JP2001303253A - Thin film forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin film forming apparatus with which a thin film of a high quality can reliably be obtained at a high speed. SOLUTION: This thin film forming apparatus employing the plasma CVD to form a thin film on a base material includes a plasma generating chamber for generating the ECR plasma to which a magnetic field is applied to a periphery thereof by a magnetic coil and into which an upstream gas is introduced with the introduction of microwaves, an inlet for supplying a downstream gas, and a mesh installed between the inlet and a polymer base material or between the plasma generating chamber and the inlet. The inlet for introducing the downstream gas in disposed so that the supplied downstream gas is uniformly distributed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an apparatus for forming a thin film on a substrate such as a plastic 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, impurities in the thin film can be removed and a good quality thin film can be coated. But,
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). 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 is excellent in adhesion to the base material, but has a problem that it does not have much hardness and is poor in abrasion resistance because it contains a large amount of impurities such as carbon and water (Japanese Patent Application Laid-Open (JP-A) No. 2002-110630). 62-1329
No. 40). Meanwhile, a reaction gas is introduced into the vacuum reaction chamber,
When a magnetic field of 875 Gauss is applied and microwaves are applied, electrons in the plasma are accelerated by the microwave electric field due to the electron cyclotron resonance (ECR) effect, and high-density plasma can be generated. It was developed (JP-A-56-155535).

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 in that the heat applied to the plastic substrate is still large, the damage to 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
Using the Assisted Chemical Vapor Deposition) technique, a transparent SiC film to the plastic surface is a thin deposition, SiO ₂ by Plasma CVD to polymer substrates so as to improve the surface hardness without compromising the design of
Developed thin film forming method and apparatus (Japanese Patent Application No. 8-5258)
No. 0). In this device, a mesh is installed between the plasma generation chamber and the supply gas inlet, and this mesh captures electrons in the plasma, escapes to ground, and allows only radicals (neutrons) in the plasma to pass. The film forming speed is improved. However, even in the above technique, the hardness of the SiO ₂ film to be coated is limited, and it has been demanded to form a thinner film having higher hardness. Further, since the SiO ₂ film transmits ultraviolet light, even if such a thin film is formed on a plastic material, the plastic material may be deteriorated by the ultraviolet light. That is, a SiC film having a band gap of about 4.5 eV to 5 eV is an SC film having a band gap of about 8 eV.
Compared with the iO ₂ film, the band gap is small, and the film has an ultraviolet cut characteristic.

In view of the above, SiC thin film having sufficient hardness and weather resistance to ultraviolet light can be formed on the surface of a plastic substrate at a low temperature by SiC by plasma CVD on a polymer substrate. A method and an apparatus for forming a thin film are disclosed in Japanese Patent Application No. 8-288156 (JP-A-10-81).
971).

However, this thin film forming apparatus still has the following problems. (1) Concentric unevenness occurs in the thickness of the formed thin film due to the shape of the material gas (downstream gas) inlet and the plasma density distribution. (2) Due to continuous operation for a long time, a film component adheres to the mesh, and the film formation speed is reduced, and there is a possibility that original characteristics such as obtaining a high-quality thin film at high speed may not be exhibited. (3) Originally, the closer the mesh is to the substrate, the higher the film formation speed is. However, if the substrate is too close to the mesh, the trace of the mesh is transferred to the formed thin film, resulting in deterioration of quality. Therefore, in order to obtain a high quality thin film, the mesh has to be moved away from the substrate to some extent at the expense of the film forming speed.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thin film forming apparatus capable of reliably obtaining a high quality thin film at a high speed in view of the above circumstances.

[0009]

In order to achieve the above object, in a thin film forming apparatus according to the present invention, a magnetic field is applied by a magnetic coil arranged around the apparatus, and a microwave is introduced and an upstream gas is introduced. A plasma generation chamber for generating ECR plasma, and an inlet for supplying a downstream gas;
In order to introduce the downstream gas in a thin film forming apparatus by plasma CVD on a substrate including a mesh provided between the inlet and the polymer substrate or between the plasma generating chamber and the inlet. Is characterized in that the downstream gas supplied is uniformly dispersed.

In another aspect, the thin film forming apparatus according to the present invention is characterized in that the mesh is formed so as to be dense at the center. Further, the thin film forming apparatus according to the present invention is characterized in that, in another aspect, the mesh is movably installed. Furthermore, the thin film forming apparatus according to the present invention is characterized in that, in another aspect, the mesh is vibrated.

[0011]

FIG. 1 shows an embodiment of a thin film forming apparatus according to the present invention. This apparatus is an embodiment relating to an apparatus for forming a SiC thin film using HMDS, as described later. This device is a horizontal ECR
In the plasma CVD apparatus, a magnetic coil 2 is arranged around the plasma generation chamber 1, a magnetic field that is an ECR condition is applied to the inside of the plasma generation chamber 1, and microwaves are introduced 3 into the generation chamber 1 to generate plasma. 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. Examples of the gas supplied to the upstream include H ₂ , He, and Ar. However, it is optimal since H ₂ is best degrade HMDS.

Further, in the downstream, another gas is flow-controlled from the ring-shaped inlet 6 by controlling the flow rate,
An SiC film can be deposited on the surface of a polymer substrate 7 (plastic substrate) such as PC (polycarbonate resin) or PP (polypropylene). Examples of the raw material of the plastic substrate 7 to which the present invention is applied include polymers such as polyethylene (PE) and polystyrene (PS) in addition to polycarbonate (PC) and polypropylene (PP). In the present invention, Hexamethyldisilane (HMDS) is used as He as a downstream gas (source gas) flowing from the ring-shaped inlet 6.
Use what has been bubbled with gas. Note that other silicon-containing compounds suitable for the present invention can also be used.

In the plasma CVD using HMDS and hydrogen gas, first, a hydrogen radical from upstream plasma breaks the Si—Si bond of HMDS to generate a precursor. In addition, the precursor reacts,
It is believed that the SiC film will be deposited.

The supply system of the source gas supplied from the ring-shaped inlet 6 of the present invention includes a constant temperature chamber 8, MFC (mass flow controller) devices 9 and 10, a bubbling He
It includes a gas tank 11, a container 12 containing a liquid HMDS, and a supply line 13. In this supply system, the H existing in the liquid state in the container 12 maintained at 28 ° C. in the constant temperature chamber 8 is used.
The MDS is supplied with H gas as bubble gas via the MFC device 9.
e gas is introduced. The bubbled HMDS is MF
The gas is supplied from the inlet 6 as a downstream gas through the supply line 13 via the C device 10.

In the present embodiment, the inlet 6 has a small hole 6 formed in a rectangular inner peripheral surface as shown in an enlarged view in FIG.
a are provided in a plurality of holes so that gas flows out uniformly from the small holes. The left and right small holes 6a are
They are vertically offset from each other. Therefore, as shown by the dotted arrows in the drawing, the outflowing gases do not interfere with each other. Further, the outflow direction of the small holes 6a is provided with an angle θ of 5 to 20 ° toward the substrate side, so that interference between gases can be reliably avoided.

Conventionally, the inlet 6 is formed in a circular shape. For this reason, the introduced gas gathered at the center and could not be uniformly dispersed. With the above configuration, the supplied downstream gas is uniformly dispersed. This eliminates the conventional disadvantage that concentric unevenness occurs in the thickness of the formed thin film. Therefore, a high-quality thin film can be obtained at a high speed.

Further, in this apparatus, the circular mesh 14 connected to the ground is connected to the ring-shaped supply gas inlet 6 and the substrate 7.
It is provided between. The mesh 14 is generally made of metal (preferably stainless steel), and is grounded or applies a DC positive or negative voltage. The reference numeral 15 indicates a DC power supply. The mesh 14 has a role of catching electrons in the plasma, escaping to the ground, and passing only radicals (neutrons) in the plasma, and therefore, the diameter of the mesh and the size of the wire thickness grid are important.
The mesh 14 must be larger than the diameter of the ring-shaped feed gas inlet 6 and the diameter of the plasma stream 16 at this point to be generated. For example, mesh 14
If a stainless steel wire is used, if the wire is too thick, the shadow of the wire will be transferred to the surface of the formed film, resulting in unevenness.
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 mesh 14 is too large, the electrons in the plasma cannot be trapped and pass through the mesh 14 together with the radicals. Therefore, it is preferably 5 mm × 5 mm or less. However, the shape of the grid is not limited, and may be, for example, an octagon, and the area size of one grid is 2
It is preferably 5 mm ² or less. ECR Plasma C
Matching of the position of the mesh 14 installed in the VD apparatus and the positional relationship between the ring-shaped supply gas inlet 6 and the substrate 7 (plastics, metals, ceramics, and materials are not particularly limited) can improve the low-temperature and high-speed formation of the SiC film. Is important. The position where the mesh 14 is installed depends on the position of the substrate 7.
It is desirable that the film formation rate of the SiC film be increased closer to the ring-shaped supply gas inlet 6 instead of closer to the side. Further, a mesh 14 is formed in the plasma generation chamber 1 or between the plasma generation chamber 1 and the ring-shaped supply gas inlet 6.
It is effective to install

The amount of electrons, negative ions and positive ions in the plasma can be controlled by grounding the mesh 14 or applying a DC voltage from negative to positive. DC voltage from -50V to +
When the voltage is applied in the range of 50, the film forming speed increases. In particular, when the OV, that is, when the mesh 14 is only grounded and no voltage is applied, the effect of trapping electrons in the plasma is the highest, and the film formation speed becomes extremely high (see Examples described later). In order to increase the deposition rate of the SiC film, it is preferable to ground the mesh 14. When a DC voltage is applied to the mesh 14, the mesh 14 must be completely insulated from the reaction chamber. Stainless mesh 14
Plays a role in capturing electrons in the plasma, escaping to the ground, and passing only radicals (neutrons) in the plasma.

In order to coat high-quality SiC containing no impurities without heating the substrate 7, precise control of generated plasma conditions is required. In particular, the supply amount of the raw material supply gas is important. When HMDS bubbled by He is used as a source gas, 0.8 to 1 sccm [standard
Abbreviation of cc / min, in the SI unit system, is preferably between cc / min (at 25 ° C.). If it exceeds 1 sccm, an extra film will adhere to the reaction chamber, and the reaction chamber will be contaminated, which will impair the coating of a high quality SiC film. In contrast, H ₂ gas is 5 to 50 sccm
Is suitable. The pressure in the sample chamber 4 is set to 0.
The range from 05 to 2 Pa is preferred. Further, if the mesh 14 grounded under the plasma conditions is installed at a position of 0 to 50 mm from the ring-shaped supply gas inlet 6, the film formation speed is significantly increased, which is effective. Further, even if a mesh is used, the film quality does not deteriorate. The power of the microwave is preferably between 100 W and 200 W,
Around 50W is good. As will be understood from the examples described later, when the output exceeds 150 W, the deposition rate decreases.

The substrate temperature may be room temperature. However, for plastics that can be heated, heating at 200 ° C. or higher is preferred. This is because the content of oxygen (O) as an impurity is reduced. Plastics having heat resistance of 200 ° C. or less, that is, substrate materials suitable for use at room temperature to less than 200 ° C. include polyacetal resins, epoxy resins, polybutylene terephthalate, polypropylene, methacrylic resins, polycarbonate resins, polystyrene, and ethylene. Acid bispolymer, ethylene vinyl alcohol, polyphenylene ether, polybutadiene, AB
Examples thereof include S resin, vinyl chloride, polyalate, polyurethane resin, melamine resin, unsaturated polyester resin, urea resin, high density polyethylene, low density polyethylene, and linear low density polyethylene. 20
Plastics having heat resistance of 0 ° C. or higher include polyimide resin, polyethylene terephthalate resin, polyamide phenol resin, fluorine resin, silicone resin, polyphenylene sulfide, polyether ketone resin,
Examples thereof include polyether sulfone resins and aromatic polyesters. Further, in the apparatus shown in FIG. 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. 7a is a heating device for the substrate 7.

When the substrate temperature is lower than 600 ° C., an amorphous film or a transparent amorphous film is formed, and when the substrate temperature is higher than 700 ° C., a polycrystalline film is formed.

The present invention can be implemented by improving the mesh 14 even when the inlet 6 is the same as the conventional one. FIG. 3 shows such an embodiment. In this embodiment, the mesh 31 shown in FIG. 3A is a mesh configured such that the center is dense and the outside is sparse. Also, as shown in FIG. 3 (b), a mesh 32 in which the wire runs only in one direction is prepared, and two meshes are prepared so as to be orthogonal to each other as shown in FIG. 3 (c). You may make it arrange | position. Both the mesh 31 and the mesh 32 are set so that the mesh size as viewed from the flow direction is 25 mm ² or less as in the embodiment of FIG. In the embodiment of FIG. 3, the mesh is configured to be dense at the center. As a result, the plasma density distribution is not homogenized, and concentric unevenness in the thickness of the formed thin film does not occur. Therefore, the effect of being able to obtain a high-quality thin film inherent to the device at a high speed can be satisfied.

It is to be noted that, even if a mesh having a small diameter (2 to 4 cm in diameter) is superposed on the conventional mesh 14, the object of homogenizing the plasma density distribution can be achieved. Further, by configuring the gas inlet 6 shown in FIG. 2 and the mesh so as to be dense at the central portion, the effect can be further enhanced.

FIG. 4 shows an embodiment in which a mesh is movably installed. In this embodiment, the mesh 41 is connected to the pulley 4
It is configured to be mounted on the wire 43 wrapped around 2 and to slide the wire 43 by the rotation of the motor 44. When the wire 43 slides, the mesh 4
1 slides in the guide 45. Thus, the region P to which the plasma is applied changes. In this embodiment, even when a film component adheres to the mesh 41, a new mesh surface appears by moving the mesh 41, and the conductivity is secured. Due to continuous operation for a long time, the film component adheres to the mesh, and the film formation speed decreases,
The conventional disadvantage that the original characteristics such as obtaining a high quality thin film at high speed cannot be exhibited is solved. In addition,
It is preferable that the mesh 41 moves at intervals of about 3 hours.

In the present invention, as another embodiment, the mesh may be constantly vibrated. Such vibration can be added to the mesh of any of the embodiments shown in FIGS. Further, the present invention can be implemented with the conventional mesh shown in FIG. As means for imparting vibration, means known to those skilled in the art, for example, various shakers having a reciprocating or rotary function can be employed. By imparting the vibration to the mesh, the trace of the mesh is not transferred to the substrate, the mesh can be brought closer to the substrate, and the film formation speed increases. Therefore, it is possible to reliably obtain a high-quality thin film at a high speed.

[0027]

As is apparent from the above description, according to the present invention, it is possible to provide a thin film forming apparatus capable of reliably obtaining a high quality thin film at a high speed. Although the present invention has been described with reference to the SiC thin film in FIGS. 1 to 4, the present invention can be applied to other thin films as long as the object of the present invention is met.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram illustrating an embodiment of a thin film forming apparatus according to the present invention.

FIG. 2 is an enlarged perspective view showing a ring-shaped inlet of the embodiment of the thin film forming apparatus according to the present invention.

FIG. 3 is a perspective view showing an embodiment of a mesh used in the thin film forming apparatus according to the present invention.

FIG. 4 is a perspective view showing another embodiment of the mesh used for the thin film forming apparatus according to the present invention.

[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) gas introduction port 7 Polymer base material 8 Constant temperature chamber 9 MFC device 10 MFC device 11 He gas tank 12 HMDS container 13 Supply line 14 Mesh 15 DC power supply 16 Plasma stream 17 Cooling water supply port 18 Cooling water discharge port 31, 32, 41 Mesh 42 Pulley 43 Wire 44 Motor 45 Guide P area

Claims (4)

[Claims] 1. A plasma generation chamber for generating an ECR plasma in which a magnetic field is applied by a magnetic coil arranged around the apparatus to introduce a microwave and an upstream gas, and a downstream gas. In the thin film forming apparatus by plasma CVD on a substrate including an inlet for supplying, and a mesh provided between the inlet and the polymer substrate or between the plasma generation chamber and the inlet, A thin film forming apparatus, wherein an inlet for introducing the downstream gas is configured such that the supplied downstream gas is uniformly dispersed. 2. A plasma generation chamber for generating an ECR plasma in which a magnetic field is applied by a magnetic coil arranged around the apparatus to introduce microwaves and an upstream gas, and a downstream gas is supplied to the plasma generation chamber. In the thin film forming apparatus by plasma CVD on a substrate including an inlet for supplying, and a mesh provided between the inlet and the polymer substrate or between the plasma generation chamber and the inlet, A thin film forming apparatus characterized in that the mesh is configured to be dense at the center. 3. A plasma generating chamber for generating an ECR plasma in which a magnetic field is applied by a magnetic coil disposed around the apparatus to introduce a microwave and an upstream gas, and a downstream gas. In the thin film forming apparatus by plasma CVD on a substrate including an inlet for supplying, and a mesh provided between the inlet and the polymer substrate or between the plasma generation chamber and the inlet, A thin film forming apparatus, wherein the mesh is movably installed. 4. A plasma generation chamber for generating an ECR plasma in which a magnetic field is applied by a magnetic coil disposed around the cell to introduce a microwave and an upstream gas, and a downstream gas, In the thin film forming apparatus by plasma CVD on a substrate including an inlet for supplying, and a mesh provided between the inlet and the polymer substrate or between the plasma generation chamber and the inlet, A thin film forming apparatus characterized in that the mesh is vibrated.