies an AC voltage to the mesh electrode 3-1 via a matching unit 16-1 having an LCR (inductance-capacitance-resistance) circuit. The second power supply 15-2 supplies an AC voltage to the mesh electrode 3-2 via a matching unit 16-2 having an LCR circuit. The phase adjuster 26 is connected between the first power source 15-1 and the second power source 15-2. Both the first and second power sources are grounded at terminals 5-1 and 5-2, respectively. The bias voltage supplier 17 is provided with first and second AC voltage sources 17-1 and 17-2, which supply an AC voltage between each adjacent electrode 13-n, and 13-n'. One terminal of the voltage sources 17-1 and 17-2 is grounded at 5-3.

In operation, after the chamber 7 is evacuated, carbide gas is introduced into the deposition space 8 at 0.001 to 1 Torr. For example, the carbide gas is composed of _C2F6 and _C2H4 in a ratio of 1:4 to 4: ₁ (for example, 1:1), and _the carbide gas is passed into the chamber 7 so that the pressure in the chamber 7 becomes 0.5 Torr. The _transparency and resistivity of _the carbon material can be controlled by changing the fluorine content contained in the carbon material to be deposited by adjusting the introduction rate of _C2F6 relative to _C2H4 . The temperature of the deposition space shall not be higher than 150°C. An AC voltage of 1 MHz to 100 MHz (for example, 13.56 MHz) is applied to the grid voltages 3-1 and 3-2 from the first power source 15-1 and the second power source 15-2. The phase difference between the above voltages is adjusted to 0° or 180° by a phase modulator 26 . The carbide gas is converted into a plasma state by means of high-frequency voltage, and carbon is deposited on the substrate. The deposition rate is 100 to 1000 Angstroms/min. The carbon film can be deposited to a thickness of 0.1 to 8 microns on a flat surface, and can be deposited to a thickness of 1 to 3 microns on a convex surface. At the same time, an AC voltage is applied between the respective adjacent electrodes 13-n and 13-n' to induce an electric field perpendicular to the respective substrates. The frequency of the AC voltage between the electrodes 13-n and 13-n' is selected in the range between 10 Hz and 100 kHz, for example 50 Hz. At such low frequencies, the ions of the plasma can follow the electric field to bombard the surface of the substrate on which carbon is to be deposited. Therefore, the hardness of the deposited carbon material is high, for example, 600 to 6000 kg/mm2. The resistivity of carbon is, for example, from 1 x 10 ⁶ to 5 x 10 ¹² ohm cm, typically 1 x 10 ⁷ to 1 x 10 ¹¹ ohm cm. The optical energy bandgap is not narrower than 1.0 eV, generally 1.5 to 5.5 eV. The carbon material contains 30 atomic % or less of hydrogen and 0.3 to 10 atomic % of fluorine.

Carbonaceous thin films are coated on some substrates according to the present invention. Figures 2(A) and 2(B) are horizontal and vertical cross-sectional views of a curved glass or plastic pane 1 coated with a carbonaceous film 45 of 0.1 to 8 microns thick, ready to be fitted to a vehicle front window. The entire surface of the pane 1 is coated with the carbon film of the present invention. The carbon film can be applied to only one side of the pane. In this case, the panes of glass processed in the apparatus shown in Fig. 1 are arranged parallel to each other so that they are paired as shown in Fig. 2(c). Figures 3(A) and 3(B) illustrate carbon coating layers formed on a cylindrical substrate. 4(A) and 4(B) illustrate carbon coating layers formed on the plastic ruler 1 . painted The thickness of the cladding layer 41 is, for example, 0.1 to 8 micrometers. 5(A) and 5(B) illustrate carbon coating layers formed on a square. The coating layer has a thickness of 0.5 microns.

Although several embodiments have been specifically described herein by way of example, it should be understood that the invention is not limited to the individual examples described, and that the invention is described in the claims appended hereto without departing from the invention. Various modifications and changes are possible within the scope. For example, the invention can be applied to coat front windows, side windows or rear windows or side mirrors with a carbon protective film.

Claims (12)

1. A plasma processing device, characterized in that the device comprises: - vacuum chamber; - a vacuum pump connected to said vacuum chamber to evacuate said vacuum chamber; - a gas introduction system, connected to said vacuum chamber, for introducing reaction gases into said vacuum chamber; - for the first electrode, located in said vacuum chamber; - a first voltage source for applying a first high-frequency alternating voltage between said first electrodes to convert the reaction gas in said vacuum chamber into plasma; - a substrate holder, used to support the substrate to be processed by the apparatus between the first electrodes; at least one pair of second electrodes configured such that a substrate supported by the substrate holder is located between the second electrodes, insulated from the substrate and spatially separated from the second electrodes; and - a second voltage source for applying a second alternating voltage between said second electrodes to enhance sputtering of said substrate surface. 2. The device according to claim 1, wherein the frequency of the first AC voltage is selected from the range of 1 MHz to 50 MHz. 3. The device according to claim 2, characterized in that the frequency of the second AC voltage is selected from the range of 10 Hz to 100 kHz. 4. The apparatus of claim 3, wherein said substrate holder is adapted to support a plurality of substrates so that said substrates are spaced apart from each other and arranged in parallel. 5. The apparatus of claim 4, wherein said second electrodes are respectively disposed between adjacent substrates of said substrates. 6. The apparatus of claim 1, wherein said at least one substrate is disposed perpendicular to said first electrode and parallel to said second electrode. 7. The apparatus of claim 1 wherein said substrate is comprised of an insulating material. 8. The apparatus of claim 7, wherein said substrate is a vehicle window. 9. The apparatus of claim 7, wherein said insulating material is selected from polyester, alkyd, unsaturated polyester, acrylic and amino resins. 10. The apparatus of claim 1, wherein said substrate holder is insulated from said reaction chamber by means of a capacitor. 11. The apparatus of claim 1, wherein said plasma treatment is an etching process. 12. The apparatus of claim 1, wherein said plasma treatment is a deposition process.

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