Abstract:
A substrate cleaning system including a carrying unit having a plurality of rollers for carrying a substrate, wherein each of the rollers includes a roller shaft and a plurality of division rollers coupled to the roller shaft, and wherein a gap between adjacent ones of the roller shafts is larger than a radius of each of the division rollers; a first rinse unit located along the carrying unit and configured to apply a first cleaning liquid onto the substrate; and a cleaning unit comprising a slit nozzle and configured to apply a second cleaning liquid to the substrate after it encounters the first rinse unit.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2010-0114531 filed in the Korean Intellectual Property Office on Nov. 17, 2010, the entire contents of which are incorporated herein by reference. 
     BACKGROUND 
     1. Field 
     The described technology relates generally to a system and method for cleaning a substrate. 
     2. Description of Related Art 
     A flat panel display is a thin display device having a flat panel and being relatively thin with respect to other display devices. Typical examples of a flat panel display include a liquid crystal display (LCD), a plasma display device, an organic light emitting diode (OLED) display, etc. 
     A flat panel display includes a display panel for displaying an image, and in order to manufacture such a display panel, various processes, for example, an etching process and a cleaning process are performed. 
     Particularly, when cleaning a silicon oxide film on an amorphous silicon layer that is formed in the OLED display or a silicon oxide film on a polysilicon layer, a spin cleaning method, or a track cleaning method of spraying a hydrofluoric acid (HF) cleaning liquid to a substrate on an in-line with a spray method or of flowing a hydrofluoric acid cleaning liquid with a flow method is used. 
     However, as the OLED display is formed in relatively larger sizes, in a spin cleaning method, it is difficult to rotate a substrate in a high speed, and in a track cleaning method, etching uniformity is difficult due to an etching difference between an intermediate portion and an edge portion of a substrate, and thus a crystallization process of an amorphous silicon layer, which follows the etching and an interface between a polysilicon layer and a gate insulating layer are affected, whereby a problem such as a crystallization stain and an element failure occurs. 
     The above information disclosed in this Background section is only for enhancement of understanding of the background of the described technology and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
     SUMMARY 
     The described technology has been made in an effort to provide a system and method for cleaning a substrate having the characteristics of improving etching uniformity and remarkably reducing a use amount of a cleaning liquid. 
     An exemplary embodiment includes a substrate cleaning system including a carrying unit having a plurality of rollers for carrying a substrate, wherein each of the rollers includes a roller shaft and a plurality of division rollers coupled to the roller shaft, and wherein a gap between adjacent ones of the roller shafts is larger than a radius of each of the division rollers; a first rinse unit located along the carrying unit and configured to apply a first cleaning liquid onto the substrate; and a cleaning unit comprising a slit nozzle and configured to apply a second cleaning liquid to the substrate after it encounters the first rinse unit. 
     Division rollers of the adjacent rollers may be alternately arranged. 
     A silicon layer and a silicon oxide film may be sequentially formed on the substrate. 
     The first cleaning liquid may be ultrapure water or deionized water, and the second cleaning liquid may be an aqueous solution including ammonium fluoride or hydrofluoric acid. 
     A concentration of hydrofluoric acid of the second cleaning liquid may be 0.2% to 2.0%. 
     A width of an ejection opening of the slit nozzle may be 0.1 mm to 2 mm. 
     The slit nozzle may include a hydrofluoric acid resistant material. 
     A second gap between the slit nozzle and an upper surface of the substrate may be 1.5 mm to 5 mm. 
     The cleaning unit may further include an air knife that removes the first cleaning liquid on the substrate; and an aqua knife that removes the second cleaning liquid on the substrate. 
     The substrate cleaning system may further include a second rinse unit that ejects a third cleaning liquid to the substrate that passes through the cleaning unit. 
     The third cleaning liquid may be ultrapure water or deionized water. 
     In another embodiment, a method of cleaning a substrate is provided, the method including loading the substrate onto a carrying unit; moving the substrate under a first rinse unit with the carrying unit and applying a first cleaning liquid to the substrate using the first rinse unit; moving the substrate under a cleaning unit with the carrying unit and applying a second cleaning liquid to the substrate using a slit nozzle of the cleaning unit; and performing a reaction process of the second cleaning liquid while sustaining the substrate to which the second cleaning liquid is applied in a horizontal state. 
     A reaction time period that performs the reaction process may be 5 seconds to 100 seconds. 
     A silicon layer and a silicon oxide film may be sequentially formed on the substrate, and the silicon oxide film may be etched using the second cleaning liquid in the reaction process. 
     The applying of a second cleaning liquid to the substrate may include forming the second cleaning liquid in a predetermined thickness on the substrate. 
     The applying of a second cleaning liquid to the substrate may be performed while sustaining the substrate in a horizontal state. 
     At the applying of a second cleaning liquid to the substrate, a gap between the slit nozzle and an upper surface of the substrate may be 1.5 mm to 5 mm. 
     The method may further includes, after the ejecting of a first cleaning liquid on the substrate, removing the first cleaning liquid from the substrate in which the first cleaning liquid remains using an air knife. 
     The method may further include, after the performing of a reaction process of the second cleaning liquid, removing a reaction material of the second cleaning liquid in which the reaction process is performed using an aqua knife from the substrate. 
     The first cleaning liquid may be ultrapure water or deionized water, and the second cleaning liquid may be an aqueous solution including ammonium fluoride or hydrofluoric acid. 
     A concentration of hydrofluoric acid of the second cleaning liquid may be 0.2% to 2.0%. 
     The method may further include ejecting the third cleaning liquid onto the substrate in which a reaction material of the second cleaning liquid is removed using the second rinse unit. 
     According to an exemplary embodiment, by applying a second cleaning liquid in a uniform thickness only onto a silicon oxide film using a slit nozzle, a use amount of the second cleaning liquid can be remarkably reduced, compared with a conventional spin cleaning method, spray method, or flow method. 
     Further, by minimizing a width of an ejection opening of a slit nozzle and a gap between a slit nozzle and a substrate, a second cleaning liquid of a uniform thickness is applied onto a silicon oxide film and a division roller of one roller of adjacent rollers of a carrying unit is alternately arranged with the other one division roller, a first gap between adjacent roller shafts is larger than a size of a radius of a division roller and is 20 mm or less and thus by reducing an area of a portion in which the division roller and the substrate doe not contact, flatness of the substrate is improved and thus etching uniformity of the silicon oxide film can be improved. 
     Further, while etching uniformity of the silicon oxide film is improved, a method of cleaning a substrate can be applied to a large sized-substrate. 
     Further, because etching uniformity is improved, a crystallization stain and an element failure are prevented from occurring. 
     Further, because the second cleaning liquid is applied only onto a silicon oxide film in a uniform thickness using a slit nozzle and a substrate is stopped under a cleaning unit during a reaction time period, a manufacturing space can be reduced, compared with a conventional spray method, and because a separate slope time period is unnecessary, compared with a conventional flow method, a tact time can be reduced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of a substrate cleaning system according to an exemplary embodiment. 
         FIG. 2  is a top plan view illustrating a carrying unit of the substrate cleaning system of  FIG. 1 . 
         FIGS. 3 to 7  are diagrams sequentially illustrating a method of cleaning a substrate using a substrate cleaning system according to an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. 
     The drawings and description are to be regarded as illustrative in nature and not restrictive. Like reference numerals designate like elements throughout the specification. 
       FIG. 1  is a schematic diagram of a substrate cleaning system according to an exemplary embodiment, and  FIG. 2  is a top plan view illustrating a carrying unit of the substrate cleaning system of  FIG. 1 . 
     As shown in  FIG. 1 , a substrate cleaning system according to an exemplary embodiment includes a carrying unit  100  that carries a substrate  10 , a first rinse unit  200  that positions on the carrying unit  100  and that ejects a first cleaning liquid  20  (see  FIG. 3 ) on the substrate  10 , and a cleaning unit  300  that applies a second cleaning liquid  30  (see  FIG. 4 ) to the substrate  10  that passes through the first rinse unit  200 . 
     A silicon layer  11  of an amorphous silicon layer or a polysilicon layer is formed on the substrate  10 , and a silicon oxide film  12  is formed on the silicon layer  11 . The silicon oxide film  12  is an oxide film that is formed on the silicon layer  11  in a manufacturing process and can be removed using a substrate cleaning system according to an exemplary embodiment. 
     The carrying unit  100  includes a plurality of rollers  110  that are disposed at a predetermined gap, and the roller  110  includes a roller shaft  111  and a plurality of division rollers  112  that are coupled to the roller shaft  111 . 
     As shown in  FIG. 2 , a plurality of roller shafts  111  are oriented parallel to each other, and a plurality of division rollers  112  rotate with a rotation of the roller shaft  111  and rotate the substrate  10  contacting the division roller  112 . The division roller  112  may be made of a material such as rubber having a large friction force or coefficient. 
     The division roller  112  of one roller  110  of adjacent rollers  110  is alternately arranged with another division roller  112 . Therefore, because an area of a portion in which the division roller  112  and the substrate  10  do not contact can be reduced, flatness of the substrate  10  can be improved. 
     Further, a first gap d 1  between adjacent roller shafts  111  is larger than a size of a radius of the division roller  112  and, for example, may be about 20 mm or less. If the first gap d 1  is smaller than a size of a radius of the division roller  112 , the division roller  112  of a first roller  110  of the adjacent rollers  110  contacts a roller shaft  111  of a second roller  110  and thus a friction force occurs. If the first gap d 1  is larger than 20 mm, it is difficult for the roller shaft  111  to appropriately rotate and an area which the division roller  112  does not support the substrate  10  increases, which may cause a cleaning liquid to pool in the area and thus the substrate  10  may be bent due to a weight of the cleaning liquid, whereby flatness of the substrate  10  may be affected. 
     The first rinse unit  200  is separated from the carrying unit  100  to be positioned at an upper part thereof. The first rinse unit  200  includes a first support  210  that is attached to a first fixing frame  1  and a plurality of first ejection portions  220  that are connected to the first support  210  and that eject a first cleaning liquid  20  onto the substrate  10 . The first cleaning liquid  20  may use ultrapure water or deionized water (DI water). The first cleaning liquid  20  that is ejected from the first rinse unit  200  removes a contamination material on a silicon oxide film  12 . 
     The cleaning unit  300  includes an air knife  310  that is attached to the first fixing frame  1 , a slit nozzle  320  that is attached to the first fixing frame  1  and that is located behind the air knife  310  in a traveling direction of the substrate  10 , and an aqua knife  330  that is attached to a second fixing frame  2  that is separated by a gap from the first fixing frame  1 . 
     The air knife  310  removes a residue of the first cleaning liquid  20  on the substrate  10  that is carried under the cleaning unit  300  using a high air pressure. 
     Because a width t of an ejection opening  321  of the slit nozzle  320  is a small width of about 0.1 mm to 2 mm, the second cleaning liquid  30  is ejected onto the substrate  10  in a substantially uniform thickness. Further, because a second gap d 2  between the ejection opening  321  of the slit nozzle  320  and an upper surface of the substrate  10 , i.e., the silicon oxide film  12  is a small size of 1.5 mm to 5 mm, the second cleaning liquid  30  that is ejected from the slit nozzle  320  is applied in a substantially uniform thickness onto the silicon oxide film  12 . The second cleaning liquid  30  is an aqueous solution including ammonium fluoride (NH 4 F) or hydrofluoric acid (HF), and a concentration of hydrofluoric acid of the aqueous solution may be 0.2% to 2.0%. Because the second cleaning liquid  30  is an aqueous solution including ammonium fluoride (NH 4 F) or hydrofluoric acid (HF), the slit nozzle  320  is made of a hydrofluoric acid resistant material. The second cleaning liquid  30  that is applied in a substantially uniform thickness is deformed into a reaction material  31  that is separated from the silicon layer  11  by reacting with the silicon oxide film  12  under the second cleaning liquid  30 . 
     The aqua knife  330  removes the reaction material  31  of the second cleaning liquid  30  on the substrate  10  using DI water of a high water pressure. 
     A second rinse unit  400  is disposed at the rear side of the cleaning unit  300  in a travel direction of the substrate  10 . The second rinse unit  400  is separated from the carrying unit  100  to be positioned at an upper part thereof and includes a second support  410  that is attached to the second fixing frame  2  and a plurality of second ejection portions  420  that are connected to the second support  410  and that eject a third cleaning liquid  40  onto the substrate  10 . The third cleaning liquid  40  can use ultrapure water or DI water. 
     The third cleaning liquid  40  that is ejected from the second rinse unit  400  removes a contamination material or a residue of the reaction material  31  on the silicon layer  11 . 
     In this way, because a substrate cleaning system according to an exemplary embodiment applies the second cleaning liquid  30  in a substantially uniform thickness only onto the silicon oxide film  12  using the slit nozzle  320 , an amount of the second cleaning liquid  30  used can be remarkably reduced, compared with a conventional spin cleaning method, spray method, or flow method. 
     Further, by minimizing a width t of the ejection opening  321  of the slit nozzle  320  and the second gap d 2  between the slit nozzle  320  and the substrate  10 , the second cleaning liquid  30  of a substantially uniform thickness is applied onto the silicon oxide film  12 , and the division roller  112  of one roller  110  of the adjacent rollers  110  of the carrying unit  100  is alternately arranged with the other one division roller  112 , and because the first gap d 1  between the adjacent roller shafts  111  is larger than a size of a radius of the division roller  112  and is 20 mm or less, an area of a portion in which the division roller  112  and the substrate  10  do not contact is minimized, and thus flatness of the substrate  10  is maximized, whereby etching uniformity of the silicon oxide film  12  can be improved. 
     Hereinafter, a method of cleaning a substrate using a substrate cleaning system according to an exemplary embodiment will be described in detail with reference to  FIGS. 3 to 7 . 
       FIGS. 3 to 7  are diagrams sequentially illustrating a method of cleaning a substrate using a substrate cleaning system according to an exemplary embodiment. 
     First, as shown in  FIG. 3 , in a method of cleaning a substrate according to an exemplary embodiment, the first cleaning liquid  20  is ejected onto the substrate  10  that is loaded on the carrying unit  100  using the first rinse unit  200 . The first cleaning liquid  20  that is ejected from the first rinse unit  200  removes a contamination material on the silicon oxide film  12  that is formed on the substrate  10 . In this case, when an ejection angle of the first ejection portion  210  of the first rinse unit  200  is excessively small or excessively large, the first cleaning liquid  20  is intensively ejected in a narrow range or is widely ejected in a wide range and thus uniform cleaning may not be performed and therefore, in one embodiment, an ejection angle a 1  of the first ejection portion  210  is set within a range of about 30° to about 75° from a direction perpendicular to a traveling direction of the substrate  10 . 
     Next, as shown in  FIG. 4 , by rotating the roller shaft  111 , the carrying unit  100  moves the substrate  10  on the carrying unit  100  under the cleaning unit  300 . In this case, because the air knife  310  is located at a front of the cleaning unit  300  (i.e., it is encountered first by an object on the carrying unit  100 ), a residue of the first cleaning liquid  20  on the substrate  10  is removed using a high air pressure. 
     At the same time, the second cleaning liquid  30  is applied onto the silicon oxide film  12  of the substrate  10  using the slit nozzle  320  of the cleaning unit  300 . In this case, because a width t of the ejection opening  321  of the slit nozzle  320  is small (for example, about 0.1 mm to 2 mm), the second cleaning liquid  30  is ejected onto the substrate  10  in a uniform thickness. Because the second gap d 2  between the ejection opening  321  of the slit nozzle  320  and the silicon oxide film  12  of the substrate  10  is a small size of 1.5 mm to 5 mm, the second cleaning liquid  30  that is ejected from the slit nozzle  320  is applied in a substantially uniform thickness onto the silicon oxide film  12 . By constantly being applied to the moving substrate  10 , the second cleaning liquid  30  is applied in a substantially uniform thickness onto the silicon oxide film  12 . 
     Next, as shown in  FIG. 5 , the substrate  10  to which the second cleaning liquid  30  is applied is sustained in a horizontal state and a reaction process of the second cleaning liquid  30  is performed. The second cleaning liquid  30  that is applied in a substantially uniform thickness is deformed into the reaction material  31  that is separated from the silicon layer  11  by reacting with the silicon oxide film  12  under the second cleaning liquid  30 . In this case, a reaction time period in which a reaction process is performed may be about 5 seconds to 100 seconds. If a reaction time period is smaller than about 5 seconds, a time period in which the second cleaning liquid  30  reacts with the silicon oxide film  12  may be too short and thus it is difficult to completely remove the silicon oxide film  12 , and if a reaction time period is longer than about 100 seconds, a time to complete the entire process may be too long. 
     Further, the division roller  112  of a first roller  110  of the adjacent rollers  110  of the carrying unit  100  is alternately arranged with a second division roller  112 , and by adjusting the first gap d 1  between the adjacent roller shafts  111 , an area of a portion in which the division roller  112  and the substrate  10  do not contact is reduced and thus flatness of the substrate  10  is maximized, whereby etching uniformity of the silicon oxide film  12  can be improved. 
     Further, the rollers  110  are classified into a contact roller that contacts with the substrate  10  and a non-contact roller that does not contact with the substrate  10 , and a gap between the non-contact roller and the substrate  10  may be about 5 mm or less, and a gap between the non-contact roller and the contact roller may be between about 30 mm and about 100 mm. 
     Next, as shown in  FIG. 6 , a reaction material  31  of the second cleaning liquid  30  is removed from the substrate  10  with DI water of a high water pressure using the aqua knife  330 . 
     Next, as shown in  FIG. 7 , the third cleaning liquid  40  is ejected onto the substrate  10  in which the reaction material  31  of the second cleaning liquid  30  is removed using the second rinse unit  400 . The third cleaning liquid  40  can use ultrapure water or DI water, and the third cleaning liquid  40  that is ejected from the second rinse unit  400  removes a contamination material or a residue of the reaction material  31  on the silicon layer  11 . 
     In this case, in order for the third cleaning liquid  40  that is ejected from the second rinse unit  400  not to be injected into the cleaning unit  300 , an ejection angle a 2  of the second ejection portion  420  may be set at up to about 30° from a direction perpendicular to a traveling direction of the substrate  10 . 
     Accordingly, in a method of cleaning a substrate according to an exemplary embodiment, because the second cleaning liquid  30  is applied in a substantially uniform thickness only onto the silicon oxide film  12  using the slit nozzle  320 , a use amount of the second cleaning liquid  30  can be remarkably reduced to about 1/10 compared with a conventional spin cleaning method, spray method, or flow method. Further, while improving etching uniformity of the silicon oxide film  12 , the method can be applied to a large sized-substrate  10 . Further, because etching uniformity is improved, a crystallization stain and an element failure are prevented from occurring. 
     In a conventional spray method, because the substrate  10  is continuously carried, a length of the cleaning unit  300  is extended and thus much manufacturing space may be occupied, and in a conventional flow method, because a slope time period of the substrate  10  for flowing the second cleaning liquid  30  is necessary, a process time is relatively long. However, in a system and method for cleaning a substrate according to an exemplary embodiment, because the second cleaning liquid  30  is applied in a substantially uniform thickness only onto the silicon oxide film  12  using the slit nozzle  320  and the substrate  10  is stopped under the cleaning unit  300  during a reaction time period, a manufacturing space can be minimized compared with a conventional spray method, and a separate slope time period is unnecessary, compared with a conventional flow method and thus a process time can be minimized. 
     A system and method for cleaning a substrate according to an exemplary embodiment are applied to the substrate  10  of a flat panel display, as described above, and can be applied to the substrate  10  to be used to a liquid crystal display (LCD) and an organic light emitting diode (OLED) display. 
     While this disclosure has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. 
     &lt;Description of Symbols&gt; 
     
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                  10: substrate 
                  20: first cleaning liquid 
               
               
                   
                  30: second cleaning liquid 
                  40: third cleaning liquid 
               
               
                   
                 100: carrying unit 
                 200: first rinse unit 
               
               
                   
                 300: cleaning unit 
                 400: second rinse unit