Patent Publication Number: US-11380562-B2

Title: Substrate processing apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a divisional of prior U.S. patent application Ser. No. 16/440,135, filed Jun. 13, 2019, by Rei TAKEAKI, Koji ANDO, Tadashi MAEGAWA and Yosuke YASUTAKE, entitled “SUBSTRATE PROCESSING APPARATUS,” which is a divisional of U.S. patent application Ser. No. 15/181,619, filed Jun. 14, 2016, now U.S. Pat. No. 10,438,821, issued Oct. 8, 2019, which claims priority to Japanese Patent Application Nos. 2015-122700, filed Jun. 18, 2015, 2015-122703, filed Jun. 18, 2015 and 2015-122714, filed Jun. 18, 2015. The entire contents of each of these patent applications are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a technique of processing substrates such as a semiconductor wafer, a glass substrate for liquid crystal display, a glass substrate for plasma display, a substrate for optical disc, a substrate for magnetic disk, a substrate for magneto-optical disk, a glass substrate for photomask, and a substrate for solar cell (hereinafter, merely referred to as “substrates”). 
     Description of the Background Art 
     A device pattern (circuit pattern) is not usually formed right up to the end face of a substrate, and in many cases, the device pattern is formed in the upper surface region located inside from the end face of the substrate by a constant width. 
     In the deposition step for forming a device pattern, however, a film may be formed up to the outside of the region in which a device pattern is formed (hereinafter, merely referred to as a “device region”). The film formed outside of the device region is not required and also can cause various malfunctions. For example, the film formed outside of the device region may peel off during the processing steps, reducing yields or causing malfunction in, for example, a substrate processing apparatus. 
     In consideration of the above, the process of removing a thin film formed outside of the device region by etching, or, so-called bevel etching process is performed in some cases, and apparatuses for performing such a process are proposed (for example, see Japanese Patent Application Laid-Open Nos. 2011-066194 and 2009-070946). 
     The apparatuses of Japanese Patent Application Laid-Open Nos. 2011-066194 and 2009-070946 discharge a processing liquid onto a peripheral portion of an upper surface of a substrate from nozzles arranged above the peripheral portion while rotating the substrate about the central axis in a horizontal plane, thereby processing the peripheral portion of the upper surface. The nozzles have outlets that are opposed to a part of the rotation path of the peripheral portion of the substrate from above. The nozzles continuously discharge a processing liquid such that the processing liquid comes into contact with the portion, which is located below the outlets, of the peripheral portion of the upper surface of the substrate being rotated. Each part of the peripheral portion of the upper surface repeatedly passes through below the nozzles, and each time, is supplied with a fresh processing liquid from the nozzles. 
     Japanese Patent Application Laid-Open Nos. 2005-142290, 2014-072389, and 2003-264168 describe the apparatuses that supply processing liquids such as various chemical solutions to an upper surface of a substrate while heating the substrate by a heater opposed to the substrate, thereby processing the substrate. Heating the substrate improves, for example, a processing rate. 
     The apparatus of Japanese Patent Application Laid-Open No. 2005-142290 includes a heater opposed to the peripheral portion of the upper surface of the substrate and another heater opposed to the peripheral portion of the lower surface of the substrate. The apparatus supplies a processing liquid to the central portion of the upper surface while heating the peripheral portion of the substrate by these heaters from above and below, thereby processing the entire upper surface. The apparatus of Japanese Patent Application Laid-Open No. 2014-072389 discharges a processing liquid onto the central portion of the upper surface of the substrate while heating the entire substrate by the heater opposed to the entire lower surface of the substrate, thereby processing the entire upper surface. The apparatus of Japanese Patent Application Laid-Open No. 2003-264168 discharges a processing liquid onto the peripheral portion of the upper surface of the substrate while heating the peripheral portion of the substrate by an annular heater opposed to the peripheral portion of the lower surface of the substrate, thereby processing the peripheral portion of the upper surface. 
     Japanese Patent Application Laid-Open No. 2004-79908 describes a substrate processing apparatus including an etching liquid supply nozzle and a pure water supply nozzle. The etching liquid supply nozzle discharges an etching liquid onto a plurality of positions of a peripheral portion of an upper surface of a substrate, which have different distances from the center of rotation of the substrate. The pure water supply nozzle discharges pure water for protection onto the central portion of the upper surface of the substrate. The pure water discharged onto the central portion of the upper surface is supplied to the entire upper surface by the rotation of the substrate and washes away the etching liquid dispersed in a to-be-protected region of the upper surface except for the peripheral portion. This protects the to-be-protected region. The etching liquid has a high concentration at the position with which the etching liquid comes into contact, and the etching liquid that has spread from that position toward the periphery is diluted with pure water and accordingly has a decreased concentration. For the etching process to advance uniformly at the respective positions with different radial distances from the center of rotation in the peripheral portion of the substrate, the apparatus of Japanese Patent Application Laid-Open No. 2004-79908 supplies an etching liquid to the plurality of positions with different distances from the center of rotation of the substrate, to thereby make the concentration of the etching liquid uniform in the peripheral portion of the substrate. 
     Japanese Patent Application Laid-Open No. 2003-86567 discloses a substrate processing apparatus including an etching liquid discharge nozzle and a rinse liquid discharge nozzle. The etching liquid discharge nozzle discharges an etching liquid such that the etching liquid comes into contact with the peripheral portion of the substrate. The rinse liquid discharge nozzle discharges a rinse liquid such that the rinse liquid comes into contact with the position of the substrate located on the side closer to the center of the substrate than the position with which the etching liquid comes into contact. The apparatus first positions both of the nozzles such that the etching liquid and the rinse liquid come into contact with two portions of the substrate closer to the center of the substrate, and then discharges the etching liquid and the rinse liquid from the respective nozzles, thereby performing an etching process. Subsequently, the apparatus stops discharging the etching liquid without changing the positions of the nozzles and continuously discharges the rinse liquid, thereby performing a rinse process. Subsequently, the apparatus moves the nozzles together toward the periphery of the substrate, thereby positioning the nozzles such that the rinse liquid comes into contact with the region from which the thin film has been removed by the first etching process and that the etching liquid comes into contact with the position on the side closer to the periphery of the substrate. The apparatus sequentially performs etching and rinse processes again after positioning. In the second rinse process, the rinse liquid comes into contact with the region from which the thin film has been removed. This prevents a situation in which the rinse liquid comes into contact with the thin film, and metal ions of the thin film flow out and adheres to the peripheral portion. 
     In the apparatuses of Japanese Patent Application Laid-Open Nos. 2011-066194 and 2009-070946, however, the respective parts of the peripheral portion of the upper surface arrive at the portion below the nozzle, with the processing liquid remaining in the respective parts. Thus, a processing liquid newly discharged from the nozzle (“fresh processing liquid”) comes into contact with the processing liquid (“residual processing liquid”) to cause splashes. When the splashed processing liquid enters the device region, a defect occurs in the device pattern. 
     When an inert gas is discharged at a high flow rate onto the landing position of the processing liquid in the peripheral portion of the upper surface of the substrate toward the upstream portion in the direction of rotation of the substrate, the residual processing liquid is blown off by a gas flow of an inert gas to be removed from the peripheral portion. This prevents a collision between the residual processing liquid and a fresh processing liquid. If an inert gas comes into contact with the residual processing liquid at a high flow rate, however, the residual processing liquid may splash to arrive at the device region. 
     If the flow rate of the inert gas is decreased to restrict the generation of splashes that can arrive at the device region, the residual processing liquid cannot be completely removed from the peripheral portion. As a result, a fresh processing liquid may come into contact with the residual processing liquid and cause splashes, and the splashed processing liquid may enter the device region. 
     According to Japanese Patent Application Laid-Open Nos. 2005-142290, 2014-072389, and 2003-264168, a space exists between the substrate and the heater, and as the substrate rotates, the room-temperature atmosphere existing around the peripheral portion of the substrate is taken into the space between the substrate and the heater. The substrate is cooled from the lower surface by the room-temperature atmosphere, which unfortunately decreases the heating efficiency of the substrate. 
     In the apparatuses of Japanese Patent Application Laid-Open Nos. 2004-79908 and 2003-86567, the etching liquid discharged onto the peripheral portion of the upper surface of the substrate wraps around the lower surface of the substrate. As a result, the lower surface of the substrate, which is not to be etched, may be etched, thus damaging the lower surface. In addition, the pure water and the rinse liquid that protect a to-be-protected region of the upper surface may dilute the etching liquid, decreasing the processing efficiency. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a substrate processing apparatus. 
     A substrate processing apparatus according to an aspect of the present invention includes a substrate holder, a rotating mechanism, a processing liquid discharge unit, and a gas discharge unit. The substrate holder is rotatably disposed about a predetermined rotation axis and holds a substrate substantially horizontally. The rotating mechanism rotates the substrate holder about the rotation axis. The processing liquid discharge unit discharges a liquid flow of a processing liquid such that the liquid flow comes into contact with a landing position in a rotation path of a peripheral portion of an upper surface of the substrate being rotated about the rotation axis. The gas discharge unit discharges a first gas flow of an inert gas from above toward a first position upstream from the landing position in a direction of rotation of the substrate in the rotation path so as to direct the first gas flow from the first position toward a periphery of the substrate, and discharges a second gas flow of the inert gas from above toward a second position upstream from the first position in the direction of rotation of the substrate in the rotation path so as to direct the second gas flow from the second position toward the periphery of the substrate. A kinetic energy of the second gas flow when the second gas flow is discharged is lower than a kinetic energy of the first gas flow when the first gas flow is discharged. 
     In this apparatus, the second gas flow having kinetic energy lower than that of the first gas flow comes into contact with the liquid film of the residual processing liquid in the peripheral portion of the substrate at the second position. This drains out the residual processing liquid out of the substrate while restricting the generation of splashes of the residual processing liquid that can arrive at the device region, thereby reducing the film thickness of the residual processing liquid. Thus, the first gas flow having high kinetic energy is caused to come into contact with the thinner portion of the residual processing liquid at the first position on the downstream side, thus draining most of the residual processing liquid out of the substrate while suppressing the generation of splashes of the residual processing liquid that can arrive at the device region. This restricts the generation of splashes that can arrive at the device region of the substrate due to a collision between the residual processing liquid and a fresh processing liquid discharged onto a further downstream landing position. Therefore, the peripheral portion of the upper surface of the substrate is processed while restricting the processing liquid from entering the device region of the upper surface of the substrate. 
     A substrate processing apparatus according to another aspect of the present invention includes a substrate holder, a rotating mechanism, a chemical solution discharge unit, a heater, and a gas discharge mechanism. The substrate holder is rotatably disposed about a predetermined rotation axis and holds a substrate substantially horizontally. The rotating mechanism rotates the substrate holder about the rotation axis. The chemical solution discharge unit discharges a chemical solution onto a to-be-processed surface of the substrate. The heater includes an opposed surface opposed to an opposite surface of the substrate opposite to the to-be-processed surface in a contactless manner, and heats the substrate. The gas discharge mechanism discharges an inert gas preheated into a space between the opposite surface of the substrate and the opposed surface of the heater. 
     This apparatus discharges an inert gas preheated into the space between the surface of the substrate opposite to the to-be-processed surface and the opposed surface of the heater. This restricts an atmosphere from entering the space to restrict a reduction in heating efficiency and restricts a reduction in heating efficiency also by the inert gas. Therefore, the substrate is processed while heating the substrate efficiently. 
     A substrate processing apparatus according to still another aspect of the present invention includes a substrate holder, a rotating mechanism, a chemical solution discharge nozzle, and a rinse liquid discharge nozzle. The substrate holder is rotatably disposed about a predetermined rotation axis and holds a substrate substantially horizontally. The rotating mechanism rotates the substrate holder about the rotation axis. The chemical solution discharge nozzle discharges a chemical solution such that the chemical solution comes into contact with a first position in a first rotation path of a peripheral portion of a to-be-processed surface of the substrate. The rinse liquid discharge nozzle discharges a rinse liquid such that the rinse liquid comes into contact with a second position in a second rotation path of a peripheral portion of a to-be-protected surface of the substrate opposite to the to-be-processed surface. The second position is a position upstream from the first position in a direction of rotation of the substrate and is set in advance such that, before the rinse liquid moves in a circumferential direction of the substrate and arrives at the first position or its vicinity, the rinse liquid has wrapped around an end face of the substrate from the to-be-protected surface of the substrate and hardly wrapped around the peripheral portion of the to-be-processed surface. 
     This apparatus restricts the rinse liquid from wrapping around the to-be-processed surface while the rinse liquid moves from the second position to the first position or its vicinity in the circumferential direction of the substrate. This restricts the dilution of the chemical solution discharged onto the first position with the rinse liquid at the peripheral portion of the to-be-processed surface of the substrate. In addition, the rinse liquid has wrapped around the end face from the to-be-protected surface before the rinse liquid arrives at the first position or its vicinity in the circumferential direction of the substrate. As a result, the chemical solution that begins to wrap around the to-be-protected surface from the first position is washed away with the rinse liquid, thus diluting the chemical solution. This restricts the to-be-protected surface from being processed with the chemical solution that has wrapped around the to-be-protected surface while discharging the chemical solution onto the peripheral portion of the to-be-processed surface of the substrate to process the peripheral portion efficiently. 
     The present invention therefore has an object to provide a technique of processing a peripheral portion of an upper surface of a substrate while restricting a processing liquid from entering a device region of the upper surface of the substrate. The present invention has another object to provide a technique of processing a substrate while efficiently heating the substrate. The present invention has sill has another object to provide a technique of restricting a to-be-protected surface of a substrate from being processed with a chemical solution that has wrapped around the to-be-protected surface while efficiently discharging a chemical solution onto a peripheral portion of the to-be-processed surface to process the peripheral portion. 
     In the present invention, the term “to-be-processed surface” means a surface that is to be processed (“surface to be processed”), and the term “to-be-protected surface” means a surface that is to be protected (“surface to be protected”). In the event that the processing with a processing liquid is to be performed on a major surface of a substrate, the major surface represents the “to-be-processed surface” of the invention, and the surface opposite to the major surface represents the “to-be-protected surface” of the invention. Similarly, the term “to-be-processed region” means a region that is to be processed (“region to be processed”), and the term “to-be-protected region” means a region that is to be protected (“region to be protected”). 
     These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic side view for explaining the configuration of a substrate processing apparatus according to a first embodiment of the present invention; 
         FIG. 2  is a schematic top view for explaining the configuration of the substrate processing apparatus according to the first (second) embodiment of the present invention; 
         FIG. 3  is a schematic perspective view for explaining the configuration of the substrate processing apparatus according to the first (second) embodiment of the present invention; 
         FIG. 4  is a top view schematically illustrating positions, at which a liquid flow of a processing liquid and gas flows of an inert gas that are discharged from the substrate processing apparatus according to the first (second) embodiment of the present invention come into contact with a peripheral portion of a substrate; 
         FIG. 5  is a schematic side view for explaining angles of dip of the gas flows and the liquid flow; 
         FIG. 6  is a schematic top view for explaining angles of traverse of the gas flows and the liquid flow; 
         FIG. 7  illustrates an example of how the gas flows and the liquid flow are discharged; 
         FIG. 8  illustrates another example of how the gas flows and the liquid flow are discharged; 
         FIG. 9  is a perspective view of an example of nozzles of a gas discharge mechanism for peripheral portion; 
         FIG. 10  schematically illustrates positions at which the gas flows discharged from the nozzles of  FIG. 9  come into contact with the substrate; 
         FIG. 11  is a perspective view of another example of nozzles of the gas discharge mechanism for peripheral portion; 
         FIG. 12  schematically illustrates positions at which the gas flows discharged from the nozzle of  FIG. 11  come into contact with the substrate; 
         FIG. 13  is a flowchart illustrating an example of the operation of the substrate processing apparatus of  FIG. 1 ; 
         FIG. 14  is a schematic side view for explaining the configuration of the substrate processing apparatus according to the second embodiment of the present invention; 
         FIGS. 15 to 17  are schematic top views of a heater of  FIG. 14 ; 
         FIG. 18  is a schematic cross-sectional view of a heater of the substrate processing apparatus according to the second (third) embodiment of the present invention; 
         FIG. 19  is a schematic cross-sectional view of the heater of  FIG. 18 ; 
         FIG. 20  illustrates an example inert gas discharged between the heater of  FIG. 18  and the substrate; 
         FIG. 21  graphically illustrates an example relationship between a flow rate of an inert gas and a temperature of a peripheral portion of the substrate; 
         FIG. 22  is a flowchart illustrating an example operation of the substrate processing apparatus of  FIG. 14 ; 
         FIG. 23  is a schematic side view for explaining the configuration of the substrate processing apparatus according to the third embodiment of the present invention; 
         FIG. 24  is a schematic top view for explaining the configuration of the substrate processing apparatus of  FIG. 23 ; 
         FIG. 25  is a schematic perspective view for explaining the configuration of the substrate processing apparatus of  FIG. 23 ; 
         FIG. 26  is a top view schematically illustrating positions at which a processing liquid, a rinse liquid, and an inert gas discharged by the substrate processing apparatus of  FIG. 23  come into contact with the peripheral portion of a substrate; 
         FIG. 27  is a schematic side view illustrating a state in which the nozzles individually discharge the processing liquid and the like to the positions of  FIG. 26 ; 
         FIGS. 28 to 30  are schematic top views of a heater of the substrate processing apparatus of  FIG. 23 ; 
         FIG. 31  is a flowchart illustrating an example operation of the substrate processing apparatus of  FIG. 23 ; 
         FIG. 32  is a schematic perspective view of another example of the heater of  FIG. 28 ; 
         FIG. 33  is a schematic perspective view of another example of the heater of  FIG. 28 ; and 
         FIG. 34  is a cross-sectional view of a substrate, which schematically illustrates how the rinse liquid discharged by the substrate processing apparatus of  FIG. 23  wraps around an end face of the substrate. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of the present invention will now be described with reference to the drawings. In the drawings, components having similar configuration and functions bear the same reference signs, and description thereof will not be repeated below. The embodiments below are examples of the implementation of the present invention, which do not limit the technical scope of the present invention. In the drawings below, for easy understanding, the dimensions and the numbers of the respective portions may be exaggerated or simplified. The up and down direction is a vertical direction, and a side close to a substrate relative to a spin chuck is an upper side. A “processing liquid” includes a “chemical solution” for use in the chemical solution process and a “rinse liquid (also referred to as a “cleaning liquid”) for use in the rinse process of washing away the chemical solution. The substrate W has an approximately circular surface shape. The substrate is transferred to and from the substrate processing apparatus by, for example, a robot, with the nozzle head and the like arranged at retreat positions. The substrate transferred to the substrate processing apparatus is detachably held by the spin chuck. The “inert gas” is a gas that is poorly reactive to a material for the substrate W and a thin film formed on the surface of the substrate W, which is, for example, nitrogen (N 2 ) gas, argon gas, or helium gas. 
     1. First Embodiment 
     1.1. Configuration of Substrate Processing Apparatus  1   
     The configuration of a substrate processing apparatus  1  will be described with reference to  FIGS. 1 to 4 .  FIGS. 1 to 3  are views for explaining the configuration of the substrate processing apparatus  1  according to an embodiment.  FIGS. 1 and 2  are a schematic side view and a schematic top view, respectively, of the substrate processing apparatus  1 .  FIG. 3  is a schematic perspective view of the substrate processing apparatus  1  as viewed from diagonally above.  FIG. 4  is a schematic top view of a substrate W, which illustrates an example of a positional relationship among positions at which a liquid flow of a processing liquid and gas flows of an inert gas that are discharged from the substrate processing apparatus  1  come into contact with the periphery of the substrate W. 
       FIGS. 1 to 3  illustrate the state in which the substrate W is being rotated in a predetermined direction of rotation (the direction of an arrow AR 1 ) about a rotation axis a 1  by a spin chuck  21 , with nozzle heads  48  to  50  arranged at their respective processing positions. In  FIG. 2 , the nozzle heads  48  to  50  arranged at their retreat positions and the like are indicated by phantom lines.  FIGS. 2 and 3  do not illustrate partial components of the substrate processing apparatus  1 , such as a scatter prevention unit  3 . 
     The substrate processing apparatus  1  includes a rotary holding mechanism  2 , the scatter prevention unit  3 , a surface protection unit  4 , a processing unit  5 , a nozzle moving mechanism  6 , a heating mechanism  7 , and a control unit  130 . These units  2  to  7  are electrically connected to the control unit  130  and operate in response to instructions from the control unit  130 . The control unit  130  may be, for example, a general-purpose computer. In other words, for example, the control unit  130  includes a CPU configured to perform various computations, a ROM that is a read-only memory configured to store a basic program, a RAM that is a random access memory for storing a various types of information, a magnetic disk for storing, for example, control software and data. The control unit  130  causes a CPU that is a main control unit to perform computations in accordance with the procedure described in the program, thereby controlling the respective units of the substrate processing apparatus  1 . 
     Rotary Holding Mechanism  2   
     The rotary holding mechanism  2  is a mechanism that can rotate the substrate W while keeping the substrate W in a substantially horizontal position, with one major surface of the substrate W facing upward. The rotary holding mechanism  2  rotates the substrate W about the rotation axis a 1  that extends vertically and passes through a center c 1  of the major surface. 
     The rotary holding mechanism  2  includes a spin chuck (“holding member” or “substrate holder”)  21  that is a disc-shaped member smaller than the substrate W. The spin chuck  21  is provided such that its upper surface is substantially horizontal and its central axis coincides with the rotation axis a 1 . The lower surface of the spin chuck  21  is coupled with a cylindrical rotary shaft  22 . The rotary shaft  22  is positioned such that its axis line coincides with the vertical direction. The axis line of the rotary shaft  22  coincides with the rotation axis a 1 . The rotary shaft  22  is connected with a rotational drive (e.g., motor)  23 . The rotational drive  23  rotatively drives the rotary shaft  22  about the axis line of the rotary shaft  22 . The spin chuck  21  can accordingly rotate about the rotation axis a 1  together with the rotary shaft  22 . The rotational drive  23  and the rotary shaft  22  serve as a rotating mechanism  231  that rotates the spin chuck  21  about the rotation axis a 1 . The rotary shaft  22  and the rotational drive  23  are accommodated in a tubular casing  24 . 
     A through hole (not shown) is provided in the central portion of the spin chuck  21  and is in communication with the interior space of the rotary shaft  22 . The interior space is connected with a pump (not shown) through a pipe (not shown) and an on/off valve (not shown). The pump and the on/off valve are electrically connected to the control unit  130 . The control unit  130  controls the operations of the pump and the on/off valve. The pump can selectively supply a negative pressure and a positive pressure in accordance with the control of the control unit  130 . When the pump supplies a negative pressure with the substrate W positioned substantially horizontally on the upper surface of the spin chuck  21 , the spin chuck  21  adheres to and holds the substrate W from below. When the pump supplies a positive pressure, the substrate W can be removed from the upper surface of the spin chuck  21 . 
     In this configuration, when the rotational drive  23  rotates the rotary shaft  22  with the spin chuck  21  adhering to and holding the substrate W, the spin chuck  21  is rotated about the axis line extending vertically. This causes the substrate W held on the spin chuck  21  to rotate in the direction of the arrow AR 1  about the rotation axis a 1  that extends vertically and passes through the center c 1  in the plane of the substrate W. 
     The spin chuck  21  may include a plurality of (e.g., six) chuck pins provided at appropriate intervals near the peripheral portion of the upper surface thereof and hold the substrate W by the plurality of chuck pins. In this case, the spin chuck  21  has a disc shape slightly larger than the substrate W. The plurality of chuck pins detachably hold the substrate W such that the center c 1  of the major surface of the substrate W coincides with the rotation axis a 1  and that the substrate W is positioned substantially horizontally at a position slightly higher than the upper surface of the spin chuck  21 . The direction of each chuck pin is selectively set, by the motor or the like electrically connected to the control unit  130 , to the direction in which the chuck pins abut against the periphery of the substrate W and holds the substrate W or the direction in which the check pins depart from the periphery of the substrate W and release the substrate W. 
     Scatter Prevention Unit  3   
     The scatter prevention unit  3  catches, for example, a processing liquid scattered from the substrate W rotated together with the spin chuck  21 . 
     The scatter prevention unit  3  includes a splash guard  31 . The splash guard  31  is a tubular member with an open upper end and is provided so as to surround the rotary holding mechanism  2 . In this embodiment, for example, the splash guard  31  includes three members: a bottom member  311 , an inside member (also referred to as an “inside guard” or merely a “guard”)  312 , and an outside member (also referred to as an “outside guard”)  313 . No outside member  313  may be provided, or a guard may be additionally provided outside of the outside member  313  so as to surround the rotary holding mechanism  2 . 
     The bottom member  311  is a tubular member having an open upper end and includes an annular bottom portion, a cylindrical inside wall portion extending upward from the inner edge portion of the bottom portion, and a cylindrical outside wall portion extending upward from the outer edge portion of the bottom portion. At least an edge of the inside wall portion and its vicinity are accommodated in an inside space of a flanged member  241  provided to the casing  24  of the rotary holding mechanism  2 . 
     On the bottom portion is formed a drain groove (not shown) communicating with the space between the inside wall portion and the outside wall portion. The drain groove is connected to the drain line of a factory. The drain groove is connected with a drain mechanism that forcibly exhausts air from the groove to provide a negative state in the space between the inside wall portion and the outside wall portion. The space between the inside wall portion and the outside wall portion is a space for collecting and exhausting the processing liquid used for processing the substrate W, and the processing liquid collected in this space is exhausted through the drain groove. 
     The inside member  312  is a tubular member with an open upper end, and the upper portion (“upper-end side portion” or “upper-end portion”) of the inside member  312  extends inwardly and upwardly. Specifically, the upper portion extends diagonally upward toward the rotation axis a 1 . At the lower portion of the inside member  312  are formed a tubular inside peripheral wall portion extending downward along the inner peripheral surface of the upper portion and a tubular outside peripheral wall portion extending downward along the outer peripheral surface of the upper portion. With the bottom member  311  and the inside member  312  close to each other, the outside wall portion of the bottom member  311  is accommodated between the inside peripheral wall portion and the outside peripheral wall portion of the inside member  312 . The processing liquid or the like caught by the upper portion of the inside member  312  is drained through the bottom member  311 . 
     The outside member  313  is a tubular member with an open upper end and is provided outside of the inside member  312 . The upper portion (“upper-end side portion” or “upper-end portion”) of the outside member  313  extends inwardly and upwardly. Specifically, the upper portion extends diagonally upward toward the rotation axis a 1 . The lower portion extends downward along the outside peripheral wall portion of the inside member  312 . The processing liquid or the like caught by the upper portion of the outside member  313  is drained from a gap between the outside peripheral wall portion of the inside member  312  and the lower portion of the outside member  313 . 
     The splash guard  31  is provided with a guard drive mechanism (“elevation drive”)  32  that moves the splash guard  31  upward or downward. The guard drive mechanism  32  is configured of, for example, a stepping motor. In this embodiment, the guard drive mechanism  32  independently moves the three members  311 ,  312 , and  313  of the splash guard  31  upward or downward. 
     The inside member  312  and the outside member  313  are individually moved between their upper positions and lower positions through driving of the guard drive mechanism  32 . Herein, the respective upper positions of the members  312  and  313  are positions at which the upper edge portions of the  312  and  313  are arranged lateral to and above the substrate W held on the spin chuck  21 . On the other hand, the respective lower positions of the members  312  and  313  are positions at which the upper edge portions of the members  312  and  313  are arranged below the upper surface of the spin chuck  21 . The upper position (lower position) of the outside member  313  is located slightly above the upper position (lower position) of the inside member  312 . The inside member  312  and the outside member  313  are moved upward or downward simultaneously or successively so as not to come into contact with each other. The bottom member  311  is driven by the guard drive mechanism  32  between a position at which the inside wall portion of the bottom member  311  is accommodated in the inside space of the flanged member  241  provided to the casing  24  and a position below the above-mentioned position. It should be noted that the guard drive mechanism  32  is electrically connected to the control unit  130  and operates under the control of the control unit  130 . That is to say, the position of the splash guard  31  (specifically, the respective positions of the bottom member  311 , the inside member  312 , and the outside member  313 ) is controlled by the control unit  130 . 
     Surface Protection Unit  4   
     The surface protection unit  4  includes a gas discharge mechanism (also referred to as a “gas discharge mechanism for peripheral portion” or a “gas discharge unit”)  440  that discharges gas flows of an inert gas such that the gas flows come into contact with the peripheral portion of the upper surface of the substrate W held and being rotated on the spin chuck  21 . The gas discharge mechanism  440  includes gas discharge mechanisms  441  and  442 . The gas discharge mechanisms  441  and  442  discharge an inert gas as, for example, gas-column-shaped gas flows G 1  and G 2 . The gas discharge mechanism  442  discharges the gas flow G 2  of the inert gas such that the gas flow G 2  comes into contact with a position (“second position”) P 2  upstream from a position (“first position”) P 1 , at which the gas flow G 1  discharged from the gas discharge mechanism  441  comes into contact with the peripheral portion of the substrate W, in the direction of rotation of the substrate W. 
     The surface protection unit  4  further includes a gas discharge mechanism (also referred to as a “gas discharge mechanism for central portion” or “another gas discharge unit”)  443  that discharges a gas flow G 3  of the inert gas onto the center or its vicinity of the upper surface of the substrate W held and being rotated on the spin chuck  21 . The surface protection unit  4  discharges the gas flows G 1  to G 3  of the inert gas onto the upper surface of the substrate W respectively from the gas discharge mechanisms  441  to  443 , thereby protecting a to-be-protected region (“device region”) S 4  ( FIG. 4 ) of the upper surface of the substrate W from, for example, the processing liquid discharged so as to come into contact with an annular processing region S 3  ( FIG. 4 ) defined by the peripheral portion of the upper surface of the substrate W. The to-be-protected region S 4  is a region of the upper surface of the substrate W except for the processing region S 3 . 
     The gas discharge mechanism  440  includes a nozzle head  48 . The gas discharge mechanism  443  includes a nozzle head  49 . The nozzle heads  48  and  49  are attached to the distal ends of elongated arms  61  and  62  of the nozzle moving mechanism  6  described below. The arms  61  and  62  extend along the horizontal plane. The nozzle moving mechanism  6  moves the arms  61  and  62  respectively to move the nozzle heads  48  and  49  between their processing positions and retreat positions. 
     The nozzle head  48  includes nozzles  41  and  42  and a holding member holding these nozzles. The holding member is formed of, for example, a plate-shaped member extending along the horizontal plane and a protruding member protruding upward from one end of the plate-shaped member, which are bonded together, and has an L-shaped cross-sectional shape. The protruding member has a distal end attached to the distal end of the arm  61  and protrudes more in the extension direction of the arm  61  than the proximal end of the arm  61  relative to the distal end of the arm  61 . The nozzles  41  and  42  are held by the plate-shaped member while passing through the plate-shaped member vertically. The nozzles  41  and  42  each have a distal end portion (lower end portion) protruding downward from the lower surface of the plate-shaped member and an upper end portion protruding upward from the upper surface of the plate-shaped member. The upper ends of the nozzles  41  and  42  are connected respectively with first ends of pipes  471  and  472 . Second ends of pipes  471  and  472  are connected respectively to gas supply sources  451  and  452 . At some midpoint in the pipe  471 , a flow rate controller  481  and an on/off valve  461  are provided sequentially from the gas supply source  451  side; at some midpoint in the pipe  472 , a flow rate controller  482  and an on/off valve  462  are provided sequentially from the gas supply source  452  side. 
     When the nozzle moving mechanism  6  arranges the nozzle head  48  at its processing position, the outlet of the nozzle  41  is opposed to a part of a rotation path of the peripheral portion of the substrate W rotated by the rotary holding mechanism  2 , and the outlet of the nozzle  42  is opposed to another part of the rotation path. 
     With the nozzle head  48  arranged at the processing position, the nozzles  41  and  42  are supplied with an inert gas (in the illustrated example, nitrogen (N 2 ) gas) respectively from the gas supply sources  451  and  452 . The nozzle  41  discharges the gas flow G 1  of the supplied inert gas from above such that the gas flow G 2  comes into contact with the position P 1  defined in the rotation path of the peripheral portion of the substrate W. The nozzle  41  discharges the gas flow G 1  in a predetermined direction through the outlet such that the discharged gas flow G 1  arrives at the position P 1  and then flows from the position P 1  toward the periphery of the substrate W. The nozzle  42  discharges the gas flow G 2  of the supplied inert gas from above such that the gas flow G 2  comes into contact with the position P 2  (“second position”) ( FIG. 4 ) defined in the rotation path. The nozzle  42  discharges the gas flow G 2  in a predetermined direction through the outlet such that the discharged gas flow G 2  arrives at the position P 2  and then flows from the position P 2  toward the periphery of the substrate W. 
     The substrate W has a radius of, for example, 150 mm. The “peripheral portion” of the substrate W is an annular portion with a width D 2  from the periphery of the substrate W. The width D 2  of the peripheral portion is, for example, 3 to 30 mm. The processing region S 3  is an annular portion with a width D 3  from the periphery of the substrate W. The width D 3  of the processing region S 3  is, for example, 1 to 5 mm. The processing region S 3  is a partial periphery-side region of the peripheral portion of the to-be-processed surface of the substrate W. 
     A liquid flow L 1  of a processing liquid discharged from a nozzle head  50  of the processing unit  5 , which will be described below, comes into contact with a position (“landing position”) PL 1  ( FIG. 4 ) defined in the rotation path of the peripheral portion on the upper surface of the substrate W. A width D 1  of the liquid flow L 1  in the radial direction of the substrate W is, for example, 0.5 to 2.5 mm. The nozzle head  50  can selectively discharge the liquid flow L 1  of the processing liquid from each of a plurality of nozzles  51   a  to  51   d . The position PL 1  slightly varies depending on the arrangements of the nozzles  51   a  to  51   d  and the direction in which the processing liquid is discharged. The position P 1  is located upstream from the position PL 1  corresponding to any of the nozzles  51   a  to  51   d  in the direction of rotation of the substrate W along the circumferential direction of the substrate W. The position P 2  is located upstream from the position P 1  in the direction of rotation of the substrate W along the circumferential direction of the substrate W. 
     That is to say, the gas discharge mechanism  440  discharges the gas flow (“first gas flow”) G 1  of the inert gas from above toward the position P 1  upstream from the position PL 1 , with which the processing liquid discharged from the processing unit  5  comes into contact, in the direction of rotation of the substrate W along the circumferential direction of the substrate W in the rotation path of the peripheral portion of the substrate W. The gas discharge mechanism  440  discharges the gas flow G 1  in a predetermined direction such that the discharged gas flow G 1  flows from the position P 1  toward the periphery of the substrate W. Also, the gas discharge mechanism  440  discharges the gas flow (“second gas flow”) G 2  of the inert gas from above toward the position P 2  upstream from the position P 1  in the direction of rotation of the substrate W along the circumferential direction of the substrate W in the rotation path. The gas discharge mechanism  440  discharges the gas flow G 2  in a predetermined direction such that the discharged gas flow G 2  flows from the position P 2  toward the periphery of the substrate W. 
     The nozzle head  49  of the gas discharge mechanism  443  includes a columnar member  93  attached to the lower surface of the distal end portion of the arm  62 , a disc-shaped shielding plate  90  attached to the lower surface of the columnar member  93 , and a cylindrical nozzle  43 . The axis line of the columnar member  93  coincides with the axis line of the shielding plate  90 , and each axis line extends vertically. The lower surface of the shielding plate  90  extends along the horizontal plane. The nozzle  43  passes through the columnar member  93  and the shielding plate  90  vertically such that the axis line of the nozzle  43  coincides with the axis lines of the shielding plate  90  and the columnar member  93 . The upper end of the nozzle  43  further passes through the distal end portion of the arm  62  to be open to the upper surface of the arm  62 . The upper opening of the nozzle  43  is connected with a first end of the pipe  473 . A second end of the pipe  473  is connected to the gas supply source  453 . At some midpoint in the pipe  473  are provided a flow rate controller  483  and an on/off valve  463  sequentially from the gas supply source  453  side. The lower end of the nozzle  43  is open to the lower surface of the shielding plate  90 . The opening is an outlet of the nozzle  43 . 
     When the nozzle moving mechanism  6  arranges the nozzle head  49  at its processing position, the outlet of the nozzle  43  is opposed to the center and its vicinity of the upper surface of the substrate W. In this state, the nozzle  43  is supplied with an inert gas (in the illustrated example, nitrogen (N 2 ) gas) from the gas supply source  453  through the pipe  473 . The nozzle  43  discharges the supplied inert gas as a gas flow G 3  of the inert gas onto the center or its vicinity of the upper surface of the substrate W. The gas flow G 3  spreads radially toward the periphery of the substrate W from above the central portion of the substrate W. Specifically, the gas discharge mechanism  443  discharges an inert gas from above the central portion of the upper surface of the substrate W to generate a gas flow spreading toward the periphery of the substrate W from above the central portion. 
     Each of the flow rate controllers  481  to  483  includes a flowmeter that detects a flow rate of a gas flowing through each of the pipes  471  to  473  in which the flow rate control unit is provided and a variable valve that can adjust the flow rate of the gas. The control unit  130  controls an open/close amount of the variable valve of each of the flow rate controllers  481  to  483  via a valve control mechanism (not shown) such that a flow rate detected by the flowmeter is equal to a target flow rate for each of the flow rate controllers  481  to  483 . The control unit  130  can set a target flow rate within a predetermined range in accordance with the preset setup information to freely control a flow rate of a gas passing through each of the flow rate controllers  481  to  483  in a predetermined range. The control unit  130  also controls the on/off valves  461  to  463  between the open state and the closed state via the valve control mechanisms. The control unit  130  thus controls how the gas flows G 1  to G 3  are discharged from the nozzles  41  to  43  (such as a discharge start timing, a discharge end timing, and a discharge flow rate). 
     How easily the residual processing liquid is blown off by the gas flows G 1  and G 2  varies depending on the film quality of the surface of the substrate W. Of the hydrophobic film quality and the hydrophilic film quality, the hydrophobic film quality is less likely to blow off the residual processing liquid, and the hydrophilic film quality is more likely to blow off the residual processing liquid. Therefore, how the gas flow G 1  is discharged is preferably set in accordance with the film quality of the surface of the substrate W. 
     Processing Unit  5   
     The processing unit  5  processes the processing region S 3  in the peripheral portion of the upper surface of the substrate W held on the spin chuck  21 . Specifically, the processing unit  5  supplies the processing liquid to the processing region S 3  of the substrate W held on the spin chuck  21 . 
     The processing unit  5  includes a processing liquid discharge mechanism  830 . The processing liquid discharge mechanism  830  discharges the liquid flow L 1  of the processing liquid such that the liquid flow L 1  comes into contact with a part of the peripheral portion (more specifically, the processing region S 3  of the peripheral portion) of the upper surface (to-be-processed surface) of the substrate W held and being rotated on the spin chuck  21 . The liquid flow L 1  is discharged so as to come into contact with the position PL 1  in the rotation path of the peripheral portion of the upper surface (more specifically, the processing region S 3 ). The liquid flow L 1  has a liquid columnar shape. The processing liquid discharge mechanism  830  includes the nozzle head  50 . The nozzle head  50  is attached to the distal end of an elongated arm  63  of the nozzle moving mechanism  6 . The arm  63  extends along the horizontal plane. The nozzle moving mechanism  6  moves the arm  63  to move the nozzle head  50  between its processing position and its retreat position. 
     The nozzle head  50  includes nozzles  51   a  to  51   d  and a holding member holding these nozzles. The holding member includes, for example, a plate-shaped member extending along the horizontal plane and a protruding member protruding upward from one end of the plate-shaped member, which are bonded together, and has an L-shaped cross-sectional shape. The distal end of the protruding member is attached to the distal end of the arm  63 , and the plate-shaped member protrudes further in the extension direction of the arm  63  beyond the proximal end of the arm  63  relative to the distal end of the arm  63 . The nozzles  51   a  to  51   d  are arranged in line along the extension direction of the arm  63  in order from the distal end side of the plate-shaped member. The nozzles  51   a  to  51   d  are held by the plate-shaped member while passing through the plate-shaped member vertically. The distal end portions (lower end portions) of the nozzles  51   a  to  51   d  protrude downward from the lower surface of the plate-shaped member, each of which includes an outlet at its distal end. The proximal end portions (upper end portions) of the nozzles  51   a  to  51   d  protrude upward from the upper surface of the plate-shaped member. 
     The nozzles  51   a  to  51   d  are connected with a processing liquid supply unit  83  that is a pipe system that supplies the processing liquid to these nozzles. Specifically, the upper ends of the nozzles  51   a  to  51   d  are connected with first ends of pipes  832   a  to  832   d  of the processing liquid supply unit  83 . Each of the nozzles  51   a  to  51   d  is supplied with the processing liquid from the processing liquid supply unit  83  and discharges the supplied processing liquid through the outlet at its distal end. The processing liquid discharge mechanism  830  discharges the liquid flow L 1  of the processing liquid in accordance with the control of the control unit  130  from one nozzle, which is determined by the control information set by the control unit  130 , among the nozzles  51   a  to  51   d . In the illustrated example, the liquid flow L 1  of the processing liquid is discharged from the nozzle  51   c.    
     Specifically, the processing liquid supply unit  83  is configured as a combination of an SC-1 supply source  831   a , a DHF supply source  831   b , an SC-2 supply source  831   c , a rinse liquid supply source  831   d , a plurality of pipes  832   a  to  832   d , and a plurality of on/off valves  833   a  to  833   d . SC-1, DHF, and SC-2 represent chemical solutions. The processing liquid discharge mechanism  830  is thus a chemical solution discharge unit that discharges the chemical solution onto the peripheral portion of the substrate W. 
     The SC-1 supply source  831   a  is a supply source that supplies SC-1. The SC-1 supply source  831   a  is connected to the nozzle  51   a  through the pipe  832   a  in which the on/off valve  833   a  is interposed. When the on/off valve  833   a  is opened, thus, the SC-1 supplied from the SC-1 supply source  831   a  is discharged from the nozzle  51   a.    
     The DHF supply source  831   b  is a supply source that supplies DHF. The DHF supply source  831   b  is connected to the nozzle  51   b  through the pipe  832   b  in which the on/off valve  833   b  is interposed. When the on/off valve  833   b  is opened, thus, the DHF supplied from the DHF supply source  831   b  is discharged from the nozzle  51   b.    
     The SC-2 supply source  831   c  is a supply source that supplies SC-2. The SC-2 supply source  831   c  is connected to the nozzle  51   c  through the pipe  832   c  in which the on/off valve  833   c  is interposed. When the on/off valve  833   c  is opened, thus, the SC-2 supplied from the SC-2 supply source  831   c  is discharged from the nozzle  51   c.    
     The rinse liquid supply source  831   d  is a supply source that supplies a rinse liquid. Herein, the rinse liquid supply source  831   d  supplies, for example, pure water as the rinse liquid. The rinse liquid supply source  831   d  is connected to the nozzle  51   d  through the pipe  832   d  in which the on/off valve  833   d  is interposed. When the on/off valve  833   d  is opened, thus, the rinse liquid supplied from the rinse liquid supply source  831   d  is discharged from the nozzle  51   d . The rinse liquid may be, for example, pure water, hot water, ozone water, magnetic water, regenerated water (hydrogen water), various organic solvents (e.g., ion water, isopropyl alcohol, or, IPA, and functional water such as CO 2  water). The nozzles  51   a ,  51   b , and  51   c  that respectively discharge SC-1, DHF, and SC-2 are also referred to as “processing liquid discharge nozzles” or “chemical solution discharge nozzles”. 
     The processing liquid supply unit  83  selectively supplies SC-1, DHF, SC-2, and a rinse liquid. When the processing liquid supply unit  83  supplies the processing liquid (SC-1, DHF, SC-2, or rinse liquid) from a corresponding nozzle among the nozzles  51   a  to  51   d , the nozzle discharges the liquid flow L 1  of the processing liquid such that the liquid flow L 1  comes into contact with the processing region S 3  of the peripheral portion of the upper surface of the substrate W being rotated. It should be noted that each of the on/off valves  833   a  to  833   d  of the processing liquid supply unit  83  is opened or closed under the control of the control unit  130  by a valve open/close mechanism (not shown) electrically connected to the control unit  130 . That is to say, the control unit  130  controls how the processing liquid is discharged from the nozzles of the nozzle head  50  (such as a type of the processing liquid, a discharge start timing, a discharge end timing, and a discharge flow rate). In other words, the processing liquid discharge mechanism  830  discharges, through the control of the control unit  130 , the liquid flow L 1  of the processing liquid such that the liquid flow L 1  comes into contact with the position PL 1  in the rotation path of the peripheral portion of the upper surface of the substrate W being rotated about the rotation axis a 1 . 
     Nozzle Moving Mechanism  6   
     The nozzle moving mechanism  6  is a mechanism that moves the nozzle heads  48  to  50  of the gas discharge mechanisms  440  and  443  and the processing liquid discharge mechanism  830  between their respective processing positions and retreat positions. 
     The nozzle moving mechanism  6  includes the arms  61  to  63  extending horizontally, nozzle bases  64  to  66 , and drives  67  to  69 . The nozzle heads  48  to  50  are respectively attached to the distal end portions of the arms  61  to  63 . 
     The proximal end portions of the arms  61  to  63  are connected to the upper end portions of the nozzle bases  64  to  66 . The nozzle bases  64  to  66  are arranged dispersedly around the casing  24 , with their axis lines extending vertically. The nozzle bases  64  to  66  extend vertically along their axis lines, each of which has a shaft rotatable about the axis line. The axis lines of the nozzle bases  64  to  66  coincide with the axis lines of the respective shafts. The upper end portions of the nozzle bases  64  to  66  are attached to the upper end portions of the respective shafts. The rotations of the shafts causes the upper end portions of the nozzle bases  64  to  66  to rotate about the axis lines of the respective shafts, that is, the axis lines of the nozzle bases  64  to  66 . The nozzle bases  64  to  66  are respectively provided with the drives  67  to  69  that rotate their shafts about the axis lines. The drives  67  to  69  each include, for example, a stepping motor. 
     The drives  67  to  69  respectively rotate the upper end portions of the nozzle bases  64  to  66  via the shafts of the nozzle bases  64  to  66 . Along with the rotations of the upper end portions, the nozzle heads  48  to  50  respectively rotate about the axis lines of the nozzle bases  64  to  66 . This causes the drives  67  to  69  to respectively move the nozzle heads  48  to  50  horizontally between their processing positions and retreat positions. 
     When the nozzle head  48  is arranged at the processing position, the outlet of the nozzle  41  is opposed to a part of the rotation path of the peripheral portion of the substrate W rotated by the rotary holding mechanism  2 , and the outlet of the nozzle  42  is opposed to another part of the rotation path. 
     When the nozzle head  49  is arranged at the processing position, the nozzle  43  is located above the center c 1  of the substrate W, and the axis line of the nozzle  43  coincides with the rotation axis a 1  of the spin chuck  21 . The outlet (lower opening) of the nozzle  43  is opposed to the central portion of the substrate W. The lower surface of the shielding plate  90  is opposed to the upper surface of the substrate W in parallel therewith. The shielding plate  90  is close to the upper surface of the substrate W in a contactless manner. 
     When the nozzle head  50  is arranged at the processing position, the nozzles  51   a  to  51   d  are arranged at the processing positions. More strictly, for example, in the case in which the nozzles  51   a  to  51   d  are arranged in a line along the extension direction of the arm  63 , the distance between the nozzle  51   a  and the periphery of the circular substrate W, the distance between the nozzle  51   b  and the periphery of the circular substrate W, the distance between the nozzle  51  and the periphery of the circular substrate W, and the distance between the nozzle  51   d  and the periphery of the circular substrate W slightly differ from each other. Even when the width of the processing region S 3  is small, the drive  69  adjusts the processing position of the nozzle head  50  in accordance with the nozzle that discharges the processing liquid among the nozzles  51   a  to  51   d  under the control of the control unit  130  such that the processing liquids selectively discharged from the nozzles  51   a  to  51   d  come into contact with the processing region S 3 . 
     The respective retreat positions of the nozzle heads  48  to  50  are positions that do not interfere with the transport path of the substrate W and do not interfere with each other. Each retreat position is, for example, a position outside of and above the splash guard  31 . 
     The drives  67  to  69  are electrically connected to the control unit  130  and operate under the control of the control unit  130 . The control unit  130  causes the nozzle moving mechanism  6  to arrange the nozzle heads  48  and  50  at the processing positions in accordance with the preset setup information such that the gas flows G 1  and G 2  and the liquid flow L 1  respectively come into contact with the positions P 1 , P 2 , and PL 1  in the rotation path of the peripheral portion of the substrate W. The positions P 1 , P 2 , and PL 1  are adjusted by changing the setup information. The control unit  130  causes the nozzle moving mechanism  6  to arrange the nozzle head  49  at the processing position in accordance with the setup information such that the gas flow G 3  comes into contact with the center of the substrate W or its vicinity. That is to say, the control unit  130  controls the positions of the nozzle heads  48  to  50 . Specifically, the control unit  130  controls the positions of the nozzles  41  to  43  and  51   a  to  51   d.    
     For the control of the positions P 1 , P 2 , and PL 1 , a central angle θ ( FIG. 4 ) is preferably set to not greater than 180°, more preferably not greater than 90°, and still more preferably not greater than 45°. The central angle θ is formed between the line segments, namely, a line segment connecting the center c 1  of the substrate W and the position PL 1  that is the landing position of the processing liquid, and a line segment connecting the center c 1  and the position P 2  with which the gas flow G 2  comes into contact. This is because a smaller central angle θ enables the residual processing liquid to stay at each portion of the processing region S 3  of the substrate W for a longer period of time, thereby improving a processing rate. 
     The liquid flow L 1  of the processing liquid, which has been discharged onto the position PL 1  in the rotation path of the peripheral portion of the upper surface of the substrate W, moves in the circumferential direction of the substrate W while adhering to the processing region S 3  in the form of a liquid film. During the movement, the central angle of the circular arc, which connects the portion to which the liquid film of the processing liquid adheres and the position PL 1  along the end face of the substrate W, becomes greater. The centrifugal force due to the rotation of the substrate W acts on the liquid film of the processing liquid during the movement. Thus, approximately 80% of the processing liquid is drained out of the substrate W until the central angle reaches 90°. This rate varies depending on, for example, the rotational speed and film quality of the substrate W, and the volume and viscosity of the processing liquid discharged. 
     If the width of the processing region S 3 , that is, the width for which the etching process or any other process is intended to be performed is 1 mm, the liquid flow L 1  of the processing liquid is preferably discharged so as to come into contact with a portion of the substrate W with a width in the range of 0.5 mm from the periphery of the substrate W. In this case, to efficiently remove the residual processing liquid from the substrate W while restricting splashes that arrive at the to-be-protected region S 4 , the gas flows G 1  and G 2  are preferably discharged such that the centers of the cross-sections of the gas flows G 1  and G 2  of the inert gas come into contact with the portion of the substrate W within the range of, for example, 4 to 8 mm from the periphery of the substrate W. The width of the liquid film of the residual processing liquid that adheres to the peripheral portion of the substrate W normally spreads to be larger than the width of the liquid flow L 1  of the processing liquid that comes into contact with the position PL 1 . Therefore, as described above, the widths of the gas flows G 1  and G 2  of the inert gas are preferably larger than the width of the liquid flow L 1  of the processing liquid that comes into contact with the peripheral portion of the substrate W. Specifically, the widths of the gas flows G 1  and G 2  of the inert gas are preferably set to be, for example, three to five times the width of the liquid flow L 1 . The residual processing liquid that adheres to the peripheral portion of the substrate W is thus efficiently drained out of the substrate W by the gas flows G 1  and G 2 . 
     Heating Mechanism  7   
     The heating mechanism  7  is provided below the peripheral portion of the lower surface of the substrate W. The heating mechanism  7  includes an annular heater  71  and an electric circuit (not shown) that supplies power to the heater  71  in accordance with the control of the control unit  130 . 
     The heater  71  is arranged annularly around the spin chuck  21  below the peripheral portion of the lower surface so as to be opposed to the portion, with which the upper surface of the spin chuck  21  is not in contact, of the lower surface of the substrate W in a contactless manner. The upper surface of the heater  71  is parallel to the lower surface of the substrate W. The heater  71  is held by a holding member (not shown) provided upright on the casing  24 . The heater  71  is provided to improve the processing rate of the substrate W with the processing liquid, and heats the peripheral portion of the substrate W from its lower surface side. The heating mechanism  7  further includes a moving mechanism (not shown) such as a motor. The moving mechanism moves the heater  71  upward or downward to arrange the heater  71  at the processing position or the retreat position below the processing position. The retreat position is a position at which the heater  71  does not interfere with the transport path for the substrate W when the substrate W is transferred to and from the substrate processing apparatus  1 . The heater  71  is supplied with power while being arranged at the processing position, and the heater  71  generates heat to heat the peripheral portion of the substrate W. 
     The electric circuit that supplies power to the heater  71  and the moving mechanism that moves the heater  71  upward or downward are electrically connected to the control unit  130 , and operate under the control of the control unit  130 . That is to say, the control unit  130  controls how the substrate W is heated by the heater  71  and the position of the heater  71 . 
     1-2. Discharge Directions of Gas Flows and Liquid Flow 
       FIGS. 5 and 6  are a schematic side view and a schematic top view, respectively, for explaining angles of dip α 1 , α 2 , and αL and angles of traverse β 1  and β 2  formed by the gas flows G 1  and G 2  and the liquid flow L 1  discharged from the nozzles  41 ,  42 , and  51   c  of the substrate processing apparatus  1 .  FIGS. 5 and 6  illustrate the nozzles  41 ,  42 , and  51   c  as a common nozzle and the gas flows G 1  and G 2  and the liquid flow L 1  as a common flow. The term “angle of dip” refers to an angle formed by the horizontal plane and the direction in which the gas flow G 1  (gas flow G 2 , liquid flow L 1 ) is discharged. The angle of dip is 90° when a gas flow or the like is discharged vertically downward or 0° when it is discharged horizontally. The term “angle of traverse” refers to an angle formed by the tangent on the end face of the substrate W closest to the position P 1  (P 2 , PL 1 ) at which the gas flow G 1  (gas flow G 2 , liquid flow L 1 ) comes into contact with the substrate W and the discharge direction in which the gas flow G 1  (gas flow G 2 , liquid flow L 1 ) is projected onto the substrate W. The angle of traverse is 0° when the discharge direction in the projection extends along the tangential direction or 90° when it extends along the radial direction of the substrate W. 
     The angles of dip α 1  and α 2  of the gas flows G 1  and G 2  are set within the range of 45° to 90°, and the angles of traverse β 1  and β 2  thereof are also set within the range of 45° to 90°. Preferably, the respective angles of dip α 1  and α 2  of the gas flows G 1  and G 2  are set to 45°, and the angles of traverse β 1  and β 2  thereof are set to 90°. The angles of dip α 1  and α 2  may differ from each other, and the angles of traverse β 1  and β 2  may differ from each other. 
     The angle of dip αL of the liquid flow L 1  is set within the range of 30° to 90°, and the angle of traverse β 3  thereof is set within the range of 0° to 45°. Preferably, the angle of dip αL and the angle of traverse βL are each set to 45°. 
       FIGS. 7 and 8  each illustrate an example of how the gas flows G 1  and G 2  of the inert gas and the liquid flow L 1  of the processing liquid are discharged. The circles indicated as the nozzles  41 ,  42 , and  51   c  represent the outlets of the nozzles  41 ,  42 , and  51   c  which are projected onto the substrate W. Although the shape of the projected outlet varies depending on the shape, direction, or the like of the outlet, it is indicated as a circle. The regions of the substrate W with which the gas flows G 1  and G 2  and the liquid flow L 1  come into contact are indicated as the respective circles surrounding the positions P 1 , P 2 , and PL 1 . The position P 1  is located upstream from the position PL 1  in the direction of rotation of the substrate W, and the position P 2  is located upstream from the position P 1  in the direction of rotation of the substrate W. 
     In the example illustrated in  FIG. 7 , the outlets of the nozzles  41  and  42  are arranged along the radial direction of the substrate W. The gas flow G 1  discharged from the nozzle  41  comes into contact with the position P 1 , and the gas flow G 2  discharged from the nozzle  42  comes into contact with the position P 2 . The positions of the outlets of the nozzles  41  and  42  may differ from each other in the radial direction of the substrate W, as described above. 
     In the example illustrated in  FIG. 8 , the gas flow G 1  and the gas flow G 2  are discharged at different angles of traverse. The outlets of the nozzles  41  and  42  are located at the positions different from each other along the direction of rotation of the substrate W. The outlet of the nozzle  42  is located upstream from the outlet of the nozzle  41  in the direction of rotation of the substrate W. In the example of  FIG. 8 , specifically, the gas flow G 1  is discharged at an angle of traverse of 90°, and the gas flow G 2  is discharged at an angle of traverse of 45°. In other words, the angle of traverse of the gas flow G 2  is smaller than the angle of traverse of the gas flow G 1 . In this case, the gas flow G 2  has the speed components, namely, a speed component directed along the diameter of the substrate W toward the outside of the substrate W, and a speed component directed along the circumferential direction of the substrate W toward the downstream side in the direction of rotation. Thus, as similarly to the gas flow G 1 , for example, a difference in speed between the residual processing liquid and the gas flow G 2  in the direction of rotation of the substrate W is smaller than in the case in which the gas flow G 2  is discharged at an angle of traverse of 90°. The gas flow G 2  thus drains the residual processing liquid out of the substrate W while restricting the generation of splashes when the gas flow G 2  comes into contact with the liquid film of the residual processing liquid, thus reducing the thickness of the liquid film of the residual processing liquid. 
     1-3. Restriction of Splashes 
     The processing liquid discharge mechanism  830  of the substrate processing apparatus  1  discharges the liquid flow L 1  of the processing liquid such that the liquid flow L 1  comes into contact with the position PL 1  in the rotation path of the peripheral portion of the upper surface of the substrate W being rotated. The discharged liquid flow L 1  adheres to the position of discharge on the peripheral portion of the upper surface (more strictly, processing region S 3 ) of the substrate W in the form of a liquid film, and moves in the circumferential direction of the substrate W together with the peripheral portion of the substrate W. 
     A gas flow is caused to come into contact with such a liquid film of the residual processing liquid from above to generate a gas flow flowing from the position with which the gas flow has come into contact toward the outside of the substrate W, thereby blowing off a portion of the processing liquid, with which the gas flow has come into contact, toward the outside of the substrate W. This results in a reduced thickness of the portion of the liquid film with which the gas flow comes into contact. As described above, the width of the gas flow of the inert gas is set to be larger than the width of the liquid flow L 1  of the processing liquid discharged onto the position PL 1 . In this case, the widths of the gas flows G 1  and G 2  are larger than the width of the liquid film of the residual processing liquid that adheres to the peripheral portion of the upper surface of the substrate W. This also causes the processing liquid to move from the position, with which the gas flow comes into contact, to the portions that are located upstream and downstream from the portion, with which the gas flow comes into contact, of the liquid film of the residual processing liquid in the direction of rotation of the substrate W (also merely referred to as “adjacent portions”), resulting in increased thicknesses of the liquid films of the adjacent portions. This causes the liquid film to become wavy at the portion with which the gas flow comes into contact and its adjacent portions. In this case, splashes normally occur mainly from the adjacent portions of the liquid film and scatter toward their surroundings. 
     The liquid at the portion with which the gas flow comes into contact is blown off more efficiently as the gas flow that comes into contact with a unit area of the surface of the liquid film has higher kinetic energy, thus reducing the thickness of the liquid film and increasing the film thicknesses of the adjacent portions that are adjacent to the portion with which the gas flow comes into contact. If the thickness of the liquid film of the residual processing liquid is constant, larger waves are thus generated in the liquid film as the gas flow that comes into contact with a unit area of the liquid film has higher kinetic energy, increasing an amount and a speed of the splashes of the residual processing liquid generated from the waves. 
     The thickness of the liquid film formed on the peripheral portion of the upper surface of the rotating substrate W has an upper limit, and thus, if the gas flow that comes into contact with the unit area of the liquid film has constant kinetic energy, the waves generated in the liquid film normally become larger as the liquid film is thicker. This increases an amount and a speed of the splashes generated from the waves. 
     If the thickness of the liquid film is small, splashes are less likely to occur even when the liquid is blown off momentarily by a gas flow with high kinetic energy, that is, a strong gas flow. On the other hand, if the thickness of the liquid film is large, splashes are likely to occur due to the liquid film becoming wavy. However, if a gas flow with low kinetic energy, that is, a weak gas flow is brought into contact with the liquid film, small waves are generated in the portion with which the gas flow comes into contact and its adjacent portions, thus enabling the liquid film to become thinner gradually while restricting splashes. 
     In other words, to efficiently drain the residual processing liquid out of the substrate W while restricting the generation of splashes of the residual processing liquid, the processing liquid needs to be drained out efficiently by bringing a gas flow with low kinetic energy (weak gas flow) into contact with the portion with a thick liquid film and bringing a gas flow with high kinetic energy (strong gas flow) into contact with the portion with a thin liquid film. It should be noted that the thickness of the liquid film of the residual processing liquid also varies depending on whether the surface of the substrate W is hydrophilic or hydrophobic. Specifically, if the substrate W has a hydrophilic surface, the residual processing liquid tends to spread across the surface of the substrate W, thus reducing the thickness of the liquid film. On the other hand, if the substrate W has a hydrophobic surface, the processing liquid rises from the surface of the substrate W, thus increasing the thickness of the liquid film. 
     The gas discharge mechanism  440  of the substrate processing apparatus  1  discharges the gas flows G 1  and G 2  of the inert gas to efficiently drain the residual processing liquid out of the substrate W while restricting the generation of splashes of the residual processing liquid. Specifically, the gas discharge mechanism  440  discharges the gas flows G 1  and G 2  such that the gas flow G 1  comes into contact with the liquid film of the residual processing liquid at the position P 1  upstream from the position PL 1  in the direction of rotation of the substrate W, and that the gas flow G 2  comes into contact with the liquid film of the residual processing liquid at the position P 2  further upstream from the position P 1 . The kinetic energy (more specifically, the kinetic energy of the gas flow discharged through the outlet per unit time) when the gas flow G 1  or G 2  is discharged is proportional to the product of the cross-sectional area of the outlet of the nozzle  41  or  42  and the cube of the flow speed in discharge. The kinetic energy of the gas flow that comes into contact with the unit area of the liquid film per unit time is also proportional to the cube of the flow speed of the gas flow. The discharge mechanism  440  discharges the gas flows G 1  and G 2  such that the kinetic energy of the gas flow G 2  when the gas flow G 2  is discharged is lower than the kinetic energy of the gas flow G 1  when the gas flow G 1  is discharged. More specifically, the gas discharge mechanism  440  discharges the gas flows G 1  and G 2  such that the kinetic energy of a portion of the gas flow G 2 , which is discharged from the unit cross-sectional area of the outlet per unit time, is lower than the kinetic energy of a portion of the gas flow G 1 , which is discharged from the unit cross-sectional area of the outlet per unit time. 
     In the substrate processing apparatus  1 , the gas flow G 2  with kinetic energy lower than that of the gas flow G 1  comes into contact with the liquid film of the residual processing liquid at the position P 2  earlier than the gas flow G 1 . Thus, the film thickness of the residual processing liquid can be reduced while restricting the generation of splashes that arrive at the to-be-protected region S 4  (more strictly, splashes with speed at which splashes can arrive at the to-be-protected region S 4 ) from the wave generated on the liquid film by the gas flow G 2 . 
     Then, at the position P 1  downstream from the position P 2 , the gas flow G 1  comes into contact with the liquid film of the processing liquid with a reduced film thickness. The gas flow G 1 , which has higher kinetic energy than the gas flow G 2 , can drain the residual processing liquid out of the substrate W more efficiently. The processing liquid is thinner than in the case in which the gas flow G 2  comes into contact with the processing liquid, resulting in a smaller wave generated in the liquid film by the gas flow G 1 . The gas flow G 1  thus drains most of the residual processing liquid out of the substrate W while restricting the generation of splashes that arrive at the to-be-protected region S 4 . 
     This restricts a collision of a fresh processing liquid, which is discharged so as to come into contact with the position PL 1  downstream from the position P 1 , with the residual processing liquid. The peripheral portion of the upper surface of the substrate W is thus processed while restricting the processing liquid from entering the to-be-protected region S 4  of the upper surface of the substrate W. The kinetic energy of the gas flow G 1  (strictly, the kinetic energy of a portion of the gas flow of the gas flow G 1 , which is discharged per unit time from the unit cross-sectional area of the nozzle  41 ) is preferably set to, for example, 1.2 to 8 times the kinetic energy of the gas flow G 2  (strictly, the kinetic energy of a portion of the gas flow G 2 , which is discharged from the unit cross-sectional area of the nozzle  42  per unit time). In this case, the ratio of the kinetic energy per unit volume of the gas flow is 1.2 to 4 times. 
     If the residual processing liquid is drained out of the substrate W at an extremely high speed, a part of the residual processing liquid may be scattered toward the substrate W by being reflected upon the splash guard  31  and arrive at the portion, onto which the gas flow has not been discharged, of the upper surface of the substrate W. The kinetic energy of the gas flow is thus preferably set such that the residual processing liquid reflected upon the splash guard  31  toward the substrate W will not arrive at the substrate W. 
     Herein, the flow rate of a gas flow is proportional to the product of the cross-sectional area and flow speed of the gas flow. Increasing the flow rate of the gas flow thus also increases the kinetic energy of the gas flow. The gas flows G 1  and G 2  can thus be discharged such that the flow rate of the gas flow when the gas flow G 2  is discharged is lower than the flow rate of the gas flow G 1  when the gas flow G 1  is discharged. For example, the flow rate of the gas flow G 1  is set to 1.1 to 2 times the flow rate of the gas flow G 2 . 
     Reducing the flow speed of the gas flow or reducing the cross-sectional area of the gas flow can also reduce the flow rate. Reducing the flow speed reduces the kinetic energy of the gas flow that comes into contact with a unit area of the liquid film of the residual processing liquid per unit time. Thus, the flow speed of the gas flow G 2  is preferably set to be lower than the flow speed of the gas flow G 1  to set the flow rate of the gas flow G 2  to be lower than the flow rate of the gas flow G 1 . In this case, the weak gas flow G 2  can be discharged in a wide range compared with the gas flow G 1  by setting the cross-sectional area of the gas flow G 2  to be larger than the cross-sectional area of the gas flow G 1 , thereby reducing the liquid film while restricting splashes from the liquid film with which the gas flow G 2  has come into contact. 
     The gas flow has higher kinetic energy as the gas flow has higher flow speed. The gas flows G 1  and G 2  can thus be discharged such that the flow speed of the gas flow G 2  when the gas flow G 2  is discharged is lower than the flow speed of the gas flow G 1  when the gas flow G 1  is discharged. For example, the flow speed of the gas flow G 1  is set to be 1.1 to 2 times the flow speed of the gas flow G 2 . 
     1-4. Another Example of Nozzle of Gas Discharge Mechanism 
       FIG. 9  ( FIG. 11 ) is a perspective view of the distal-end side portions (the portions including the outlets) of nozzles  41 X and  42 X ( 41 Y and  42 Y) as an example of the nozzles that can be included in the gas discharge mechanism  440  in place of the nozzles  41  and  42  of  FIG. 1 .  FIG. 10  ( FIG. 12 ) schematically illustrates the positions at which the gas flows G 1  and G 2  respectively discharged from the nozzles  41 X and  42 X ( 41 Y and  42 Y) come into contact with the peripheral portion of the substrate W. 
     The nozzle  41 X and the nozzle  42 X illustrated in  FIG. 9  each have a cylindrical outer shape. The diameter of the outlet of the nozzle  41 X is smaller than the diameter of the outlet of the nozzle  42 X, and the axis of the nozzle  41 X coincides with the axis of the nozzle  42 X. In other words, the side wall of the nozzle  41 X is surrounded by the side wall of the nozzle  42 X. The respective outlets of the nozzles  41 X and  42 X are opposed to the peripheral portion of the upper surface of the substrate W. The nozzle  41 X discharges the columnar gas flow G 1 , and the nozzle  42 X discharges the tubular gas flow G 2  having a ring-shaped cross section surrounding the gas flow G 1 . The gas flow G 2  flows along the axis line of the nozzle  42  while spreading outward from the axis line. The kinetic energy of the gas flow G 2  when the gas flow G 2  is discharged is lower than the kinetic energy of the gas flow G 1  when the gas flow G 1  is discharged. 
     The gas flow G 1  discharged from the nozzle  41 X comes into contact with the position P 1  upstream from the position PL 1  with which the liquid flow L 1  comes into contact, and a part of the gas flow G 2  discharged from the nozzle  42 X comes into contact with the position P 2  further upstream from the position P 1 . Although a part of the gas flow G 2  also comes into contact with the side downstream from the position P 1  with which the gas flow G 1  comes into contact, the residual processing liquid in the peripheral portion of the substrate W can be reduced while restricting splashes by a part of the gas flow G 2  that comes into contact with the position P 2  upstream from the position P 1  and the gas flow G 1  that comes into contact with the position P 1 . Thus, the utility of the substrate processing apparatus  1  is not impaired. The use of the nozzles  41 X and  42 X causes a part of the gas flow G 2  to come into contact with the substrate W again on the side downstream from the position P 1 , thereby further reducing the residual processing liquid. 
     The nozzles  41 Y and  42 Y illustrated in  FIG. 11  are tubular nozzles that are longer along the periphery of the substrate W, each of which has a circular-arc-shaped cross-section with a small width in the radial direction of the substrate W. The outlets of the nozzles  41 Y and  42 Y are opposed to the peripheral portion of the substrate W. The nozzles  41 Y and  42 Y are partitioned by a partition wall axially extended such that the cross-sections of the respective flow paths are adjacent to each other along the coaxial circular arc. 
     The nozzles  41 Y and  42 Y respectively discharge the gas flows G 1  and G 2  each having a circular-arc-shaped cross-section along the shape of the periphery of the substrate W. The gas flow G 2  is lower than the gas flow G 1  in the kinetic energy in discharge. 
     The gas flow G 1  discharged from the nozzle  41 Y comes into contact with the position P 1  upstream from the position PL 1  with which the liquid flow L 1  comes into contact, and the gas flow G 2  discharged from the nozzle  42 Y comes into contact with the position P 2  further upstream from the position P 1 . The gas flow G 2  with low kinetic energy can reduce the residual processing liquid while restricting splashes of the residual processing liquid that arrive at the to-be-protected region S 4 . Most of the residual processing liquid that has not been removed by the gas flow G 2  and has remained in the substrate W is removed from the substrate W by the gas flow G 1  with kinetic energy higher than that of the gas flow G 2 . The residual processing liquid also has a liquid film whose thickness has been reduced, thus restricting the generation of splashes that arrive at the to-be-protected region S 4  even when the gas flow G 1  comes into contact with the to-be-protected region S 4 . The gas flows G 1  and G 2  each come into contact with the liquid film in the form of a cross-sectional shape elongated in the circumferential direction of the substrate W, and thus, the kinetic energy of the gas flow G 1  and the kinetic energy of the gas flow G 2  are dispersed more than in the case in which the gas flows G 1  and G 2  come into contact with narrow areas. Moreover, the gas comes into contact with the area longer in the circumferential direction of the substrate W than in the case in which the gas flows G 1  and G 2  come into contact with narrow areas. Thus, even when the kinetic energy per unit area of each gas flow is reduced, each gas flow comes into contact with the liquid film of the residual processing liquid for a longer period of time, thus sufficiently removing the residual processing liquid. 
     1-5. Operation of Substrate Processing Apparatus 
       FIG. 13  is a flowchart illustrating an example operation in which the substrate processing apparatus  1  processes a substrate with a processing liquid. The operation of the substrate processing apparatus  1  will be described below with reference to  FIG. 13 . Before the operation illustrated in  FIG. 13 , the substrate W has been transferred into the substrate processing apparatus  1  to be held on the spin chuck  21 . The nozzle heads  48  to  50  have been arranged at the processing positions by the nozzle moving mechanism  6 , and the splash guard  31  has been arranged at the upper position by the guard drive mechanism  32 . 
     When the process illustrated in  FIG. 13  is started, the rotating mechanism  231  of the substrate processing apparatus  1  starts rotating the spin chuck  21  holding the substrate W (step S 110 ). The rotational speed of the substrate W is set to, for example, 1000 rotations per minute. 
     Then, the gas discharge mechanism  440  starts discharging the gas flows G 1  and G 2  of an inert gas from the nozzles  41  and  42  of the nozzle head  48 , and simultaneously, the gas discharge mechanism  443  starts discharging the gas flow G 3  of the inert gas from the nozzle  43  of the nozzle head  49  (step S 120 ). The nozzle  43  discharges the inert gas onto the central portion of the upper surface of the substrate W from above to generate the gas flow G 3  spreading from the central portion of the substrate W toward the periphery of the substrate W. The flow rate of the gas flow G 3  when the gas flow G 3  is discharged from the nozzle  43  is higher than the flow rates of the gas flows G 1  and G 2  when the gas flows G 1  and G 2  are discharged. 
     After the gas discharge mechanisms  440  and  443  have started discharging the gas flows G 1 , G 2 , and G 3 , the heating mechanism  7  starts heating the peripheral portion of the substrate W by the heater  71 . After the temperature of the peripheral portion of the substrate W has risen and become stable after a lapse of time, the processing liquid discharge mechanism  830  discharges the liquid flow L 1  of the processing liquid such that the liquid flow L 1  comes into contact with the peripheral portion of the upper surface of the substrate W (more specifically, the processing region S 3  of the peripheral portion of the upper surface on the side closer to the end face of the substrate W), thus processing the peripheral portion of the upper surface (step S 130 ). Specifically, the processing liquid discharge mechanism  830  discharges the liquid flow L 1  from one nozzle (in  FIG. 1 , the nozzle  51   c ) among the nozzles  51   a  to  51   d  in accordance with the control of the control unit  130 . The liquid flow L 1  is discharged so as to come into contact with the position PL 1  defined in the rotation path of the peripheral portion of the upper surface (more specifically, the processing region S 3 ) of the substrate W. The cross-sectional size and flow rate of the liquid flow L 1  are set in advance such that the width of the liquid film, which turns from the liquid flow L 2  and adheres to the peripheral portion of the substrate, is accommodated in the processing region S 3 . The liquid flow L 1  comes into contact with the position PL 1  and then forms a liquid film on the processing region S 3 . The liquid film of the processing liquid moves in the circumferential direction of the substrate W while adhering to the peripheral portion of the substrate W along with the rotation of the substrate W. 
     From the viewpoint of improving the processing rate of the substrate W, the discharged processing liquid preferably stays at the position of discharge in the processing region S 3  for the longest possible period of time. The central angle, which is formed between the straight line connecting the position PL 1  in the rotation path and the center c 1  of the substrate W and the straight line connecting the position onto which the liquid flow L 1  has been discharged and the center c 1 , gradually increases along with the rotation of the substrate W. For example, 80% of the processing liquid discharged onto the processing region S 3  is drained out of the substrate W mainly by the centrifugal force associated with the rotation of the substrate W while the substrate W rotates until the central angle reaches 90°. After that, the liquid-film-shaped processing liquid that has not been drained out and has remained at the substrate W also moves along with the rotation of the substrate W while being gradually drained out of the substrate W and simultaneously adhering to the processing region S 3 , thus contributing to processing of the substrate W during the process. 
     The gas flow G 1  (G 2 ), whose discharge has been started from the nozzle  41  ( 42 ) in step S 120 , comes into contact with the liquid film of the residual processing liquid at the position P 1  (P 2 ) upstream from the position PL 1  in the direction of rotation of the substrate W along the circumferential direction of the substrate W in the rotation path of the substrate W. The position P 2  is located upstream from the position P 1 . Subsequently, the gas flow G 1  (G 2 ) flows from the position P 1  (P 2 ) toward the periphery of the substrate W by, for example, its discharge direction and the centrifugal force associated with the rotation of the substrate W. In other words, the gas discharge mechanism  440  discharges the gas flow G 1  of the inert gas from above onto the position P 1  upstream from the position PL 1 , at which the processing liquid lands, in the direction of rotation of the substrate W in the rotation path of the substrate W, thereby directing the gas flow G 1  from the position P 1  toward the periphery of the substrate W. Additionally, the gas discharge mechanism  440  discharges the gas flow G 2  of the inert gas from above toward the position P 2  upstream from the position P 1  in the direction of rotation of the substrate W in the rotation path of the substrate W, thereby directing the gas flow G 2  from the position P 2  toward the periphery of the substrate W. 
     The gas flow G 3  discharged from the nozzle  43  of the gas discharge mechanism  443  spreads from the central portion of the substrate W toward the periphery of the substrate W due to the influence of, for example, the direction in which the gas flow G 3  is discharged and the centrifugal force associated with the rotation of the substrate W. In other words, the gas discharge mechanism  443  discharges the inert gas from above the central portion of the upper surface of the substrate W to generate the gas flow G 3  spreading from the central portion toward the periphery of the substrate W. 
     The gas flow G 2  first comes into contact with the liquid film of the residual processing liquid in the peripheral portion of the substrate W. The gas flow G 2  has low kinetic energy when it is discharged compared with the gas flow G 1 , thus draining the processing liquid out of the substrate while restricting the generation of splashes that arrive at the to-be-protected region S 4 . This reduces the film thickness of the residual processing liquid. The gas flow G 1  comes into contact with the liquid film of the processing liquid that has not been drained out of the substrate W by the gas flow G 2 , at the position P 1  downstream from the position P 2 . The gas flow G 1  has high kinetic energy when it is discharged compared with the gas flow G 2 , and thus, most of the remaining processing liquid is drained out of the substrate W by the gas flow G 1 . The liquid film of the residual processing liquid has been thinned by the gas flow G 2  before the gas flow G 1  comes into contact with the liquid film. This restricts the generation of splashes that arrive at the to-be-protected region S 4  even when the gas flow G 1  comes into contact with the liquid film of the residual processing liquid. 
     As described above, most of the processing liquid discharged at the position PL 1  so as to come into contact with the processing region S 3  of the substrate W is drained out of the substrate W during one rotation of the substrate W. This restricts the splashes generated due to a processing liquid, which is newly discharged onto the position PL 1 , coming into contact with the residual processing liquid. While discharging of the gas flows G 1  to G 3  and discharging of the liquid flow L 1  are performed simultaneously, the rotating mechanism  231  repeatedly rotates the substrate W in accordance with the control of the control unit  130 . For example, the gas flows G 1  to G 3  are discharged respectively at flow rates of 12 L/min, 4 L/min, and 30 L/min to 130 L/min. 
     When the control unit  130  detects a lapse of a processing time required for processing the substrate W, the processing liquid discharge mechanism  830  stops discharging the processing liquid. This completes the process of step S 130 . 
     The rotating mechanism  231  stops rotating the spin chuck  21  (step S 140 ), and the heating mechanism  7  stops heating the peripheral portion of the substrate W by the heater  71 . The gas discharge mechanisms  440  and  443  stop discharging the gas flows G 1  to G 3  (step S 150 ). As a result, the operation illustrated in  FIG. 13  ends. 
     After that, the nozzle moving mechanism  6  and the guard drive mechanism  32  respectively move the nozzle heads  48  to  50  and the splash guard  31  to the retreat positions. The substrate W is removed from the spin chuck  21  to be transferred from the substrate processing apparatus  1 . 
     Although the substrate processing apparatus  1  includes the nozzle  43  that discharges the gas flow G 3  of the inert gas, the substrate processing apparatus  1  may include no nozzle  43 . In such a case, the substrate processing apparatus  1  may include no arm  62  and no nozzle head  49 . 
     Although the nozzles  41  and  42  are held by the nozzle head  48  and moved together by the arm  61 , another configuration may be employed in which the nozzles  41  and  42  are held by different nozzle heads and moved individually by different arms. 
     Although the substrate processing apparatus  1  discharges the nitrogen gas as the gas flows G 1  to G 3 , at least one gas flow of the gas flows G 1  to G 3  may be an inert gas different from the inert gas of the other gas flows. 
     Although the nozzles  41  and  42  that respectively discharge the gas flows G 1  and G 2  of the inert gas and the nozzles that discharge the processing liquid are held by the different nozzle heads  48  and  50  in the substrate processing apparatus  1 , another configuration may be employed in which the nozzle  41 , the nozzle  42 , and the nozzles that discharge the processing liquid are held by the same nozzle head and moved together by an arm or the like. 
     The nozzles  41 Y and  42 Y, which are adjacent to each other, are separate nozzles. For example, one nozzle having an outlet elongated in the circumferential direction of the substrate may discharge the gas flow G 2  and the gas flow G 2  respectively from the upstream portion and the downstream portion thereof in the direction of rotation of the substrate W. Such nozzles are achieved by, for example, providing a structure that will serve as a resistance on the downstream side in the flow path such that the resistance experienced by the gas flowing through the upstream portion of the flow path is higher than that through the downstream portion. 
     Between the nozzles  41  and  42  or between the nozzles  41 Y and  42 Y, at least one additional nozzle may be provided that discharges a gas flow of an inert gas such that the gas flow comes into contact with the peripheral portion of the substrate W. The kinetic energy of the gas flow discharged from this at least one additional nozzle may be lower or higher than the kinetic energy of the gas flow G 2  discharged from the nozzle  42 . This at least one additional nozzle preferably discharges a gas flow such that the kinetic energy of the gas flow of the inert gas discharged onto the peripheral portion of the substrate W becomes higher successively from the upstream side to the downstream side in the direction of rotation of the substrate W. 
     In the substrate processing apparatus according to the first embodiment configured as described above, at the position P 2 , the gas flow G 2  with kinetic energy lower than that of the gas flow G 1  comes into contact with the liquid film of the residual processing liquid at the peripheral portion of the substrate W. This causes the residual processing liquid to be drained out of the substrate W while restricting the generation of splashes of the residual processing liquid that can arrive at the to-be-protected region S 4 , thus reducing the film thickness of the residual processing liquid. Consequently, the gas flow G 1  with high kinetic energy is brought into contact with the portion at which the film thickness of the residual processing liquid has been reduced at the position P 1  on the downstream side, thereby draining most of the residual processing liquid out of the substrate W while restricting the generation of splashes of the residual processing liquid that can arrive at the to-be-protected region S 4 . This restricts the generation of splashes that can arrive at the to-be-protected region S 4  of the substrate W due to a collision between a processing liquid newly discharged onto the position PL 1  on the further downstream side and the residual processing liquid. The peripheral portion of the upper surface of the substrate W is thus processed while restricting the processing liquid from entering the to-be-protected region S 4  of the upper surface of the substrate W. 
     In the substrate processing apparatus according to the first embodiment configured as described above, the flow rate of the second gas flow when the second gas flow is discharged is lower than the flow rate of the gas flow G 1  when the gas flow G 1  is discharged. The second gas flow thus drains the residual processing liquid out of the substrate W while restricting the generation of splashes that can arrive at the to-be-protected region S 4 , thereby reducing the film thickness of the residual processing liquid. 
     In the substrate processing apparatus according to the first embodiment configured as described above, the flow speed of the second gas flow when the second gas flow is discharged is lower than the flow speed of the gas flow G 1  when the gas flow G 1  is discharged. The second gas flow thus drains the residual processing liquid out of the substrate W while restricting the generation of splashes that can arrive at the to-be-protected region S 4 , thereby reducing the film thickness of the residual processing liquid. 
     In the substrate processing apparatus according to the first embodiment configured as described above, the gas discharge mechanism  443  discharges an inert gas from above the central portion of the upper surface of the substrate W to generate a gas flow spreading from above the central portion of the substrate W toward the periphery of the substrate W. The gas flow generated by the gas discharge mechanism  443  further restricts the splashes that are generated when the second gas flow, the gas flow G 1 , and a fresh processing liquid sequentially come into contact with the residual processing liquid from arriving at the to-be-protected region S 4 . 
     In the substrate processing apparatus according to the first embodiment configured as described above, the flow rate of a gas flow discharged from the gas discharge mechanism  443  when the gas flow is discharged is higher than the flow rate of any of the flow rate of the gas flow G 1  when the gas flow G 1  is discharged and the flow rate of the second gas flow when the second gas flow is discharged. A large amount of gas flow is supplied to the respective parts of the peripheral portion also in the case in which the gas flow generated by the gas discharge mechanism  443  spreads radially from the central portion of the substrate W toward the peripheral portion of the substrate W. 
     2. Second Embodiment 
     2-1. Configuration of Substrate Processing Apparatus  1 A 
     The configuration of a substrate processing apparatus  1 A will be described with reference to  FIGS. 2 to 4 and 14 .  FIGS. 14, 2, and 3  are views for explaining the configuration of the substrate processing apparatus  1 A according to an embodiment.  FIGS. 14 and 2  are a schematic side view and a schematic top view, respectively, of the substrate processing apparatus  1 A.  FIG. 3  is a schematic perspective view of the substrate processing apparatus  1 A as viewed from diagonally above.  FIG. 4  is a schematic top view of a substrate W illustrating an example of a positional relationship among positions at which a liquid flow of a processing liquid and gas flows of an inert gas that are discharged from the substrate processing apparatus  1 A come into contact with the peripheral portion of the substrate W. 
       FIGS. 14, 2, and 3  illustrate a state in which the substrate W is being rotated in a predetermined direction of rotation (the direction of the arrow AR 1 ) about a rotation axis a 1  by a spin chuck  21 , with nozzle heads  48  to  50  arranged at their respective processing positions. In  FIG. 2 , the nozzle heads  48  to  50  arranged at the retreat positions and the like are indicated by the phantom lines.  FIGS. 2 and 3  do not illustrate partial components of the substrate processing apparatus  1 A, such as a scatter prevention unit  3 . 
     The substrate processing apparatus  1 A includes a rotary holding mechanism  2 , the scatter prevention unit  3 , a surface protection unit  4 , a processing unit  5 , a nozzle moving mechanism  6 , a heating mechanism  7 A, and a control unit  130 A. These units  2  to  6  and  7 A are electrically connected to the control unit  130 A and operate in response to instructions from the control unit  130 A. The control unit  130 A is configured similarly to the control unit  130  of the substrate processing apparatus  1 . In the control unit  130 A, the CPU serving as a main control unit performs computations in accordance with the procedure described in the program. The control unit  130 A thus controls the respective units of the substrate processing apparatus  1 A. 
     The units  2  to  6  of the substrate processing apparatus  1 A are configured and operate similarly to those of the units  2  to  6  of the substrate processing apparatus  1 . The substrate processing apparatus  1 A includes the heating mechanism  7 A in place of the heating mechanism  7  of the substrate processing apparatus  1 . The description of the units  2  to  6  of the substrate processing apparatus  1 A will be omitted, and the heating mechanism  7 A will now be described. 
     Heating Mechanism  7 A 
     The heating mechanism  7 A is provided below the peripheral portion of the lower surface of the substrate W. The heating mechanism  7 A includes an annular heater  71 A extending in the circumferential direction of the substrate W along the peripheral portion of the lower surface of the substrate W, a gas discharge mechanism (“shielding gas discharge mechanism”)  444 , and an electric circuit (not shown) that supplies power to the heater  71 A in accordance with the control of the control unit  130 A. 
       FIGS. 15 to 17  are schematic top views of the heater  71 A of the heating mechanism  7 A.  FIG. 15  illustrates a heating element  73  and a heating flow path  74  of the heater  71 A. For easy viewing,  FIG. 16  does not illustrate the heating flow path  74  of  FIG. 15 , and  FIG. 17  does not illustrate the heating element  73  of  FIG. 15 . The heating element  73  is illustrated as a region in which the heating element  73  is arranged (arrangement region). The heating flow path  74  is arranged below the heating element  73 . 
       FIGS. 18 and 19  are schematic cross-sectional views of the heater  71 A of the heating mechanism  7 A.  FIG. 18  is a longitudinal cross-sectional view of the heater  71 A taken along the lines I-I and II-II of  FIG. 15 , and  FIG. 19  is a longitudinal cross-sectional view of the heater  71 A taken along the lines and IV-IV of  FIG. 15 . 
     The heater  71 A is arranged annularly (more specifically, in an annular belt shape) around the spin chuck  21  below the peripheral portion of the lower surface so as to be opposed to the portion, which is not in contact with the upper surface of the spin chuck  21 , of the lower surface of the substrate W in a contactless manner. The heater  71 A has an annular plate shape. An opposed surface (upper surface) S 7  of the heater  71 A is parallel to the lower surface of the substrate W. The opposed surface S 7  is opposed to the lower surface (that is, a surface opposite to the upper surface being a to-be-processed surface) of the substrate W with an interval of, for example, approximately 2 to 5 mm. 
     The heater  71 A is held by a holding member (not shown) provided upright on the casing  24 . The heater  71 A is provided to improve the processing rate of the substrate W with a chemical solution and heats the peripheral portion of the substrate W from the lower surface side. The heating mechanism  7 A further includes a moving mechanism (e.g., a motor, not shown). The moving mechanism moves the heater  71 A upward or downward to dispose the heater  71 A at the processing position or the retreat position below the processing position. The retreat position is a position at which the heater  71 A does not interfere with the transfer path of the substrate W when the substrate W is transferred to and from the substrate processing apparatus  1 A. The heater  71 A is supplied with power while being arranged at the processing position. The heater  71 A accordingly generates heat to heat the peripheral portion of the substrate W. 
     The gas discharge mechanism  444  supplies an inert gas to the heating flow path  74  of the heater  71 A. The inert gas is preheated by the heater  71 A while flowing through the heating flow path  74 . The gas discharge mechanism  444  discharges the heated inert gas into a space V 1  between the upper surface (opposed surface S 7 ) of the heater  71 A and the lower surface of the substrate W. The inert gas discharged into the space V 1  restricts the atmosphere around the heater  71 A from entering the space V 1  and also heats the substrate W. 
     The heater  71 A is a resistance heater including a body portion  72  made of silicon carbide (SiC) or ceramic and the heating element (e.g., a resistance heating element such as a nichrome wire)  73  built in the body portion  72 . The heating element  73  is arranged below an annular (more specifically, an annular-belt-shaped) portion of the opposed surface S 7  of the heater  71 A except for the outer peripheral portion and the inner peripheral portion of the heater  71 A, over the entire annular (more specifically, annular-belt-shaped) arrangement region defined along the annular portion. The arrangement region for the heating element  73  is parallel to the lower surface of the substrate W and the opposed surface S 7  of the heater  71 A. Preferably, the substrate W is uniformly heated with ease if the arrangement region for the heating element  73  is parallel to the lower surface of the substrate W. Inside the heater  71 A, a temperature sensor (not shown) is also arranged. The temperature sensor measures the temperature of the heater  71 A and transmits the measurement result to the control unit  130 A. The control unit  130 A controls the power supply to the heating element  73  based on the measurement result. 
     The heating flow path  74  is arranged along the heating element  73  below the heating element  73 . In other words, the heating flow path  74  is arranged opposite to the substrate W relative to the heating element  73 . In this case, the heating flow path  74  is not provided between the substrate W and the heating element  73 , thus enabling the substrate W to be heated uniformly. The heat radiation and heat transfer from the heating element  73  to the substrate W are not hindered by the inert gas flowing through the heating flow path  74 . The heating flow path  74  may be arranged between the substrate W and the heating element  73 . To consider that the heating flow path  74  is arranged along the heating element  73 , it suffices that the heating flow path  74  is arranged along the arrangement region for the heating element  73 . The respective portions of the heating flow path  74  can be uniformly heated with ease if the heating flow path  74  is arranged along the heating element  73 . Thee inert gas flowing through the each portion of the heating flow path  74  is thus uniformly heated with ease. 
     The body portion  72  of the heater  71 A includes, for example, a lower member  72   a , a middle member  72   b , and an upper member  72   c  sequentially layered from below to above. The members  72   a  to  72   c  are annular plate-shaped members extending in the circumferential direction of the substrate W along the peripheral portion of the lower surface of the substrate W. 
     On the upper surface of the lower member  72   a , a groove portion (“recess”) forming the heating flow path  74  is extended. The groove portion has a bottom surface and a pair of side surfaces provided upright at the opposite widthwise ends of the bottom surface. The bottom surface and the pair of side surfaces are a bottom surface and a pair of side surfaces, respectively, of the heating flow path  74 . 
     The middle member  72   b  is bonded onto the lower member  72   a  with, for example, bolts (not shown). The upper surface of the lower member  72   a  and the lower surface of the middle member  72   b  adhere closely to each other. The portion, which closes the groove formed in the upper surface of the lower member  72   a , of the lower surface of the middle member  72   b  is a ceiling surface of the heating flow path  74 . In the upper surface of the middle member  72   b , an annular and shallow recess in which the heating element  73  is to be arranged is provided along the circumferential direction of the lower member  72   a . The heating element  73  is arranged in the recess. The recess is an arrangement region for the heating element  73 . 
     The upper member  72   c  is bonded onto the middle member  72   b  in which the heating element  73  is arranged with, for example, bolts (not shown). The upper surface of the middle member  72   b  and the lower surface of the upper member  72   c  adhere closely to each other except for in the recess provided in the upper surface of the middle member  72   b . The upper surface of the upper member  72   c  is the opposed surface S 7  of the heater  71 A. 
     In the example illustrated in  FIG. 15 , the heating flow path  74  is repeatedly arranged as follows: it makes approximately one loop around the inner peripheral surface S 9  of the heater  71 A in the circumferential direction, is then doubled back toward the outer peripheral surface S 10  of the heater  71 A in the plane extending along the opposed surface S 7 , and makes approximately one loop around the heater  71 A in the opposite direction. Consequently, the heating flow path  74  is arranged across the inner peripheral surface S 9  of the heater  71 A and the outer peripheral surface S 10  of the heater  71 A so as to make approximately four loops by being doubled back each time it makes approximately one loop around the inner peripheral surface S 9  of the heater  71 A in the circumferential direction of the heater  71 A. The heating flow path  74  cuts across four locations of the longitudinal cross-section of the heater  71 A in the circumferential direction of the heater  71 A. The four locations are arranged sequentially at intervals along the radial direction of the heater  71 A. The innermost (innermost peripheral) portion, that is, the portion with the smallest diameter of the heating flow path  74  is, when seen through from above, arranged between the inner periphery of the heater  71 A and the inner periphery of the arrangement region for the heating element  73  along both of the inner peripheries. The outermost (outermost peripheral) portion, that is, the portion with the largest diameter of the heating flow path  74  is, when seen through from above, arranged between the outer periphery of the arrangement region for the heating element  73  and the outer periphery of the heater  71 A along both of the outer peripheries. 
     As described above, the arrangement region for the heating element  73  is parallel to the lower surface of the substrate W. The heating flow path  74  is arranged two-dimensionally along the heating element  73  below the heating element  73 . To consider that the heating flow path  74  is arranged two-dimensionally, it suffices that an imaginary plane in which the heating flow path  74  is entirely arranged can be grasped. If the heating flow path  74  is arranged two-dimensionally along the heating element  73 , the heating flow path  74  can be made longer, and the distance from each portion of the heating flow path  74  to the heating element  73  can be made uniform. This facilitates sufficient heating of the inert gas flowing through each portion of the heating flow path  74  by the heating element  73  and uniform heating of the inert gas flowing through each portion of the heating flow path  74  at each portion. 
     As a portion of the heating flow path  74 , which is arranged below the heating element  73  along the heating element  73 , is longer, the inert gas flowing through the heating flow path  74  is heated by the heating element  73  for a longer period of time. The path in which the heating flow path  74  is arranged may be, for example, various arrangement paths such as a path looping in the circumferential direction of the heater  71 A while meandering below the heating element  73 . Although the heating flow path  74  makes approximately four loops around the inner peripheral surface S 9  of the heater  71 A in the example illustrated in  FIG. 17 , the number of loops may be less than or more than four. Alternatively, the heating flow path  74  may be arranged along the heating element  73  one-dimensionally or three-dimensionally. To consider that the heating flow path  74  is arranged three-dimensionally, it suffices that a three-dimensional region in which the heating flow path  74  is entirely arranged can be grasped. 
     In the lower portion of the heater  71 A, an introduction hole  75  for introducing an inert gas into the heating flow path  74  is formed. The introduction hole  75  at its lower end is open to the lower surface of the lower member  72   a  and at its upper end is open to the bottom surface of an approximately central portion of the heating flow path  74  in the longitudinal direction of the heating flow path  74 . The lower end of the introduction hole  75  is connected with the second end of a pipe  474 . The introduction hole  75  is in communication with each of the pipe  474  and the heating flow path  74 . The inert gas supplied from the gas supply source  454  of the gas discharge mechanism  444  through the pipe  474  is introduced into the heating flow path  74  through the introduction hole  75 . 
     In the opposed surface S 7  of the heater  71 A, a plurality of (in the illustrated example, 12) outlets  78  and a plurality of (in the illustrated example, 12) outlets  79  are provided to be opposed to the lower surface of the substrate W. 
     The plurality of outlets  78  are provided in the outer peripheral portion of the heater  71 A, and the plurality of outlets  79  are provided in the inner peripheral portion of the heater  71 A. More specifically, the plurality of outlets  78  are, in a top view, distributed sparsely in the circumferential direction of the heater  71 A between the outer periphery of the heater  71 A and the outer periphery of the arrangement region for the heating element  73 . The plurality of outlets  79  are, in a top view, distributed sparsely in the circumferential direction of the heater  71 A between the inner periphery of the heater  71 A and the inner periphery of the arrangement region for the heating element  73 . Consequently, the flow paths (through holes  76  and  77 ) connecting the outlet for the inert gas and the heating flow path  74  can be arranged easily, thus easily achieving a configuration in which a gas is discharged from an outlet formed in the opposed surface S 7  of the heater  71 A including the heater  71 A. Also, the heater  71 A can be miniaturized easily. 
     The plurality of outlets  78  are connected with the outermost (outermost peripheral) portion of the heating flow path  74  through the plurality of through holes  76 . The plurality of outlets  79  are connected with the innermost (innermost peripheral) portion of the heating flow path  74  through the plurality of through holes  77 . The plurality of through holes  76  and  77  respectively pass through the upper member  72   c  and the middle member  72   b  vertically. The plurality of through holes  76  are open to the ceiling surface of the outermost portion of the heating flow path  74 . The plurality of through holes  77  are open to the ceiling surface of the innermost portion of the heating flow path  74 . 
     The gas discharge mechanism  444  includes a gas supply source  454 , the pipe  474 , a flow rate controller  484 , an on/off valve  464 , the introduction hole  75 , the heating flow path  74 , the plurality of through holes  76  and  77 , and the plurality of outlets  78  and  79 . The gas supply source  454  supplies an inert gas (in the illustrated example, nitrogen (N 2 ) gas). The pipe  474  is connected at a first end to the gas discharge mechanism  444  and at a second end to the introduction hole  75 . 
     At some midpoint in the pipe  474 , the flow rate controller  484  and the on/off valve  464  are provided sequentially from the gas supply source  454  side. The introduction hole  75 , the heating flow path  74 , the through hole  76 , and the through hole  77  are provided in the heater  71 A. The gas discharge mechanism  444  supplies an inert gas from the gas supply source  454  to the pipe  474 . The flow rate controller  484  controls the flow rate of the gas flowing through the pipe  474 . The inert gas is introduced through the pipe  474  and the introduction hole  75  into an approximately central portion of the heating flow path  74  in the longitudinal direction of the heating flow path  74 . The introduced inert gas is divided into two gas flows flowing in the opposite directions along the path of the heating flow path  74  to flow through the heating flow path  74 . 
     The gas that has flowed in one direction flows through the portion (specifically, the portion with the second smallest looping diameter) of the heating flow path  74  making approximately one loop around the heater  71 A below the heating element  73 . During the flowing, the gas is heated by the heating element  73  thereabove. Subsequently, the inert gas flows through the portion (the portion with the smallest looping diameter) closest to the inner peripheral surface S 9  of the heater  71 A. The portion of the heating flow path  74  closest to the inner peripheral surface S 9  is arranged slightly inward of the inner periphery of the heating element  73  (on the side closer to the rotary shaft  22 ), and thus, the inert gas is also heated when flowing through this flow path. The inert gas then passes through the plurality of through holes  77  to be discharged through the plurality of outlets  79  into the space V 1 . 
     The gas that has been introduced into the heating flow path  74  and then flowed in the other direction flows through the portion (the portion with the second largest looping diameter) of the heating flow path  74  making approximately one loop around the heater  71 A below the heating element  73 . During the flowing, the gas is heated by the heating element  73 . Subsequently, the inert gas flows through the outermost portion (the portion with the largest looping diameter) of the heating flow path  74 . The outermost portion is arranged slightly outward of the outer periphery of the heating element  73  (opposite to the rotary shaft  22 ), and thus, the inert gas is also heated when flowing through this portion. The inert gas then passes through the plurality of through holes  76  to be discharged into the space V 1  through the plurality of outlets  78 . 
     As described above, the inert gas discharged into the space V 1  is preheated by the heating element  73  while flowing through the heating flow path  74 . Thus, the gas can be heated sufficiently without another heater provided for heating the inert gas. 
     The flow rate controller  484  includes, for example, a flowmeter that detects the flow rate of a gas flowing through the pipe  474  and a variable valve that can adjust the flow rate of the gas in accordance with a valve open/close amount. The control unit  130 A controls the open/close amount of the variable valve of the flow rate controller  484  via a valve control mechanism (not shown) such that the flow rate detected by the flowmeter of the flow rate controller  484  is equal to a target flow rate. The control unit  130 A sets a target flow rate within a predetermined range in accordance with the predetermined setting information to freely control the flow rate of the gas passing through the flow rate controller  484  within the predetermined range. The control unit  130 A also controls the on/off valve  464  between the open state and the closed state via the valve control mechanism. 
     Thus, the control unit  130 A controls how the gas flow G 4  of the inert gas is discharged through the plurality of outlets  78  and  79  (such as a discharge start timing, a discharge end timing, and a discharge flow rate). 
     The electric circuit that supplies power to the heater  71 A and the moving mechanism that moves the heater  71 A upward or downward is electrically connected to the control unit  130 A and operates under the control of the control unit  130 A. In other words, the control unit  130 A controls how the heater  71 A heats the substrate W and the inert gas (such as the temperature of the substrate W and the temperature of the discharged inert gas) and also controls the position of the heater  71 A. 
     2-2. Action of Shielding Gas 
       FIG. 20  illustrates an example of the gas flow G 4  of the inert gas discharged into a space between the heater  71 A and the substrate. The heater  71 A radiates rays of heat H 1  onto the lower surface of the substrate W from the opposed surface S 7  by heat generation of the heating element  73 , thereby heating the substrate W. The inert gas supplied from the gas discharge mechanism  444  is introduced into the heating flow path  74  and is preheated by the heating element  73  while flowing through the heating flow path  74 . The heated gas passes through holes  76  and  77  to be discharged through the outlets  78  and  79  into the space V 1  as the gas flow G 4  of the inert gas. 
     The gas flow G 4  flows from each of the outlets  78  and  79  toward the periphery of the substrate W and the center of the substrate W. On the side close to the periphery of the substrate W relative to the heater  71 A and the side close to the center of the substrate W relative to the heater  71 A, an atmosphere G 9  of lower temperature than that of the gas flow G 4  is present. The gas flow G 4  discharged through the outlet  78  and directed toward the periphery of the substrate W restricts the atmosphere G 9  present on the side close to the periphery of the substrate W relative to the heater  71 A from entering the space V 1 . The gas flow G 4  discharged through the outlet  79  and directed toward the center of the substrate W restricts the atmosphere G 9  present on the side close to the center of the substrate W relative to the heater  71 A from entering the space V 1 . This restricts a temperature drop of the peripheral portion of the substrate W. Thus, the heating efficiency of the substrate W by the heater  71 A is restricted from dropping due to the atmosphere G 9 . The gas flow G 4 , which has been preheated, contributes to heating of the substrate W. 
     The inert gas discharged from the gas discharge mechanism  441  servers as a shielding gas to prevent the atmosphere G 9  from entering the space V 1 , as well as a heating gas to heat the substrate W. 
       FIG. 21  graphically illustrates an example relationship between the flow rate of the gas flow G 4  of the inert gas and the temperature of the peripheral portion of the substrate W. The flow rate of the gas flow G 4  of the inert gas (specifically, nitrogen gas) discharged onto the lower surface of the substrate W through the outlets  78  and  79  of the heater  71 A is varied in four ways: 80 L/min, 60 L/min, 40 L/min, and 20 L/min. The temperature of the peripheral portion of the substrate W in  FIG. 21  is the temperature of the portion of the substrate W, which is 3 mm inside of the periphery of the substrate W. The temperatures after 300 seconds from the start of discharging of the gas flow G 4  are measured. The exhaust pressure of a chamber that accommodates the substrate processing apparatus  1 A is 250 Pa. 
     As illustrated in  FIG. 21 , as the flow rate of the gas flow G 4  is higher, the temperature of the peripheral portion of the substrate W is higher. This reveals that by discharging the preheated gas flow G 4  through the outlets  78  and  79  of the heater  71 A, the atmosphere G 9  can be restricted from entering the space V 1 , thereby efficiently heating the substrate W by the heater  71 A. 
     2-3. Operation of Substrate Processing Apparatus 
       FIG. 22  is a flowchart illustrating an example operation in which the substrate processing apparatus  1 A processes a substrate with a processing liquid. The operation of the substrate processing apparatus  1 A will be described below with reference to  FIG. 22 . Before the operation illustrated in  FIG. 22 , the substrate W has been transferred to the substrate processing apparatus  1 A to be held on the spin chuck  21 . The nozzle heads  48  to  50  have been arranged at the processing positions by the nozzle moving mechanism  6 , and the splash guard  31  is arranged at the upper position by the guard drive mechanism  32 . 
     When the process illustrated in  FIG. 22  is started, the rotating mechanism  231  of the substrate processing apparatus  1 A starts rotating the spin chuck  21  holding the substrate W (step S 210 ). The rotational speed of the substrate W is set to, for example, 1000 rotations per minute. 
     Then, the gas discharge mechanism  440  starts discharging the gas flows G 1  and G 2  of the inert gas from the nozzles  41  and  42  of the nozzle head  48 , and the gas discharge mechanism  443  starts discharging the gas flow G 3  of the inert gas from the nozzle  43  of the nozzle head  49  (step S 220 ). The nozzle  43  discharges the inert gas onto the central portion of the upper surface of the substrate W from above to generate the gas flow G 3  spreading from the central portion of the substrate W toward the periphery of the substrate W. The flow rate of the gas flow G 3  when the gas flow G 3  discharged from the nozzle  43  is discharged is higher than the flow rates of the gas flows G 1  and G 2  when the gas flows G 1  and G 2  are discharged. 
     After the discharge of the gas flows G 1  to G 3  has been started, the heating mechanism  7 A starts heating the peripheral portion of the substrate W by the heater  71 A. The heater  71 A is heated to, for example, approximately 185°. The gas discharge mechanism  444  of the heating mechanism  7 A starts supplying the inert gas from the gas supply source  454  at a flow rate of, for example, 40 L/min to 60 L/min to start discharging the gas flow G 4  through the plurality of outlets  78  and  79  formed in the opposed surface S 7  of the heater  71 A (step S 230 ). The inert gas is heated to be higher than the processing temperature (e.g., 60° C. to 90° C.) of the substrate W. 
     After the temperature of the peripheral portion of the substrate W has risen and become stable after a lapse of time, the processing liquid discharge mechanism  830  discharges the liquid flow L 1  of the processing liquid (chemical solution) such that the liquid flow L 1  comes into contact with the peripheral portion of the upper surface of the substrate W (more specifically, the processing region S 3  of the peripheral portion of the upper surface on the side closer to the end face of the substrate W), thus processing the peripheral portion of the upper surface (step S 240 ). Specifically, the processing liquid discharge mechanism  830  discharges the liquid flow L 1  from one nozzle (in  FIG. 14 , the nozzle  51   c ) among the nozzles  51   a  to  51   d  in accordance with the control of the control unit  130 A. The liquid flow L 1  is discharged so as to come into contact with a position PL 1  defined in the rotation path of the peripheral portion of the upper surface of the substrate W (more specifically, the processing region S 3 ). The cross-sectional size and flow rate of the liquid flow L 1  are set in advance such that the width of the liquid film, which turns from the liquid flow L 1  and adheres to the peripheral portion of the substrate W, fits in the processing region S 3 . The liquid flow L 1  comes into contact with the position PL 1  and then forms a liquid film on the processing region S 3 . The liquid film of the processing liquid moves in the circumferential direction of the substrate W while adhering to the peripheral portion of the substrate W along with the rotation of the substrate W. 
     From the viewpoint of improving the processing rate of the substrate W, the discharged processing liquid preferably stays at the position of discharge in the processing region S 3  for the longest possible period of time. The central angle, which is formed between the straight line connecting the position PL 1  in the rotation path and the center c 1  of the substrate W and the straight line connecting the position onto which the liquid flow L 1  has been discharged and the center c 1 , gradually increases along with the rotation of the substrate W. For example, 80% of the processing liquid discharged onto the processing region S 3  is drained out of the substrate W mainly by the centrifugal force associated with the rotation of the substrate W while the substrate W rotates until the central angle reaches 90°. After that, the liquid-film-shaped processing liquid that has not been drained out and has remained in the substrate W also moves along the circumferential direction of the substrate W while being gradually drained out of the substrate W and simultaneously adhering to the processing region S 3 , thus contributing to processing of the substrate W during the process. 
     The gas flow G 1  (G 2 ), whose discharge has been started from the nozzle  41  ( 42 ) in step S 220 , comes into contact with the liquid film of the residual processing liquid at the position P 1  (P 2 ) upstream from the position PL 1  in the direction of rotation of the substrate W along the circumferential direction of the substrate W in the rotation path of the substrate W. The position P 2  is upstream from the position P 1 . Subsequently, the gas flow G 1  (G 2 ) flows from the position P 1  (P 2 ) toward the periphery of the substrate W by, for example, its discharge direction and the centrifugal force associated with the rotation of the substrate W. In other words, the gas discharge mechanism  440  discharges the gas flow G 1  of the inert gas from above onto the position P 1  upstream from the position PL 1 , at which the processing liquid lands, in the direction of rotation of the substrate W in the rotation path of the substrate W, thereby directing the gas flow G 1  from the position P 1  toward the periphery of the substrate W. Additionally, the gas discharge mechanism  440  discharges the gas flow G 2  of the inert gas from above toward the position P 2  upstream from the position P 1  in the direction of rotation of the substrate W in the rotation path of the substrate W, thereby directing the gas flow G 2  from the position P 2  toward the periphery of the substrate W. 
     The gas flow G 3  discharged from the nozzle  43  of the gas discharge mechanism  443  spreads from the central portion of the substrate W toward the periphery of the substrate W due to the influence of, for example, the direction in which the gas flow G 3  is discharged and the centrifugal force associated with the rotation of the substrate W. In other words, the gas discharge mechanism  443  discharges the inert gas from above the central portion of the upper surface of the substrate W to generate the gas flow G 3  spreading from the central portion toward the periphery of the substrate W. 
     The gas flow G 2  first comes into contact with the liquid film of the residual processing liquid in the peripheral portion of the substrate W. The gas flow G 2  has low kinetic energy when it is discharged compared with the gas flow G 1 , thus draining the processing liquid out of the substrate while restricting the generation of splashes that arrive at the to-be-protected region S 4 . This reduces the film thickness of the residual processing liquid. The gas flow G 1  comes into contact with the liquid film of the processing liquid that has not been drained out of the substrate W by the gas flow G 2  and has remained in the substrate W, at the position P 1  downstream from the position P 2 . The gas flow G 1  has high kinetic energy when it is discharged compared with the gas flow G 2 , and thus, most of the remaining processing liquid is discharged out of the substrate W by the gas flow G 1 . The liquid film of the residual processing liquid has been thinned by the gas flow G 2  before the gas flow G 1  comes into contact with the liquid film. This restricts the generation of splashes that arrive at the to-be-protected region S 4  even when the gas flow G 1  comes into contact with the liquid film of the residual processing liquid. 
     As described above, most of the processing liquid discharged at the position PL 1  so as to come into contact with the processing region S 3  of the substrate W is drained out of the substrate W during one rotation of the substrate W. This restricts the splashes generated due to a processing liquid, which is newly discharged onto the position PL 1 , coming into contact with the residual processing liquid. While discharging of the gas flows G 1  to G 3  and discharging of the liquid flow L 1  are performed simultaneously, the rotating mechanism  231  repeatedly rotates the substrate W in accordance with the control of the control unit  130 A. For example, the gas flows G 1  to G 3  are discharged respectively at flow rates of 12 L/min, 4 L/min, and 30 L/min to 130 L/min. 
     When the control unit  130 A detects a lapse of a processing time required for processing the substrate W, the processing liquid discharge mechanism  830  stops discharging the processing liquid. This completes the process of step S 240 . 
     The heating mechanism  7 A stops supplying power to the heater  71 A to stop heating the substrate W by the heater  71 A and stops discharging the gas flow G 4  by the gas discharge mechanism  444  (step S 250 ). 
     The rotating mechanism  231  stops rotating the spin chuck  21  (step S 260 ), and the heating mechanism  7 A stops heating the peripheral portion of the substrate W by the heater  71 A. The gas discharge mechanisms  440  and  443  stop discharging the gas flows G 1  to G 3  (step S 270 ). As a result, the operation illustrated in  FIG. 22  ends. 
     After that, the nozzle moving mechanism  6  and the guard drive mechanism  32  respectively move the nozzle heads  48  to  50  and the splash guard  31  to the retreat positions. The substrate W is removed from the spin chuck  21  to be transferred from the substrate processing apparatus  1 . 
     The gas discharge mechanism  444  discharges the gas flow G 4  through the plurality of outlets  78  and  79  provided in the heater  71 A, while the substrate W rotates. Thus, the gas discharge mechanism  444  may discharge the gas flow G 4  through a single outlet  78  and a single outlet  79  provided in the heater  71 A. Even when the gas flow G 4  is discharged from only one outlet of the outlet  78  and the outlet  79 , a temperature drop of the substrate W can be restricted more than in the case in which the gas flow G 4  is not discharged. A flow path for the inert gas may be provided between the opposed surface S 7  of the heater  71 A and the heating element  73  such that the gas flow G 4  may be discharged through the outlet that is open to above the heating element  73 . 
     The substrate processing apparatus  1 A discharges the chemical solution from the processing liquid discharge mechanism  830  onto the processing region S 3  of the upper surface (to-be-processed surface) of the substrate W and heats the substrate W from the lower surface of the substrate W by the heater  71 A opposed to the lower surface of the substrate W. Also, the gas discharge mechanism  444  discharges the gas flow G 4  of the heated inert gas into the space V 1  between the opposed surface S 7  of the heater  71 A and the lower surface of the substrate W. It should be noted that the to-be-processed surface may be the lower surface of the substrate W. In other words, the processing liquid discharge mechanism  830  may discharge the chemical solution onto the peripheral portion of the lower surface of the substrate W, the heater  71 A, which is opposed to the upper surface of the substrate W, may heat the substrate W, and the gas discharge mechanism  444  may discharge the gas flow G 4  into the space between the upper surface of the substrate W and the lower surface (opposed surface) of the heater  71 A. 
     The gas discharge mechanism  444  may discharge the inert gas preheated by, for example, another heater different from the heater  71 A into the space V 1 . Specifically, the gas discharge mechanism  444  may preheat the inert gas supplied from the gas supply source  454  by the other heater and, through the pipe outside of the heater  71 A, discharge the heated inert gas into the space V 1  from the nozzle outside of the heater  71 A. 
     The heater  71 A may be provided so as to cover the entire surface, which is opposite to the to-be-processed surface, of the substrate W. The heater  71 A can be provided between the lower surface of the substrate W and the upper surface of the spin chuck  21  when the spin chuck  21 , which includes a plurality of chuck pins, holds the substrate W such that the substrate W does not contact the upper surface of the spin chuck  21 . In this case, the heater  71 A is supported by a columnar support member passing through the inside of the rotary shaft  22  and the spin chuck  21 . 
     Although the substrate processing apparatus  1 A includes the nozzle  43  that discharges the gas flow G 3  of the inert gas, the substrate processing apparatus  1 A may include no nozzle  43 . In that case, the substrate processing apparatus  1 A may include no arm  62  and no nozzle head  49 . 
     Although the nozzles  41  and  42  are held by the nozzle head  48  and moved together by the arm  61 , another configuration may be employed in which the nozzles  41  and  42  are held by different nozzle heads and are moved individually by different arms. 
     Although the substrate processing apparatus  1 A discharges the nitrogen gas as the gas flows G 1  to G 4 , at least one gas flow of the gas flows G 1  to G 4  may be an inert gas different from the inert gas of the other gas flows. 
     Although the nozzles  41  and  42  that respectively discharge the gas flows G 1  and G 2  of the inert gas and the nozzles that discharge the processing liquid are held by the different nozzle heads  48  and  50  in the substrate processing apparatus  1 , another configuration may be employed in which the nozzle  41 , the nozzle  42 , and the nozzles that discharge the processing liquid are held by the same nozzle head and moved together by an arm or the like. 
     In the substrate processing apparatus according to the second embodiment configured as described above, the gas flow G 4  of the preheated inert gas is discharged into the space V 1  between the opposed surface S 7  of the heater  71 A and the surface (to-be-protected surface), which is opposite to the to-be-processed surface, of the substrate W. This restricts the atmosphere G 9  from entering the space V 1  to restrict a drop in the heating efficiency of the substrate W, and also restricts a drop in the heating efficiency also by the gas flow G 4  of the inert gas. Thus, the substrate W can be processed while being efficiently heated. 
     In the substrate processing apparatus according to the second embodiment configured as described above, the gas discharge mechanism  444  discharges the gas flow G 4  of the inert gas preheated by the heater  71 A. Thus, there is no need to separately provide the heater for heating the inert gas, reducing the cost of the substrate processing apparatus. 
     In the substrate processing apparatus according to the second embodiment configured as described above, the gas discharge mechanism  444  includes the heating flow path  74  arranged along the heating element  73  of the heater  71 A and discharges the inert gas heated by the heater  71 A when flowing through the heating flow path  74 . This improves the heating efficiency of the inert gas by the heater  71 A. 
     In the substrate processing apparatus according to the second embodiment configured as described above, the heating flow path  74  is arranged two-dimensionally along the heating element  73 , thus further improving the heating efficiency of the inert gas by the heater  71 A. 
     In the substrate processing apparatus according to the second embodiment configured as described above, the heating flow path  74  is arranged opposite to the substrate W relative to the heating element  73 , and thus, the heating element  73  efficiently heats both of the substrate W and the inert gas. 
     In the substrate processing apparatus according to the second embodiment configured as described above, the gas discharge mechanism  444  includes the outlets  78  and  79  respectively provided in the outer peripheral portion and the inner peripheral portion of the annular heater  71 A and discharges the inert gas through the outlets  78  and  79 . This effectively restricts the atmosphere G 1  around the heater  71 A from entering the space V 1  between the substrate W and the heater  71 A. The substrate W is therefore heated efficiently. 
     3. Third Embodiment 
     3-1. Configuration of Substrate Processing Apparatus  1 B 
     The configuration of a substrate processing apparatus  1 B will be described with reference to  FIGS. 23 to 27 .  FIGS. 23 to 25  are views for explaining the configuration of the substrate processing apparatus  1 B according to an embodiment.  FIGS. 23 and 24  are a schematic side view and a schematic top view, respectively, of the substrate processing apparatus  1 B.  FIG. 25  is a schematic perspective view of the substrate processing apparatus  1 B as viewed from diagonally above.  FIGS. 26 and 27  are a schematic top view and a schematic side view, respectively, of a substrate W, which illustrate an example of a positional relationship of the positions at which a liquid flow of a processing liquid and gas flows of an inert gas that are discharged from the substrate processing apparatus  1 B come into contact with the peripheral portion of the substrate W.  FIG. 26  is a top view schematically illustrating positions PL 1 , PL 2 , P 3 , and P 4  at which the processing liquid, rinse liquid, and inert gas discharged from the substrate processing apparatus  1 B come into contact with the peripheral portion of the substrate.  FIG. 27  is a schematic side view illustrating a state in which the nozzles individually discharge the processing liquid and the like onto the positions PL 1 , PL 2 , P 3 , and P 4 . 
       FIGS. 23 to 25  illustrate a state in which the substrate W is being rotated in a predetermined direction of rotation (the direction of the arrow AR 1 ) about a rotation axis a 1  by a spin chuck  21 , with nozzle heads  48 B,  49 , and  50  arranged at their respective processing positions. In  FIG. 24 , the nozzle heads  48 B,  49 , and  50  arranged at their retreat positions and the like are indicated by phantom lines.  FIGS. 24 and 25  do not illustrate partial components of the substrate processing apparatus  1 B, such as a scatter prevention unit  3 . 
     The substrate processing apparatus  1 B includes a rotary holding mechanism  2 , the scatter prevention unit  3 , a surface protection unit  4 B, a processing unit  5 , a nozzle moving mechanism  6 , a heating mechanism  7 B, a rear surface protection unit  8 , and a control unit  130 B. These units  2 ,  3 ,  4 B,  5 ,  6 ,  7 B, and  8  are electrically connected to the control unit  130 B and operate in response to instructions from the control unit  130 B. The control unit  130 B is configured similarly to the control unit  130  of the substrate processing apparatus  1 . In the control unit  130 B, the CPU serving as a main control unit performs computations in accordance with the procedure described in the program. The control unit  130 B thus controls the respective units of the substrate processing apparatus  1 B. 
     The units  2 ,  3 , and  5  of the substrate processing apparatus  1 B are configured and operate similarly to those of the units  2 ,  3 , and  5  of the substrate processing apparatus  1  ( 1 A). The nozzle moving mechanism  6  of the substrate processing apparatus  1 B, which is configured similarly to the nozzle moving mechanism  6  of the substrate processing apparatus  1  ( 1 A), moves an object different from an object moved by the nozzle moving mechanism  6  of the substrate processing apparatus  1  ( 1 A). The substrate processing apparatus  1 B includes the surface protection unit  4 B in place of the surface protection unit  4  of the substrate processing apparatus  1  ( 1 A) and includes the heating mechanism  7 B in place of the heating mechanism  7  ( 7 A) of the substrate processing apparatus  1  ( 1 A). The substrate processing apparatus  1 B further includes the rear surface protection unit  8 . The units  2 ,  3 , and  5  of the substrate processing apparatus  1 B will not be described here, and the units  4 B,  6 ,  7 B, and  8  will now be described. 
     Surface Protection Unit  4 B 
     The surface protection unit  4 B includes a gas discharge mechanism (also referred to as a “gas discharge mechanism for peripheral portion” or a “gas discharge unit”)  441  that discharges a gas flow of an inert gas such that the gas flow comes into contact with the peripheral portion of the upper surface of the substrate W held and being rotated on the spin chuck  21 . The gas discharge mechanism  441  discharges the inert gas as, for example, a gas-column-shaped gas flow G 1 . 
     The configuration and the like of the surface protection unit  4 B, which differ from those of the surface protection unit  4  of the substrate processing apparatus  1  ( 1 A), will be described below. Description of a similar configuration will be omitted appropriately. The components of the surface protection unit  4 B, whose description will be omitted, can be described in the description of the components bearing the same reference signs of the surface protection unit  4  described above, or can be described in the description of the surface protection unit  4  by replacing the reference signs of the components of the surface protection unit  4  and the like with the reference sings of the corresponding components of the surface protection unit  4 B and the like. The corresponding components bear reference sings combining numerals of the surface protection unit  4  and an alphabet “B”. 
     The surface protection unit  4 B further includes a gas discharge mechanism (also referred to as a “gas discharge mechanism for central portion” or “another gas discharge unit”)  443 . The gas discharge mechanism  443  is configured and operates similarly to the gas discharge mechanism  443  of the substrate processing apparatus  1  ( 1 A). The surface protection unit  4 B discharges gas flows G 1  and G 3  of an inert gas onto the upper surface of the substrate W respectively from the gas discharge mechanisms  441  and  443 , thereby protecting the to-be-protected region (“device region”) S 4  ( FIG. 26 ) of the upper surface of the substrate W from, for example, the processing liquid discharged so as to come into contact with the annular processing region S 3  ( FIG. 26 ) defined in the peripheral portion of the upper surface of the substrate W. 
     The gas discharge mechanism  441  includes a nozzle head  48 B. The gas discharge mechanism  443  includes the nozzle head  49 . The nozzle heads  48 B and  49  are attached to the distal ends of elongated arms  61  and  62  of the nozzle moving mechanism  6 . The arms  61  and  62  extend along the horizontal plane. The nozzle moving mechanism  6  moves the arms  61  and  62  to move the nozzle heads  48 B and  49  between their processing positions and retreat positions. 
     The nozzle head  48 B includes a nozzle (“gas discharge nozzle for to-be-processed surface”)  41  and a holding member holding the nozzle  41 . The holding member is configured similarly to the holding member in the nozzle head  48  of the substrate processing apparatus  1  ( 1 A) and is also similarly attached to the distal end of the arm  61  to hold the nozzle  41 . The upper end of the nozzle  41  is connected with a first end of the pipe  471 . A second end of the pipe  471  is connected to the gas supply source  451 . At some midpoint in the pipe  471 , a flow rate controller  481  and an on/off valve  461  are provided sequentially from the gas supply source  451  side. 
     Here, when the nozzle moving mechanism  6  arranges the nozzle head  48 B at its processing position, the outlet of the nozzle  41  is opposed to a part of the rotation path (“first rotation path”) of the peripheral portion of the upper surface of the substrate W rotated by the rotary holding mechanism  2 . 
     With the nozzle head  48 B arranged at the processing position, the nozzle  41  is supplied with an inert gas (in the illustrated example, a nitrogen (N 2 ) gas) from the gas supply source  451 . The nozzle  41  discharges the gas flow G 1  of the supplied inert gas from above such that the gas flow G 1  comes into contact with the position P 3  defined in the rotation path of the peripheral portion of the upper surface of the substrate W. The nozzle  41  discharges the gas flow G 1  through the outlet in a predetermined direction such that the gas flow G 1  reaches the position P 3  and then flows from the position P 3  toward the periphery of the substrate W. 
     A liquid flow L 1  of a processing liquid discharged from a nozzle head  50  of the processing unit  5  comes into contact with a position (“landing position”, “first position”) PL 1  ( FIG. 26 ) defined in the rotation path of the peripheral portion of the upper surface of the substrate W. A width D 1  of the liquid flow L 1  in the radial direction of the substrate W is, for example, 0.5 to 2.5 mm. The nozzle head  50  can selectively discharge the liquid flow L 1  of the processing liquid from each of a plurality of nozzles  51   a  to  51   d . The position PL 1  slightly varies depending on the arrangements of the nozzles  51   a  to  51   d  and the direction in which the processing liquid is discharged. The position P 3  with which the gas flow G 1  comes into contact is located upstream from the position P 1  corresponding to any of the nozzles  51   a  to  51   d  in the direction of rotation of the substrate W along the periphery of the substrate W. 
     That is to say, the gas discharge mechanism  441  discharges the gas flow (“first gas flow”) G 1  of the inert gas from above toward the position P 3  upstream from the position PL 1 , with which the processing liquid discharged from the processing unit  5  comes into contact, in the direction of rotation of the substrate W along the circumferential direction of the substrate W in the rotation path of the peripheral portion of the substrate W. The gas discharge mechanism  441  discharges the gas flow G 1  in a predetermined direction such that the discharged gas flow G 1  flows from the position P 3  toward the periphery of the substrate W. 
     The nozzle head  49  of the substrate processing apparatus  1 B is configured and operates similarly to the substrate processing apparatus  1  ( 1 A) described above. Flow rate control units  481  and  483  and the pipe  471  and a pipe  473  of the substrate processing apparatus  1 B are configured similarly to the flow rate control units  481  and  483  and the pipes  471  and  473  of the substrate processing apparatus  1  ( 1 A). The control unit  130 B controls the flow rate control units  481  and  483  and the on/off valve  461  and an on/off valve  463  similarly to the control unit  130  ( 130 A) of the substrate processing apparatus  1  ( 1 A) via a valve control mechanism (not shown). The control unit  130 B thus controls how the gas flows G 1  and G 3  are respectively discharged from the nozzles  41  and  43  (such as a discharge start timing, a discharge end timing, and a discharge flow rate). 
     How easily the residual processing liquid that remains on the upper surface of the substrate W is blown off by the gas flow G 1  varies depending on the film quality of the surface of the substrate W. Of the hydrophobic film quality and the hydrophilic film quality, the hydrophobic film quality is less likely to blow off the residual processing liquid, and the hydrophilic film quality is more likely to blow off the residual processing liquid. Therefore, how the gas flow G 1  is discharged is preferably set in accordance with the film quality of the surface of the substrate W. 
     Nozzle Moving Mechanism  6   
     The nozzle moving mechanism  6  is a mechanism that moves the nozzle heads  48 B,  49 , and  50  of the gas discharge mechanisms  441  and  443  and the processing liquid discharge mechanism  830  between their processing positions and retreat positions. 
     The nozzle moving mechanism  6  of the substrate processing apparatus  1 B is configured similarly to the nozzle moving mechanism  6  of the substrate processing apparatus  1  ( 1 A). The nozzle heads  48 B,  49 , and  50  are attached to the distal end portions of the arms  61  to  63  of the nozzle moving mechanism  6 . Drives  67  to  69  of the nozzle moving mechanism  6  respectively move the nozzle heads  48 B,  49 , and  50  horizontally between their processing positions and their retreat positions in accordance with the control of the control unit  130 B. 
     When the nozzle head  48 B is arranged at the processing position, the outlet of the nozzle  41  is opposed to a part of the rotation path of the peripheral portion of the substrate W rotated by the rotary holding mechanism  2 . The processing positions and retreat positions of the nozzle head  49  and the nozzle holding member  50  of the substrate processing apparatus  1 B are positions respectively similar to the processing positions and the retreat positions of the nozzle head  49  and the nozzle holding member  50  of the substrate processing apparatus  1  ( 1 A). 
     The respective retreat positions of the nozzle heads  48 B,  49 , and  50  of the substrate processing apparatus  1 B are positions similar to their respective retreat positions of the nozzle heads  48 ,  49 , and  50  of the substrate processing apparatus  1  ( 1 A). 
     The drives  67  to  69  are electrically connected to the control unit  130 B and operate under the control of the control unit  130 B. The control unit  130 B causes the nozzle moving mechanism  6  to arrange the nozzle heads  48 B and  50  at the processing positions in accordance with the preset setup information such that the gas flow G 1  and the liquid flow L 1  respectively come into contact with the positions P 3  and PL 1  in the rotation path of the peripheral portion of the substrate W. The positions P 3  and PL 1  are adjusted by changing the setup information. The control unit  130 B causes the nozzle moving mechanism  6  to arrange the nozzle head  49  at the processing position in accordance with the setup information such that the gas flow G 3  comes into contact with the center or its vicinity of the substrate W. That is to say, the control unit  130 B controls the positions of the nozzle heads  48 B,  49 , and  50 . Specifically, the control unit  130  controls the positions of the nozzles  41 ,  43 , and  51   a  to  51   d.    
     The liquid flow L 1  of the processing liquid, which has been discharged onto the position PL 1  in the rotation path of the peripheral portion of the upper surface of the substrate W, moves in the circumferential direction of the substrate W while adhering to the processing region S 3  in the form of a liquid film. During the movement, the central angle of the circular arc, which connects the portion to which the liquid film of the processing liquid adheres and the position PL 1  along the end face (“edge”) of the substrate W, becomes greater. The centrifugal force due to the rotation of the substrate W acts on the liquid film of the processing liquid during the movement. Thus, approximately 80% of the processing liquid is drained out of the substrate W until the central angle reaches 90°. This rate varies depending on, for example, the rotational speed and film quality of the substrate W, and the volume and viscosity of the processing liquid discharged. 
     If the width of the processing region S 3 , that is, the width with which the etching process or any other process is intended to be performed is 1 mm, the liquid flow L 1  of the processing liquid is preferably discharged so as to come into contact with the substrate W with a width in the range of 0.5 mm from the periphery of the substrate W. In this case, to efficiently remove the residual processing liquid from the substrate W while restricting splashes that arrive at the to-be-protected region S 4 , the gas flow G 1  is preferably discharged such that the center of the cross-section of the gas flow G 1  of the inert gas comes into contact with the substrate W within the range of, for example, 4 to 8 mm from the periphery of the substrate W. The width of the liquid film of the residual processing liquid that adheres to the peripheral portion of the substrate W normally spreads to be larger than the width of the liquid flow L 1  of the processing liquid that comes into contact with the position PL 1 . As described above, therefore, the width of the gas flow G 1  of the inert gas is preferably larger than the width of the liquid flow L 1  of the processing liquid that comes into contact with the peripheral portion of the substrate W. Specifically, the width of the gas flow G 1  of the inert gas is preferably set to be, for example, three to five times the width of the liquid flow L 1 . The residual processing liquid that adheres to the peripheral portion of the substrate W is thus efficiently drained out of the substrate W by the gas flow G 1 . 
     Heating Mechanism  7 B 
     The heating mechanism  7 B is provided below the peripheral portion of the lower surface of the substrate W. The heating mechanism  7 B includes an annular heater  71 B extending in the circumferential direction of the substrate W along the peripheral portion of the lower surface of the substrate W, a gas discharge mechanism (“shielding gas discharge mechanism”)  444 , and an electric circuit (not shown) that supplies power to the heater  71 B in accordance with the control of the control unit  130 B. The heating mechanism  7 B is configured similarly to the heating mechanism  7 A of the substrate processing apparatus  1 A except for that it includes the heater  71 B in place of the heater  71 A. 
       FIGS. 28 to 30  are schematic top views of the heater  71 B of the heating mechanism  7 B.  FIG. 28  illustrates a heating element  73 B and a heating flow path  74 B of the heater  71 A.  FIG. 29  does not illustrate the heating flow path  74 B of  FIG. 28  for easy viewing, and  FIG. 30  does not illustrate the heating element  73 B of  FIG. 28 . The heating element  73 B is illustrated as a region in which the heating element  73 B is arranged (arrangement region). The heating flow path  74 B is arranged below the heating element  73 B. The heater  71 B is configured similarly to the heater  71 A of the heating mechanism  7 A of the substrate processing apparatus  1 A except for that it includes the heating element  73 B and the heating flow path  74 B in place of the heating element  73  and the heating flow path  74  and that it has a recess  170  formed in the outer peripheral surface S 10  of the heater  71 B. 
       FIGS. 18 and 19  are schematic cross-sectional views of the heater  71 B of the heating mechanism  7 B.  FIG. 18  is a longitudinal cross-sectional view of the heater  71 B taken along the lines I-I and II-II of  FIG. 28 , and  FIG. 19  is a longitudinal cross-sectional view of the heater  71 B taken along the lines and IV-IV of  FIG. 28 . As illustrated in  FIGS. 18 and 19 , the structure of each cross-section of the heater  71 B taken along these cutting lines is the same as the structure of each cross-section of the heater  71 A taken along corresponding cutting lines in the heater  71 A of the substrate processing apparatus  1 A. 
     A configuration of the heating mechanism  7 B different from that of the heating mechanism  7 A will be mainly described below. Description of a similar configuration will be omitted appropriately. The components of the heating mechanism  7 B, whose description will be omitted, can be described in the description of the components bearing the same reference sings of the heating mechanism  7 A described above, or can be described in the description of the heating mechanism  7 A by replacing the reference sings of the components of the heating mechanism  7 A and the like with the reference sings of the corresponding components of the heating mechanism  7 B and the like. The corresponding components bear reference signs combining the same numerals and an alphabet “B”. 
     The heater  71 B is arranged in a positional relationship similar to that of the heater  71 A of the substrate processing apparatus  1 A relative to the substrate W and the spin chuck  21 , and is held similarly to the heater  71 A. The heater  71 B is movable upward and downward by a moving mechanism (not shown) between the processing position and the retreat position similarly to the heater  71 A. The heater  71 B is supplied with power while being arranged at the processing position, and then, the heater  71 B generates heat to heat the peripheral portion of the substrate W. 
     The heater  71 B (body portion  72 ) is an annular plate-shaped member extending in the circumferential direction of the substrate W along the peripheral portion of the lower surface of the substrate W. The recess  170  is formed in the outer peripheral surface S 10  of the heater  71 B. The recess  170  is recessed from the outer peripheral surface S 10  of the body portion  72  toward the center of the heater  71 B (toward the rotation axis a 1 ). The recess  170  passes through the heater  71 B vertically from the opposed surface S 7  of the heater  71 B to a surface (lower surface) S 8  opposite to the opposed surface S 7 . 
     The recess  170  has a bottom surface  171  and side surfaces  172  and  173 . The bottom surface  171  and the side surfaces  172  and  173  are vertical planes of approximately elongated shape extending from the opposed surface S 7  of the heater  71 B to the surface S 8  heater  71 B. The normal of the bottom surface  171  is orthogonal to the rotation axis a 1 . The side surface  172  ( 173 ) extends from the end of the bottom surface  171  downstream (upstream) in the direction of rotation of the substrate W to the outer peripheral surface S 10  of the heater  71 B. The side surfaces  172  and  173  are orthogonal to the bottom surface  171  and are parallel to each other. 
     The recess  170  has an opening (“opposed-surface opening)  174  open to the opposed surface S 7 , an opening (“outer-peripheral-surface opening”)  175  open to the outer peripheral surface of the heater  71 B, and an opening  176  open to the surface S 8 . The openings  174  to  176  each have a rectangular shape. The opening  174  is opposed to the portion, which is adjacent to the position PL 2  with which the liquid flow L 2  of the rinse liquid discharged from the nozzle  55  comes into contact, of the peripheral portion of the to-be-protected surface of the substrate W. The upper edges (lower edges) of the bottom surface  171  and the side surfaces  172  and  173  form the periphery of the opening  174  ( 176 ). The intersecting lines of the outer peripheral surface S 10  of the heater  71 B and the side surfaces  172  and  173  form the periphery of the opening  175 . The openings  174 ,  175 , and  176  are sequentially continuous with each other and form one opening from the opposed surface S 7  of the heater  71 B to the surface S 8  via the outer peripheral surface S 10 . The recess  170  accommodates a nozzle head  150  holding nozzles  45  and  55  of the rear surface protection unit  8 , and the respective outlets of the distal end portions of the nozzles  45  and  55  are opposed to the peripheral portion of the lower surface of the substrate W. 
     The heating element  73 B is arranged below the annular portion of the opposed surface S 7  of the heater  71 B except for the outer peripheral portion and the inner peripheral portion of the opposed surface S 7  (more specifically, the annular-belt shaped portion except for the opening  174  of the recess  170 ), over the entire annular (more specifically, annular-belt-shaped) arrangement region defined along the annular portion. The arrangement region for the heating element  73 B is parallel to the lower surface of the substrate W and the opposed surface S 7  of the heater  71 B. Preferably, the substrate W is uniformly heated with ease if the arrangement region for the heating element  73 B is parallel to the lower surface of the substrate W. Inside the heater  71 B, a temperature (not shown) is also arranged. The temperature sensor measures the temperature of the heater  71 B and transmits the measurement result to the control unit  130 B. The control unit  130 B controls power supply to the heating element  73 B based on the measurement result. 
     The heating flow path  74 B is arranged below the heating element  73 B along the heating element  73 B. The respective portions of the heating flow path  74 B can be uniformly heated with ease if the heating flow path  74 B is arranged along the heating element  73 B. Thus, the inert gas flowing through each part of the heating flow path  74 B is uniformly heated with ease. 
     The body portion  72  of the heater  71 B includes, for example, a lower member  72   a , a middle member  72   b , and an upper member  72   c  layered sequentially from below to above. The members  72   a  to  72   c  are annular plate-shaped members extending in the circumferential direction of the substrate W along the peripheral portion of the lower surface of the substrate W. The recess  170  is formed in a part of the body portion  72  at the outer peripheral surface side. In the cross-sectional shapes of the respective members  72   a  to  72   c  taken along the horizontal plane, a rectangular recess is formed that is recessed from the outer peripheries of the respective members  72   a  to  72   c  toward the centers of the respective members  72   a  to  72   c.    
     In the example illustrated in  FIG. 30 , the heating flow path  74 B is repeatedly arranged as follows: it makes approximately one loop around an inner peripheral surface S 9  of the heater  71 B in the circumferential direction, is then doubled back toward the outer peripheral surface S 10  of the heater  71 B in the plane extending along the opposed surface S 7 , and makes approximately one loop around the heater  71 B in the opposite direction. Consequently, the heating flow path  74 B is arranged across the inner peripheral surface S 9  of the heater  71 B and the outer peripheral surface S 10  of the heater  71 B so as to make approximately four loops by being doubled back every time it makes approximately one loop in the circumferential direction around the inner peripheral surface S 9  of the heater  71 B. The heating flow path  74 B is formed except for in the recess  170 . The heating flow path  74 B cuts across four locations of the longitudinal cross-section of the heater  71 B in the circumferential direction of the heater  71 B. The four locations are arranged sequentially at intervals in the radial direction of the heater  71 B. The innermost (innermost peripheral) portion, that is, the portion with the smallest diameter of the heating flow path  74  is, when seen through from above, arranged between the inner periphery of the heater  71 B and the inner periphery of the arrangement region for the heating element  73  along both of the inner peripheries. The outermost (outermost peripheral) portion, that is, the portion with the largest diameter of the heating flow path  74  is, when seen through from above, arranged between the outer periphery of the arrangement region for the heating element  73  and the outer periphery of the heater  71 B along both of the outer peripheries. 
     The control unit  130 B controls how the heater  71 B heats the substrate W and the inert gas (such as the temperature of the substrate W and the temperature of the discharged inert gas) and also controls the position of the heater  71 B. 
     Rear Surface Protection Unit  8   
     The rear surface protection unit  8  includes a rinse liquid discharge mechanism  840  and a gas discharge mechanism  445 . The rinse liquid discharge mechanism  840  discharges a liquid flow L 2  of a rinse liquid such that the liquid flow L 2  comes into contact with the peripheral portion of the lower surface of the substrate W held and being rotated on the spin chuck  21 . The gas discharge mechanism  445  discharges a gas flow G 5  of an inert gas such that the gas flow G 5  comes into contact with the peripheral portion. 
     The rear surface protection unit  8  discharges the liquid flow L 2  of the rinse liquid onto the peripheral portion of the lower surface of the substrate W from the rinse liquid discharge mechanism  840 . By so doing, the rear surface protection unit  8  protects the lower surface of the substrate W from, for example, a processing liquid discharged so as to come into contact with the position PL 1  in the rotation path of the peripheral portion of the upper surface (more specifically, the processing region S 3  of the peripheral portion of the upper surface) of the substrate W. The liquid flow L 2  is discharged so as to come into contact with the position (“second position”) PL 2  defined in the rotation path (“second rotation path”) of the peripheral portion of the lower surface. The position PL 2  is determined to be upstream from the position PL 1  in the direction of rotation of the substrate W. 
     The rear surface protection unit  8  discharges the gas flow G 5  of the inert gas onto the peripheral portion of the lower surface of the substrate W from the gas discharge mechanism  445 . The gas flow G 5  is discharged so as to come into contact with the position (“fourth position”) P 4  in the rotation path of the peripheral portion of the lower surface and flow from the position P 4  toward the periphery of the lower surface of the substrate W. The position P 4  is determined to be upstream from the position PL 2  in the direction of rotation of the substrate W. A part of the liquid flow L 2  of the rinse liquid discharged onto the position PL 2  loops in the circumferential direction of the substrate W while and remaining in the peripheral portion of the lower surface of the substrate W in the form of a liquid film. Most of the residual rinse liquid is blown off by the gas flow G 5  to be drained out of the substrate W from the peripheral portion of the lower surface of the substrate W. This restricts mixing of a rinse liquid newly discharged from the rinse liquid discharge mechanism  840  onto the position PL 2  and the residual rinse liquid to excessively increase the volume of the rinse liquid. 
     The rinse liquid discharge mechanism  840  includes a tubular nozzle (“rinse liquid discharge nozzle”)  55 . The nozzle  55  passes through the nozzle head  150  and is held by the nozzle head  150 . The nozzle head  150  has an approximately rectangular-solid-shaped outer appearance. The nozzle head  150  is accommodated in the recess  170  of the heater  71 B so as to be arranged below the peripheral portion of the lower surface (portions adjacent to the position PL 2  and the position P 4 ) of the substrate W, with its upper surface being horizontal. The heater  71 B is arranged in advance such that the recess  170  is located below the portions adjacent to the position PL 2  and the position P 4 . The nozzle head  150  is held by, for example, a support member (not shown) provided in the casing  24 . The nozzle  55  is connected with a rinse liquid supply unit  84  serving as a pipe system that supplies a rinse liquid to the nozzle  55 . Specifically, the lower end of the nozzle  55  is connected with a first end of a pipe  842  of the rinse liquid supply unit  84 . The outlet of the distal end of the nozzle  55  is opposed to the position PL 2 . The nozzle  55  is supplied with a rinse liquid from the rinse liquid supply unit  84  and discharges the supplied rinse liquid through the outlet of the distal end. The rinse liquid discharge mechanism  840  discharges the liquid flow L 2  of the rinse liquid from the nozzle  55  in accordance with the control of the control unit  130 B. The liquid flow L 2  is discharged so as to come into contact with the position PL 2  defined in the rotation path of the peripheral portion of the lower surface of the substrate W. 
     The rinse liquid supply unit  84  specifically includes a rinse liquid supply source  841 , the pipe  842 , and an on/off valve  843 . The rinse liquid supply source  841  is a supply source that supplies a rinse liquid. The rinse liquid supply source  841  is connected to the nozzle  55  via the pipe  842  in which the on/off valve  843  is interposed. When the on/off valve  843  is opened, thus, the rinse liquid supplied from the rinse liquid supply source  841  is discharged from the nozzle  55  onto the position PL 2  as the liquid flow L 2 . 
     The on/off valve  843  of the rinse liquid supply unit  84  is opened or closed under the control of the control unit  130 B by a valve open/close mechanism (not shown) electrically connected to the control unit  130 B. That is to say, the control unit  130 B controls how the rinse liquid is discharged from the nozzle  55  of the nozzle head  150  (such as a discharge start timing, a discharge end timing, and a discharge flow rate). Specifically, by the control of the control unit  130 B, the rinse liquid discharge mechanism  840  discharges the liquid flow L 2  of the rinse liquid such that the liquid flow L 2  comes into contact with the position PL 2  in the rotation path of the lower peripheral portion of the substrate W being rotated about the rotation axis a 1 . 
     The gas discharge mechanism  441  includes a nozzle (“gas charge nozzle for to-be-protected surface”)  45 . The nozzle  45  passes through the nozzle head  150  and is held by the nozzle head  150  on the side upstream from the nozzle  55  in the direction of rotation of the substrate W. The lower end of the nozzle  45  is connected with a first end of the pipe  475 . A second end of the pipe  475  is connected with the gas supply source  455  that supplies an inert gas. At some midpoint in the pipe  475 , a flow rate control unit  485  and an on/off valve  465  are provided sequentially from the gas supply source  455  side. The outlet of the distal end (upper end) of the nozzle  45  is opposed to the part of the rotation path of the peripheral portion of the lower surface of the substrate W rotated by the rotary holding mechanism  2 , specifically, the position P 4  determined in the rotation path. 
     The nozzle  45  is supplied with an inert gas (in the illustrated example, a nitrogen (N 2 ) gas) from the gas supply source  455 . The nozzle  45  discharges the gas flow G 5  of the supplied inert gas from below such that the gas flow G 5  comes into contact with the position P 4 . The nozzle  45  discharges the gas flow G 5  through the outlet in a predetermined direction such that the discharged gas flow G 5  arrives at the position P 4  and then flows from the position P 4  toward the periphery of the substrate W. 
     The flow rate control unit  485  includes a flowmeter and a variable valve. The flowmeter detects the flow rate of a gas flowing through the pipe  475 . The variable valve can adjust the flow rate of the gas in accordance with an open/close amount of the valve. The control unit  130 B controls an open/close amount of the variable valve of the flow rate control unit  485  via a valve control mechanism (not shown) such that the flow rate detected by the flowmeter of the flow rate control unit  485  is equal to a target flow rate. The control unit  130 B can set a target flow rate within a predetermined range in accordance with the preset setup information to freely control a flow rate of a gas passing through the flow rate control unit  485  within the predetermined range. The control unit  130 B also controls the on/off valve  465  between the open state and the closed state via the valve control mechanism. The control unit  130 B thus controls how the gas flow G 5  is discharged from the nozzle  45  (such as a discharge start timing, a discharge end timing, and a discharge flow rate). 
     How easily the residual rinse liquid is blown off by the gas flow G 5  varies depending on the film quality of the surface of the substrate W. Of the hydrophobic film quality and the hydrophilic film quality, the hydrophobic film quality is less likely to blow off the residual processing liquid, and the hydrophilic film quality is more likely to blow off the residual processing liquid. Therefore, how the gas flow G 5  is discharged is preferably set in accordance with the film quality of the surface of the substrate W. 
     3-2. Actions of Rinse Liquid Discharged onto Lower Surface and Inert Gas Discharged onto Upper and Lower Surfaces 
     As illustrated in  FIGS. 26 and 27 , one (in the illustrated example, the nozzle  51   c ) among the nozzles  51   a  to  51   c  capable of discharging a chemical solution as a processing liquid discharges the liquid flow L 1  of the chemical solution such that the liquid flow L 1  comes into contact with the position PL 1  in the rotation path of the peripheral portion of the upper surface of the substrate W. The nozzle  55  of the rinse liquid discharge mechanism  840  discharges the liquid flow L 2  of the rinse liquid such that the liquid flow L 2  comes into contact with the position PL 2  in the rotation path of the peripheral portion of the lower surface (to-be-protected surface) opposite to the upper surface (to-be-processed surface) of the substrate W. The position PL 2  is a position upstream from the position PL 1  in the direction of rotation of the substrate W. 
     The nozzle  41  of the gas discharge mechanism  441  discharges the gas flow G 1  of the inert gas such that the gas flow G 1  comes into contact with the position (“third position”) P 3  in the rotation path of the peripheral portion of the upper surface of the substrate W. The position P 3  is located between the position PL 1  and the position PL 2  along the periphery (end face S 5 ) of the substrate W. 
     The nozzle  45  of the gas discharge mechanism  445  discharges the gas flow G 5  of the inert gas such that the gas flow G 5  comes into contact with the position P 4  in the rotation path of the peripheral portion of the lower surface of the substrate W. The position P 4  is located adjacent to the position PL 2  upstream from the position PL 2  in the direction of rotation of the substrate W. 
       FIG. 34  is a longitudinal cross-sectional view of the substrate W schematically illustrating how the liquid flow L 2  of the rinse liquid discharged by the substrate processing apparatus  1 B wraps around an end face S 5  of the substrate. The longitudinal cross-sectional view of the substrate W of  FIG. 34  is a cross-sectional view of the substrate W cut on the cutting surface including the rotation axis a 1  and the position PL 1 . The liquid flow L 1  of the chemical solution, the liquid flow L 2  of the rinse liquid, and the gas flow G 1  of the inert gas are projected onto the cutting surface and illustrated schematically. Although the liquid flows L 1  and L 2  and the gas flow G 1  discharged onto the surface of the substrate W flow along the surface of the substrate W, for easy viewing,  FIG. 34  illustrates these flows at intervals from the surface of the substrate W. 
     The flat portion of the upper surface and the flat portion of the lower surface of the substrate W are connected by an annular curved surface S 30  provided along the circumferential direction of the substrate W. If a depth D 11  of the substrate W is, for example, 0.7 mm, a width D 12  of the curved surface S 30  along the radial direction of the substrate W is, for example, 0.3 mm. In the longitudinal cross-section of the substrate W, the curved surface S 30  projects toward the outside of the substrate W along the radial direction of the substrate W and is curved. The annular apex (distal end portion) of the curved surface S 30  is an end face (also referred to as a “periphery” or “edge”) S 5  of the substrate W. A curved surface portion S 3   a  is a portion of the curved surface S 30  on the side close to the upper side (on the side close to the to-be-processed surface) relative to the end face S 5 . The curved surface portion S 3   a  is an annular curved surface connecting a flat portion S 3   b  and the end face S 5 . The processing region S 3  of the peripheral portion of the upper surface of the substrate W on the side closer to the periphery includes the annular flat portion S 3   b  and the annular curved surface portion S 3   a.    
     The liquid flow L 2  of the rinse liquid discharged onto the position PL 2  loops in the circumferential direction of the substrate W along the peripheral portion of the lower surface of the substrate W due to the influence of, for example, the direction in which the liquid flow L 2  is discharged and the rotation of the substrate W, and a part of the rinse liquid wraps around the curved surface S 30  of the substrate W including the end face S 5  from the peripheral portion of the lower surface of the substrate W. Here, although a part of the liquid flow L 2  wraps around the end face S 5  and the curved surface portion S 3   a  of the substrate from the to-be-protected surface of the substrate W when the liquid flow L 2  moves from the position PL 2  in the circumferential direction of the substrate W and then arrives at the position PL 1  or its vicinity (below the position PL 1 ), the position PL 2  (a distance from the position PL 2  to the position PL 1  along the periphery of the substrate W) is set in advance relative to the position PL 1  such that the part of the liquid flow L 2  does not wrap around up to the flat portion S 3   b . Specifically, the position PL 2  is set in advance such that a part of the liquid flow L 2  of the rinse liquid wraps around the end face S 5  of the substrate W from the to-be-protected surface of the substrate W and hardly wraps around the peripheral portion of the to-be-processed surface. The position PL 2  described above varies depending on the conditions for discharging the rinse liquid, such as the rotational speed and the surface film quality of the substrate W, and the viscosity and flow rate of the liquid flow L 2 . The position PL 2  is set in advance through experiments or the like in accordance with the conditions for discharging the rinse liquid. 
     When the liquid flow L 1  of the chemical solution is discharged onto the position PL 1 , the liquid flow L 1  moves in the circumferential direction of the substrate W along with the rotation of the substrate W. Also, a part of the liquid flow L 1  wraps around the curved surface portion S 3   a  from the flat portion S 3   b  of the substrate W. The position PL 2 , however, is set such that the rinse liquid that has been discharged onto the position PL 2  and wrapped around the end face S 5  hardly wraps around the peripheral portion of the upper surface, thus restricting the dilution of the processing liquid discharged onto the position PL 1  with the rinse liquid on the peripheral portion of the upper surface. Also, the gas flow G 1  of the inert gas discharged onto the position P 3  can further restrict the rinse liquid from wrapping around the peripheral portion of the upper surface. 
     A part of the processing liquid discharged onto the position PL 1  turns into the residual processing liquid remaining on the peripheral portion of the upper surface and wraps around up to the position P 3 . At the position P 3 , the gas flow G 1  blows off most of the residual processing liquid to drain the residual processing liquid out of the substrate W. This restricts the generation of splashes due to a collision between the residual processing liquid and a processing liquid newly discharged onto the position PL 1 . 
     Before the rinse liquid discharged onto the position PL 1  arrives at the position PL 1  or its vicinity, a part of the rinse liquid has wrapped around the end face S 5 . This restricts the processing liquid discharged onto the position PL 1  from wrapping around the peripheral portion of the lower surface of the substrate W via the end face S 5 . 
     A part of the rinse liquid discharged onto the position PL 2  turns into the liquid-film-shaped residual rinse liquid adhering to and remaining at the peripheral portion of the lower surface of the substrate W, and then loops by the rotation of the substrate W to arrive at the position P 4  or its vicinity. The gas flow G 5  of the inert gas discharged onto the position P 4  blows off most of the residual rinse liquid to drain the residual rinse liquid out of the substrate W. This restricts a situation in which the residual rinse liquid and a rinse liquid newly discharged onto the position are mixed to excessively increase the volume of the rinse liquid, and accordingly, the rinse liquid wraps around the upper surface of the substrate W. 
     The heater  71 B has the recess  170  formed therein, and the recess  170  has the opening  174  that is opposed to the portions adjacent to the positions PL 2  and P 4  in the rotation path of the peripheral portion of the lower surface of the substrate W and that is open to the opposed surface S 7 . At least the outlets of the nozzles  45  and  55  of the rinse liquid discharge mechanism  840  are accommodated in the recess  170 . The outlet of the distal end portion of the nozzle  55  ( 45 ) is arranged in the opening  174  when the recess  170  is viewed from the opening  174  side. This enables the nozzle  55  and the nozzle  45  having simple configurations to easily perform the following operations simultaneously: heating the peripheral portion of the substrate W by the heater  71 B and discharging the liquid flow L 2  of the rinse liquid and the gas flow G 5  of the inert gas onto the peripheral portion of the lower surface of the substrate W. 
     3-3. Another Example of Heater 
       FIG. 32  ( FIG. 33 ) is a schematic perspective view of a heater  71 X ( 71 Y) that is another example of the heater  71 B, as viewed from diagonally above. The heater  71 X ( 71 Y) is configured similarly to the heater  71 B except for that a recess  170 X ( 170 Y) is formed in place of the recess  170  of the heater  71 B ( 71 Y). 
     Unlike the recess  170  of the heater  71 B, the recess  170 X of the heater  71 X does not pass through the heater  71 X vertically. An opening  175 X of the heater  71 X that is open to the outer peripheral surface S 10  is thus open across the outer peripheral surface S 10  from the upper end of the outer peripheral surface S 10  to the center and its vicinity of the outer peripheral surface S 10 . Like the recess  170 X of the heater  71 X, the recess  170 Y of the heater  71 Y does not pass through the heater  71 Y vertically. The recess  170 X differs from the recess  170 Y in that the recess  170 X has the opening  175 X open to the outer peripheral surface S 10 , whereas the recess  170 Y is not open to the outer peripheral surface S 10 . An opening  174 Y that is open to the opposed surface S 7  of the heater  71 Y is open to the outer-periphery-side portion of the annular opposed surface S 7 . The opening  174 Y, however, does not extend up to the outer periphery of the opposed surface S 7  along the radial direction of the heater  71 Y. 
     If the nozzle head  150  holding the nozzles  45  and  55  are accommodated in the recess  170 X ( 170 Y) such that the outlets of the nozzles  45  and  55  are opposed to the positions P 4  and PL 2 , the following operations can be performed simultaneously: heating the peripheral portion of the substrate W by the heater  71 X ( 71 Y), and discharging the liquid flow L 2  of the rinse liquid and the gas flow G 5  of the inert gas onto the peripheral portion of the lower surface of the substrate W. Thus, the heater  71 X ( 71 Y) may be employed in place of the heater  71 B. Alternatively, the recess  170 Y of the heater  71 Y may pass through the heater  71 Y vertically. 
     3-4. Action of Shielding Gas 
       FIG. 20  illustrates an example of the gas flow G 4  of the inert gas discharged between the heater  71 B and the substrate. The heater  71 B irradiates the lower surface of the substrate W with rays of heat H 1  from the opposed surface S 7  through heat generation of the heating element  73 B, thereby heating the substrate W. The inert gas supplied by the gas discharge mechanism  444  is introduced into the heating flow path  74 B and is preheated by the heating element  73 B while flowing through the heating flow path  74 B. The heated gas passes through the through holes  76  and  77  and is then discharged into the space V 1  through the outlets  78  and  79  as the gas flow G 4  of the inert gas. 
     The gas flow G 4  flows toward the periphery of the substrate W and the center of the substrate W from each of the outlets  78  and  79 . On the side close to the periphery of the substrate W and the side close to the substrate W relative to the heater  71 B, an atmosphere G 9  of temperature lower than that of the heated gas flow G 4  is present. The gas flow G 4  discharged through the outlet  78  and directed toward the periphery of the substrate W restricts the atmosphere G 9 , which is present on the side close to the periphery of the substrate W relative to the heater  71 B, from wrapping around the space V 1 . The gas flow G 4  discharged through the outlet  79  and directed toward the center of the substrate W restricts the atmosphere G 9 , which is present on the side close to the center of the substrate W relative to the heater  71 B, from wrapping around the space V 1 . This restricts a reduction in the heating efficiency of the substrate W by the heater  71 B due to the atmosphere G 9 . Also, the gas flow G 4  is preheated, thus contributing to heating of the substrate W. 
     The inert gas discharged by the gas discharge mechanism  441  serves as a shielding gas that prevents the atmosphere G 9  from entering the space V 1  and also as a heating gas that heats the substrate W. 
     When the liquid flow L 2  of the rinse liquid and the gas flow G 5  of the inert gas that are respectively discharged onto the positions PL 2  and P 4  from the nozzles  55  and  45  enter the space V 1  between the heater  71 B and the lower surface of the substrate W, the heating efficiency of the peripheral portion of the substrate W by the heater  71 B may decrease due to scattering of the rinse liquid onto the opposed surface S 7  of the heater  71 B. Thus, the position PL 2  and the position P 4  are preferably provided on the side closer to the periphery of the substrate W than the outlet  78  through which an inert gas is discharged from the outer peripheral portion of the opposed surface S 7  of the heater  71 B. This enables the use of the inert gas discharged from the gas discharge mechanism  444  as a shielding gas that prevents the rinse liquid or an unheated inert gas from entering the space V 1 . 
     3-5. Operation of Substrate Processing Apparatus 
       FIG. 31  is a flowchart illustrating an example operation in which the substrate processing apparatus  1 B processes a substrate with a processing liquid. The operation of the substrate processing apparatus  1 B will be described below with reference to  FIG. 31 . Before the operation illustrated in  FIG. 31 , the substrate W has been transferred to the substrate processing apparatus  1 B to be held on the spin chuck  21 . The nozzle heads  48 B,  49 , and  50  have been arranged at the processing positions by the nozzle moving mechanism  6 , and the splash guard  31  has been arranged at the upper position by the guard drive mechanism  32 . 
     When the process illustrated in  FIG. 31  is started, the rotating mechanism  231  of the substrate processing apparatus  1 B starts rotating the spin chuck  21  holding the substrate W (step S 310 ). The rotational speed of the substrate W is set to, for example, 1000 rotations per minute. 
     Then, the gas discharge mechanism  441  starts discharging the gas flows G 1  of the inert gas from the nozzle  41  of the nozzle head  48 B, and the gas discharge mechanism  443  starts discharging the gas flow G 3  of the inert gas from the nozzle  43  of the nozzle head  49 , and the gas discharge mechanism  445  starts discharging the gas flow G 5  of the inert gas from the nozzle  45  (step S 320 ). The gas flows G 1  and G 5  are respectively discharged onto the position P 3  on the peripheral portion of the upper surface of the substrate W and the position P 4  on the peripheral portion of the lower surface of the substrate W. Preferably, the gas flows G 1  and G 5  are respectively discharged in predetermined directions so as to come into contact with the positions P 3  and P 4  and then flow toward the periphery of the upper surface and the periphery of the lower surface. The nozzle  43  discharges the inert gas from above onto the central portion of the upper surface of the substrate W to generate the gas flow G 3  spreading from the central portion toward the periphery of the substrate W. The flow rate of the gas flow G 3  when the gas flow G 3  discharged from the nozzle  43  is discharged is higher than the flow rate when the gas flow G 1  is discharged. 
     After the discharge of the gas flows G 1  and G 3  has been started, the heating mechanism  7 B starts heating the peripheral portion of the substrate W by the heater  71 B. The heater  71 B is heated to, for example, approximately 185°. The gas discharge mechanism  444  of the heating mechanism  7 B starts supplying the inert gas from the gas supply source  454  at a flow rate of, for example, 40 L/min to 60 L/min to start discharging the gas flow G 4  through the plurality of outlets  78  and  79  formed in the opposed surface S 7  of the heater  71 B (step S 330 ). The inert gas is heated to be higher than the processing temperature (e.g., 60° C. to 90° C.) of the substrate W. 
     After the temperature of the peripheral portion of the substrate W has risen and become stable after a lapse of time, the rinse liquid discharge mechanism  840  starts discharging the liquid flow L 2  of the rinse liquid such that the liquid flow L 2  comes into contact with the position PL 2  determined in the rotation path of the peripheral portion of the lower surface of the substrate W (step S 340 ). The liquid flow L 2  is preferably discharged in a predetermined direction such that the liquid flow L 2 , which has come into contact with the position PL 2 , flows also from the position PL 2  toward the periphery of the lower surface of the substrate W. 
     The processing liquid discharge mechanism  830  discharges the liquid flow L 1  of the processing liquid (chemical solution) such that the liquid flow L 1  comes into contact with the position PL 1  determined in the rotation path of the peripheral portion of the upper surface of the substrate W (more specifically, the processing region S 3  of the upper surface on the side closer to the end face S 5  of the substrate W) after the rinse liquid discharged first onto the position PL 2  arrives at below the position PL 1 , thereby processing the peripheral portion of the upper surface (step S 350 ). Specifically, the processing liquid discharge mechanism  830  discharges the liquid flow L 1  of the chemical solution from one nozzle (in  FIG. 23 , the nozzle  51   c ) among the nozzles  51   a  to  51   d  in accordance with the control of the control unit  130 B. The cross-sectional size and flow rate of the liquid flow L 1  are set in advance such that the width of the liquid film, which turns from the liquid flow L 1  and adheres to the peripheral portion of the substrate W, fits in the processing region S 3 . The liquid flow L 1  comes into contact with the position PL 1  and then forms a liquid film on the processing region S 3 . The liquid film of the processing liquid moves in the circumferential direction of the substrate W while adhering to the peripheral portion of the substrate W along with the rotation of the substrate W. 
     A part of the processing liquid discharged onto the position PL 1  flows from the peripheral portion of the upper surface of the substrate W through the end face S 5  of the substrate W to begin to wrap around the peripheral portion of the lower surface. A part of the liquid flow L 2  of the rinse liquid, however, wraps around the end face S 5  after being discharged onto the position PL 2 . Thus, the rinse liquid that has wrapped around the end face S 5  restricts the processing liquid from wrapping around the lower surface of the substrate W. 
     From the viewpoint of improving the processing rate of the substrate W, the discharged processing liquid preferably stays at the position of discharge in the processing region S 3  for the longest possible period of time. The central angle, which is formed between the straight line connecting the position PL 1  in the rotation path and the center c 1  of the substrate W and the straight line connecting the portion onto which the liquid flow L 1  has been discharged and the center c 1 , gradually increases along with the rotation of the substrate W. For example, 80% of the processing liquid discharged onto the processing region S 3  is drained out of the substrate W mainly by the centrifugal force associated with the rotation of the substrate W while the substrate W rotates until the central angle reaches 90°. After that, the liquid-film-shaped processing liquid that has not been drained out and has remained in the substrate W also moves along the circumferential direction of the substrate W while being gradually drained out of the substrate W and simultaneously adhering to the processing region S 3 , thus contributing to processing of the substrate W during the process. 
     The gas flow G 1 , whose discharge has been started from the nozzle  41  in step S 310 , comes into contact with the liquid film of the residual processing liquid at the position P 3 . The position P 3  is located upstream from the position PL 1  in the direction of rotation of the substrate W along the circumferential direction of the substrate W in the rotation path of the substrate W, and is also located downstream from the position PL 2  in the direction of rotation. Subsequently, the gas flow G 1  flows from the position P 3  toward the periphery of the substrate W due to the influence of, for example, the direction in which the gas flow G 1  flows and the rotation of the substrate W. In other words, the gas discharge mechanism  441  discharges the gas flow G 1  of the inert gas from above onto the position P 3  in the rotation path of the peripheral portion of the upper surface of the substrate W, thereby directing the gas flow G 1  from the position P 3  toward the periphery of the substrate W. Most of the residual processing liquid is drained out of the substrate W from the peripheral portion of the upper surface of the substrate W by the gas flow G 1 . 
     The gas flow G 3  discharged from the nozzle  43  of the gas discharge mechanism  443  spreads from the central portion of the substrate W toward the periphery of the substrate W due to the influence of, for example, the direction in which the gas flow G 3  is discharged and the rotation of the substrate W. In other words, the gas discharge mechanism  443  discharges the inert gas from above the central portion of the upper surface of the substrate W to generate the gas flow G 3  spreading from the central portion toward the periphery of the substrate W. 
     The rinse liquid discharged onto the position PL 2  flows to below the position PL 1  along the periphery of the substrate W, and while the flowing, a part of the rinse liquid wraps around the end face S 5  of the substrate W from the peripheral portion of the lower surface of the substrate W. The rinse liquid that has wrapped around the end face S 5  is restricted from wrapping around the upper surface of the substrate W by the gas flow G 1  flowing from the position P 3  toward the periphery of the substrate W. Also, although a part of the rinse liquid discharged onto the position PL 2  turns into a residual rinse liquid that adheres to and remains in the peripheral portion of the lower surface of the substrate W and makes loops on the lower surface of the substrate W, most of the residual rinse liquid is blown off by the gas flow G 5  of the inert gas discharged onto the position P 4  to be drained out of the substrate W. This restricts mixing of the residual rinse liquid and a rinse liquid newly discharged onto the position PL 2  to excessively increase the volume of the rinse liquid. 
     As described above, most of the processing liquid discharged at the position PL 1  so as to come into contact with the processing region S 3  of the substrate W is drained out of the substrate W during one rotation of the substrate W. This restricts the splashes generated due to a processing liquid newly discharged onto the position PL 1  from coming into contact with the residual processing liquid. The rinse liquid is also restricted from wrapping around the upper surface of the substrate W, thus restricting the dilution of the processing liquid discharged onto the position PL 2  with the rinse liquid that has wrapped around the upper surface. Also, the rinse liquid that has wrapped around the end face S 5  of the substrate W restricts the processing liquid from wrapping around the lower surface of the substrate W. Also, the residual rinse liquid can be easily drained out of the substrate W by the gas flow G 5  discharged onto the position P 4 . 
     While discharging of the gas flows G 1 , G 3 , and G 5  and discharging of the liquid flow L 1  are performed simultaneously, the rotating mechanism  231  rotates the substrate W repeatedly in accordance with the control of the control unit  130 B. For example, the gas flows G 1 , G 3 , and G 5  are discharged respectively at flow rates of 12 L/min, 30 L/min to 130 L/min, and 10 L/min to 10 to 20 L/min. 
     When the control unit  130 B detects, for example, a lapse of a processing time required for processing the substrate W, the processing liquid discharge mechanism  830  stops discharging the processing liquid. This completes the process of step S 340 . 
     The rinse liquid discharge mechanism  840  stops discharging the liquid flow L 2  of the rinse liquid onto the lower surface (position PL 2 ) of the substrate W (step S 360 ). The heating mechanism  7 B stops power supply to the heater  71 B to stop heating the substrate W by the heater  71 B and also stops discharging the gas flow G 4  by the gas discharge mechanism  444  (step S 370 ). 
     The rotating mechanism  231  stops rotating the spin chuck  21  (step S 380 ), and the heating mechanism  7 B stops heating the peripheral portion of the substrate W by the heater  71 B. The gas discharge mechanisms  441 ,  443 , and  445  respectively stop discharging the gas flows G 1 , G 3 , and G 5  (step S 390 ). As a result, the operation illustrated in  FIG. 31  ends. 
     After that, the nozzle moving mechanism  6  and the guard drive mechanism  32  respectively move the nozzle heads  48 B,  49 , and  50 , and the splash guard  31  to the retreat positions. The substrate W is removed from the spin chuck  21  to be transferred from the substrate processing apparatus  1 B. 
     The substrate processing apparatus  1 B discharges the chemical solution such that the chemical solution comes into contact with the position PL 1  in the rotation path of the peripheral portion of the upper surface (to-be-processed surface) of the substrate W and discharges the rinse liquid such that the rinse liquid comes into contact with the position PL 2  in the rotation path of the peripheral portion of the lower surface (to-be-protected surface) opposite to the upper surface of the substrate W. The position PL 2  is located upstream from the position PL 1  in the direction of rotation of the substrate W. The heater  71 B opposed to the lower surface of the substrate W heats the substrate W from the lower surface of the substrate W. The gas discharge mechanism  444  discharges the gas flow G 4  of the heated inert gas into the space V 1  between the opposed surface S 7  of the heater  71 B and the lower surface of the substrate W. Alternatively, the to-be-processed surface may be the lower surface of the substrate W. In other words, the nozzles of the processing liquid discharge mechanism  830  may discharge the chemical solution such that the chemical solution comes into contact with the first position in the rotation path of the peripheral portion of the lower surface of the substrate W. The nozzle  55  of the rinse liquid discharge mechanism  840  may discharge the rinse liquid such that the rinse liquid comes into contact with the second position in the rotation path of the upper surface of the substrate W. The second position may be located upstream from the first position in the direction of rotation of the substrate W. In this case, the heater  71 B heats the substrate W while being opposed to the upper surface of the substrate W, and the gas discharge mechanism  444  discharges the gas flow G 4  into the space between the upper surface of the substrate W and the lower surface (opposed surface) of the heater  71 B. The rinse liquid discharged onto the position PL 2  of the upper surface wraps around the lower surface that is a to-be-processed surface more easily than in the case in which the to-be-processed surface is the upper surface. The volume of the rinse liquid is thus adjusted in advance. 
     The substrate processing apparatus  1 B may be devoid of at least one gas discharge mechanism of the gas discharge mechanism  441  that discharges the gas flow G 1  of the inert gas onto the position P 3  and the gas discharge mechanism  445  that discharges the gas flow G 5  of the inert gas onto the position P 4 . 
     Although the rinse liquid discharge mechanism  840  includes one nozzle  55 , the rinse liquid discharge mechanism  840  may include a plurality of nozzles  55  distributed sparsely in the circumferential direction of the substrate W and discharge, from the plurality of nozzles  55 , the rinse liquid onto a plurality of positions PL 2  determined in the rotation path of the peripheral portion of the to-be-protected surface of the substrate W. If the rinse liquid discharge mechanism  840  includes a plurality of nozzles  55 , it can protect the to-be-protected surface of the substrate more uniformly. 
     Although the gas discharge mechanism  445  includes one nozzle  45 , the gas discharge mechanism  445  may include a plurality of nozzles  45  and discharge, from the plurality of nozzles  45 , an inert gas onto a plurality of positions P 4  determined in the rotation path of the peripheral portion of the to-be-protected surface of the substrate W. The plurality of positions P 4  are determined on the side upstream from the position PL 2  in the direction of rotation of the substrate W. 
     The gas discharge mechanism  441  discharges, from one nozzle  41 , the gas flow G 1  of the inert gas onto the position P 3  in the rotation path of the peripheral portion of the upper surface of the substrate W, where the position P 3  is determined between the position PL 2  and the position PL 1  along the peripheral portion of the substrate W. Alternatively, the gas discharge mechanism  444  may discharge, from a plurality of nozzles  41 , the gas flow G 1  of the inert gas onto a plurality of positions P 3  in the rotation path of the peripheral portion of the upper surface. The plurality of positions P 3  are determined between the position PL 2  and the position PL 1  along the peripheral portion of the substrate W. 
     The gas discharge mechanism  444  discharges the gas flow G 4  from a plurality of outlets  78  and  79  provided in the heater  71 B, while the substrate W rotates. The gas discharge mechanism  444  may thus discharge the gas flow G 4  from a single outlet  78  and a single outlet  79  provided in the heater  71 B. Even when the gas flow G 4  is discharged through only one outlet of the outlet  78  and the outlet  79 , a temperature drop of the substrate W can be restricted more than in the case in which the gas flow G 4  is not discharged. Alternatively, a flow path for the inert gas may be provided between the opposed surface S 7  of the heater  71 B and the heating element  73 B such that the gas flow G 4  may be discharged through an outlet open to above the heating element  73 B. 
     The gas discharge mechanism  444  may discharge the inert gas preheated by, for example, another heater different from the heater  71 B into the space V 1 . Specifically, the gas discharge mechanism  444  may preheat the inert gas supplied from the gas supply source  454  by the other heater and, through the pipe outside of the heater  71 B, discharge the heated inert gas into the space V 1  from the nozzle outside of the heater  71 B. 
     The heater  71 B may be provided so as to cover the entire surface, which is opposite to the to-be-processed surface, of the substrate W. Such a heater  71 B can be provided between the lower surface of the substrate W and the upper surface of the spin chuck  21  when the spin chuck  21 , which includes a plurality of chuck pins, holds the substrate W such that the substrate W does not contact the upper surface of the spin chuck  21 . In this case, the heater  71 B is supported by a columnar support member passing through the inside of the rotary shaft  22  and the spin chuck  21 . 
     Although the substrate processing apparatus  1 B includes the nozzle  43  that discharges the gas flow G 3  of the inert gas, the substrate processing apparatus  1 B may include no nozzle  43 . In that case, the substrate processing apparatus  1 B may include no arm  62  and no nozzle head  49 . 
     Although the substrate processing apparatus  1 B discharges a nitrogen gas as the gas flows G 1  and G 3  to G 5 , at least one gas flow among the gas flows G 1  and G 3  to G 5  may be an inert gas different from the inert gas of the other gas flows. 
     The substrate processing apparatus according to the third embodiment configured as described above restricts a rinse liquid from wrapping around the to-be-processed surface until the rinse liquid moves from the position PL 2  to the position PL 1  or its vicinity in the circumferential direction of the substrate W, thus restricting the dilution of the chemical solution discharged onto the position PL 1  with the rinse liquid at the peripheral portion of the to-be-processed surface of the substrate W. The rinse liquid has wrapped around the end face from the to-be-protected surface before the rinse liquid arrives at the position PL 1  or its vicinity in the circumferential direction of the substrate W, thus washing away the chemical solution that begins to wrap around the to-be-protected surface from the position PL 1  with the rinse liquid to dilute the chemical solution. Thus, the to-be-protected surface can be processed with a chemical solution that has wrapped around the to-be-protected surface while the peripheral portion is processed efficiently by discharging the chemical solution onto the peripheral portion of the to-be-processed surface of the substrate W. 
     The substrate processing apparatus according to the third embodiment configured as described above discharges an inert gas onto the peripheral portion of the to-be-processed surface of the substrate W at the position P 3  between the positions PL 2  and PL 1 . The inert gas flows downstream in the direction of rotation of the substrate W while flowing toward the periphery of the substrate W along the to-be-processed surface due to the rotation of the substrate W. This restricts the rinse liquid from wrapping around the to-be-processed surface while the rinse liquid that has been discharged onto the to-be-protected surface of the substrate W at the position PL 2  moves to the position PL 1  or its vicinity in the circumferential direction of the substrate W. 
     The substrate processing apparatus according to the third embodiment configured as described above discharges an inert gas onto the peripheral portion of the to-be-protected surface of the substrate W at the position P 4 . The inert gas flows downstream in the direction of rotation of the substrate W while flowing toward the periphery of the substrate W along the to-be-protected surface due to the rotation of the substrate W. The rinse liquid discharged onto the peripheral portion of the to-be-protected surface at the position PL 2  loops, on the substrate W in the circumferential direction of the substrate W, downstream in the direction of rotation of the substrate W while being drained out of the substrate W from the periphery of the to-be-protected surface due to the rotation of the substrate W. Thus, a part of the rinse liquid discharged onto the position PL 2  arrives at the position P 4 . The rinse liquid that has arrived at the position P 4  is thus blown off, by the inert gas discharged onto the position P 4 , from the peripheral portion of the to-be-protected surface of the substrate W toward the outside of the substrate W, thus reducing the volume of the rinse liquid further. This reduces the volume of the rinse liquid that loops around the peripheral portion of the to-be-protected surface in the circumferential direction of the substrate W and again arrives at the position PL 2 . Consequently, a rinse liquid newly discharged onto the position PL 2  is restricted from coming into contact with the rinse liquid that has looped around the peripheral portion to generate splashes. Also, the rinse liquid is restricted from increasing excessively in amount to wrap around the to-be-protected region of the to-be-processed surface of the substrate W. 
     In the substrate processing apparatus according to the third embodiment configured as described above, the recess  170  with the opening  174  open to the opposed surface S 7  of the heater  71 B is formed in the heater  71 B, and the opening  174  is opposed to the portion adjacent to the position PL 2  in the rotation path of the lower surface peripheral portion. Besides, at least the outlet portion of the nozzle  55  is accommodated in the recess  170 . This enables the following operations simultaneously: bringing the heater  71 B closer to the to-be-protected surface of the substrate W to efficiently heat the peripheral portion of the substrate W from the to-be-protected surface side, and discharging the rinse liquid onto the position PL 2 . 
     In the substrate processing apparatus according to the third embodiment configured as described above, the recess  170  of the heater  71 B passes through the heater  71 B vertically, thus facilitating the work of arranging the nozzle  55  that discharges the rinse liquid. 
     In the substrate processing apparatus according to the third embodiment configured as described above, the opening  175 X open to the outer peripheral surface S 10  of the heater  71 B is further formed in the recess  170 X of the heater  71 X, and the opening  174  open to the opposed surface S 7  and the opening  175 X are continuous with each other. This facilitates the work of arranging the nozzle  55  that discharges the rinse liquid. 
     In the substrate processing apparatus according to the third embodiment configured as described above, the opening  175  open to the outer peripheral surface S 10  of the heater  71 B and the opening  176  open to the surface S 8  opposite to the opposed surface S 7  are formed in the recess  170  of the heater  71 B, and the openings  176 ,  175 , and  174  are sequentially continuous with each other. This facilitates the work of arranging the rinse liquid discharge nozzle. 
     In the substrate processing apparatus according to the third embodiment configured as described above, the gas flow G 4  of the preheated inert gas is discharged into the space V 1  between the opposed surface S 7  of the heater  71 B and the surface (to-be-protected surface), which is opposite to the to-be-processed surface, of the substrate W. This restricts the atmosphere G 9  from entering the space V 1  to restrict a drop in the heating efficiency of the substrate W, and also restricts a drop in heating efficiency also by the gas flow G 4  of the inert gas. Thus, the substrate W is processed while being efficiently heated. 
     In the substrate processing apparatus according to the third embodiment configured as described above, the gas discharge mechanism  444  discharges the gas flow G 4  of the inert gas preheated by the heater  71 B. Thus, there is no need to separately provide the heater for heating the inert gas, reducing the cost of the substrate processing apparatus. 
     In the substrate processing apparatus according to the third embodiment configured as described above, the gas discharge mechanism  444  includes the heating flow path  74 B arranged along the heating element  73 B of the heater  71 B and discharges the inert gas heated by the heater  71 B when flowing through the heating flow path  74 . This improves the heating efficiency of the inert gas by the heater  71 B. 
     In the substrate processing apparatus according to the third embodiment configured as described above, the heating flow path  74 B is arranged two-dimensionally along the heating element  73 B, thus further improving the heating efficiency of the inert gas by the heater  71 B. 
     In the substrate processing apparatus according to the third embodiment configured as described above, the heating flow path  74 B is arranged opposite to the substrate W relative to the heating element  73 B, and thus, can efficiently heat both of the substrate W and the inert gas by the heating element  73 B. 
     In the substrate processing apparatus according to the third embodiment configured as described above, the gas discharge mechanism  444  includes the outlets  78  and  79  respectively provided in the outer peripheral portion and the inner peripheral portion of the annular heater  71 B and discharges the inert gas through the outlets  78  and  79 . This effectively restricts the atmosphere G 1  around the heater  71 B from entering the space V 1  between the substrate W and the heater  71 B. This enables the substrate W to be heated efficiently. 
     While the invention has been shown and described in detail, the foregoing description is in all aspects illustrative and not restrictive. It is therefore understood that numerous modifications and variations can be devised without departing from the scope of the invention.