JPH0796704B2 - Method for homogenizing low-temperature plasma - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for homogenizing low-temperature plasma generated by high-frequency discharge in low-temperature plasma processing used for surface treatment of organic materials, inorganic materials, and the like. .

2. Description of the Related Art In recent years, plasma by high-frequency discharge under low pressure has been used for surface treatment of semiconductors, metals, organic materials, inorganic materials and the like, thin film formation and the like. As one of the plasma treatment effects, for example, by treating a cloth or the like in a low-temperature plasma atmosphere,
It is known that a desizing, scouring or finishing effect can be obtained. An internal electrode type low temperature plasma processing apparatus for these treatments is disclosed in, for example, Journal of the Textile Machinery Society: Volume 38, NO.4.198.
Pp. 199 (1985), Japanese Patent Publication No. 60-31937, Japanese Patent Publication No. 60-1114
No. 9 and Japanese Patent Publication No. 60-11150. Its basic structure is as shown in FIG. That is, in FIG. 4, a high voltage applying electrode plate (2) and a ground electrode plate (3) facing the high voltage applying electrode plate (2) at a constant interval in parallel to the high voltage applying electrode plate (2) are arranged in a processing chamber (1) capable of holding a vacuum. The high voltage applying electrode plate (2) is provided with a feeding point (2a) substantially at the center thereof, and the ground electrode plate (3) is provided with a grounding point (3a) at the substantially center thereof. During the period 3), a high frequency high voltage is applied from the high frequency power supply device (4). The sheet-like material (b) to be treated is fed by the supply roller (7a) from the vacuum-sealed inlet (5a), processed between the electrodes (2) and (3), and taken up from the outlet (5b) to the take-up roller ( Wind up according to 7b). It should be noted that a predetermined processing gas such as air and oxygen is continuously fed into the processing chamber (1) through a supply port (8a) in a predetermined amount and continuously exhausted through an exhaust port (8b) at a predetermined pressure. Keep In these devices, since the plasma generating electrode composed of the high voltage applying electrode plate (2) and the ground electrode plate (3) is installed in the vacuum processing chamber (1), it penetrates through the wall and is vacuumed from the atmosphere. An electric circuit (hereinafter referred to as a power feeding unit) (9) for supplying high frequency power to the inside is required.

As described above, in the conventional apparatus illustrated in FIG. 4, the main body of the normal processing chamber (1) and the metals in the processing chamber (1) are grounded, so that the power feeding section (9) to which the high frequency voltage is applied. Plasma is generated between the high voltage application electrode plate (2) and the surrounding processing chamber (1) body and the metals inside the processing chamber (1), which causes significant power loss and also causes the processing chamber (1) Thermal distortion over a wide range in the processing chamber (1) due to overheating of the main body and the insulating material in the vicinity thereof, or overheating of the power feeding section (9) and the electrode plates (2) and (3) themselves. Although there was a problem such as heat deterioration due to heat and the like, an internal electrode type low temperature plasma processing device connected to one end of the plasma generating electrode by using a cable with external shield such as a coaxial cable or a balanced type cable as a power supply line. Tried and fed The reflection at the connection point between the electrode and the electrode will be small, the standing wave generated on the power supply line will be small, the local overheating of the power supply line will be eliminated, and the plasma will be localized in the generating electrode and generate unnecessary plasma. There is no such effect.

Problems to be Solved by the Invention In such a low-temperature plasma processing apparatus, there is a problem in that the plasma generated between the plasma generating electrodes differs in intensity between the power supply side and the opposite side, and the processing effect becomes nonuniform. . Particularly in the case of processing fabrics and films, a large area or a large volume of plasma is required, and the device becomes large on an industrial scale, but generating a uniform and large-scale plasma by high-frequency discharge increases the frequency. However, it becomes difficult as the wavelength becomes shorter or the device becomes larger.

Considering the movement of the high frequency on the surface of the plasma generating electrode in which the externally shielded power supply line is connected to one end edge as described above, the edge part of the electrode to which the power supply line is connected (hereinafter referred to as the power supply end part). High-frequency wave (traveling wave) starts from.
Since the electric path is open at the edge portion on the opposite side (hereinafter referred to as the terminal portion), the high frequency waves that have arrived are reflected and travel in the opposite direction. The reflected wave and the traveling wave are combined on the electrode surface to generate a standing wave. Since the terminal end of the electrode is electrically open, no current can flow, and the energy of the magnetic field possessed by the current changes to the energy of the electric field.
The value is doubled, and the voltage drops toward the feeding end. Therefore, the maximum plasma generated at the electrode terminal end becomes weaker toward the power supply end, and a gradient occurs in the plasma intensity. The occurrence of this gradient is an unavoidable phenomenon when the terminal end of the electrode is opened.

The present invention is to solve the above problems,
It is an object of the present invention to provide a low-temperature plasma homogenizing method capable of generating a uniform low-temperature plasma even in a low-temperature plasma generator using a large-scale plasma generating electrode.

In the present invention, the large-scale plasma generating electrode means
The width and length of the electrode is approximately 1/50 of the high frequency wavelength (λ)
The above is said. Further, “uniform” means that the non-uniformity is so small that it is practically acceptable.

Means for Solving the Problems In order to solve the above-mentioned problems, a method for homogenizing low temperature plasma according to the present invention is a high frequency discharge type internal electrode in which an externally shielded feed line is connected to one edge of a plasma generating electrode. In the low-temperature plasma processing apparatus, the edge portion on the opposite side of the connection point with the power supply line of the plasma generating electrode, the length of the external shielded one end side is 1/4 or less of the wavelength on the cable The other end is connected.

Operation In the low-pressure high-frequency discharge having the above-described structure of the present invention, one end of a coaxial cable or a balanced cable whose outside is shielded is short-circuited (hereinafter referred to as a short-circuit cable), and the other end is a terminal portion of the plasma generating electrode. Once connected, the distribution of current and voltage on the plasma generating electrode can be optimized. That is, the voltage at the cable short-circuit end is zero, and the voltage increases toward the terminal end of the electrode and the power supply end. The voltage standing wave on the electrode surface is a combination of the standing wave when the terminal end of the electrode is open and the standing wave due to the short-circuit cable. If it is located at or near the center, the gradient of plasma generation will be eliminated. To this end, by adjusting the length of the short-circuit cable connected to the terminal end of the electrode within the range of 1/4 of the wavelength on the cable, the position of the antinode of the standing wave on the electrode surface can be controlled so that plasma is It may be set at a uniform point (approximately the center of the electrode).

Example An example of the present invention will be described. FIG. 1 shows an example of a low temperature plasma processing apparatus for processing a sheet-like material using a plasma generating electrode according to the present invention. Figure 1 (A), (B)
In a processing chamber (11) capable of holding a vacuum, both sides of a high voltage applying electrode plate (12) standing upright are separated from the high voltage applying electrode (12) at regular intervals. A plasma generating electrode (14) in which ground electrode plates (13a) and (13b) having a large area are arranged in parallel and opposite to each other is provided, and high frequency power sent from the high frequency power supply device (15) is matched by a matching box (16).
Is supplied to the plasma generating electrode (14) through a power supply line (17) composed of a coaxial cable (or a balanced type cable) the outside of which is grounded and shielded. The feeder line (17)
As shown in FIG. 2, the plasma generating electrode (14) is connected to one end edge (feed end) (14a). That is, the feeder line (17) consisting of a coaxial cable with the outside shielded.
Outer conductor, ie shield side conductor (17a), (17b)
Are connected to the corresponding ground electrode plates (13a) and (13b), respectively, and the internal conductor (17c) is connected to the high voltage applying electrode plate (12) by the shortest path. Further, connect the coaxial cable (18) to one end at the edge (termination) (14b) opposite to the feeding end (14a) where the connection point of the plasma generating electrode (14) with the feeding line (17) is provided. The side (18a) is short-circuited and the other end side (18b) is connected. The connection mode is the power supply line (1
This is exactly the same as in 7). Next, in the processing room (11),
Vacuum-sealed inlet (20) for the sheet (19) to be treated
It is fed from a) by a supply roller (21a), and guide rollers (22a), (22b), (22c), (22d), (22e), (22).
f), (22g), and between both electrodes (12), (13a) and (1
2) and (13b) are passed through, and the outlet (20b), which is also vacuum-sealed, is pulled out by the winding roller (21b) and wound up. Further, the processing chamber (11) is evacuated from the exhaust port (23a) and continuously supplies a processing gas such as air, oxygen and nitrogen from the intake port (23b) while maintaining a predetermined pressure.

Using the above-mentioned low-temperature plasma treatment device, the polyester textured yarn fabric was subjected to low-temperature plasma treatment under the following conditions.

(Conditions) Treated fabric: Polyester processed yarn fabric (War 15
0 ^D , 110 lines / inch; Weft 150 ^D × 2,55 lines / inch) Processing gas …… Oxygen Processing gas flow rate ・ ・ ・ 4 / min Vacuum degree ・ ・ ・ 0.5 Torr Processing speed ・ ・ ・ 100cm / min High frequency power supply frequency ・ ・ ・ 13.56MHz High frequency Power supply device Free space wavelength: 22 m High frequency power supply output: 2 KW Electrode dimensions (ground electrode): Length 900 mm, width 2000 mm Electrode spacing: 60 mm Short-circuited coaxial cable length: 1000 mm As a comparative example, the device of Fig. 1 was short-circuited. The same fabric as the above example was treated under the same plasma treatment conditions using the coaxial cable (18) without being connected.

The water absorption of the treated fabrics obtained in the above examples and comparative examples is JIS L
It was measured in the width direction of the fabric by -1096 (Bayrec method). The results are shown in FIG. 3, and in the case of the example using the apparatus of FIG. 1, uniform and excellent water absorption performance was imparted in the width direction of the fabric. On the other hand, in the case of the comparative example in which the short-circuited coaxial cable is not connected, the water absorption performance of the fabric is uneven in the width direction, and the end (ear) corresponding to the power supply end to which the power supply line of the plasma generation electrode is connected is the most It was low and increased toward the opposite end, which was not preferable.
As is clear from these results, in the example, the plasma generation state was extremely uniform and highly efficient, and uniform plasma treatment could be performed.

In the present invention, as described above, in the low temperature plasma processing apparatus, by connecting the short-circuit cable to the terminal end on the side opposite to the connection point with the power supply line with respect to the plasma generation electrode, the plasma generated at the plasma generation electrode is made uniform. Will be
The degree thereof varies depending on the position of the antinode of the combined standing wave on the electrode surface as described above, and the homogenization is further improved by positioning the electrode as close to the center as possible. This can be achieved by adjusting the length of the short-circuit cable to be connected under other conditions being the same, within a range of 1/4 of the wavelength on the cable. Although one short-circuit cable is connected in the embodiment shown in FIG. 1, a plurality of short-circuit cables may be connected if necessary.

Instead of the one-sided short-circuited cable of the present invention, it is possible to use a cable that is open on one side and has a length of 1/4 to 1/2 of the wavelength on the cable or a lumped constant inductance.

EFFECTS OF THE INVENTION According to the present invention, in the internal electrode high frequency discharge type low temperature plasma processing apparatus in which the externally shielded power supply line is connected to the one end edge of the plasma generation electrode, the side opposite to the connection point of the power generation line of the plasma generation electrode. In addition, by connecting a cable with a shielded length such as a coaxial cable or a balanced type cable with one end short-circuited within 1/4 of the wavelength on the cable to the other end side, it is possible to achieve a very uniform distribution on the plasma generating electrode. Plasma can be obtained with high efficiency, and extremely uniform treatment can be performed.

[Brief description of drawings]

FIG. 1 shows a low temperature plasma processing apparatus used in an embodiment of the present invention, (A) is a schematic side view, and (B) is II of (A).
2 is a plan view of the main part of the plasma generating electrode of FIG. 1, FIG. 3 is a diagram showing the water absorption performance value of the low temperature plasma treated fabric, and FIG. ) Is a schematic side view, (B) is a schematic front view, and (C) is a schematic plan view. (11) …… Processing chamber, (12) …… High voltage application electrode plate, (13
a), (13b) …… ground electrode plate, (14) …… plasma generating electrode, (15) …… high frequency power supply, (17) …… feeding line,
(18) …… Short-circuit cable.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasutomo Oguchi, 3-16, Kitashinke, Himeji-shi, Hyogo (72) Inventor Shiro Tsutsumi, 24-24 Kaminita, Toyonaka, Osaka G-208 (72) Inventor Masakatsu Takahashi 23 Uji-kozakura, Uji-shi, Kyoto Unit Central Research Institute, Unitika Ltd. (72) Inventor Hiroshi Ishitohaku 2-18 Wakaura East, Wakayama City, Wakayama Prefecture

Claims (1)

[Claims] 1. An internal electrode high frequency discharge type low temperature plasma processing apparatus in which an externally shielded power supply line is connected to one edge of a plasma generation electrode, the end of the plasma generation electrode opposite to the connection point with the power supply line. A method for homogenizing low-temperature plasma, characterized in that the other end of a cable having an externally shielded length with one end short-circuited and having a length of 1/4 or less of the wavelength on the cable is connected to the edge portion.