JPH09316647A - Thin film forming device by plasma cvd - Google Patents

Abstract

PROBLEM TO BE SOLVED: To clean a mesh without removing a mesh and using hydrofluoric acid by providing the mesh with a voltage applying means and allowing the mesh to be heated. SOLUTION: A magnetic coil 2 is arranged around a plasma generating chamber 1, and the magnetic field is applied thereto. Microwaves are introduced therein from a microwave introducing port 3, and an upstream gas is introduced therein from a plasma generating gas introducing port 5. A downstream gas is introduced therein from a ring-shaped introducing port 6. A mesh 14 in which ERC plasma is allowed to pass between the introducing port 6 and a base material 7 is arranged. The mesh 14 is allowed to be heated by a d.c. power source as a voltage applying means. In this way, the mesh 14 is cleaned. As the upstream gas, an inert gas is introduced. In this way, the cleaning of the mesh can be executed without its removal.

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 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 adhesiveness to the base material, 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
Assisted Chemical Vapor Deposition) technology is used to thinly deposit a transparent SiO ₂ film on the plastic surface to improve the surface hardness without impairing the design. A 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.

[0006]

However, in the apparatus developed as described above, Si is formed on the surface of a mesh (usually stainless steel) for trapping valence electrons in plasma.
When the O ₂ film was deposited and continued to be used, the mesh trap effect was weakened, which sometimes affected the film formation rate. Therefore, the mesh is removed from the device, immersed in a hydrofluoric acid solution to dissolve the SiO ₂ film,
Had been removed. 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.

[0007] Therefore, an object of the present invention is to provide a thin film forming apparatus by plasma CVD capable of cleaning the mesh without removing the mesh and without using hydrofluoric acid.

[0008]

In order to achieve the above object, in the invention described in claim 1, a magnetic field is applied by a magnetic coil arranged in the periphery to introduce a microwave and an upstream gas. A plasma generation chamber for generating ECR plasma, an inlet for supplying a supply gas downstream, a space between the inlet and a base material, or the plasma generation chamber and the inlet. A thin film forming apparatus by plasma CVD including a mesh disposed between the mesh and allowing the ECR plasma to pass therethrough, and a voltage applying unit for applying a voltage to the mesh to heat the mesh,
It is characterized in that the mesh is washed by generating heat.

According to a second aspect of the present invention, a plasma is generated for generating ECR plasma in which a magnetic field is applied by a magnetic coil arranged in the periphery to introduce a microwave and an upstream gas. A generation chamber, an introduction port for supplying a supply gas downstream, and a space between the introduction port and a base material or between the plasma generation chamber and the introduction port for passing the ECR plasma. Plasma CV including the formed mesh
In the thin film forming apparatus according to D, an inert gas is introduced as the upstream gas to wash the mesh.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a plasma according to the present invention.
An embodiment of a thin film forming method by CVD is shown. this
The equipment is a horizontal type ECR plasma CVD equipment.
A magnetic coil 2 is placed around the Zuma generation chamber 1 to generate plasma.
A magnetic field that is an ECR condition is applied to the inside of the generation chamber 1 to
A wave is introduced into the generation chamber 1 to generate plasma. What
Note that 3a is quartz glass. Magnetic field distribution of magnetic coil 2
Is a divergence that decreases from the plasma generation chamber 1 to the sample chamber 4
It is a magnetic field type. Mass Flowco Upstream Gas
The flow rate is controlled by the controller and introduced into the plasma generation chamber 5
Then, ECR plasma is generated. That down story
The raw material liquid is heated and vaporized in the glass, and the flow rate of the gas is controlled.
From the ring-shaped inlet 6, and PC (polycarbonate
Nate resin) or PP (polypropylene), etc.
SiO on the surface of the child base material 7 (substrate made of plastic) _Twofilm
Can be deposited. Source gas supply system 8
Is the source gas tank 9, the source gas supply line 10, the
It includes a digas supply line 11 and an MFC device 12. this
In the device 12, the source gas from the gas supply line 10 is used as the source gas.
The raw gas is stored in the raw gas tank 9 and the raw gas is purged.
Purge gas (N _TwoEtc.) and MFC
Mixing is done in the device 12 and a predetermined amount is supplied via the supply line 13.
Supply from the inlet 6. This inlet 6 is inside the ring tube
A plurality of small holes 6a are formed on the peripheral surface, and the small holes 6a
Gas is allowed to flow out uniformly (enlargement of Fig. 1
See figure).

As described above, examples of the raw material of the plastic substrate 7 to which the present invention is applied include polymers such as polycarbonate (PC), polypropylene (PP), polyethylene (PE), polystyrene (PS) and the like. 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 upstream include O ₂ , CO, H ₂ , He, Ar and the like.

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. 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, so that the diameter of the mesh and the size of the wire grid are important. The mesh 14 is a ring-shaped supply gas inlet 6
And the plasma stream at this point that produces 16
Must be larger than the diameter of. For example, when the mesh 14 is composed of a wire made of Stellesun, if the mesh 14 is too thick, the shadow of the wire is transferred to the surface of the formed film to form irregularities, so the mesh 14 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, 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
The matching of the position of the mesh 14 installed in the VD device and the positional relationship between the ring-shaped supply gas introduction port 6 and the substrate 7 (plastic, metal, ceramics, materials are not particularly limited) is effective for low temperature and high speed formation of the SiO ₂ film. Important above. It is desirable that the position where the mesh 14 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 also effective to install the mesh 14 in the plasma generation chamber 1 or between the plasma generation chamber 1 and the ring-shaped supply gas introduction port 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. Particularly, 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. Furthermore, the device of FIG. 1 comprises a measuring device 19. In this measuring device 19, the state of the substrate 7 is captured by the quartz lens 20, and sent to the spectrometer 22 via the optical fiber 21. Spectrometer 2
From 2, the analysis can be performed by the microprocessor 25 via the detector 23 and the controller 24 to optimize the control conditions.

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 the cleaning means, there are a method of applying a voltage to the mesh to heat the mesh and a method of applying plasma molecules of an inert gas. These methods can be used individually or in combination. Method using voltage applying device As shown in FIG.
Wear 0 and 31. A voltage is applied between these terminals 30 and 31. As a result, the mesh 14 itself generates heat, and the coating film deposited on the surface can be ionized or separated by heat. In the form shown in FIG. 2, the mesh 14 is configured to be grounded during the formation of the coating film on the base material.
The voltage applied to the mesh 14 is preferably in the range of 100 to 300V, and the current is preferably about 5 to 20A. Either an AC power supply or a DC power supply may be used. The time for applying the voltage is 1 to 5 hours. FIG. 3 shows an embodiment in which a circuit is configured without using the terminals as shown in FIG. In this form, the cleaning power source 3
2 is provided, and the switch 33 is opened at the time of cleaning so that a cleaning current is passed through the mesh 14. At the time of film formation, the cleaning power source 32 is off. When the film-forming power supply 15 is turned on, the cleaning power supply 32 is turned off. Then, the switch 33 is connected to the terminal 34 side. When the mesh 14 is grounded to form a film, the switch 33 is connected to the terminal 35 side.

Method of Applying Inert Gas In this method, an inert gas such as argon gas is introduced through the plasma generating gas inlet 5 of FIG. That is, the inside of the apparatus is depressurized to an inert gas atmosphere. Then, microwaves are introduced into the plasma generation chamber 1 to generate plasma. The generated inactive molecules such as Ar molecules collide with the surface of the mesh 15 and attack the coating film. Since the inside of the device is depressurized, the ions and the peeled film are exhausted and no residue remains. The gas flow rate is 1.0 to 50 sccm, the pressure in the reaction chamber is 0.05 to 1 Pa, and the microwave output is 100 to 1000 W. By providing the cleaning means as described above, cleaning can be safely performed in a short time while the mesh 15 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.

[0019]

As is apparent from the above, according to the present invention, the plasma CVD can be carried out without removing the mesh and without using hydrofluoric acid.
A thin film forming apparatus is provided.

[Brief description of 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 conceptual diagram showing another embodiment of the mesh cleaning apparatus used in the present invention.

[Explanation of symbols]

 1 Plasma Generating Chamber 2 Magnetic Coil 3 Microwave Inlet 4 Sample Chamber 5 Plasma Generating Gas Inlet 6 Inlet 7 Polymeric Base Material 8 Raw Material Gas Supply System 9 Raw Material Gas Tank 10 Raw Material Gas Supply Line 11 Purge Gas Supply Line 12 MFC Device 13 Supply line 14 Mesh 15 DC power supply 16 Plasma stream 17 Cooling water supply port 18 Cooling water discharge port 19 Measuring device 20 Quartz lens 21 Optical fiber 22 Spectrometer 23 Detector 24 Controller 25 Microprocessor 30, 31 Terminals 30, 31 32 For cleaning Power supply 33 Switch 34, 35 terminal

Claims (2)

[Claims] 1. A plasma generating chamber for generating an ECR plasma in which a magnetic field is applied by a magnetic coil arranged around the microwave to introduce a microwave and an upstream gas, and a downstream is supplied. By plasma CVD including an inlet for supplying gas and a mesh arranged between the inlet and the base material or between the plasma generation chamber and the inlet to pass the ECR plasma In the thin film forming apparatus, a voltage applying unit for applying a voltage to the mesh to heat the mesh is provided, and the mesh is heated to generate cleaning. 2. A plasma generation chamber for generating ECR plasma in which a microwave is introduced and an upstream gas is introduced by applying a magnetic field by a magnetic coil arranged around the plasma generation chamber, and is supplied downstream. By plasma CVD including an inlet for supplying gas and a mesh arranged between the inlet and the base material or between the plasma generation chamber and the inlet to pass the ECR plasma A thin film forming apparatus by plasma CVD, wherein an inert gas is introduced as the upstream gas to wash the mesh.