Patent Publication Number: US-2015072078-A1

Title: Substrate treatment method and substrate treatment apparatus

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a substrate treatment method and a substrate treatment apparatus. Exemplary substrates to be treated include semiconductor wafers, substrates for liquid crystal display devices, substrates for plasma display devices, substrates for FED (Field Emission Display) devices, substrates for optical disks, substrates for magnetic disks, substrates for magneto-optical disks, substrates for photo masks, ceramic substrates and substrates for solar cells. 
     2. Description of Related Art 
     Semiconductor device production processes include the step of locally implanting an impurity (ions) such as phosphorus, arsenic or boron, for example, into a front surface of a semiconductor substrate (hereinafter referred to simply as “wafer”). In order to prevent the ion implantation into an unnecessary portion of the wafer, a resist pattern of a photosensitive resin is formed on the front surface of the wafer to mask the unnecessary portion of the wafer with the resist in this step. After the ion implantation, the resist pattern formed on the front surface of the wafer becomes unnecessary and, therefore, a resist removing process is performed for removing the unnecessary resist. 
     In a typical example of the resist removing process, the front surface of the wafer is irradiated with oxygen plasma to ash the resist on the front surface of the wafer. Then, a chemical liquid such as a sulfuric acid/hydrogen peroxide mixture (SPM liquid which is a liquid mixture of sulfuric acid and a hydrogen peroxide solution) is supplied to the front surface of the wafer to remove the asked resist. Thus, the resist is removed from the front surface of the wafer. 
     However, the irradiation with the oxygen plasma for the ashing of the resist damages a portion of the front surface of the wafer uncovered with the resist (e.g., an oxide film exposed from the resist). 
     Therefore, a method of lifting off the resist from the front surface of the wafer by the strong oxidative power of peroxosulfuric acid (H 2 SO 5 ) contained in the SPM liquid supplied onto the front surface of the wafer without ashing the resist has recently been attracting attention (see, for example, JP2005-32819A). 
     SUMMARY OF THE INVENTION 
     A resist formed on the wafer subjected to ion implantation at a higher dose is liable to be altered (hardened). 
     One method of imparting the SPM liquid with a higher resist lift-off capability is to heat the SPM liquid on the front surface of the wafer, particularly a portion of the SPM liquid present around an interface between the front surface of the wafer and the SPM liquid, to a higher temperature (e.g., 200° C. or higher). With this method, even a resist having a hardened surface layer can be removed from the front surface of the wafer without the ashing. One conceivable method for keeping the SPM liquid at a higher temperature around the interface between the front surface of the wafer and the SPM liquid is to continuously supply the higher temperature SPM liquid to the wafer. However, this method increases the use amount of the SPM liquid. 
     The inventors of the present invention contemplate to cover the entire front surface of the wafer with a liquid film of the treatment liquid, while heating the treatment liquid film by means of a heater located in opposed relation to the front surface of the wafer. More specifically, a heater having a smaller diameter than the front surface of the wafer is employed as the heater, and the heater is moved along the front surface of the wafer, for example, at a constant speed while being energized for heating. The amount of heat applied from the heater during the heating is kept constant. This arrangement makes it possible to remove the hardened resist from the wafer while reducing the consumption of the treatment liquid. In addition, the resist lift-off efficiency can be significantly increased, thereby reducing the process time required for the resist lift-off process. 
     If the liquid film heated on the major surface (front surface) of the substrate (wafer) by the heater has a smaller thickness, however, the major surface of the substrate is likely to be damaged. If the liquid film has a greater thickness, on the other hand, the liquid film absorbs the heat applied from the heater. Therefore, the heat does not reach the treatment liquid portion present around the interface between the major surface of the substrate and the liquid film, failing to sufficiently increase the temperature of the treatment liquid portion. That is, there is a demand for advantageously treating the major surface of the substrate with the use of the heater without damaging the major surface. 
     It is therefore an object of the present invention to provide a substrate treatment method and a substrate treatment apparatus which ensure that a major surface of a substrate can be advantageously treated with the use of a heater without any damage thereto. 
     According to the present invention, there is provided a substrate treatment method, which includes: a treatment liquid supplying step of supplying a treatment liquid to a major surface of a substrate; a substrate rotating step of rotating the substrate while retaining a liquid film of the treatment liquid on the major surface of the substrate; a heater heating step of locating a heater in opposed relation to the major surface of the substrate to heat the treatment liquid film by the heater in the substrate rotating step; and a heat amount controlling step of controlling the amount of heat to be applied per unit time to a predetermined portion of the liquid film from the heater according to the rotation speed of the substrate in the heater heating step. 
     In this method, the heat is applied to the predetermined portion of the liquid film retained on the major surface of the substrate from the heater, and the heat amount per unit time is controlled according to the rotation speed of the substrate. The thickness of the liquid film present on the major surface of the substrate varies depending on the rotation speed of the substrate. Therefore, the amount of the heat to be applied per unit time to the predetermined portion of the liquid film from the heater can be adapted for the thickness of the liquid film. Thus, even if the thickness of the liquid film present on the major surface of the substrate varies due to a change in the rotation speed of the substrate, overheating of the major surface of the substrate and insufficient heating of the treatment liquid are prevented. As a result, the major surface of the substrate can be advantageously treated with the use of the heater without any damage thereto. 
     According to one embodiment of the present invention, the heat amount controlling step includes a heater output controlling step of controlling the output of the heater according to the rotation speed of the substrate. 
     In this method, the output of the heater is controlled according to the rotation speed of the substrate. Therefore, the output of the heater can be adapted for the thickness of the liquid film present on the major surface of the substrate. Therefore, even if the thickness of the treatment liquid film varies due to the change in the rotation speed of the substrate, the overheating of the major surface of the substrate and the insufficient heating of the treatment liquid are prevented. As a result, the major surface of the substrate can be advantageously treated with the use of the heater without any damage thereto. 
     The substrate treatment method may further include a heater moving step of moving the heater along the major surface of the substrate, and the heat amount controlling step may include a heater moving speed controlling step of controlling the moving speed of the heater according to the rotation speed of the substrate. 
     In this method, the heater is moved along the major surface of the substrate in the heater moving step. The heater moving speed is controlled according to the rotation speed of the substrate. Therefore, the heater moving speed can be adapted for the thickness of the liquid film present on the major surface of the substrate. The amount of the heat to be applied to the predetermined portion of the liquid film can be relatively reduced by increasing the heater moving speed, and relatively increased by reducing the heater moving speed. Therefore, even if the thickness of the treatment liquid film varies due to the change in the rotation speed of the substrate, local overheating of the major surface of the substrate and the insufficient heating of the treatment liquid are prevented. As a result, the major surface of the substrate can be advantageously treated with the use of the heater without any damage thereto. 
     The heat amount controlling step may include the step of determining the heat amount per unit time based on a relational table indicating a relationship between the rotation speed of the substrate and the amount of the heat to be applied per unit time from the heater. 
     In this method, the heat amount per unit time is determined based on the relational table indicating the relationship between the rotation speed of the substrate and the amount of the heat to be applied per unit time from the heater. Since the relationship between the rotation speed of the substrate and the amount of the heat to be applied per unit time from the heater is preliminarily specified in the relational table, the heat amount suitable for the rotation speed of the substrate can be applied to the liquid film present on the major surface of the substrate. 
     The heat amount controlling step may include the step of referring to a recipe stored in a recipe storing unit and determining the heat amount per unit time based on a rotation speed of the substrate specified in the recipe to be employed in the substrate rotating step. 
     In this method, the heat amount per unit time is determined based on information of the substrate rotation speed contained in the recipe for a substrate treatment process in the heat amount controlling step. Therefore, the heat amount suitable for the rotation speed of the substrate can be applied to the liquid film present on the major surface of the substrate. 
     The treatment liquid may include a resist lift-off liquid containing sulfuric acid. 
     In this method, where a resist is provided on the major surface of the substrate, a liquid including the resist lift-off liquid containing sulfuric acid is used as the treatment liquid. In this case, the resist lift-off liquid containing sulfuric acid can be heated to a higher temperature on the major surface of the substrate by the heater. Thus, even if the resist has a hardened surface layer, the resist can be removed from the major surface of the substrate without ashing thereof. 
     The amount of the heat to be applied per unit time to the predetermined portion of the liquid film of the resist lift-off liquid can be adapted for the thickness of the liquid film. Therefore, even if the thickness of the resist lift-off liquid film varies due to the change in the rotation speed of the substrate, the overheating of the major surface of the substrate and the insufficient heating of the treatment liquid are prevented. As a result, the resist can be efficiently lifted off from the major surface of the substrate without damaging the major surface of the substrate. 
     The treatment liquid may include a chemical liquid containing an ammonia water. 
     According to the present invention, there is also provided a substrate treatment apparatus, which includes: a substrate holding unit which holds a substrate; a substrate rotating unit which rotates the substrate held by the substrate holding unit; a treatment liquid supplying unit which supplies a treatment liquid to a major surface of the substrate held by the substrate holding unit; a heater to be located in opposed relation to the major surface of the substrate; and a control unit which controls the substrate rotating unit and the heater to perform a substrate rotating step of rotating the substrate while retaining a liquid film of the treatment liquid on the major surface of the substrate, a heater heating step of heating the treatment liquid film by the heater in the substrate rotating step, and a heat amount controlling step of controlling the amount of heat to be applied per unit time to a predetermined portion of the liquid film from the heater according to the rotation speed of the substrate in the heater heating step. 
     With this arrangement, the heat is applied to the predetermined portion of the liquid film retained on the major surface of the substrate from the heater. The heat amount per unit time is controlled according to the rotation speed of the substrate. The thickness of the liquid film present on the major surface of the substrate varies depending on the rotation speed of the substrate. Therefore, the amount of the heat to be applied per unit time to the predetermined portion of the liquid film can be adapted for the thickness of the liquid film. Thus, even if the thickness of the liquid film present on the major surface of the substrate varies due to a change in the rotation speed of the substrate, overheating of the major surface of the substrate and insufficient heating of the treatment liquid are prevented. As a result, the major surface of the substrate can be advantageously treated with the use of the heater without any damage thereto. 
     The foregoing and other objects, features and effects of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a schematic plan view showing the schematic construction of a substrate treatment apparatus according to a first embodiment of the present invention. 
         FIG. 1B  is a diagram schematically showing the construction of a treatment unit of the substrate treatment apparatus. 
         FIG. 2  is a schematic sectional view of a heater shown in  FIG. 1B . 
         FIG. 3  is a perspective view of an infrared lamp shown in  FIG. 2 . 
         FIG. 4  is a perspective view of a heater arm and the heater shown in  FIG. 1B . 
         FIG. 5  is a plan view showing the positions of the heater. 
         FIG. 6  is a block diagram showing the electrical construction of the substrate treatment apparatus. 
         FIG. 7  is a flow chart showing a first exemplary resist removing process according to the first embodiment of the present invention. 
         FIG. 8  is a time chart for explaining major steps of the exemplary process shown in  FIG. 7 . 
         FIGS. 9A to 9C  are schematic diagrams for explaining process steps of the first exemplary process. 
         FIG. 10  is a flow chart showing how to control power supply to the heater. 
         FIG. 11  is a time chart for explaining an SC1 supplying/heater heating step of the first exemplary process. 
         FIG. 12  is a time chart showing a second exemplary resist removing process according to the first embodiment of the present invention. 
         FIG. 13  is a block diagram showing the electrical construction of a substrate treatment apparatus according to a second embodiment of the present invention. 
         FIG. 14  is a flowchart showing a third exemplary resist removing process according to the second embodiment of the present invention. 
         FIG. 15  is a time chart for explaining an SPM liquid film forming step and an SPM liquid film heating step of the third exemplary process. 
         FIG. 16  is a flow chart showing how to control a heater moving speed. 
         FIG. 17  is a time chart for explaining an SC1 supplying/heater heating step of the third exemplary process. 
         FIG. 18  is a time chart showing a fourth exemplary resist removing process according to the second embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1A  is a schematic plan view showing the schematic construction of a substrate treatment apparatus  1  according to a first embodiment of the present invention. As shown in  FIG. 1A , the substrate treatment apparatus  1  is of a single substrate treatment type to be used for removing an unnecessary resist from a front surface (major surface) of a wafer W (exemplary substrate) after being subjected to an ion implantation process for implanting an impurity into the front surface of the wafer W or a dry etching process. 
     The substrate treatment apparatus  1  includes a load port LP serving as a container retaining unit which retains a plurality of carriers C (containers), and a plurality of treatment units  100  (12 treatment units  100  in this embodiment) which each treat a wafer W with a treatment liquid. The treatment units  100  are disposed in vertically stacked relation. 
     The substrate treatment apparatus  1  further includes an indexer robot IR (transport robot) which transports a wafer W between the load port LP and a center robot CR, the center robot CR (transport robot) which transports a wafer W between the indexer robot IR and the treatment units  100 , and a computer  55  (control unit) which controls the operations of devices provided in the substrate treatment apparatus  1  and the opening and closing of valves. 
     As shown in  FIG. 1A , the load port LP is horizontally spaced from the treatment units  100 . The carriers C, which are each adapted to contain a plurality of wafers W, are arranged in a horizontal arrangement direction D as seen in plan. The indexer robot IR transports the wafers W one by one from the carriers C to the center robot CR, and transports the wafers W one by one from the center robot CR to the carriers C. Similarly, the center robot CR transports the wafers W one by one from the indexer robot IR to the treatment units  100 . Further, the center robot CR transports a wafer W between the treatment units  100  as required. 
     The indexer robot IR includes two hands H each having a U-shape as seen in plan. The two hands H are disposed at different height levels. The hands H each horizontally hold a wafer W. The indexer robot IR moves its hands H horizontally and vertically. The indexer robot IR rotates (turns) about its vertical axis to change the orientations of the hands H. The indexer robot IR is movable in the arrangement direction D along a path extending through a transfer position (a position shown in  FIG. 1A ). The transfer position is such that the indexer robot IR and the center robot CR are opposed to each other perpendicularly to the arrangement direction D as seen in plan. The indexer robot IR locates its hands H in opposed relation to a desired one of the carriers C or the center robot CR. The indexer robot IR moves its hands H to perform a loading operation to load a wafer W to any of the carriers C and perform an unloading operation to unload a wafer W from any of the carriers C. The indexer robot IR cooperates with the center robot CR to perform a transfer operation at the transfer position to transfer a wafer W from one of the indexer robot IR and the center robot CR to the other robot. 
     Similarly to the indexer robot IR, the center robot CR includes two hands H each having a U-shape as seen in plan. The two hands H are disposed at different height levels. The hands H each horizontally hold a wafer W. The center robot CR moves its hands H horizontally and vertically. The center robot CR rotates (turns) about its vertical axis to change the orientations of the hands H. The center robot CR is surrounded by the treatment units as seen in plan. The center robot CR locates its hands H in opposed relation to a desired one of the treatment units  100  or the indexer robot IR. The center robot CR moves its hands H to perform a loading operation to load a wafer W to any of the treatment units  100  and perform an unloading operation to unload a wafer W from any of the treatment units  100 . The center robot CR cooperates with the indexer robot IR to perform a transfer operation to transfer a wafer W from one of the indexer robot IR and the center robot CR to the other robot. 
       FIG. 1B  is a diagram schematically showing the construction of each of the treatment units  100  which perform a substrate treatment method according to the first embodiment of the present invention. 
     The treatment units  100  each include a treatment chamber  2  defined by a partition wall (see  FIG. 1A ), a wafer holding mechanism  3  (substrate holding unit) which holds a wafer W, a lift-off liquid nozzle  4  which supplies an SPM liquid (exemplary resist lift-off liquid) to a front surface (upper surface) of the wafer W held by the wafer holding mechanism  3 , and a heater  54  which is located in opposed relation to the front surface of the wafer W held by the wafer holding mechanism  3  to heat the wafer W and a liquid film of the treatment liquid (the SPM liquid or SC1 to be described later) retained on the wafer W. The wafer holding mechanism  3 , the lift-off liquid nozzle  4  and the heater  54  are disposed in the treatment chamber  2 . 
     The wafer holding mechanism  3  is, for example, of a clamping type. More specifically, the wafer holding mechanism  3  includes a rotative drive mechanism (substrate rotating unit), a spin shaft  7  integral with a drive shaft of the rotative drive mechanism  6 , a disk-shaped spin base  8  generally horizontally attached to an upper end of the spin shaft  7 , and a plurality of clamping members  9  provided generally equiangularly circumferentially of the spin base  8 . The rotative drive mechanism  6  is, for example, an electric motor. The clamping members  9  generally horizontally clamp the wafer W. When the rotative drive mechanism  6  is driven in this state, the spin base  8  is rotated about a predetermined vertical rotation axis A1 by the driving force of the rotative drive mechanism  6 . Thus, the wafer W is rotated about the rotation axis A1 together with the spin base  8  while being generally horizontally held. 
     The wafer holding mechanism  3  is not limited to the clamping type, but may be, for example, of a vacuum suction type, which sucks a back surface of the wafer W by vacuum to horizontally hold the wafer W and, in this state, is rotated about the rotation axis A1 to rotate the wafer W thus held. 
     The lift-off liquid nozzle  4  is, for example, a straight nozzle which spouts the SPM liquid in the form of a continuous stream. The lift-off liquid nozzle  4  is attached to a distal end of a generally horizontally extending first liquid arm  11  with its spout directed downward. The first liquid arm  11  is pivotal about a predetermined vertical pivot axis (not shown). A first liquid arm pivot mechanism  12  for pivoting the first liquid arm  11  within a predetermined angular range is connected to the first liquid arm  11 . The lift-off liquid nozzle  4  is moved between a position on the rotation axis A1 of the wafer W (at which the lift-off liquid nozzle  4  is opposed to the rotation center of the wafer W) and a home position defined on a lateral side of the wafer holding mechanism  3  by pivoting the first liquid arm  11 . 
     A lift-off liquid supply mechanism  13  (treatment liquid supplying unit) for supplying the SPM liquid to the lift-off liquid nozzle  4  includes a mixing portion  14  for mixing sulfuric acid (H 2 SO 4 ) and hydrogen peroxide solution (H 2 O 2 ), and a lift-off liquid supply line  15  connected between the mixing portion  14  and the lift-off liquid nozzle  4 . A sulfuric acid supply line  16  and a hydrogen peroxide solution supply line  17  are connected to the mixing portion  14 . Sulfuric acid temperature-controlled at a predetermined temperature (e.g., about 80° C.) is supplied to the sulfuric acid supply line  16  from a sulfuric acid supply portion (not shown) to be described later. On the other hand, a hydrogen peroxide solution not temperature-controlled but having a temperature generally equal to a room temperature (about 25° C.) is supplied to the hydrogen peroxide solution supply line  17  from a hydrogen peroxide solution supply source (not shown). 
     A sulfuric acid valve  18  and a flow rate control valve  19  are provided in the sulfuric acid supply line  16 . Further, a hydrogen peroxide solution valve  20  and a flow rate control valve  21  are provided in the hydrogen peroxide solution supply line  17 . In the lift-off liquid supply line  15 , an agitation flow pipe  22  and a lift-off liquid vale  23  are provided in this order from the side of the mixing portion  14 . The agitation flow pipe  22  is configured such that a plurality of rectangular planar agitation fins each twisted by about 180 degrees about an axis extending in a liquid flowing direction are provided in a tubular member so as to be angularly offset from each other by 90 degrees about a center axis of the tubular member extending in the liquid flowing direction. 
     When the sulfuric acid valve  18  and the hydrogen peroxide solution valve  20  are opened with the lift-off liquid valve  23  being open, sulfuric acid from the sulfuric acid supply line  16  and the hydrogen peroxide solution from the hydrogen peroxide solution supply line  17  flow into the mixing portion  14 , and then flow out of the mixing portion  14  into the lift-off liquid supply line  15 . Sulfuric acid and the hydrogen peroxide solution flow through the agitation flow pipe  22  to be thereby sufficiently agitated when flowing through the lift-off liquid supply line  15 . With the agitation in the agitation flow pipe  22 , sulfuric acid and the hydrogen peroxide solution sufficiently react with each other, whereby an SPM liquid containing a great amount of peroxosulfuric acid (H 2 SO 5 ) is prepared. The temperature of the SPM liquid is increased to a temperature level higher than the liquid temperature of sulfuric acid supplied to the mixing portion  14  by reaction heat generated by the reaction between sulfuric acid and the hydrogen peroxide solution. The SPM liquid having a higher temperature is supplied to the lift-off liquid nozzle  4  through the lift-off liquid supply line  15 . 
     In this embodiment, sulfuric acid is stored in a sulfuric acid tank (not shown) of the sulfuric acid supply portion (not shown). Sulfuric acid stored in the sulfuric acid tank is temperature-controlled at a predetermined temperature (e.g., about 80° C.) by a temperature controller (not shown). Sulfuric acid stored in the sulfuric acid tank is supplied to the sulfuric acid supply line  16 . In the mixing portion  14 , sulfuric acid having a temperature of about 80° C., for example, is mixed with the hydrogen peroxide solution kept at a room temperature, whereby an SPM liquid having a temperature of about 140° C., for example, is prepared. The SPM liquid having a temperature of about 140° C. is spouted from the lift-off liquid nozzle  4 . 
     The treatment units  100  each further include a DIW nozzle  24  from which DIW (deionized water) is supplied as a rinse liquid onto the front surface of the wafer W held by the wafer holding mechanism  3 , and an SC1 nozzle  25  from which SC1 (an ammonia-hydrogen peroxide mixture) is supplied as a cleaning chemical liquid onto the front surface of the wafer W held by the wafer holding mechanism  3 . 
     The DIW nozzle  24  is a straight nozzle which spouts the DIW, for example, in the form of a continuous stream, and is fixedly disposed above the wafer holding mechanism  3  with its spout directed toward around the rotation center of the wafer W. The DIW nozzle  24  is connected to a DIW supply line  26  to which the DIW is supplied from a DIN supply source. A DIW valve  27  for switching on and off the supply of the DIW from the DIW nozzle  24  is provided in the DIW supply line  26 . 
     The SC1 nozzle  25  is a straight nozzle which spouts the SC1, for example, in the form of a continuous stream, and is fixed to a distal end of a generally horizontally extending second liquid arm  28  with its spout directed downward. The second liquid arm  28  is pivotal about a predetermined vertical pivot axis (not shown). A second liquid arm pivot mechanism  29  for pivoting the second liquid arm  28  within a predetermined angular range is connected to the second liquid arm  28 . The SC1 nozzle  25  is moved between a center position on the rotation axis A1 of the wafer W (at which the SC1 nozzle  25  is opposed to the rotation center of the wafer W) and a home position defined on a lateral side of the wafer holding mechanism  3  by pivoting the second liquid arm  28 . 
     The SC1 nozzle  25  is connected to an SC1 supply line  30  to which the SC1 is supplied from an SC1 supply source. An SC1 valve  31  for switching on and off the supply of the SC1 from the SC1 nozzle  25  is provided in the SC1 supply line  30 . 
     A vertically extending support shaft  33  is disposed on a lateral side of the wafer holding mechanism  3 . A horizontally extending heater arm  34  is connected to an upper end of the support shaft  33 , and the heater  54  is attached to a distal end of the heater arm  34 . A pivot drive mechanism  36  which rotates the support shaft  33  about its center axis and a lift drive mechanism  37  which moves up and down the support shaft  33  along its center axis are connected to the support shaft  33 . 
     A driving force is inputted to the support shaft  33  from the pivot drive mechanism  36  to rotate the support shaft  33  within a predetermined angular range, whereby the heater arm  34  is pivoted about the support shaft  33  above the wafer W held by the wafer holding mechanism  3 . By pivoting the heater arm  34 , the heater  54  is moved between a position on the rotation axis A1 of the wafer W (at which the heater  54  is opposed to the rotation center of the wafer W) and a home position defined on a lateral side of the wafer holding mechanism  3 . Further, a driving force is inputted to the support shaft  33  from the lift drive mechanism  37  to move up and down the support shaft  33 , whereby the heater  54  is moved up and down between a position adjacent to the front surface of the wafer W held by the wafer holding mechanism  3  (a height position indicated by a two-dot-and-dash line in  FIG. 1B , and including a middle adjacent position, an edge adjacent position and a center adjacent position to be described later) and a retracted position above the wafer W (a height position indicated by a solid line in  FIG. 1B ). In this embodiment, the adjacent position is defined so that a lower end face of the heater  54  is spaced a distance of, for example, 3 mm from the front surface of the wafer W held by the wafer holding mechanism  3 . 
       FIG. 2  is a schematic sectional view of the heater  54 .  FIG. 3  is a perspective view of an infrared lamp  38 .  FIG. 4  is a perspective view of the heater arm  34  and the heater  54 . 
     As shown in  FIG. 2 , the heater  54  includes a heater head  35 , an infrared lamp  38 , a lamp housing  40  which is a bottomed container having a top opening  39  and accommodating the infrared lamp  38 , a support member  42  which supports the infrared lamp  38  while suspending the infrared lamp  38  in the lamp housing  40 , and a lid  41  which closes the opening  39  of the lamp housing  40 . In this embodiment, the lid  41  is fixed to the distal end of the heater arm  34 . 
     As shown in  FIGS. 2 and 3 , the infrared lamp  38  is a unitary infrared lamp heater which includes an annular portion  43  having an annular shape, and a pair of straight portions  44 ,  45  extending vertically upward from opposite ends of the annular portion  43  along a center axis of the annular portion  43 . The annular portion  43  mainly functions as a light emitting portion which emits infrared radiation. In this embodiment, the annular portion  43  has an outer diameter of, for example, about 60 mm. With the infrared lamp  38  supported by the support member  42 , the center axis of the annular portion  43  vertically extends. In other words, the center axis of the annular portion  43  is perpendicular to the front surface of the wafer W held by the wafer holding mechanism  3 . The annular portion  43  of the infrared lamp  38  is disposed in a generally horizontal plane. 
     The infrared lamp  38  includes a quartz tube, and a filament accommodated in the quartz tube. Typical examples of the infrared lamp  38  include infrared heaters of shorter wavelength, intermediate wavelength and longer wavelength such as halogen lamps and carbon lamps. The computer  55  is connected to the infrared lamp  38  for power supply to the infrared lamp  38 . 
     As shown in  FIGS. 2 and 4 , the lid  41  has a disk shape, and is fixed to the heater arm  34  as extending longitudinally of the heater arm  34 . The lid  41  is formed of a fluororesin such as PTFE (polytetrafluoroethylene). In this embodiment, the lid  41  is formed integrally with the heater arm  34 . However, the lid  41  may be formed separately from the heater arm  34 . Exemplary materials for the lid  41  other than the resin material such as PTFE include ceramic materials and quartz. 
     As shown in  FIG. 2 , the lid  41  has a groove  51  (having a generally cylindrical shape) formed in a lower surface  49  thereof. The groove  51  has a horizontal flat upper base surface  50 , and an upper surface  42 A of the support member  42  is fixed to the upper base surface  50  in contact with the upper base surface  50 . As shown in  FIGS. 2 and 4 , the lid  41  has insertion holes  58 ,  59  extending vertically through the upper base surface  50  and a lower surface  42 B. Upper end portions of the straight portions  44 ,  45  of the infrared lamp  38  are respectively inserted in the insertion holes  58 ,  59 . In  FIG. 4 , the heater head  35  is illustrated with the infrared lamp  38  removed therefrom. 
     As shown in  FIG. 2 , the lamp housing  40  of the heater head  35  is a bottomed cylindrical container. The lamp housing  40  is formed of quartz. 
     In the heater head  35 , the lamp housing  40  is fixed to the lower surface  49  of the lid  41  (fixed to a portion of the lower surface  49  of the lid  41  not formed with the groove  51  in this embodiment) with its opening  39  facing up. An annular flange  40 A projects radially outward (horizontally) from a peripheral edge of the opening of the lamp housing  40 . The flange  40 A is fixed to the lower surface  49  of the lid  41  with a fixture portion such as bolts (not shown), whereby the lamp housing  40  is supported by the lid  41 . 
     A bottom plate  52  of the lamp housing  40  has a horizontal disk shape. The bottom plate  52  has an upper surface  52 A and a lower surface  52 B which are horizontal flat surfaces. In the lamp housing  40 , a lower portion of the annular portion  43  of the infrared lamp  38  is located in closely opposed relation to the upper surface  52 A of the bottom plate  52 . The annular portion  43  and the bottom plate  52  are parallel to each other. In other words, the lower portion of the annular portion  43  is covered with the bottom plate  52  of the lamp housing  40 . In this embodiment, the lamp housing  40  has an outer diameter of, for example, about 85 mm. Further, a vertical distance between a lower end of the infrared lamp  38  (a lower portion of the annular portion  43 ) and the upper surface  52 A is, for example, about 2 mm. 
     The support member  42  is a thick plate having a generally disk shape. The support member  42  is horizontally attached and fixed to the lid  41  from below by bolts  56  or the like. The support member  42  is formed of a heat-resistant material (e.g., a ceramic or quartz). The support member  42  has two insertion holes  46 ,  47  extending vertically through the upper surface  42 A and the lower surface  42 B thereof. The straight portions  44 ,  45  of the infrared lamp  38  are respectively inserted in the insertion holes  46 ,  47 . 
     O-rings are respectively fixedly fitted around intermediate portions of the straight portions  44 ,  45 . With the straight portions  44 ,  45  respectively inserted in the insertion holes  46 ,  47 , outer peripheries of the O-rings  48  are kept in press contact with inner walls of the corresponding insertion holes  46 ,  47 . Thus, the straight portions  44 ,  45  are prevented from being withdrawn from the insertion holes  46 ,  47 , whereby the infrared lamp  38  is suspended to be supported by the support member  42 . 
     The emission of the infrared radiation from the heater  54  is controlled by the computer  55  (specifically, a CPU  55 A to be described later). More specifically, when the computer  55  controls the heater  54  to supply electric power to the infrared lamp  38 , the infrared lamp  38  starts emitting infrared radiation. The infrared radiation emitted from the infrared lamp  38  is outputted through the lamp housing  40  downward of the heater head  35 . In a resist removing process to be described later, the bottom plate  52  of the lamp housing  40  which defines the lower end face of the heater head  35  is located in opposed relation to the front surface of the wafer W held by the wafer holding mechanism  3  and, in this state, the infrared radiation outputted through the bottom plate  52  of the lamp housing  40  heats the wafer W and the treatment liquid film (the SPM liquid film or the SC1 liquid film) present on the wafer W. Since the annular portion  43  of the infrared lamp  38  assumes a horizontal attitude, the infrared radiation can be evenly applied onto the front surface of the wafer W horizontally held. Thus, the wafer W and the treatment liquid present on the wafer W can be efficiently irradiated with the infrared radiation. 
     In the heater head  35 , the periphery of the infrared lamp  38  is covered with the lamp housing  40 . Further, the flange  40 A of the lamp housing  40  and the lower surface  49  of the lid  41  are kept in intimate contact with each other circumferentially of the lamp housing  40 . Further, the opening  39  of the lamp housing  40  is closed by the lid  41 . Thus, an atmosphere containing droplets of the treatment liquid around the front surface of the wafer W is prevented from entering the lamp housing  40  and adversely influencing the infrared lamp  38  in the resist removing process to be described later. Further, the treatment liquid droplets are prevented from adhering onto the quartz tube wall of the infrared lamp  38 , so that the amount of the infrared radiation emitted from the infrared lamp  38  can be stabilized for a longer period of time. 
     The lid  41  includes a gas supply passage  60  through which air is supplied into the lamp housing  40 , and an evacuation passage  61  through which an internal atmosphere of the lamp housing  40  is expelled. The gas supply passage  60  and the evacuation passage  61  respectively have a gas supply port  62  and an evacuation port  63  which are open in the lower surface of the lid  41 . The gas supply passage  60  is connected to one of opposite ends of a gas supply pipe  64 . The other end of the gas supply pipe  64  is connected to an air supply source. The evacuation passage  61  is connected to one of opposite ends of an evacuation pipe  65 . The other end of the evacuation pipe  65  is connected to an evacuation source. 
     While air is supplied into the lamp housing  40  from the gas supply port  62  through the gas supply pipe  64  and the gas supply passage  60 , the internal atmosphere of the lamp housing  40  is expelled to the evacuation pipe  65  through the evacuation port  63  and the evacuation passage  61 . Thus, a higher-temperature atmosphere in the lamp housing  40  can be expelled for ventilation. Thus, the inside of the lamp housing  40  can be cooled. As a result, the infrared lamp  38  and the lamp housing  40 , particularly the support member  42 , can be advantageously cooled. 
     As shown in  FIG. 4 , the gas supply pipe  64  and the evacuation pipe  65  (not shown in  FIG. 4 , but see  FIG. 2 ) are respectively supported by a gas supply pipe holder  66  provided on the heater arm  34  and an evacuation pipe holder  67  provided on the heater arm  34 . 
       FIG. 5  is a plan view showing positions of the heater  54 . 
     The pivot drive mechanism  36  and the lift drive mechanism  37  are controlled to move the heater  54  along an arcuate path crossing a wafer rotating direction above the front surface of the wafer W. 
     When the wafer W and the SPM liquid or the SC1 present on the wafer W are heated by the heater  54 , the heater  54  is located at the adjacent position at which the bottom plate  52  (lower end face) of the heater head  35  is opposed to and spaced a minute distance (e.g., 3 mm) from the front surface of the wafer W. During the heating, the bottom plate  52  (lower surface  52 B) and the front surface of the wafer W are kept spaced the minute distance from each other. 
     Examples of the adjacent position of the heater  54  include a middle adjacent position (indicated by a solid line in  FIG. 5 ), an edge adjacent position (indicated by a two-dot-and-dash line in  FIG. 5 ) and a center adjacent position (indicated by a one-dot-and-dash line in  FIG. 5 ). 
     With the heater  54  located at the middle adjacent position, the center of the round heater  54  as seen in plan is opposed to a radially intermediate portion of the front surface of the wafer W (a portion intermediate between the rotation center (on the rotation axis A1) and a peripheral edge portion of the wafer W), and the bottom plate  52  of the heater head  35  is spaced the minute distance (e.g., 3 mm) from the front surface of the wafer W. 
     With the heater  54  located at the edge adjacent position, the center of the round heater  54  as seen in plan is opposed to the peripheral edge portion of the front surface of the wafer W, and the bottom plate  52  of the heater head  35  is spaced the minute distance (e.g., 3 mm) from the front surface of the wafer W. 
     With the heater  54  located at the center adjacent position, the center of the round heater  54  as seen in plan is opposed to the rotation center (on the rotation axis A1) of the front surface of the wafer W, and the bottom plate  52  of the heater head  35  is spaced the minute distance (e.g., 3 mm) from the front surface of the wafer W. 
       FIG. 6  is a block diagram showing the electrical construction of the substrate treatment apparatus  1 . 
     The substrate treatment apparatus  1  includes the computer  55 . The computer  55  includes the CPU  55 A, and a storage  55 D (recipe storing unit). The storage  55 D stores a recipe  55 B, a rotation speed/heater output relational table  55 C for the SPM liquid, and a rotation speed/heater output relational table  55 F for the SC1. 
     Exemplary data stored in the storage  55 D include data for a process recipe (recipe  55 B) which specifies treatments to be performed on the wafer W (procedures, conditions and the like), and relational tables indicating relationships between the rotation speed of the wafer W and the output of the heater  54  (the rotation speed/heater output relational table  55 C for the SPM liquid and the rotation speed/heater output relational table  55 F for the SC1). 
     The rotation speed/heater output relational table  55 C for the SPM liquid specifies a relationship between the rotation speed of the wafer W and the output of the heater  54  such that, during the supply of the SPM liquid, the output of the heater  54  is reduced as the rotation speed of the wafer W increases. More specifically, the rotation speed/heater output relational table  55 C for the SPM liquid specifies a relationship between the rotation speed of the wafer W and the output of the heater  54  such that sufficient heat can reach a portion of the SPM liquid film present around an interface between the front surface of the wafer W and the SPM liquid film without damaging the front surface of the wafer W. The thickness of the liquid film of the SPM liquid supplied to the front surface of the wafer W is dependent on the rotation speed of the wafer W. The higher the rotation speed of the wafer W, the smaller the thickness of the SPM liquid film. The lower the rotation speed of the wafer W, the greater the thickness of the SPM liquid film. Where the relationship between the rotation speed of the wafer W and the output of the heater  54  is specified by the rotation speed/heater output relational table  55 C for the SPM liquid, therefore, sufficient heat can reach the SPM liquid portion present around the interface between the front surface of the wafer W and the SPM liquid film without damaging the front surface of the wafer W. 
     Similarly, the rotation speed/heater output relational table  55 F for the SC1 specifies a relationship between the rotation speed of the wafer W and the output of the heater  54  such that, during the supply of the SC1, the output of the heater  54  is reduced as the rotation speed of the wafer W increases. More specifically, the rotation speed/heater output relational table  55 F for the SC1 specifies a relationship between the rotation speed of the wafer W and the output of the heater  54  such that sufficient heat can reach a portion of the SC1 liquid film present around an interface between the front surface of the wafer W and the SC1 liquid film without damaging the front surface of the wafer W. The thickness of the liquid film of the SC1 supplied to the front surface of the wafer W is dependent on the rotation speed of the wafer W. The higher the rotation speed of the wafer W, the smaller the thickness of the SC1 liquid film. The lower the rotation speed of the wafer W, the greater the thickness of the SC1 liquid film. Where the relationship between the rotation speed of the wafer W and the output of the heater  54  is specified by the rotation speed/heater output relational table  55 F for the SC1, therefore, sufficient heat can reach the SC1 liquid film portion present around the interface between the front surface of the wafer W and the SC1 liquid film without damaging the front surface of the wafer W. 
     The computer  55  is connected to the rotative drive mechanism  6 , the heater  54 , the pivot drive mechanism  36 , the lift drive mechanism  37 , the first liquid arm pivot mechanism  12 , the second liquid arm pivot mechanism  29 , the sulfuric acid valve  18 , the hydrogen peroxide solution valve  20 , the lift-off liquid valve  23 , the DIW valve  27 , the SC1 valve  31 , the flow rate control valves  19 ,  21 , and the like, which are controlled by the computer  55 . 
     A recipe inputting portion  57  includes a keyboard, a touch panel and other input interfaces which are operated by a user. The user can read the data out of the storage  55 D by operating the recipe operating portion  57 . Further, the user can make a recipe by using the recipe inputting portion  57  and store the recipe as a recipe  55 B in the storage  55 D. 
       FIG. 7  is a flow chart showing a first exemplary resist removing process according to the first embodiment of the present invention.  FIG. 8  is a time chart for explaining a control operation to be performed by the CPU  55 A mainly in an SPM liquid film forming step and an SPM liquid film heating step to be described later.  FIGS. 9A to 9C  are schematic diagrams for explaining the SPM liquid film forming step and the SPM liquid film heating step.  FIG. 10  is a flow chart showing a control operation to be performed for the power supply to the heater  54 .  FIG. 11  is a time chart for explaining an SC1 supplying/heater heating step of the first exemplary process. 
     Referring to  FIGS. 1A and 1B  and  FIGS. 6 to 11 , the first exemplary resist removing process will hereinafter be described. 
     Prior to the resist removing process, the user operates the recipe inputting portion  57  to determine the recipe  55 B to specify conditions for the treatment of the wafer W. Subsequently, the CPU  55 A performs a process sequence for the treatment of the wafer W based on the recipe  55 B. 
     The CPU  55 A controls the indexer robot IR (see  FIG. 1A ) and the center robot CR (see  FIG. 1A ) to load a wafer W subjected to the ion implantation process into a treatment chamber  2  (Step S 1 : Wafer loading step). The wafer W is not subjected to the resist ashing process. The wafer W is transferred to the wafer holding mechanism  3  with its front surface facing up. At this time, the heater  54 , the lift-off liquid nozzle  4  and the SC1 nozzle  25  are respectively located at their home positions so as not to prevent the loading of the wafer W. 
     With the wafer W held by the wafer holding mechanism  3 , the CPU  55 A controls the rotative drive mechanism  6  to start rotating the wafer W (Step S 2 ). The rotation speed of the wafer W is increased to a predetermined first rotation speed, and then maintained at the first rotation speed. The first rotation speed is such that the entire front surface of the wafer W can be covered with the SPM liquid, and may be, for example, 150 rpm. The CPU  55 A controls the first liquid arm pivot mechanism  12  to move the lift-off liquid nozzle  4  to above the wafer W and locate the lift-off liquid nozzle  4  above the rotation center of the wafer W (on the rotation axis A1). Further, the CPU  55 A opens the sulfuric acid valve  18 , the hydrogen peroxide solution valve  20  and the lift-off liquid valve  23  to spout the SPM liquid from the lift-off liquid nozzle  4 . The SPM liquid spouted from the lift-off liquid nozzle  4  is supplied to the front surface of the wafer W as shown in  FIGS. 8 and 9A  (Step S 31 : SPM liquid film forming step). 
     The SPM liquid supplied to the front surface of the wafer W spreads from a center portion of the front surface of the wafer W to a peripheral portion of the front surface of the wafer W by a centrifugal force generated by the rotation of the wafer W. Thus, the SPM liquid spreads over the entire front surface of the wafer W to form a liquid film  70  of the SPM liquid which covers the entire front surface of the wafer W. The SPM liquid film  70  has a thickness of, for example, 0.4 mm. 
     The CPU  55 A controls the pivot drive mechanism  36  and the lift drive mechanism  37  to move the heater  54  to above the edge adjacent position (indicated by the two-dot-and-dash line in  FIG. 5 ) from the home position defined on the lateral side of the wafer holding mechanism  3  and then down to the edge adjacent position, and further move the heater  54  at a constant speed toward the center adjacent position (indicated by the one-dot-and-dash line in  FIG. 5 ). 
     The SPM liquid film forming step of Step S 31  and an SPM liquid film heating step of Step S 32  to be described below are collectively referred to as an SPM supplying/heater heating step (Step S 3 ). Throughout the SPM supplying/heater heating step of Step S 3 , the heater  54  emits infrared radiation, and the output of the heater  54  is determined so as to be adapted for the rotation speed of the wafer W. 
     In the SPM liquid film forming step of Step S 31 , as shown in  FIG. 10 , the CPU  55 A judges if the heater  54  is currently in an ON period, with reference to a timer (not shown) for monitoring the progression status of the resist removing process (Step S 21 ). 
     If the heater  54  is in the ON period (YES in Step S 21 ), the CPU  55 A determines the level of electric power to be supplied to the heater  54  based on the rotation speed of the wafer W stored in the recipe  55 B and the rotation speed/heater output relational table  55 C for the SPM liquid (Step S 22 ). Then, the electric power is supplied at the level thus determined to the heater  54 . The SPM liquid film present on the front surface of the wafer W is heated to a higher temperature by the infrared radiation emitted from the heater  54 . Thus, even a resist having a hardened surface layer can be removed from the front surface of the wafer W without ashing thereof. 
     If the heater  54  is not in the ON period (NO in Step S 21 ), on the other hand, the electric power is not supplied to the heater  54 . Thus, the output of the heater  54  is controlled to an output level suitable for the rotation speed of the wafer W stored in the recipe  55 B. At this time, the rotation speed of the wafer W is a relatively high first rotation speed in the SPM liquid film forming step of Step S 31 , so that a relatively thin SPM liquid film is formed on the front surface of the wafer W. Therefore, the CPU  55 A controls the output of the heater  54  to a relatively low first output level (e.g., about 40% of the maximum output level) based on the relationship between the rotation speed of the wafer W and the output of the heater  54  specified by the rotation speed/heater output relational table  55 C for the SPM liquid (see  FIG. 6 ). 
     The first output level is such that sufficient heat can reach a portion of the SPM liquid film  70  present around the interface between the front surface of the wafer W and the SPM liquid film without damaging the front surface of the wafer W. This prevents the overheating of the front surface of the wafer W and the insufficient heating of the SPM liquid film  70 . As a result, the resist can be efficiently lifted off from the front surface of the wafer W without damaging the front surface of the wafer W in the SPM liquid film forming step of Step S 31 . 
     After a lapse of a predetermined SPM liquid supply period from the start of the supply of the SPM liquid, the CPU  55 A controls the rotative drive mechanism  6  to reduce the rotation speed of the wafer W from the first rotation speed to a second rotation speed. The second rotation speed is, for example, such that an SPM liquid film  80  thicker than the SPM liquid film  70  can be retained on the front surface of the wafer W (a speed in a range of 1 rpm to 30 rpm, e.g., 15 rpm). The thickness of the SPM liquid film  80  is, for example, 1.0 mm. 
     After a lapse of another predetermined SPM liquid supply period from the start of the supply of the SPM liquid, the CPU  55 A closes the sulfuric acid valve  18 , the hydrogen peroxide solution valve  20  and the lift-off liquid valve  23  to stop supplying the SPM liquid from the lift-off liquid nozzle  4  as shown in  FIGS. 8 and 9B . Further, the CPU  55 A controls the first liquid arm pivot mechanism  12  to move the lift-off liquid nozzle  4  back to its home position after the stop of the supply of the SPM liquid. The SPM liquid supply periods should be each longer than a period required for forming the SPM liquid film  70 ,  80  to cover the entire front surface of the wafer W. The SPM liquid supply periods vary depending on the spouting flow rate of the SPM liquid spouted from the lift-off liquid nozzle  4  and the rotation speed (first rotation speed) of the wafer W, but may be in a range of 3 seconds to 30 seconds, e.g., 15 seconds. 
     The CPU  55 A continues the emission of the infrared radiation from the heater  54  (Step S 32 : SPM liquid film heating step). 
     In the SPM liquid film heating step of Step S 32 , the output level of the heater  54  is determined based on the rotation speed of the wafer W. As in the SPM liquid film forming step of Step S 31 , more specifically, the CPU  55 A determines the level of the electric power to be supplied to the heater  54  based on the rotation speed of the wafer W stored in the recipe  55 B and the rotation speed/heater output relational table  55 C for the SPM liquid (Step S 22  in  FIG. 10 ) in the ON period of the heater  54  (YES in Step S 21  in  FIG. 10 ). Then, the electric power is supplied at the output level thus determined to the heater  54 . As described above, the rotation speed/heater output relational table  55 C for the SPM liquid (see  FIG. 6 ) is defined such that the output of the heater  54  is reduced as the rotation speed of the wafer W increases. Therefore, the output of the heater  54  is controlled to a second output level (e.g., about 95% of the maximum output level) that is higher than the first output level. 
     The second output level is such that sufficient heat can reach a portion of the SPM liquid film  80  present around the interface between the front surface of the wafer W and the SPM liquid film without damaging the front surface of the wafer W. This prevents the overheating of the front surface of the wafer W and the insufficient heating of the SPM liquid film  80 . Therefore, the resist can be efficiently lifted off from the front surface of the wafer W without damaging the front surface of the wafer W in the SPM liquid film heating step of Step S 32 . 
     Immediately after the start of the SPM liquid film heating step of Step S 32 , the heater  54  is located around the middle adjacent position (indicated by the solid line in  FIG. 5 ) in this embodiment. The CPU  55 A continuously controls the pivot drive mechanism  36  to move the heater  54  at the predetermined moving speed from the middle adjacent position toward the center adjacent position (indicated by the one-dot-and-dash line in  FIG. 5 ). 
     After the heater  54  reaches the center adjacent position, the heating of the wafer W is continued at the center adjacent position for a predetermined period. In the SPM liquid film heating step of Step S 32 , a portion of the wafer W opposed to the bottom plate  52  of the heater head  35  and a portion of the SPM liquid film  80  present on that portion of the wafer W are heated by the infrared radiation emitted from the heater  54 . The SPM liquid film heating step of Step S 32  is performed for a predetermined heating period (in a range of 2 second to 90 seconds, e.g., about 40 seconds). 
     After a lapse of a predetermined period from the start of the emission of the infrared radiation from the heater  54 , the CPU  55 A controls the heater  54  to stop the emission of the infrared radiation. Further, the CPU  55 A controls the pivot drive mechanism  36  and the lift drive mechanism  37  to move the heater  54  back to its home position. 
     Then, the CPU  55 A controls the rotative drive mechanism  6  to increase the rotation speed of the wafer W to a predetermined third rotation speed (in a range of 300 rpm to 1500 rpm, e.g., 1000 rpm), and opens the DIW valve  27  to supply the DIW from the spout of the DIW nozzle  24  toward around the rotation center of the wafer W (Step S 4 : Intermediate rinsing step). 
     The DIW supplied onto the front surface of the wafer W receives a centrifugal force generated by the rotation of the wafer W to flow toward the peripheral edge of the wafer W on the front surface of the wafer W. Thus, SPM liquid adhering to the front surface of the wafer W is rinsed away with the DIW. After the supply of the DIW is continued for a predetermined period, the CPU  55 A closes the DIW valve  27  to stop supplying the DIW to the front surface of the wafer W. 
     While maintaining the rotation speed of the wafer W at the third rotation speed as shown in  FIG. 11 , the CPU  55 A opens the SC1 valve  31  to supply the SC1 from the SC1 nozzle  25  to the front surface of the wafer W (Step S 5 : SC1 supplying/heater heating step). The CPU  55 A controls the second liquid arm pivot mechanism  29  to pivot the second liquid arm  28  within the predetermined angular range to reciprocally move the SC1 nozzle  25  between a position above the rotation center of the wafer W and a position above the peripheral edge of the wafer W. Thus, an SC1 supply position on the front surface of the wafer W to which the SC1 is supplied from the SC1 nozzle  25  is reciprocally moved along an arcuate path crossing the wafer rotating direction in a range from the rotation center of the wafer W to the peripheral edge of the wafer W. Thus, the SC1 spreads over the entire front surface of the wafer W, whereby a thin liquid film of the SC1 is formed as covering the entire front surface of the wafer W. 
     The front surface of the wafer W and the SC1 liquid film are warmed by the heater  54  during the supply of the SC1 to the wafer W. More specifically, the CPU  55 A controls the heater  54  to start emitting the infrared radiation, and controls the pivot drive mechanism  36  and the lift drive mechanism  37  to move the heater  54  from the home position defined on the lateral side of the wafer holding mechanism  3  to above the edge adjacent position (indicated by the two-dot-and-dash line in  FIG. 5 ) and then down to the edge adjacent position, and move the heater  54  toward the center adjacent position (indicated by the one-dot-and-dash line in  FIG. 5 ) at a constant speed. 
     In the SC1 supplying/heater heating step of Step S 5 , the output level of the heater  54  is determined based on the rotation speed of the wafer W. As in the SPM supplying/heater heating step of Step S 3 , more specifically, the CPU  55 A determines the level of the electric power to be supplied to the heater  54  based on the rotation speed of the wafer W stored in the recipe  55 B and the rotation speed/heater output relational table  55 F for the SC1 (see Step S 22  in  FIG. 10 ) in the ON period of the heater  54 . Then, the electric power is supplied at the output level thus determined to the heater  54 . In the SC1 supplying/heater heating step of Step S 5 , the rotation speed of the wafer W is the relatively high third rotation speed, so that the output of the heater  54  is controlled to a relatively low third output level suitable for the third rotation speed. The third output level is such that sufficient heat can reach the SC1 liquid film portion present around the interface between the front surface of the wafer W and the SC1 liquid film without damaging the front surface of the wafer W in the SC1 supplying/heater heating step of Step S 5 . 
     In the SC1 supplying/heater heating step of Step S 5 , the method of scanning the SC1 nozzle  25  and the heater  54  is determined so as to prevent the SC1 nozzle  25  and the heater  54  from interfering with each other. 
     In the SC1 supplying/heater heating step of Step S 5 , the SC1 is evenly supplied to the entire front surface of the wafer W, whereby particles adhering to the front surface of the wafer W can be efficiently removed for cleaning the front surface of the wafer W. The SC1 is heated by the heater  54  and, therefore, is highly activated. As a result, the cleaning efficiency can be significantly improved. 
     In the SC1 supplying/heater heating step of Step S 5 , the output of the heater  54  is controlled to the third output level, thereby preventing the overheating of the front surface of the wafer W and the insufficient heating of the SC1 liquid film. As a result, the front surface of the wafer W can be cleaned without any damage thereto in the SC1 supplying/heater heating step of Step S 5 . 
     In this embodiment, the rotation speed of the wafer W is not changed in the SC1 supplying/heater heating step of Step S 5 . Therefore, the output of the heater  54  is not changed in the SC1 supplying/heater heating step. Where the rotation speed of the wafer W is changed in the SC1 supplying/heater heating step, however, the output of the heater  54  is changed according to the change in the rotation speed. 
     After the heating by the heater  54  is continued for a predetermined period, the CPU  55 A controls the heater  54  to stop the emission of the infrared radiation, and controls the pivot drive mechanism  36  and the lift drive mechanism  37  to move the heater  54  back to its home position. 
     After the supply of the SC1 is continued for the predetermined period, the CPU  55 A closes the SC1 valve  31 , and controls the second liquid arm pivot mechanism  29  to move the SC1 nozzle  25  back to its home position. While maintaining the rotation speed of the wafer W at the third rotation speed, the CPU  55 A opens the DIW valve  27  to supply the DIW from the spout of the DIW nozzle  24  toward around the rotation center of the wafer W (Step S 6 : final rinsing step). 
     The DIW supplied to the front surface of the wafer W receives a centrifugal force generated by the rotation of the wafer W to flow toward the peripheral edge of the wafer W on the front surface of the wafer W, whereby SC1 adhering to the front surface of the wafer W is rinsed away with the DIW. 
     After a lapse of a predetermined period from the start of the final rinsing step, the CPU  55 A closes the DIW valve  27  to stop supplying the DIW to the front surface of the wafer W. Thereafter, the CPU  55 A drives the rotative drive mechanism  6  to increase the rotation speed of the wafer W to a predetermined higher rotation speed (e.g., 1500 to 2500 rpm), whereby a spin drying process is performed to spin off the DIW from the wafer W for drying the wafer W (Step S 7 ). 
     In the spin drying process of Step S 7 , DIW adhering to the wafer W is removed from the wafer W. It is noted that the rinse liquid to be used in the intermediate rinsing step of Step S 4  and the final rinsing step of Step S 6  is not limited to the DIW, but other examples of the rinse liquid include carbonated water, electrolytic ion water, ozone water, reduced water (hydrogen water) and magnetic water. 
     After the spin drying process is performed for a predetermined period, the CPU  55 A controls the rotative drive mechanism  6  to stop rotating the wafer holding mechanism  3 . Thus, the resist removing process for the single wafer W ends, and the treated wafer W is unloaded from the treatment chamber  2  by the center robot CR (Step S 8 ). 
     According to this embodiment, as described above, the output of the heater  54  is adjusted according to the rotation speed of the wafer W in the SPM liquid film forming step of Step S 31 , the SPM liquid film heating step of Step S 32  and the SC1 supplying/heater heating step of Step S 5 . Therefore, the output of the heater  54  can be adapted for the thickness of the liquid film of the treatment liquid (the SPM liquid or the SC1) present on the front surface of the wafer W. Even if the thickness of the liquid film of the treatment liquid (the SPM liquid or the SC1) varies due to a change in the rotation speed of the wafer W, the overheating of the front surface of the wafer W and the insufficient heating of the treatment liquid (the SPM liquid or the SC1) can be prevented. As a result, the front surface of the wafer W can be advantageously treated without any damage thereto. 
       FIG. 12  is a time chart showing a second exemplary resist removing process according to the first embodiment of the present invention. The second exemplary process differs from the first exemplary process in that an SPM supplying/heater heating step of Step S 33  shown in  FIG. 12  is performed instead of the SPM supplying/heater heating step of Step S 3  shown in  FIG. 8 . Other process steps are performed in the same manner as in the first exemplary process. Therefore, only the SPM supplying/heater heating step of Step S 33  in the second exemplary process will be described. 
     In the SPM supplying/heater heating step of Step S 33 , the SPM liquid is supplied from the lift-off liquid nozzle  4  to the front surface of the wafer W to cover the front surface of the wafer W with a liquid film of the SPM liquid, and the infrared radiation is emitted from the heater  54  as in the SPM supplying/heater heating step of Step S 3  of the first exemplary process. However, the supply of the SPM liquid is continued throughout the period of the emission of the infrared radiation. This differentiates the SPM supplying/heater heating step of Step S 33  from the SPM supplying/heater heating step of Step S 3  shown in  FIG. 8 . 
     In the SPM supplying/heater heating step of Step S 33 , the wafer W is rotated at a relatively high rotation speed (fourth rotation speed) for a predetermined period (for example, corresponding to the SPM liquid supply period in the first exemplary process), and then rotated at a relatively low fifth rotation speed lower than the fourth rotation speed for a predetermined period (for example, corresponding to the heating period in the first exemplary process) as in the SPM supplying/heater heating step of Step S 3 . The fourth rotation speed is such that the entire front surface of the wafer W can be covered with the SPM liquid, and may be, for example, 150 rpm which is equal to the first rotation speed described above. 
     In the second exemplary process, when the rotation speed of the wafer W is the relatively high fourth rotation speed, the output of the heater  54  is controlled to a relatively low fourth output level. When the wafer W is rotated at the relatively high fourth rotation speed, a relatively thin SPM liquid film is formed on the front surface of the wafer W. However, the fourth output level of the heater  54  is such that sufficient heat can reach a portion of the SPM liquid film present around the interface between the front surface of the wafer W and the SPM liquid film without damaging the front surface of the wafer W. 
     When the rotation speed of the wafer W is the relatively low fifth rotation speed (e.g., not lower than 15 rpm), the output of the heater  54  is controlled to a fifth output level that is higher than the fourth output level. When the rotation speed of the wafer W is changed to the relatively low fifth rotation speed, the thickness of the SPM liquid film is increased. The fifth output level of the heater  54  is such that sufficient heat can reach a portion of the SPM liquid film present around the interface between the front surface of the wafer W and the SPM liquid film without damaging the front surface of the wafer W. 
     The fifth rotation speed is lower than the fourth rotation speed and higher than the second rotation speed of the first exemplary process described above. Thus, a thicker SPM liquid film is formed on the front surface of the wafer W than when the wafer W is rotated at the fourth rotation speed. The fifth rotation speed is required to be, for example, such that the SPM liquid film can be retained on the front surface of the wafer W. 
     Thus, the second exemplary process employing the SPM supplying/heater heating step of Step S 33  provides effects comparable to those of the first exemplary process described above. 
       FIG. 13  is a block diagram showing the electrical construction of a substrate treatment apparatus  101  according to a second embodiment of the present invention. A computer  155  of the second embodiment differs from the computer  55  of the first embodiment in that a rotation speed/heater moving speed relational table  55 E for the SPM liquid is employed instead of the rotation speed/heater output relational table  55 C for the SPM liquid, and a rotation speed/heater moving speed relational table  55 G for the SC1 is employed instead of the rotation speed/heater output relational table  55 F for the SC1. The other arrangement is the same as the treatment unit  100  of the first embodiment. In  FIG. 13 , components corresponding to those of the first embodiment shown in  FIG. 6  will be designated by the same reference characters as in  FIG. 6 , and duplicate description will be omitted. 
     The rotation speed/heater moving speed relational table  55 E for the SPM liquid specifies a relationship between the rotation speed of the wafer W and the moving speed of the heater  54  (more specifically, the pivoting speed of the heater arm  34 ) such that the moving speed of the heater  54  is reduced as the rotation speed of the wafer W decreases. That is, the rotation speed/heater moving speed relational table  55 E for the SPM liquid specifies a relationship between the rotation speed of the wafer W and the moving speed of the heater  54  such that sufficient heat can reach a portion of the SPM liquid present around the interface between the front surface of the wafer W and the SPM liquid film without damaging the front surface of the wafer W. 
     The thickness of the liquid film of the SPM liquid supplied to the front surface of the wafer W is dependent on the rotation speed of the wafer W. Therefore, the higher the rotation speed of the wafer W, the thinner the SPM liquid film. The lower the rotation speed of the wafer W, the thicker the SPM liquid film. If the output of the heater  54  is kept constant, the amount of the heat applied to a predetermined portion of the SPM liquid film varies depending on the rotation speed of the wafer W. 
     That is, the amount of the heat applied to the predetermined portion of the liquid film is relatively reduced by increasing the moving speed of the heater  54 . On the other hand, the amount of the heat applied to the predetermined portion of the liquid film is relatively increased by reducing the moving speed of the heater  54 . Where the rotation speed of the wafer W and the moving speed of the heater  54  have a relationship specified by the rotation speed/heater moving speed relational table  55 E for the SPM liquid, sufficient heat can reach the SPM liquid film portion present around the interface between the front surface of the wafer W and the SPM liquid film without damaging the front surface of the wafer W. 
     The rotation speed/heater moving speed relational table  55 G for the SC1 specifies a relationship between the rotation speed of the wafer W and the moving speed of the heater  54  (more specifically, the pivoting speed of the heater arm  34 ) such that the moving speed of the heater  54  is reduced as the rotation speed of the wafer W decreases. That is, the rotation speed/heater moving speed relational table  55 G for the SC1 specifies a relationship between the rotation speed of the wafer W and the moving speed of the heater  54  such that sufficient heat can reach a portion of the SC1 liquid film present around the interface between the front surface of the wafer W and the SC1 liquid film without damaging the front surface of the wafer W. Therefore, sufficient heat can reach the SC1 liquid film portion present around the interface between the front surface of the wafer W and the SC1 liquid film without damaging the front surface of the wafer W. 
       FIG. 14  is a flowchart showing a third exemplary resist removing process according to the second embodiment of the present invention.  FIG. 15  is a time chart for explaining an SPM liquid film forming step and an SPM liquid film heating step of the third exemplary process.  FIG. 16  is a flow chart showing how to control the moving speed of the heater  54 .  FIG. 17  is a time chart for explaining an SC1 supplying/heater heating step of the third exemplary process. 
     Referring to  FIGS. 1A and 1B  and  FIGS. 13 to 17 , the third exemplary resist removing process will hereinafter be described. 
     Prior to the resist removing process, the user operates the recipe inputting portion  57  to determine the recipe  55 B to specify conditions for the treatment of the wafer W. Subsequently, the CPU  55 A of the computer  155  performs a process sequence for the treatment of the wafer W based on the recipe  55 B. 
     The CPU  55 A controls the indexer robot IR (see  FIG. 1A ) and the center robot CR (see  FIG. 1A ) to load a wafer W subjected to the ion implantation process into the treatment chamber  2  (Step S 11 : Wafer loading step). The wafer W is not subjected to the resist ashing process. The wafer W is transferred to the wafer holding mechanism  3  with its front surface facing up. At this time, the heater  54 , the lift-off liquid nozzle  4  and the SC1 nozzle  25  are respectively located at their home positions so as not to prevent the loading of the wafer W. 
     With the wafer W held by the wafer holding mechanism  3 , the CPU  55 A controls the rotative drive mechanism  6  to start rotating the wafer W (Step S 12 ). As shown in  FIG. 15 , the rotation speed of the wafer W is increased to a predetermined sixth rotation speed, and then maintained at the sixth rotation speed. The sixth rotation speed is such that the entire front surface of the wafer W can be covered with the SPM liquid, and may be, for example, 150 rpm which is equal to the first rotation speed (see  FIG. 8 ) in the first exemplary process of the first embodiment described above. 
     As in the first exemplary process of the first embodiment, the CPU  55 A controls the first liquid arm pivot mechanism  12  to move the lift-off liquid nozzle  4  to above the wafer W and locate the lift-off liquid nozzle  4  above the rotation center of the wafer W (on the rotation axis A1). Further, the CPU  55 A opens the sulfuric acid valve  18 , the hydrogen peroxide solution valve  20  and the lift-off liquid valve  23  to supply the SPM liquid from the lift-off liquid nozzle  4  to the front surface of the wafer W (Step S 41 : SPM liquid film forming step). 
     The SPM liquid supplied to the front surface of the wafer W spreads from a center portion of the front surface of the wafer W to a peripheral portion of the front surface of the wafer W by a centrifugal force generated by the rotation of the wafer W. Thus, the SPM liquid spreads over the entire front surface of the wafer W to form a liquid film of the SPM liquid which covers the entire front surface of the wafer W. The SPM liquid film has a thickness of, for example, 0.4 mm. 
     As shown in  FIG. 15 , the CPU  55 A controls the pivot drive mechanism  36  and the lift drive mechanism  37  to move the heater  54  to above the edge adjacent position (indicated by the two-dot-and-dash line in  FIG. 5 ) from the home position defined on the lateral side of the wafer holding mechanism  3  and then down to the edge adjacent position, and further move the heater  54  at a first moving speed in one direction toward the center adjacent position (indicated by the one-dot-and-dash line in  FIG. 5 ). 
     The SPM liquid film forming step of Step S 41  and an SPM liquid film heating step of Step S 42  to be described below are collectively referred to as an SPM supplying/heater heating step (Step S 13 ). Throughout the SPM supplying/heater heating step of Step S 13 , the heater  54  emits infrared radiation. In this embodiment, the output of the heater  54  is set at a fixed output level (sixth output level). The sixth output level is, for example, higher than the first output level (see  FIG. 8 ) employed in the first embodiment described above. 
     In the SPM liquid film forming step of Step S 41 , as shown in  FIG. 16 , the CPU  55 A judges if the heater  54  is currently in a movement period, with reference to the timer (not shown) for monitoring the progression status of the resist removing process as in the first exemplary process of the first embodiment (Step S 23 ). 
     If the heater  54  is in the movement period (YES in Step S 23 ), the CPU  55 A determines the pivoting speed of the heater arm  34  based on the rotation speed of the wafer W stored in the recipe  55 B and the rotation speed/heater moving speed relational table  55 E for the SPM liquid, and controls the pivot drive mechanism  36  to move the heater arm  34  at the pivoting speed thus determined. That is, the moving speed of the heater  54  (the pivoting speed of the heater arm  34 ) is generally constant, but is changed during the movement period of the heater  54  by thus controlling the pivot drive mechanism  36 . The SPM liquid film present on the front surface of the wafer W can be heated to a higher temperature by the infrared radiation emitted from the heater  54 . Thus, even a resist having a hardened surface layer can be removed from the front surface of the wafer W without ashing thereof. 
     If the heater  54  is not in the movement period (NO in Step S 23 ), on the other hand, the CPU  55 A does not control the pivot drive mechanism  36 . 
     In the SPM supplying/heater heating step of Step S 13 , the moving speed of the heater  54  is thus controlled to the moving speed suitable for the rotation speed of the wafer W stored in the recipe  55 B. In the SPM liquid film forming step of Step S 41 , the rotation speed of the wafer W is the relatively high sixth rotation speed, so that a relatively thin SPM liquid film is formed on the front surface of the wafer W. Therefore, the CPU  55 A controls the moving speed of the heater  54  to the relatively high first moving speed (e.g., 5 mm/min) based on a relationship between the rotation speed of the wafer W and the moving speed of the heater  54  specified in the rotation speed/heater moving speed relational table  55 E for the SPM liquid (see  FIG. 13 ). 
     The first moving speed of the heater  54  is such that sufficient heat can reach a portion of the SPM liquid film present around the interface between the front surface of the wafer W and the SPM liquid film without damaging the front surface of the wafer W. This prevents the overheating of the front surface of the wafer W and the insufficient heating of the SPM liquid film. As a result, the resist can be efficiently lifted off from the front surface of the wafer W without damaging the front surface of the wafer W in the SPM liquid film forming step of Step S 41 . 
     After a lapse of a predetermined SPM liquid supply period from the start of the supply of the SPM liquid, the CPU  55 A closes the sulfuric acid valve  18 , the hydrogen peroxide solution valve  20  and the lift-off liquid valve  23  to stop supplying the SPM liquid from the lift-off liquid nozzle  4  as shown in  FIGS. 1B and 15 . Further, the CPU  55 A controls the first liquid arm pivot mechanism  12  to move the lift-off liquid nozzle  4  back to its home position after the stop of the supply of the SPM liquid. The SPM liquid supply period should be longer than a period required for forming the SPM liquid film to cover the entire front surface of the wafer W. The SPM liquid supply period varies depending on the spouting flow rate of the SPM liquid spouted from the lift-off liquid nozzle  4  and the rotation speed (sixth rotation speed) of the wafer W, but may be in a range of 3 seconds to 30 seconds, e.g., 15 seconds. 
     The CPU  55 A controls the rotative drive mechanism  6  to reduce the rotation speed of the wafer W from the sixth rotation speed to a seventh rotation speed. The seventh rotation speed is, for example, such that a thicker SPM liquid film can be retained on the front surface of the wafer W even without additional supply of the SPM liquid to the front surface of the wafer W (in a range of 1 rpm to 30 rpm, e.g., 15 rpm). At this time, the SPM liquid film has a thickness of, for example, 1.0 mm. 
     The CPU  55 A continues the emission of the infrared radiation from the heater  54  and, in this state, reduces the moving speed of the heater  54  from the first moving speed to a second moving speed (e.g., 2.5 mm/min) according to a change in the rotation speed of the wafer W (Step S 42 : SPM liquid film heating step). 
     In the SPM liquid film heating step of Step S 42 , the moving speed of the heater  54  is determined based on the rotation speed of the wafer W and the rotation speed/heater moving speed relational table  55 E for the SPM. Then, the CPU  55 A controls the pivot drive mechanism  36  to move the heater  54  at the moving speed thus determined. In the SPM liquid film heating step of Step S 42 , more specifically, the rotation speed of the wafer W is the seventh rotation speed that is lower than the sixth rotation speed. Therefore, a thicker SPM liquid film is formed on the front surface of the wafer W than when the wafer W is rotated at the sixth rotation speed. As described above, the rotation speed/heater moving speed relational table  55 E for the SPM specifies a relationship between the rotation speed of the wafer W and the moving speed of the heater  54  such that the moving speed of the heater  54  is reduced as the rotation speed of the wafer W decreases. Therefore, the CPU  55 A controls the moving speed of the heater  54  to the second moving speed. 
     The second moving speed of the heater  54  is such that sufficient heat can reach the entire SPM liquid film present around the interface between the front surface of the wafer W and the SPM liquid film without damaging the front surface of the wafer W. This prevents the overheating of the front surface of the wafer W and the insufficient heating of the SPM liquid film. As a result, the resist can be efficiently lifted off from the front surface of the wafer W without damaging the front surface of the wafer W in the SPM liquid film heating step of Step S 42 . 
     Immediately after the start of the SPM liquid film heating step of Step S 42 , the heater  54  is located around the middle adjacent position (indicated by the solid line in  FIG. 5 ) in this embodiment. The CPU  55 A controls the pivot drive mechanism  36  to move the heater  54  at the second moving speed from the middle adjacent position toward the center adjacent position (indicated by the one-dot-and-dash line in  FIG. 5 ). 
     After the heater  54  reaches the center adjacent position, the heating of the wafer W is continued at the center adjacent position for a predetermined period. In the SPM liquid film heating step of Step S 42 , a portion of the wafer W opposed to the bottom plate  52  of the heater head  35  and the SPM liquid film present on that portion of the wafer W are heated by the infrared radiation emitted from the heater  54 . The SPM liquid film heating step of Step S 42  is performed for a predetermined heating period (in a range of 2 second to 90 seconds, e.g., about 40 seconds). 
     After a lapse of a predetermined period from the start of the emission of the infrared radiation from the heater  54 , the CPU  55 A closes the sulfuric acid valve  18  and the hydrogen peroxide solution valve  20 , and controls the heater  54  to stop the emission of the infrared radiation. Further, the CPU  55 A controls the pivot drive mechanism  36  and the lift drive mechanism  37  to move the heater  54  back to its home position. 
     Then, as shown in  FIG. 15 , the CPU  55 A controls the rotative drive mechanism  6  to increase the rotation speed of the wafer W to a predetermined eighth rotation speed, and opens the DIW valve  27  to supply the DIW from the spout of the DIW nozzle  24  toward around the rotation center of the wafer W (Step S 14 : Intermediate rinsing step). The eighth rotation speed is in a range of 300 rpm to 1500 rpm, e.g., 1000 rpm. 
     The DIW supplied onto the front surface of the wafer W receives a centrifugal force generated by the rotation of the wafer W to flow toward the peripheral edge of the wafer W on the front surface of the wafer W. Thus, SPM liquid adhering to the front surface of the wafer W is rinsed away with the DIW. After the supply of the DIW is continued for a predetermined period, the CPU  55 A closes the DIW valve  27  to stop supplying the DIW to the front surface of the wafer W. 
     While maintaining the rotation speed of the wafer W at the eighth rotation speed, as shown in  FIG. 17 , the CPU  55 A opens the SC1 valve  31  to supply the SC1 from the SC1 nozzle  25  to the front surface of the wafer W (Step S 15 : SC1 supplying/heater heating step). The CPU  55 A controls the second liquid arm pivot mechanism  29  to pivot the second liquid arm  28  within the predetermined angular range to reciprocally move the SC1 nozzle  25  between a position above the rotation center of the wafer W and a position above the peripheral edge of the wafer W. Thus, an SC1 supply position on the front surface of the wafer W to which the SC1 is supplied from the SC1 nozzle  25  is reciprocally moved along an arcuate path crossing the wafer rotating direction in a range from the rotation center of the wafer W to the peripheral edge of the wafer W. Thus, the SC1 spreads over the entire front surface of the wafer W, whereby a thin liquid film of the SC1 is formed as covering the entire front surface of the wafer W. 
     The front surface of the wafer W and the SC1 liquid film are warmed by the heater  54  during the supply of the SC1 to the wafer W. As in the SPM supplying/heater heating step of Step S 13 , the CPU  55 A controls the heater  54  to start emitting the infrared radiation, and controls the pivot drive mechanism  36  and the lift drive mechanism  37  to move the heater  54  from the home position defined on the lateral side of the wafer holding mechanism  3  to above the edge adjacent position (indicated by the two-dot-and-dash line in  FIG. 5 ) and then down to the edge adjacent position, and move the heater  54  toward the center adjacent position (indicated by the one-dot-and-dash line in  FIG. 5 ) at a constant speed. 
     In the SC1 supplying/heater heating step of Step S 15 , the output level of the heater  54  is fixed to the sixth output level. 
     In the SC1 supplying/heater heating step of Step S 15 , the method of scanning the SC1 nozzle  25  and the heater  54  is determined so as to prevent the SC1 nozzle  25  and the heater  54  from interfering with each other. 
     The CPU  55 A moves the heater  54  to above the edge adjacent position and then down to the edge adjacent position, and moves the heater  54  toward the center adjacent position (indicated by the one-dot-and-dash line in  FIG. 5 ) at a predetermined third moving speed. 
     In the SC1 supplying/heater heating step of Step S 15 , the moving speed of the heater  54  is determined based on the rotation speed of the wafer W and the rotation speed/heater moving speed relational table  55 G for the SC1. Then, the CPU  55 A controls the pivot drive mechanism  36  to move the heater  54  at the moving speed thus determined. In the SC1 supplying/heater heating step of Step S 15 , the rotation speed of the wafer W is kept constant at the eighth rotation speed. The moving speed of the heater  54  is controlled to the constant third moving speed suitable for the rotation speed of the wafer W. 
     The third moving speed is such that sufficient heat can reach the SC1 liquid film portion present around the interface between the front surface of the wafer W and the SC1 liquid film without damaging the front surface of the wafer W in the SC1 supplying/heater heating step of Step S 15 . 
     In the SC1 supplying/heater heating step of Step S 15 , the SC1 is evenly supplied to the entire front surface of the wafer W, whereby particles adhering to the front surface of the wafer W can be efficiently removed for cleaning the front surface of the wafer W. The SC1 is heated by the heater  54  and, therefore, is highly activated. As a result, the cleaning efficiency can be significantly improved. 
     In the SC1 supplying/heater heating step of Step S 15 , the moving speed of the heater  54  is controlled to the third moving speed, thereby preventing the overheating of the front surface of the wafer W and the insufficient heating of the SC1 liquid film. As a result, the front surface of the wafer W can be cleaned without any damage thereto in the SC1 supplying/heater heating step of Step S 15 . 
     In this embodiment, the rotation speed of the wafer W is not changed in the SC1 supplying/heater heating step of Step S 15  and, therefore, the output of the heater  54  is not changed in the SC1 supplying/heater heating step. Where the rotation speed of the wafer W is changed in the SC1 supplying/heater heating step, however, the output of the heater  54  is changed according to the change in the rotation speed. 
     After the heating by the heater  54  is continued for a predetermined period, the CPU  55 A controls the heater  54  to stop emitting the infrared radiation, and controls the pivot drive mechanism  36  and the lift drive mechanism  37  to move the heater  54  back to its home position. 
     After the supply of the SC1 is continued for a predetermined period, the CPU  55 A performs a final rinsing step of Step S 16 , a drying step of Step S 17  and a wafer unloading step of Step S 18  in the same manner as the final rinsing step of Step S 6 , the drying step of Step S 7  and the wafer unloading step of Step S 8  of the first embodiment. 
     According to this embodiment, as described above, the heater  54  is moved along the front surface of the wafer W by the pivot drive mechanism  36  in the SPM liquid film forming step of Step S 41 , the SPM liquid film heating step of Step S 42  and the SC1 supplying/heater heating step of Step S 15 . The moving speed of the heater  54  is adjusted according to the rotation speed of the wafer W. Therefore, the moving speed of the heater  54  can be adapted for the thickness of the liquid film present on the front surface of the wafer W. That is, the amount of the heat to be applied to the predetermined portion of the liquid film of the treatment liquid (the SPM liquid or the SC1) can be relatively reduced by increasing the moving speed of the heater  54 . On the other hand, the amount of the heat to be applied to the predetermined liquid film portion can be relatively increased by reducing the moving speed of the heater  54 . Even if the thickness of the liquid film of the treatment liquid (the SPM liquid or the SC1) is changed due to a change in the rotation speed of the wafer W, therefore, the overheating of the front surface of the wafer W and the insufficient heating of the SPM liquid film can be prevented. As a result, the front surface of the wafer W can be advantageously treated with the use of the heater  54  without any damage thereto. 
       FIG. 18  is a time chart showing a fourth exemplary resist removing process according to the second embodiment of the present invention. In the second embodiment, the fourth exemplary process differs from the third exemplary process in that an SPM supplying/heater heating step of Step S 43  shown in  FIG. 18  is performed instead of the SPM supplying/heater heating step of Step S 13  shown in  FIG. 15 . Other process steps are performed in the same manner as in the third exemplary process of the second embodiment. Therefore, only the SPM supplying/heater heating step of Step S 43  in the fourth exemplary process will be described. 
     In the SPM supplying/heater heating step of Step S 43 , the SPM liquid is supplied from the lift-off liquid nozzle  4  to the front surface of the wafer W to cover the front surface of the wafer W with a liquid film of the SPM liquid, and the infrared radiation is emitted from the heater  54  as in the SPM supplying/heater heating step of Step S 13 . However, the supply of the SPM liquid from the lift-off liquid nozzle  4  is continued throughout the period of the emission of the infrared radiation. This differentiates the SPM supplying/heater heating step of Step S 43  from the SPM supplying/heater heating step of Step S 13  shown in  FIG. 15 . 
     In the SPM supplying/heater heating step of Step S 43 , the wafer W is rotated at a relatively high rotation speed (ninth rotation speed) for a predetermined period (for example, corresponding to the SPM liquid supply period in the third exemplary process), and then rotated at a relatively low tenth rotation speed lower than the ninth rotation speed for a predetermined period (for example, corresponding to the liquid film heating period in the third exemplary process) as in the SPM supplying/heater heating step of Step S 13 . The ninth rotation speed is such that the entire front surface of the wafer W can be covered with the SPM liquid, and may be, for example, 150 rpm which is equal to the sixth rotation speed in the third exemplary process described above. 
     In the fourth exemplary process, when the rotation speed of the wafer W is the relatively high ninth rotation speed, the moving speed of the heater  54  is controlled to a relatively high third moving speed. When the wafer W is rotated at the relatively high ninth rotation speed, a relatively thin SPM liquid film is formed on the front surface of the wafer W. However, the third moving speed is such that sufficient heat can reach the SPM liquid film portion present around the interface between the front surface of the wafer W and the SPM liquid film without damaging the front surface of the wafer W. 
     When the rotation speed of the wafer W is the relatively low tenth rotation speed (e.g., not lower than 15 rpm), the moving speed of the heater  54  is controlled to a fourth moving speed that is lower than the third moving speed. When the rotation speed of the wafer W is changed to the relatively low tenth rotation speed, the thickness of the SPM liquid film is increased. The fourth moving speed of the heater  54  is such that sufficient heat can reach the SPM liquid film portion present around the interface between the front surface of the wafer W and the SPM liquid film on the front surface without damaging the front surface of the wafer W. 
     The tenth rotation speed is lower than the ninth rotation speed and higher than the seventh rotation speed of the third exemplary process described above. Thus, a thicker SPM liquid film is formed on the front surface of the wafer W than when the wafer W is rotated at the ninth rotation speed. The tenth rotation speed is required to be, for example, such that the SPM liquid film can be retained on the front surface of the wafer W. 
     Thus, the fourth exemplary process employing the SPM supplying/heater heating step of Step S 43  provides effects comparable to those of the third exemplary process described above. 
     While two embodiments of the present invention have thus been described, the invention may be embodied in other ways. 
     For example, a rotation speed/heater output/hater moving speed relational table specifying a relationship among the rotation speed of the wafer W, the output of the heater  54  and the moving speed of the heater  54  may be stored in the storage  55 D, and the CPU  55 A may be adapted to determine the output of the heater  54  and the moving speed of the heater  54  based on the rotation speed of the wafer W with reference to the table. 
     In the SPM supplying/heater heating steps of Steps S 3 , S 13 , S 33 , S 43  and the SC1 supplying/heater heating steps of Steps S 5  and S 15 , the heater  54  is moved at the constant moving speed in one direction from the edge adjacent position (indicated by the two-dot-and-dash line in  FIG. 5 ) toward the center adjacent position (indicated by the one-dot-and-dash line in  FIG. 5 ) by way of example. Alternatively, the heater  54  may be reciprocally moved at a predetermined moving speed between the edge adjacent position (indicated by the two-dot-and-dash line in  FIG. 5 ) and the center adjacent position (indicated by the one-dot-and-dash line in  FIG. 5 ). In this case, the heater  54  may be moved at different moving speeds in opposite reciprocal directions. In this case, a rotation speed/heater moving speed relational table specifying different moving speeds for the opposite reciprocal directions may be stored in the storage  55 D. 
     The infrared lamp  38  including the single annular lamp is used by way of example but not by way of limitation. Alternatively, the infrared lamp  38  may include a plurality of annular lamps disposed coaxially with each other, or may include a plurality of linear lamps disposed parallel to each other in a horizontal plane. 
     In the embodiments described above, the resist removing process is performed on the wafer W by way of example, but the present invention is applicable to an etching process typified by a phosphoric acid etching process. In this case, etching liquids such as a phosphoric acid aqueous solution and a hydrofluoric acid aqueous solution, and cleaning chemical liquids such as SC1 and SC2 (hydrochloric acid/hydrogen peroxide mixtures) may be used as the treatment liquid. 
     While the present invention has been described in detail by way of the embodiments thereof, it should be understood that these embodiments are merely illustrative of the technical principles of the present invention but not limitative of the invention. The spirit and scope of the present invention are to be limited only by the appended claims. 
     This application corresponds to Japanese Patent Application No. 2013-187626 filed in the Japan Patent Office on Sep. 10, 2013, the disclosure of which is incorporated herein by reference in its entirety.