Abstract:
A heat processing apparatus comprises a heating section having a hot plate for heating a substrate in a heat conduction manner, refrigeration medium for decreasing temperature of the hot plate in a heat exchange manner by bring the refrigeration medium in direct or indirect contact with the hot plate, a refrigeration section for storing the refrigeration medium while cooling, a transport mechanism for taking out the refrigerant from the refrigeration section, transporting the refrigeration medium to the heating section, mounting the refrigeration medium on the hot plate, picking up the refrigeration medium from the hot plate, taking out the refrigeration medium from the heating section, and transporting the refrigeration medium to the refrigeration section, setting mechanism for setting a heat processing temperature for the substrate, and a controller for controlling temperature of the hot plate by using the refrigeration medium so as to reach the heat processing temperature set by the setting mechanism.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a heat processing apparatus such as a heating apparatus and a preheating apparatus to be installed in a semiconductor manufacturing system for manufacturing a semiconductor device. 
     In a photolithography process for manufacturing a semiconductor device and an LCD, resist is coated on a substrate, and the resultant resist coating film is exposed to light and developed. Such a series of processing is carried out in a coating/developing system. The coating/developing system has heating units such as a prebake unit and a postbake unit. These heating units have a hot plate with a built-in heater of a resistance heating type. 
     The wafers W are processed in units (lots) each consisting of, e.g., 25 wafers. Each lot is processed under the same recipe (individual processing program). Heating is performed under the conditions such as prebaking temperature and postbaking temperature according to the recipe. The wafers belonging in the same lot are heated under the same conditions. 
     Then, when one lot is completed and a new lot is subjected to the processing, the recipe is switched to a new recipe, accordingly, so that temperature of the hot plate changes. When the heat processing temperature is allowed to change from a low temperature range to a high temperature range, the temperature of the hot plate can be changed immediately if electric supply to the hot plate is increased. However, the heat processing temperature is allowed to switch from the high temperature range to the low temperature range, the temperature of the hot plate cannot be decreased in a short time. This is because a conventionally used heating unit employs an air cooling method. To be more specifically, the hot plate is cooled by blowing a cold air thereon. Since the hot plate (metal disk of approximately 16 mm thick) has a large heat capacity, it takes a long time to decrease the temperature of the hot plate to a desired temperature, thus lowering a throughput. 
     To overcome the low throughput, if hot plates are provided so as to correspond to the number of different recipes, the hot plates will occupy a huge space. As a result, the apparatus will increase in size and its control system will be more complicated. 
     To use a single hot plate for different heat processes, it is possible to consider an apparatus equipped with a hot plate having a refrigerant circulating therein to cool the hot plate in a short time. The apparatus of this type has a problem in that the structure of the hot plate becomes complicated, increasing the manufacturing cost. 
     BRIEF SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a heat processing apparatus capable of decreasing temperature of a hot plate in a short time and in a high throughput without complicating a control system. 
     The heat processing apparatus according to the present invention has 
     a heating section having a hot plate for heating a substrate in a heat conduction manner; 
     refrigeration medium for decreasing temperature of the hot plate in a heat exchange manner by bringing the refrigeration medium in direct or indirect contact with the hot plate; 
     a refrigeration section for storing the refrigeration medium while cooling; 
     a transport mechanism for taking out the refrigeration medium from the refrigeration section, transporting the refrigeration medium to the heating section, mounting the refrigeration medium on the hot plate, picking up the refrigeration medium from the hot plate, taking out the refrigeration medium from the heating section, and transporting the refrigeration medium to the refrigeration section; 
     setting means for setting a heat processing temperature for the substrate; and 
     a controller for controlling temperature of the hot plate by using the refrigeration medium so as to reach the heat processing temperature set by the setting means. 
     The heat processing apparatus further comprises a sensor for detecting temperature of the hot plate. 
     In this case, it is preferable that the controller should control the contact time for the hot plate in contact with the refrigeration medium on the basis of the temperature of the hot plate detected by the sensor and the heat processing temperature determined. 
     In the case where the refrigeration medium includes a plurality of refrigeration members different in heat capacity, it is preferable that the controller should select one or two refrigeration members from the refrigeration members on the basis of the temperature of the hot plate detected by the sensor and the heat processing temperature determined, and that the transport mechanism should transport the one or two refrigeration members selected, from the refrigeration section to the heating section, mounting the one or two refrigeration members on the hot plate to allow the one or two refrigeration members in contact with the hot plate for the contact time, and transporting the one or two refrigeration members from the heating section to refrigeration section. 
     In the case where the refrigeration medium includes a plurality of refrigeration members different in heat capacity, the refrigeration members may be different in thickness and in material. 
     Furthermore, it is preferable that the controller should control temperature for cooling the refrigeration medium in the refrigeration section on the basis of the temperature of the hot plate detected by the sensor and the heat processing temperature determined. 
     It is further preferable that the refrigeration medium has a plan-view shape substantially the same as that of the substrate. 
     It is still preferable that the refrigeration medium should be made of a material containing no harmful ingredients to not only the substrate but also a film formed on the substrate. 
     Incidentally, it is preferable that the transporting mechanism should place the refrigeration medium on the hot plate so as to cover an area of the hot plate at which the substrate comes in contact with the hot plate or near which the substrate is placed so as to face the hot plate. 
     Furthermore, the refrigeration section has 
     a plurality of cooling plates each cooling the corresponding refrigeration medium refrigerant in a heat conduction manner, 
     a lift mechanism having a plurality of pins pushing up the refrigeration medium from each of the cooling plates; and 
     a plurality of compartments each surrounding the corresponding cooling plate. 
     The refrigeration section has 
     a cooling plate for collectively cooling the refrigeration medium stacked one upon the other in multiple stages, 
     a lift mechanism having a plurality of pins for pushing up at least one of the refrigeration medium from the cooling plate, and 
     a compartment surrounding the cooling plate. 
     In this case, the pins may be arranged on a common concentric circle in the same plane. 
     Alternatively, the pins are arranged by being divided on two concentric circles in the same plane. 
     Note that it is preferable that a high purity silicon (Si), silica glass (SiO 2 ) and silicon carbide (SiC) may be used as the refrigeration medium. This is because they are stable even in a high temperature range and no possibility of contaminating a silicon wafer. 
     The refrigeration medium desirably has substantially the same plan-view shape as the substrate. In this case, the refrigeration medium refrigerants can be designed so as to have various heat capacities by changing thickness and material of the refrigeration medium. 
     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 hereinafter. 
    
    
     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 schematic plan view showing a coating/developing system; 
     FIG. 2 is a front view of the coating/developing system; 
     FIG. 3 is a rear view of the coating/developing system; 
     FIG. 4 is a block diagram showing a heat processing apparatus according to an embodiment of the present invention; 
     FIG. 5 is a plan view showing a heating unit of the heat processing apparatus according to an embodiment of the present invention; 
     FIG. 6 is a longitudinal sectional view of the heating unit of the heat processing apparatus according to an embodiment of the present invention; 
     FIG. 7 is a sectional view of a refrigeration section of the heat processing apparatus according to the present invention accompanying a block diagram of peripheral elements; 
     FIG. 8 is a plan view of the refrigeration section of the heat processing apparatus according to the present invention; 
     FIG. 9 is a longitudinal sectional view showing the refrigeration section of the apparatus according to an embodiment; 
     FIG. 10 is a longitudinal sectional view showing the refrigeration section of the apparatus according to the embodiment; 
     FIG. 11 is a longitudinal sectional view showing the refrigeration section of the apparatus according to an embodiment; 
     FIG. 12 is a plan view showing a refrigerant according to another embodiment; 
     FIG. 13 is a plan view showing a refrigerant according to still another embodiment; and 
     FIG. 14 is a cross sectional view of a heating unit of a heat processing apparatus according to a further embodiment accompanying a block diagram of peripheral elements. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Now, various preferred embodiments of the present invention will be explained with reference to the accompanying drawings. 
     As shown in FIGS. 1-3, a coating/developing system  1  has a load/unload section  10 , a process section  11 , and an interface section  12 . The load/unload section  10  has a cassette table  20  on which cassettes CR storing e.g., 25 semiconductor wafers W for each, is loaded/unloaded. The process section  11  has various single wafer processing units for processing wafers W sequentially one by one. The interface section  12  is arranged between the process section  11  and a light-exposure apparatus (not shown). 
     Four projections  20   a  are formed on the cassette table  20 . Four cassettes CR are positioned respectively in right places to the process section  11  by means of these projections  20   a . Each of the cassettes CR mounted on the table  20  has a load/unload opening facing the process section  11 . 
     In the load/unload section  10 , a first sub-arm mechanism  21  is formed which is responsible for loading/unloading the wafer W into/from each cassette CR. The first sub arm mechanism  21  has a holder portion for holding the wafer W, a back and forth moving mechanism (not shown) for moving the holder portion back and forth, an X-axis moving mechanism (not shown) for moving the holder portion in an X-axis direction, a Z-axis moving mechanism (not shown) for moving the holder portion in a Z-axis direction, and a θ rotation mechanism (not shown) for swinging the holder portion around the Z-axis. 
     The first sub-arm mechanism  21  can gain access to an alignment unit (ALIM) and an extension unit (EXT) belonging to a third process unit group G 3 . 
     As shown in FIG. 3, a main arm mechanism  22  is liftably arranged at the center of the process section  11 . Five process units G 1 -G 5  are arranged around the main arm mechanism  22 . The main arm mechanism  22  is arranged within a cylindrical supporting frame  49  and has a liftable wafer transporting apparatus  46 . The cylindrical supporting frame  49  is connected to a driving shaft of a motor (not shown). The driving shaft can be rotated about the Z-axis in synchronism with the wafer transporting apparatus  46  by an angle of θ. The wafer transporting apparatus  46  has a plurality of holder portions movable in a front and rear direction of a transfer base table  47 . 
     Units belonging to first and second process unit groups G 1 , G 2 , are arranged at the front side of the system  1 . Units belonging to a third process unit group G 3  are arranged next to the load/unload section  10 . Units belonging to a fourth process unit group G 4  are arranged next to the interface section  12 . Units belonging to a fifth process unit group G 5  are arranged at a back side of the system  1 . 
     As shown in FIG. 2, the first process unit group G 1  has two spinner-type process units for applying a predetermined process to the wafer W mounted on a spin chuck within the cup CP. In the first process unit G 1 , for example, a resist coating unit (COT) and a developing unit (DEV) are stacked in two stages sequentially from the bottom. In the second process unit group G 2 , two spinner type process units such as a resist coating unit (COT) and a developing unit (DEV) in two stages sequentially from the bottom. The resist coating unit (COT) is preferably set at a lower stage than the developing unit (DEV). This is because a discharge line for the resist waste solution is desired to be shorter than a developing waste solution since the resist waste solution is more difficult to discharge than the developing waste solution. However, if necessary, the resist coating unit (COT) may be arranged at the upper stage than the developing unit (DEV). 
     As shown in FIG. 3, the third process unit group G 3  has a cooling unit (COL), an adhesion unit (AD), an alignment unit (ALIM), an extension unit (EXT), a prebaking unit(PREBAKE), and postbaking unit (POBAKE) which are stacked sequentially from the bottom. 
     Similarly, the fourth process unit group G 4  has a cooling unit (COL), an extension cooling unit (EXTCOL), an extension unit (EXT), a cooling unit (COL), a prebaking unit (PREBAKE) and a postbaking unit (POBAKE). 
     As mentioned, the cooling unit (COL) and the extension cooling unit (EXTCOL) to be operated at low processing temperatures, are arranged at lower stages and the baking unit (PREBAKE), the postbaking unit (POBAKE) and the adhesion unit (AD) to be operated at high temperatures, are arranged at the upper stages. With this arrangement, thermal interference between units can be reduced. Note that a unit  103  of the cooling units (COL) positioned at the lowest stage is used as a refrigerator (refrigeration unit) for refrigerating and storing a refrigeration medium  110 . 
     At the front side of the interface section  12 , a movable pick-up cassette CR and an non-movable buffer cassette BR are arranged in two stages. At the back side of the interface section  12 , a peripheral light exposure apparatus  23  is arranged. At the center portion of the interface section  12 , a second sub-arm mechanism  24  is provided, which is movable independently in the X and Z directions, and which is capable of gaining access to both cassettes CR and BR and the peripheral light exposure apparatus  23 . In addition, a second sub-arm mechanism  24  is rotatable around the Z-axis by an angle of θ and capable of gaining access to the extension unit (EXT) belonging to the fourth processing unit G 4  and to a wafer transfer table (not shown) near the light exposure apparatus (not shown). 
     In the system  1 , the fifth processing unit group G 5  can be arranged at the back side of the main arm mechanism  22 . The fifth processing unit G 5  can be slidably shifted in the Y-axis direction along a guide rail  25 . Since the fifth processing unit group G 5  can be shifted as mentioned, maintenance operation can be applied to the main arm mechanism  22  easily from the back side. 
     As shown in FIG. 4, a temperature sensor  59  is provided to a hot plate  58  of a heating unit  99 . A signal line of the sensor  59  is connected to an input portion of the controller  120 . A plurality of temperature detection signals are sent from individual sensors  59  and individually input to the controller  120 . To the input portion of the controller  120 , a signal line from a sensor (not shown) of the main arm mechanism  22  is connected. The sensor checks operation of the driving section  22   m  in terms of the rotation number and input the signal into the controller  120 . Furthermore, to the input portion of the controller  120 , a data-input keyboard (not shown) is connected by which data of a recipe corresponding to each lot is input. 
     On the other hand, to an output portion of the controller  120 , a power source (not shown) for a hot plate  58  of the heating unit  99 , a power source  122  (see FIG. 7) for a cooling plate  102  of a refrigeration section  103 , and a power source (not shown) for the driving section  22   m  of the main arm mechanism  22 , are independently connected. The controller  120  controls the power source  122  for the cooling plate  102  on the basis of the temperature detection signal and the operation check signal (i.e., rotation counting signal). In other words, the temperature of the refrigeration medium  110  refrigerated in the refrigeration unit  103  as well as time for cooling the hot plate  58  by the refrigeration medium  110  (which has been refrigerated by the refrigeration unit  103 ) mounted on the hot plate  58  are obtained by the controller. The controller  120  further controls the power source  122  on the basis of the temperature and the time thus obtained. In this manner, the hot plate  58  can be reduced in temperature efficiently in the minimum time. 
     As another temperature controlling method for the hot plate, a refrigeration section  103  housing a plurality of refrigerants different in heat capacity, may be employed, as shown in FIGS. 9-11. In this case, the controller  120  calculates the balance between incoming and outgoing heat amounts on the basis of the temperature of the hot plate  58  and a predetermined heat processing temperature on recipe, with respect to a plurality of refrigeration members  110 A,  110 B,  110 C,  110 D,  110 E,  110 F,  110 G and  110 H. In this way, the most suitable refrigerant is selected and allowed in contact with the hot plate  58 . 
     Alternatively, an appropriate refrigeration medium  110  may be selected from the refrigeration members  110 A to  110 H and allowed to be in contact with the hot plate  58 . In this case, as a first strategy, the refrigeration medium  110  having the most suitable heat capacity may be selected on the basis of the actually measured temperature of the hot plate  58  and the predetermined temperature on recipe (first strategy: heat-capacity choice). Note that thickness of the refrigeration medium  110  may be varied within the range of 1 to 10 mm. It is desirable to prepare a series of refrigeration medium  110  having various heat capacities. For example, refrigeration members  110 A,  110 B,  110 C, and  110 D having a thickness of 1 mm, 2.5 mm, 4 mm, and 5.5 mm can be prepared and stored in refrigeration chambers  11 A,  111 B,  111 C and  111 D, respectively. Furthermore, it is desirable that a high purity silicon (Si), silica glass (SiO 2 ) and silicon carbide (SiC) may be used as the refrigeration medium  110 . These materials are stable in the high temperature range and do not contaminate the silicon wafer. 
     As a second strategy, a desired refrigeration temperature of the refrigeration medium  110  is obtained by the controller  120  on the basis of the actually measured temperature of the hot plate  58  and the predetermined temperature on recipe, and then, the refrigeration medium  110  may be refrigerated by the refrigeration unit  103  so as to reach the desired refrigeration temperature (second strategy: refrigeration driving control). 
     Furthermore, as a third strategy, the contact time for the refrigeration medium  110  to be contact with the hot plate  58  is first obtained by the controller  120  on the basis of the actually measured temperature of the hot plate  58  and the predetermined temperature on recipe, and then the refrigeration medium  110  may be loaded and unload into and from the heating unit  99  so as to satisfy the contact time thus obtained (third strategy: cooling time control). 
     Note that two or three strategies selected from the first to third strategies may be used in combination. Any strategy is preferable as an efficient controlling method. 
     Referring now to FIGS. 5 and 6, the heating unit  99  will be explained. 
     The heating unit  99  includes a prebaking unit (PREBAKE) a postbaking unit (POBAKE), and an adhesion unit (AD) for heating the wafer W to a temperature at least higher than room temperature. A processing chamber  50  of the heating unit  99  has a hot plate  58  having a heater of resistance heating (not shown) and a temperature sensor  59  therein. The hot plate has a thickness of 3 mm made of ceramics. The heat capacity of the hot plate is approximately 164 J/K. 
     Note that the hot plate  58  may be constructed in a jacket form having a hollow portion therein. The wafer W may be heated by supplying and circulating a heat medium through the hollow portion. Alternatively, as shown in FIG. 14, heat pipes  58   b ,  93  may be introduced into a vacant space within the hot plate  58   a  to heat the hot plate  58 . 
     The processing chamber is defined by a side wall  52 , a horizontal shielding plate  55 , and a cover  68 . Opening portions  50 A,  50 B are formed respectively at the front side (near a passage of the main arm mechanism  22 ) and a back side of the processing chamber  50 . The wafer W is loaded into and unloaded from the processing chamber  50  through the openings  50 A and  50 B. A circular opening  56  is formed at the center of the horizontal shielding plate  55 . The hot plate  58  is housed in the opening  56 . The hot plate  58  is supported by a supporting plate  76  in concert with the horizontal shielding plate  55 . 
     Three holes  60  are formed through the hot plate  58 . A lift pin  62  is inserted into each of three holes  60 . Three lift pins  62  are connected to and supported by an arm  80 . The arm  80  is connected to and supported by a rod  84   a  of a vertical cylinder  84 . When the rod  84   a  is allowed to project from the cylinder  84 , the lift pins  62  project to lift up the wafer-W from the hot plate  58 . 
     A ring-form shutter  66  is attached to the outer periphery of the hot plate  58 . A plurality of air holes  64  are formed along the periphery of the shutter  66  at intervals of central angles of 2°. The air holes  64  communicate with a cooling gas supply source (not shown). 
     The shutter- 66  is liftably supported by a cylinder  82  via an arm  78 . The shutter  66  is positioned at a place lower than the hot plate  58  at non-operation time and lifted to a position higher than the hot plate  58  and between the hot plate  58  and the cover  68 , at an operation time, as shown in FIG.  6 . When the shutter  66  is lifted up, nitrogen gas or air (cooling gas) blows out from the air holes  64 . 
     An exhaust port  68   a  is opened at the center of the cover  68  so as to communicate with the exhaust pipe  70 . Gas generated from the surface of wafer W at the heating processing time is exhausted through the exhaust port  68   a . The exhaust pipe  70  communicates with a duct  53  (or  54 ) at the front side (near the main arm mechanism  22 ) of the apparatus or another duct (not shown). 
     A machine room  74  is formed below the horizontal shielding plate  55 . The machine room  74  is defined by the shielding plate  55 , two side walls  53  and a bottom plate  72 . In the machine room  74 , a hot plate supporting plate  76 , a shutter arm  78 , a lift pin arm  80 , a liftable cylinder  82 , and a liftable cylinder  84  are arranged. 
     As shown in FIG. 5, four projections  86  are formed on an upper surface of the hot plate  58 . The wafer W can be positioned at a right place by means of the four projections  86 . In addition, a plurality of small projections (not shown) are formed on the upper surface of the hot plate  58 . When the wafer W is mounted on the hot plate  58 , top portions of these small projections come in touch with the wafer W. By virtue of the presence of the small projections, a small gap is formed between the wafer W and the hot plate  58 . It is therefore possible to prevent the lower surface of the wafer W from being stained and damaged. 
     Referring now to FIGS. 7 to  13 , various refrigeration sections  103  will be explained. 
     The refrigeration section  103  may be formed of a plurality of compartments (refrigerators)  111 A- 111 D stacked in multiple stages, as shown in FIG.  7 . Alternatively, the refrigeration section  103  is formed of a single compartment  111 E as shown in FIG.  11 . As the refrigeration medium  110 , refrigeration members  110 B and  110 D different in thickness (different in heat capacity) or the refrigeration members  110 E and  110 F different in material (different in heat capacity) may be stacked upon the hot plate  58 . In the case where a sufficient heat capacity is not expected to obtain by the presence of the refrigeration member  110 D (5.5 mm thick) alone, the refrigeration member  110 B (2.5 mm thick) may be stacked upon the refrigeration member  10 D, as shown in FIG.  9 . In the case where a sufficient heat capacity is not expected to obtain by the presence of the refrigeration member  110 E made of pure silicon, the refrigeration member  110 F made of silicate glass (or silicon carbide) may be further stacked upon the refrigeration member  110 E, as shown in FIG.  10 . To improve a heat exchange rate (heat conductivity) between the hot plate  58  or a cooling plate  102  and the refrigeration medium  110 , a minute fin or an elastic layer may be formed on the lower surface of the refrigeration medium  110 . 
     As shown in FIG. 7, a housing  100  of the refrigeration section  103  is divided into  4  compartments  11 A,  111 B,  111 C, and  111 D. The cooling plate  102  is housed in each of the compartments  11 A,  111 B,  111 C, and  111 D. The refrigeration members  110 A,  110 B,  110 C and  110 D different in heat capacity (different in thickness) are respectively mounted on the cooling plates  102  of four compartments. A shutter  106  is attached to each of loading or unloading port  101  of the compartments  11 A,  111 B,  111 C, and  111 D. A plurality of through-holes (not shown) are formed through the cooling plate  102 . A lift pin  162  is provided through each of the through-holes so as to protrude from the cooling plate  102 . When the shutter  106  is opened, the refrigeration member  110 B is lifted up by the lift pins  162 . A holder  22   a  of the main arm mechanism is inserted into the compartment  111 B and then the lift pins  162  are moved down. In this way, the refrigeration member  110 B is transferred from the lift pins  162  to the arm holder  22   a . Note that to reduce the size of the compartments  111 A,  111 B,  111 C, and  111 D in the Z direction as small as possible, the shutter  106  is connected to the rod  107  of the horizontal cylinder  108 , as shown in FIG. 8, thereby sliding in the horizontal direction. 
     The cooling plate  102  houses a cooling element  102   a . Electric power is supplied to each of the cooling elements  102   a  from a common power source  122  controlled by the controller  120 . As the cooling element  102   a , a thermo-element using Peltier effect, is used. Furthermore, a temperature sensor (not shown) may be buried in the cooling plate  102 . The temperature sensor plays a role in detecting temperature of the cooling plate  102  and send a signal of the detected temperature to the controller  120 . 
     The refrigeration members  110 A,  110 B,  10 C,  110 D are formed of pure silicon disks having substantially the same diameter of the wafer W. However, they are different in thickness, e.g., 1 mm, 2.5 mm, 4 mm, 5.5 mm, respectively. Therefore, refrigerants different in heat capacity can be provided. The refrigerants used in this embodiment are uniform in thickness. However the center portions of the refrigerants may be slightly thicker than the peripheral portion. Such a refrigerant may make up for the insufficiency in cooling ability of the center portion. 
     As the cooling plate  102 , a refrigerant jacket may be used which is constituted of a disk-form plate made of metal such as aluminium or copper and a refrigerant passage formed inside the jacket. In this case, the controller drives a refrigerator compressor while controlling, thereby controlling a refrigerant flow rate to a refrigerant jacket. In this manner, the cooling ability of the refrigerator compressor can be controlled. 
     As shown in FIG. 8, the cooling plate  102  is positioned virtually at the center of the housing  100  (box form) of the refrigeration section  103 . The refrigeration medium  110  is loaded into and unloaded from the refrigeration section  103  by the main arm mechanism  22 . The holder  22   a  of the main arm mechanism has a plurality of support projections  22   c  protruding toward the inside of the ring member  22   b . By the presence of the support projections  22   c , the refrigeration medium  110  is in contact with and supported by the ring member  22   b  at the peripheral portion alone. Not that not only the refrigeration medium  110  but also the wafer W may be cooled in the refrigeration section  103 . 
     Now, referring to FIGS. 11-13, a refrigeration section  103  of another embodiment will be explained. 
     The refrigeration section  103  has a single compartment  111 E, which is capable of cooling two refrigeration members  110 G and  110 H placed therein. The compartment  111 E is partitioned into upper and lower chambers  201 ,  202  by a horizontal partition plate  100   c . The upper chamber  201  has a port  101  opened or closed by a shutter  106  and a cooling plate  102 A. The lower chamber  202  has first and second lift pins  262 ,  263 , horizontal arms  281 ,  283 , liftable cylinders  282 ,  284 . Driving sources (not shown) for two liftable cylinders  282 ,  284  are independently controlled by the controller  120 . 
     Three first lift pins  262  are supported by the horizontal arm  281 , which is connected to a rod  282   a  of the liftable cylinder  282 . Three second lift pins  263  are supported by the horizontal arm  283 , which is connected to a rod  284   a  of the liftable cylinder  284 . Three first through-holes  102   c  and three second through-holes  102   d  are formed through the cooling plate  102 A. The first lift pin  262  is inserted into each of the first through holes  102   c , and the second lift pin  263  is inserted into each of the second through holes  102   d . The first and second through-holes  102   c ,  102   d  may be arranged at equal intervals on a common concentric circle  266  as shown in FIG. 12 or may be arranged respectively on two concentric circles  267 ,  268  at equal intervals, as shown in FIG.  13 . 
     As shown in FIG. 11, two refrigeration members  110 G,  110 H are stacked one upon the other on the cooling plate  102 A, as shown in FIG.  11 . The upper refrigeration member  110 H is lifted up by the first lift pins  262 . The lower refrigeration member  110 G is lifted up by the second lift pins  263 . The upper and lower refrigeration members  110 G,  110 H have substantially the same diameter of the wafer W and made of pure silicon. The lower refrigeration member  110 G is thicker than the upper refrigeration member  110 H. The heat capacity of the lower refrigeration member  110 G is nearly double of the upper refrigeration member  110 H. In the lower refrigeration member  110 G, three through-holes  102   c  are formed for inserting the lift pins  262  therethrough, as shown in FIGS. 12 and 13. 
     Next, we will explain how to process the wafer W by using the aforementioned apparatus. 
     When a main switch of the coating/developing system  1  is turned on, power supply is initiated to the heating unit  99  and the refrigeration section  103  from respective power sources. The hot plate  58  of the heating unit  99  is controlled to set at a predetermined processing temperature. The cooling pate  102  of the refrigeration section  103  is controlled to be set at, for example, 10° C. The temperature of the cooling plate  102  is set in consideration of the predetermined heat processing temperature (heat processing temperature to be applied to the wafer W in each of the heating processes for each lot) and the heat capacity of the hot plate  58 . The time required for the refrigeration medium  110  to be in contact with the hot plate  58  is calculated by the controller  120  using a predetermined equation for seeking the balance between incoming and outgoing heat amounts, on the basis of there conditions (temperature, heat capacity, heat dissipation coefficient). It is possible to know, for example, how many seconds are required for the refrigeration medium  110  (having a heat capacity of a certain value or more) to be in contact with the hot plate  58 , in order to decrease the temperature of the hot plate  58  from 120° C. to 90° C. by use of the refrigeration medium  110  of 10° C. Note that it may be better for the refrigeration medium  110  to have a total heat capacity larger than that of the hot plate  58 . 
     The wafer W is taken out from the cassette CR by the sub arm mechanism  21  and transferred to the main arm mechanism  22 . The main arm mechanism  22  transfers the wafer W into the resist coating unit (COT)  22 . In the resist coating unit (COT), resist is coated on the surface of the wafer W. Then, the main arm mechanism  22  takes the wafer W from the resist/coating unit (COT) and transfers it to a prebake unit (PREBAKE) of the heating unit  99 . 
     Then, the shutter  56  is opened to insert the arm holder  22   a  into the processing chamber  50 . Subsequently, the pins  62  are moved up to transfer the wafer W from the arm holder  22   a  onto the pins  62 . The arm holder  22   a  is unloaded from the processing chamber  50  and the pins  62  are moved down to place the wafer W onto the hot plate  58 . At this time, the hot plate  58  is maintained at, for example, 120° C. 
     After heat processing at 120° C. is completed with respect to a manufacturing lot of wafers W, the wafers W of another manufacturing lot are prepared for heat treatment under different temperature condition, for example, at a temperature of 90° C. 
     The main arm mechanism  22  is moved to the refrigeration section  103  to take out the refrigeration medium  110  cooled to 10° C. The main arm mechanism  22  is moved to the heating unit  99  while holding the refrigeration medium  110 . Then, the shutter  56  is opened to insert the arm holder  22   a  into the processing chamber  50 . Subsequently, the pins  62  are moved up to transfer the refrigeration medium  110  from the arm holder  22   a  to the pins  62 . The arm holder  22   a  is unloaded from the processing chamber  50 , and the pins  62  are moved down to place the refrigeration medium  110 , onto the hot plate  58 . After a predetermined time, the refrigeration medium  110  is picked up from the hot plate  58  by the main arm mechanism  22  and returned onto the cooling plate  102  in-the refrigeration section  103 . The hot plate  58  is cooled to a desired temperature of about 90° C. by the refrigeration medium  110  and maintained at 90° C. 
     When the sensor  59  detects the temperature of the hot plate  58  and the controller  120  confirms that thee temperature of the hot plate  58  is maintained stable at 90° C., the controller  120  sends an instruction signal to the main arm mechanism  22 . Upon reception of the instruction signal, the main arm mechanism  22  initiates loading of the wafers W of another manufacturing lot. The wafers of this manufacturing lot are heat-processed at 90° C. and thereafter subjected to further treatment. 
     In the apparatus according to this embodiment, a refrigeration section  103  is arranged other than the hot plate  58 . When the hot plate  58  is cooled, the refrigeration medium  110  which has been previously cooled in the refrigeration section  103 , is placed on the hot plate  58  for a predetermined time. It is therefore possible to reduce the temperature of the hot plate in a short-time. 
     In the apparatus of this embodiment, only refrigeration section  103  is added without providing any modification to the heating unit. Since the hot plates are not increased in number, enlargement of the apparatus in size is suppressed at minimum. 
     Now, referring to FIG. 14, the heating unit of another example will be explained. 
     A depressed portion  68   b  of a conical shape is formed in the lower portion of the cover  68 . An exhaust port  68   a  is formed near the top of the cone. To the exhaust port  68   a , a lower end of an exhaust tube  70  is connected. The other end of the exhaust tube  70  communicates with an evacuation system (not shown). The gas heated by the hot plate  58  and moved up, is collected at the depressed portion  68  and exhausted through the exhaust port  68   a  and the exhaust tube  70 . 
     In the heating unit  99 , an inner space of the hot plate  58  is a vacant hole  58   a  closed airtight. A heat medium storage  58   b  having a V-shape cross-section is formed in part of the bottom portion of the vacant hole  58   a . In the heat medium  58   b , a resistance heater  93  made of dichromatic wire is arranged in the direction from the front side to the back side of the figure. Electric power is supplied to the heater  93  from the power supply unit  95  controlled by a controller. 
     When power is supplied from the power supply unit  95  to the heater  93 , the heater  93  initiates heat generation. The heat medium which has been condensed in the heat medium storage  58   b , is heated by the heater  93 . The heat medium thus heated is gasified, vaporized and circulates within the vacant hole  58   a . When the vapor from the heat medium comes in contact with a cooled portion of the vacant hole  58   a , the vapor gives heat quantity to the cooled portion and simultaneously condensed. At this time, the heat quantity is the heat of vaporization of the heat medium which is determined depending upon a type of heat medium. Therefore, a series of cycle starting from the vaporization of the heat medium to the condensation thereof reaches stable and constant conditions, the temperature of the hot plate  58  can be kept almost constant. 
     We have explained the case in which the present invention is applied to the resist coating/developing system for use in a semiconductor wafer in the aforementioned embodiments. However, the present invention may be applied to a resist coating/developing system for use in an LCD substrate. 
     According to the present invention, since the temperature of the hot plate can be reduced immediately by the refrigerant, the throughput in processing can be improved remarkably. According to the present invention, the conventionally-used heating unit can be used as it is without any modification, the controlling system need not to be complicated. As a result, it is possible to suppress an increase in manufacturing cost at minimum. In addition, the refrigeration section to be added is simply constructed. The controlling system is thus simple and malfunction of the apparatus rarely occurs. 
     It is therefore possible to improve the throughput in processing without reducing the operation rate of the apparatus. Moreover, the balance between incoming and outgoing heat amounts is calculated on the basis of the actually-measured temperature and a predetermined temperature for heat processing of the hot plate. Based on the calculation, the refrigerant having the most suitable heat capacity is selected, and time for the refrigerant in contact with the hot plate is determined. It is therefore possible to cool the hot plate to the predetermined temperature efficiently in the shortest time. 
     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.