WO2005003848A1

WO2005003848A1 - The process for cleaning a glass surface in manufacturing lcd

Info

Publication number: WO2005003848A1
Application number: PCT/KR2003/001335
Authority: WO
Inventors: Il Soon Kwak; Jae Bok Lee
Original assignee: Sfa Engineering Corp.
Priority date: 2003-07-01
Filing date: 2003-07-07
Publication date: 2005-01-13
Also published as: KR20030095365A; KR100412258B1; AU2003246104A1

Abstract

The present invention relates to a method of cleaning an LCD substrate, and more particularly, to a method of cleaning an LCD substrate using ozonized-electrolyzed water and ultrasonic wave. A method of cleaning an LCD substrate according to the present invention comprises steps of producing electrolyzed water using an electrolyzed water generator, producing ozonized water using an ozonized water generator, mixing and agitating the electrolyzed water and the ozonized water to produce the ozonized-electrolyzed water, activating the ozonized-electrolyzed water using an ultrasonic wave generator, cleaning the LCD substrate by spraying the activated ozonized-electrolyzed water onto the LCD substrate using an ozonized-electrolyzed water spraying unit, and recovering and filtering off the ozonized-electrolyzed water used in the LCD substrate cleaning step so as to be reused in the electrolyzed water producing process.

Description

THE PROCESS FOR CLEANING A GLASS SURFACE IN MANUFACTURING LCD

TECHNICAL FIELD The present invention relates to a method of cleaning a substrate of LCD manufacturing process, and more particularly, to a method of cleaning a substrate by using ozonized-electrolyzed water. In general, an LCD is an element using a kind of optical switching phenomenon that liquid crystal, which is intermediary material of solid and liquid, is interposed between two thin glass plates and then molecular arrangement is changed to create light and dark effect and thereby display a character or an image.

BACKGROUND ART Driving method of LCD is classified into a passive matrix method and an active matrix method. Then, such a passive matrix method includes a TN (Twisted Nematic) type and an STN (Super Twisted Nematic) type, and the active matrix method includes a TFT (Thin Film Transistor) type. In recent, with increase of demand for a TFT LCD, a research for improving performance of the TFT LCD has been carried out. Accordingly, after 1990s, a research for the TFT LCD has proceeded with concentration on a large screen, a large viewing angle, a high aspect ratio, and the like, and this tendency will be continued hereafter. A process for manufacturing an LCD is broadly classified into a Cell process where an LCD panel itself is produced and a Module process where a completed panel is assembled into a finished product. In the Cell process, on a substrate Glass, cleaning, depositing, and etching processes are repeatedly carried out to make a patterning, and thus TFT

Glass and C/F Glass are manufactured. Because produced TFT and CF pattern are results of fine process comprising root of an LCD, it is necessary to remove impurities in each process. Two glasses produced through the aforementioned processes are bound together using a spacer injected therebetween, and then liquid crystal is injected into a space defined by the spacers. The module process is to produce a finished TFT panel as a module. That is, the module is completed through processes of attaching an LCD driving IC and a backlight. The aforementioned cleaning process, which might be taken to each individual process of the LCD manufacturing process, is an important process on which improvement of yield depends. As described above, current cleaning process is used in each of an LCD Glass manufacturing process and C/F process, and is repeatedly carried out by seven or eight times on the whole. In the cleaning process, DIW (Deionized Water) or chemicals which are called TMAH being a kind of surfactant is used as a cleaning solution. Primary cleaning target of the chemicals is a particle causing disconnection or short circuit leak in the TFT-LCD using an a-Si, an organic matter such as oilpaper lowering adhesion of thin film, a natural oxidation film deteriorating contact characteristic, and so forth. If such impurities are not removed completely, pattern defect on an array substrate or operation failure of the transistor may frequently occur, thereby decreasing an yield of the array substrate. Thus, it is important to select cleaning method, cleaning facilities, or cleaning process suitable for each cleaning object. Presently, as compared with semiconductor cleaning, a cleaning process used in a TFT-LCD manufacturing process depends on only simple cleaning method that cleaning using DIW is simply repeated several times. Accordingly, it is impending to develop cleaning technology suitable for every film used in TFT-LCD manufacturing process and to develop cleaning technology capable of maximizing performance of a TFT-LCD. Conventionally, first, particle and metallic impurities are removed by using chemical, and second, chemical remnant is removed through Rinse process using DIW, and third UV process is carried out to remove organic. However, there are problems with great cost used for every process, and urgent needs to develop an improved cleaning technology since an LCD using low-temperature Poly- Si TFT may require a level of cleaning process similar to that of a semiconductor. Alternatively, Radical, which is generated when SiO₂ film is deposited on a Glass substrate, a Poly-Si layer is deposited, or Laser heating and Lithography processes are carried out after deposition, may prevent physical and chemical bonding between thin films and cause decrease of yield. Chemical and physical cleaning process used for obviating such radical causes crystalline defect of thin film and ion remnants, such that performance is deteriorated and yield decreases. Therefore, it is required to introduce a wet-cleaning method using EW (Electrolyzed Water), which is a new cleaning method not generating ions while being environment-affinitive. Recently, in response to requirement of environmental preservation and lower manufacturing cost, decrease of chemical-cost is gradually raised as an important issue. In accordance with such changes of surrounding, it is required to develop new cleaning solution and decrease chemical density, while pollutant cleanup capacity in conventional cleaning process using liquid is maintained. Thus, in nineteen-nineties, there have been suggested various physical cleanings (e.g., ultrasonic wave cleaning) having additional new function and lower cleaning cost, wet cleaning, and dry cleaning. Of such cleaning methods, there is a cleaning method using TMAH (Tetra Methyl Ammonium Hydro-oxide), but, presently, the above-described chemical is greatly used together with DIW and physical cleaning applied thereto. While cleaning capacity of the cleaning method is gradually improved, because there is problem with great DIW use in the case of applying the cleaning method to whole LCD mass-manufacturing process, there are unsolved problems with cleaning capacity, running cost of cleaning process, or contaminated water removing generated from cleaning process. Alternatively, since many kinds of chemicals are greatly used in a current TFT-LCD surface processing, there have always been problems associated with cost of chemical, cost of post-processing, safety of an operator, induction of environmental pollution, and the like. That is, since great wastewater and waste are produced due to greatly various kinds of chemical and great water used in cleaning process, the above- described problems, that is, problems with increase of cost, safety of an operator, induction of pollution may occur. Therefore, in a point of view that pollutant is not originally produced, rather than cleanup of produced pollutant, it is greatly required to develop new process not producing pollutant. America already set a definite action for regulating generation of pollutant, and a joint research between government and enterprise is made by SEMATECH and thus reaches a reasonable level of solution. Japan also progresses actively joint development business with the help of the Board of Trade, and presently, fifty percent or more of chemical and freshwater is reused. While studying material and data and making a basic research insignificantly, home industries greatly depend on foreign nation because of technological inferior of material and equipment industries. Nevertheless, home industries passively face to them with optimization of current process. Namely, in practical, home industries have never developed an alternative technology and a technology for improving a process so as to alleviate generation of pollutant produced from TFT-LCD manufacturing process.

DISCLOSURE OF INVENTION Accordingly, it is an object of the present invention to provide a cleaning method that is environment affinitive and uses little chemical. It is another object of the present invention to provide a cleaning method where cost is cut due to little chemical use and simplified processing. It is still another object of the present invention to provide a cleaning method where used water is reused to decrease use of DI substantially. It is still yet another object of the present invention to provide an ozonized water generator capable of being used everywhere by using a common power source.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagram illustrating a structure of an ozonized water generator according to the present invention; Fig. 2 is a diagram illustrating a structure of an ozonized water spraying unit according to the present invention; Fig. 3 is a diagram illustrating a process of semiconductor manufacturing processes, to which a cleaning method according to the present invention is applied; Fig. 4 is a partially enlarged view of the cleaning unit according to the present invention; Fig. 5 is a diagram generally illustrating primary processes of an LCD; and Fig. 6 is a diagram generally illustrating primary processes of an LCD.

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a method of cleaning an LCD substrate, and more particularly, to a method of cleaning an LCD substrate using ozonized-electrolyzed water which is activated by ultrasonic wave. A method of cleaning an LCD substrate according to the present invention comprises the steps of producing electrolyzed water by using an electrolyzed water generator, producing ozonized water by using an ozonized water generator, mixing and agitating the electrolyzed water and the ozonized water to produce the ozonized-electrolyzed water, activating the ozonized- electrolyzed water by using an ultrasonic wave generator, cleaning the LCD substrate by spraying the activated ozonized-electrolyzed water onto the LCD substrate by using an ozonized-electrolyzed water spraying unit, and recovering and filtering off the ozonized-electrolyzed water used in the LCD substrate cleaning step so as to be reused in the electrolyzed water producing process. Hereinafter, individual process will be described in detail with reference to the drawings.

(1) Electrolyzed water producing process The present process is to produce electrolyzed water by using an electrolyzed water generator 100. The electrolyzed water is generated by electrolyzing and ionizing DI with an oxidative ion, such as H⁺ and a reductive ion, such as OH^", using an ion exchanging film. Thus, electrolyzed water has much broader range of pH and ORP (Oxidation Reduction Potential) without a little chemical addition. Accordingly, the present invention optimizes degree of cleaning by using the above- described electrolyzed water, such that LCD manufacturing productivity is improved and cleaning technology becomes environment affinitive. Also, the electrolyzed water has great cleaning capability because of pH and oxidation-reduction capability required in each step of LCD cleaning process. Further, surface tension is weak since H+ and OH- produced from molecule of electrolyzed water is less than that of general water. Thus, when compared with conventional cleaning method, the present invention is capable of cleaning fine portion due to easier invasion into fine hole Accordingly, degree of integration of LCD can be increased and cleaning effect can be improved.

(2) Ozonized water producing process The present process is to produce ozonized water by using an ozonized water generator 200. Ozone is commonly generated by electric discharge under oxygen. Various kinds of ozone generators have already been developed and supplied to open market. However, conventional ozone generator has a problem with high cost and great volume. A representative method of conventional ozone generating methods is a dielectric barrier discharge method, the dielectric barrier discharge being a kind of corona discharge. That is, the dielectric barrier discharge method is to generate AC discharge after injecting dielectric between electrodes. In the dielectric barrier discharge, the dielectric prevents arc discharge and holds AC discharge. However, surfaces of dielectric and electrode create new capacitance, and thus cause new vibration. Thus, because plasma generated from the dielectric barrier discharge is not uniform, there may be a problem of unreliability. Accordingly, the present invention uses resistive barrier discharge using resistive material. The resistive barrier discharge is to inject resistive material between electrodes. Resistive material decreases vibration in discharge as well as prevents arc discharge. As a result, discharge becomes stable, and uniform and stable plasma is generated. In addition, the resistive barrier discharge has an advantage of alternative selection of AC or DC in accordance with convenience. The present invention is able to use cheap transformer easily purchased in the open market as a power device. For example, neon sign ballast where a specification of transformer has 15keV, 20mA, and 60Hz can be used. Current obtained by the transformer is used as DC after rectifying it or used as AC itself. A broad wire net forms stable discharging space and causes uniform and broad discharge. Almost power is converted into heat during discharge, such that a gas temperature of a discharging area and a barrier temperature between electrodes increase due to such heat. However, the broad wire net used in the present invention broadens the discharging area, so that heat generated during discharging can efficiently be dispersed, and thus gas temperature is held an ambient temperature. There are two methods of producing ozonized water by using the resistive barrier discharging system. First, there is a method generating ozone under oxygen atmosphere where corona discharge induced under oxygen atmosphere generates a lot of ozone. Such ozone is transferred through an exhaust pipe mounted to a discharger into a diffuser positioned in water, and ozone and molecule of oxygen are discharge through the diffuser into water as small gas-drops. Herein, molecule of ozone is dissolved into water and thereby becomes ozonized water. Second, there is the other method where discharge is directly carried out on water surface. An ozoined-water generator using such method has a structure that high voltage source is connected into a wire net electrode and resistive material is attached under the wire net electrode. In the ozonized water generator, when oxygen flows between surface of water and lower surface of the resistive material, corona discharge is generated between the wire net electrode with the resistive material and surface of water grounded. With the corona discharge, oxygen is resolved and ozone is alloyed. Such ozone is dissolved in water and thus ozonized water is produced. Up to this time, water under the resistive material continually flows to generate high density of ozonized water and great ozonized water. The resistive barrier discharge system according to the present invention has an advantage that various layers of the above-described discharge configuration are laminated and thus space is efficiently utilized. Also, because ozone gas is dissolved in water, an ozonized water generator according to the present invention has powerful oxidizing power and bactericidal power and has no outflow ozone gas in atmosphere. As a result, the ozonized water generator is not only innoxious to a human body, but also to environments due to little secondary pollutant. Thus, the present invention is capable of not only taking the place of an UV process of removing harmful substance deteriorating characteristics of semiconductor element or LCD substrate with adhesion to an wafer surface, but also solving cleaning of various industrial facilities, disinfection of hospital laundry, clean up of remained agricultural chemicals, and the like by using ozonized water.

(3) Agitating process The present process is to mix electrolyzed water with ozonized water produced by the electrolyzed water generator 100 and the ozonized water generator 200, respectively. That is, alkaline water produced from a cathode cell 110 of the electrolyzed water generator 100 is mixed with ozonized water, and acid water produced from an anode cell 120 of the electrolyzed water generator 100 is mixed. Accordingly, each mixed solution is agitated by an agitating unit 300, and generated from each electrolyzed water

(4) Ozoneized-electrolyzed water activating process The present process is to activate the ozonized-electrolyzed water by using ultrasonic wave. Namely, ultrasonic wave generated from a megasonic, which is an ultrasonic wave generator 400, is applied to the ozonized-electrolyzed water, so that vibration is applied to the ozonized-electrolyzed water. Ozonized- electrolyzed water to which vibration is applied has powerful cavitation or evacuated acceleration, and thus is able to remove pollutant. In this time, frequency of ultrasonic wave which is applied to activate mixing micro organic matter or inorganic matter adhering to a substrate with ozonized water is controlled to 20 to 100kHz. However, when wavelength of vibration is long, cleaning smear can occur due to a standing wave and damage to a thin film pattern can occur due to power cavitation, such that it is need to be careful.

(5) Clean-up process The present process is to clean up pollutant on the substrate by spraying the activated ozonized-electrolyzed water onto a substrate which needs to be cleaned up. Namely, the present process is to clean up pollutant by spraying the activated ozonized-electrolyzed water onto a surface 700 of a glass by using ozonized-electrolyzed water spraying unit 500. In this time, activated ozonized-electrolyzed water is sprayed through a spraying nozzle 510 provided at the ozonized-electrolyzed water spraying unit 500, and it is preferable that a hole of the spraying nozzle is 0.5 to 3mm in diameter Also, the spraying nozzle 510 is controlled so that the distance between end of the nozzle and the surface 700 of the glass can be 2 to 13mm. Further, as shown in Fig. 2, it is preferable that an angle 520 between a center line of the spraying nozzle and the LCD substrate is adjusted to be 85 to 90. Of ozonized-electrolyzed water, a mixture of alkaline water and ozonized water is taking the place of a chemical in the process of cleaning particles and metallic impurities. In addition, mixture of acid water and ozonized water is taking the place of an UV process of eliminating an organic matter which adheres to glass surface during the cleaning process and thus deteriorates performance of an LCD.

(6) Ozonized water recovering process The present process is to recover and filter off the ozonized water used in the cleaning process of the glass surface 700 so as to be reused in the electrolyzed water and the ozonized water producing processes. Once used ozonized-electrolyzed water becomes similar to original DIW because electrolyte and ozone component are almost consumed during cleaning process. However, recovered ozonized-electrolyzed water is difficult to directly reuse because various pollutant and impurity produced from the cleaning process are included. Thus, the recovered ozonized-electrolyzed water should be filtered and then is possible to be reused in the electrolyzed water producing process and the ozonized water producing process. In this time, DIW having very high pure degree is used in the electrolyzed water producing process and the ozonized water producing process, filtering generator 600 where fine particle can be removed and ion can be removed may be used in the filtering process. However, in the present invention, although electrolyzed water after cleaning process may not be reused, there is an advantage that salt is not produced during mixing of wastewater produced after cleaning process, but neutral water is produced, and thus natural drain is possible without additional purification. Accordingly, the present invention is very environment affinitive. Further, in the above-described process of the present invention, desired cleaning effect can be obtained by activating ozonized water by using an ultrasonic wave generator without using electrolyzed water. Figs. 5 and 6 are diagrams generally illustrating primary processes of an LCD, and processes to which ozonized-electrolyzed water cleaning method of the present invention can be applied is shown with slanting lines. As shown in Figs. 5 and 6, cleaning method of the present invention can be efficiently used in various steps of LCD manufacturing processes. <Best Mode Embodiment Hereinafter, the best mode embodiment will be described. First, DIW is divided by using an electrolyzed water generator 100. In this time, produced alkaline water and acid water are divided through a semi- permeable membrane, and is conveyed through a cathode cell 110 and an anode cell 120. In this time, in the ozonized water generator 200, ozonized water is produced by discharging in oxygen and DIW supplied and the ozonized water is conveyed to the agitating unit 300. The electrolyzed water and the ozonized water which are conveyed to the agitating unit 300 are mixed by the agitating unit 300. The agitated and mixed ozonized-electrolyzed water is conveyed to an ultrasonic wave generator 400. In the ultrasonic wave generator 400, frequency of the ultrasonic wave is controlled to 20 to 100 kHz. Ozonized-electrolyzed water is activated by the ultrasonic wave. Activated ozonized-electrolyzed water is conveyed to an ozonized-electrolyzed water spraying unit 500. The activated ozonized-electrolyzed water which is conveyed to the ozonized-electrolyzed water spraying unit 500 is sprayed onto the LCD substrate which needs to be cleaned. It is preferable that a spraying nozzle of the spraying unit 510 has 0.5mm to 3mm in diameter, distance between nozzle end of the spraying nozzle 510 and glass surface 700 is 2 to 13mm, as shown in Fig. 4, and angle between and center line of the spraying nozzle and the LCD substrate is controlled to be degrees of 85 to 90. Ozonized-electrolyzed water which is used in the cleaning process may be recovered, and filtered by means of the filtering unit 600, and then supplied to the electrolyzed water generator 100 and the ozonized water generator 200 for reuse. The ozonized-electrolyzed water according to the present invention, which is a cleaning water produced by electrolyzing DIW, uses less DIW than a conventional method as well as little chemical. Thus, the present invention optimizes degree of cleaning by using the above-described electrolyzed water having much broader range of pH and ORP

(Oxidation Reduction Potential) without a little chemical addition, such that LCD manufacturing productivity is improved and cleaning technology becomes environment affinitive. Further, according to the present invention, the chemical cost can be cut downed and ratio of defective products can be decreased due to electrolyzed water, thereby reducing economic cost. In addition, the cleaning method according to the present invention is capable of allowing the cleaning power by allowing pH and oxidation-reduction power which is required in each of LCD cleaning processes to cleaning water.

Particularly, H+ and OH- generated by molecules of electrolyzed water have smaller size than conventional water, such that it is easy to invade into fine hole having small surface tension. Thus, it is possible to clean finer portions compared with the related art and increase degree of integration on the LCD substrate. Also, in the cleaning method according to the present invention, process simplification and suppression of DIW amount to be used can be obtained by decreasing the number of cleaning processes which are repeated several times. Further, in the cleaning method according to the present invention, DIW use can be remarkably decreased by reusing water once used in the cleaning process. Thus, industrial environment problem is originally solved by decreasing pollutant in the LCD cleaning process, such that each nation's environmental regulation can be originally coped with. In addition, the ozonized water generator according to the present invention which has a feature of low cost and high efficiency has an advantage that it can be used anywhere by using a common power source. Thus, a small- income farmer or a small-medium company uses generally it without great financial burden due to its economical efficiency.

Claims

WHAT IS CLAIMED IS:

1. A method of cleaning an LCD (Liquid Crystal Display) substrate using ozonized-electrolyzed water, the method comprising steps of: producing the ozonized water by dissolving ozone, which is produced using an ozonized water generator, in deionized water; activating the ozonized water using an ultrasonic wave generator; cleaning the LCD substrate by spraying the activated ozonized water onto the LCD substrate using an ozonized water spraying unit; and recovering and filtering off the ozonized water used in the cleaning step for reuse in the ozonized water producing process.

2. A method of cleaning an LCD (Liquid Crystal Display) substrate using ozonized-electrolyzed water, the method comprising steps of: producing electrolyzed water by electrolyzing deionized water by using an electrolyzed water generator; producing ozonized water using an ozonized water generator; mixing and agitating the electrolyzed water and the ozonized water to produce the ozonized-electrolyzed water; activating the ozonized-electrolyzed water using an ultrasonic wave generator; and cleaning the LCD substrate by spraying the activated ozonized- electrolyzed water onto the LCD substrate using an ozonized-electrolyzed water spraying unit;

3. A method according to claim 2, further comprising a step of recovering and filtering off the ozonized-electrolyzed water used in the LCD substrate cleaning step for reuse in the electrolyzed water producing process.

4. A method according to claim 2, wherein the ozonized-electrolyzed water spraying unit has a spraying nozzle, a hole of which is 0.5mm to 3mm in diameter.

5. A method according to claim 2, wherein the ozonized-electrolyzed water spraying unit is positioned at 2mm to 13mm apart from the LCD substrate.

6. A method according to claim 3, wherein the ozonized-electrolyzed water spraying unit is adjusted to make an angle of 85 to 90 degrees between a center line of the spraying nozzle and the LCD substrate.

7. A method according to claim 2, wherein the electrolyzed water is alkaline water containing OH^" ion or acid water containing H ion, and the ozonized-electrolyzed water is alkaline ozonized-electrolyzed water or acid ozonized-electrolyzed water.

8. A method according to claim 7, wherein the alkaline ozonized- electrolyzed water removes particles or metallic impurities on the LCD substrate.

9. A method according to claim 7, wherein the acid ozonized- electrolyzed water replaces an UV process of removing organic materials, which are adhered to a surface of a glass and thus deteriorate an LCD performance.

10. A method according to claim 2, wherein a variable resistor is provided in the electrolyzed water generator.