JPH1017691A - Method and apparatus for forming thin film on polymer substrate by plasma cvd - Google Patents

Abstract

PROBLEM TO BE SOLVED: To give an improved surface hardness to the surface of a plastics without detriment to its decorativeness by building up a thin transparent SiO2 film on the surface by utilizing the ECR plasma CVD technique by which low- temperature buildup of a high-quality film is possible. SOLUTION: A magnetic field is applied in a plasma generation 1 chamber by using a magnetic coil 2 surrounding the chamber 1. An upstream gas is introduced into the chamber 1 to generate an ECR plasma, and the starting material is evaporated to form a feed gas in an downstream zone. The feed gas is fed from a feed port 6. The ECR plasma is passed through a mesh 14a set between the port 6 and a polymer substrate 7 or between the chamber 1 and the port 6 and a mesh 14b set near the substrate 7 to build up an SiO2 film on the surface of the substrate 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a thin film on a polymer substrate by plasma CVD.

[0002]

2. Description of the Related Art In the era of the demand for high-performance and eco-friendly automobiles, the use of plastic parts for automobiles has been promoted, and fuel economy has been improved by reducing the weight of automobiles. In particular, thermoplastic plastic has attracted attention as an easily recyclable material, and its active use in automotive parts has been attempted. However, plastic materials have lower mechanical strength and surface hardness than metal materials and are inferior in scratch resistance. Furthermore, the surface is discolored and weakened by the ultraviolet rays and heat of the sun, and the weather resistance is never good. Considering the functions and quality of automobiles, there are limits to the parts that can be used with plastic. In the future, unless the plastic is subjected to some surface treatment to improve its function,
No progress in plastic parts is expected.

As a plastic surface treatment method as described above, a thin film forming method by plasma CVD has been conventionally performed. According to the plasma CVD, a substrate temperature of 4
By heating to 00 ° C. or higher to remove impurities in the SiO ₂ film can be coated a high quality SiO ₂ film. However, it was not possible to coat a plastic with low heat resistance (Sunil Wikramanayaka, Yoshinori Hatanaka et al., IEICE, Technical Report, Vol.93, p.91-86, '93
Year). Therefore, the polymer substrate is first treated with a non-polymerizable gas, for example, CO, H ₂ , O ₂ in the same plasma device to increase the adhesiveness of the film, and then subjected to plasma polymerization of the organosilicon compound. And a method for forming a plasma-polymerized film having excellent durability. However, the thin film has excellent adhesion to the substrate, but is an impurity.
Since it contains a large amount of carbon and water, there is a problem that it does not have much hardness and has poor scratch resistance.
No. 2-132940). On the other hand, when a reaction gas is introduced into a vacuum reaction chamber, a magnetic field of 875 Gauss is applied, and a microwave is applied, electrons in the plasma are accelerated by an electron field due to an electron cyclotron resonance (ECR) effect, and a high-density plasma is formed. E that can be generated and uses this
A CR plasma apparatus was developed (Japanese Patent Laid-Open No. 56-1555).
No. 35).

However, in the above-mentioned conventional method, a large amount of supplied gas is used, so that the running cost is high, the apparatus is very dirty, and maintenance is troublesome and costly. Also, it takes a lot of time to form a film,
There is a problem that heat is still applied to the plastic substrate, the damage of the substrate is increased, and residual strain and cracks are generated in the coating.

[0005] Therefore, an EC capable of depositing a high quality film at a low temperature is used.
R Plasma CVD (Electron Resonance Cyclotron Resonance Plasma Chemical Vapor Deposition, Electron Cycrotron Resonance Plasma
Thin film formation by plasma CVD on a polymer base material using Assisted Chemical Vapor Deposition) technology to deposit a thin transparent SiO ₂ film on the plastic surface and improve the surface hardness without impairing the design Method and apparatus developed (Japanese Patent Application No. 8-52580)
issue). In this device, a mesh is installed between the plasma generation chamber and the inlet of the supply gas. The mesh captures electrons in the plasma, escapes to the ground, and passes only radicals (neutrons) in the plasma. The film forming speed is improved. However, even in the technique using the mesh, all the valence electrons in the plasma cannot flow into the ground, and the valence electrons (hydrogen ions) diffused beyond the mesh are deposited on the substrate surface.
The O ₂ film was etched, which had an adverse effect on the deposition rate of the film.

[0006]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a plasma CV to a polymer base material in which valence electrons are reliably supplied to the ground and the deposition rate of the film is improved.
D to provide a thin film forming method and apparatus.

[0007]

According to a first aspect of the present invention, there is provided a method of forming a thin film on a polymer substrate by plasma CVD, wherein the magnetic coil is disposed around a plasma generation chamber. A magnetic field is applied to the plasma generation chamber, microwaves are introduced into the plasma generation chamber, an upstream gas is introduced into the plasma generation chamber to generate ECR plasma, and raw materials are vaporized downstream to generate a supply gas. Then, the supply gas is supplied from the inlet, and further, a mesh provided between the inlet and the polymer base or between the plasma generation chamber and the inlet, and the inlet and the polymer base And the ECR plasma is passed through a mesh set at a position closer to the polymer substrate than the mesh, whereby S O ₂ film characterized by comprising so as to deposit a.

According to a second aspect of the present invention, in a thin film forming apparatus for performing plasma CVD on a polymer base material, a magnetic field is applied by a magnetic coil arranged around the thin film to introduce microwaves and upstream gas. A plasma generating chamber for generating ECR plasma to be introduced, an inlet for supplying a supply gas downstream, and a space between the inlet and the polymer substrate or between the plasma generating chamber and the It is characterized in that it includes a mesh provided between the inlet and an inlet, and a mesh provided closer to the polymer base material than the mesh in addition to the mesh.

[0009]

FIG. 1 shows an embodiment of an apparatus used for a method for forming a thin film on a polymer substrate by plasma CVD according to the present invention. This device is a horizontal EC
In an R plasma CVD apparatus, a magnetic coil 2 is arranged around a plasma generation chamber 1, a magnetic field that is an ECR condition is applied to the inside of the plasma generation chamber 1, microwaves are introduced into the generation chamber 1, and plasma is generated. . 3a is a quartz glass. The magnetic field distribution of the magnetic coil 2 is of a divergent magnetic field type that decreases from the plasma generation chamber 1 to the sample chamber 4. The upstream gas is flow-controlled by the mass flow controller and introduced into the plasma generation chamber 5 to generate ECR plasma.

[0010] The raw material liquid is heated downstream thereof.
The gas is vaporized and the flow rate of the gas is controlled so that the ring-shaped inlet 6
From PC (polycarbonate resin) or
Polymer base material 7 such as PP (polypropylene) (Plastic
Substrate) _TwoFilm can be deposited
You. The source gas supply system 8 includes a source gas tank 9,
Source gas supply line 10, purge gas supply line 11,
And the MFC device 12. In this device 12, gas supply
Primary storage of source gas from line 10 in source gas tank 9
This raw material gas is stored from the purge gas supply line 11.
Purge gas (N _Two) And the MFC device 12 to mix
The amount is supplied from the inlet 6 via the supply line 13.
As shown in FIG. 2, the inlet 6 is provided on the inner peripheral surface of the ring tube.
Are provided with a plurality of small holes 6a.
So that the water flows out evenly. Thus, the book
The original of the plastic substrate 7 to which the invention is applied
Materials include polycarbonate (PC), polypropylene
(PP), polyethylene (PE), polystyrene (P
Polymers such as S) can be mentioned. It is also deposited
Monosilane, tetramethyl
Silane, hexamethyldisilane, tetraethoxysilane
And other Si-containing compounds. Upst
The gas supplied to the room is O_Two, CO, H_Two,
He, Ar and the like can be mentioned.

Further, in this apparatus, a circular mesh 14A connected to the ground is provided between the ring-shaped supply gas inlet 6 and the substrate 7, and a similar circular mesh 14B is provided between the inlet 6 and the polymer substrate 7. And is provided at a position closer to the substrate 7 than the mesh 14A. That is, in addition to the circular mesh 14A, this device
A circular mesh 14 </ b> B provided between A and the substrate 7 is provided. The meshes 14A and 14B are generally made of metal (preferably stainless steel), and are grounded or applied with DC positive and negative voltages. Those indicated by 15A and 15B are DC power supplies. Mesh 14A and 14
B has a role of catching electrons in the plasma, escaping to the ground, and passing only radicals (neutrons) in the plasma, so that the diameter of the mesh and the size of the wire thickness grid are important. Mesh 14A and 14B
Must be greater than the diameter of the ring-shaped feed gas inlet 6 and the diameter of the plasma stream 16 at this point where it is generated. For example, meshes 14A and 14B
When made of stainless steel wire, if the wire is too thick, the shadow of the wire will be transferred to the surface of the formed film, and it will be uneven,
It must be thin to some extent. Therefore, the diameter of the wire is preferably φ0.1 mm or more and 1 mm or less.

If the lattice size of the meshes 14A and 14B is too large, electrons in the plasma cannot be trapped,
Since the radicals pass through the meshes 14A and 14B together with the radicals, they must be reduced to some extent. Therefore, it is preferably 5 mm × 5 mm or less. However, the shape of the lattice is not limited and may be, for example, an octagon,
It is preferable that one grid has an area size of 25 mm ² or less. The matching of the positions of the meshes 14A and 14B installed in the ECR plasma CVD apparatus and the positional relationship between the ring-shaped supply gas inlet 6 and the substrate 7 (plastic, metal, ceramics, and materials are not particularly limited) is based on the SiO ₂ film. This is important for low-temperature high-speed formation. The position where the mesh 14A is installed is not close to the substrate side of the ring-shaped supply gas inlet 6, but the closer to the ring-shaped supply gas inlet 6, the higher the deposition rate of the SiO ₂ film is.
It is desirable because it rises. Also, the inside of the plasma generation chamber 1 or the plasma generation chamber 1 and the ring-shaped supply gas inlet 6
There is also an effect even if the mesh 14A is installed between them. The position where the mesh 14B is installed is TE nearer the substrate 7.
It is possible to remove ions diffusing out of the mesh 14A provided on the OS gas inlet 6 side, and to improve the deposition rate of the film. If it is too close to the TEOS gas inlet 6, diffused valence electrons cannot be completely removed.

The amount of electrons, negative ions and positive ions in the plasma can be controlled by grounding the meshes 14A and 14B or applying a DC voltage from minus to plus. DC voltage
When the voltage is applied in the range of 50 V to +50, the film forming speed increases. In particular, when the OV, that is, when the meshes 14A and 14B are only grounded and no voltage is applied, the effect of trapping electrons in the plasma is the highest, and the film formation rate is significantly increased (see the examples described later). In order to increase the deposition rate of the SiO ₂ film, it is preferable to ground the meshes 14A and 14B. When a DC voltage is applied to the meshes 14A and 14B, the meshes 14A and 14B must be completely insulated from the reaction chamber. The stainless steel meshes 14A and 14B capture the electrons in the plasma, release them to the ground, and cause radicals (neutrons) in the plasma.
Only pass through. The newly installed stainless mesh 14B ensures that valence electrons that could not be flowed to the ground by only the mesh 14A flow to the ground, thereby improving the deposition rate of the film.

Good quality S without impurities without heating the substrate
In order to coat iO ₂ , precise control of generated plasma conditions is required. In particular, the supply amount of the raw material supply gas is important. For example, when TEOS gas is used as a supply gas, an excess supply of 2 sccm (abbreviation of standard cc / min, cc / min (at 25 ° C. in SI unit system)) within the range of 100 to 200 W of microwaves results. The film speed is significantly reduced (see the description of FIG. 2 in the embodiment described later).
Further, when the TEOS gas becomes 2 sccm, the content of carbon, which is an impurity in the film, increases remarkably, and the film quality deteriorates. Therefore, the supply amount of oxygen gas 10 scc
When the TEOS gas is supplied at 1.5 sccm or less with respect to m, a high quality SiO ₂ film can be coated. Among them, the film formation rate is highest when the TEOS supply amount is 1.5 sccm. Further, the mesh 14A grounded under the plasma conditions is connected to the ring-shaped supply gas inlet 6 through 5
When it is set at a position of 0 mm, the film forming speed is significantly increased, which is effective. Further, even if a mesh is used, the film quality does not deteriorate. Note that the circular mesh 14B is
The effect is greater the closer it is provided. 1, the cooling water is supplied from the cooling water supply port 17 and the cooling water is discharged from the cooling water discharge port 18. Also, 7
a is a heating device for the substrate 7.

[0015]

EXAMPLES Using an ECR plasma CVD apparatus of Embodiment FIG 1, was performed a thin film forming experiments. Plastic PC Specimens A transparent PC material and an impact-resistant PP material, which are frequently used in automobiles, were selected as test specimens. An injection-molded plastic plate (60 × 60 × 3 mm) was used as a test piece. In order to deposit a high quality SiO ₂ film as a source gas , monosilane (SiH
₄ ) is often used, but is highly flammable and very dangerous. Therefore, highly safe TEOS [Si (OC ₂ H ₅ ) ₄ ] was used as the supply gas.

[0016] In this experiment the method for depositing an SiO ₂ film, an ECR plasma CVD apparatus of a lateral arrangement,
A magnetic coil is disposed around the plasma generation chamber, and a magnetic flux density of 875 Gauss, which is an ECR condition, is provided in the plasma generation chamber.
And a microwave was introduced into the generation chamber to generate plasma. The magnetic field distribution of the magnetic coil is of a divergent magnetic field type that decreases in the direction from the plasma generation chamber to the sample chamber. High-purity O ₂ gas as an upstream gas was flow-controlled by a mass flow controller and introduced into a plasma generation chamber to generate ECR plasma. Its downstream high purity liquid TEOS was warmed vaporized 80 ° C., poured its gas inlet 6 of φ150mm shaped ring with flow control, 1.0 .mu.m the SiO ₂ film PC, the PP surface Deposited. Furthermore, a circular (φ160 mm) mesh (φ0.2 mm stainless steel wire, 1.5 × 1.75 mm grid) 14A connected to the ground is T
A film deposition experiment was performed in the case where the film was installed between the EOS inlet 6 and the substrate 7 and between the mesh 14A and the base 7. The position of the mesh 14A was 50 mm downstream from the TEOS inlet. The position of the mesh 14B is TE
50 mm from the board 7 from the position 50 mm from the OS inlet
Was changed to the position. The other dimensions of the apparatus were as shown in FIG.

FIG. 3 shows TEO measured under the above conditions.
The relationship between the position from the S inlet 6 to the mesh 14B and the film deposition rate is shown. As understood from this figure, as the position of the mesh 14B is closer to the substrate 7, the deposition rate of the film is improved.

[0018]

As is apparent from the above description, according to the present invention, ECR plasma CVD (Electron Cycrotron Resonance Plasma Assi
(sted Chemical Vapor Deposition) In the technology, by positively flowing valence electrons to the ground and increasing the deposition rate of the film, a transparent SiO ₂ film is deposited thinly on the plastic surface to increase the surface hardness without impairing the design. Can be improved. According to the present invention, the surface function of the plastic can be remarkably improved, and parts that could not be made plastic can be put to practical use, and the recycling and weight reduction of automobile parts can be further achieved. INDUSTRIAL APPLICABILITY The present invention can be applied to plastic parts of various products such as automobiles and motorcycles. For example, transparent plastic parts for automobiles, lamp housings, meter panel plates, window materials, sunroofs, etc., original instrument panels made of plastic, bumpers, door knobs, handles, trim materials, console boxes, etc., plastic doors, mirrors, emblems, etc. Also, it can be applied to a transparent plastic windshield for motorcycles, a plastic cowling, a handle lever, a fuel tank, a plastic engine cover for an outboard motor, and a rust-proof coating on metal parts.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram illustrating an embodiment of an ECR plasma CVD apparatus used in the present invention.

FIG. 2 is a perspective view illustrating a TEOS gas inlet.

FIG. 3 is a graph showing a relationship between a position from a TEOS inlet to a mesh 14B and a film deposition rate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plasma generation chamber 2 Magnetic coil 3 Microwave introduction port 4 Sample chamber 5 Plasma generation gas introduction port 6 Source gas supply port 7 Polymer base material 8 Source gas supply system 9 Source gas tank 10 Source gas supply line 11 Purge gas Supply line 12 MFC device 13 Supply line 14A and 14B mesh 15 DC power supply 16 Plasma stream 17 Cooling water supply port 18 Cooling water discharge port

Claims (2)

[Claims] In a method of forming a thin film on a polymer substrate by plasma CVD, a magnetic field is applied to the plasma generation chamber by a magnetic coil disposed around the plasma generation chamber, and microwaves are introduced into the plasma generation chamber; An upstream gas is introduced into a plasma generation chamber to generate ECR plasma, a raw material is vaporized downstream to generate a supply gas, and the supply gas is supplied from an inlet. Between the material or the plasma generating chamber and the inlet and between the inlet and the polymer substrate and set at a position closer to the polymer substrate than the mesh. EC above mesh
A method of forming a thin film on a polymer substrate by plasma CVD, wherein the plasma is passed through R plasma to deposit an SiO ₂ film on the surface of the polymer substrate. 2. In an apparatus for forming a thin film on a polymer substrate by plasma CVD, a magnetic field is applied by a magnetic coil disposed around the ECR plasma to introduce a microwave and an upstream gas. A plasma generation chamber for generating a gas, an inlet for supplying a supply gas to the downstream, and installed between the inlet and the polymer substrate or between the plasma generation chamber and the inlet. An apparatus for forming a thin film on a polymer substrate by plasma CVD, comprising: a mesh; and, in addition to the mesh, a mesh provided closer to the polymer substrate than the mesh.