Abstract:
A technology, when forming a film by supplying TiCl 4  gas and NH 3  gas a plurality of times in alternation to a substrate, can increase the amount of gas flow while suppressing cooling of a valve device, and contribute to an increase in throughput. In the formation of the film, the gas for atmosphere replacement supplied into a processing vessel between supplying one processing gas and supplying the other processing gas is heated ahead of time. Thus, the flow rate of gas can be increased while suppressing cooling of the gas-contacting sites such as a wafer and the inner wall of the processing vessel, and so it is possible to reduce the time necessary to replace the atmosphere, resulting in being able to contribute to increased throughput, and problems such as adhesion of reaction products due to cooling at the valve device are suppressed.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates to a gas supply device used to perform a film forming process on a substrate within a process vessel under a vacuum atmosphere, and a valve device used in the gas supply device. 
       BACKGROUND 
       [0002]    As a method of forming a film on a semiconductor wafer (hereinafter, referred to as a “wafer”) as a substrate, an atomic layer deposition (ALD) method of alternately supplying a raw material gas and a reaction gas reacting with the raw material gas to a wafer a plurality of times to deposit a molecular layer of a reaction product on a surface of the wafer so as to obtain a thin film is known. 
         [0003]    In the ALD method, it is required to supply a substitution gas for substituting a process atmosphere between the supply of the raw material gas and the supply of the reaction gas. Thus, it is important to rapidly substitute an atmosphere to obtain high throughput. For example, Patent Document 1 discloses a method in which, in order to prevent entry of another process gas to a flow passage of a process gas, an inert gas is constantly supplied, and when the supply of the process gas is stopped, the process gas of a process vessel is substituted with the inert gas as a substitution gas. In this case, in order to increase substitution efficiency of the process gas, a flow rate of the inert gas may be increased. However, when the flow rate of the inert gas is increased, a deposition rate may be lowered as a partial pressure of the process gas is lowered. 
         [0004]    Further, the interior of the process vessel is heated by a heating mechanism in order to suppress generation of particles based on adsorption or re-liquefaction of the process gas. However, when a flow rate of the substitution gas is increased, the interior of the process vessel is likely to be cooled by the substitution gas, leading to a state where the process gas is adsorbed to remain on a gas contact portion or re-liquefied or re-solidified. 
       PRIOR ART DOCUMENTS 
     Patent Document 
       [0005]    Japanese laid-open publication No. 2009-038408 (the paragraph 0038) 
       SUMMARY 
       [0006]    The present disclosure provides some embodiments of a technique capable of increasing a flow rate of a substitution gas, while suppressing cooling of a gas contact portion, in forming a film by alternately supplying different process gases to a substrate a plurality of times, thus contributing to enhancement of throughput. 
         [0007]    Further, the present disclosure provides some embodiments of a valve device suitable for performing the aforementioned technique. 
         [0008]    According to one embodiment of the present disclosure, a gas supply device for sequentially supplying a first reaction gas as a process gas, a substitution gas for substituting an atmosphere, and a second reaction gas as a process gas into a process vessel, in which a substrate is placed, under a vacuum atmosphere, a plurality of cycles includes: a process gas flow passage configured to supply the process gas into the process vessel; a substitution gas flow passage configured to supply the substitution gas into the process vessel; and a substitution gas heating part installed in the substitution gas flow passage to heat the substitution gas. 
         [0009]    According to another embodiment of the present disclosure, a valve device in which a first valve body part configured to open and close a flow passage in a first valve chamber and a second valve body part configured to open and close a flow passage in a second valve chamber are successively installed includes: a first gas introduction port, a second gas introduction port, and a gas discharge port; a first gas flow passage connected to the first valve chamber from the first introduction port and opened and closed by the first valve body part; a gas discharge flow passage extending from the first valve chamber to the gas discharge port; a second gas flow passage as an inert gas flow passage configured to communicate with the gas discharge flow passage from the second gas introduction port through an orifice so as not to be opened and closed by each of the first valve body part and the second valve body part; and a bypass flow passage as a substitution gas flow passage formed to join in a downstream side of the orifice in the second gas flow passage from the second gas introduction port through the second valve chamber, and opened and closed by the second valve body part. 
         [0010]    According to the present disclosure, in forming a film by alternately supplying different process gases to a substrate a plurality of times, a substitution gas for atmosphere substitution supplied into a process vessel is heated in advance by a substitution gas heating part between the supply of one process gas and the supply of the other process gas. Thus, since a flow rate of the substitution gas can be increased, while suppressing cooling of a gas contact portion such as an inner wall of the process vessel or the substrate, it is possible to shorten the time necessary for substituting an atmosphere, contribute to enhancement of throughput, and suppress occurrence of a problem such as adhesion of a reaction product due to the cooling of the gas contact portion. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a cross-sectional view of an ALD device having a gas supply device used in an embodiment of the present disclosure. 
           [0012]      FIG. 2  is a cross-sectional view illustrating a valve device according to an embodiment of the present disclosure. 
           [0013]      FIG. 3  is a timing chart illustrating a gas supply sequence in the embodiment of the present disclosure. 
           [0014]      FIG. 4  is an explanatory view illustrating supply of a gas by the gas supply device according to the embodiment of the present disclosure. 
           [0015]      FIG. 5  is an explanatory view illustrating supply of a gas by the valve device. 
           [0016]      FIG. 6  is an explanatory view illustrating supply of a gas by the gas supply device according to the embodiment of the present disclosure. 
           [0017]      FIG. 7  is an explanatory view illustrating supply of a gas by the valve device. 
           [0018]      FIG. 8  is an explanatory view illustrating supply of a gas by the gas supply device according to the embodiment of the present disclosure. 
           [0019]      FIG. 9  is an explanatory view illustrating supply of a gas by the valve device. 
           [0020]      FIG. 10  is an explanatory view illustrating supply of a gas by the gas supply device according to the embodiment of the present disclosure. 
           [0021]      FIG. 11  is an explanatory view illustrating supply of a gas by the gas supply device according to the embodiment of the present disclosure. 
           [0022]      FIG. 12  is a cross-sectional view illustrating another example of the valve device used in the embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    An embodiment in which a gas supply device according to an embodiment of the present disclosure is applied to an ALD device as a film forming device for forming a film on a substrate will be described.  FIG. 1  illustrates an overall configuration of the ALD device. The ALD device includes a device main body part  200  and a gas supply device  100 , and is configured to form a TiN film through an ALD method by alternately supplying a TiCl 4  gas and an NH 3  gas to a surface of a wafer W as a substrate. 
         [0024]    The device main body part  200  includes a process vessel  10  serving as a vacuum chamber, a mounting table  2 , which is configured to be moved up and down by an elevation mechanism  24  through an elevation shaft  23 , is installed between a processing position for performing a film forming process on the wafer W and an exchange position for exchanging the wafer W within the process vessel  10 , and a heater  21  is embedded in the mounting table  2 . In the exchange position, the wafer W is exchanged between, for example, three push-up pins  27  for pushing up the wafer W through a hole portion  22  formed in the mounting table  2  by a push-up mechanism  28 , and a transfer mechanism (not shown), which is installed in, for example, an external vacuum transfer chamber and enters through a loading/unloading port  11 , which is opened and closed by a gate valve  12 . 
         [0025]      FIG. 1  illustrates a state where the mounting table  2  is placed in the processing position, and an upper space and a lower space of the mounting table  2  is partitioned with a gap  33  therebetween by the mounting table  2 , a cylindrical cover member  20  installed around the mounting table  2  and an annular partition member  45  of a side of the process vessel  10 . A lower surface of a ceiling portion  3  of the process vessel  10  widens from a central portion toward a lower side slantingly to form a flat conical space, and a space between the ceiling portion  3  and the mounting table  2  becomes a processing space  30 . Two gas supply paths  31  and  32  that pass through in a thickness direction are formed in the central portion of the ceiling portion  3 , and a dispersion plate  36  for dispersing a gas discharged from the gas supply paths  31  and  32  into the processing space  30  is installed, for example, horizontally, in a lower side of the gas supply paths  31  and  32 . 
         [0026]    An exhaust duct  4  is installed to be bent in an annular shape to surround the ambience of the processing space  30 . An inner peripheral surface of the exhaust duct  4  is opened in a circumferential direction, and a gas flowing from the processing space  30  is exhausted into the exhaust duct  4 . An exhaust pipe  42  is connected to an outer peripheral surface of the exhaust duct through an exhaust port  41  that passes through the process vessel  10 . The exhaust pipe  42  is connected to a vacuum exhaust pump  40  from a side of the exhaust port  41  through a pressure regulating part  43  and an opening/closing valve  44 . 
         [0027]    Further, a temperature rising mechanism such as a heater (not shown) is installed within a sidewall of the process vessel  10  or within the ceiling portion  3 , and an internal temperature of the ceiling portion  3  and the process vessel  10  is set to, for example, 150 degrees C. Thus, for example, adsorption of the process gas in the process vessel  10  is suppressed. 
         [0028]    The gas supply device  100 , which is configured to supply a TiCl 4  gas as a raw material gas, an NH 3  gas as a reaction gas, and an inert gas, for example, an N 2  gas, as an anti-backflow gas or a substitution gas, is connected to the gas supply paths  31  and  32 . The TiCl 4  gas as the raw material gas corresponds to a first reaction gas and the NH 3  gas as the reaction gas corresponds to a second reaction gas. 
         [0029]    The gas supply device  100  includes a TiCl 4  gas flow passage  80  as a raw material gas flow passage for supplying the TiCl 4  gas, an NH 3  gas flow passage  82  as a reaction gas flow passage for supplying the NH 3  gas, and two N 2  gas flow passages  8  and  81  for supplying the N 2  gas. 
         [0030]    An N 2  gas supply source  83 , a pressure regulating part  85 , a base valve V 3  and a substitution gas heating part  54  are installed in the N 2  gas flow passage  8  in this order from an upstream side, and a downstream side thereof is connected to the valve device  1 . Similarly, an N 2  gas supply source  84 , a pressure regulating part  86 , a base valve V 6 , and a substitution gas heating part  64  are also installed in the N 2  gas flow passage  81  in this order from the upstream side, and a downstream side thereof is connected to the valve device  1 . The substitution gas heating parts  54  and  64  have a cylindrical vessel formed to allow a gas to flow in a spiral shape, and a heater for heating the interior of the flow passage from the outside of the flow passage, and heat the N 2  gas to, for example, 180 degrees C. to 300 degrees C. 
         [0031]    A TiCl 4  storage part  87  is installed in the TiCl 4  gas flow passage  80 , and heated by a heater (not shown) to 80 to 90 degrees C. such that TiCl 4  is stored in a liquid state. Further, a carrier gas supply part  90  is connected to the TiCl 4  storage part  87 , and it is configured such that a raw material stored in the TiCl 4  storage part  87  is supplied by the N 2  gas or the like (for example, a flow rate of 50 sccm) supplied from the carrier gas supply part  90 . In addition, a flow rate adjusting part  91  for controlling a flow rate of the carrier gas is installed, and a vaporization amount of the TiCl 4  gas is adjusted by a flow rate of the carrier gas, so that a flow rate of the TiCl 4  gas is adjusted. An NH 3  gas supply source  89  and a flow rate adjusting part  88  are installed in the NH 3  gas flow passage  82  in this order from the upstream side. A downstream side of the TiCl 4  storage part  87  and a downstream side of the flow rate adjusting part  88  in the NH 3  gas flow passage  82  are connected to the valve device  1 . 
         [0032]    In  FIG. 1 , a portion surrounded by the dashed dotted line illustrates the flow passage or the like within the valve device  1  as a piping diagram, and  FIG. 2  illustrates a structure of the valve device  1 . The valve device  1  is constituted in a single component in which a hole passage forming a gas flow passage is formed within a block body  7 , which is formed of, for example, stainless steel or the like, and has a substantially rectangular shape, and a flow passage opening/closing part including first and second valve sheets  57   a  and  57   b  and first and second valve body parts  59   a  and  59   b  connected to the hole passage is formed. In  FIG. 1 , within the valve device  1 , a portion corresponding to the flow passage opening/closing part including the first valve sheet  57   a  and the first valve body part  59   a  is indicated as a valve V 1  and a portion corresponding to the flow passage opening/closing part including the second valve sheet  57   b  and the second valve body part  59   b  is indicated as a valve V 2 . Further, in an NH 3  supply system side, a portion corresponding to the valve V 1  is indicated as a valve V 4 , and a portion corresponding to the valve V 2  is indicated as a valve V 5 . 
         [0033]    In the valve device  1 , a TiCl 4  gas system portion, which joins the TiCl 4  gas flow passage  80 , is configured as a structure having a 2-way valve as illustrated in  FIG. 2 , and a portion formed as an NH 3  gas system portion, which joins the NH 3  gas flow passage  82 , is also configured as the same structure as that illustrated in  FIG. 2 . The structure configured as the NH 3  gas system portion is arranged in a horizontal direction of a space with the structure forming the TiCl 4  gas system portion illustrated in  FIG. 2  to be integrated in this example. Thus, the valve device  1  may be a structure having a 4-way valve including two structures, each having the 2-way valve. The structure forming the TiCl 4  gas system portion corresponds to a first valve part and the structure forming the NH 3  gas system portion corresponds to a second valve part. Thus, regarding the structure of the valve device  1 , only the structure (first valve) forming the TiCl 4  gas system portion will be described with reference to  FIG. 2 . 
         [0034]    The valve device  1  has the block body  7 , and a TiCl 4  gas introduction hole  74  as a first gas introduction port through which a TiCl 4  gas is introduced, and an N 2  gas introduction hole  75  as a second gas introduction port through which an N 2  gas is introduced, are formed to be parallel to each other on the side of the block body  7 . 
         [0035]    A process gas flow passage  5  in which the TiCl 4  gas introduction hole  74  is opened on the side thereof and which extends upwardly is formed in the block body  7 . Further, a first valve chamber  58   a  having a cylindrical shape in which the process gas flow passage  5  as a first reaction gas flow passage is opened on a lower surface thereof is formed within the block body  7 . In the first valve chamber  58   a , the annular first valve sheet  57   a  is installed to surround the opening of the process gas flow passage  5 , and the first valve body part  59   a  for opening and closing the first valve sheet  57   a  is disposed. The first valve body part  59   a  is connected to a driving part  72   a  disposed on an upper surface side of the block body  7 . The driving part  72   a  movers up and down the first valve body part  59   a  within the first valve chamber  58   a . The first valve body part  59   a  is a member having a mushroom shape in which a front end of a cylinder is curved to have a hemispherical shape, and is disposed such that the front end thereof faces downwardly. 
         [0036]    Further, a gas discharge flow passage  55  extends downwardly from a peripheral portion of a lower surface of the first valve chamber  58   a , and is connected to the gas discharge hole  76 , which is a gas discharge port, through the lower surface of the block body  7 . 
         [0037]    A bypass flow passage  51  illustrated in  FIG. 1  in which the N 2  gas introduction hole  75  is opened on the side thereof and which extends upwardly is formed in the block body  7 . A second valve chamber  58   b  having a cylindrical shape in which the bypass flow passage  51  is opened on a lower surface thereof is formed within the block body  7 . In the second valve chamber  58   b , the annular second valve sheet  57   b  is installed to surround the opening of the bypass flow passage  51 , and a second valve body part  59   b  for opening and closing the second valve sheet  57   b  is disposed. The second valve body part  59   b  is connected to a driving part  72   b  disposed on an upper surface side of the block body  7 . The driving part  72   b  moves up and down the second valve body part  59   b  within the second valve chamber  58   b.    
         [0038]    Further, the opening of the bypass flow passage  51  in the second valve chamber  58   b  is blocked by an orifice forming member  53   a  having a disk shape, and a hole portion forming an orifice  53  having a caliber of 0.1 to 1.0 mm is formed in the orifice forming member  53   a . The orifice forming part  53   a  may also be used as the second valve sheet  57   b.    
         [0039]    In addition, an N 2  gas introduction passage  50  slantingly extending upwardly from the N 2  gas introduction hole  75  and connected to a peripheral portion of the second valve chamber  58   b  is formed in the block body  7 . In the second valve chamber  58   b , the opening of the N 2  gas introduction passage  50  is blocked by the orifice forming member  52   a  having a disk shape, and a hole portion forming the orifice  52  having a caliber of 0.1 to 1.0 mm is formed in the orifice forming member  52   a . Further, a V-shaped flow passage  56  is formed in a peripheral portion of a lower surface of the second valve chamber  58   b , and slantingly extends toward a lower side and then slantingly changes direction toward an upper side so as to be connected to a peripheral portion of a lower surface of the first valve chamber  58   a.    
         [0040]    In the valve device  1 , a flow passage of the TiCl 4  gas introduction hole  74 →first valve chamber  58   a →gas discharge flow passage  55 →gas discharge hole  76  corresponds to a portion from the TiCl 4  gas introduction hole  74  of the TiCl 4  gas flow passage  80  to the gas discharge hole  76  illustrated in  FIG. 1 . Further, a flow passage of the N 2  gas introduction hole  75 →N 2  gas introduction path  50  and bypass flow passage  51 →second valve chamber  58   b →V-shaped flow passage  56 →first valve chamber  58   a →gas discharge flow passage  55 →gas discharge hole  76  corresponds to a portion from the N 2  gas introduction hole  75  of the N 2  gas flow passage  8  to the gas discharge hole  76  illustrated in  FIG. 1 . 
         [0041]    Further, in the following description of operation, opening the valve V 1  (or V 2 ) refers to a state where the first valve body part  59   a  (or the second valve body part  59   b ) is spaced apart from the first valve sheet  57   a  (or the second valve sheet  57   b ). Also, closing the valve V 1  (or V 2 ) refers to a state where the first valve body part  59   a  (or the second valve body part  59   b ) is moved down to be seated on the first valve sheet  57   a  (or the second valve sheet  57   b ). 
         [0042]    As illustrated in  FIG. 1 , the valve device  1  installed in a portion where the NH 3  gas flow passage  82  and the N 2  gas flow passage  81  join is configured to have a mirror plane symmetry with respect to the line I-I′ of  FIG. 2 , except that the first gas introduction port is formed as an NH 3  gas introduction hole  78  and, instead of the TiCl 4  gas, an NH 3  gas is supplied, as illustrated in  FIG. 1 . Further, in  FIG. 1 , reference numeral  79  denotes a gas discharge hole, reference numeral  77  denotes an N 2  gas introduction hole, reference numeral  60  denotes an N 2  gas introduction path, and reference numeral  63  denotes an orifice installed in a bypass flow passage  61 . Further, in the valve device  1 , for example, a heating mechanism  71  having an aluminum jacket and a mantle heater is installed to surround the block body  7 , and a wall surface of a gas flow passage in the valve device  1  is heated to have a temperature of, for example, 150 degrees C. 
         [0043]    In addition, the ALD device includes a control part  9 . The control part  9  is configured as, for example, a computer, and includes a program, a memory, and a CPU. The program has a group of steps S embedded to perform a series of operations in the following description of operations, and an opening/closing operation of each valve V 1  to V 6 , a flow rate adjusting operation of each gas, a pressure regulating operation of an internal pressure of the process vessel  10  and the like are executed according to the program. The program is stored in a computer storage medium, for example, a flexible disc, a compact disc, a hard disc, a magneto-optical disc, or the like and installed in the control part  9 . 
         [0044]    Next, an operation of the embodiment of the present disclosure will be described.  FIG. 3  is a timing chart of opening/closing of each valve V 1  to V 6  (supply/stop of gas) in an ALD film forming process. Further,  FIGS. 4, 6, 8, 10, and 11  are views illustrating a state where a gas is supplied from the gas supply device  100  into the process vessel  10 , and  FIGS. 5, 7, and 9  illustrate an operation of the valve device  1  when a gas is supplied. Also, in  FIGS. 4, 6, 8, 10 , and  11 , the device main body part  200  is simplified to facilitate understanding of the described content. Also, the opening diameter of the orifice  53  is exaggerated. Further, in the explanatory drawings illustrating the gas supply after  FIG. 4 , hatching is illustrated in a closed valve for convenience. 
         [0045]    First, after the wafer W is mounted on the mounting table  2  by a transfer mechanism within an external vacuum transfer chamber (not shown), the gate valve  12  is closed and the wafer W is heated by the heater  21  installed in the mounting table  2  to, for example, 350 degrees C. Further, a temperature of a wall surface of the process vessel  10  is set to, for example, 170 degrees C. by a heater (not shown) installed in the process vessel  10 . 
         [0046]    Further, at time t 0  illustrated in  FIG. 3 , the base valves V 3  and V 6  of the N 2  gas flow passages  8  and  81  are opened as illustrated in  FIG. 4 . At this time, as can be seen from  FIG. 5 , although the valve V 2  is closed, the N 2  gas introduced through the N 2  gas introduction hole  75  within the valve device  1  passes through the N 2  gas introduction path  50 , the orifice  52 , the second valve chamber  58   b , the V-shaped flow passage  56 , the first valve chamber  58   a , the gas discharge flow passage  55 , and the gas discharge hole  76 . Thus, the N 2  gas is supplied from the N 2  gas supply sources  83  and  84  into the process vessel  10  through the N 2  gas flow passages  8  and  81  and the gas supply paths  31  and  32 , respectively. The N 2  gas introduction path  50  and the orifice  52  correspond to a first inert gas flow passage. The N 2  gas is heated by the substitution gas heating parts  54  and  64  to, for example, 300 degrees C., and is also set to a flow rate of, for example, 3000 sccm, in each of the N 2  gas flow passages  8  and  81 . 
         [0047]    Subsequently, the mounting table  2  is moved up to the processing position indicated by the solid line in  FIG. 1  to form the processing space  30 , and thereafter, the valve V 1  is opened at time t 1  at step S 1  as illustrated in  FIG. 6 . In the valve device  1 , as illustrated in  FIG. 7 , the first valve body part  59   a  is moved up and a TiCl 4  gas is supplied from the process gas flow passage  5  to the first valve chamber  58   a . Further, the N 2  gas introduced through the V-shaped flow passage  56  and flowing to the gas discharge flow passage  55  through the first valve chamber  58   a  join with the TiCl 4  gas in the first valve chamber  58   a . Accordingly, the TiCl 4  gas, together with the N 2  gas as an inert gas, is introduced from the gas supply path  31  into the process vessel  10  and supplied to the wafer W. At this time, since the N 2  gas flows through the gas supply path  32 , the TiCl 4  gas is suppressed from flowing backwards to the corresponding gas supply path  32 . Thus, the N 2  gas flowing through the gas supply path  32  may be considered an anti-backflow gas. Further, the N 2  gas flowing through the gas supply path  31  is also a gas for preventing backflow of a gas from a process atmosphere. 
         [0048]    At time t 2  after 0.05 to 0.5 seconds has elapsed from the time t 1 , the valve V 1  is closed and the valve V 2  is opened at step S 2 . Thus, as illustrated in  FIG. 8 , the supply of the TiCl 4  gas is stopped and the N 2  gas as a heated substitution gas is introduced into the process vessel  10  through the N 2  gas flow passages  8  and  81 , the valve device  1 , and the gas supply paths  31  and  32 . The N 2  gas will be described in detail. As illustrated in  FIG. 9 , as the second valve body part  59   b  of the valve V 2  is moved up, the N 2  gas which has been introduced through the N 2  gas introduction hole  75  is introduced to the second valve chamber  58   b  through the bypass flow passage  51  and the orifice  53  and joins the N 2  gas which has come through the orifice  52  described above. The bypass flow passage  51  and the orifice  53  correspond to the first substitution gas flow passage. 
         [0049]    The joined N 2  gas is introduced, at a flow rate greater than that of the N 2  gas serving as an anti-backflow gas when a TiCl 4  gas is supplied or when an NH 3  gas is supplied, for example, at a flow rate of 10000 sccm, from the valve device  1  into the process vessel  10  through the gas supply path  31 . At this time, the N 2  gas is also continuously discharged from the gas supply path  32 . Thus, these N 2  gases serve as substitution gases for substituting an internal atmosphere of the process vessel  10  or supply paths of the process gases such as the gas supply paths  31  and  32  during an idle time in intermittent supply of the process gases (TiCl 4  gas and NH 3  gas). 
         [0050]    Thereafter, at step S 3 , as illustrated in  FIG. 10 , the valve V 2  is closed and the valve V 4  is opened from time t 3  after 0.1 to 0.5 seconds have lapsed from the time t 2 . At this time, like the TiCl 4  gas illustrated in  FIG. 7 , the NH 3  gas flows in the valve device  1  of the NH 3  gas system side and is introduced together with the N 2  gas as an inert gas into the process vessel  10  through the gas supply path  32 , and supplied to the wafer W. At this time, since the N 2  gas flows through the gas supply path  31 , the NH 3  gas is suppressed from being introduced to the corresponding gas supply path  31 . Thus, the gas flowing through the gas supply path  31  may be an anti-backflow gas. Also, the N 2  gas flowing through the gas supply path  32  is a gas preventing backflow of a process atmosphere. 
         [0051]    Further, the valve V 4  is closed and the valve V 5  is opened at step S 4  from time t 4  after 0.05 to 0.5 seconds have lapsed from the time t 3 . Thus, as illustrated in  FIG. 11 , the supply of the NH 3  gas is stopped and the N 2  gas as a heated substitution gas is introduced into the process vessel  10  through the N 2  gas flow passages  8  and  81 , the valve device  1 , and the gas supply paths  31  and  32 . At this time, the N 2  gas flows within the valve device  1  on the NH 3  gas system portion as in  FIG. 9 , and the N 2  gas of, for example, 10000 sccm is introduced as a substitution gas into the process vessel  10 . 
         [0052]    Further, a cycle including supply of TiCl 4  gas→substitution by N 2  gas→supply of NH 3  gas→substitution of process atmosphere by N 2  gas from step S 1  to step S 4  is repeated a preset number of times, for example, 20 times after time t 5 . By repeating the cycle, a TiCl 4  gas is adsorbed onto the wafer W, the TiCl 4  gas and the NH 3  gas are subsequently reacted to create a molecular layer of TiN, and the molecular layer of TiN is sequentially stacked to form a TiN film. 
         [0053]    After the supply cycle is repeated a preset number of times, the N 2  gas is supplied into the process vessel  10  for a while, and thereafter, the mounting table  2  is moved down to a loading/unloading position and the gate valve  12  is opened to unload the wafer W from the process vessel  1 . 
         [0054]    In the aforementioned embodiment, in performing the ALD, the N 2  gas as a substitution gas for substituting an atmosphere is dedicatedly heated by the substitution gas heating parts  54  and  64  independent from the valve device  1 . The valve device  1  is also heated by the heating mechanism  71  to promote release of gas from a gas contact portion, however, a heating temperature thereof is limited in consideration of heat resistance of a seal material, and thus, a temperature rises only to, for example, about 150 degrees C. In contrast, when the dedicated substitution gas heating parts  54  and  64  are used, a temperature of the N 2  gas can be increased up to a temperature enough to suppress a cooling operation of a gas contact portion when a large amount of N 2  gas enough to increase substitution efficiency is supplied. 
         [0055]    In the ALD, the time necessary for substituting an atmosphere between a raw material gas (first reaction gas) as a process gas and a reaction gas as (second reaction gas), for example, between the TiCl 4  gas and the NH 3  gas, affects the throughput. In this embodiment, since a large amount of N 2  gas can be supplied, an atmosphere can be substituted within a short time, promoting the enhancement of throughput. Further, when the temperature of a gas contact portion is lowered, as mentioned above, any one of the TiCl 4  gas and the NH 3  gas adheres to an inner wall of the process vessel  10  to remain thereon and reacts with the other gas to cause a particle to be formed. The present inventor recognized that an adsorption probability of the NH 3  gas is reduced as a temperature is higher and increased as a temperature is lower, between 150 degrees C. to 400 degrees C. Further, when the TiCl 4  gas and the NH 3  gas adhere to the gas supply paths  31  and  32 , respectively, there is a possibility that the NH 3  gas flows backwards to the gas supply path  31  or the TiCl 4  gas flows backwards to the gas supply path  32 , causing a reaction within the gas supply paths  31  and  32 . In addition, the TiCl 4  gas may be re-liquefied on an inner wall of the process vessel  10  or within the gas supply path  31 . According to the aforementioned embodiment, this problem can be solved, while allowing a large amount of substitution gas to flow. 
         [0056]    Further, the N 2  gas for preventing a backflow is supplied into the gas supply paths  31  and  32 , and the bypass flow passages  51  and  61  are installed to bypass the orifices  52  and  62  for regulating a flow rate of the N 2  gas for preventing a backflow, such that the N 2  gas as a substitution gas can be supplied or stopped separately from the N 2  gas for preventing a backflow. Thus, when the TiCl 4  gas and the NH 3  as process gases are supplied, a partial pressure of these process gases can be lowered to avoid lowering of a deposition rate. Further, the valve device  1 , which is a so-called multi-way valve in which the valves V 1  and V 4  for the process gas and the valves V 2  and V 5  for the N 2  gas are successively installed, is used. In addition, a substitution gas is supplied or stopped using the second valve body  59   b  and the second valve sheet  57   b  such that the bypass flow passages  51  and  61  of the N 2  gas as a substitution gas bypass with respect to the N 2  gas introduction paths  50  and  60  as a portion of the N 2  gas flow passage for preventing a backflow in the valve device  1 . Also, these N 2  gas introduction paths  50  and  60  and the bypass flow passages  51  and  61  join in the gas discharge flow passage  55  (see  FIG. 2 ) of the process gas. Thus, the gas supply device is advantageously reduced in size. 
         [0057]    The present disclosure is not limited to the aforementioned embodiment, and for example, modifications as described later may be configured. 
         [0058]    In the valve device  1 , as illustrated in  FIG. 12 , the gas flow passage  50  of the N 2  gas for preventing a backflow may be connected to the V-shaped flow passage  56  through the orifice  92 , or instead of the structure illustrated in  FIG. 12 , the N 2  gas introduction path  50  may be directly connected to the gas discharge flow passage  55  through the orifice, rather than being connected to the V-shaped flow passage  56 . Further, an outlet of a flow passage corresponding to the V-shaped flow passage  56  illustrated in  FIG. 2 , namely, an outlet of a flow passage after the N 2  gas for preventing a backflow and the N 2  gas as a substitution gas join may be opened to the gas discharge flow passage  55 , without passing through the first valve chamber  58   a.    
         [0059]    Also, rather than being connected to the second valve chamber  58   b , the N 2  gas introduction path  50  of the N 2  gas for preventing a backflow may be directly connected to the first valve chamber  58   a  so as not to be opened and closed by the first valve body part  59   a , and the flow passage corresponding to the V-shaped flow passage  56  extending from the second valve chamber  58   b  as described above may be directly connected to the gas discharge flow passage  55 , without passing through the first valve chamber  58   a . In this case, the orifice  52  installed in the N 2  gas introduction path  50  may be configured by applying the same structure as that illustrated in  FIG. 2  to an inner wall part of the first valve chamber  58   a . Further, the N 2  gas introduction path  50  and the bypass flow passage  51  may join in the gas discharge flow passage  55 . When the orifice  52  is configured by the orifice forming member  52   a  in the inner wall part of the valve chambers  58   a  and  58   b , a processing operation is facilitated. 
         [0060]    The substitution gas heating parts  54  and  64  of a gas may also be installed in a downstream side of the valve device  1 , as well as being installed in an upstream side of the valve device  1 . 
         [0061]    In the aforementioned embodiment, the valve device (equivalent to the first valve part) of the TiCl 4  gas system side is illustrated in  FIG. 2 , but actually, as mentioned above, the valve device (equivalent to the second valve part) of the NH 3  gas system side may also have the same structure as that illustrated in  FIG. 2 , and the valve device  1  illustrated in  FIG. 1  is configured by integrating those two valve devices. However, in the valve device  1 , the valve device on the TiCl 4  gas system side and the valve device on the NH 3  gas system side may also be separately provided. 
         [0062]    As a type of film forming process, a silicon oxide film may be formed using an organic silicon source as a raw material gas and an ozone gas as a reaction gas, without being limited to the TiCl 4  gas and the NH 3  gas. Alternatively, a so-called SiN film may also be formed using a silane-based gas such as a dichlorosilane gas as a raw material gas and an NH 3  gas as a reaction gas, or the like. 
         [0063]    Further, the present disclosure is not limited to the case of performing ALD. For example, a first CVD film may be formed by supplying a process gas for first CVD into the process vessel and a second CVD film is subsequently formed by using a process gas for a second CVD different from the process gas for the first CVD. In this manner, the present disclosure may also be applied to a method of forming a thin film by alternately supplying both process gases into the process vessel  10  a plurality of times through substitution of an atmosphere by a substitution gas. In this case, the process gas for the first CVD corresponds to the first reaction gas and the process gas for the second CVD corresponds to the second reaction gas. 
         [0064]    Regarding a flow passage of the N 2  gas as a substitution gas, a dedicated flow passage, separated from the flow passages through which the N 2  gas for preventing a backflow and the process gas flow, may be installed to supply the same into the process vessel  10 . 
       INDUSTRIAL USE OF THE PRESENT DISCLOSURE 
       [0065]    The present disclosure can be effective in the field of a gas supply device used to perform a film forming process on a substrate, and thus has industrial applicability. 
       EXPLANATION OF REFERENCE NUMERALS 
       [0066]      2 : mounting table,  9 : control part,  10 : process vessel,  12 : gate valve,  21 : heater,  23 : elevation shaft,  24 : elevation mechanism,  28 : push-up mechanism,  40 : vacuum exhaust pump