KR20020071694A - Method and apparatus for removing contaminants from the surface of a substrate with atmospheric-pressure plasma - Google Patents

Abstract

The present invention relates to a method and apparatus for using atmospheric plasma for surface cleaning of various materials. In the present invention, the plasma generated by the silent discharge method is used to lead out of the discharge space by using a flow of rapid airflow. That is, if one side of the space between the positive electrode, which is the plasma generating space, is used as the inlet for the gas used for discharge, and the other side is the outlet, the directional air flow is applied, the plasma in the discharge space is ejected toward the outlet, and thus the Cleaning of the sample surface located on the outlet side can be performed. Moving the sample relative to the atmospheric plasma generator according to the present invention can obtain the effect of continuously cleaning the surface of the sample. In this manner, the sample can be continuously moved to the sample moving under atmospheric pressure or by the moving atmospheric plasma generator. Cleaning process is possible.

Description

Surface cleaning method and apparatus using atmospheric plasma {METHOD AND APPARATUS FOR REMOVING CONTAMINANTS FROM THE SURFACE OF A SUBSTRATE WITH ATMOSPHERIC-PRESSURE PLASMA}

The present invention relates to a method and apparatus for generating a plasma under atmospheric pressure and using the generated plasma to clean the surface of the material.

The degree of surface cleaning of all materials has a great influence on adhesion and adhesion when other materials are deposited, coated or bonded on the material. Conventional surface cleaning methods have been made using various chemicals, but these methods have been limited in their use due to environmental pollution by chemicals, and thus new surface cleaning methods have been studied and used a lot. One of such new surface cleaning methods is a method using plasma in a low temperature and low pressure state. The surface cleaning method using a low pressure plasma is to remove impurities or contaminants on the surface of the material by contacting the surface of the material with ions or activated gas produced by generating a plasma in a low pressure vacuum chamber. The surface cleaning method using the plasma in the low pressure state is not widely used in spite of the excellent cleaning effect, which requires a vacuum device to generate the low pressure plasma, and thus is applied to the continuous process at atmospheric pressure. Because it is difficult. Accordingly, recent studies have been actively conducted to generate plasma under atmospheric pressure and use it for surface cleaning.

Atmospheric pressure plasma can be generated using a number of methods, the most commonly used method being the silent discharge method that has been used in ozone generators for a long time (Siemens W. 1857, Ann. Phys. Chem. 102 , 66- 122). The principle of silent discharge is well known. When one or both of the metal electrodes are insulated with an insulator and a high voltage alternating current or pulse is applied to the metal electrodes, a high voltage discharge occurs in the space between the two electrodes, thereby causing the plasma to be discharged. It is a principle that occurs. The generated plasma is used to clean the surface of the sample placed in the space between the two electrodes. However, when the electrode structure is used to clean the surface of an actual sample, the sample must be located in the space between both electrodes, so only a very thin plate-like sample can be processed, and thus its application field is very limited. In addition, when the sample is a metal and semiconductor sample having conductivity rather than an insulator, there is a disadvantage that the sample may be damaged by high voltage.

In recent years, in order to overcome the drawbacks of the atmospheric silent discharge, the research is being conducted to generate and use atmospheric plasma using RF power of 13.56 MHz, but the cost of RF power devices is high, impedance matching is required, and the device is complicated. There is a disadvantage of this (US 5,977,715-'Handheld atmospheric pressure glow discharge plasma source', US 5,961,772-'Atmospheric-pressure plasma jet').

Accordingly, an object of the present invention is to provide a new surface cleaning method which overcomes the disadvantages of the above methods, which comprises (a) introducing a used gas into a plasma generating space formed between the metal electrodes insulated with an insulator, (b) applying an alternating current or pulsed high voltage to the metal electrode to generate an atmospheric plasma of the used gas by silent discharge under atmospheric pressure; and (c) generating the atmospheric pressure plasma through the outlet by using a stream of airflow. Spraying out of the generating space, and (d) cleaning the surface of the sample by removing the impurities from the surface of the sample by contacting the ejected atmospheric plasma with a stationary or moving sample. .

It is another object of the present invention to provide an atmospheric pressure plasma generator capable of surface cleaning of a continuous sample which can be used in the above method and having a simple structure.

1 is a structural diagram of a preferred example of a cleaning apparatus using an atmospheric plasma according to the present invention.

FIG. 2 is a graph measuring the contact angle with water of the glass substrate cleaned using nitrogen atmosphere plasma in Example 1 of the present invention.

※ Explanation of codes for main parts of drawing

101: insulator 102: electrode 103: high voltage inverter

104: plasma generating space 105: inlet port 106: outlet port

107: used gas storage container 108: flow regulator 109: flow homogenizer

110: plasma 111: heat sink 112: ground

113: Sample in motion

In general, the simplest method of generating atmospheric pressure plasma is silent discharge. That is, when one or both of the metal electrodes are insulated with an insulator and a high voltage alternating current or pulse is applied to the metal electrodes, plasma is generated by the high voltage discharge of the used gas in the space between the electrodes. Unlike the high temperature arc plasma under atmospheric pressure, the generated plasma has characteristics of low pressure and low temperature plasma, and thus can be used to clean the surface of a sample without being destroyed by the temperature rise of the workpiece. However, since the space in which the plasma is generated is limited to the space between the metal electrodes, space is very limited in using the generated plasma.

In the present invention, the plasma generated by the silent discharge method is intended to be drawn out of the discharge space by using a fast air flow. That is, if one side of the space between the positive electrode, which is the plasma generating space, is used as the inlet of the gas used for discharge and the other is the outlet, the directional air flow is applied, the plasma in the discharge space is ejected toward the outlet. Cleaning of the sample surface located on the outlet side can be performed.

Accordingly, the present invention relates to a surface cleaning method using atmospheric pressure plasma, the method comprising the following steps.

(a) introducing a used gas into a plasma generating space formed between the metal electrodes insulated with an insulator;

(b) applying an alternating current or pulsed high voltage to the metal electrode to generate atmospheric pressure plasma of the gas used by silent discharge under atmospheric pressure;

(c) ejecting the generated atmospheric plasma out of the plasma generating space through an outlet using a stream of airflow; and

(d) A surface cleaning step of removing impurities from the surface of the sample by contacting the ejected atmospheric plasma with a stationary or moving sample.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings and examples. 1 shows a schematic view of a preferred example of a surface cleaning apparatus using an atmospheric pressure plasma according to the present invention, wherein the surface cleaning apparatus 1 includes two metal electrodes 102 facing each other insulated with an insulator 101. A high voltage inverter 103 connected to both ends of the electrode 102, a plasma generation space 104 generated between the two metal electrodes facing each other, and an inlet formed on a side surface of the plasma generation space 104 to correspond to each other; 105) and the flow rate for controlling the flow rate of the gas used between the outlet 106, the used gas storage container 107 for supplying the used gas through the inlet 105, the inlet 105 and the used gas storage container 107 Regulator 108.

First, a high voltage in the form of alternating current or pulse generated from the high voltage inverter 103 which is a high voltage generator is applied to both ends of the metallic electrode 102 covered by the insulator 101. The applied high voltage converts the used gas introduced into the plasma generating space 104 from the used gas storage container 107 through the flow regulator 108 into the plasma generating space 104 by the silent discharge to the plasma 110 under atmospheric pressure. . The generated plasma 110 is ejected out of the plasma generating space 104 through the outlet 106 by the flow of airflow flowing into the plasma generating space 104 through the inlet 105, and ejected the plasma 110. ) Cleans the surface of the stationary or moving sample 113 in contact with the plasma 110.

The surface cleaning apparatus may further include a metallic heat sink 111 attached to the metallic electrode 102 to facilitate the emission of heat generated by the plasma discharge, and the electrode of the side to which the high voltage is not applied is grounded. (112) can be used for safety. In addition, in the surface cleaning apparatus described above, if necessary, a flow homogenizing device 109 is installed at the inlet port 105 so that the use gas introduced into the plasma generating space 104 through the flow regulator 108 is discharged into the plasma generating space 104. It is possible to have a uniform flow of air in the), the flow rate homogenizing device 109 has the effect of improving the ejection uniformity of the atmospheric plasma sprayed on the sample.

The material used for the insulator 101 is not necessarily limited thereto, but a ceramic or plastic such as alumina or glass may be used, and the metallic electrode 102 is not necessarily limited thereto. It may be used as an electrode by vapor deposition or coating, or may be used as an electrode by attaching a thin metal plate such as copper or aluminum. In addition, the insulator 101 can insulate one metal electrode or both electrodes.

The gap of the plasma generating space 104 between the metal electrodes 102 insulated by the insulator 101 is not necessarily limited thereto, but the distance of 0.01 mm or more and 5 mm or less, preferably 0.1 mm or more and 1 mm or less. I use it. For this reason, if a gap of 0.01 mm or less is used, the airflow of the used gas is not smooth and the plasma is not easily ejected, and at a distance of 5 mm or more, a high voltage of too high value of 10 kV or more is required to cause silent discharge. This is because safety in use is a problem and may cause damage to the sample due to high voltage.

The high voltage applied to the metal electrode 102 to generate the atmospheric pressure plasma 110 may be generated using the high voltage inverter 103, and the high voltage applied is not necessarily limited thereto, but it is commercially easy to generate high voltage. A frequency of 60 Hz or more and 100 kHz or less is used, and a high voltage value uses a high voltage of 10 kV or less, which is easy to generate high voltage. In addition, the voltage waveform of the high voltage is not necessarily limited to this, but may use a pulse waveform or a sinusoidal waveform.

The gas flowing in to generate the plasma 110 is not necessarily limited thereto, but may be oxygen, nitrogen, or air as well as inert gases such as helium (He), neon (Ne), argon (Ar), and xenon (Xe). And the like, and one or more mixed gases of these gases may be used.

1 illustrates an example in which one surface cleaning device is installed to clean a sample, but if necessary, two or more surface cleaning devices may be connected in series or in parallel.

Example 1

In order to examine the material surface cleaning effect using the atmospheric pressure plasma according to the present invention, an experiment was carried out using a glass substrate, and the degree of surface cleaning was quantified by measuring the contact angle with water, which is the most direct characteristic after surface cleaning.

The atmospheric plasma generator used in the experiment was alumina of 0.635 mm as an insulator and was formed by coating a metal film on one side of the alumina as an electrode. The clearance gap of the discharge space was 0.4 mm, and nitrogen gas, a gas used for discharge, was introduced at a flow rate of 25 liters / minute. The voltage value of the high voltage inverter was 4 kV, the frequency was 20 kHz, and the discharge power was 100 W. The experiment was performed by varying the distance between the plasma jet port and the sample substrate from 0.5 mm to 2 mm. The surface cleaning effect by atmospheric pressure plasma was measured by changing the moving speed of the sample from 10 cm / min to 50 cm / min.

Figure 2 shows the results of the above, as can be seen in the figure as shown in the sample movement speed of 10 cm / min very clean the surface is very low contact angle with water can be seen that, the movement speed of the sample It can be seen that the surface cleaning effect decreases as the speed increases or as the distance from the sample increases. However, the reduction of the surface cleaning effect can be easily solved by using a plurality of devices according to the present invention, and can also be easily cleaned by using a plurality of samples of a large area.

The surface cleaning method and apparatus according to the present invention described above can be widely applied to surfaces requiring cleaning, and in particular, all processes for general PCB strip and leadframe or packaging, that is, bonding ( Cleaning required for bonding, molding, soldering, chip attaching, dipping, marking, or pre-cleaning of large area glass for TFT-LCD ), It can be applied to the removal of PR (photo-resistor) on the large-area glass for TFT-LCD, ie ashing. In addition, the surface cleaning method and apparatus described above may be applied to a cleaning process and a photo-resistor (PR) removal process in manufacturing a semiconductor.

The material surface cleaning method using atmospheric pressure plasma according to the method of the present invention uses the plasma generated by the silent discharge by ejecting it out of the narrow discharge space using the flow of airflow, so that the application range is very wide and the cleaning effect is very excellent. There is an advantage. In addition, the surface cleaning method of the present invention is not limited to the interior of the discharge space consisting of a small sample position, but only located in the portion where the plasma is ejected, there is little restriction according to the type of sample, and also outside the space where the high voltage electric field exists Since the sample is placed there is an advantage that can prevent the damage of the sample by high voltage. On the other hand, when the sample is moved relative to the atmospheric plasma generator according to the present invention, the surface of the sample can be continuously washed. In this manner, the sample can be moved under atmospheric pressure or by a moving atmospheric plasma generator. Continuous cleaning process is possible.

In addition, the surface cleaning apparatus of the present invention used in the above method has an advantage that it can be economical by having a very simple structure and can be very easily applied to various applications. Specifically, all processes for general PCB strip and leadframe or packaging, ie bonding, molding, soldering, chip attaching, For cleaning required in dipping and marking processes, pre-cleaning of large-area glass for TFT-LCD, photo-resistor removal on large-area glass for TFT-LCD That is, it can be applied to ashing.

Claims (16)

(a) introducing a used gas into a plasma generating space formed between the metal electrodes insulated with an insulator; (b) applying an alternating current or pulsed high voltage to the metal electrode to generate atmospheric pressure plasma of the gas used by silent discharge under atmospheric pressure; (c) ejecting the generated atmospheric plasma out of the plasma generating space through an outlet using a stream of airflow; and (d) A surface cleaning step of removing impurities from the surface of the sample by contacting the ejected atmospheric plasma with a stationary or moving sample. Surface cleaning method using an atmospheric plasma comprising a. The method of claim 1 wherein the insulator is a ceramic or plastic material comprising alumina and glass. The method of claim 1, wherein the metal electrode is in a form in which a metal film is deposited, coated, or attached onto an insulator. The method according to claim 1, wherein the clearance gap of the plasma generating space is 0.01 mm or more and 5 mm or less. The method of claim 1, wherein the high voltage waveform applied for silent discharge is in the form of alternating current or pulse, the frequency is 60 Hz-100 kHz, and the maximum voltage value is 10 kV or less. The method of claim 1, wherein helium (He), neon (Ne), argon (Ar), xenon (Xe), oxygen, nitrogen, air or a mixture of one or more of these gases is introduced into the gas to generate the atmospheric pressure plasma How to use. The method of claim 1, wherein the inlet gas is introduced through a flow homogenizing device that pumps inlet gas into a number of fine pores in order to improve the uniformity of the ejected atmospheric plasma. The method according to claim 1, wherein at least two devices according to the present invention are used in series or in parallel in order to increase the surface cleaning effect using atmospheric plasma. (a) two insulated metal electrodes facing each other, (b) a high voltage inverter connected to the metal electrode to apply a high voltage to both ends of the metal electrode; (c) a plasma generating space formed between the two metal electrodes facing each other, wherein the used gas introduced into the interior is converted into plasma by a high voltage applied by a high voltage inverter; (d) an inlet and an outlet formed on the side of the plasma generating space; (e) a used gas storage container for supplying a used gas through the inlet; (f) a surface cleaning device including a flow controller for controlling the flow rate of the gas used between the inlet and the gas storage container. 10. The apparatus of claim 9, wherein the surface cleaner further comprises a flow rate equalizer that enhances the uniformity of the incoming gas flow. 10. The method of claim 9, wherein the cleaning of the surface is converted into a plasma using a high voltage applied to the metal electrode by a high voltage inverter through a flow regulator from the used gas storage vessel to a plasma, and through the inlet to the plasma generating space A device is achieved by ejecting the generated plasma through an outlet using a stream of airflow flowing into it and contacting the ejected plasma with a stationary or moving sample. 10. The apparatus of claim 9, wherein the apparatus is for cleaning required for processing for normal PCB strips and leadframes or for packaging. 10. The method of claim 9, wherein the general PCB strip and leadframe or packaging process is performed by bonding, molding, soldering, chip attaching. , Dipping or marking process. 10. The apparatus of claim 9, wherein the apparatus is for pre-cleaning treatment of large area glass for TFT-LCDs. 10. The apparatus of claim 9, wherein the apparatus is for removing photo-resistor (PR) on large area glass for TFT-LCDs. 10. The apparatus according to claim 9, wherein the apparatus is for cleaning process and photo-resistor (PR) removal during semiconductor fabrication.