Patent Publication Number: US-2021183669-A1

Title: Heating treatment apparatus and heating treatment method

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a continuation application of U.S. patent application Ser. No. 16/136,793, filed on Sep. 20, 2018, which claims the benefit of Japanese Patent Application No. 2017-182138 filed on Sep. 22, 2017, the entire disclosures of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The various aspects and embodiments described herein pertain generally to a heating treatment apparatus and a heating treatment method. 
     BACKGROUND 
     In the manufacture of a semiconductor device, to dry a coating film such as a resist film formed on a substrate such as a semiconductor wafer (hereinafter, simply referred to as “wafer”), a heating treatment is performed on this semiconductor wafer. 
     Conventionally, such a heating treatment is performed by using a heating treatment apparatus. In performing this heating treatment, it is required to heat the substrate uniformly as it affects uniformity of a film thickness. 
     In consideration of this requirement, a conventional heating treatment apparatus is equipped with a placing table for mounting the substrate thereon; a housing configured to accommodate the placing table and form a processing space therein; a shutter member provided around the placing table to surround the placing table; an elevating device configured to move the shutter member up and down; a cover member configured to cover an upper portion of the processing space within the housing and connected to a gas exhaust line at a central portion thereof; and gas holes arranged along a circumferential direction thereof (Patent Document 1). A ring-shaped air rectifying plate configured to form an annular air flow inlet between the ring-shaped air rectifying plate and a peripheral portion of the cover member when the shutter member is raised is further provided. 
     With this configuration, a downflow in the vicinity of the apparatus can be uniformly introduced into the processing space from a circumferential direction of the processing space. As a result, a local decrease of a temperature of the wafer as a result of a direct contact with the downflow introduced from a wafer entrance can be suppressed, so that a hindrance to achieving thickness uniformity of the resist film can be improved. 
     Patent Document 1: Japanese Patent Laid-open Publication No. H09-326341 
     SUMMARY 
     In the heating treatment apparatus disclosed in the aforementioned Patent Document 1, however, since the downflow of air (typically having a temperature of 23° C.) is introduced into the processing space only from above the processing space within the housing, a center-oriented descending airflow is created in a heat atmosphere within the processing space. As a result, a stagnation of the airflow is generated between the descending airflow and an inner wall of the shutter member, and a sublimated matter may float in this stagnation and leak to the outside from an apparatus gap. To suppress the leakage of the sublimated matter by suppressing the generation of the stagnation, an exhaust rate needs to be increased. In this regard, there is still a room for improvement from the viewpoint of energy saving. 
     In view of the foregoing, exemplary embodiments provide a technique capable of suppressing generation of stagnation of an airflow within a processing space in a heating treatment apparatus for a substrate, thus allowing a sublimated matter to be exhausted at a smaller exhaust rate as compared to conventional cases. 
     In one exemplary embodiment, there is provided a heating treatment apparatus configured to heat a substrate having a coating film formed thereon. The heating treatment apparatus includes a placing table configured to place the substrate thereon; a heating device configured to heat the substrate placed on the placing table; a top surface unit provided above the placing table and configured to cover the placing table; and a side surface unit configured to surround the placing table and located at an outer periphery of the placing table. A heat treatment space is formed by the placing table, the top surface unit and the side surface unit. An exhaust unit configured to exhaust an atmosphere within the heat treatment space is provided at a central portion of the top surface unit. A first gas inlet and a second gas inlet are provided in a circumferential direction of the side surface unit and through which a gas is supplied into the heat treatment space. A height position of the first gas inlet is on a level with a height position of the substrate placed on the placing table, and a height position of the second gas inlet is higher than the height position of the first gas inlet. A flow rate of the gas introduced into the heat treatment space from the first gas inlet is larger than a flow rate of the gas introduced into the heat treatment space from the second gas inlet. 
     According to the exemplary embodiment, the first gas inlet and the second gas inlet through which the gas is supplied into the heat treatment space are provided, and the height position of the first gas inlet is on the level with the substrate placed on the placing table. Accordingly, it is possible to supply a horizontal laminar flow toward a surface of the substrate on the placing table. Further, the height position of the second gas inlet is higher than the height position of the first gas inlet, and the flow rate of the gas supplied into the heat treatment space from the first gas inlet is larger than the flow rate of the gas supplied into the heat treatment space from the second gas inlet. Therefore, generation of a stagnation of an airflow within the heat treatment space is suppressed due to the gas supplied from the second gas inlet. As a result, when exhausting the atmosphere within the heat treatment space, the atmosphere can be exhausted at a smaller exhaust rate than in conventional cases while suppressing leakage of the sublimated matter. 
     A ratio between the flow rate of the gas introduced into the heat treatment space from the first gas inlet and the flow rate of the gas introduced into the heat treatment space from the second gas inlet is in a range from 9:1 to 6:4. More desirably, the flow rate ratio may be in a range from 5:1 to 7:3. Still more desirably, the flow rate ratio may be 4:1. 
     Further, according to the investigation of the present inventors, it is deemed that the higher the height position of the second gas inlet is, the better it may be. Further, it is deemed that an effect of suppressing the generation of the stagnation can be achieved by providing the second gas inlet at a height position higher than a half of a height of the heat treatment space, and, further, that the generation of the stagnation can be suppressed more effectively as the second gas inlet is located as close to the top surface unit of the heat treatment space as possible. As will be described in the following exemplary embodiment, it is most desirable that the second gas inlet is located at the top surface unit of the heat treatment space (the topmost portion of the heat treatment space). 
     In another exemplary embodiment, there is provided a heating treatment apparatus configured to heat a substrate having a coating film formed thereon. The heating treatment apparatus includes a placing table configured to place the substrate thereon; a heating device configured to heat the substrate placed on the placing table; a top surface unit provided above the placing table and configured to cover the placing table; and a side surface unit configured to surround the placing table and located at an outer periphery of the placing table. A heat treatment space is formed by the placing table, the top surface unit and the side surface unit. An exhaust unit configured to exhaust an atmosphere within the heat treatment space is provided at a central portion of the top surface unit. A first gas inlet and a second gas inlet are provided in a circumferential direction of the side surface unit and through which a gas is supplied into the heat treatment space. A height position of the first gas inlet is on a level with a height position of the substrate placed on the placing table, and a height position of the second gas inlet is higher than the height position of the first gas inlet. The first gas inlet is larger than the second gas inlet. 
     According to the present exemplary embodiment, since the first gas inlet is larger than the second gas inlet, a pressure loss of the second gas inlet is large when a downflow in a region where the heating treatment apparatus is provided is introduced into the heat treatment space. Therefore, a flow rate of the gas supplied from the first gas inlet can be set to be larger than a flow rate of the gas supplied from the second gas inlet. Accordingly, the gas supplied from the second gas inlet can be used to suppress the generation of the stagnation within the heat treatment space, so that the generation of the stagnation within the heat treatment space can be suppressed. Therefore, when exhausting the atmosphere within the heat treatment space, it is possible to exhaust the sublimated matter at a smaller exhaust rate as compared to the conventional cases. 
     A ratio between a size of the first gas inlet, that is, a cross sectional area of an opening of the first gas inlet and a size of the second gas inlet, that is, a cross sectional area of an opening of the second gas inlet may be in a range from 9:1 to 6:4. More desirably, the ratio may be in a range from 5:1 to 7:3. Still more desirably, the ratio may be 4:1. 
     The side surface unit may be implemented by a shutter member allowed to be moved up and down. 
     When the substrate is heated, the shutter member may be moved up, and the second gas inlet may be formed by a gap between an upper end portion of the shutter member and the top surface unit. 
     The shutter member may include an outer shutter and an inner shutter configured as one body. The first gas inlet may communicate with a path formed between the outer shutter and the inner shutter. 
     The outer shutter may have a hollow structure. 
     In still another exemplary embodiment, there is provided a heating treatment method of heating a substrate, which has a coating film formed thereon, on a placing table within a heat treatment space. The heating treatment method includes supplying, when heating the substrate, a gas horizontally toward the heat treatment space at a height position on a level with the substrate on the placing table from an outside of the heat treatment space, and supplying the gas toward the heat treatment space at a height position higher than the substrate on the placing table from the outside of the heat treatment space, while exhausting an atmosphere within the heat treatment space from above a center of the heat treatment space. A flow rate of the gas supplied from the height position on the level with the substrate is set to be larger than a flow rate of the gas supplied from the height position higher than the substrate. 
     A ratio between the flow rate of the gas supplied from the height position on the level with the substrate and the flow rate of the gas supplied from the height position higher than the substrate is in a range from 9:1 to 6:4. More desirably, the flow rate ratio may be in a range from 5:1 to 7:3. Still more desirably, the flow rate ratio may be 4:1. 
     According to the exemplary embodiments, it is possible to suppress the generation of the stagnation of the airflow in the heat treatment space, and when exhausting the atmosphere within the heat treatment space, it is possible to exhaust the sublimated matter within the heat treatment space at a smaller exhaust rate as compared to the conventional cases. 
     The foregoing summary is illustrative only and is not intended to be any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the detailed description that follows, embodiments are described as illustrations only since various changes and modifications will become apparent to those skilled in the art from the following detailed description. The use of the same reference numbers in different figures indicates similar or identical items. 
         FIG. 1  is a plan view schematically illustrating a substrate processing system equipped with a heating treatment apparatus according to an exemplary embodiment; 
         FIG. 2  is a front view of the substrate processing system of  FIG. 1 ; 
         FIG. 3  is a rear view of the substrate processing system of  FIG. 1 ; 
         FIG. 4  is a schematic side sectional view illustrating a schematic configuration of the heating treatment apparatus according to the exemplary embodiment; 
         FIG. 5  is a perspective view of a shutter member in the heating treatment apparatus of  FIG. 4 ; 
         FIG. 6  is an enlarged view of explaining the shutter member in the heating treatment apparatus of  FIG. 4 ; 
         FIG. 7  is a diagram illustrating a state in which a wafer is carried into/out of the heating treatment apparatus of  FIG. 4 ; and 
         FIG. 8  is a schematic side sectional view illustrating a schematic configuration of a heating treatment apparatus in which an outer shutter of a shutter member has a hollow structure. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed e, reference is made to the accompanying drawings, which form a part of the description. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. Furthermore, unless otherwise noted, the description of each successive drawing may reference features from one or more of the previous drawings to provide clearer context and a more substantive explanation of the current exemplary embodiment. Still, the exemplary embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein. It will be readily understood that the aspects of the present disclosure, as generally described herein and illustrated in the drawings, may be arranged, substituted, combined, separated, and designed in a wide variety of different configurations, all of which are explicitly contemplated herein. 
     Hereinafter, various exemplary embodiments will be described in detail with reference to the accompanying drawings. In the specification and the drawings, parts having substantially same configuration and function will be assigned same reference numerals, and redundant description will be omitted. 
     &lt;Substrate Processing System&gt; 
     First, a configuration of a substrate processing system equipped with a heating treatment apparatus according to an exemplary embodiment will be explained.  FIG. 1  is a plan view schematically illustrating a configuration of a substrate processing system  1 .  FIG. 2  and  FIG. 3  are a front view and a rear view schematically illustrating an internal configuration of the substrate processing system  1 . In the substrate processing system  1 , a preset processing is performed on a wafer W as a processing target substrate. 
     The substrate processing system  1  is equipped with, as depicted in  FIG. 1 , a cassette station  10  into/from which a cassette C accommodating therein a multiple number of wafers W is carried; a processing station  11  equipped with a plurality of processing apparatuses respectively configured to perform the preset processings on the wafer W; and an interface station  13  configured to transfer the wafer W between the processing station  11  and an exposure apparatus  12  disposed adjacent to the processing station  11 . 
     A cassette placing table  20  is provided in the cassette station  10 . The cassette placing table  20  is provided with a plurality of cassette placing plates  21  configured to place thereon cassettes C when the cassettes C are carried to/from the outside of the substrate processing system. 
     The cassette station  10  is equipped with a wafer transfer device  23  configured to be movable on a transfer path  22  which is extended in the X direction as shown in  FIG. 1 . The wafer transfer device  23  is also configured to be movable up and down and rotatable around a vertical axis ( 0  direction) and is capable of transferring the wafers W between the cassette C on each cassette placing plate  21  and a transit device of a third block G 3  of the processing station  11  to be described later. 
     The processing station  11  is provided with a plurality of, for example, four blocks, that is, a first block G 1  to a fourth block G 4  each of which is equipped with various kinds of apparatuses. By way of example, a second block G 2  is provided at a rear side (the positive X-axis side of  FIG. 1 , upper side of the drawing) of the processing station  11 . Further, the aforementioned third block G 3  is provided at a side of the cassette station  10  (the negative Y-axis side of  FIG. 1 ) of the processing station  11 , and the fourth block G 4  is disposed at a side of the interface station  13  (the positive Y-axis side of  FIG. 1 ) of the processing station  11 . 
     By way of example, the first block G 1  accommodates therein a plurality of liquid processing apparatuses, as shown in  FIG. 2 . By way of example, developing apparatuses  30  configured to perform a developing processing on the wafer W, lower antireflection film forming apparatuses  31  configured to form an antireflection film (hereinafter, referred to as “lower antireflection film”) under a processing target film of the wafer W, resist coating apparatuses  32  as processing liquid coating apparatuses configured to form the processing target film by coating a resist on the wafer W, and upper antireflection film forming apparatuses  33  configured to form an antireflection film (hereinafter, referred to as “upper antireflection film”) on the processing target film of the wafer W are arranged in this sequence from the bottom. 
     For example, a number of the developing apparatuses  30  is three, and these three developing apparatuses  30  are horizontally arranged. Likewise, a number of the lower antireflection film forming apparatuses  31  is three, and these three lower antireflection film forming apparatuses  31  are arranged horizontally. Further, a number of the resist coating apparatuses  32  is three, and these three resist coating apparatuses  32  are arranged horizontally. Also, a number of the upper antireflection film forming apparatuses  33  is three, and these three upper antireflection film forming apparatuses  33  are arranged horizontally. Here, the numbers of the developing apparatuses  30 , the lower antireflection film forming apparatuses  31 , the resist film forming apparatuses  32  and the upper antireflection film forming apparatuses  33  and the arrangements thereof may be modified as required. 
     In each of these developing apparatuses  30 , lower antireflection film forming apparatuses  31 , resist coating apparatuses  32  and upper antireflection film forming apparatuses  33 , spin coating of coating a preset processing liquid on the wafer W is performed, for example. In the spin coating, the processing liquid is discharged onto the wafer W from, for example, a coating nozzle, and the processing liquid is diffused on a surface of the wafer W by rotating the wafer W. 
     By way of example, within the second block G 2 , as shown in  FIG. 3 , heating treatment apparatuses  40  configured to perform a heating treatment of the wafer W, hydrophobizing apparatuses  41  configured to perform a hydrophobizing processing to improve adhesivity between the resist liquid and the wafer W, and periphery exposure apparatuses  42  configured to perform exposure to a peripheral portion of the wafer W are arranged in the vertical direction and in the horizontal direction. The numbers and the arrangements of the heat treatment apparatuses  40 , the hydrophobizing apparatuses  41  and the periphery exposure apparatuses  42  may be modified as required. 
     By way of example, within the third block G 3 , a multiple number of transit devices  50 ,  51 ,  52 ,  53 ,  54 ,  55  and  56  are arranged in sequence from the bottom. Further, within the fourth block G 4 , a plurality of transit devices  60 ,  61  and  62  are arranged in sequence from the bottom. 
     As depicted in  FIG. 1 , a wafer transfer region D is formed in an area surrounded by the first block G 1  to the fourth block G 4 . Multiple wafer transfer devices  70  each of which has a transfer arm  70   a  configured to be movable in the Y, X,  0  and up-and-down directions are disposed within the wafer transfer region D. The wafer transfer devices  70  are moved within the wafer transfer region D and capable of moving the wafers W to preset apparatuses within the first to fourth blocks G 1  to G 4 . 
     Further, also provided in the wafer transfer region D is a shuttle transfer device  80  which is configured to transfer the wafer W between the third block G 3  and the fourth block G 4  linearly as illustrated in  FIG. 3 . 
     By way of example, the shuttle transfer device  80  is configured to be movable linearly in the Y direction of  FIG. 3 . The shuttle transfer device  80  is capable of transferring the wafer W between the transit device  52  of the third block G 3  and the transit device  62  of the fourth block G 4  by being moved in the Y direction while holding the wafer W. 
     As depicted in  FIG. 1 , a wafer transfer device  81  is provided at the positive X-axis side of the third block G 3 . The wafer transfer device  81  is equipped with a transfer arm  81   a  configured to be movable in the X,  0  and up-and-down directions. The wafer transfer device  81  is capable of transferring the wafer W into the transit devices within the third block G 3  by being moved up and down while holding the wafer W with the transfer arm  81   a.    
     The interface station  13  accommodates therein a wafer transfer device  90  and transit devices  91  and  92 . For example, the wafer transfer device  90  is equipped with a transfer arm  90   a  configured to be movable in the Y,  0  and up-and-down directions. The wafer transfer device  90  is capable of transferring the wafer W between each transit device within the fourth block G 4 , the transit devices  91  and  92  and the exposure apparatus  12  while holding the wafer W with the transfer arm  90   a , for example. 
     The above-described substrate processing system  1  includes a control unit  110 , as illustrated in  FIG. 1 . The control unit  110  is implemented by, for example, a computer and equipped with a program storage unit (not shown). The program storage unit stores therein a program for controlling a processing on the wafer W within the substrate processing system  1 . Further, the program may be recorded in a computer-readable recording medium such as a hard disk (HD), a flexible disk (FD), a compact disk (CD), a magnet optical disk (MO) or a memory card and may be installed to the control unit  110  from this recording medium. 
     &lt;Configuration of Heating Treatment Apparatus&gt; 
     Now, a configuration of the heating treatment apparatus  40  according to the exemplary embodiment will be explained with reference to  FIG. 4 . 
       FIG. 4  illustrates a schematic configuration of the heating treatment apparatus  40 . In the heating treatment apparatus  40 , a heat treatment space S is formed by a ceiling plate  200  forming a top surface unit, a placing table  210  disposed to face the ceiling plate  200  and a shutter member  250  forming a side surface unit. 
     An exhaust port  201  configured as an exhaust unit is provided at a center of the ceiling plate  200 . This exhaust port  201  communicates with an exhaust device  202  provided at an outside of the heating treatment apparatus  40 , for example. A heat protection body  203  is provided on a top surface of the ceiling plate  200 . 
     The placing table  210  is equipped with a heat plate  211  configured as a placing unit on which the wafer W is placed; and a heat plate supporting member  212  configured to support the heat plate  211 . The heat plate supporting member  212  is supported at a base  214  forming a bottom portion of the heating treatment apparatus  40  with a multiple number of supporting columns  213  therebetween. The heat plate  211  has a heater  215  embedded therein. 
     The base  214  is provided with a supporting pin elevating mechanism  216 , and supporting pins  217  provided at the supporting pin elevating mechanism  216  are moved up and down by the supporting pin elevating mechanism  216 . Accordingly, the supporting pins  217  can be protruded upwards from the heat plate  211 , and the wafer W can be delivered between the supporting pins  217  and the transfer arm  70   a  of the aforementioned wafer transfer device  70 . 
     In the present exemplary embodiment, the side surface unit of the heating treatment apparatus  40  is formed by the shutter member  250  having a ring shape. The shutter member  250  includes an outer shutter  260  provided at an outer side; and an inner shutter  270  provided at an inner side with a gap with respect to the outer shutter  260 . As depicted in  FIG. 5 , the outer shutter  260  and the inner shutter  270  are connected as one body by a fixing member  261 , for example. Fixed at a bottom portion  262  of the outer shutter  260  is an elevating member  219  configured to be moved up and down by an elevating mechanism  218  which is provided at the base  214 . Accordingly, if the elevating member  219  is moved up and down, the shutter member  250  is also moved up and down. That is, the outer shutter  260  and the inner shutter  270  are moved up and down as one body. 
     As shown in  FIG. 6 , the outer shutter  260  is provided with the bottom portion  262  and a sidewall portion  263  configured as an outer peripheral surface. Further, an engagement portion  262   a  formed as a step-shaped portion is provided at an inner end portion of the bottom portion  262 , and this engagement portion  262   a  is engaged with an outer end portion  212   a  of the heat plate supporting member  212 . Accordingly, the outer end portion  212   a  of the heat plate supporting member  212  serves as a stopper, and the shutter member  250  is suppressed from being raised over a predetermined range. Further, the state shown in  FIG. 6 , that is, the state in which the shutter member  250  is completely raised is a state when a heating treatment is performed on the wafer W. 
     The inner shutter  270  is provided with a horizontal portion  271  having a circular ring shape; and a suspended portion  272  provided at an inner end portion of the horizontal portion  271 . The inner shutter  270  and the outer shutter  260  are configured as one body with preset gaps therebetween, as will be described below. 
     That is, a gap d 1  formed between a lower end surface of the suspended portion  272  of the inner shutter  270  and a top surface of the bottom portion  262  of the outer shutter  260  along the entire circumference thereof is set to be, for example, 2 mm. A gap D 1  formed between an outer surface of the suspended portion  272  of the inner shutter  270  and an inner surface of the sidewall portion  263  of the outer shutter  260  is set to be, for example, 2 mm. A gap D 2  between a bottom surface of the horizontal portion  271  of the inner shutter  270  and an upper end surface of the sidewall portion  263  of the outer shutter  260  is set to be, for example, 2 mm. In the present exemplary embodiment, a condition of gaps D 1 , D 2 ≥gap d 1  needs to be satisfied. 
     In the state shown in  FIG. 6 , that is, in the state that the shutter member  250  is completely raised, a gap d 2  is formed between a bottom surface of the ceiling plate  200  and a top surface of the horizontal portion  271  of the inner shutter  270  along the entire circumference thereof. In this example, the gap d 2  is set to be, for example, 0.5 mm. 
     The aforementioned gap d 1  serves as a first gas inlet having a slit shape, and the gap d 2  serves as a second gas inlet having a slit shape. Accordingly, in the present exemplary embodiment, the first gas inlet and the second gas inlet has a size ratio of 4:1. Further, a height position of the gap d 1  serving as the first gas inlet is on a level with a height position of the wafer W placed on the heat plate  211  of the placing table  210 . That is, in the state where the shutter member  250  is completely raised, a position of a top surface of the wafer W is within a vertical range of the gap d 1  which serves as the first gas inlet. 
     &lt;Operation of Heating Treatment Apparatus&gt; 
     The heating treatment apparatus  40  according to the exemplary embodiment has the above-described configuration. Now, an operation of the heating treatment apparatus  40  and so forth will be explained. 
     First, as depicted in  FIG. 7 , in a state where the shutter member  250  is lowered and the supporting pins  217  are raised, the wafer W as a heating target is transferred to above the heat plate  211  of the placing table  210  and placed on the supporting pins  217  by the transfer arm  70   a  of the wafer transfer device  70  of the substrate processing system  1 . Then, the transfer arm  70   a  is retreated, and the supporting pins  217  are lowered, so that the wafer W is placed on the heat plate  211 . Thereafter, the shutter member  250  is raised, so that a heating treatment state shown  FIG. 4  is created. That is, the heat treatment space S is formed by the ceiling plate  200 , the placing table  210  and the shutter member  250 . Further, the exhaust device  202  is driven constantly. 
     In this state, the wafer W placed on the heat plate  211  of the placing table  210  is subjected to a heating treatment by being heated with the heater  215 . At this time, from a lower end side of the shutter member  250  configured as the side surface unit of the heating treatment apparatus, a downflow of air is supplied from the gap d 1  serving as the first gas inlet. 
     That is, as the exhaust device  202  is driven, the inside of the heat treatment space S is set to be of a negative pressure by being evacuated through the exhaust port  201  provided at the center of the ceiling plate  200 . Meanwhile, within the substrate processing system  1  in which the heating treatment apparatus  40  is provided, clean air having a room temperature of, e.g., 23° C. always flows downwards from above, so that a downflow of the air is formed therein. Accordingly, as depicted in  FIG. 4 , the downflow of the air is introduced from the gaps D 2  and D 1  at the lower side of the shutter member  250  to be supplied into the heat treatment space S from the gap d 1  as supply air A. Further, the downflow of the air is also introduced from the gap d 2  at an upper end side of the shutter member  250  to be supplied into the heat treatment space S as supply air B. 
     Here, as stated above, as the size ratio of the gap d 1  and the gap d 2  is 4:1, a flow rate ratio of the supply air A and the supply air B is also 4:1. As shown in  FIG. 4 , the supply air A is flown horizontally as a laminar flow toward the wafer W along the entire circumference thereof from the lower end side of the shutter member  250  forming the side surface unit, that is, from the gap d 1  located on the level with the wafer W placed on the heat plate  211  of the mounting table  210 . Meanwhile, the supply air B from an upper end side of the shutter member  250  forming the side surface unit, that is, from the gap d 2  is supplied to above the heat treatment space S at a flow rate equivalent to ¼ of a flow rate of the supply air A. Accordingly, the stagnation of the airflow, which has been conventionally generated in the space above the side portion of the heat treatment space S, is suppressed from being generated. 
     Therefore, the sublimated matter generated in the heat treatment space S when the heating treatment is performed does not stay or float in the heat treatment space S but is exhausted from the exhaust port  201  smoothly, so that the leakage of the sublimated matter is suppressed. 
     Since the stagnation does not occur in the heat treatment space S and the exhaust of the sublimated matter is performed more smoothly as compared to conventional cases as stated above, an exhaust amount by the exhaust device  202  is reduced as compared to the conventional cases. Therefore, an energy saving effect can be improved. According to the investigation of the present inventors, an exhaust rate of 70 L/min is required to suppress the leakage of the sublimated matter in the conventional heating treatment apparatus of the same kind and the same size. According to the present exemplary embodiment, however, the leakage of the sublimated matter is not observed even with the exhaust rate of 30 L/min. 
     Here, “the suppressing of the generation of the stagnation” also implies suppressing generation of a turbulence. Accordingly, it is possible to suppress degradation of uniformity in a film thickness of a coating film on a surface of the wafer W, which might be caused as the way whereby the coating film is dried is locally changed due to the turbulence. 
     Further, if the exhaust rate from the center of the ceiling portion is increased to suppress the leakage of the sublimated matter as in the conventional cases, the film thickness at the central portion of the wafer W tends to be increased. According to the present exemplary embodiment, however, since the exhaust rate is reduced as compared to the conventional cases, such a tendency can be reduced, which contributes to improvement of uniformity in the film thickness. 
     The supply air A is introduced from the gap D 2  to be supplied from the gap d 1  via the gap D 1 . Here, however, as a temperature of the suspended portion  272  of the inner shutter  270  of the shutter member  250  is raised due to the heat atmosphere within the heat treatment space S or the like, the downflow of the air is heated when it flows in a path formed by the gaps D 2  and D 1 . Accordingly, when the supply air A reaches the heat treatment space S from the gap d 1 , the temperature of the supply air A is higher than the temperature (e.g., 23° C.) of the downflow of the air. Therefore, when the supply air A reaches the wafer W, as compared to the conventional case where the supply air comes into contact with the wafer W while being maintained at the substantially room temperature, an amount of heat deprived from the wafer W is reduced. Further, since the supply air A does not flow toward the wafer W from above the wafer W, unlike in the conventional cases, no physical impact is inflicted on the coating film on the surface of the wafer W when the airflows comes into contact with the wafer W. 
     Further, since not only a thermal influence upon the wafer W is small but a thermal influence upon surfaces of the members forming the heat treatment space S from the downflow of the air is also small, a risk that the sublimated matter adheres to the surfaces of the members forming the heat treatment space S including the suspended portion  272  of the inner shutter  270  is also lowered. 
     As a result of investigating constant temperature accuracy on the surface of the wafer W when the heating treatment is actually performed, an average discrepancy of 0.50% is observed in the conventional heating treatment apparatus when the heating treatment is performed at a temperature of 240° C. In the heating treatment apparatus  40  according to the exemplary embodiment, however, the average discrepancy is found to be suppressed to 0.30%. 
     That is, the thermal influence from the gas introduced from the outside of the heat treatment space S upon the wafer W is reduced as compared to the conventional cases. In this point of view, the heating of the wafer W can be performed more uniformly than in the conventional cases, so that the uniformity of the film thickness can be improved. 
     Furthermore, since the path formed by the gaps D 2  and D 1  in the shutter member  250  also serves as a heat insulation space, heat dissipation from the outer shutter  260  is suppressed, and the thermal influence upon various kinds of devices and apparatuses around the heating treatment apparatus  40  is reduced. 
     &lt;Another Configuration Example of Heating Treatment Apparatus&gt; 
     In the above-described exemplary embodiment, though the size ratio between the gap d 1  as the first gas inlet and the gap d 2  as the second gas inlet is set to be 4:1, the size ratio is not limited thereto but may be set to be in a range from 9:1 to 6:4 or 5:1 to 7:3. 
     Further, in the above-described exemplary embodiment, the flow rate of the gas from the first gas inlet is set to be larger than the flow rate of the gas from the second gas inlet by adjusting the size ratio of the gap d1 as the first gas inlet and the gap d2 as the second gas inlet. However, the preset flow rate ratio may be obtained by setting the flow rate from the first gas inlet to be larger than the flow rate of the gas from the second gas inlet not while setting the sizes of those inlets to be of the mentioned ratio but while adjusting a pressure loss by allowing path communicating with the gaps d 1  and d 2  to have a labyrinth structure or changing a size of the inlet of the downflow. 
     Furthermore, in the above-stated exemplary embodiment, each of the first gas inlet and the second gas inlet is implemented by the gap having the slit shape (the gap d 1  and the gap d 2 , respectively). Without being limited thereto, however, each of the first gas inlet and the second gas inlet may be implemented by a plurality of fine holes. 
     Moreover, in the above-described exemplary embodiment, the shutter  250  has a so-called dual-ring shutter structure in which the outer shutter  260  and the inner shutter  270  are provided. As depicted in  FIG. 8 , however, the shutter  250  may have a triple-ring shutter structure in which the outer shutter  280  has a hollow structure. 
     That is, in an outer shutter  280  in the shutter member  250  of the heating treatment apparatus  40  shown in  FIG. 8 , a space  283  is provided between an outer sidewall portion  281  and an inner sidewall portion  282 . Accordingly, since the space  283  serves as the heat insulation space, the heat dissipation from the outer shutter  280  and the thermal influence upon the various devices and apparatuses around the heating treatment apparatus  40  are further suppressed, as compared to the dual-ring shutter structure. Further, since the temperature to which the introduced downflow reaches before it is supplied from the gap d 1  as the first gas inlet is further increased, a difference between the temperature of the supply air A supplied into the heat treatment space S from the gap d 1  and the temperature of the wafer W is further reduced, so that the thermal influence upon the wafer W is further suppressed, and more uniform heating can be achieved. 
     In the above-described exemplary embodiment, the side surface unit of the heating treatment apparatus is formed by the shutter member  250  configured to be moved up and down. However, the exemplary embodiment is not limited thereto, and, by way of non-limiting example, the heating treatment apparatus may have a typical sidewall structure which is not moved up and down. In such a case, a carry-in/out of the wafer W into/from the heat treatment space S may be performed by using a shutter provided at a part of the sidewall. Furthermore, the exemplary embodiment may also be applicable to a heating treatment apparatus having a configuration in which a ceiling plate itself is configured to be opened, and the wafer W is carried into or out of the heat treatment space from above the heat treatment space. 
     From the foregoing, it will be appreciated that various embodiments of the present disclosure have been described herein for purposes of illustration, and that various modifications may be made without departing from the scope and spirit of the present disclosure. Accordingly, the various embodiments disclosed herein are not intended to be limiting. The scope of the inventive concept is defined by the following claims and their equivalents rather than by the detailed description of the exemplary embodiments. It shall be understood that all modifications and embodiments conceived from the meaning and scope of the claims and their equivalents are included in the scope of the inventive concept. 
     The claims of the present application are different and possibly, at least in some aspects, broader in scope than the claims pursued in the parent application. To the extent any prior amendments or characterizations of the scope of any claim or cited document made during prosecution of the parent could be construed as a disclaimer of any subject matter supported by the present disclosure, Applicants hereby rescind and retract such disclaimer. Accordingly, the references previously presented in the parent applications may need to be revisited. 
     INDUSTRIAL APPLICABILITY 
     The exemplary embodiment has advantages when it is applied to heat a substrate.