Abstract:
A processing apparatus includes: a tank configured to store water; vapor generating unit configured to turn the water supplied from the tank into vapor; a processing chamber in which vapor supplied from the vapor generating unit is used to remove residues from a workpiece; cooling unit; and filtering unit. The cooling unit cools waste liquid ejected from the processing chamber. The filtering unit is provided between the cooling unit and the tank, and the filtering unit filters the waste liquid cooled in the cooling unit. A processing method includes: supplying vapor into a processing chamber; removing residues from a workpiece using the vapor; cooling waste liquid containing the removed residues to precipitate the residues as solids; and filtering the waste liquid containing the precipitates.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefits of priority from the prior Japanese Patent Application No. 2006-012758, filed on Jan. 20, 2006; the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a processing apparatus and a processing method, and more particularly to a processing apparatus and a processing method suitable to removing photoresist used in lithography. 
     2. Background Art 
     In a lithography step of a process of manufacturing a semiconductor device or a liquid crystal panel, for example, an organic resist film is typically used as a patterning mask. The resist film needs removing after the patterning is completed. Methods for removing a resist film include a method of heating and dissolving the resist film with an organic solvent or the like. However, use of an organic solvent involves additional costs in facilities for waste liquid disposal. In particular, recent upsizing of semiconductor wafers and liquid crystal panels increases the amount of waste liquid generated in the process of resist peeling. This causes a problem of the associated increase in disposal costs and environmental loads. 
     JP 2001-250773A, for example, discloses a technology of spraying water vapor of 70 to 200° C. onto a substrate to peel and remove a resist film. 
     However, in particular, low molecular weight ingredients in the organic resist are left dissolved in water at high temperatures. Therefore, even if waste liquid is passed through a filter to recover and reuse water from the waste liquid, the resist is not trapped by the filter and is passed through the filter together with water. As a result, unfortunately, the water contaminated with resist is used again as vapor for resist peeling. 
     SUMMARY OF THE INVENTION 
     According to an aspect of the invention, there is provided a processing apparatus comprising: a tank configured to store water; vapor generating unit configured to turn the water supplied from the tank into vapor; a processing chamber in which vapor supplied from the vapor generating unit is used to remove residues from a workpiece; cooling unit configured to cool waste liquid ejected from the processing chamber; and filtering unit provided between the cooling unit and the tank, the filtering unit being configured to filter the waste liquid cooled in the cooling unit. 
     According to another aspect of the invention, there is provided a processing method comprising: supplying vapor into a processing chamber; removing residues from a workpiece using the vapor; cooling waste liquid containing the removed residues to precipitate the residues as solids; and filtering the waste liquid containing the precipitates. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view illustrating the configuration of a processing apparatus according to an embodiment of the invention. 
         FIG. 2  is a schematic view illustrating the internal configuration of the processing chamber shown in  FIG. 1 . 
         FIG. 3  is a photographic image of a filter through which waste liquid has been passed, where a workpiece is processed with a high-temperature vapor and the waste liquid is passed through the filter at a high temperature (75° C.) without being cooled. 
         FIG. 4  is a photographic image of another similar filter through which the filtered waste liquid of 75° C. in  FIG. 3  cooled down to a liquid temperature of 30° C. has been passed again. 
         FIG. 5  is a photographic image of still another similar filter through which the filtered waste liquid of 30° C. in  FIG. 4  further cooled down to a liquid temperature of 25° C. has been passed again. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the invention will now be described with reference to the drawings, 
       FIG. 1  is a schematic view illustrating the configuration of a processing apparatus according to an embodiment of the invention. 
     The processing apparatus according to this embodiment primarily comprises a tank  39  for storing water, a vapor generator  26  for turning water in the tank  39  into vapor, a vapor reheater  27  for heating vapor generated in the vapor generator  26 , a processing chamber  1  in which the vapor supplied from the vapor reheater  27  is used to remove residues (matter to be removed) from a workpiece, a cooler  35  for cooling waste liquid ejected from the processing chamber  1 , and filters  38   a ,  38   b  provided along a piping between the cooler  35  and the tank  39  for filtering the waste liquid cooled in the cooler  35 . 
     The workpiece processed in the processing chamber  1  is, for example, a glass substrate for a liquid crystal panel. However, the workpiece is not limited thereto, but may be a substrate for a flat panel display, a semiconductor wafer, a lead frame, a printed wiring board, or the like. 
     Water such as ultrapure water or deionized water is stored in the tank  39 . The vapor generator  26  generates vapor of ultrapure water or deionized water. The vapor reheater  27  heats the vapor generated in the vapor generator  26  to a prescribed temperature. The heated vapor is supplied into the processing chamber  1 . 
       FIG. 2  is a schematic view illustrating the internal configuration of the processing chamber  1 . 
     In the processing chamber  1 , a plurality of transfer rollers  6  are provided along the moving direction A of the workpiece  10 . The transfer rollers  6  are rotatable while supporting the workpiece  10 . The workpiece  10  is moved in the moving direction A on the transfer rollers  6 . The workpiece  10  of up to 1.1 meters wide, for example, can be transferred by these transfer rollers  6 . The transfer rate can be varied from 1 to 10 meters/min, for example. 
     Above the moving path of the workpiece  10  on the transfer rollers  6  is disposed a nozzle  5 . The nozzle  5  has a discharge port opposed to the moving path of the workpiece  10 . The vapor generated in the vapor generator  26  and heated in the vapor reheater  27  is discharged toward the workpiece  10  through the discharge port of the nozzle  5 . 
     The flow rate of ultrapure water or deionized water introduced from the tank  39  into the vapor generator  26  for vapor generation is 4 to 10 liters/min, for example. The temperature of vapor discharged from the nozzle  5  can be controlled in the range of 100 to 140° C., for example. 
     Here, in light of temperature decrease due to adiabatic expansion that occurs when the water vapor is discharged into the atmosphere, the vapor generator  26  and the vapor reheater  27  are used to heat the water vapor to 180 to 300° C. so that the water vapor has a temperature of 100 to 140° C. on the surface of the processed substrate. 
     A water outlet  14  is formed at the bottom of the processing chamber  1 . A wastewater piping, not shown, is connected to the water outlet  14 . The wastewater piping is connected to the cooler  35  placed outside the processing chamber  1 . The cooler  35  is supplied with cooling fluid such as cooling water from a chiller  36 . The cooling fluid is circulated between the cooler  35  and the chiller  36 . The cooler  35  cools the waste liquid ejected from the processing chamber  1  through the water outlet  14 . 
     The cooler  35  is connected to a centrifuge  37 . The centrifuge  37  uses centrifugal force to separate ingredients with different masses contained in the waste liquid cooled by the cooler  35 . 
     The outlet piping of the centrifuge  37  is split into two pipings  45   a ,  45   b , to which filters  38   a ,  38   b  are connected, respectively. The filters  38   a ,  38   b  are hollow fiber membrane filters, for example, and filter the waste liquid from which heavier solids have been removed in the centrifuge  37 . 
     A valve  44   a  is provided between the inlet side of the filter  38   a  and the outlet side of the centrifuge  37 . The outlet side of the filter  38   a  is connected to the tank  39  through a valve  55   a.    
     Similarly, a valve  44   b  is provided between the inlet side of the filter  38   b  and the outlet side of the centrifuge  37 . The outlet side of the filter  38   b  is connected to the tank  39  through a valve  55   b.    
     That is, the two filters  38   a ,  38   b  are connected in parallel in the pipings between the centrifuge  37  and the tank  39 . 
     The inlet side of the filter  38   a  is connected to a tank  43  through a piping  46  and a valve  48 . Similarly, the inlet side of the filter  38   b  is connected to the tank  43  through a piping  47  and a valve  49 . The tank  43  is different from the above-described tank  39  for storing water for use in processing a workpiece and stores a processing liquid for removing solids trapped by the filters  38   a ,  38   b.    
     The outlet side of the filter  38   a  is connected to the discharge port of a hydraulic pump  42  through a piping  51  and a valve  53 . Similarly, the outlet side of the filter  38   b  is connected to the discharge port of the hydraulic pump  42  through a piping  52  and a valve  54 . The intake port of the hydraulic pump  42  is connected to the tank  43 . 
     The hydraulic pump  42 , the tank  43 , the pipings  46 ,  47 ,  51 ,  52 , and the valves  48 ,  49 ,  53 ,  54  constitute a filter cleaning mechanism for washing away and dissolving the solids trapped by the filters  38   a ,  38   b.    
     Each valve is an electromagnetic valve, which is switched by a signal from a controller (not shown). The opening and closing of the valves can be controlled to switch each of the filters  38   a ,  38   b  to one of the following states. In one state, the filters  38   a ,  38   b  are in communication with the centrifuge  37  and the tank  39  and blocked from the filter cleaning mechanism including the hydraulic pump  42  and the tank  43 . In the other state, the filters  38   a ,  38   b  are in communication with the filter cleaning mechanism and blocked from the centrifuge  37  and the tank  39 . 
     Next, the processing of the workpiece using the processing apparatus according to the embodiment of the invention is described. 
     A workpiece  10  is transferred into the processing chamber  1  and moved along a moving direction A in the processing chamber  1  by the rotation of the transfer rollers  6  shown in  FIG. 2 . At this time, water vapor generated in the vapor generator  26  and heated in the vapor reheater  27  is discharged toward the workpiece  10  from the nozzle  5 . The temperature and impact of this water vapor swells and peels the photoresist or other residues formed on the workpiece  10 . The peeled resist is flushed with water from the workpiece  10  to the bottom of the processing chamber  1  and ejected outside the processing chamber  1  through the water outlet  14 . This waste liquid is fed to the cooler  35 . 
     Here, a chemical for facilitating dissolution of the photoresist can also be added to the water vapor discharged from the nozzle  5 . In this case, water vapor, and water that has condensed from the water vapor after the processing, with photoresist ingredients being dissolved therein, remain on the processed portion of the workpiece. Such water vapor and water may be naturally cooled down and recoagulated on the substrate or other workpiece. 
     In this respect, in the processing apparatus (shown in  FIG. 2 ) described above, another nozzle is placed at a prescribed position such as a position immediately downstream of the nozzle  5 , and hot water sprayed from the other nozzle is supplied onto the substrate or other workpiece. Then water with photoresist ingredients being dissolved therein can be washed away from the substrate or other workpiece before the remaining photoresist ingredients dissolved in the water are recoagulated as described above. 
     The waste liquid fed from the cooler  35  is cooled by the cooling water supplied from the chiller  36 . By this cooling, the resist removed from the workpiece  10  and contained in the waste liquid is precipitated as solids. 
     The waste liquid cooled in the cooler  35 , which contains the resist precipitated as solids, is fed to the centrifuge  37 , where the solids are separated into a heavier and lighter fraction. The heavier fraction is recovered here and not fed to the filters  38   a ,  38   b  in the subsequent stage. Alternatively, instead of the centrifuge, a separator based on gravity settling may be used to separate the waste liquid ingredients into a heavier and lighter fraction. 
     The waste liquid from which the heavier component has been removed in the centrifuge  37  is fed to the filter  38   a ,  38   b . Both or either one of the filters  38   a ,  38   b  may be used. When both of the filters  38   a ,  38   b  are used, the valves  44   a ,  44   b ,  55   a ,  55   b  are opened. When only the filter  38   a  is used, the valves  44   a ,  55   a  are opened, and the valves  44   b ,  55   b  are closed. When only the filter  38   b  is used, the valves  44   b ,  55   b  are opened, and the valves  44   a ,  55   a  are closed. In any case, when the waste liquid is passed through the filters  38   a ,  38   b , the valves  48 ,  49 ,  53 ,  54  are closed. 
     When the waste liquid is passed through the filter  38   a ,  38   b , the lighter solids that were not recovered by the centrifuge  37  in the previous stage is trapped, and only the water that does not contain the resist removed from the workpiece  10  can be returned to the tank  39 . 
     The water returned to the tank  39  is vaporized again and discharged from the nozzle  5 , thereby being reused for removing resist from the workpiece  10 . Solids are completely removed from the waste liquid before returning to the tank  39  as described above. Therefore the piping from the tank  39  to the vapor generator  26 , the vapor reheater  27 , and the nozzle  5  is free from contamination due to solids. Thus the efficiency of generating vapor and processing the workpiece  10  by vapor can be improved. 
     A hundred pieces of glass substrates with a photoresist of novolac resin being applied thereon, for example, were processed as a workpiece by using only the cooler  35  without using the centrifuge  37  and the filters  38   a ,  38   b  described above. Then 3.28 grams of residual photoresist solids were observed in the waste liquid returned to the tank  39 . 
     When a similar processing was conducted using the centrifuge  37  in addition to the cooler  35 , the amount of residual solids in the waste liquid returned to the tank  39  was 0.11 gram. Thus it was found that the centrifuge  37  can remove 96 percent or more by weight of residual solids. 
     Furthermore, when a similar processing was conducted using a filter (either one of the filters  38   a  and  38   b ) in addition to the cooler  35  and the centrifuge  37 , the amount of solids in the waste liquid returned to the tank  39  was immeasurably small and scarcely observed. 
       FIG. 3  shows a photographic image of a filter through which waste liquid has been passed, where a glass substrate with a photoresist of novolac resin being applied thereon, for example, is processed with a high-temperature vapor and the waste liquid is passed through the filter at a high temperature (75° C.) without being cooled. 
     In this image, the presence of solids (resists) trapped by the filter is clearly observed. 
       FIG. 4  shows a photographic image of another similar filter (having the same mesh size) through which the filtered waste liquid of 75° C. in  FIG. 3  cooled down to a liquid temperature of 30° C. has been passed again. 
     Here again, although smaller in amount than previously, solids (resists) were trapped by the filter. That is, the resist ingredients dissolved in the high-temperature (75° C.) waste liquid were precipitated as solids by being cooled down to 30° C. 
       FIG. 5  shows a photographic image of still another similar filter (having the same mesh size) through which the filtered waste liquid of 30° C. in  FIG. 4  further cooled down to a liquid temperature of 25° C. has been passed again. 
     In this case, no solids (resists) trapped by the filter were detected. Consequently, when the waste liquid produced by high-temperature vapor processing is cooled down, the resist ingredients can be reliably precipitated as solids, which can be reliably trapped by the filter in the subsequent stage, so that the water with resist ingredients being dissolved therein is not directly returned to the tank  39 . 
     The solids trapped by the filters  38   a ,  38   b  can be removed by the filter cleaning mechanism. 
     For example, in the case of cleaning the filter  38   a , the hydraulic pump  42  is operated with the valves  44   a ,  55   a  being closed and the valves  48 ,  53  being opened. The cleaning liquid (e.g. water) in the filter cleaning tank  43  is passed through the filter  38   a  in the opposite direction to the direction during the waste liquid processing described above, that is, in the direction from the outlet side to the inlet side of the filter  38   a . Thus the solids trapped by the filter  38   a  can be removed from the filter  38   a . The solids removed from the filter  38   a  are recovered into the tank  43 . 
     At this time, the other filter  38   b  can be used for the normal processing of waste liquid by closing the valves  49 ,  54  and opening the valves  44   b ,  55   b . Thus there is no need to stop the normal processing of waste liquid for filter cleaning. 
     In the case of cleaning the other filter  38   b , the hydraulic pump  42  is operated with the valves  44   b ,  55   b  being closed and the valves  49 ,  54  being opened. The cleaning liquid in the filter cleaning tank  43  is passed through the filter  38   b  from the outlet side to the inlet side of the filter  38   b . At this time, the filter  38   a  can be used for the normal processing of waste liquid by closing the valves  48 ,  53  and opening the valves  44   a ,  55   a.    
     When about two thousand pieces of glass substrates with a photoresist of novolac resin being applied thereon, for example, were processed, there was an increased pressure loss due to the clogging of the filter with solids (resists). However, after the filter was backwashed with the cleaning liquid by the hydraulic pump  42 , the pressure loss was returned to the level before the beginning of processing the two thousand pieces of glass substrates. 
     The cleaning liquid is not limited to water, but may contain any solvent that can dissolve photoresist and the like. In this case, the cleaning liquid does not necessarily need to be passed through the filter in the opposite direction. 
     Embodiments of the invention have been described with reference to the examples. However, the invention is not limited thereto, but various modifications can be made within the spirit of the invention. 
     Residues to be removed by vapor are not limited to photoresists. Furthermore, the workpiece, specific processing conditions and the like are also not limited to those described above. 
     Filters can be parallel connected in three or more stages. Alternatively, a single filter configuration can also be used. Furthermore, filters with different mesh sizes can be series connected in multiple stages. Series connection of filters in multiple stages further ensures that resists and other solids can be trapped.