WO2004079812A1 - Improved method and apparatus for removing contaminants from the surface of a substrate - Google Patents

Improved method and apparatus for removing contaminants from the surface of a substrate Download PDF

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Publication number
WO2004079812A1
WO2004079812A1 PCT/KR2004/000462 KR2004000462W WO2004079812A1 WO 2004079812 A1 WO2004079812 A1 WO 2004079812A1 KR 2004000462 W KR2004000462 W KR 2004000462W WO 2004079812 A1 WO2004079812 A1 WO 2004079812A1
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WO
WIPO (PCT)
Prior art keywords
substrate
plasma generating
plasma
cleaned
processing gas
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PCT/KR2004/000462
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French (fr)
Inventor
Hag-Joo Lee
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Sem Technology Co., Ltd
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Publication date
Application filed by Sem Technology Co., Ltd filed Critical Sem Technology Co., Ltd
Publication of WO2004079812A1 publication Critical patent/WO2004079812A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02041—Cleaning
    • H01L21/02043—Cleaning before device manufacture, i.e. Begin-Of-Line process
    • H01L21/02046—Dry cleaning only
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/32—Gas-filled discharge tubes
    • H01J37/32431—Constructional details of the reactor
    • H01J37/32715—Workpiece holder
    • H01J37/32724—Temperature
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H1/00—Generating plasma; Handling plasma
    • H05H1/24—Generating plasma
    • H05H1/2406—Generating plasma using dielectric barrier discharges, i.e. with a dielectric interposed between the electrodes
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/26—Processing photosensitive materials; Apparatus therefor
    • G03F7/42—Stripping or agents therefor
    • G03F7/427—Stripping or agents therefor using plasma means only
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02041—Cleaning
    • H01L21/02057—Cleaning during device manufacture
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H1/00—Generating plasma; Handling plasma
    • H05H1/24—Generating plasma
    • H05H1/2406—Generating plasma using dielectric barrier discharges, i.e. with a dielectric interposed between the electrodes
    • H05H1/2443—Generating plasma using dielectric barrier discharges, i.e. with a dielectric interposed between the electrodes the plasma fluid flowing through a dielectric tube
    • H05H1/246—Generating plasma using dielectric barrier discharges, i.e. with a dielectric interposed between the electrodes the plasma fluid flowing through a dielectric tube the plasma being activated using external electrodes
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/1316—Methods for cleaning the liquid crystal cells, or components thereof, during manufacture: Materials therefor
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H2245/00—Applications of plasma devices
    • H05H2245/30—Medical applications
    • H05H2245/36—Sterilisation of objects, liquids, volumes or surfaces
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K3/00—Apparatus or processes for manufacturing printed circuits
    • H05K3/0011—Working of insulating substrates or insulating layers
    • H05K3/0055—After-treatment, e.g. cleaning or desmearing of holes

Definitions

  • the present invention relates to a method for removing contaminants from the surface of a substrate and an apparatus used in the method. More precisely, the present invention relates to a method for removing contaminants such as an organic chemical mixture, or a resist using atmospheric pressure plasma and radiant heat to clean the surface of a substrate and an apparatus used in the method.
  • a process to remove contaminants such as an organic chemical mixture or a resist formed on the substrate surface is required in semiconductor processing and it is generally called "cleaning."
  • One example of existing cleaning method is a chemical surface treatment, which has the disadvantage of causing adverse environmental effects.
  • Another example of existing surface cleaning method is surface treatment with low temperature and low pressure plasma. This method generates plasma inside a low pressure chamber, after which the low pressure plasma comes in contact with the substrate to remove contaminants from the substrate surface. Despite its excellent cleaning performance however, this method has not been popularly used because it requires a vacuum apparatus to maintain the low pressure and therefore, cannot be easily applied to consecutive processes performed under atmospheric pressure environment. As a result, research to generate plasma under atmospheric pressure for surface cleaning is being pursued actively.
  • One method of using atmospheric pressure plasma for surface treatment is illustrated by using two metal electrodes wherein at least one of the two electrodes is insulated with a dielectric, and an alternating current is impressed on the electrodes to generate plasma in the plasma generating space (or discharging space) formed between the two electrodes so that the surface of a substrate located inside the plasma generating surface can be treated.
  • Japanese public patent publication 2-15171, 3-241739 or 1-306569 are examples applying the method mentioned above.
  • only very thin substrates can be treated because the substrate needs to be positioned between the two electrodes. For this reason, its application is very limited.
  • the substrate is not a dielectric but a conductive metal or a semiconductor, there is a high risk of substrate damage due to the high voltage applied on the electrodes.
  • US patent 5,185,132 shows a surface treatment method with a reaction vessel with dielectric coated electrodes created by placing solid dielectrics on the surfaces of two or more flat panel electrodes, wherein a mixture of rare and reactive gases is introduced into the said reaction vessel to generate plasma and transfer the active species downstream to treat the surface of a substrate with the said active species.
  • US patent 5,185,132 also shows an apparatus for cleaning the surface of a substrate, comprising of a) at least one pair of electrodes having a dielectric layer their external surfaces; b) a gas supply as a means for supplying processing gas to the plasma generating space formed between these electrodes; c) a power supply for applying alternating current voltage between these electrodes to generate plasma from the processing gas in the plasma generating space whereat least one of these electrodes possesses a curved side that protrudes into the discharging space.
  • the method mentioned above uses a surface treatment apparatus that generates plasma under atmospheric pressure for surface treatment without taking the thermal budget of contaminants such as an organic chemical mixture into account.
  • Korean public patent report 2002-48332 applied by the present inventor shows a surface cleaning method, wherein heated gas directly contacts the substrate surface to be cleaned so that surface to be cleaned is preheated selectively and the preheated surface is cleaned by using atmospheric pressure plasma.
  • this method mentioned has a merit of not causing any damage to the inner circuit formed inside the substrate by preheating the surface to be cleaned selectively using heated gas, it has the disadvantage of having a low preheat efficiency in the case of easily oxidizable BGA substrate, using oxygen as a preheating gas causes oxidation.
  • the objective of the present invention is to address and solve the problems mentioned above. More precisely, the objective of the present invention is to prevent damage caused to a circuit formed inside a substrate, improve the preheating efficiency by selectively preheating a substrate surface to be cleaned among substrate surfaces using reflected heat, and offer an efficient method to remove contaminants, formed on the surface mentioned above, by brining the plasma generated, from the plasma generating source, in contact with the preheated surface.
  • the second objective of the present invention is to offer a surface treatment method, wherein damage on to a circuit, which is formed inside a substrate, is prevented.
  • the preheating efficiency is improved by preheating a substrate surface to be cleaned selectively among substrate surfaces using reflected heat and a substrate is treated regardless of its shape by impressing an alternating current voltage to processing gas, which is introduced into the plasma generating space formed between the two electrodes insulated with a dielectric, to generate plasma, inducing the generated plasma outside of the plasma generating space with flow of the processing gas current, which is introduced into the plasma generating space, and having the plasma contact the surface to be treated.
  • the next objective of the present invention is to offer a surface treatment method that makes it possible to clean the surface of a substrate in a continuous manner by moving a substrate relative to a surface cleaning apparatus (or a plasma generating source).
  • Another objective of the present invention is to offer a surface cleaning apparatus used in the method mentioned above.
  • the first point of view of the invention provides a method comprising of a moving step wherein the substrate is moved relatively to the plasma generating source or the plasma generating source is moved relatively to the substrate, a preheating step wherein heat from a reflecting heat supply is reflected by a reflecting panel and irradiated on to the specific surface to be cleaned among the substrate surfaces so that the surface to be cleaned is selectively preheated, a converting step wherein the processing gas, which is introduced into the plasma generating space formed between the two electrodes insulated with a dielectric, is converted to plasma using an alternating current voltage impressed from an alternating current supply, a removing step wherein the generated plasma is in contact with the preheated substrate surface to be cleaned so that contaminants formed on the surface are removed.
  • the second point of view of the invention provides a method comprising a moving step wherein the substrate is moved relatively to the plasma generating source or the plasma generating source is moved relatively to the substrate, a preheating step wherein heat from a reflecting heat supply is reflected by a reflecting panel and irradiated on to the specific surface to be cleaned among the substrate surfaces so that the surface to be cleaned is selectively preheated, a converting step wherein the processing gas, which is introduced into the plasma generating space formed between the two electrodes insulated with a dielectric, is converted to plasma using an alternating current voltage impressed from an alternating current supply, a removing step wherein the plasma generated in the plasma generating space is induced to outside of the plasma generating space using the flow of the processing gas and contacts the surface to be treated.
  • FIG. la is a cross-sectional view of an example of a desirable embodiment of the surface cleaning apparatus according to the present invention.
  • Fig. 2 is a cross-sectional view showing the principle of the preheating part used in the surface cleaning apparatus.
  • Fig. 3 a is a layout of an example of a desirable embodiment of the atmospheric pressure plasma generating part used in the surface cleaning apparatus.
  • Fig. 3b is another layout of an example of a desirable embodiment of the atmospheric pressure plasma generating part used in the surface cleaning apparatus.
  • Fig. 4 is a graph showing experimental results according to the embodied example 2 using the atmospheric pressure plasma generating part used in the surface cleaning apparatus.
  • the present invention is related to a method removing contaminants from the substrate surface.
  • the method mentioned above is comprised of a moving step wherein the substrate is moved relatively to the plasma generating source or the plasma generating source is moved relatively to the substrate, a preheating step wherein heat from a reflecting heat supply is reflected by a reflecting panel and irradiated on to the specific surface to be cleaned among the substrate surfaces so that the surface to be cleaned is selectively preheated, a converting step wherein the processing gas, which is introduced into the plasma generating space formed between the two electrodes insulated with a dielectric, is converted to plasma using an alternating current voltage impressed from an alternating current supply, a removing step wherein the generated plasma contacts the preheated substrate surface to be cleaned so that contaminants formed on the surface are removed.
  • the method mentioned above is performed by offering a method comprising a moving step wherein the substrate is moved relatively to the plasma generating source or the plasma generating source is moved relatively to the substrate, a preheating step wherein heat from a reflecting heat supply is reflected by a reflecting panel and irradiated on to the specific surface to be cleaned among the substrate surfaces so that the surface to be cleaned is selectively preheated, a converting step wherein the processing gas, which is introduced into the plasma generating space formed between the two electrodes insulated with a dielectric, is converted to plasma using an alternating current voltage impressed from an alternating current supply, inducing step wherein the generated plasma is induced to outside of the plasma generating space using the flow of the processing gas ,and removing step wherein contaminants formed on the surface is removed by having the plasma contact the preheated substrate surface outside the plasma generating space.
  • the present invention also relates to a surface cleaning apparatus used for the said method of removing contaminants from the substrate surface.
  • This apparatus is comprised of a preheating part, wherein the reflected heat is directly irradiated on to the specific surface to be cleaned among the substrate surfaces so that the surface to be cleaned is selectively preheated, and an atmospheric pressure plasma generating part, wherein plasma is generated from a processing gas under atmospheric pressure and induced outside of the plasma generating space using the flow of the processing gas, which is introduced into the plasma generating space.
  • the preheating part is comprised of reflecting panel, which irradiates a reflecting heat source or heat reflected from a reflecting heat source directly on to the specific surface to be cleaned among the substrate surfaces, an atmospheric pressure plasma generating part that is comprised of two electrodes insulated with a dielectric, a plasma generating space formed between the two electrodes, an inlet port introducing a processing gas into the plasma generating space, an outlet port discharging the generated plasma outside the plasma generating space and an alternating current supply impressing alternating current voltage.
  • Fig. 1 is a cross-sectional view of a desirably embodied example a surface cleaning apparatus used for the aforementioned surface cleaning method.
  • the present surface cleaning apparatus 1 is comprised of a preheating part 100 and an atmospheric pressure plasma generating part 200.
  • the preheating part 100 is comprised of a reflective heat source 101 and reflecting panel 102
  • the atmospheric pressure plasma generating part 200 is comprised of two flat panel electrodes 201a, 201b arranged in parallel, a plasma generating space 202 formed between the two electrodes 201a, 201b, dielectrics 203a, 203b insulating the two flat panel electrodes 201a,201b, an inlet port 204 formed on one side of the plasma generating space 202, an outlet port formed on the other side of the inlet port 204 and an alternating current supply 206 impressing alternating current voltage to be used for discharging.
  • the preheating part 100 selectively preheats the surface 2a to be cleaned among the surfaces 2a, 2b of a substrate 2 by radiating the reflected heat from the reflected heat source 101 and irradiating the reflected heat directly on to the surface 2a to be cleaned.
  • the present method could improve the preheating efficiency compared to the preheating method that preheats the lower surface 2b of the substrate 2, and reduce the possibility of damaging circuits by selectively preheating the surface 2a to be cleaned among the surfaces 2a, 2b of the substrate2.
  • the present method has the advantages of yielding a higher preheating efficiency resulting in a shorter preheating time and improved the processing speed.
  • the preheating method of the present invention preheats the specific surface 2a to be cleaned selectively among the surfaces 2a, 2b of the substrate 2 by using reflected heat to loosen the coupling state of organic chemical mixtures so that it helps the atmospheric pressure plasma generating part 200 to perform a much more efficient cleaning.
  • the atmospheric pressure plasma generating part 200 introduces the processing gas into the plasma generating space 202 formed between the two flat panel electrodes 201a, 201b insulated with dielectrics 203a, 203b through the inlet port 204.
  • the processing gas which is introduced into the plasma generating space 202, is converted into the plasma by an alternating current voltage impressed from an alternating current source 206.
  • the generated plasma and processing gas that has not been converted into plasma are induced to outside of the plasma generating space 202 tlirough the outlet port 205 and remove contaminants formed on the surface 2a by contacting the plasma on the preheated substrate surface 2a among the substrate2 surfaces2a, 2b. Meanwhile, the substrate2 mentioned above is moved by a transferring apparatus such as a roller3 so that consecutive surface cleaning is possible.
  • the preheating part 100 mentioned above preheats the surface 2a to be cleaned selectively among the surfaces 2a, 2b of substrate 2 by radiating the reflected heat 103 from a reflected heat sourcelOl using the reflecting panel 102 and irradiating the reflected heat directly on to the surface 2a to be cleaned.
  • a reflected heat source using a nickel-chrome wire or carbon as a heater or an infrared reflected heat source such as quartz halogen lamp could be referred to.
  • the reflected heat 103 from a reflected heat source 101 is radiated by the reflecting panel 102 and preheats the surface2a to be cleaned selectively among the surfaces 2a, 2b of the substrate 2.
  • an existing heating apparatus that uses reflected heat such as those as shown in the previously mentioned US patent 5,155,336, 6,023,555 and 6,122,440, could be used under the condition that the reflected heat 103 radiated by the reflecting panel 102 preheats the surface 2a to be cleaned selectively among the surfaces 2a, 2b of the substrate 2. More preferably, as shown on Fig.1, Fig.2, it should have a concaved reflecting panel 102 to focus the reflected heat 103 from a reflected heat source 101 on to the substrate 2 surface.
  • the specific surface 2a to be cleaned is selectively preheated among the surfaces 2a, 2b of the substrate 2. That is, by preheating a specific part A to be cleaned selectively among substrate surfaces with reflected heat, the preheating efficiency can be additionally improved and side effects caused from preheating parts or areas that do not need to be treated, could be avoided..
  • the ratio of a distance LI between a substrate 2 and a reflected heat source 101 to a distance L2 between a reflected heat source 101 and a reflecting panel 102, that is, L1/L2 is adjusted in the range within 1 through 10.
  • ratios under 1 selective preheating by a reflecting panel 102 is not easy and for ratios over 10, the preheating efficiency is reduced because the distance LI between a substrate 2 and a reflected heat source 101 is too far. More preferably, the ratio mentioned above should be adjusted to be within the range of 3 through 5.
  • the ratio of a width L3 between a reflected heat source 101 and a reflecting panel 102 to its length L2, that is, L3/L2 is adjusted to be within the range of 2 through 0.5, more preferably, adjusted to be within the range of 3/2 through 2/3.
  • focusing the reflected heat is not easy and for ratios under 0.5, the area to be heated become excessively narrow.
  • the substrate 2 in the heating part whose specific surface 2a has been selectively preheated to be cleaned is moved to the adjoining atmospheric pressure plasma generating part 100 by using a transporting apparatus such as a roller3.
  • the surface cleaning apparatusl could also be moved while the substratel stays fixed, as needed.
  • a substrate2, moved to the atmospheric pressure plasma generating part 100 is contacted with the discharged plasma through an outlet port 205 and contaminants on the substrate 2 are removed.
  • the processing gas which is introduced into the plasma generating space 202 formed between the two electrodes 201a, 201b insulated with dielectrics 203a, 203b through an inlet port 204, is converted into plasma by discharging of the alternating current voltage impressed from an alternating current supply.
  • the generated plasma is induced to outside of the plasma generating space 202 through an outlet port 205 with the flow of the processing gas current and removes contaminants formed on the preheated surface 2a by contacting with the surface 2a preheated selectively among moving substrates in the preheating part.
  • processing gases that are generally used to generate plasma in this field are nitrogen, a mixture of nitrogen and oxygen, a mixture of nitrogen and air, rare gases or a mixture of nitrogen and a rare gas.
  • nitrogen gas, a mixture of nitrogen and oxygen, a mixture of nitrogen and air are more preferable.
  • oxidizing gases such as oxygen, ozone, air, carbon dioxide, steam or nitric oxide (N 2 O) could be used alone or used with nitrogen.
  • the most preferable mixture in terms of economics and cleaning efficiency using plasma would be to use nitrogen mixed with 1 to 10% of air.
  • the frequency of the alternating current supply 206 applying alternating current voltage to the electrode 201a is in the range of 50Hz ⁇ 200MHz.
  • Plasma discharge could be unstable for frequencies below 50Hz and arc discharging could be caused from the significantly high plasma temperatures reached at frequencies above 200MHz.
  • a preferable frequency would be in the range of 2kHz ⁇ 100MHz and the most preferable frequency is in the range of 5kHz ⁇ 100MHz.
  • the applied voltage could be chosen properly with regards to the distance between the two electrodes 201a, 201b, the total area of the electrodes, the converting efficiency of plasma and the type of insulators used. It is generally adjusted within the range of lkV ⁇ 40kV.
  • Plasma discharge hardly occurs at voltages below than lkV and the insulator could be damaged at voltages greater than 40k V.
  • the preferable voltage is within the range of 2kV ⁇ lOkV and the most preferable voltage is within the range of 2 kV ⁇ 8 kV.
  • impedance matching is not necessary to attain high frequency and voltage, allowing the apparatus to be more simplified and cost effective.
  • Both pulsed and sine wave voltage shapes may be used for the wave shape formed in the alternating current supply 206, but they should not be considered as the only options for use.
  • the surface temperature of the electrodes (401a, 401b) should be maintained below 250°C but more favorably below 200°C. At surface temperatures above 250°C, the electrodes (201a, 201b) could become deformed and cause arc discharge to occur. Although the lower limit for the electrodes' surface temperature is not particularly defined, additional cooling costs could incur in order to maintain surface temperatures below room temperature.
  • Surface cooling of the electrodes (201a, 201b) is achieved by installing a heat proof machines (207a, 207b) around the electrodes (201a, 201b). Surface cooling of the electrodes (201a, 201b) is performed through circulation of air, water or refrigerant.
  • Air circulation is preferable for low electric power impressed from the alternating current supply (206) and circulation of water or refrigerant is preferable for high electric power impressed from the alternating current supply (206).
  • the heatproof machine (207) for the grounded electrode (201b) may not be required when using low power.
  • the two flat panel electrodes (201a, 201b) are insulated by the insulators (203a, 203b). Although 2 insulators (203a, 203b) are used in fig.1, the electrodes (201a, 201b) could be insulated by one insulator. This fact should be clear for an expert who has general knowledge in this field.
  • the insulators (203 a, 203b) insulating materials with lower than an inductive coefficient of 2000 are preferable but it does not need to be limited to a specific value.
  • MgO, MgF 2 , CaF 2 , LiF, alumina, glass, and ceramic are some examples of such materials. The use of oxidized magnesium is especially favorable in maintaining stability.
  • an insulator containing oxidized magnesium sintered body manufactured with a mixture of ceramic powders like alumina and a small amount (0.01-5 vol%) of oxidized magnesium and sintering the mixture referred to above may be used.
  • an inductive material containing oxidized magnesium can be manufactured by coating oxidized magnesium film onto the inductive substrate surface like alumina or quartz through sputtering, electron-beam deposition or heat injection.
  • the preferable thickness of the insulators (203a, 203b) is in the range of 0.1 mm ⁇ 2 mm.
  • inner voltage of the insulators (203a, 203b) could be lowered or insulators (203a, 203b) could crack or peeled off leading to difficulties in maintaining the uniformity of the glow discharge.
  • inner voltage of insulators (203a, 203b) could be excessively increased.
  • Connection between the insulators (203a, 203b) and the electrodes (201a, 201b) could be performed through common methods such as fusion-bonding method, ceramic-spraying method, the electrode materials (for example, copper, silver, aluminum, gold, platinum, palladium, molybdenum, tungsten or alloy of these) spraying method, chemical-vapor deposition, or physical vapor deposition.
  • the electrode materials for example, copper, silver, aluminum, gold, platinum, palladium, molybdenum, tungsten or alloy of these
  • the plasma generating part in the present invention is comprised of two electrodes insulated with a dielectric, a plasma generating space formed between the two electrodes, an inlet port introducing a processing gas into the plasma generating space, an outlet port discharging the generated plasma outside the plasma generating space and an alternating current supply impressing alternating current voltage needed to discharge.
  • the plasma generating part could be transformed variously under the condition wherein the plasma discharged through an outlet port is contacted with the moving substrate.
  • a flow homogenizing apparatus which introduces the processing gas into the plasma generating space 202 through fine holes with a diameter of about 1mm, could be installed for uniform plasma generation in the plasma generating space 202 and uniform plasma emission through the outlet port 205.
  • the plasma processing width could be improved by using the cylindrical electrode referred to in detail in the US Patent 6,424,091.
  • the plasma generating part it is most preferable to have the plasma generating part to have high efficiency of plasma generation per unit area and improved processing width at the same time.
  • Fig. 3 a is squinted view of another desirably embodied example of the atmospheric pressure plasma generating part used in the surface cleaning apparatus shown on Fig. 1.
  • the atmospheric pressure plasma generating part is comprised of the upper and lower flat panel electrodes 201a, 201b arranged in parallel, the plasma generating space202, which is formed between these two electrodes201a, 201b, the insulators 203a, 203b connecting these two electrodes201a, 201b, the inlet port204a, 204b, formed on both sides of the plasma generating space202, the outlet port205a ⁇ 205e, "205" formed on the lower electrode201b, and the alternating current supply206 impressing the alternating current voltage needed for discharge.
  • the atmospheric pressure plasma generating part shown on Fig. 3a offers new advantage compared to the atmospheric pressure plasma generating part shown on Fig. 1. More precisely, the distance (W) between the two electrodes in the atmospheric pressure plasma generating part shown on Fig. 1 is significantly limited by the applied voltage so that the processing width is hardly improved. However the atmospheric pressure plasma generating part shown on Fig. 3 a has the advantage of improving the processing width without any noticeable affect from the applied voltage. More precisely, although the applied voltage's influence limits the distance (W) between the two electrodes to 0.01 mm ⁇ 30 mm, the length of the electrode (D) is hardly affected by the applied voltage, allowing its length to be significantly greater.
  • the total processing width (D1+D2+D3+D4+D5) can be remarkably increased.
  • the shape of the outlet port in the present invention can be created in the form of a circle, triangle, oval, or any other shape without modifying any part of the apparatus except for the heatproof machine. Therefore, the shape of the outlet port 205 has the advantage of easily being able to be modified according to the shape of the substrate to be processed. Therefore, the shape of the outlet port 205 has the advantage of easily being able to be modified according to the shape of the substrate to be processed.
  • Fig 3b shows an example in which the outlet port 205 is created with having multiple holes. Meanwhile, the inlet ports 204a, 204b are located on both sides of the insulator instead of on both sides of the plasma generating space in Fig.3c.
  • a processing gas storage container is additionally added to supply stable processing gas into the plasma generating space.
  • the surface cleaning apparatus could be used for removing the contaminants like an organic material or resist from the substrate surface. For instance, it could be applied to PCB strip and lead frame cleaning, pre-cleaning process of large area glass panels used for TFT-LCD, and removing resist loaded on large area glass panels used for TFT-LCD. Moreover, it could be applied to all packaging steps of the semiconductor manufacturing process such as bonding, molding, soldering, chip attaching, dipping and marking process.
  • a preheating part could be arranged parallel to more than 2 plasma generating parts, a plasma generating part could be arranged parallel to more than 2 preheating parts and more than 2 preheating parts and plasma generating parts could be arranged in various combinations in the surface cleaning apparatus according to the present invention.
  • the present invention is mentioned more precisely with embodied examples and experimental examples to explain the present invention more in detail, the range of the present invention is not limited to these examples. Various types of complementing set ups and transformations are possible within the range referred to in the present patent claims.
  • Preheating is performed by employing the surface cleaning apparatus shown on Fig. 1.
  • the reflecting heat source has 4mm of diameter and halogen lamp as a heat generator and supplies 1KW electric power to the reflecting heat source.
  • a stainless steel semicircle panel, which is coated with gold, is used as a reflecting panel and its diameter is 28 mm.
  • Distance between a reflecting panel and a reflecting heat source is 15mm and distance between a reflecting heat source and PCB substrate is 30mm.
  • Length of a PCB substrate is 50mm and the entire surface of a substrate to be treated is preheated.
  • Preheating temperature is set to 100°C and temperature on the substrate surface is measured using an infrared thermometer.
  • Temperature on the substrate surface is controlled by installing a controller between a reflecting heat source and a power supply supplying electric power to the reflecting heat source mentioned above.
  • Alumina with 0.635 mm thickness is used as an insulator.
  • As a metal electrode a metal foil formed by coating silver(Ag)-palladium(Pd) on one side of the alumina. Gap of the discharging space is set to 0.4 mm. Nitrogen gas is injected with 80 liter/minute mass flux as processing gas.
  • the voltage value of the alternating current source is set to 10 kV, the frequency is set to 8 kHz and the discharging power is set to 200 W in the present experiment.
  • the degree of cleaning was evaluated by measuring the contact angle to water while changing the moving velocity of a substrate.
  • Contact angle to water is maintained less than 30° with 400 cm/min moving velocity of a substrate. Surface cleaning through an atmospheric pressure plasma generating part is performed without preheating for comparison. For 200 cm/min substrate velocity, the contact angle is less than 30° so that it gave sufficient cleaning effect. Meanwhile, for a substrate with velocity faster than 250 cm/min, the contact angle is higher than 40°, an insufficient cleaning performance.
  • a resist coated on a silicon wafer is removed using the surface cleaning apparatus shown on Fig.1 through the same method in the embodied example 2 except using 85 1pm nitrogen and 5 1pm air as processing gas and maintaining the preheating temperature at 100 °C.
  • the resist removal rate according to temperature is shown on Fig.4.
  • the resist removal rate is increased about 2 times for temperatures in the range 72 °C to 100 °C.
  • the surface cleaning method and the apparatus in the present invention could perform rapid surface cleaning without thermal expansion by preheating the surface to be cleaned among the substrate surfaces selectively with a reflected heat and performing cleaning under atmospheric pressure without any damage to the substrate with plasma, which is generated through dielectric discharge under atmospheric pressure. And continuous surface cleaning is possible by moving a substrate relatively to the surface cleaning apparatus mentioned above.
  • the present surface cleaning method has an advantage of performing cleaning without regard to the shape of a substrate by impressing an alternating current voltage to the processing gas, which is introduced into the plasma generating space formed between the two electrodes insulated with a dielectric, to generate atmospheric pressure plasma, inducing the generated plasma to outside of the plasma generating space with flow of the processing gas current, which is introduced into the plasma generating space, and contacting it on to the surface to be treated.

Abstract

The present invention provides an improved method and an apparatus for removing contaminants from a surface of a substrate. The method according to the present invention comprises the steps of moving a substrate relatively to a plasma generating source or a plasma generating source, preheating selectively the surface to be cleaned among surfaces of the substrate with a radiant heat generated from a radiant heat source and reflected by a reflecting panel, converting a processing gas, which is introduced into a plasma generating space formed between the two electrodes insulated with a dielectric, into plasma using an alternating current voltage impressed from an alternating current supply, and removing contaminants formed on the surface by contacting the preheated surface of the substrate to be cleaned with the plasma. The method could improve preheating efficiency by preheating the surface to be cleaned selectively and prevent damage to the circuit, which is formed inside the substrate, by thermal expansion. Moreover, the processing efficiency could be remarkably improved by selectively preheating the surface to be cleaned with a radiant heat from a radiant heat source.

Description

IMPROVED METHOD AND APPARATUS FOR REMOVING CONTAMINANTS FROM THE SURFACE OF A SUBSTRATE
TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for removing contaminants from the surface of a substrate and an apparatus used in the method. More precisely, the present invention relates to a method for removing contaminants such as an organic chemical mixture, or a resist using atmospheric pressure plasma and radiant heat to clean the surface of a substrate and an apparatus used in the method.
BACKGROUND OF THE INVENTION
A process to remove contaminants such as an organic chemical mixture or a resist formed on the substrate surface is required in semiconductor processing and it is generally called "cleaning." One example of existing cleaning method is a chemical surface treatment, which has the disadvantage of causing adverse environmental effects. Another example of existing surface cleaning method is surface treatment with low temperature and low pressure plasma. This method generates plasma inside a low pressure chamber, after which the low pressure plasma comes in contact with the substrate to remove contaminants from the substrate surface. Despite its excellent cleaning performance however, this method has not been popularly used because it requires a vacuum apparatus to maintain the low pressure and therefore, cannot be easily applied to consecutive processes performed under atmospheric pressure environment. As a result, research to generate plasma under atmospheric pressure for surface cleaning is being pursued actively. One method of using atmospheric pressure plasma for surface treatment is illustrated by using two metal electrodes wherein at least one of the two electrodes is insulated with a dielectric, and an alternating current is impressed on the electrodes to generate plasma in the plasma generating space (or discharging space) formed between the two electrodes so that the surface of a substrate located inside the plasma generating surface can be treated. Japanese public patent publication 2-15171, 3-241739 or 1-306569 are examples applying the method mentioned above. However, according to these examples of the said method, only very thin substrates can be treated because the substrate needs to be positioned between the two electrodes. For this reason, its application is very limited. Furthermore, when the substrate is not a dielectric but a conductive metal or a semiconductor, there is a high risk of substrate damage due to the high voltage applied on the electrodes.
To overcome these disadvantages, another method was proposed wherein the plasma generated within a plasma generating space was induced outside of the plasma generating space where it then came in contact with the substrate whose surface was treated thereafter. US patent 5,185,132 shows a surface treatment method with a reaction vessel with dielectric coated electrodes created by placing solid dielectrics on the surfaces of two or more flat panel electrodes, wherein a mixture of rare and reactive gases is introduced into the said reaction vessel to generate plasma and transfer the active species downstream to treat the surface of a substrate with the said active species. US patent 5,185,132 also shows an apparatus for cleaning the surface of a substrate, comprising of a) at least one pair of electrodes having a dielectric layer their external surfaces; b) a gas supply as a means for supplying processing gas to the plasma generating space formed between these electrodes; c) a power supply for applying alternating current voltage between these electrodes to generate plasma from the processing gas in the plasma generating space whereat least one of these electrodes possesses a curved side that protrudes into the discharging space. However, the method mentioned above uses a surface treatment apparatus that generates plasma under atmospheric pressure for surface treatment without taking the thermal budget of contaminants such as an organic chemical mixture into account.
One attempt to improve the cleaning efficiency by preheating the contaminants formed on the substrate surface is can be illustrated by installing a heater inside a suscepter, on which a substrate is loaded for preheating. US patent 6,479,408 can be referred to as an example of such a method. However, this method installs a heater on the lower part of the substrate and heats the opposite side of the surface to be cleaned by heat conduction, instead of selectively preheating the surface to be treated among the substrate surfaces. Therefore, the preheat efficiency in this method is significantly decreased since the present method preheats the side of the substrate, where preheating is not necessary, and in addition to the surface to be preheated, the circuit formed inside a substrate is also inevitably heated leading to possible damage from thermal expansion. Meanwhile, although US patent 5,155,336, 6,023,555 and 6,122,440 show heating apparatuses to preheat a substrate with reflected heat, according to the presented documents, the preheat efficiency in the present method is decreased, as mentioned above, because these methods preheat a surface from the opposite side of the surface to be cleaned instead of preheating the surface to be treated selectively and, as mentioned above, circuits formed inside a substrate could be damaged by thermal expansion.
Meanwhile, Korean public patent report 2002-48332 applied by the present inventor shows a surface cleaning method, wherein heated gas directly contacts the substrate surface to be cleaned so that surface to be cleaned is preheated selectively and the preheated surface is cleaned by using atmospheric pressure plasma. Although this method mentioned has a merit of not causing any damage to the inner circuit formed inside the substrate by preheating the surface to be cleaned selectively using heated gas, it has the disadvantage of having a low preheat efficiency in the case of easily oxidizable BGA substrate, using oxygen as a preheating gas causes oxidation.
SUMMARY OF THE INVENTION
Therefore, the objective of the present invention is to address and solve the problems mentioned above. More precisely, the objective of the present invention is to prevent damage caused to a circuit formed inside a substrate, improve the preheating efficiency by selectively preheating a substrate surface to be cleaned among substrate surfaces using reflected heat, and offer an efficient method to remove contaminants, formed on the surface mentioned above, by brining the plasma generated, from the plasma generating source, in contact with the preheated surface.
The second objective of the present invention is to offer a surface treatment method, wherein damage on to a circuit, which is formed inside a substrate, is prevented. The preheating efficiency is improved by preheating a substrate surface to be cleaned selectively among substrate surfaces using reflected heat and a substrate is treated regardless of its shape by impressing an alternating current voltage to processing gas, which is introduced into the plasma generating space formed between the two electrodes insulated with a dielectric, to generate plasma, inducing the generated plasma outside of the plasma generating space with flow of the processing gas current, which is introduced into the plasma generating space, and having the plasma contact the surface to be treated.
The next objective of the present invention is to offer a surface treatment method that makes it possible to clean the surface of a substrate in a continuous manner by moving a substrate relative to a surface cleaning apparatus (or a plasma generating source).
Another objective of the present invention is to offer a surface cleaning apparatus used in the method mentioned above.
The first point of view of the invention provides a method comprising of a moving step wherein the substrate is moved relatively to the plasma generating source or the plasma generating source is moved relatively to the substrate, a preheating step wherein heat from a reflecting heat supply is reflected by a reflecting panel and irradiated on to the specific surface to be cleaned among the substrate surfaces so that the surface to be cleaned is selectively preheated, a converting step wherein the processing gas, which is introduced into the plasma generating space formed between the two electrodes insulated with a dielectric, is converted to plasma using an alternating current voltage impressed from an alternating current supply, a removing step wherein the generated plasma is in contact with the preheated substrate surface to be cleaned so that contaminants formed on the surface are removed.
The second point of view of the invention provides a method comprising a moving step wherein the substrate is moved relatively to the plasma generating source or the plasma generating source is moved relatively to the substrate, a preheating step wherein heat from a reflecting heat supply is reflected by a reflecting panel and irradiated on to the specific surface to be cleaned among the substrate surfaces so that the surface to be cleaned is selectively preheated, a converting step wherein the processing gas, which is introduced into the plasma generating space formed between the two electrodes insulated with a dielectric, is converted to plasma using an alternating current voltage impressed from an alternating current supply, a removing step wherein the plasma generated in the plasma generating space is induced to outside of the plasma generating space using the flow of the processing gas and contacts the surface to be treated.
BRIEF DESCRIPTION OF THE DRAWINGS Fig. la is a cross-sectional view of an example of a desirable embodiment of the surface cleaning apparatus according to the present invention.
Fig. 2 is a cross-sectional view showing the principle of the preheating part used in the surface cleaning apparatus.
Fig. 3 a is a layout of an example of a desirable embodiment of the atmospheric pressure plasma generating part used in the surface cleaning apparatus.
Fig. 3b is another layout of an example of a desirable embodiment of the atmospheric pressure plasma generating part used in the surface cleaning apparatus.
Fig. 4 is a graph showing experimental results according to the embodied example 2 using the atmospheric pressure plasma generating part used in the surface cleaning apparatus.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is related to a method removing contaminants from the substrate surface. The method mentioned above is comprised of a moving step wherein the substrate is moved relatively to the plasma generating source or the plasma generating source is moved relatively to the substrate, a preheating step wherein heat from a reflecting heat supply is reflected by a reflecting panel and irradiated on to the specific surface to be cleaned among the substrate surfaces so that the surface to be cleaned is selectively preheated, a converting step wherein the processing gas, which is introduced into the plasma generating space formed between the two electrodes insulated with a dielectric, is converted to plasma using an alternating current voltage impressed from an alternating current supply, a removing step wherein the generated plasma contacts the preheated substrate surface to be cleaned so that contaminants formed on the surface are removed.
More preferably, the method mentioned above is performed by offering a method comprising a moving step wherein the substrate is moved relatively to the plasma generating source or the plasma generating source is moved relatively to the substrate, a preheating step wherein heat from a reflecting heat supply is reflected by a reflecting panel and irradiated on to the specific surface to be cleaned among the substrate surfaces so that the surface to be cleaned is selectively preheated, a converting step wherein the processing gas, which is introduced into the plasma generating space formed between the two electrodes insulated with a dielectric, is converted to plasma using an alternating current voltage impressed from an alternating current supply, inducing step wherein the generated plasma is induced to outside of the plasma generating space using the flow of the processing gas ,and removing step wherein contaminants formed on the surface is removed by having the plasma contact the preheated substrate surface outside the plasma generating space. The present invention also relates to a surface cleaning apparatus used for the said method of removing contaminants from the substrate surface. This apparatus is comprised of a preheating part, wherein the reflected heat is directly irradiated on to the specific surface to be cleaned among the substrate surfaces so that the surface to be cleaned is selectively preheated, and an atmospheric pressure plasma generating part, wherein plasma is generated from a processing gas under atmospheric pressure and induced outside of the plasma generating space using the flow of the processing gas, which is introduced into the plasma generating space. The preheating part is comprised of reflecting panel, which irradiates a reflecting heat source or heat reflected from a reflecting heat source directly on to the specific surface to be cleaned among the substrate surfaces, an atmospheric pressure plasma generating part that is comprised of two electrodes insulated with a dielectric, a plasma generating space formed between the two electrodes, an inlet port introducing a processing gas into the plasma generating space, an outlet port discharging the generated plasma outside the plasma generating space and an alternating current supply impressing alternating current voltage.
Fig. 1 is a cross-sectional view of a desirably embodied example a surface cleaning apparatus used for the aforementioned surface cleaning method. As shown on Fig. 1, the present surface cleaning apparatus 1 is comprised of a preheating part 100 and an atmospheric pressure plasma generating part 200. The preheating part 100 is comprised of a reflective heat source 101 and reflecting panel 102, and the atmospheric pressure plasma generating part 200 is comprised of two flat panel electrodes 201a, 201b arranged in parallel, a plasma generating space 202 formed between the two electrodes 201a, 201b, dielectrics 203a, 203b insulating the two flat panel electrodes 201a,201b, an inlet port 204 formed on one side of the plasma generating space 202, an outlet port formed on the other side of the inlet port 204 and an alternating current supply 206 impressing alternating current voltage to be used for discharging.
The preheating part 100 selectively preheats the surface 2a to be cleaned among the surfaces 2a, 2b of a substrate 2 by radiating the reflected heat from the reflected heat source 101 and irradiating the reflected heat directly on to the surface 2a to be cleaned. The present method could improve the preheating efficiency compared to the preheating method that preheats the lower surface 2b of the substrate 2, and reduce the possibility of damaging circuits by selectively preheating the surface 2a to be cleaned among the surfaces 2a, 2b of the substrate2. Furthermore, compared to the heating method in which the heated gas directly contacts the surface to be treated, the present method has the advantages of yielding a higher preheating efficiency resulting in a shorter preheating time and improved the processing speed. More precisely, the preheating method of the present invention preheats the specific surface 2a to be cleaned selectively among the surfaces 2a, 2b of the substrate 2 by using reflected heat to loosen the coupling state of organic chemical mixtures so that it helps the atmospheric pressure plasma generating part 200 to perform a much more efficient cleaning.
The atmospheric pressure plasma generating part 200 introduces the processing gas into the plasma generating space 202 formed between the two flat panel electrodes 201a, 201b insulated with dielectrics 203a, 203b through the inlet port 204. The processing gas, which is introduced into the plasma generating space 202, is converted into the plasma by an alternating current voltage impressed from an alternating current source 206. The generated plasma and processing gas that has not been converted into plasma are induced to outside of the plasma generating space 202 tlirough the outlet port 205 and remove contaminants formed on the surface 2a by contacting the plasma on the preheated substrate surface 2a among the substrate2 surfaces2a, 2b. Meanwhile, the substrate2 mentioned above is moved by a transferring apparatus such as a roller3 so that consecutive surface cleaning is possible.
A more detailed description of the preheating part 100 mentioned above can be seen in Fig.2, and can be described as follows. The preheating part 100 mentioned above preheats the surface 2a to be cleaned selectively among the surfaces 2a, 2b of substrate 2 by radiating the reflected heat 103 from a reflected heat sourcelOl using the reflecting panel 102 and irradiating the reflected heat directly on to the surface 2a to be cleaned. As examples of the reflected heat source 101, a reflected heat source using a nickel-chrome wire or carbon as a heater or an infrared reflected heat source such as quartz halogen lamp could be referred to. The reflected heat 103 from a reflected heat source 101 is radiated by the reflecting panel 102 and preheats the surface2a to be cleaned selectively among the surfaces 2a, 2b of the substrate 2. At this point, an existing heating apparatus that uses reflected heat such as those as shown in the previously mentioned US patent 5,155,336, 6,023,555 and 6,122,440, could be used under the condition that the reflected heat 103 radiated by the reflecting panel 102 preheats the surface 2a to be cleaned selectively among the surfaces 2a, 2b of the substrate 2. More preferably, as shown on Fig.1, Fig.2, it should have a concaved reflecting panel 102 to focus the reflected heat 103 from a reflected heat source 101 on to the substrate 2 surface. By employing a concaved reflecting panel 102, the specific surface 2a to be cleaned is selectively preheated among the surfaces 2a, 2b of the substrate 2. That is, by preheating a specific part A to be cleaned selectively among substrate surfaces with reflected heat, the preheating efficiency can be additionally improved and side effects caused from preheating parts or areas that do not need to be treated, could be avoided.. The ratio of a distance LI between a substrate 2 and a reflected heat source 101 to a distance L2 between a reflected heat source 101 and a reflecting panel 102, that is, L1/L2 is adjusted in the range within 1 through 10. For ratios under 1, selective preheating by a reflecting panel 102 is not easy and for ratios over 10, the preheating efficiency is reduced because the distance LI between a substrate 2 and a reflected heat source 101 is too far. More preferably, the ratio mentioned above should be adjusted to be within the range of 3 through 5. The ratio of a width L3 between a reflected heat source 101 and a reflecting panel 102 to its length L2, that is, L3/L2 is adjusted to be within the range of 2 through 0.5, more preferably, adjusted to be within the range of 3/2 through 2/3. For ratios over 2, focusing the reflected heat is not easy and for ratios under 0.5, the area to be heated become excessively narrow.
The substrate 2 in the heating part whose specific surface 2a has been selectively preheated to be cleaned is moved to the adjoining atmospheric pressure plasma generating part 100 by using a transporting apparatus such as a roller3. The surface cleaning apparatusl could also be moved while the substratel stays fixed, as needed. A substrate2, moved to the atmospheric pressure plasma generating part 100, is contacted with the discharged plasma through an outlet port 205 and contaminants on the substrate 2 are removed. More precisely, the processing gas, which is introduced into the plasma generating space 202 formed between the two electrodes 201a, 201b insulated with dielectrics 203a, 203b through an inlet port 204, is converted into plasma by discharging of the alternating current voltage impressed from an alternating current supply. The generated plasma is induced to outside of the plasma generating space 202 through an outlet port 205 with the flow of the processing gas current and removes contaminants formed on the preheated surface 2a by contacting with the surface 2a preheated selectively among moving substrates in the preheating part.
Examples of processing gases that are generally used to generate plasma in this field are nitrogen, a mixture of nitrogen and oxygen, a mixture of nitrogen and air, rare gases or a mixture of nitrogen and a rare gas. From an economic point of view, nitrogen gas, a mixture of nitrogen and oxygen, a mixture of nitrogen and air are more preferable. To remove resist formed on a substrate, oxidizing gases, such as oxygen, ozone, air, carbon dioxide, steam or nitric oxide (N2O) could be used alone or used with nitrogen. The most preferable mixture in terms of economics and cleaning efficiency using plasma would be to use nitrogen mixed with 1 to 10% of air.
The frequency of the alternating current supply 206 applying alternating current voltage to the electrode 201a is in the range of 50Hz ~ 200MHz. Plasma discharge could be unstable for frequencies below 50Hz and arc discharging could be caused from the significantly high plasma temperatures reached at frequencies above 200MHz. A preferable frequency would be in the range of 2kHz ~ 100MHz and the most preferable frequency is in the range of 5kHz ~ 100MHz. The applied voltage could be chosen properly with regards to the distance between the two electrodes 201a, 201b, the total area of the electrodes, the converting efficiency of plasma and the type of insulators used. It is generally adjusted within the range of lkV~40kV. Plasma discharge hardly occurs at voltages below than lkV and the insulator could be damaged at voltages greater than 40k V. The preferable voltage is within the range of 2kV ~ lOkV and the most preferable voltage is within the range of 2 kV ~ 8 kV. Moreover, by adjusting the frequency and voltage range to 2 kHz ~ 100kHz and 2 kV ~ 10 kV respectively, impedance matching is not necessary to attain high frequency and voltage, allowing the apparatus to be more simplified and cost effective. Both pulsed and sine wave voltage shapes may be used for the wave shape formed in the alternating current supply 206, but they should not be considered as the only options for use.
The surface temperature of the electrodes (401a, 401b) should be maintained below 250°C but more favorably below 200°C. At surface temperatures above 250°C, the electrodes (201a, 201b) could become deformed and cause arc discharge to occur. Although the lower limit for the electrodes' surface temperature is not particularly defined, additional cooling costs could incur in order to maintain surface temperatures below room temperature. Surface cooling of the electrodes (201a, 201b) is achieved by installing a heat proof machines (207a, 207b) around the electrodes (201a, 201b). Surface cooling of the electrodes (201a, 201b) is performed through circulation of air, water or refrigerant. Air circulation is preferable for low electric power impressed from the alternating current supply (206) and circulation of water or refrigerant is preferable for high electric power impressed from the alternating current supply (206). The heatproof machine (207) for the grounded electrode (201b) may not be required when using low power.
The two flat panel electrodes (201a, 201b) are insulated by the insulators (203a, 203b). Although 2 insulators (203a, 203b) are used in fig.1, the electrodes (201a, 201b) could be insulated by one insulator. This fact should be clear for an expert who has general knowledge in this field. As for the insulators (203 a, 203b), insulating materials with lower than an inductive coefficient of 2000 are preferable but it does not need to be limited to a specific value. For reference, MgO, MgF2, CaF2, LiF, alumina, glass, and ceramic are some examples of such materials. The use of oxidized magnesium is especially favorable in maintaining stability. For an insulator containing oxidized magnesium, sintered body manufactured with a mixture of ceramic powders like alumina and a small amount (0.01-5 vol%) of oxidized magnesium and sintering the mixture referred to above may be used. And an inductive material containing oxidized magnesium can be manufactured by coating oxidized magnesium film onto the inductive substrate surface like alumina or quartz through sputtering, electron-beam deposition or heat injection. The preferable thickness of the insulators (203a, 203b) is in the range of 0.1 mm~ 2 mm. For an insulator thinner than 0.1 mm, inner voltage of the insulators (203a, 203b) could be lowered or insulators (203a, 203b) could crack or peeled off leading to difficulties in maintaining the uniformity of the glow discharge. For an insulator thicker than 2 mm, inner voltage of insulators (203a, 203b) could be excessively increased.
Connection between the insulators (203a, 203b) and the electrodes (201a, 201b) could be performed through common methods such as fusion-bonding method, ceramic-spraying method, the electrode materials (for example, copper, silver, aluminum, gold, platinum, palladium, molybdenum, tungsten or alloy of these) spraying method, chemical-vapor deposition, or physical vapor deposition.
The plasma generating part in the present invention is comprised of two electrodes insulated with a dielectric, a plasma generating space formed between the two electrodes, an inlet port introducing a processing gas into the plasma generating space, an outlet port discharging the generated plasma outside the plasma generating space and an alternating current supply impressing alternating current voltage needed to discharge. The plasma generating part could be transformed variously under the condition wherein the plasma discharged through an outlet port is contacted with the moving substrate. For instance, a flow homogenizing apparatus, which introduces the processing gas into the plasma generating space 202 through fine holes with a diameter of about 1mm, could be installed for uniform plasma generation in the plasma generating space 202 and uniform plasma emission through the outlet port 205. Furtheπnore, the plasma processing width could be improved by using the cylindrical electrode referred to in detail in the US Patent 6,424,091.
It is most preferable to have the plasma generating part to have high efficiency of plasma generation per unit area and improved processing width at the same time.
Fig. 3 a is squinted view of another desirably embodied example of the atmospheric pressure plasma generating part used in the surface cleaning apparatus shown on Fig. 1. As shown on Fig. 3 a, the atmospheric pressure plasma generating part is comprised of the upper and lower flat panel electrodes 201a, 201b arranged in parallel, the plasma generating space202, which is formed between these two electrodes201a, 201b, the insulators 203a, 203b connecting these two electrodes201a, 201b, the inlet port204a, 204b, formed on both sides of the plasma generating space202, the outlet port205a~205e, "205" formed on the lower electrode201b, and the alternating current supply206 impressing the alternating current voltage needed for discharge. The atmospheric pressure plasma generating part shown on Fig. 3a offers new advantage compared to the atmospheric pressure plasma generating part shown on Fig. 1. More precisely, the distance (W) between the two electrodes in the atmospheric pressure plasma generating part shown on Fig. 1 is significantly limited by the applied voltage so that the processing width is hardly improved. However the atmospheric pressure plasma generating part shown on Fig. 3 a has the advantage of improving the processing width without any noticeable affect from the applied voltage. More precisely, although the applied voltage's influence limits the distance (W) between the two electrodes to 0.01 mm ~ 30 mm, the length of the electrode (D) is hardly affected by the applied voltage, allowing its length to be significantly greater. Therefore, the total processing width (D1+D2+D3+D4+D5) can be remarkably increased. Furthermore, although for the atmospheric pressure plasma generating part shown on Fig. 1, changing the shape of the outlet port205 was difficult because it required a great deal of modification to be made to the apparatus, the shape of the outlet port in the present invention can be created in the form of a circle, triangle, oval, or any other shape without modifying any part of the apparatus except for the heatproof machine. Therefore, the shape of the outlet port 205 has the advantage of easily being able to be modified according to the shape of the substrate to be processed. Therefore, the shape of the outlet port 205 has the advantage of easily being able to be modified according to the shape of the substrate to be processed. Fig 3b shows an example in which the outlet port 205 is created with having multiple holes. Meanwhile, the inlet ports 204a, 204b are located on both sides of the insulator instead of on both sides of the plasma generating space in Fig.3c. For the atmospheric pressure plasma generating part shown on Fig. 3, a processing gas storage container is additionally added to supply stable processing gas into the plasma generating space.
The surface cleaning apparatus according to the present invention could be used for removing the contaminants like an organic material or resist from the substrate surface. For instance, it could be applied to PCB strip and lead frame cleaning, pre-cleaning process of large area glass panels used for TFT-LCD, and removing resist loaded on large area glass panels used for TFT-LCD. Moreover, it could be applied to all packaging steps of the semiconductor manufacturing process such as bonding, molding, soldering, chip attaching, dipping and marking process.
A preheating part could be arranged parallel to more than 2 plasma generating parts, a plasma generating part could be arranged parallel to more than 2 preheating parts and more than 2 preheating parts and plasma generating parts could be arranged in various combinations in the surface cleaning apparatus according to the present invention. Hereinafter, although the present invention is mentioned more precisely with embodied examples and experimental examples to explain the present invention more in detail, the range of the present invention is not limited to these examples. Various types of complementing set ups and transformations are possible within the range referred to in the present patent claims.
Example 1
Preheating is performed by employing the surface cleaning apparatus shown on Fig. 1. The reflecting heat source has 4mm of diameter and halogen lamp as a heat generator and supplies 1KW electric power to the reflecting heat source. A stainless steel semicircle panel, which is coated with gold, is used as a reflecting panel and its diameter is 28 mm. Distance between a reflecting panel and a reflecting heat source is 15mm and distance between a reflecting heat source and PCB substrate is 30mm. Length of a PCB substrate is 50mm and the entire surface of a substrate to be treated is preheated. Preheating temperature is set to 100°C and temperature on the substrate surface is measured using an infrared thermometer. Temperature on the substrate surface is controlled by installing a controller between a reflecting heat source and a power supply supplying electric power to the reflecting heat source mentioned above. Alumina with 0.635 mm thickness is used as an insulator. As a metal electrode, a metal foil formed by coating silver(Ag)-palladium(Pd) on one side of the alumina. Gap of the discharging space is set to 0.4 mm. Nitrogen gas is injected with 80 liter/minute mass flux as processing gas. The voltage value of the alternating current source is set to 10 kV, the frequency is set to 8 kHz and the discharging power is set to 200 W in the present experiment. The degree of cleaning was evaluated by measuring the contact angle to water while changing the moving velocity of a substrate. Contact angle to water is maintained less than 30° with 400 cm/min moving velocity of a substrate. Surface cleaning through an atmospheric pressure plasma generating part is performed without preheating for comparison. For 200 cm/min substrate velocity, the contact angle is less than 30° so that it gave sufficient cleaning effect. Meanwhile, for a substrate with velocity faster than 250 cm/min, the contact angle is higher than 40°, an insufficient cleaning performance.
Example 2
A resist coated on a silicon wafer is removed using the surface cleaning apparatus shown on Fig.1 through the same method in the embodied example 2 except using 85 1pm nitrogen and 5 1pm air as processing gas and maintaining the preheating temperature at 100 °C. The resist removal rate according to temperature is shown on Fig.4. The resist removal rate is increased about 2 times for temperatures in the range 72 °C to 100 °C.
The surface cleaning method and the apparatus in the present invention could perform rapid surface cleaning without thermal expansion by preheating the surface to be cleaned among the substrate surfaces selectively with a reflected heat and performing cleaning under atmospheric pressure without any damage to the substrate with plasma, which is generated through dielectric discharge under atmospheric pressure. And continuous surface cleaning is possible by moving a substrate relatively to the surface cleaning apparatus mentioned above. Furthermore, according to the more preferable embodied example based on the present invention, the present surface cleaning method has an advantage of performing cleaning without regard to the shape of a substrate by impressing an alternating current voltage to the processing gas, which is introduced into the plasma generating space formed between the two electrodes insulated with a dielectric, to generate atmospheric pressure plasma, inducing the generated plasma to outside of the plasma generating space with flow of the processing gas current, which is introduced into the plasma generating space, and contacting it on to the surface to be treated.

Claims

1. A method of removing contaminants from a surface of a substrate, comprising the steps of moving a substrate relatively to a plasma generating source or a plasma generating source, preheating selectively the surface to be cleaned among surfaces of the substrate with a radiant heat generated from a radiant heat source and reflected by a reflecting panel, converting a processing gas, which is introduced into a plasma generating space formed between the two electrodes insulated with a dielectric, into plasma using an alternating current voltage impressed from an alternating current supply, and removing contaminants formed on the surface by contacting the preheated surface of the substrate to be cleaned with the plasma.
2. The method as set forth in claim 1, wherein the step of removing contaminants formed on the surface by contacting preheated substrate surface to be cleaned with the plasma is carried out by driving the plasma generated to outside of the plasma generating space with the aid of the flow of the processing gas, followed by removing contaminants formed on the surface by contacting the plasma with the preheated substrate surface at outside of the plasma generating space.
3. The method as set forth in claim 1, wherein the contaminants are an organic compound or a resist.
4. The method as set forth in claim 1 or 2, wherein the substrate is a semiconductor.
5. The method as set forth in claim 1 or 2, wherein the substrate is PCB strip or leadframe.
6. The method as set forth in claim 1 or 2, wherein the substrate is a glass panel for TFT-LCD.
7. The method as set forth in claim 1 or 2, wherein frequency and voltage of the alternating current supply are respectively in a range of 50Hz ~ 200MHz of and lkV ~ 40kV.
8. The method as set forth in claim 1 or 2, wherein frequency and voltage of the alternating current supply are respectively in a range of 5kHZ ~ 100kHz and 2kV ~ lOkV.
9. A surface cleaning apparatus comprising a preheating part in which a radiant heat is directly irradiated on to a surface to be cleaned so that the surface to be cleaned is selectively preheated and an atmospheric pressure plasma generating part in which plasma is generated from a processing gas under atmospheric pressure and is driven to outside of a plasma generating space with a aid of flow of the processing gas introduced into the plasma generating space, wherein the preheating part is comprised of a radiant heat source and a reflecting panel which reflects a radiant heat from the radiant heat source on to the surface to be cleaned in order to directly irritate the surface to be cleaned, and the atmospheric pressure plasma generating part is comprised of two electrodes insulated with a dielectric, a plasma generating space formed between the two electrodes, an inlet port introducing a processing gas into the plasma generating space, an outlet port through which plasma is driven to outside of the plasma generating space and an alternating current supply impressing alternating current voltage, the plasma driven throughout the outlet port removes contaminants by contacting the preheated surface.
10. The surface cleaning apparatus as set forth in claim 9, wherein both of the two electrodes are flat panel electrodes, the outlet port is formed inside of one of the electrodes and the substrate to be cleaned is positioned under the flat electrode inside which the outlet port is formed.
11. surface cleaning apparatus as set forth in claim 9, further including a storage container to store the processing gas in order to stably supply the processing gas into the plasma generating space and the storage container supplies the processing gas into the plasma generating space through the inlet port formed on the dielectric.
PCT/KR2004/000462 2003-03-06 2004-03-05 Improved method and apparatus for removing contaminants from the surface of a substrate WO2004079812A1 (en)

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WO2012010299A1 (en) * 2010-07-21 2012-01-26 Dow Corning France Plasma treatment of substrates
WO2012146348A1 (en) * 2011-04-27 2012-11-01 Dow Corning France Plasma treatment of substrates

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KR100764036B1 (en) * 2006-02-24 2007-10-05 주식회사 케이씨텍 Dry cleaning module for large-substrate and cleaning apparatus and method to use the cleaning module
KR100755517B1 (en) * 2006-10-09 2007-09-05 성균관대학교산학협력단 Highdensity plasma generaror apparatus for using atmospheric remote plasma

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2012010299A1 (en) * 2010-07-21 2012-01-26 Dow Corning France Plasma treatment of substrates
CN102986304A (en) * 2010-07-21 2013-03-20 道康宁法国公司 Plasma treatment of substrates
JP2013538288A (en) * 2010-07-21 2013-10-10 ダウ コーニング フランス Plasma treatment of substrate
WO2012146348A1 (en) * 2011-04-27 2012-11-01 Dow Corning France Plasma treatment of substrates
CN103609203A (en) * 2011-04-27 2014-02-26 道康宁法国公司 Plasma treatment of substrates
JP2014514454A (en) * 2011-04-27 2014-06-19 ダウ コーニング フランス Plasma treatment of substrate

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KR20040079029A (en) 2004-09-14

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