Patent Publication Number: US-11664217-B2

Title: Method of manufacturing semiconductor device, substrate processing method, substrate processing apparatus, and recording medium

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This non-provisional U.S. patent application is a continuation of U.S. patent application Ser. No. 16/988,235, filed on Aug. 7, 2020, which is a continuation of U.S. patent application Ser. No. 16/286,292, filed on Feb. 26, 2019, which issued as U.S. Pat. No. 10,770,287 on Sep. 8, 2020, and claims the benefit of priority from Japanese Patent Application No. 2018-034770, filed on Feb. 28, 2018, the entire contents of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a method of manufacturing a semiconductor device, a substrate processing apparatus, and a recording medium. 
     BACKGROUND 
     In a related art, as an example of a process of manufacturing a semiconductor device, a process of forming a film containing silicon (Si) and nitrogen (N), i.e., a silicon nitride film (SiN film), on a substrate is carried out. 
     SUMMARY 
     The present disclosure provides some embodiments of a technique that improves film thickness uniformity of a SiN film formed on a substrate in a plane of the substrate. 
     According to an embodiment of the present disclosure, there is provided a technique, which includes: (a) forming NH termination on a surface of a substrate by supplying a first reactant containing N and H to the substrate; (b) forming a first SiN layer having SiCl termination formed on its surface by supplying SiCl 4  as a precursor to the substrate to react the NH termination formed on the surface of the substrate with the SiCl 4 ; (c) forming a second SiN layer having NH termination formed on its surface by supplying a second reactant containing N and H to the substrate to react the SiCl termination formed on the surface of the first SiN layer with the second reactant; and (d) forming a SiN film on the substrate by performing a cycle a predetermined number of times under a condition where the SiCl 4  is not gas-phase decomposed after performing (a), the cycle including non-simultaneously performing (b) and (c). 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a schematic configuration diagram of a vertical type process furnace of a substrate processing apparatus suitably used in an embodiment of the present disclosure, in which a portion of the process furnace is shown in a vertical cross sectional view. 
         FIG.  2    is a schematic configuration diagram of a vertical type process furnace of the substrate processing apparatus suitably used in an embodiment of the present disclosure, in which a portion of the process furnace is shown in a cross sectional view taken along line A-A in  FIG.  1   . 
         FIG.  3    is a schematic configuration diagram of a controller of the substrate processing apparatus suitably used in one embodiment of the present disclosure, in which a control system of a controller is shown in a block diagram. 
         FIG.  4    is a diagram illustrating a film-forming sequence according to an embodiment of the present disclosure. 
         FIG.  5 A  illustrates a partial enlarged view of a surface of a substrate after a first reactant is supplied,  FIG.  5 B  illustrates a partial enlarged view of a surface of a substrate after a precursor is supplied, and  FIG.  5 C  illustrates a partial enlarged view of a surface of a substrate after a second reactant is supplied. 
         FIG.  6 A  is a diagram illustrating an evaluation result of film thickness uniformity of a SiN film formed on a substrate in a plane of the substrate, and  FIG.  6 B  is a diagram illustrating an evaluation result of processing resistance of a SiN film formed on the substrate. 
         FIG.  7    is a diagram illustrating an evaluation result of film thickness uniformity of a SiN film formed on a substrate in the plane of the substrate. 
     
    
    
     DETAILED DESCRIPTION 
     One Embodiment of the Present Disclosure 
     An embodiment of the present disclosure will now be described in detail mainly with reference to  FIGS.  1  to  5 C . 
     (1) Configuration of the Substrate Processing Apparatus 
     As illustrated in  FIG.  1   , a process furnace  202  includes a heater  207  as a heating mechanism (temperature adjustment part). The heater  207  has a cylindrical shape and is supported by a holding plate so as to be vertically installed. The heater  207  functions as an activation mechanism (an excitation part) configured to thermally activate (excite) a gas. 
     A reaction tube  203  is disposed inside the heater  207  to be concentric with the heater  207 . The reaction tube  203  is made of a heat resistant material, e.g., quartz (SiO 2 ), silicon carbide (SiC) or the like, and has a cylindrical shape with its upper end closed and its lower end opened. A process chamber  201  is formed in a hollow cylindrical portion of the reaction tube  203 . The process chamber  201  is configured to accommodate wafers  200  as substrates. The processing of the wafers  200  is performed in the process chamber  201 . 
     Nozzles  249   a  and  249   b  are installed in the process chamber  201  so as to penetrate a lower sidewall of the reaction tube  203 . Gas supply pipes  232   a  and  232   b  are respectively connected to the nozzles  249   a  and  249   b.    
     Mass flow controllers (MFCs)  241   a  and  241   b , which are flow rate controllers (flow rate control parts), and valves  243   a  and  243   b , which are opening/closing valves, are installed in the gas supply pipes  232   a  and  232   b  sequentially from the corresponding upstream sides of gas flow, respectively. Gas supply pipes  232   c  and  232   d  are respectively connected to the gas supply pipes  232   a  and  232   b  at the downstream side of the valves  243   a  and  243   b . MFCs  241   c  and  241   d  and valves  243   c  and  243   d  are respectively installed in the gas supply pipes  232   c  and  232   d  sequentially from the corresponding upstream sides of gas flow. 
     As illustrated in  FIG.  2   , the nozzles  249   a  and  249   b  are disposed in a space with an annular plan-view shape between the inner wall of the reaction tube  203  and the wafers  200  such that the nozzles  249   a  and  249   b  extend upward along an arrangement direction of the wafers  200  from a lower portion of the inner wall of the reaction tube  203  to an upper portion of the inner wall of the reaction tube  203 . Specifically, the nozzles  249   a  and  249   b  are installed at a lateral side of a wafer arrangement region in which the wafers  200  are arranged, namely in a region which horizontally surrounds the wafer arrangement region, so as to extend along the wafer arrangement region. Gas supply holes  250   a  and  250   b  for supplying a gas are installed on the side surfaces of the nozzles  249   a  and  249   b , respectively. The gas supply holes  250   a  and  250   b  are opened toward the center of the reaction tube  203  so as to allow a gas to be supplied toward the wafers  200 . The gas supply holes  250   a  and  250   b  may be formed in a plural number between the lower portion of the reaction tube  203  and the upper portion of the reaction tube  203 . 
     A precursor (precursor gas), for example, a chlorosilane-based gas which contains silicon (Si) and chlorine (Cl), is supplied from the gas supply pipe  232   a  into the process chamber  201  via the MFC  241   a , the valve  243   a , and the nozzle  249   a . The precursor gas refers to a gaseous precursor, for example, a gas obtained by vaporizing a precursor which remains in a liquid state under a room temperature and an atmospheric pressure, or a precursor which remains in a gas state under a room temperature and an atmospheric pressure. As the chlorosilane-based gas, it may be possible to use, for example, a tetrachlorosilane (SiCl 4 ) gas. The SiCl 4  gas contains four chemical bonds (Si—Cl bonds) of Si and Cl in one molecule. 
     A hydrogen nitride-based gas containing, for example, nitrogen (N) and hydrogen (H), as first and second reactants, is supplied from the gas supply pipe  232   b  into the process chamber  201  via the MFC  241   b , the valve  243   b , and the nozzle  249   b . As the hydrogen nitride-based gas, it may be possible to use, for example, an ammonia (NH 3 ) gas. The NH 3  gas contains three chemical bonds (N—H bonds) of N and H in one molecule. 
     A nitrogen (N 2 ) gas as an inert gas is supplied from the gas supply pipes  232   c  and  232   d  into the process chamber  201  via the MFCs  241   c  and  241   d , the valves  243   c  and  243   d , the gas supply pipes  232   a  and  232   b , and the nozzles  249   a  and  249   b . The N 2  gas acts as a purge gas, a carrier gas, a dilution gas, or the like. 
     A precursor supply system includes the gas supply pipe  232   a , the MFC  241   a , and the valve  243   a . A reactant supply system (first and second reactant supply systems) includes the gas supply pipe  232   b , the MFC  241   b , and the valve  243   b . An inert gas supply system includes the gas supply pipes  232   c  and  232   d , the MFCs  241   c  and  241   d , and the valves  243   c  and  243   d.    
     One or all of various supply systems described above may be configured as an integrated supply system  248  in which the valves  243   a  to  243   d , the MFCs  241   a  to  241   d , and the like are integrated. The integrated supply system  248  is connected to each of the gas supply pipes  232   a  to  232   d  so that a supply operation of various kinds of gases into the gas supply pipes  232   a  to  232   d , i.e., an opening/closing operation of the valves  243   a  to  243   d , a flow rate adjusting operation by the MFCs  241   a  to  241   d  or the like, is controlled by a controller  121  which will be described later. The integrated supply system  248  is configured as an integral type or division type integrated unit, and is also configured so that it is detachable from the gas supply pipes  232   a  to  232   d  or the like, so as to perform maintenance, replacement, expansion or the like of the integrated supply system  248 , on an integrated unit basis. 
     An exhaust pipe  231  configured to exhaust an internal atmosphere of the process chamber  201  is installed at a lower side of the sidewall of the reaction tube  203 . A vacuum pump  246  as a vacuum exhaust device is connected to the exhaust pipe  231  via a pressure sensor  245  as a pressure detector (pressure detection part) which detects the internal pressure of the process chamber  201  and an auto pressure controller (APC) valve  244  as a pressure regulator (pressure regulation part). The APC valve  244  is configured so that a vacuum exhaust of the interior of the process chamber  201  and a vacuum exhaust stop can be performed by opening and closing the APC valve  244  while operating the vacuum pump  246  and so that the internal pressure of the process chamber  201  can be adjusted by adjusting an opening degree of the APC valve  244  based on pressure information detected by the pressure sensor  245  while operating the vacuum pump  246 . An exhaust system includes the exhaust pipe  231 , the pressure sensor  245  and the APC valve  244 . The vacuum pump  246  may be regarded as being included in the exhaust system. 
     A seal cap  219 , which serves as a furnace opening cover configured to hermetically seal a lower end opening of the reaction tube  203 , is installed under the reaction tube  203 . The seal cap  219  is made of a metal material such as, e.g., stainless steel (SUS) or the like, and is formed in a disc shape. An O-ring  220 , which is a seal member making contact with the lower end portion of the reaction tube  203 , is installed on an upper surface of the seal cap  219 . A rotation mechanism  267  configured to rotate a boat  217 , which will be described later, is installed under the seal cap  219 . A rotary shaft  255  of the rotation mechanism  267 , which penetrates the seal cap  219 , is connected to the boat  217 . The rotation mechanism  267  is configured to rotate the wafers  200  by rotating the boat  217 . The seal cap  219  is configured to be vertically moved up and down by a boat elevator  115  which is an elevator mechanism installed outside the reaction tube  203 . The boat elevator  215  is configured as a transfer device (transfer mechanism) which loads and unloads (transfers) the wafers  210  into and from (out of) the process chamber  201  by moving the seal cap  219  up and down. 
     The boat  217  serving as a substrate support is configured to support a plurality of wafers  200 , e.g.,  25  to  200  wafers, in such a state that the wafers  200  are arranged in a horizontal posture and in multiple stages along a vertical direction with the centers of the wafers  200  aligned with one another. That is, the boat  217  is configured to arrange the wafers  200  in a spaced-apart relationship. The boat  217  is made of a heat resistant material such as quartz or SiC. Heat insulating plates  218  made of a heat resistant material such as quartz or SiC are installed below the boat  217  in a horizontal posture and in multiple stages. 
     A temperature sensor  263  serving as a temperature detector is installed in the reaction tube  203 . Based on temperature information detected by the temperature sensor  263 , a state of supplying electric power to the heater  207  is adjusted such that the interior of the process chamber  201  has a desired temperature distribution. The temperature sensor  263  is installed along the inner wall of the reaction tube  203 . 
     As illustrated in  FIG.  3   , the controller  121 , which is a control part (control means), may be configured as a computer including a central processing unit (CPU)  121   a , a random access memory (RAM)  121   b , a memory device  121   c , and an I/O port  121   d . The RAM  121   b , the memory device  121   c  and the I/O port  121   d  are configured to exchange data with the CPU  121   a  via an internal bus  121   e . An input/output device  122  formed of, e.g., a touch panel or the like, is connected to the controller  121 . 
     The memory device  121   c  is configured by, for example, a flash memory, a hard disk drive (HDD), or the like. A control program for controlling operations of a substrate processing apparatus, a process recipe for specifying sequences and conditions of a film-forming process as described hereinbelow, or the like is readably stored in the memory device  121   c . The process recipe functions as a program for causing the controller  121  to execute each sequence in the film-forming process, as described hereinbelow, to obtain a predetermined result. Hereinafter, the process recipe and the control program will be generally and simply referred to as a “program.” Furthermore, the process recipe will be simply referred to as a “recipe.” When the term “program” is used herein, it may indicate a case of including only the recipe, a case of including only the control program, or a case of including both the recipe and the control program. The RAM  121   b  is configured as a memory area (work area) in which a program, data and the like read by the CPU  121   a  is temporarily stored. 
     The I/O port  121   d  is connected to the MFCs  241   a  to  241   d , the valves  243   a  to  243   d , the pressure sensor  245 , the APC valve  244 , the vacuum pump  246 , the temperature sensor  263 , the heater  207 , the rotation mechanism  267 , the boat elevator  115 , and the like, as described above. 
     The CPU  121   a  is configured to read the control program from the memory device  121   c  and execute the same. The CPU  121   a  also reads the recipe from the memory device  121   c  according to an input of an operation command from the input/output device  122 . In addition, the CPU  121   a  is configured to control, according to the contents of the recipe thus read, the flow rate adjusting operation of various kinds of gases by the MFCs  241   a  to  241   d , the opening/closing operation of the valves  243   a  to  243   d , the opening/closing operation of the APC valve  244 , the pressure regulating operation performed by the APC valve  244  based on the pressure sensor  245 , the driving and stopping of the vacuum pump  246 , the temperature adjusting operation performed by the heater  207  based on the temperature sensor  263 , the operation of rotating the boat  217  with the rotation mechanism  267  and adjusting the rotation speed of the boat  217 , the operation of moving the boat  217  up and down with the boat elevator  115 , and the like. 
     The controller  121  may be configured by installing, on the computer, the aforementioned program stored in an external memory device  123 . The external memory device  123  may include, for example, a magnetic disc such as an HDD, an optical disc such as a CD, a magneto-optical disc such as an MO, a semiconductor memory such as a USB memory, and the like. The memory device  121   c  or the external memory device  123  is configured as a computer-readable recording medium. Hereinafter, the memory device  121   c  and the external memory device  123  will be generally and simply referred to as a “recording medium.” When the term “recording medium” is used herein, it may indicate a case of including only the memory device  121   c , a case of including only the external memory device  123 , or a case of including both the memory device  121   c  and the external memory device  123 . Furthermore, the program may be supplied to the computer using a communication means such as the Internet or a dedicated line, instead of using the external memory device  123 . 
     (2) Substrate Processing 
     A substrate processing sequence example of forming a SiN film on a wafer  200  as a substrate using the aforementioned substrate processing apparatus, i.e., a film-forming sequence example, which is one of the processes for manufacturing a semiconductor device, will be described with reference to  FIG.  4   . In the following descriptions, the operations of the respective parts constituting the substrate processing apparatus are controlled by the controller  121 . 
     In the film-forming sequence illustrated in  FIG.  4   , there are performed: step A of supplying an NH 3  gas as a first reactant containing N and H to a wafer  200  to form NH termination on a surface of the wafer  200 ; step B of supplying a SiCl 4  gas as a precursor to the wafer  200  to react the NH termination formed on the surface of the wafer  200  with SiCl 4  to form a first SiN layer having SiCl termination formed on its surface; and step C of supplying an NH 3  gas as a second reactant containing N and H to the wafer  200  to react the SiCl termination formed on the surface of the first SiN layer with the NH 3  gas to form a second SiN layer having NH termination formed on its surface. 
     Specifically, a cycle which non-simultaneously performs step B and step C described above under a condition in which SiCl 4  is not gas-phase decomposed after performing step A described above is implemented a predetermined number of times. Thus, a SiN film is formed on the wafer  200 . Furthermore, in  FIG.  4   , execution periods of steps A, B, and C are denoted as A, B, and C, respectively. 
     In the present disclosure, for the sake of convenience, the film-forming sequence illustrated in  FIG.  4    may sometimes be denoted as follows. The same denotation will be used in other embodiments and the like as described hereinbelow.
 
NH 3 →(SiCl 4 →NH 3 )× n =⇒SiN
 
     When the term “wafer” is used herein, it may refer to a wafer itself or a laminated body of a wafer and a predetermined layer or film formed on the surface of the wafer. In addition, when the phrase “a surface of a wafer” is used herein, it may refer to a surface of a wafer itself or a surface of a predetermined layer or the like formed on a wafer. Furthermore, in the present disclosure, the expression “a predetermined layer is formed on a wafer” may mean that a predetermined layer is directly formed on a surface of a wafer itself or that a predetermined layer is formed on a layer or the like formed on a wafer. In addition, when the term “substrate” is used herein, it may be synonymous with the term “wafer.” 
     (Wafer Charging and Boat Loading) 
     A plurality of wafers  200  is charged on the boat  217  (wafer charging). Thereafter, as illustrated in  FIG.  1   , the boat  217  supporting the plurality of wafers  200  is lifted up by the boat elevator  115  and is loaded into the process chamber  201  (boat loading). In this state, the seal cap  219  seals the lower end of the reaction tube  203  through the O-ring  220 . 
     (Pressure Regulation and Temperature Adjustment) 
     The interior of the process chamber  201 , namely the space in which the wafers  200  are located, is vacuum-exhausted (depressurization-exhausted) by the vacuum pump  246  so as to reach a desired processing pressure (degree of vacuum). In this operation, the internal pressure of the process chamber  201  is measured by the pressure sensor  245 . The APC valve  244  is feedback-controlled based on the measured pressure information. Furthermore, the wafers  200  in the process chamber  201  are heated by the heater  207  to a desired processing temperature (film-forming temperature). In this operation, the state of supplying electric power to the heater  207  is feedback-controlled based on the temperature information detected by the temperature sensor  263  such that the interior of the process chamber  201  has a desired temperature distribution. In addition, the rotation of the wafers  200  by the rotation mechanism  267  begins. The driving of the vacuum pump  246  and the heating and rotation of the wafers  200  may be all continuously performed at least until the processing of the wafers  200  is completed. 
     (Film-Forming Process) 
     Next, the following steps A and B are sequentially performed. 
     [Step A] 
     At this step, an NH 3  gas is supplied to the wafer  200  in the process chamber  201 . Specifically, the valve  243   b  is opened to allow an NH 3  gas to flow through the gas supply pipe  232   b . The flow rate of the NH 3  gas is adjusted by the MFC  241   b . The NH 3  gas is supplied into the process chamber  201  via the nozzle  249   b  and is exhausted from the exhaust pipe  231 . At this time, the NH 3  gas is supplied to the wafer  200  from the side of the wafer  200 . Simultaneously, the valves  243   c  and  243   d  may be opened to allow an N 2  gas to flow through the gas supply pipes  232   c  and  232   d.    
     The processing conditions at this step may be exemplified as follows: 
     NH 3  gas supply flow rate: 100 to 10,000 sccm 
     N 2  gas supply flow rate (per gas supply pipe): 0 to 10,000 sccm 
     Supply time of each gas: 1 to 30 minutes 
     Processing temperature: 300 to 1,000 degrees C., 700 to 900 degrees C. in some embodiments, or 750 to 800 degrees C. in some embodiments 
     Processing pressure: 1 to 4,000 Pa or 20 to 1,333 Pa in some embodiments. 
     Furthermore, in the present disclosure, the expression of the numerical range such as “300 to 1,000 degrees C.” may mean that a lower limit value and an upper limit value are included in that range. Therefore, “300 to 1,000 degrees C.” may mean “300 degrees C. or higher and 1,000 degrees C. or lower”. The same applies to other numerical ranges. 
     A natural oxide film or the like may be formed on the surface of the wafer  200  prior to performing a film-forming process. By supplying the NH 3  gas to the wafer  200  under the aforementioned conditions, NH termination can be formed on the surface of the wafer  200  on which the natural oxide film or the like is formed. Thus, a desired film-forming reaction can go ahead on the wafer  200  at step B as described hereinbelow. A partial enlarged view of the surface of the wafer  200  on which the NH termination is formed is illustrated in  FIG.  5 A . The NH termination formed on the surface of the wafer  200  may be regarded as synonymous with an H termination. Furthermore, since the supply of the NH 3  gas to the wafer  200  and the process of forming the NH termination on the surface of the wafer  200  at this step are performed prior to a substantial film-forming process (steps B and C), they will be referred to as pre-flow and pre-processing, respectively. 
     In the case where the NH 3  gas is supplied to the wafer  200  from the side of the wafer  200  as in the present embodiment, there is a tendency that the formation of the NH termination starts earlier in an outer peripheral portion of the wafer  200 , and starts in the central portion of the wafer  200  with delay. This phenomenon becomes particularly conspicuous when a pattern including a recess such as a trench or a hole is formed on the surface of the wafer  200 . At this step, if the supply time of the NH 3  gas is less than 1 minute, although the NH termination may be formed in the outer peripheral portion of the wafer  200 , the NH termination may be difficult to be formed in the center portion of the wafer  200 . By setting the supply time of the NH 3  gas at a time of 1 minute or more, it is possible to form the NH termination from the outer peripheral portion to the central portion of the wafer  200  uniformly, i.e., substantially uniformly in amount and density. However, if the supply time of the NH 3  gas exceeds 30 minutes, the supply of the NH 3  gas to the wafer  200  may be continued in a state in which the formation reaction of the NH termination on the surface of the wafer  200  is saturated. As a result, usage amount of the NH 3  gas which does not contribute to the formation of the NH termination unnecessarily increases, which may increase a gas cost. By setting the supply time of the NH 3  gas at a time of 30 minutes or less, it is possible to suppress an increase in the gas cost. 
     After the NH termination is formed on the surface of the wafer  200  by pre-flowing the NH 3  gas to the wafer  200 , the valve  243   b  is closed to stop the supply of the NH 3  gas into the process chamber  201 . Then, the interior of the process chamber  201  is vacuum-exhausted and the gas or the like remaining within the process chamber  201  is removed from the interior of the process chamber  201 . At this time, the valves  243   c  and  243   d  are opened to supply an N 2  gas as a purge gas into the process chamber  201  (purge step). The processing pressure at the purge step may be set at a pressure of, for example, 1 to 100 Pa, and the supply flow rate of the N 2  gas may be set at a flow rate of, for example, 10 to 10,000 sccm. 
     As the first reaction gas, it may be possible to use, in addition to the NH 3  gas, a hydrogen nitride-based gas such as a diazene (N 2 H 2 ) gas, a hydrazine (N 2 H 4 ) gas, and an N 3 H 8  gas. 
     As the inert gas, it may be possible to use, in addition to the N 2  gas, a rare gas such as an Ar gas, an He gas, an Ne gas, and an Xe gas. This also applies to steps B and C as described hereinbelow. 
     [Step B] 
     At this step, a SiCl 4  gas is supplied to the wafer  200  in the process chamber  201 , namely the NH termination formed on the surface of the wafer  200 . Specifically, the opening/closing control of the valves  243   a ,  243   c  and  243   d  is performed in the same procedure as the opening/closing control of the valves  243   b  to  243   d  at step A. The flow rate of the SiCl 4  gas is controlled by the MFC  241   a . The SiCl 4  gas is supplied into the process chamber  201  via the nozzle  249   a  and is exhausted from the exhaust pipe  231 . At this time, the SiCl 4  gas is supplied to the wafer  200  from the side of the wafer  200 . 
     The processing conditions at this step may be exemplified as follows: 
     SiCl 4  gas supply flow rate: 10 to 2,000 sccm, or 100 to 1,000 sccm in some embodiments 
     Supply time of SiCl 4  gas: 60 to 180 seconds, or 60 to 120 seconds in some embodiments 
     Processing temperature: 300 to 1,000 degrees C., 700 to 900 degrees C. in some embodiments, or 750 to 800 degrees C. in some embodiments 
     Processing pressure: 1 to 2,000 Pa, or 20 to 1,333 Pa in some embodiments. 
     Other processing conditions may be similar to the processing conditions of step A. 
     By supplying the SiCl 4  gas to the wafer  200  under the aforementioned conditions, it is possible to react the NH termination formed on the surface of the wafer  200  with SiCl 4 . Specifically, at least a portion of Si—Cl bonds in SiCl 4  and at least a portion of N—H bonds in the NH termination formed on the surface of the wafer  200  can be broken. Furthermore, Si after the at least a portion of Si—Cl bonds in SiCl 4  are broken can be bonded to N after the at least a portion of N—H bonds in the NH termination formed on the surface of the wafer  200  are broken to form Si—N bonds. Cl separated from Si and H separated from N respectively constitute gaseous substances such as HCl or the like so as to be desorbed from the wafer  200  and are exhausted from the exhaust pipe  231 . 
     In addition, at this step, the Si—Cl bonds, which are not converted into the Si—N bonds among the Si—Cl bonds in SiCl 4  during the aforementioned reaction, can be held without being broken. That is, at this step, Si after the at least a portion of Si—Cl bonds in SiCl 4  are broken can be bonded to N after the at least a portion of N—H bonds in the NH termination formed on the surface of the wafer  200  are broken in a state where Cl is bonded to each of three bonding hands of four bonding hands of Si constituting SiCl 4 . 
     In the present disclosure, the aforementioned reaction proceeding on the surface of the wafer  200  at step B will be referred to as an adsorptive substitution reaction. At this step, the adsorptive substitution reaction described above can go ahead to form a layer which contains Si and N and whose entire surface is terminated with SiCl, i.e., a silicon nitride layer (first SiN layer) having SiCl termination formed on its surface, on the wafer  200 . A partial enlarged view of the surface of the wafer  200  on which the first SiN layer having SiCl termination formed on its surface is formed is illustrated in  FIG.  5 B . Furthermore, in  FIG.  5 B , illustration of part of Cl is omitted for the sake of convenience. The first SiN layer having SiCl termination formed on its surface becomes a layer in which further Si deposition on the wafer  200  does not go ahead even if the supply of the SiCl 4  gas to the wafer  200  is further continued after the formation of this layer, due to Cl constituting the SiCl termination acting as steric hindrance. That is, the first SiN layer having SiCl termination formed on its surface becomes a layer to which self-limitation is applied for further Si adsorption reaction. Accordingly, the thickness of the first SiN layer becomes a uniform thickness of less than one atomic layer (less than one molecular layer) over the entire region in the plane of the wafer. Furthermore, the SiCl termination formed on the surface of the wafer  200  may be regarded as synonymous with a Cl termination. 
     The processing conditions at this step are conditions under which SiCl 4  supplied into the process chamber  201  is not gas-phase decomposed (pyrolyzed). That is, the aforementioned processing conditions are conditions under which SiCl 4  supplied into the process chamber  201  does not generate an intermediate in the gas phase and the Si deposition on the wafer  200  by the gas-phase reaction does not go ahead. In other words, the processing conditions described above are conditions under which only the adsorptive substitution reaction described above can occur on the wafer  200 . By setting the processing conditions at this step to such conditions, it is possible to allow the first SiN layer formed on the wafer  200  to become a layer having excellent thickness uniformity in the plane of the wafer (hereinafter, also simply referred to as in-plane thickness uniformity). 
     If the film-forming temperature (processing temperature) is lower than 300 degrees C., there may be a case where it is difficult for the first SiN layer to be formed on the wafer  200  and for the formation of the SiN film on the wafer  200  to go ahead at a practical deposition rate. Furthermore, a large amount of impurity such as Cl or the like may remain in the SiN film formed on the wafer  200 , lowering a processing resistance of the SiN film. By setting the film-forming temperature at a temperature of 300 degree C. or higher, the formation of the SiN film on the wafer  200  can go ahead at a practical deposition rate. In addition, it is possible to allow the SiN film formed on the wafer  200  to become a film having low impurity concentration and excellent processing resistance. By setting the film-forming temperature at a temperature of 700 degrees C. or higher, it is possible to reliably achieve the aforementioned effects. By setting the film-forming temperature at a temperature of 750 degrees C. or higher, it is possible to more reliably achieve the aforementioned effects. 
     If film-forming temperature exceeds 1,000 degrees C., there may be a case where a reaction other than the aforementioned adsorptive substitution reaction goes ahead in the process chamber  201 . For example, the Si—Cl bonds which are not converted into the Si—N bonds among the Si—Cl bonds in SiCl 4  may be broken, making it difficult to be SiCl-terminated on the entire surface of the first SiN layer. That is, it may be difficult for the first SiN layer to become a layer to which self-limitation is applied for further Si adsorption reaction. In addition, SiCl 4  supplied into the process chamber  201  is gas-phase decomposed (pyrolyzed) to generate an intermediate, and the Si deposition on the wafer  200  by the gas-phase reaction may go ahead. As a result, the in-plane thickness uniformity of the first SiN layer formed on the wafer  200 , i.e., the film thickness uniformity of the SiN film in the plane of the substrate (hereinafter, simply referred to as in-plane film thickness uniformity), may be deteriorated. By setting the film-forming temperature at a temperature of 1,000 degrees C. or lower, it is possible to solve the problems described above. By setting the film-forming temperature at a temperature of 900 degrees C. or lower, it is possible to reliably solve the problems described above. By setting the film-forming temperature at a temperature of 800 degrees C. or lower, it is possible to more reliably solve the problems described above. 
     From these facts, it is desirable that the film-forming temperature be set at 300 to 1,000 degrees C., 700 to 900 degrees C. in some embodiments, or 750 to 800 degrees C. in some embodiments. Furthermore, among the temperature conditions illustrated above, the relatively high temperature condition such as, e.g., 700 to 900 degrees C., is a temperature condition under which a chlorosilane-based gas such as a dichlorosilane (SiH 2 Cl 2 , abbreviation: DCS) gas, a hexachlorodisilane (Si 2 Cl 6 , abbreviation: HCDS) gas or the like is gas-phase decomposed. On the other hand, the SiCl 4  gas is not gas-phase decomposed even under a high temperature condition in which the DCS gas or the HCDS gas is gas-phase decomposed. Therefore, when performing the film-forming process at this relatively high temperature zone, it can be said that the SiCl 4  gas is a precursor capable of enhancing the thickness controllability of the SiN film formed on the wafer  200 . 
     In the case where the SiCl 4  gas is supplied to the wafer  200  from the side of the wafer  200  as in the present embodiment, there is a tendency that the formation of the first SiN layer starts earlier in the outer peripheral portion of the wafer  200 , and starts in the central portion of the wafer  200  with delay. This phenomenon becomes particularly conspicuous when the aforementioned pattern is formed on the surface of the wafer  200 . At this step, if the supply time of the SiCl 4  gas is less than 60 seconds, although the first SiN layer may be formed in the outer peripheral portion of the wafer  200 , the first SiN layer may be difficult to be formed in the central portion of the wafer  200 . By setting the supply time of the SiCl 4  gas at a time of 60 seconds or more, it is possible to form the first SiN layer substantially uniformly, i.e., substantially uniformly in thickness and composition, from the outer peripheral portion to the central portion of the wafer  200 . However, if the supply time of the SiCl 4  gas exceeds 180 seconds, the supply of the SiCl 4  gas to the wafer  200  may be continued in a state in which the formation reaction of the first SiN layer on the surface of the wafer  200  is saturated. As a result, the usage amount of the SiCl 4  gas which does not contribute to the formation of the first SiN layer unnecessarily increases, which may increase the gas cost. By setting the supply time of the SiCl 4  gas at a time of 180 seconds or less, it is possible to suppress an increase in gas cost. By setting the supply time of the SiCl 4  gas at a time of 120 seconds or less, it is possible to reliably suppress an increase in gas cost. 
     After the first SiN layer is formed on the wafer  200 , the valve  243   a  is closed to stop the supply of the SiCl 4  gas into the process chamber  201 . Then, the gas or the like remaining within the process chamber  201  is removed from the interior of the process chamber  201  under the same processing procedures and processing conditions as those of the purge step of step A described above. 
     [Step C] 
     At this step, an NH 3  gas is supplied to the wafer  200  in the process chamber  201 , i.e., the first SiN layer formed on the wafer  200 . Specifically, the opening/closing control of the valves  243   b  to  243   d  is performed in the same procedure as the opening/closing control of the valves  243   b  to  243   d  at step A. The flow rate of the NH 3  gas is controlled by the MFC  241   b . The NH 3  gas is supplied into the process chamber  201  via the nozzle  249   b  and is exhausted from the exhaust pipe  231 . At this time, the NH 3  gas is supplied to the wafer  200  from the side of the wafer  200 . 
     The processing conditions at this step may be exemplified as follows: 
     Supply time of NH 3  gas: 1 to 60 seconds, or 1 to 50 seconds in some embodiments. 
     Other processing conditions may be similar to the processing conditions of step A. 
     By supplying the NH 3  gas to the wafer  200  under the aforementioned conditions, it is possible to react the SiCl termination formed on the surface of the first SiN layer with NH 3 . Specifically, at least a portion of N—H bonds in NH 3  and at least a portion of Si—Cl bonds in the SiCl termination formed on the surface of the first SiN layer can be broken. Then, N after the at least a portion of N—H bonds in NH 3  are broken can be bonded to Si after the at least a portion of Si—Cl bonds in the SiCl termination formed on the surface of the first SiN layer are broken to form Si—N bonds. H separated from N and Cl separated from Si respectively constitute gaseous substances such as HCl or the like so as to be desorbed from the wafer  200  and are exhausted from the exhaust pipe  231 . 
     At this step, the N—H bonds, which are not converted into the Si—N bonds among the N—H bonds in NH 3  during the aforementioned reaction, can be held without being broken. That is, at this step, N after the at least a portion of N—H bonds in NH 3  are broken can be bonded to Si after the at least a portion of Si—Cl bonds in the SiCl termination formed on the surface of the first SiN layer are broken in a state in which H is bonded to each of two bonding hands among three bonding hands of N constituting NH 3 . 
     In the present disclosure, the aforementioned reaction proceeding on the surface of the wafer  200  at step C will be referred to as an adsorptive substitution reaction. At this step, the adsorptive substitution reaction described above can go ahead to form a layer which contains Si and N and whose entire surface is terminated with NH, i.e., a silicon nitride layer (second SiN layer) having NH termination formed on its surface, on the wafer  200 . A partial enlarged view of the surface of the wafer  200  on which the second SiN layer having NH termination formed on its surface is formed is illustrated in  FIG.  5 C . Furthermore, the NH termination formed on the surface of the second SiN layer may be regarded as synonymous with the H termination. 
     The processing conditions at this step are conditions under which only the adsorptive substitution reaction described above occurs on the wafer  200 . At this step, N after the at least a portion of N—H bonds in NH 3  are broken can be bonded to Si after the at least a portion of Si—Cl bonds in the SiCl termination formed on the surface of the wafer  200  are broken in a state where H is bonded to each of two bonding hands among three bonding hands of N constituting NH 3 . 
     In the case where the NH 3  gas is supplied to the wafer  200  from the side of the wafer  200  as in the present embodiment, there is a tendency that the formation of the second SiN layer starts earlier in the outer peripheral portion of the wafer  200 , and starts in the central portion of the wafer  200  with delay. This phenomenon becomes particularly conspicuous when the aforementioned pattern is formed on the surface of the wafer  200 . At this step, if the supply time of the NH 3  gas is less than 1 second, although the second SiN layer may be formed in the outer peripheral portion of the wafer  200 , the second SiN layer may be difficult to be formed in the central portion of the wafer  200 . By setting the supply time of the NH 3  gas at a time of 1 second or more, it is possible to form the second SiN layer substantially uniformly, i.e., substantially uniformly in thickness and composition, from the outer peripheral portion to the central portion of the wafer  200 . However, when the supply time of the NH 3  gas exceeds 60 seconds, the supply of the NH 3  gas to the wafer  200  may be continued in a state in which the formation reaction of the second SiN layer on the surface of the wafer  200  is saturated. As a result, the usage amount of the NH 3  gas which does not contribute to the formation of the second SiN layer unnecessarily increases, which may increase the gas cost. By setting the supply time of the NH 3  gas at a time of 60 seconds or less, it is possible to suppress an increase in gas cost. By setting the supply time of the NH 3  gas at a time of 50 seconds or less, it is possible to reliably suppress an increase in gas cost. 
     After the second SiN layer is formed on the wafer  200 , the valve  243   b  is closed to stop the supply of the NH 3  gas into the process chamber  201 . Then, the gas or the like remaining within the process chamber  201  is removed from the interior of the process chamber  201  under the same processing procedures and processing conditions of the purge step of step A described above. 
     As the second reaction gas, it may be possible to use, in addition to the NH 3  gas, various kinds of hydrogen nitride-based gases exemplified at step A described above. Furthermore, it may be possible to use different gases as the first reaction gas and the second reaction gas. For example, it may be possible to use the NH 3  gas as the first reaction gas and the N 2 H 2  gas as the second reaction gas. 
     [Performing a Predetermined Number of Times] 
     After step A is performed, a cycle which non-simultaneously, i.e., non-synchronously, performs steps B and C is implemented a predetermined number of times (n times, where n is an integer of 1 or more), whereby a SiN film having a predetermined thickness can be formed on the wafer  200 . The surface of the second SiN layer formed by performing step C becomes a surface terminated with NH, like the surface of the wafer  200  after performing step A. That is, the surface of the wafer  200  after performing step C becomes a surface on which the first SiN layer is easy to be formed when performing step B thereafter. Therefore, the cycle which non-simultaneously performs steps B and C after performing step A can be implemented a predetermined number of times to alternately perform the formation of the first SiN layer on the wafer  200  and the formation of the second SiN film on the wafer  200 . As a result, the formation of the SiN film on the wafer  200  can go ahead with enhanced controllability. Furthermore, the aforementioned cycle may be repeated multiple times. That is, the thickness of the second SiN layer formed when the cycle which non-simultaneously performs steps B and C is implemented once may be set smaller than a desired thickness, and the aforementioned cycle may be repeated multiple times until the thickness of the SiN film formed by laminating the second SiN layer becomes equal to the desired thickness. 
     Furthermore, in order to allow the SiN film formed on the wafer  200  to become a film having excellent in-plane film thickness uniformity, it is desirable that the supply time of the SiCl 4  gas at step B may be set such that the thickness of the first SiN layer formed in the central portion of the wafer  200  becomes substantially equal to the thickness of the first SiN layer formed in the outer peripheral portion of the wafer  200  in some embodiments. In other words, the supply time of the SiCl 4  gas at step B may be set for a time so that the amount of the adsorptive substitution reaction occurring between the NH termination formed on the surface of the wafer  200  and the SiCl 4  gas in the central portion of the wafer  200  becomes substantially equal to the amount of the adsorptive substitution reaction occurring between the NH termination formed on the surface of the wafer  200  and the SiCl 4  gas in the outer peripheral portion of the wafer  200  in some embodiments. For example, by setting the supply time of the SiCl 4  gas at step B longer than the supply time of the NH 3  gas at step C, it is possible to reliably achieve the operational effects described above. 
     Furthermore, in order to allow the SiN film formed on the wafer  200  to become a film having excellent in-plane film thickness uniformity, the supply time of the NH 3  gas at step A may be set for a time so that the amount or density of the NH termination formed in the central portion of the wafer  200  becomes substantially equal to the amount or density of the NH termination formed in the outer peripheral portion of the wafer  200  in some embodiments. For example, by setting the supply time of the NH 3  gas at step A longer than the supply time of the NH 3  gas at step C, it is possible to reliably achieve the operational effects described above. In addition, for example, by setting the supply time of the NH 3  gas at step A longer than the supply time of the SiCl 4  gas at step B, it is possible to more reliably achieve the operational effects described above. 
     From this fact, the supply time of the NH 3  gas at step A may be set longer than the supply time of the SiCl 4  gas at step B, and the supply time of the SiCl 4  gas at step B may be set longer than the supply time of the NH 3  gas at step C in some embodiments. By setting the supply time s of the various kinds of gases at steps A, B, and C to have such a balance, it is possible to allow the SiN film formed on the wafer  200  to become a film having very excellent in-plane film thickness uniformity. 
     (After-Purge and Atmospheric Pressure Return) 
     After the aforementioned film-forming process is completed, the N 2  gas is supplied from the respective gas supply pipes  232   c  and  232   d  into the process chamber  201  and is exhausted from the exhaust pipe  231 . Thus, the interior of the process chamber  201  is purged and the gas or the reaction byproduct, which remains within the process chamber  201 , is removed from the interior of the process chamber  201  (after-purge). Thereafter, the internal atmosphere of the process chamber  201  is substituted by an inert gas (inert gas substitution). The internal pressure of the process chamber  201  is returned to an atmospheric pressure (atmospheric pressure return). 
     (Boat Unloading and Wafer Discharging) 
     Thereafter, the seal cap  219  is moved down by the boat elevator  115  to open the lower end of the reaction tube  203 . Then, the processed wafers  200  supported on the boat  217  are unloaded from the lower end of the reaction tube  203  to the outside of the reaction tube  203  (boat unloading). The processed wafers  200  are discharged from the boat  217  (wafer discharging). 
     (3) Effects According to the Present Embodiment 
     According to the present embodiment, one or more effects as set forth below may be achieved. 
     (a) By performing a cycle a predetermined number of times under the condition where SiCl 4  is not gas-phase decomposed after performing step A, the cycle including non-simultaneously performing step B and step C, it is possible to allow the SiN film formed on the wafer  200  to become a film having excellent in-plane film thickness uniformity. 
     This is because, by performing step B under the aforementioned conditions, i.e., under the conditions in which only the adsorptive substitution reaction occurs between the NH termination formed on the surface of the wafer  200  and SiCl 4 , it is possible to allow the first SiN layer formed on the wafer  200  to become a layer whose entire surface is terminated with SiCl. That is, it is possible to allow the first SiN layer to become a layer to which self-limitation is applied for further Si adsorption reaction, i.e., for further adsorptive substitution reaction. As a result, it is possible to allow the first SiN layer formed on the wafer  200  to become a layer having excellent in-plane thickness uniformity. This also makes it possible to allow the second SiN layer formed by modifying the first SiN layer to become a layer having excellent in-plane thickness uniformity at subsequent step C. 
     Furthermore, by performing step C under the aforementioned conditions, i.e., under the conditions in which only the adsorptive substitution reaction occurs between the SiCl termination formed on the surface of the first SiN layer and NH 3 , it is possible to allow the second SiN layer formed on the wafer  200  to become a layer whose entire surface is terminated with NH. This makes it possible for the adsorptive substitution reaction between the NH termination formed on the surface of the second SiN layer and SiCl 4  to go ahead uniformly over the entire surface of the wafer  200  at step B performed in the subsequent cycle. As a result, it is possible to allow the first SiN layer formed on the second SiN layer to become a layer having excellent in-plane thickness uniformity. This makes it possible to allow the second SiN layer formed by modifying the first SiN layer to become a layer having excellent in-plane thickness uniformity at subsequent step C. 
     As described above, according to the present embodiment, only the NH termination formed on the wafer  200  and the SiCl termination formed on the wafer  200  can be allowed to utilize a film-forming mechanism which contributes to the formation of the SiN film on the wafer  200 . As a result, it is possible to allow the SiN film formed on the wafer  200  to become a film having excellent in-plane film thickness uniformity. 
     (b) By setting the supply time of the SiCl 4  gas at step B longer than the supply time of the NH 3  gas at step C, it is possible to allow the first SiN layer having SiCl termination formed on its surface formed on the wafer  200  to become a layer having excellent in-plane thickness uniformity. As a result, it is possible to allow the SiN film formed on the wafer  200  to become a film having excellent in-plane film thickness uniformity. 
     (c) By setting the supply time of the NH 3  gas at step A longer than the supply time of the NH 3  gas at step C, it is possible to uniformly form the NH termination from the outer peripheral portion to the central portion of the wafer  200 . This makes it possible to allow the first SiN layer formed on the wafer  200  to become a layer having excellent in-plane thickness uniformity at step B performed in the subsequent cycle. As a result, it is possible to allow the SiN film formed on the wafer  200  to become a film having excellent in-plane film thickness uniformity. 
     In addition, by setting the supply time of the NH 3  gas at step A longer than the supply time of the SiCl 4  gas at step B, it is possible to more reliably achieve the aforementioned effects. 
     (d) Since the SiCl 4  gas is used as the precursor, although step B is performed under a relatively high temperature condition (temperature condition of 700 degrees C. or higher) in which the DCS gas or HCDS gas is gas-phase decomposed, it is possible to allow the thickness of the first SiN layer to become a uniform thickness of less than one atomic layer (less than one molecular layer) over the entire region in the plane of the wafer. Therefore, it is possible to precisely and stably control the thickness of the SiN film. That is, it is possible to allow the formation of the SiN film on the wafer  200  to go ahead with enhanced controllability. 
     Furthermore, when the DCS gas or HCDS gas is used as the precursor, for example, under a relatively high temperature condition of 700 degrees C. or higher, the precursor is vapor-phase decomposed and the Si-containing layer formed on the wafer  200  by supplying the precursor becomes a layer to which self-limitation is not applied for further Si adsorption reaction. Therefore, it is difficult to allow the thickness of the Si-containing layer formed by supplying these precursors to become a uniform thickness of less than one atomic layer (less than one molecular layer) over the entire region in the plane of the wafer under a relatively high temperature condition. As a result, it is difficult to precisely and stably control the thickness of the finally obtained SiN film. 
     (e) The effects mentioned above can be similarly achieved in the case where the aforementioned hydrogen nitride-based gas other than the NH 3  gas is used or in the case where the aforementioned inert gas other than the N 2  gas is used, as the first and second reactants. In addition, the effects mentioned above can be similarly achieved in the case where different hydrogen nitride-based gases are used as the first and second reactants. 
     Other Embodiments 
     While one embodiment of the present disclosure has been specifically described above, the present disclosure is not limited to the aforementioned embodiment but may be variously modified without departing from the spirit of the present disclosure. 
     At least one of step A and step C, the NH 3  gas activated by plasma may be supplied to the wafer  200 . Even in this case, the same effects as those of the film-forming sequence illustrated in  FIG.  4    may be achieved. 
     Recipes used in substrate processing may be prepared individually according to the processing contents and may be stored in the memory device  121   c  via a telecommunication line or an external memory device  123 . Moreover, at the start of substrate processing, the CPU  121   a  may properly select an appropriate recipe from the recipes stored in the memory device  121   c  according to the processing contents. Thus, it is possible for a single substrate processing apparatus to form films of different kinds, composition ratios, qualities and thicknesses with enhanced reproducibility. In addition, it is possible to reduce an operator&#39;s burden and to quickly start the substrate processing while avoiding an operation error. 
     The recipes mentioned above are not limited to newly-prepared ones but may be prepared by, for example, modifying the existing recipes already installed in the substrate processing apparatus. When modifying the recipes, the modified recipes may be installed in the substrate processing apparatus via a telecommunication line or a recording medium storing the recipes. In addition, the existing recipes already installed in the substrate processing apparatus may be directly modified by operating the input/output device  122  of the existing substrate processing apparatus. 
     In the aforementioned embodiment, there has been described an example in which films are formed using a batch-type substrate processing apparatus capable of processing a plurality of substrates at a time. The present disclosure is not limited to the aforementioned embodiment but may be appropriately applied to, e.g., a case where films are formed using a single-wafer-type substrate processing apparatus capable of processing a single substrate or several substrates at a time. In addition, in the aforementioned embodiments, there have been described examples in which films are formed using the substrate processing apparatus provided with a hot-wall-type process furnace. The present disclosure is not limited to the aforementioned embodiments but may be appropriately applied to a case where films are formed using a substrate processing apparatus provided with a cold-wall-type process furnace. 
     In the case of using these substrate processing apparatuses, a film-forming process may be performed by the processing procedures and processing conditions similar to those of the embodiments and modifications described above. Effects similar to those of the embodiments and modifications described above may be achieved. 
     The embodiments, modifications and the like described above may be appropriately combined with one another. The processing procedures and processing conditions at this time may be similar to, for example, the processing procedures and processing conditions of the aforementioned embodiment. 
     EXAMPLES 
     First Example 
     In example 1, a film-forming process of forming a SiN film on a wafer was performed a plurality of times using the substrate processing apparatus illustrated in  FIG.  1    and by the film-forming sequence illustrated in  FIG.  4   . The film-forming temperature was set at 650 degrees C., 700 degrees C., 750 degrees C., and 800 degrees C. Other processing conditions were set to predetermined conditions which fall within the processing condition range of the aforementioned embodiments. 
     In comparative example 1, after performing step A of the film-forming sequence illustrated in  FIG.  4    to form NH termination on the wafer using the substrate processing apparatus illustrated in  FIG.  1   , a cycle is performed a predetermined number of times, the cycle including non-simultaneously performing a step B′ of supplying a DCS gas to a wafer and a step C′ of supplying an NH 3  gas to the wafer, whereby a film-forming process of forming a SiN film on the wafer was performed multiple times. The film-forming temperature was set at 550 degrees C., 600 degrees C., 650 degrees C., and 700 degrees C. The processing conditions at steps A, B ‘and C’ were set similar to the processing conditions of steps A to C of the example, respectively. 
     Then, the in-plane film thickness uniformities of the SiN film formed in example 1 and comparative example 1 were each measured. The measurement results are shown in  FIG.  6 A . 
     The vertical axis in  FIG.  6 A  indicates an in-plane film thickness uniformity (%) of the SiN film. When the value of the in-plane film thickness uniformity (%) is 0, it means that the film thickness of the SiN film is uniform from the central portion to the outer peripheral portion of the wafer. When the value of the in-plane film thickness uniformity (%) is larger than 0, it means that the thickness of the SiN film has a distribution which is the largest in the central portion of the wafer surface and is gradually decreased toward the outer peripheral portion thereof, i.e., a central convex distribution. When the value of the in-plane film thickness uniformity (%) is smaller than 0, it means that the thickness of the SiN film has a distribution which is the largest in the outer peripheral portion of the wafer surface and is gradually decreased toward the central portion thereof, i.e., a central concave distribution. In addition, the value of the in-plane film thickness uniformity (%) indicates that the in-plane film thickness uniformity of the SiN film formed on the wafer is better as it approaches zero. The horizontal axis in  FIG.  6 A  indicates a film-forming temperature (degrees C.) when forming the SiN film. In  FIG.  6 A , the symbol ● indicates example 1 and the symbol X indicates comparative example 1. 
     According to  FIG.  6 A , it can be seen that the in-plane film thickness uniformity of the SiN film in example 1 is consistently excellent regardless of the film-forming temperature. In contrast, it can be seen that the in-plane film thickness uniformity of the SiN film in comparative example 1 varies greatly from the central convex distribution to the central concave distribution as the film-forming temperature increases. It is also understood that the in-plane film thickness uniformity of the SiN film in the comparative example shows a strong central concave distribution when the film-forming temperature exceeds 650 degrees C. That is, under a temperature condition of a high temperature exceeding at least 650 degrees C., it is understood that it is possible to more improve the in-plane film thickness uniformity of the SiN film by using the SiCl 4  gas as the precursor instead of using the DCS gas as the precursor. 
     In addition, a wet etching rate (hereinafter, referred to as a WER) of the SiN film formed in each of example 1 and comparative example 1 was measured, and each processing resistance was evaluated. The measurement results are shown in  FIG.  6 B . 
     The vertical axis in  FIG.  6 B  indicates a WER (Å/min) of the SiN film with respect to hydrofluoric acid have a concentration of 1% (1% HF aqueous solution). The horizontal axis in  FIG.  6 B  indicates comparative example 1 and example 1 in order. Comparative example 1 is a SiN film formed at a film-forming temperature of 650 degrees C., and example 1 is a SiN film formed at a film-forming temperature of 800 degrees C. 
     According to  FIG.  6 B , it can be seen that a WER (6.2 Å/min) of the SiN film of example 1 is smaller than a WER (9.7 Å/min) of the SiN film of comparative example 1. That is, it can be seen that the SiN film formed using the SiCl 4  gas as the precursor under a relatively high temperature condition has better processing resistance (wet etching resistance) than the SiN film formed using the DCS gas as the precursor under a relatively low temperature condition. 
     Example 2 
     In example 2, a SiN film was formed on a wafer using the substrate processing apparatus illustrated in  FIG.  1    and by the film-forming sequence illustrated in  FIG.  4   . A bare wafer on which no pattern was formed and a pattern wafer on which a pattern is formed and which has a surface area 50 times the surface area of the bare wafer were used as the wafer. The processing condition at each step were set to predetermined conditions which fall within the processing condition range of the aforementioned embodiments. 
     In comparative example 2, after performing step A of the film-forming sequence illustrated in  FIG.  4    to form NH termination on the wafer using the substrate processing apparatus illustrated in  FIG.  1   , a cycle is performed a predetermined number of times, the cycle including non-simultaneously performs a step B′ of supplying a DCS gas to the wafer and a step C′ of supplying an NH 3  gas to the wafer at, whereby a SiN film was formed on the wafer. The bare wafer and the pattern wafer described above were each used as the wafer. The processing conditions at steps A, B′ and C′ were set similar to the processing conditions at steps A to C of the example, respectively. 
     Then, the in-plane film thickness uniformities of the SiN film formed in example 2 and comparative example 2 were each measured. The measurement results are shown in  FIG.  7   . The vertical axis in  FIG.  7    indicates an in-plane film thickness uniformity (%) of the SiN film, and meaning of its value is similar to the vertical axis in  FIG.  6 A . The horizontal axis in  FIG.  7    indicates a case where the bare wafer is used as the wafer and a case where the pattern wafer is used as the wafer. In  FIG.  7   , a white columnar graph shows comparative example 2 and a shaded columnar graph shows example 2. 
     According to  FIG.  7   , it can be seen that the in-plane film thickness uniformity of the SiN film in example 2 is excellent both in the case where the bare wafer is used as the wafer and in the case where the pattern wafer is used as the wafer. In contrast, it can be seen that the in-plane film thickness uniformity of the SiN film in comparative example 2 shows a strong central convex distribution when the bare wafer is used as the wafer and a strong central concave distribution when the pattern wafer is used as the wafer. That is, it can be seen that the influence of the SiN film in example 2 on the in-plane film thickness uniformity due to the surface area of the wafer can be suppressed to be smaller than that on the SiN film in comparative example 2. In other words, it can be seen that the film-forming method in example 2 can suppress a so-called loading effect (substrate surface area dependency) to be smaller than that of the film-forming method in comparative example 2. 
     According to the present disclosure in some embodiments, it is possible to improve film thickness uniformity of a SiN film formed on the substrate in the plane of the substrate. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the disclosures. Indeed, the embodiments described herein may be embodied in a variety of other forms. Furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the disclosures. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the disclosures.