JP3353585B2 - Plasma processing method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma treatment method such as a modification treatment and a cleaning treatment using plasma on the surface of an article made of an organic material such as a resin or rubber, a metal material, a ceramic material or the like, and to implement the method. To a plasma processing apparatus for performing

[0002]

2. Description of the Related Art Conventionally, in order to improve the abrasion resistance, lubricity, heat resistance and other characteristics of an article, a predetermined substance is injected into the article surface to modify the article, or to improve the article surface roughness. ,
BACKGROUND ART Surface modification treatment for changing the properties of the article surface portion, surface cleaning treatment for removing dirt attached to the article surface, and the like are performed. Examples of such surface treatment include plasma treatment performed under reduced pressure, ion beam irradiation, and the like.

[0003]

However, when the article surface treatment is performed under reduced pressure as described above, an exhaust device having a large exhaust capability is required to bring the inside of the processing container into a predetermined vacuum state. Running costs are high. In particular, in order to process large-sized articles, it is necessary to evacuate the inside of a large-capacity processing container, which further increases the cost.

Accordingly, an object of the present invention is to provide a plasma processing method and apparatus which do not require an expensive exhaust device and which can perform a surface treatment on a large article to be processed at a low cost. And

[0005]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have conducted various studies and have obtained the following findings. That is, when power is applied to a processing gas at or above atmospheric pressure to convert the gas into plasma, plasma can be generated by applying high-voltage power, rather than generating plasma under reduced pressure. High-density plasma can be obtained efficiently. Furthermore, if high-voltage power is applied in a pulse shape, the generated plasma can be easily generated. Thus, an exhaust device that causes a rise in processing cost can be omitted.

[0006] Based on the above findings, the present invention places an article to be processed in a processing vessel and places a pressure of 1 kg / cm ^2-
While introducing a process gas of 10 kg / cm ^2, while adjusting the vessel inside pressure at a predetermined pressure of ^{1kg / cm 2 ~10kg / cm 2} , which was plasma by applying a high voltage power to the gas, wherein under said plasma providing facilities to flop plasma processing method a predetermined process on an article to be treated.

[0007] The present invention is based on the finding, and processing container, and the object to be processed article support means provided within the vessel, the pressure 1kg / cm ² ~10kg / cm ² of the processing gas into said vessel Supply means, and the pressure in the container is 1 kg / c.
a means for adjusting the pressure to a predetermined pressure of m ^{2 to} 10 kg / cm ² , and a means for applying high voltage power to the processing gas introduced into the container by the processing gas supply means to convert the gas into plasma. providing a high-voltage power applying means Help plasma processing apparatus having a.

[0008] According to the method and apparatus of the present invention, by applying a high voltage power, the atmospheric pressure or nearly atmospheric pressure (about 1 kg / cm
² ) The above processing gases can be turned into plasma. Accordingly, an exhaust device for evacuating the inside of a container for performing a process required for surface treatment under reduced pressure such as a conventional reduced-pressure plasma process becomes unnecessary, and running costs associated with the operation of the exhaust device are reduced. It becomes unnecessary, and the processing can be performed at a low cost. In particular, the processing of a large article to be processed that requires a large processing container can be performed at a low cost.

In the plasma treatment in the method and apparatus of the present invention, the surface of the article to be treated is modified by injecting a predetermined substance, the surface roughness of the article is improved, or the property of the surface portion of the article is changed. And surface cleaning treatment by plasma for removing dirt attached to the surface of the article. Before in the method of the present invention
The application of the high voltage power to the processing gas is performed in the processing container.
The discharge main electrode pair and the discharge start between the main electrode pair
A high voltage is applied to the auxiliary ionizing pins including the discharge electrode pairs to assist
A main electrode pair and a pre-ionization pin connected in parallel to a power source;
Is performed by applying a high voltage from the power supply to each of them .
The high voltage power applying means in the present invention apparatus, high voltage
A power supply, and the processing container connected in parallel to the high-voltage power supply;
Main electrode pairs for discharge and pre-ionization pins
The preliminary ionization pin initiates discharge between the main electrode pair.
A pair of discharge electrodes for assistance, and a main electrode
A high voltage is applied to each of the pair and the preionization pin .

Further, the pressure in the container is set to 1 kg / cm ²
Means for adjusting to a predetermined pressure of 〜１０10 kg / cm ² are:
For example, a pressure gauge for detecting the pressure in the container, a pressure regulating valve for releasing gas in the container as needed for the purpose of maintaining the pressure in the container at a predetermined pressure, and the like are considered. In the method and apparatus of the present invention, the high voltage power is 1 kV to
It is conceivable to use DC power of about 50 kV, preferably about 10 kV to 30 kV. This is because if the voltage is lower than 1 kV, the plasma density of the processing gas within the pressure range becomes low, so that the processing speed becomes low and the processing time becomes long. If it is higher than 50 kV, the power supply cost becomes high. Because.

Further, in the method and the apparatus according to the present invention, the high voltage power may be a pulsed high voltage power. At this time, atmospheric pressure or approximately atmospheric pressure (about 1 kg / cm ² ) is used.
The above processing gas can be easily converted into plasma. For example, when a DC power supply is used as a power supply, the application repetition frequency of pulsed high-voltage power is 10 Hz to 1000 Hz.
Hz. This is because if the frequency is lower than 10 Hz, the time during which the article to be processed is exposed to the plasma becomes shorter, and if the frequency is higher than 1000 Hz, the power supply cost increases.

In the method and apparatus of the present invention, when applying a DC high voltage power to the processing gas in a pulse form,
Turning on / off the application of power from the high-voltage power supply using a normal switch may damage the switch terminal.For example, charging the power from the high-voltage power supply once to the capacitor and then discharging the power repeatedly to the gas. A circuit that makes the power application pulsed can be employed. It is conceivable that the charge and discharge are repeated by, for example, a thyratron connected to a high-voltage DC power supply in parallel with the capacitor.

The material of the article to be treated in the method and apparatus of the present invention may be an organic material such as resin, rubber, etc. in addition to metal and ceramic. Since the plasma of a gas above atmospheric pressure is a very hot thermal plasma,
When processing an article made of a material having relatively low heat resistance such as resin and rubber, for example, a partition wall having a plasma passage hole is provided in a processing container, separating a plasma generation region and an article to be processed, It is conceivable to perform the treatment such that the article is not directly exposed to the high temperature thermal plasma generation region.

In the method and apparatus of the present invention, the combinations shown in Table 1 can be exemplified as the article to be processed, the processing gas that can be used for processing the article, and the type of processing performed thereby.

[0015]

[Table 1]

As the fluorine-containing gas, fluorine (F
₂ ) gas, nitrogen trifluoride (NF ₃ ) gas, sulfur hexafluoride (SF ₆ ) gas, carbon tetrafluoride (CF ₄ ) gas, silicon tetrafluoride (SiF ₄ ) gas, disilicon hexafluoride ( Si ₂
F ₆ ) gas, chlorine trifluoride (ClF ₃ ) gas, hydrogen fluoride (HF) gas and the like.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of an example of a plasma processing apparatus according to the present invention. This apparatus has a pressure-resistant processing vessel 1, in which a heat exchanger 2, a gas circulation fan 3, and a pair of semi-cylindrical main electrodes 41a, 41b for applying high-voltage power are provided. Two sets of preliminary ionization pins 44a and 44b and a workpiece support holder 5 are provided. Since the high pressure gas plasma has a short life, the main electrode 4
1a, 41b and the article support holder 5 to be processed are usually arranged close to each other.

Outside the container 1, a high-voltage DC power supply 42, a capacitor C, a magnetic switch SW, and a coil (inductance) L
And a thyratron 43. The capacitor C, the magnetic switch SW, and the coil L are connected in series to a power supply 42, and a thyratron 43 is connected to the power supply 42 in parallel with the series circuit. In addition, the main electrode 41
a, 41b and two sets of preliminary ionization pins 44a, 44b are connected to the coil L in parallel.

The preionization pins 44a and 44b are each composed of a pair of electrodes having a sharp tip and a capacitor, and are arranged in the container 1 near the main electrodes 41a and 41b. When a DC voltage is applied between electrodes having a relatively large area, discharge and accompanying plasma are unlikely to occur. However, preliminary ionization pins 44a and 44b are arranged near main electrodes 41a and 41b having a relatively large area. By doing so, the preliminary ionization pins 44a and 44b play a role in assisting the start of discharge between the main electrodes 41a and 41b.

The magnetic switch SW acts together with the coil (inductance) L to suppress a rapid current flow to the thyratron 43 and to prevent the thyratron 43 from being damaged. That is, when the thyratron 43 is connected, the impedance of the magnetic switch SW is large at the same time, and then the magnetic switch SW can be changed to a small value. Thus, the thyratron 43 can be protected. High voltage DC power supply 4
2. The capacitor C, the magnetic switch SW, the coil L, the thyratron 43, the main electrodes 41a and 41b, and the two sets of preliminary ionization pins 44a and 44b constitute high voltage power application means.

The processing gas supply unit 6 is connected to the container 1, and the gas supply unit 6 has a regulator 611,
612 and one or more processing gas sources 631, 632,... Connected via valves 621, 622.
・ Is included. Further, a pressure gauge 81 and a pressure adjusting valve 82 are connected to the container 1, and these constitute a pressure adjusting unit 80 for adjusting the pressure inside the container 1.

In carrying out the method of the present invention using this apparatus, the article S to be processed is carried into the container 1 by a transport means (not shown), and the article S is supported by the article support holder 5. Next, a processing gas is introduced into the container 1 from the gas supply unit 6, and one gas is applied between the main electrodes 41a and 41b.
A high voltage power of kV to 50 kV is applied. Main electrode 41
The voltage application between the terminals a and 41b is performed by temporarily charging the capacitor C with the power supplied from the high-voltage power supply 42 and discharging the capacitor C. When starting the discharge, the discharge is first started at the preliminary ionization pins 44a and 44b, and with the help of the discharge, the discharge starts between the main electrodes 41a and 41b. The charging and discharging of the capacitor C is performed by the thyratron 43, and pulse application of high-voltage power is repeated at a period of 10 Hz to 1000 Hz.

In this case, since the thyratron 43 is very weak against overcurrent, the thyratron 4
3 and the impedance of the magnetic switch SW is increased at the same time as the current starts flowing through the thyratron 43.
The impedance of the magnetic switch SW is reduced after several 100 nsec so that the current gradually flows through the thyratron 43.

Thus, the introduced processing gas is turned into plasma, and a predetermined process is performed on the article S under the plasma. During this time, the gas in the container is made uniform by the rotation of the gas circulation fan 3. Further, the atmosphere in the container is sent between the main electrodes 41a and 41b. The direction of rotation of the fan 3 is such that the processing gas is sent toward the article S supported by the article support holder 5 through the space between the main electrodes 41a and 41b. Further, the gas pressure in the container 1 is reduced to 1 kg / cm by discharging the gas in the container to the outside of the container or to a space prepared under an appropriate atmospheric pressure by operating the pressure adjusting valve 82 in the pressure adjusting unit 80. ^{2 ~10kg}
/ Cm ² at a given pressure. During this time, the inside of the container 1 becomes high temperature due to the high-temperature plasma, so that the inside of the container 1 is cooled by the operation of the heat exchanger 2.

According to the above-described method and apparatus, a high-voltage power is applied in a pulsed manner to a processing gas having an atmospheric pressure or a gas pressure higher than substantially atmospheric pressure, whereby the gas can be turned into plasma. As a result, high-density plasma can be efficiently obtained as compared with the low-pressure plasma treatment. Further, since it is not necessary to make the inside of the container 1 a vacuum state, an exhaust device is not required, and a running cost for exhausting by the exhaust device is unnecessary.

FIG. 2 is a diagram showing a schematic configuration of another example of the plasma processing apparatus according to the present invention. This apparatus uses a large-capacity processing vessel 1 in the apparatus shown in FIG. 1, and the inside of the vessel 1 is divided into two parts by a partition wall 11. The partition wall 11 has a hole 11a at the center for allowing plasma to pass therethrough. In place of the article supporting means 5, a reel or a drive table for supporting a long or large article S is provided on the opposite side of the partition wall 11 from the plasma generation area, as described later. You. Other configurations are the same as those of the apparatus in FIG. 1, and the processing operations are also the same. Components having the same configuration and operation as those in the apparatus of FIG. 1 are denoted by the same reference numerals as those in FIG.

When the method of the present invention is carried out using this apparatus, since the volume in the container 1 is large, long or large articles can be treated. On the other hand, it is difficult to perform the plasma processing on the three-dimensional structure, and thus the apparatus shown in FIG. In the illustrated example, the reel R1 and the take-up reel R2 on which the long workpiece S is wound are separated from the main electrode 41a, 41 with respect to the partition wall 11.
It is arranged at a predetermined position on the opposite side to b. The processing on the long article S is performed by exposing the upper surface of the article S to the plasma of the processing gas while sequentially winding the article from the reel R1 to the take-up reel R2. The reels R1 and R2 are separated from the plasma generation region by a partition wall 11. In addition, the drive table can support a large article to be processed, and the drive means can move the drive table in parallel to perform processing on the entire upper surface of the article.

When this apparatus is used, since the plasma generation region and the article to be processed are separated by the partition wall 11, it is possible to process even an article having low heat resistance. Other functions and effects are the same as those of the device shown in FIG. Next, a specific example of the method of the present invention in which the article S is subjected to plasma treatment using the apparatus shown in FIG. 1 in order to improve the wettability of the surface of the article S to be treated made of urethane rubber with water will be described. .

The apparatus conditions common to each embodiment are as follows. Main electrode size and shape Semi-cylindrical shape with radius 50 mm x length 500 mm Distance between main electrodes 41 a and 41 b 28 mm Gas circulation fan 3 rotation speed 500 rpm Example 1 (Surface modification treatment and surface cleaning treatment) Urethane rubber Size 100 mm × 100 mm Applied voltage 25 kV Repetition frequency 200 Hz Container pressure 3 kg / cm ² Processing gas Oxygen (O ₂ ) Processing time 5 min Example 2 (Surface modification and surface cleaning) Article to be processed S material Urethane rubber Size 100 mm × 100 mm Applied voltage 25 kV Repetition frequency 200 Hz Container pressure 3 kg / cm ² Processing gas Hydrogen (H ₂ ) Processing time 5 min Example 3 (Surface modification) Material S to be processed Urethane rubber Size 100 mm × 100 mm Applied voltage 25kV repetition frequency 2 0Hz container pressure 3 kg / cm ² treatment gas sulfur hexafluoride (SF ₆₎ processing time 5min then the article obtained by the plasma treatment of the Examples 1, 2, 3, and identical to an article to be treated S The wettability of the surface of each of the articles (comparative examples) obtained by performing the conventional reduced-pressure plasma treatment using sulfur hexafluoride gas for the same time was evaluated. Water wettability was evaluated by measuring the contact angle of water. The contact angle is the angle between the solid line and the cut line drawn at the liquid at the three-phase contact point of solid, liquid, and gas when the liquid is on the solid surface in air. Which is the angle represented by the angle θ in FIG.

The results are shown in the following table. As described above, the articles obtained by the treatments of Examples 1, 2, and 3 have better surface wettability than the articles obtained by the treatments of the comparative examples, and are decompressed by using a plasma of a gas at about atmospheric pressure or higher. It can be seen that the plasma treatment of the article surface was performed more efficiently than using plasma.

[0031]

As described above, according to the present invention, an expensive exhaust device is not required, and a large-sized article can be subjected to a surface treatment at a low cost without using an expensive exhaust device. Can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an example of a plasma processing apparatus according to the present invention.

FIG. 2 is a diagram showing a schematic configuration of another example of the plasma processing apparatus according to the present invention.

FIG. 3 is a diagram illustrating a contact angle θ indicating a degree of wettability by water.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 High-pressure container 2 Heat exchanger 3 Gas circulation fan 41a, 41b Main electrode 42 High voltage power 43 Thyratron 44a, 44b Preionization pin C Capacitor SW Magnetic switch L Coil 5 Treated article support holder 6 Processing gas supply unit 80 Pressure Adjusting unit 81 Pressure gauge 82 Pressure adjusting valve R1, R2 Reel

Continuation of the front page (56) References JP-A-3-61376 (JP, A) JP-A-7-118857 (JP, A) JP-A-2-50967 (JP, A) JP-A 5-235520 (JP) JP-A-60-116784 (JP, A) JP-A-6-120144 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23C 16/00-16/56 C08J 7/00 H05H 1/46

Claims (8)

(57) [Claims] 1. A The article to be treated was placed in a treatment vessel, together with introducing a processing gas at a pressure of 1kg / cm ² ~10kg / cm ² within the vessel, the vessel internal pressure 1 kg / cm
^While adjusting the pressure to a predetermined pressure of ^{2 to} 10 kg / cm ² , high-voltage power is applied to the gas to convert it into plasma, and the predetermined process is performed on the article under the plasma .
The application of the high voltage power is performed by a discharge disposed in the processing container.
A discharge main electrode pair for assisting the start of discharge between the main electrode pair and the main electrode pair.
The pre-ionization pin including the charging electrode pair is
Connected to the main electrode pair and the preliminary ionization pin.
A plasma processing method, wherein the method is performed by applying a high voltage from the power supply . 2. The plasma processing method according to claim 1, wherein the high-voltage power is applied in a pulse shape. 3. The plasma processing method according to claim 1, wherein the processing gas is converted into plasma while the atmosphere in the processing chamber is stirred and uniformed by a fan installed in the processing chamber. 4. The process is performed while controlling the temperature in the processing vessel by a heat exchange means provided for the vessel.
Or the plasma processing method according to 3. 5. A processing container, an article supporting means provided in the container, and a pressure of 1 kg / cm ² to 1 kg in the container.
Means for supplying processing gas of 0 kg / cm ^2, and means for adjusting the pressure within said vessel to a predetermined pressure of ^{1kg / cm 2 ~10kg / cm 2} , the container by the processing gas supply means the high voltage power is applied to have a high voltage power applying means for plasma the gas to the processing gas introduced into the high-voltage power applying means comprises a high voltage power supply, the
Connected in parallel to a high voltage power supply and placed in the processing vessel
A discharge main electrode pair and a preliminary ionization pin,
The pre-ionization pins are used to assist discharge initiation between the main electrode pairs.
A power electrode pair, and the main electrode pair and a spare
A plasma processing apparatus wherein a high voltage is applied to each of the ionization pins . 6. The plasma processing apparatus according to claim 5, wherein said high voltage power application means applies said high voltage power in a pulsed manner. 7. The plasma processing apparatus according to claim 5, wherein a fan is provided in the processing container to stir and uniformize the atmosphere in the processing container. 8. The plasma processing apparatus according to claim 5, wherein heat exchange means for controlling the temperature inside the processing container is provided for the container.