JP2000109979A - Surface treatment method by dc arc discharge plasma - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface treatment method of arc discharge plasma capable of treating only an objective region on a substrate and complying with an enlarged treatment area with a simple means. SOLUTION: In a method in which gas 2 for discharge and for treatment is supplied between two electrodes 1 to impress DC voltage, a surface treatment is conducted using the plasma with arc discharge generated between electrodes, the surface treatment is conducted by a method in which a plasma generating source is moved for a fixed substrate 3 or a method in which the plasma generating source is fixed and a substrate side is moved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid surface treatment technique using plasma, and more particularly to a method for treating a surface by arc discharge plasma by applying a DC voltage between two electrodes.

[0002]

2. Description of the Related Art Conventionally, as a solid surface treatment technique using plasma (high-speed and continuous production technique for large-area amorphous silicon solar cells, etc.), a method using plasma using parallel plate type high frequency glow discharge (plasma CVD method) has been known. ) Has been adopted. As shown schematically in FIG. 9, this method supplies a processing gas and a mixed gas with another gas between a pair of parallel plate type electrodes 12 and 13 which are opposed to each other in a container 11 which can be evacuated. Power supply 1 between the electrodes
By applying a high-frequency voltage at 5 to bring the electrodes into a plasma state, a part of the gas is decomposed, and a decomposition product acts on the substrate 16 attached to the one electrode 13 to deposit a thin film, etch, This is a technique for obtaining effects such as surface modification.
Reference numeral 14 denotes a matching device for matching the impedance of the power supply 15 with the impedance of the parallel plate type electrodes 12 and 13 accompanied by plasma. 13.56 MHz is widely used as the frequency of the high frequency voltage.

The solid-state surface treatment technology using plasma has the following three features. The processing area can be easily increased by increasing the area of the parallel plate type electrode. In the case of DC discharge, the discharge is not maintained when the substrate or the deposit is an insulator, whereas the high frequency does not depend on the conductivity of the substrate or the deposit. The processing quality may be improved by increasing the frequency of the high-frequency voltage or by using a pulse (for example, in the case of an amorphous silicon solar cell, the photoelectric conversion efficiency is improved).

[0004]

However, in the above-described conventional plasma CVD method using high-frequency glow discharge, if the processing area is increased, the length of one side of the electrode becomes the same as the wavelength of the high-frequency wave used. There is a problem in that the electric field distribution in the inside becomes uneven, so that uniform processing becomes impossible, and the same quality as in the case of a small area cannot be ensured. In particular, this problem becomes remarkable when a higher frequency or a pulse capable of improving the quality is used, and there is a limit in increasing the processing area.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem in such a conventional parallel plate type plasma CVD method using a high-frequency glow discharge in which a large area is used. An object of the present invention is to propose a surface treatment method using DC arc discharge plasma which can be applied and can sufficiently cope with an increase in the treatment area by simple means.

[0006]

A DC arc according to the present invention.
The surface treatment method using discharge plasma is directly applied between two electrodes.
Arc generated between the electrodes by applying a
This is a method that uses plasma by electricity, and its gist is two
Supply discharge and processing gas between the electrodes of
The arc discharge generated between the electrodes
Surface treatment using plasma
Moving the plasma source with respect to the substrate
Or by fixing the plasma source and moving the substrate side
Surface treatment by the method of
You. Also, a plurality of the plasma generating sources are arranged in parallel to perform a surface treatment.
Or program control the plasma source or substrate.
Or the relative position between the substrate and the plasma source.
Change the position, or
One of them is selected and energized. What
The discharge and processing gases are SiH₄,
SiCl₄, Si₂Cl₆, CH₄, C₃H₈, TEG
a, TiCl₄, NH₃, N₂, BF₃, O₂, C
F₄, C₂F₆, B₂H₆, Cu (DPM)₂, P
H₃, C₃F₈, C₄F ₈, F₂, NF₃, Ar, H_e
Etc. can be used.

In the electrode structure of the present invention, the hollow cylinder and the center axis thereof are preferably electrodes, and the diameter of the cylinder is preferably 1 cm or less. By applying a DC voltage between the conductive hollow cylinder and its central axis and introducing a processing gas or a mixed gas with another gas into the cylinder, plasma is generated between the electrodes by arc discharge. The processing gas is decomposed, and the decomposition product blows out from the opening end of the cylinder, and acts on the substrate facing the opening end, such as thin film deposition, etching, and surface modification. In the parallel plate type DC discharge, the discharge is not maintained if the substrate is insulative, but in the present invention, the electrodes are independent of the substrate to be processed, and there is no dependence on the conductivity of the substrate.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic view showing a basic structure of a surface treatment method using a DC arc discharge plasma according to the present invention, and FIG. 2 illustrates an electrode structure in the present invention. And (b) is a schematic diagram showing an electrode in which a cathode and a cylindrical anode are combined, and (c) is a diagram in which a plurality of electrodes having the structure shown in (b) are arranged. (D) is a schematic diagram showing an electrode composed of a cathode and a multi-stage cylindrical anode, and (e) is an electrode formed by arranging an electrode having an anode and a cathode facing each other in multiple stages. FIG. 3 is a schematic diagram illustrating an example of a surface treatment method for a flexible polymer substrate, FIG. 4 is a schematic diagram illustrating an example of a method of performing a wide surface treatment on a sheet-like substrate, and FIG. The three-layer thin film is connected by arranging the electrodes of the FIG. 6 is a schematic diagram showing an example of a method for performing surface treatment on an arbitrary region on a substrate, and FIGS. 7A and 7B are microcrystalline thin films on a substrate, respectively. Schematic diagram illustrating a method of creating a,
FIG. 8 is a schematic view showing an example of a method of forming a solar cell on a flexible polymer substrate, wherein 1 is an electrode, 1-1 is an anode, 1-2 is a cathode, 2 is a gas for discharging and processing,
The substrate, 4 regions, W is the opening diameter of the nozzle, L ₁ is the nozzle tip and the distance between the substrate, L ₂ is distance between the tip and the anode tip end of the cathode, the flexible polymer substrate 3-1, 3-2 It is a sheet-like substrate.

In FIG. 1, when a discharge gas and a processing gas 2 are supplied to a gap between the anode 1-1 and the cathode 1-2, a region 4 of the substrate 3 is subjected to a process determined by the properties of the processing gas. In this case, the diameter of the region 4 is the opening diameter W of the nozzle.
When determined by the distance L ₁ between the nozzle tip and the substrate. The distance L ₂ between the tip and the anode tip end of the cathode, is changed in controlling the effect of heating due to plasma irradiation of the region 4. Heating effect by increasing the distance L ₂ is suppressed,
If it is reduced, the heating effect is promoted. That is, when a microplasma source using direct current as an electrode voltage is used, a target region on a substrate can be processed.

Next, FIG. 2A shows an example in which electrodes are arranged horizontally.
In this configuration, the anode 1-1 and the cathode 1-2 are arranged to face each other.
A high voltage is applied to the pole 1, and one end face of the
Ar gas flows through the gap between the cathode and the cathode 1-2, and the plasma state
And the reactive species in the plasma are transferred to the other end face.
By irradiating the substrate 3 from the nozzle of
The surface modification of only the plasma irradiation part can be performed.
(B) is an example in which the electrodes are arranged vertically, the cathode 1-2 and a hollow cylinder.
A high voltage is applied to the anode 1-1 ′ of the shape, and the cathode 1-2 is hollow.
In the gap with the cylindrical anode 1-1 ', for example, CF₄, C₃
F₈, C₂F₆, C ₄F₈, F₂, NF₃Etc.
Bring the reactive species to the exit of the hollow cylinder
For example, by irradiating on the Si substrate 3, the Si substrate
3. Only the plasma-irradiated part on 3 can be etched
You. Also, as shown in (c), a plurality of electrodes 1 are connected in a row.
Yeah, O₂By using as a discharge gas
A linear process can be performed on the substrate 3. further,
As shown in (d), a cathode 1-2 and a multi-stage hollow cylindrical anode 1-
1 ', or (e)
As described above, the anode 1-1 and the cathode (1-2) are arranged facing each other.
If the poles 1 are arranged in multiple stages, the vias of each stage
By controlling the source voltage, the
Plasma is generated on the surface of the substrate 3 to be processed by controlling the shape of the zuma.
The degree of direct exposure can be controlled.

FIG. 3 shows that the flexible polymer substrate 3-1 conveyed by the roll R is irradiated with Ar plasma by using the electrode 1 having the structure shown in FIG. The surface of the polymer substrate 3-1 can be continuously modified over a predetermined width.

FIG. 4 illustrates a method of continuously performing a surface treatment such as thin film deposition on a sheet-like substrate 3-2. In this case, the electrodes 1 are arranged in a line above the substrate 3-2. By moving the substrate 3-2 in a direction perpendicular to the electrode array, surface treatment such as thin film deposition can be continuously performed on the substrate 3-2 without interruption. In this case, electrode 1
Can have higher electron density than conventional parallel plate type plasma sources, so that a high processing speed can be obtained. Further, in a conventional plasma source using a high frequency, if the length of one row of electrodes is increased, the non-uniformity occurs in the row due to the influence of the wavelength. However, the present invention using a DC discharge has no such effect.

FIG. 5 shows a flexible sheet transported by a roll R.
An example of a method of forming a multilayer film above the polymer substrate 3-1
In this case, the electric wires arranged in a line as shown in FIG.
For example, three rows of poles 1 are installed at desired intervals in the transport direction.
And an SiH ₄/ PH₃Mixed gas, S
iH₄, SiH₄/ B₂H₆Plasma using mixed gas
To generate three layers of p-type, i-type and n-type S
i It is possible to form a film continuously without breaking the thin film structure
it can.

FIG. 6 shows an example of a method for processing an arbitrary-shaped region using a single electrode. The electrode 1 and the substrate 3 are moved in a width direction, a length direction and a height direction by a horizontal movement mechanism and a vertical movement mechanism, respectively. It is possible. Therefore, in the case of this method, an arbitrary area on the substrate 3 can be subjected to surface treatment by the horizontal movement mechanism of the electrode 1 and the substrate 3. The degree of surface treatment, that is, the deposition rate or film thickness for a thin film, and the etching rate or etching depth for etching can be controlled by the vertical movement mechanism of the electrode 1 and the substrate 3. The electrodes and substrate in this method are moved under program control.

FIGS. 7A and 7B respectively show FIGS.
Using the electrode shown in FIG. ₂Reactive to
Gas SiH₄Or SiF₄Introduced in the plasma
The reactive gas is decomposed by the formed atomic H, and a large amount of
Microcrystals S at low temperatures below 300 ° C due to the contribution of H radicals
i. A method of depositing a thin film on a sheet-like substrate 3-2.
You. According to this method, a substrate temperature of 400 ° C. or more is used.
Volume of the polycrystalline silicon thin film
Wear. In addition, Flexi has super heat resistance of 400 ° C or more.
To use a continuous film formation method with a flexible polymer substrate
Polycrystalline silicon thin film on more flexible polymer substrate
Can be continuously formed in a large area.

As shown in FIG. 8, the p-type using polycrystalline silicon is formed on the flexible polymer substrate 3-1.
Forming a polycrystalline silicon solar cell on a flexible polymer substrate 3-1 with high efficiency by adding a transparent electrode forming process, a metal electrode forming process, and a laminating process to the continuous deposition of layers, i-layers, and n-layers. Can be.

In addition, the following processing can be performed. (1) TiCl ₄ and N ₂ or NH as a gas in a plasma source
₃ , a TiN coating is applied to an object having an arbitrary shape by controlling the X, Y, and X axes of the plasma source itself and the object to be irradiated by computer control. (2) A large number of diamond coatings are continuously processed by using H ₂ -diluted CH ₄ as a gas for a large number of cutting tools arranged in a tray. (3) A copper thin film in which electrodes are arranged in two rows, a plasma source of Ar or He is provided in the front row to improve the adhesion of the substrate surface, and a Cu-containing gas raw material such as Cu (DPM) ₂ is used as a raw material in the rear row. By providing forming plasma, a printed circuit board having high adhesion is formed in a large area, at high speed, and continuously. (4) Electrodes and hollow cylinders are alternately bundled in a cylindrical shape, TEGa is passed through the hollow cylinder, and N ₂ is passed through the discharge cylinder, so that N atoms generated in the high-density N ₂ plasma are TE
Reacts with Ga to form GaN on the substrate. Further, since atmospheric pressure discharge is possible, it is expected that the growth speed is high and bulk growth is also possible. (5) In (4), all are discharge cylinders, and cylinders using Si-containing gas such as SiCl ₄ or Si ₂ Cl ₆ as discharge gas and C-containing gas such as CH ₄ or C ₃ H ₈ are alternately circled. By bundling in a columnar shape, SiC is grown on the substrate.

[0018]

As described above, according to the present invention,
By using plasma by arc discharge generated between the electrodes by applying a DC voltage between the two electrodes, a higher processing speed can be obtained compared to the conventional parallel-plate DC discharge system due to the improvement in electron density, In the case of thin-film deposition, the deposition speed of the film-forming element is relatively increased with respect to the speed at which the impurities in the film-forming vessel enter the film. Density is reduced and quality is improved. Further, by continuously arranging a large number of cylindrical electrodes, it is possible to easily perform a process for increasing the area, and to secure a high-quality large-area film. Also in this case, when a high frequency is used, an effect similar to that of a parallel plate appears when the length of the cylindrical array approaches the wavelength, whereas the effect can be avoided by using a direct current. Further, in the method of the present invention, the relative position between the substrate and the nozzle is changed at the same time when the area is increased,
By controlling N and OFF, a thin film can be deposited on an arbitrary region.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a basic configuration of a surface treatment method using DC arc discharge plasma according to the present invention.

FIG. 2 illustrates an electrode structure in the method of the present invention.
(A) is a schematic diagram showing an electrode in which an anode and a cathode are arranged to face each other, (b) is a schematic diagram showing an electrode in which a cathode and a cylindrical anode are combined, and (c) is an electrode having a structure shown in (b). , A schematic diagram showing an electrode composed of a cathode and a multi-stage cylindrical anode, and (e) a multi-stage arrangement of electrodes in which the anode and the cathode are opposed to each other. It is the schematic which shows the electrode comprised by this.

FIG. 3 is a schematic view illustrating an example of a surface treatment method for a flexible polymer substrate.

FIG. 4 is a schematic view showing an example of a method for performing a wide surface treatment on a sheet-like substrate.

FIG. 5 is a schematic view showing an example of a method for continuously forming three layers of thin films by arranging electrodes having a plurality of arrangements shown in FIG. 2 (c) at intervals.

FIG. 6 is a schematic view showing an example of a method for performing a surface treatment on an arbitrary region on a substrate.

FIGS. 7A and 7B illustrate a method of forming a microcrystalline thin film on a substrate, wherein FIG. 7A is a schematic diagram when the electrode shown in FIG. 2A is used, and FIG. It is the schematic in the case of using the electrode shown.

FIG. 8 is a schematic view showing an example of a method for forming a solar cell on a flexible polymer substrate.

FIG. 9 is a schematic diagram showing a conventional method (plasma CVD method) using plasma using a parallel plate type high frequency glow discharge.

[Explanation of symbols]

 Reference Signs List 1 electrode 1-1 anode 1-2 cathode 2 gas for discharge and processing 3 substrate 4 area W nozzle opening diameter L1 distance between nozzle tip and substrate L2 distance between cathode tip and anode tip 3-1 flexible polymer substrate 3-2 Sheet-like substrate

Claims (5)

[Claims] 1. A method for performing a surface treatment using plasma by arc discharge generated between two electrodes by supplying a discharge gas and a processing gas between two electrodes and applying a DC voltage, wherein the plasma is fixed. A surface treatment method using DC arc discharge plasma, wherein the surface treatment is performed by a method of moving the plasma generation source relative to a substrate or a method of moving the substrate side while fixing the plasma generation source. 2. The surface treatment method using DC arc discharge plasma according to claim 1, wherein the surface treatment is performed by arranging a plurality of the plasma generation sources in parallel. 3. The method according to claim 1, wherein the plasma generation source or the substrate is moved under program control. 4. An arbitrary area is surface-treated by changing a relative position between the substrate and a plasma generation source, or by selecting one of a plurality of plasma generation sources and energizing the same. The surface treatment method using a DC arc discharge plasma according to any one of claims 1 to 3. 5. The method according to claim 1, wherein the discharge gas and the processing gas are S
iH₄, SiCl₄, SI₂Cl₆, CH₄, C
₃H₈, TEGa, TiCl₄, NH₃, N₂, B
F₃, O₂, CF₄, C₂F₆, Cu (DPM)₂, P
H₃, C₃F₈, C₄F ₈, F₂, NF₃, Ar, H_e
5. A method according to claim 1, wherein a gas such as the above is used.
Table by the DC arc discharge plasma according to any one of the above.
Surface treatment method.