Abstract:
A washing/drying process apparatus comprises a spin chuck for holding a substrate such that a surface thereof to be processed faces upward and for rotating the substrate, a process fluid supply mechanism for selectively supplying one or two or more of a plurality of kinds of process fluids to the surface to be processed of the substrate rotated by the spin chuck, the process fluid supply mechanism having a first nozzle with a discharge port for discharging a process fluid which is in a liquid phase under conditions of room temperature and atmospheric pressure, and a second nozzle with a discharge port for discharging fluid which is in a gas phase under conditions of room temperature and atmospheric pressure, a driving mechanism for simultaneously moving the first and second nozzles to a location above the substrate held by the spin chuck, and a controller for controlling operations of the process liquid supply mechanism and the driving mechanism.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a washing/drying process apparatus and a washing/drying method for chemical-solution-washing, rinsing and drying a surface of a substrate such as a semiconductor wafer or a glass substrate for an LCD. 
     In a process of fabricating a semiconductor device, a washing/drying process apparatus is used in order to remove a contamination such as particles, organic substances or metal ions from the surface of the substrate. An example of the apparatus for washing and drying a semiconductor wafer is a single-wafer-type washing/drying process apparatus for processing wafers one by one within a cup. In the single-wafer-type washing/drying process apparatus, a wafer is rotated, while being held by a spin chuck, and a chemical solution is applied to the surface of the spinning wafer for chemical solution washing. Then, pure water is applied to the washed surface to rinse it. Finally, a dry N 2  gas is applied to dry the wafer surface. 
     In the conventional apparatus, a chemical solution nozzle, a rinse nozzle and a dry nozzle are provided around the cup. These nozzles are moved between the home position and use position by different drive mechanisms. In this conventional apparatus, a considerable time is needed for switching from the chemical solution nozzle to the rinse nozzle and from the rinse nozzle to the dry gas nozzle. Consequently, so-called a water mark occurs when liquid drops adhering to the surface of the wafer dry naturally. The water mark is a compound of H 2 SiO 3  produced by reaction between oxygen and H2O in the atmosphere and silicon or by precipitation of a very small amount of SiO 2  included in rinse liquid (pure water) on the surface of the silicon wafer. Such a water mark may remain on the wafer surface even after the dry process. 
     In addition, in the conventional apparatus, when a chemical solution is applied to the rotating wafer, liquid drops separated centrifugally from the wafer adhere to the inner wall of the cup. Repetition of chemical solution wash processes results in adhesion of a great amount of liquid drops on the inner wall of the cup. This may adversely affect the subsequent rinse process. If the chemical solution drops have dried on the inner wall of the cup and their constituent has precipitated, particles of the constituent may occur and contaminate the wafer. 
     In the conventional apparatus, after the chemical solution wash process, the waste liquid is recovered from the cup and it is reused after regeneration. In the conventional apparatus, a recovery/regeneration apparatus for recovering and regenerating the waste liquid is disposed as a unit separated from the chemical solution wash apparatus and at a separate location. As a result, the conventional apparatus occupies a large area within the clean room. In addition, the length of the waste liquid recovery circuit (recovery piping) and the regenerated chemical solution return circuit (return piping) increases considerably. Thus, such problems will arise as an increase in capacity of a chemical solution supply pump and a variation in temperature of chemical solution. 
     In the conventional apparatus, in a case where the bottom surface of the wafer is hydrophobic, a process liquid, which has been applied to the bottom surface of the wafer from a bottom-side nozzle, will naturally drop from the bottom surface of the wafer before spreading over the entire bottom surface. In the conventional process apparatus, therefore, the area on the bottom surface of the wafer, which can be effectively washed, is limited. 
     Furthermore, the bottom surface of the wafer is not uniformly covered with the liquid, and after the process liquid has naturally dropped from the bottom surface of the wafer, the bottom surface of the wafer comes in contact with outside air in the state in which it is wet to some degree. As a result, a great number of gas-liquid interfaces occur on the bottom surface of the wafer and particles will easily occur at the gas-liquid interfaces. Consequently, particles adhere to the bottom surface of the wafer while the wash process is being performed, and the efficiency of the wash process considerably deteriorates. 
     BRIEF SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a small-sized, simple-structured washing/drying process apparatus and a washing/drying process method capable of washing, rinsing and drying a surface of a substrate with a high through-put without producing a water mark. 
     Another object of the invention is to provide a washing/drying process apparatus and a washing/drying process method capable of immediately washing away a chemical solution, etc. on an inner wall of a cup and decreasing the length of a waste liquid recovery circuit and a return circuit. 
     Still another object of the invention is to provide a washing/drying process apparatus and a washing/drying process method capable of uniformly processing a lower surface of a substrate. 
     A washing/drying process apparatus according to the invention comprises: a spin chuck for holding a substrate such that a surface thereof to be processed faces upward and for rotating the substrate; a process fluid supply mechanism for selectively supplying one or two or more of a plurality of kinds of process fluids to the surface to be processed of the substrate rotated by the spin chuck, the process fluid supply mechanism having a first nozzle with a discharge port for discharging a process fluid which is in a liquid phase under conditions of room temperature and atmospheric pressure, and a second nozzle with a discharge port for discharging fluid which is in a gas phase under conditions of room temperature and atmospheric pressure; a driving mechanism for simultaneously moving the first and second nozzles to a location above the substrate held by the spin chuck; and a controller for controlling operations of the process liquid supply mechanism and the driving mechanism. 
     It is preferable that the washing/drying process apparatus further comprises a nozzle assembly in which the first and second nozzles are integrated, the discharge port of the first nozzle and the discharge port of the second nozzle being adjacent to each other in the nozzle assembly. It is also preferable that the discharge port of the first nozzle and the discharge port of the second nozzle are arranged concentrical at a lower part of the nozzle assembly. It is preferable that the discharge port of the first nozzle and the discharge port of the second nozzle are arranged symmetrical at a lower part of the nozzle assembly. It is preferable that the first nozzle has a first discharge port for discharging a chemical solution for chemical washing and a second discharge port for discharging pure water for rinsing, and the second nozzle has a third discharge port for discharging isopropyl alcohol vapor for drying and a fourth discharge port for discharging a dry inert gas for drying. Thereby, the dry gas can be applied from the second nozzle immediately after the chemical solution and rinse liquid have been discharged to the substrate from the first nozzle. Thus, the wash/rinse process and the dry process can be successively performed, and no water mark is produced. 
     A washing/drying process apparatus according to the invention comprises: a cup having at an upper part thereof an opening for loading and unloading a substrate; a spin chuck for holding and rotating the substrate within the cup; a process fluid supply mechanism having a plurality of nozzles for discharging and supplying a process fluid to the substrate held by the spin chuck; and a relative elevation mechanism for relatively and vertically moving at least one of the cup and the spin chuck, thereby varying a positional relationship between the substrate on the spin chuck and the cup. 
     The cup has an over-hang portion projecting inward so as to surround the opening and receiving the process fluid dispersed from the rotating substrate. The rinse liquid as second process fluid is indirectly applied to the over-hang portion, and dry N 2  gas as second process fluid is indirectly applied to the over-hand portion. Therefore, the inner wall of the cup is always kept in a clean state. 
     It is preferable that the washing/drying process apparatus further comprises: a recovery circuit communicating with a lower part of the cup; a recovery/regeneration tank communicating via the recovery circuit with the cup below the cup, for recovering and regenerating the process fluid exhausted from the cup; and a return circuit for returning the regenerated process fluid from the recovery/regeneration tank to the process fluid supply mechanism. It is preferable that the recovery circuit, recovery/regeneration tank, return circuit, cup, spin chuck, and process fluid supply mechanism are arranged within a single unit. Thereby, the length of the recovery circuit and return circuit is decreased, and a temperature variation in chemical solution is prevented. 
     It is preferable that the spin chuck has a conical reservoir with a diameter decreasing from a periphery thereof toward a center thereof, the reservoir facing a lower surface of the held substrate, and the apparatus further comprises a third nozzle opening at a lowermost part of the reservoir, the third nozzle supplying a rinse liquid to the reservoir and applying the rinse liquid to the lower surface of the held substrate. 
     A method of the invention for chemically washing, rinsing and drying a surface of a substrate in a single apparatus, comprises the steps of: (a) holding the substrate and starting spin-rotation of the substrate; (b) supplying a chemical solution to the rotating substrate and subjecting the surface of the substrate to a chemical washing process; (c) supplying a rinse solution to the rotating substrate and subjecting the surface of the substrate to a rinse process; (d) supplying a first dry gas to the rotating substrate and subjecting the surface of the substrate to a dry process; (e) supplying a second dry gas to the rotating substrate and subjecting the surface of the substrate to a final dry process; and (f) stopping the spin-rotation of the substrate and releasing the holding of the substrate. 
     It is preferable that in the steps (d) and (e), the first dry gas along with the second dry gas is supplied to the surface of the substrate. In this case, it is preferable that the first dry gas contains vapor of isopropyl alcohol, and the second dry gas is an inert gas temperature-controlled at a point higher than a boiling point of isopropyl alcohol. The inert gas is, for example, nitrogen gas, argon gas, or helium gas. 
     It is preferable that in the steps (b) to (e), pure water is supplied to a lower surface of the substrate, thereby preventing particles from adhering to the lower surface of the substrate. 
     A washing/drying process method of the invention for chemical-washing, rinsing and drying a surface of a substrate in an apparatus comprising a cup having at an upper part thereof an opening for loading/unloading the substrate, a spin chuck for holding and rotating the substrate, a relative elevation means for relatively and vertically moving the spin chuck and the cup, and a process fluid supply mechanism with a nozzle for selectively discharging and supplying one or two or more of a plurality of kinds of process liquids to the substrate, comprises: (A) relatively and vertically moving the cup and the spin chuck by the relative elevation means, setting the opening of the cup at a position lower than the pin chuck, and loading the substrate on the spin chuck; (B) relatively and vertically moving the cup and the spin chuck by the relative elevation means, setting the substrate at a first relative height position relative to the cup, and discharging a liquid-phase first process fluid from the nozzle to the substrate, thereby subjecting the surface of the substrate to a chemical washing process; (C) relatively and vertically moving the cup and the spin chuck by the relative elevation means, setting the substrate at a second relative height position relative to the cup, and discharging a liquid-phase second process fluid from the nozzle to the substrate, thereby subjecting the surface of the substrate to a rinsing process; (D) relatively and vertically moving the cup and the spin chuck by the relative elevation means, setting the substrate at the first relative height position relative to the cup, and discharging a gas-phase first process fluid from the nozzle to the substrate, thereby subjecting the surface of the substrate to a dry process; (E) relatively and vertically moving the cup and the spin chuck by the relative elevation means, setting the substrate at the second relative height position relative to the cup, and discharging a gas-phase second process fluid from the nozzle to the substrate, thereby subjecting the surface of the substrate to a final dry process; and (F) relatively and vertically moving the cup and the spin chuck by the relative elevation means, setting the opening of the cup at a position lower than the spin chuck, and unloading the substrate from the spin chuck. 
     It is preferable that in the step (C) or (E) the liquid-phase second process fluid is supplied to the substrate before setting the substrate at the second relative height position. In addition, it is preferable that in the step (D) the gas-phase second process fluid along with the gas-phase first process fluid is supplied to the substrate. It is preferable that in the step (B) the liquid-phase first process fluid is recovered, regenerated, returned to the process fluid supply mechanism, and resupplied to the substrate from the nozzle. It is preferable that in the step (D) the gas-phase first process fluid is recovered, regenerated, returned to the process fluid supply mechanism, and resupplied to the substrate from the nozzle. In addition, it is preferable that the gas-phase first process fluid contains vapor of isopropyl alcohol, and the gas-phase second dry process fluid is an inert gas temperature-controlled at a point higher than a boiling point of isopropyl alcohol. 
     Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinbefore. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiments of the invention, and together with the general description given above and the detailed description of the preferred embodiments given below, serve to explain the principles of the invention. 
     FIG. 1 is a plan view showing a washing/drying system for washing a surface of a semiconductor wafer with a chemical solution, rising the surface and drying the surface; 
     FIG. 2 is a cross-sectional block diagram showing a washing/drying process apparatus according to an embodiment of the present invention; 
     FIG. 3 is a plan view showing the washing/drying process apparatus according to the embodiment; 
     FIG. 4 is a circuit diagram showing a circuit for supplying and recovering a washing chemical solution; 
     FIG. 5 is a perspective block diagram showing a collective nozzle block (nozzle assembly); 
     FIG. 6 is a partially enlarged plan view showing a liquid discharge portion of the collective nozzle block (nozzle assembly); 
     FIG. 7 is a partially enlarged plan view showing a modification of the liquid discharge portion of the collective nozzle block (nozzle assembly); 
     FIG. 8 is a partially enlarged plan view showing a modification of the liquid discharge portion of the collective nozzle block (nozzle assembly); 
     FIG. 9 is a perspective block diagram showing another collective nozzle block (nozzle assembly); 
     FIG. 10 is a perspective block diagram showing another collective nozzle block (nozzle assembly); 
     FIG. 11 is a partially enlarged plan view showing a liquid discharge portion of the collective nozzle block (nozzle assembly) shown in FIG. 10; 
     FIG. 12 is a flow chart illustrating a washing/drying method according to an embodiment of the invention; 
     FIG. 13 is a cross-sectional block diagram showing a washing/drying process apparatus according to another embodiment of the invention; 
     FIG. 14 is a flow chart illustrating a washing/drying method according to another embodiment of the invention; 
     FIGS. 15A to  15 D are see-through cross-sectional views showing various states of the washing/drying apparatus in order to describe the method illustrated in FIG. 14; 
     FIG. 16 is a see-through cross-sectional view showing a bottom-surface process apparatus for processing a bottom surface of a substrate; and 
     FIG. 17 is a plan view showing the upper side of the bottom-surface process apparatus. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. 
     A washing/drying system  1 , as shown in FIG. 1, comprises a cassette mount section  2 , a sub-arm mechanism  3 , a process section  4  and a main arm mechanism  5 . Four cassettes C each storing  25  wafers W are arranged on the cassette mount section  2 . The sub-arm mechanism  3  takes out non-washed wafers W from the cassettes C and transfers them onto the main arm mechanism  5 , or receives washed wafers W from the main arm mechanism  5  and restores them into the cassettes C. 
     The process section  4  is provided with a Y-axis transfer path  6  for movement of the main arm mechanism  5 . Process units  7  ( 7 A,  7 B),  8  and  9  are successively provided on both sides of the Y-axis transfer path  6 . Specifically, each pair of process units  7  ( 7 A,  7 B),  8  and  9  are opposed to each other, with the transfer path  6  interposed. 
     The main arm mechanism  5  comprises a wafer holder, an advancing mechanism for advancing the wafer holder, a Y-axis drive mechanism for driving the wafer holder in the Y-axis direction, a Z-axis drive mechanism for driving the wafer holder in the Z-axis direction, and a θ rotary drive mechanism for rotating the wafer holder about the Z-axis. 
     At first, the wafer W is washed with a chemical solution in the first process unit  7 , rinsed and dried. Then the wafer W is washed with another chemical solution in the second process unit  8 , rinsed and dried. At last the wafer W is rinsed with pure water in the third process unit  9  and dried. 
     The process unit  7 ,  8 ,  9  will now be described. Since the process units  7 ,  8  and  9  have substantially the same construction, the first process unit  7  will be described representatively. 
     The process unit  7  has a casing  7   a , as shown in FIG. 2. A spin chuck  10 , a cup  20  and a process fluid supply mechanism  30  are provided within the casing  7   a . The spin chuck  10  has a motor  11 , a table  13  and a wafer holder  14 . The motor  11  is disposed below the casing  7   a , and its rotary drive shaft  12  is coupled to the lower surface of the table  13 . The wafer holder  14  is erected on a peripheral portion of the table  13  and is put in contact with an outer peripheral portion of the wafer W. The wafer W is thus held in the state in which the wafer W is floated above the table  13 . A part of the wafer holder  14  is cut out to permit transfer of the wafer W, as shown in FIG.  3 . 
     The cup  20  comprises a cylindrical portion  20   a , a bottom portion  20   b , an inner guide portion  20   c , a discharge port  20   d , an upper opening  20   e  and an over-hang portion  20   f . A space for downward flow of waste liquid is defined between the cylindrical portion  20   a  and inner guide portion  20   c . A plurality of exhaust ports are formed in the bottom portion  20   b  and communicate with exhaust pipes  21 . The over-hang portion  20   f  is continuous with an upper portion of the cylindrical portion  20   a . The upper opening  20   e  is surrounded by the over-hang portion  20   f . The angle θ between the over-hang portion  20   f  and cylindrical portion  20   a  is set in a range of from 110° to 135°. 
     An atmospheric gas within the cup  20  is exhausted by a vacuum pump (not shown) having a suction port communicating with the bottom of the cup  20 . A process liquid separated centrifugally from the wafer W is exhausted to a drain unit  61  via the exhaust pipes  21  opening to the bottom of the cup  20 . 
     Referring to FIG. 4, recovery and regeneration of waste liquid in the drain unit  61  will now be described. 
     The drain unit  61  is provided within the single unit casing  7   a  along with the spin chuck  10 , cup  20  and process liquid supply mechanism  30 . The drain unit  61  comprises a recovery circuit  70 , a tank  71 , a gas-liquid separator  72 , a circulation circuit  80  and a return circuit  33 . 
     A chemical solution, pure water, IPA (isopropyl alcohol) vapor and N 2  gas are all exhausted from the cup  20  through the discharge pipes  21  to the drain unit  61 . The recovery circuit  70  communicates with the discharge pipes  21 , and the outlet of the recovery circuit  70  communicates with the tank  71  disposed below the cup  20 . The gas-liquid separator  72  and drain circuit  73  are arranged successively in this order from above between the recovery circuit  70  and tank  71 . The drain circuit  73  communicates with the recovery circuit  70  via an opening/closing valve  74 . 
     The gas-liquid separator  72  separates the process fluid coming in from the discharge pipes  21  via the recovery circuit  70  into process liquids, such as chemical solution and pure water, and process gases such as IPA vapor and N 2  gas. The gas-liquid separator  72  also eliminates bubbles from the chemical solution. Specifically, the process liquids such as IPA vapor and N 2  gas, which are included in the process fluid coming into the gas-liquid separator  72 , are exhausted from an exhaust port  75  provided at an upper portion of the gas-liquid separator  72 , and the process liquids such as chemical solution and pure water are let to flow along an inclined table  76  set in the separator  52 . While the process liquids are flowing, gas components are exhausted from the exhaust port  75  and liquid components are supplied once again into the recovery circuit  70  from an exhaust liquid port  77  provided at a bottom portion of the gas-liquid separator  72 . 
     The three-way valve  74  is operated to exhaust the pure water of process liquids separated by the gas-liquid separator, which has been used in the rinse process, to the drain circuit  73  from the recovery circuit  70 . The chemical solution of process liquids is received in the tank  71 . Since the tank  71  is provided below the cup  20 , the length of the recovery circuit  70  can be decreased and the used chemical solution can be quickly recovered into the tank  71  by natural drop. 
     The circulation circuit  80  for conditioning the chemical solution stored in the tank  71  is connected to the tank  71 . The return circuit  33  is connected midway along the circulation circuit  80  via a three-way valve  81 . The outlet of the return circuit  33  is connected to the process liquid supply mechanism  30 . The chemical solution from the tank  71 , which has been conditioned by the circulation circuit  80 , is returned to the nozzle of the supply mechanism  30 . 
     The inlet of the circulation circuit  80  is connected to the bottom surface of the tank  71 . A pump  83 , a damper  84 , a heater  85  and a filter  86  are successively arranged midway along the circulation circuit  80 . The outlet of the circulation circuit  80  is connected to the upper part of the tank  70 . The three-way valve  81  may be switched to prevent the chemical solution from flowing to the return circuit  33  and to permit the chemical solution recovered from the recovery circuit  70  into the tank  71  to flow to the circulation circuit  80 . The chemical solution coming in the circulation circuit  80  is let to flow successively through the damper  84 , heater  85  and filter  86  by the operation of the pump  83 . Thus, the chemical solution is temperature-conditioned and purified and then returned to the tank  71 . 
     The regenerated chemical solution in the tank  71  is let to flow to the return circuit  33  by switching the three-way valve  81 . The chemical solution returned to the nozzle of supply mechanism  30  through the return circuit  33  is reused for the washing process of the wafer W. 
     The process fluid supply mechanism  30  and nozzle assembly  31  will now be described with reference to FIGS. 2,  3  and  5 - 11 . 
     The process fluid supply mechanism  30  comprises a nozzle assembly  31 , a chemical solution supply unit  62 , a pure water supply unit  64 , an N 2  gas supply unit  66 , an IPA vapor generator  68 , and a controller  60 . The nozzle assembly  31  is attached to a distal end portion of a horizontal arm  32 . As is shown in FIG. 3, the nozzle assembly  31  is swung about a vertical shaft  50  by means of a drive mechanism  51  between a home position (outside the cup  20 ) and a use position (inside the cup  20 ). The respective supply units  62 ,  64 ,  66  and  68  communicate with the nozzle assembly  31  via line tubes  33 ,  34 ,  35  and  37 . The line tubes  33 ,  34 ,  35  and  37  are made of fluororesin or stainless steel and are flexible. Flow rate control valves (not shown) of the supply units  62 ,  64 ,  66  and  68  are controlled by the controller  60 . 
     As is shown in FIG. 5, the main body of the nozzle assembly  31  has a rectangular shape. The horizontal arm  32  is coupled to one side surface of the assembly  31 . The line tubes  33  and  34  are connected to other mutually opposed side surfaces of the assembly  31 . The line tube  35  is connected to the top surface of the assembly  31 . A collective nozzle member  43  is attached to the bottom surface of the assembly  31 . The respective line tubes  33 ,  34  and  35  are connected to discharge ports  40 ,  41  and  42  of the collective nozzle member  43  via internal passages (not shown). The first to third discharge ports  40 ,  41  and  42  may be arranged symmetrical, as shown in FIGS. 6 and 7, or may be arranged concentric, as shown in FIG.  8 . 
     The first discharge port  40  communicates with the line tube  33 , and the line tube  33  communicates with the chemical solution supply unit  62 . The second discharge port  41  communicates with the line tube  34 , and the line tube  34  communicates with the pure water supply unit  64 . The third discharge port  42  communicates with the line tube  35 , and the line tube  35  communicates with the IPA vapor generator  68  via a three-way valve  36 . 
     As is shown in FIG. 5, the IPA vapor generator  68  comprises a tank  68   a , an N 2  gas source  68   b  and a take-in pipe  68   c . If N 2  gas is introduced into IPA liquid in the tank  68   a  via the take-in pipe  68   c  from the N 2  gas source  68   b , IPA vapor is generated by gas bubbling. The IPA vapor (first dry gas) is discharged from the third discharge port  42  of collective nozzle member  43  through the line tube  35 . One passage of the three-way valve  36  communicates with the line tube  37 . Dry N 2  gas (second dry gas) is introduced from another N 2  gas source  66  via the line tube  37 , and the IPA vapor is mixed with the dry N 2  gas in the line tube  35 . Instead of using the mixture of the IPA vapor and dry N 2  gas, it is possible to use the IPA vapor alone as dry gas. 
     As is shown in FIG. 3, the nozzle assembly  31  is reciprocally moved in a horizontal plane between the home position and use position by the swing mechanism  50 ,  51 . By moving the nozzle assembly  31  only once, it is possible to perform a series of processes for chemical-washing, rinsing and drying the wafer W. A receiving cup (not shown) may be provided at the home position of the nozzle assembly  31  so that the discharge ports  40 ,  41  and  42  of the collective nozzle member  43  in the wait position may be received in the cup and cleaned. 
     FIG. 9 shows a nozzle assembly  31 A according to another embodiment of the invention. The nozzle assembly  31 A comprises three separate nozzles  33   a ,  34   a  and  35   a . The nozzles  33   a ,  34   a  and  35   a  are linearly arranged on the lower surface of the nozzle assembly  31 A. The discharge port of the first nozzle  33   a  communicates with the line tube  33 , the discharge port of the second nozzle  34   a  communicates with the line tube  34 , and the discharge port of the third nozzle  35   a  communicates with the line tube  35 . 
     FIGS. 10 and 11 show a nozzle assembly  31 B according to still another embodiment of the invention. A collective nozzle member  43 A of nozzle assembly  31 B has four discharge ports  40 ,  41 ,  42  and  44 . Although the first, second and third discharge ports  40 ,  41  and  42  are substantially the same as those in the embodiment shown in FIG. 5, the fourth discharge port  44  is newly added. The added fourth discharge port  44  communicates with the N 2  gas supply unit  66  via the line tube  39  and discharges only dry N 2  gas. 
     With reference to FIG. 12, a description will now be given of the case of washing the surface of the semiconductor wafer W twice by using two kinds of chemical solutions. 
     The cassette C is placed on the mount section  2  by means of a transfer robot (not shown). The cassette C contains  25  prewashed, non-processed semiconductor wafers W. The sub-arm mechanism  3  takes out one of the wafers W from the cassette C, and transfers this wafer W to the main arm mechanism  5 . The main arm mechanism  5  carries the wafer W into the first process unit  7  and places it on the table  13  of spin chuck  10  (step S 1 ). The spin chuck  10 , cup  20  and nozzle assembly  31  are relatively moved, and the cup  20  and nozzle assembly  31  are positioned relative to the wafer W (step S 2 ). 
     The spin chuck  10  is rotated at low speed, and a chemical solution is supplied to the line tube  33  of the nozzle assembly  31 . The chemical solution is discharged from the discharge port  40  onto the wafer W, and applied to the upper surface of the wafer W (step S 3 ). In the first washing process, a mixture solution of ammonia solution and hydrogen peroxide solution for example, is used as the chemical solution, thereby eliminating contaminants such as organic substance or particles from the surface of the wafer W. 
     The valve of the line tube  33  is closed, and the valve of the line tube  34  is opened. Pure water is supplied to the nozzle assembly  31 , and pure water is discharged from the discharge port  41  onto the wafer W. The chemical-washed surface of the wafer W is thus rinsed (step S 4 ). The valve of the line tube  34  is closed to stop the supply of pure water. The wafer W is then rotated at high speed, and water is separated and removed from the wafer W by centrifugal force. 
     The three-way valve  36  of line tubes  35  and  37  is opened, and a mixture gas (first dry gas) of IPA vapor and N 2  gas is supplied to the nozzle assembly  31 . The firs dry gas is applied from the discharge port  42  to the wafer W, thus drying the wafer W (step S 5 ). The drying step for the wafer W may be finished in this step S 5  alone. It is preferable, however, to apply dry N 2  gas (second dry gas) to the wafer W in the next step S 6 . Since IPA vapor contains particles of carbon, etc., the particles remaining on the surface of the wafer W are removed by the additional drying step using only N 2  gas, following the drying step using the mixture gas of IPA vapor and N 2  gas. In this case, if the N 2  gas is preheated, even if IPA component remains on the surface of the wafer W, the remaining IPA component can be evaporated and removed by the heat of the N 2  gas. It is preferable that the N 2  gas in this case be preheated at a temperature higher than the boiling point of IPA vapor. 
     If the primary drying step using IPA vapor and the secondary drying step using dry N 2  gas (final drying) are combined, the surface of the wafer W can be completely dried. In the above steps S 3  to S 6 , the nozzle assembly  31  stays at a fixed position above the wafer W. 
     The main arm mechanism  5  carries out the wafer W from the first process unit  7  (step S 7 ) and then carries it into the second process unit  8  (step S 8 ). The nozzle assembly  31 , spin chuck  10 , and cup  20  are relatively moved, and the nozzle assembly  31  is positioned relative to the wafer W on the table  13  (step S 9 ). 
     The spin chuck  10  is rotated at a predetermined speed, and a chemical solution is supplied to the line tube  33  of the nozzle assembly  31 . The chemical solution is discharged from the discharge port  40  onto the wafer W, and applied to the upper surface of the wafer W (step S 10 ). In the second washing process, hydrofluoric acid solution is used as the chemical solution. 
     Pure water is supplied to the line tube  34  of nozzle assembly  31 , and pure water is discharged from the discharge port  41 . The chemical-washed surface of the wafer W is thus rinsed (step S 11 ). Following the rinsing step S 11 , the wafer W is rotated at high speed, and liquid is separated and removed from the wafer W by centrifugal force. 
     The three-way valve  36  of line tubes  35  and  37  is opened, and a mixture gas (first dry gas) of IPA vapor and N 2  gas is supplied to the nozzle assembly  31 . The firs dry gas is applied from the discharge port  42  to the wafer W, thus drying the wafer W (step S 12 ). The drying step for the wafer W may be finished in this step S 5  alone. It is preferable, however, to apply dry N 2  gas to the wafer W in the next step S 6 . Specifically, N 2  gas is supplied to the line tube  39  of nozzle assembly  31 , and the N 2  gas is applied from the discharge port  44  to the washed surface of the wafer W, thereby finally drying the washed surface (step S 13 ). If the primary drying step using IPA vapor and the secondary drying step using dry N 2  gas (final drying) are combined, the surface of the wafer W can be completely dried. Thus, impure substances such as organic contaminants and particles on the surface of the wafer W can be removed. 
     The main arm mechanism  5  carries out the wafer W from the second process unit  8  (step S 14 ) and then stores the processed wafer W in the cassette C of cassette station  2  (step S 15 ). If the cassette C is filled with processed wafers W, the cassette C along with wafers W is carried to the outside. It is possible to finally wash the wafer W in the process unit  9  using a third chemical solution and then dry it. 
     According to this embodiment, the three processes of chemical solution washing, rinsing and drying can carried out by the single nozzle assembly. Thus, the step of chemical solution washing and rinsing can be quickly switched to the drying step, and occurrence of so-called water marks (stains due to local oxidation reaction between liquid drops and atmosphere on the wafer surface) can be prevented, and the through-put increased. 
     In addition, since the final drying step using N 2  gas along is added to the primary drying step using the mixture gas of IPA vapor and N 2  gas, it is possible to prevent contamination such as carbon from remaining on the surface of the wafer W. 
     According to the above embodiment, the chemical solution/rinsing process through the drying process can be successively performed, and no water mark is produced. In the conventional apparatus much time is needed for the switching from the nozzle for chemical solution/rinsing process to the drying process. By contrast, in the present embodiment, the operation for switching of the nozzle is not required, and the through-put is greatly increased. 
     A second embodiment of the present invention will now be described with reference to FIGS. 13,  14  and  15 A to  15 D. A description of the parts common to those of the first embodiment is omitted. 
     The washing/drying process apparatus of the second embodiment is provided as process unit  7 A in the washing process system  1  shown in FIG.  1 . As is shown in FIG. 13, the washing/drying process apparatus  7 A comprises various process fluid supply mechanisms  130  and  131  and drive mechanisms  23 ,  148  and  149 . The process apparatus  7 A is surrounded by housing panels and formed as unit  7   a . A casing  7   b  is provided within the unit  7   a , A spin chuck  10  and a cup  20  are provided within the casing  7   b . The spin chuck  10  and cup  20  are the same as described above. 
     The first process fluid supply mechanism  130  functions to supply a chemical solution as a first process fluid and pure water as a second process fluid to the wafer W. The supply mechanism  130  comprises a first nozzle  128 , a nozzle support member  132 , a chemical solution supply source  102 , pure water supply source  104 , a horizontal arm  138 , a swing mechanism (not shown), and an elevation mechanism  148 . The swing mechanism (not shown) functions to swing the horizontal arm  138  in a horizontal plane. The swing mechanism  138  is substantially the same as the mechanism  50 ,  51  shown in FIG.  2 . The elevation mechanism  148  comprises an air cylinder whose air supply source (not shown) is controlled by a controller  160 . The elevation mechanism  148  elevates the horizontal arm  138 . The nozzle support member  132  is provided at a free end portion of the horizontal arm  138 . The first nozzle  128  is attached to a lower part of the nozzle support portion  132 . 
     The chemical solution supply source  102  communicates with a line tube  135  via a valve  134  and comprises a plurality of tanks, a mass flow meter, a mixer, and a temperature control mechanism (all not shown). The chemical solution supply source  102  supplies a chemical solution as a first process fluid. The chemical solution supply source  102  mixes, for example, ammonia solution and hydrogen peroxide solution at a predetermined ratio, controls the temperature of the mixture solution of ammonia and hydrogen peroxide, and supplies the mixture solution to the first nozzle  128 . The first process fluid may be, for example, hydrofluoric acid solution. 
     The rinse liquid supply source  104  communicates with a line tube  137  via a valve  136 , and comprises a tank, a mass flow meter and a temperature control mechanism (all not shown). The rinse liquid supply source  104  supplies a rinse liquid as a second process fluid. The supply source  104  controls the temperature of, for example, pure water and supplies it to the first nozzle  128 . The line tubes  135  and  137  communicate with a common line tube  33 . The common line tube  33  communicates with the first nozzle  128  via an internal passage in the nozzle support member  132 . The common line tube  33  communicates with the circulation circuit  80 . A chemical solution regenerated by the circulation circuit  80  and recovery tank  71  is fed to the common pipe  33 . 
     The second process fluid supply mechanism  131  functions to supply IPA vapor as a first process fluid and dry nitride gas as a second process fluid to the wafer W. The supply mechanism  131  comprises a second nozzle  129 , a nozzle support member  140 , an IPA vapor supply source  106 , a dry nitride gas supply source  108 , a horizontal arm  145 , a swing mechanism (not shown), and an elevation mechanism  149 . The swing mechanism (not shown) functions to swing the horizontal arm  145  in a horizontal plane and is substantially the same as the mechanism  50 ,  51  shown in FIG.  2 . The elevation mechanism  149  comprises an air cylinder whose air supply source (not shown) is controlled by the controller  160 . The elevation mechanism  149  elevates the horizontal arm  145 . The nozzle support member  140  is provided at a free end portion of the horizontal arm  145 . The second nozzle  129  is attached to a lower part of the nozzle support portion  140 . 
     The IPA vapor supply source  106  communicates with a line tube  142  via a valve  141 , and comprises a plurality of tanks, a mass flow meter, a mixer, and a temperature control mechanism (all not shown). The IPA vapor supply source  106  mixes, for example, IPA vapor and dry nitrogen gas at a predetermined ratio, controls the temperature and humidity of the mixture gas, and supplies the mixture gas to the second nozzle  129 . It should be noted that IPA vapor alone may be supplied to the second nozzle  129 . 
     The dry nitrogen gas supply source  108  communicates with a line tube  144  via a valve  143  and comprises a tank, a mass flow meter and a temperature/humidity control mechanism (all not shown). The dry nitrogen gas supply source  108 , for example, controls the temperature and humidity of dry nitrogen gas and supplies it to the second nozzle  129 . The opening/closing drive units of the valves  134 ,  136 ,  141  and  143  are controlled by the controller  160 . 
     The elevation mechanism  23  for elevating the cup  20  will now be described. 
     The elevation mechanism  23  is provided below the cup  20 . The elevation mechanism  23  comprises a motor  24 , a driving pulley  24   a , a timing belt  25 , a driven pulley  26   a , ball nut  26   b  and a ball screw  26   c . An upper end portion of the ball screw  26   c  is rotatably coupled to the lower part of the cup  20 , and a lower end portion of the ball screw  26   c  is rotatably coupled to a stationary frame (not shown). The ball nut  26   b  is engaged the ball screw  26   c  and coupled to the driven pulley  26   a . The timing belt  25  is passed between the pulleys  24   a  and  26   a . The operation of the motor  24  is controlled by the controller  160 . 
     The elevation mechanism  23  vertically moves the cup  20  such that the level of the opening  20   e  varies in a range between an upper position P 1  and a lower position P 2 . Specifically, the cup opening  20   e  is located at position P 0  when the cup  20 H indicated by a solid line in FIG. 13 is in the home position. The opening  20   e  is located at position P 1  when the cup  20 U indicated by an imaginary line in FIG. 13 is in its upper position, and at position P 2  when the cup  20 L indicated by an imaginary line in FIG. 13 is in its lower position. 
     In this description, the position of the wafer W relative to the cup  20  when the cup opening  20   e  is at the upper position P 1  is defined as “first relative height position”, and the position of the wafer W relative to the cup  20  when the opening  20   e  is at the home position P 0  or lower position P 2  is defined as “second relative height position.” 
     With reference to FIGS. 14,  15 A to  15 D and  4 , the process of washing, rinsing and drying the semiconductor wafer W with use of the above apparatus will now be described. 
     The wafer W is taken out of the cassette C by the sub-arm mechanism  3 , and the wafer W is transferred from the sub-arm mechanism  3  to the main arm mechanism  5 . The main arm mechanism  5  carries it to the washing/drying process apparatus  7 . 
     If the wafer W to be processed has reached the apparatus  7 , the cup  20  is lowered and the cup opening  20   e  is located at the lower position P 2 , as shown in FIG. 15A (step S 21 ). The shutter (not shown) is opened and the wafer holder of the main arm mechanism  5  is introduced into the casing  7   b . The wafer W is placed on the spin chuck  10  (step S 22 ). The wafer W is located higher than the cup opening  20   e . The wafer holder of the main arm mechanism  5  is retreated from the casing  7   b  and the shutter (not shown) is closed. 
     Subsequently, the cup  20  is raised and the cup opening  20   e  is located at the higher position P 1 , as shown in FIG. 15B (step S 23 ). At this time, the wafer W is in the “first relative height position” relative to the cup  20 . Specifically, the wafer W is located sufficiently below the cup opening  20   e , and the wafer W is completely surrounded by the cup  20 . The nozzle support member  132  is moved so that the nozzle  128  is located above the center of rotation of the wafer W. The distance L 1  between the discharge port of first nozzle  128  and the upper surface of the wafer W is set at 10 mm to 15 mm. 
     The rotation of the spin chuck  10  is started (step S 24 ), and the discharge of the chemical solution as first process fluid from the first nozzle  128  is started (step S 25 ). The chemical solution is spread over the entire upper surface of the wafer W by centrifugal force, and the upper surface of wafer W is uniformly chemically washed. The chemical solution is centrifugally separated from the wafer W and applied to the inner wall of the cup  20 . The applied chemical solution flows down along the inner wall of the cup  20 . The waste liquid (chemical solution) flows from the cup  20  through the exhaust pipe  21  to the recovery circuit  70  shown in FIG. 4. A gas component is separated and removed from the waste liquid by the gas-liquid separator  72 . The waste liquid is then stored in the tank  72 . The waste liquid is circulated from the tank  71  to the circulation circuit  80  by the pump  83  and heated by the heater  85 . Impurities in the waste liquid is then removed by the filter  86  and returned to the tank  71 . Through this circulation, the waste liquid in the tank  71  is purified. The thus regenerated liquid is supplied for reuse to the first nozzle  128  through the return circuit  33 . 
     After a predetermined wash process time, the valve  134  is closed and the discharge of chemical solution from the first nozzle  128  is stopped (step S 26 ). The rotational speed of the spin chuck  10  is switched from low level to high level and the liquid on the wafer W is centrifugally separated and removed. 
     The cup  20  is lowered and the cup opening  20   e  is set at the home position P 0 , as shown in FIG. 15C (step S 27 ). At this time, the wafer W is located slightly below the cup opening  20   e  (“second relative height position). 
     The valve  136  is opened and the discharge of pure water as second process fluid from the first nozzle  128  is started (step S 28 ). The pure water is spread over the entire upper surface of the rotating wafer W due to centrifugal force, and the upper surface of the wafer W is uniformly rinsed. At this time, the pure water centrifugally separated from the wafer W is applied to the over-hang portion  20   f  of the cup and flows down from the over-hang portion  20   f . Thus, the chemical solution on the entire inner wall of the cup  20  is removed. Specifically, the upper surface of the wafer W and the inner wall of the cup  20  are simultaneously rinsed. 
     After a predetermined rinse process time, the discharge of pure water from the first nozzle  128  is stopped and the first nozzle  128  is retreated from the position above the wafer W (step S 29 ). The rotational speed of the spin chuck  10  is switched from the low level to high level and the liquid on the wafer W is centrifugally separated and removed. 
     Then the cup  20  is raised and the cup opening  20   e  is located at the upper position P 1 , as shown in FIG. 15B (step S 30 ). At this time the wafer W is set at the “first relative height position” relative to the cup  20 . Specifically, the wafer W is located sufficiently below the cup opening  20   e  and the wafer W is completely surrounded by the cup  20 . 
     The nozzle support portion  140  is moved and the second nozzle  129  is located at a point above the center of rotation of the wafer W. The second nozzle  129  is approached to the wafer W and the distance L 2  between the discharge port of second nozzle  129  and the upper surface of wafer W is set at 2 mm to 8 mm. 
     The discharge of IPA vapor as first process fluid from the second nozzle  129  is started (step S 31 ). A predetermined amount of N 2  gas is mixed in the IPA vapor. The IPA vapor is spread over the entire upper surface of the wafer W, and water on the upper surface of the wafer W is removed. Part of the IPA vapor is liquefied and the liquefied IPA flows down along the inner wall of the cup as waste liquid. The waste liquid (IPA liquid) flows through the discharge pipe  21  from the cup  20  to another recovery circuit (not shown). A gas component is separated and removed from this waste liquid by another gas-liquid separator (not shown) and stored in another tank (not shown). In addition, the waste liquid (IPA liquid) is circulated from the tank to another circulation circuit (not shown) by another pump (not shown), heated by a heater (not shown), passed through a filter (not shown) to remove impurities, and returned to the tank. The waste liquid in the tank is purified through the circulation circuit. The thus regenerated liquid is returned to the supply source  106  through another return circuit (not shown) for reuse. 
     After a primary drying process time, the valve  141  is closed and the discharge of IPA vapor from the second nozzle  128  is stopped (step S 32 ). 
     Subsequently the cup  20  is lowered and the cup opening  20   e  is set at the home position P 0 , as shown in FIG. 15C (step S 33 ). At this time, the wafer W is located slightly lower than the cup opening  20   e  (“second relative height position”). 
     The valve  143  is opened and the discharge of dry N 2  as second process liquid from the second nozzle  129  is started (step S 34 ). The dry N 2  gas is spread over the entire upper surface of the rotating wafer W and thus the upper surface of wafer W is finally dried. At this time, the dry N 2  gas bounces off the wafer W, hits the over-hang portion  20   f  of the cup  20 , and flows down along the inner wall of the cup  20  from the over-hang portion  20   f . Thus, the entire inner wall of the cup  20  is dried. Specifically, the upper surface of the wafer W and the inner wall of the cup  20  are simultaneously finally dried. 
     After a predetermined final dry process time, the valve  143  is closed and the discharge of dry N 2  gas from the second nozzle  129  is stopped (step S 35 ). Then, the second nozzle  129  is retreated from the position above the wafer W and the rotation of the wafer W is stopped (step S 36 ). 
     Subsequently, the cup  20  is lowered and the cup opening  20   e  is set at the lower position P 2 , as shown in FIG. 15D (step S 37 ). At this time, the wafer W is located slightly above the cup opening  20   e . The shutter (not shown) is opened and the wafer holder of main arm mechanism  5  is introduced into the casing  7   b . The wafer W is taken up from the spin chuck  10  and carried out of the apparatus  7  (step S 38 ). The shutter (not shown) is closed, the cup  20  is raised, and the cup opening  20   e  is set at the home position P 0  (step S 39 ). 
     The wafer W carried out of the process apparatus  7 A is transferred to the next process apparatus  8 . In the process apparatus  8 , too, a similar washing/drying process is performed. At last, the wafer W is finally washed with pure water and dried in the process apparatus  9 . The processed wafer W is restored to the cassette C and the wafer W along with the cassette C is carried out of the wash process system  1 . 
     According to the above embodiment, the inner wall of the cup  20  including the over-hang portion  20   f  is rinsed in real time and dried in real time with the second process fluid (pure water, N 2  gas). Accordingly, the inner wall of the cup  20  is always kept in a clean state. Thus, contamination with particles on the wafer W is effectively prevented. 
     In addition, according to the above embodiment, almost all the amount of the first process fluid (chemical solution, IPA) is recovered and reused. 
     Therefore, the amount of consumed first process fluid (chemical solution, IPA) can be greatly reduced. 
     Furthermore, the spin chuck  10 , cup  20 , process fluid supply mechanism  130 ,  131 , recovery circuit  50 , tank  51  and return circuit  33  are arranged within single unit  7   a , the length of the recovery circuit  50  and return circuit  33  is decreased and the chemical solution, etc. can be recovered and reused with the area occupied by the single apparatus. Accordingly, the area occupied by the wash process system  1  decreases, the manufacture of semiconductor devices can be facilitated, and the productivity of semiconductor devices is enhanced. 
     In the above embodiment, the system for washing and drying the semiconductor wafer W has been described by way of example. The present invention is not limited to this embodiment and is applicable to a washing/drying process system for other substrates such as LCD glass substrates. 
     In the above embodiment, the system for washing/drying the upper surface (circuit pattern formation surface) alone of the semiconductor wafer W has been described by way of example. This system may be combined with a bottom-surface process apparatus for washing/drying a bottom surface of the wafer W. 
     A third embodiment of the present invention will now be described with reference FIGS. 16 and 17. A description of the parts common to those in the first and second embodiments is omitted. 
     The washing/drying process apparatus of the third embodiment is provided as process apparatus  7 B in the wash process system  1  shown in FIG.  1 . As is shown in FIG. 16, the washing/drying process apparatus  7 B comprises a cup  20 , a spin chuck  220 , a surface (upper surface) process nozzle  230  and a bottom-surface process nozzle  231 . 
     The spin chuck  220  has a table  221  for supporting a peripheral portion of a bottom surface of wafer W. An upper surface of the table  221  has a conical shape with a diameter increasing from its center toward its periphery. A pool  240  is formed on the upper surface  222 . 
     A plurality of pins  23  for guiding and aligning the wafer W are erected on the peripheral portion of the table  221 . As is shown in FIG. 17, three sets of aligning pins  223 , each set comprising three pins, are disposed at three locations (the total number of pins being nine). In addition, three notches  224  are formed at peripheral portions of the table  221  for transfer of the wafer W. 
     A rotary shaft  225  is attached to the lower surface of the table  221  of spin chuck  220 . A pulley  226  is attached to the rotary shaft  225 . A torque of a motor  227  is transmitted to the pulley  226  through another pulley  228  and a belt  229 . 
     A top-surface process nozzle  230  for applying a chemical solution and a rinsing solution to the upper surface of wafer W is movably provided above the spin chuck  220 . The nozzle in the first embodiment or second embodiment may be used for the top-surface process nozzle  230 . 
     A bottom-surface process nozzle  231  communicates with an internal passage  232  in the rotary shaft  225  and opens to a lowermost portion of the pool  240 . The internal passage  232  communicates with a pure water supply source (not shown). Pure water is supplied to the nozzle  231  through the internal passage  232  and discharged from the nozzle  231  to the pool  240 . The discharge port of the nozzle  231  faces a central area of the bottom surface of the wafer W on the table  221 . The atmosphere in the cup  20  is exhausted from the bottom of the cup  20  by a vacuum pump (not shown) provided outside. 
     A description will now be given of the processing of the upper surface and lower surface of the wafer W by the apparatus  7 B. 
     The wafer W is placed on the table  221  of spin chuck  220 . The spin chuck  220  is rotated at a speed of, e.g. 20 rpm. Then a chemical solution is discharged from the nozzle  230  to the upper surface of wafer W, and pure water is discharged from the nozzle  231  to the lower surface of wafer W. Thus, the upper surface and lower surface of wafer W are simultaneously processed. 
     If the chemical solution washing of the upper surface of wafer W is finished, pure water is supplied from the nozzle  230  to rinse the upper surface of wafer W. 
     On the other hand, when the lower surface of wafer W is to be rinsed, pure water is jetted from the nozzle  231  to a central area of the lower surface of the rotating wafer W. The pure water is uniformly spread by centrifugal force from the center of the lower surface of the wafer toward the periphery thereof. In addition, it should suffice to quietly supply pure water from the nozzle  231  to the pool  240 . The pure water in the pool  240  flows from the center of the pool  240  toward the periphery there of by centrifugal force, and overflows through a gap between the wafer W and table  221 . The pure water spattered to the surrounding of the wafer W by centrifugal force flows down along the inner wall of cup  20  and exhausted through discharge pipes  21 . Since pure water is constantly supplied from the nozzle  231 , as described above, fresh pure water is always fed from the center toward the periphery of upper surface  222  of spin chuck  220 . 
     In this manner the entire lower surface of wafer W is rinsed. Since pure water is constantly supplied to the lower surface of wafer W during the rinsing step, the lower surface of wafer is coated with pure water without contact with outside air 
     After a predetermined process time, the supply of pure water from the nozzle  231  is stopped and the washing process for the lower surface of wafer W is finished. Subsequently, the spin chuck is rotated at higher speed, pure water is removed from the lower surface of wafer W, and the lower surface of wafer W is subjected to a drying process. Not only pure water but also a chemical solution for chemical washing may be applied to the lower surface of wafer W. 
     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.