JPH10219454A - Device for forming thin film by plasma cvd - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin film forming device by plasma CVD capable of cleaning a mesh without detaching it and also without using hydrofluoric acid. SOLUTION: In a thin film forming device by plasma CVD contg. a plasma generating chamber 1 for generating ECR plasma, to which the magnetic flux is applied by magnetic coils 2 arranged therearound, capable of introducing a microwave and furthermore capable of introducing an upstream gas, an introducing port 5 for feeding a feeding gas to a downstream and a mesh 14 passing ECR plasma, a heating element 20 for heating and cleaning the mesh 14 is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an apparatus for forming a thin film 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 plastics for automobile parts has been promoted, and fuel economy has been improved by reducing the weight of automobiles. In particular, thermoplastics have attracted attention as materials that are easy to recycle, and have been actively employed in automobile parts. However, plastic materials have lower mechanical strength and surface hardness than metal materials and are inferior in scratch resistance. In addition, the surface is exposed to the sun's ultraviolet rays and heat,
Discoloration and reduction in strength occur, and weather resistance is never good. Considering the functions and quality of automobiles, there are limits to the parts that can be used for plastic. In the future, unless the plastics are subjected to some surface treatment to improve their functions, it is not expected that automobile parts will become plastic.

As a method for treating the surface of plastic as described above, a method of forming a thin film by plasma CVD has been conventionally performed. According to plasma CVD, a substrate temperature of 40
By heating to 0 ℃ 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 plastics 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 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
Thin film formation by plasma CVD on a polymer substrate 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 The device was developed (Japanese Patent Application No. 8-52580). In this apparatus, a magnetic field is applied by a magnetic coil arranged around a thin film forming apparatus by plasma CVD on a polymer base material, and an ECR plasma in which a microwave is introduced and an upstream gas is introduced is applied. A plasma generation chamber for generating, an inlet for supplying a supply gas to the downstream, and the above-mentioned installed between the inlet and the polymer substrate or between the plasma generation chamber and the inlet And a mesh through which ECR plasma is allowed to pass.

However, in the device developed as described above, a SiO ₂ film is deposited on the surface of a mesh (usually stainless steel) for trapping valence electrons in plasma, and if the device is used continuously, The trapping effect of the mesh was weakened, which sometimes affected the film formation rate. For this reason, the mesh has been removed from the apparatus and immersed in a hydrofluoric acid solution to dissolve and remove the SiO ₂ film. It is troublesome to remove the mesh in this way, and this hydrofluoric acid has a strong corrosive property, so that care must be taken in handling. Still another method has been to remove the mesh and heat it. However, even in the case of heating, a very time-consuming operation of once bringing the reaction chamber to atmospheric pressure, taking out the mesh, washing, reattaching and reducing the pressure was required.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a thin film forming apparatus by plasma CVD which can clean a mesh without removing the mesh and without using hydrofluoric acid.

[0008]

In order to achieve the above object, according to the first aspect of the present invention, a magnetic field is applied by a magnetic coil disposed around, and a microwave is introduced and an upstream gas is introduced. A thin film forming apparatus by plasma CVD including a plasma generation chamber for generating an ECR plasma, an inlet for supplying a supply gas downstream, and a mesh for passing the ECR plasma. Wherein a heating element for heating and washing the mesh is provided.

According to a second aspect of the present invention, in the thin film forming apparatus based on the plasma CVD according to the first aspect, the heating element is provided so as to be capable of moving forward and backward with respect to the mesh. According to a third aspect of the present invention, there is provided the thin film forming apparatus by plasma CVD according to the first aspect, wherein an inert gas is caused to flow into the sample chamber after or during the heating of the mesh by heating the film residue removed from the mesh by heating. It is characterized in that it is removed from the sample chamber.

[0010]

FIG. 1 shows an embodiment of an apparatus for forming a thin film by plasma CVD according to the present invention. This apparatus is a horizontal type ECR plasma CVD apparatus, in which a magnetic coil 2 is arranged around a plasma generation chamber 1, a magnetic field which is an ECR condition is applied in the plasma generation chamber 1, and microwaves are introduced into the generation chamber 1. 3 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.
Then, ECR plasma is generated. The raw material liquid is heated and vaporized in the downstream thereof, and the gas is flow-controlled from the ring-shaped inlet 6 by controlling the flow rate thereof, and a polymer base material 7 such as PC (polycarbonate resin) or PP (polypropylene) (made of plastic) is used. The substrate can have a SiO ₂ film deposited thereon. The source gas supply system includes a source gas tank, a source gas supply line, a purge gas supply line, and an MFC device. In this apparatus, a source gas from a gas supply line is temporarily stored in a source gas tank, and the source gas is mixed with a purge gas (eg, N ₂ ) from a purge gas supply line by an MFC device, and a predetermined amount is passed through a supply line 13. From the inlet 6. This inlet 6
A plurality of small holes are formed in the inner peripheral surface of the ring tube, and gas flows out uniformly from the small holes.

As described above, as a raw material of the plastic substrate 7 to which the present invention is applied, polymers such as polycarbonate (PC), polypropylene (PP), polyethylene (PE), and polystyrene (PS) are mentioned. be able to. Further, as a raw material of the supply gas to be deposited, Si-containing compounds such as monosilane, tetramethylsilane, hexamethyldisilane, and tetraethoxysilane can be given. Examples of the gas supplied to the upstream include O ₂ , CO, H ₂ , He, and Ar.

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 installed between The mesh 14 is generally made of metal (preferably made of stainless steel), and is grounded or a DC positive or negative voltage is applied. Mesh 1
No. 4 has a role of catching electrons in the plasma, escaping to the ground, and allowing only radicals (neutrons) in the plasma to pass. 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, when the mesh 14 is made of a stainless steel wire, if the mesh is too thick, the shadow of the wire is transferred to the surface of the formed film and becomes uneven, so that the mesh 14 must be thin to some extent. Therefore, the diameter of the wire should be
mm or less is preferable.

If the lattice size of the mesh 14 is too large, electrons in the plasma cannot be trapped and pass through the mesh 14 together with radicals, so that it must be reduced to some extent. Therefore, it is preferably 5 mm × 5 mm or less. However, the shape of the grating is not limited, and may be, for example, an octagon, and the area size of one grating 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 (plastic, metal, ceramics, and materials are not particularly limited) is a low-temperature and high-speed formation of the SiO ₂ film. Important above. The position where the mesh 14 is installed is not close to the substrate side of the ring-shaped supply gas inlet 6,
It is desirable that the closer to the ring-shaped supply gas inlet 6, the higher the deposition rate of the SiO ₂ film is. It is also effective to install a mesh 14 in the plasma generation chamber 1 or between the plasma generation chamber 1 and the ring-shaped supply gas inlet 6.

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, 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 forming speed is significantly increased. In order to increase the deposition rate of the SiO ₂ film, it is preferable to ground the mesh 14. When applying a DC voltage to the mesh 14,
The mesh 14 must be completely insulated from the reaction chamber.

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 excessive 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. 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, if the TEOS gas is supplied at a rate of 1.5 sccm or less with respect to the supply rate of the oxygen gas of 10 sccm, 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, when the mesh 14 grounded under these plasma conditions is installed at a position 50 mm from the ring-shaped supply gas inlet 6, the film forming speed is significantly increased, which is effective. Further, even if a mesh is used, the film quality does not deteriorate.

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. Still further, the device of FIG. 1 includes a measuring device. In this measuring device, the state of the substrate 7 is captured by a quartz lens and sent to a spectrometer via an optical fiber. From the spectrometer, it can be further analyzed by a microprocessor via a detector and a controller, and the control conditions can be optimized.

According to the present invention, there is provided a plasma CVD apparatus basically comprising the above-mentioned structure, characterized in that the means for cleaning the mesh is improved. As an embodiment of the cleaning means, one using a heating element 20 as shown in FIGS. 1 to 4 is shown. As shown in FIG. 3, the heat generating element 20 is formed by joining the heat generating parts 21 and 21 facing each other by a joint part 22 and supporting the heat generating parts 21 and 21 with a pointing cylinder 23. Heating part 21
Has the same configuration as a so-called electric heater, and as shown in FIG.
Is provided with a nichrome wire 25 for heat generation. A lead wire 26 is provided in the cylindrical support tube 23, and a power supply 27 is provided.
Connected to Further, as shown in FIGS. 1 and 2, the heating element 20 is always stored in a storage space 28 provided above the plasma CVD apparatus so as not to disturb the reaction in the sample chamber, but can move up and down. It has become. As shown in FIG. 5, the contact portion with the support cylinder 23 is sealed by an O-ring 29 at the upper portion of the storage space 28.

When cleaning the mesh 14, the heating element 20 descends as shown by the solid line in FIG. Then, electricity is supplied to the heat generating portion 21 to cause the nichrome wire 25 to generate heat and heat the mesh 14. As a result, the mesh 14 is heated, and the film deposited on the surface can be ionized or peeled off by heat. The coating residue removed from the mesh by heating can be removed from the sample chamber by flowing a gas into the sample chamber after or during heating. At that time, the pressure is preferably 0.05 to 1 Pa, and the used gas is preferably an inert gas such as an argon gas. The gas flow rate is 1.
0-50 sccm is preferred. Such an operation keeps the sample chamber clean. Thus, mesh 1
The film deposited and deposited can be removed without taking out 4 from the reaction chamber. When cleaning is completed, heating element 2
0 rises and returns to the storage space 28.

The voltage applied when generating heat is usually 1
It may be about 00V, the current is 8 to 12 A, and the power is 1200
It is about W. The gap between the mesh 14 and the heating part 21 is 1
About 0 mm is preferable, and the surface temperature of the heat generating part is 600 to
800 ° C. and the washing time are preferably 1 to 10 minutes. By providing the washing means as described above, washing can be performed safely in a short time while the mesh 14 is attached to the apparatus. The cleaning cycle is set every time a thin film of about 1 μm is formed on the substrate. Note that when performing the cleaning operation, other operations necessary for the film formation operation, for example, the supply of the source gas and the like are interrupted.

In the above embodiment, the heat generating means is made of a nichrome wire. However, other heat generating means can be used as long as the object of the present invention is not hindered.

[0021]

As is apparent from the above description, according to the present invention, the plasma CV can be cleaned without removing the mesh and without using hydrofluoric acid.
D provides a thin film forming apparatus.

[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 conceptual diagram showing one embodiment of a mesh cleaning device used in the present invention.

FIG. 3 is a perspective view of an embodiment of a mesh cleaning apparatus used in the present invention, in which an inner surface structure of a heating unit is not shown.

FIG. 4 is a front view showing an inner surface structure of a heating unit of the mesh cleaning device used in the present invention.

FIG. 5 is a partial cross-sectional view illustrating an upper part of a storage space showing an embodiment of a mesh cleaning device used in 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 Introduction port 7 Polymer base material 13 Supply line 14 Mesh 16 Plasma stream 17 Cooling water supply port 18 Cooling water discharge port 20 Heating element 21 Heating part 28 storage space

Claims (3)

[Claims] 1. 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 supply the plasma to a downstream. In a thin film forming apparatus by plasma CVD including an inlet for supplying a gas and a mesh through which the ECR plasma passes, a heating element for heating and cleaning the mesh is provided. An apparatus for forming a thin film by plasma CVD. 2. The plasma C according to claim 1, wherein said heating element is installed so as to be able to advance and retreat with respect to said mesh.
VD thin film forming equipment. 3. The method according to claim 1, wherein the coating residue removed from the mesh by heating is removed from the sample chamber by flowing an inert gas into the sample chamber after or during heating of the mesh. An apparatus for forming a thin film by plasma CVD.