Patent Publication Number: US-2023151480-A1

Title: Film deposition method and method for forming polycrystalline silicon film

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application claims priority to Japanese Patent Application No. 2021-184977, filed Nov. 12, 2021, the contents of which are incorporated herein by reference in their entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to a film deposition method and a method for forming a polycrystalline silicon film. 
     BACKGROUND 
     A technique is known in which an amorphous silicon film, which is doped with impurities that suppress the progress of crystallization, as well as a non-doped amorphous silicon film, are laminated in this order so as to be situated on and above an insulating film, and then the laminated amorphous silicon films are crystallized (see, for example, Patent Document 1). 
     RELATED-ART DOCUMENT 
     Patent Document 
     
         
         [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2015-115435 
       
    
     SUMMARY 
     One aspect of the present disclosure relates to a film deposition method. The film deposition method includes depositing an amorphous silicon film in a substrate under a process condition. The process condition includes supplying SiH 4  gas into a processing chamber in which the substrate is placed. The process condition includes setting a temperature in the processing chamber to be in a range of greater than or equal to 300° C. and less than or equal to 440° C. The process condition includes setting a pressure of the processing chamber to be in a range of greater than or equal to 10 Torr and less than or equal to 100 Torr. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a flowchart illustrating a method for forming a polycrystalline silicon film according to one embodiment; 
         FIG.  2    is a schematic cross-sectional view of a substrate after a second deposition step; 
         FIG.  3    is a schematic diagram of an example of a processing apparatus that performs the method for forming a polycrystalline silicon film; 
         FIG.  4 A  is a graph indicating the relationship between a temperature in a processing chamber and a hydrogen concentration in a film in a deposition process; 
         FIG.  4 B  is a graph indicating the relationship between a pressure of the processing chamber and the hydrogen concentration in the film in the deposition process; 
         FIG.  5 A  is a cross-sectional view of an example of a seed layer and a bulk layer in a recess formed in the deposition process according to one embodiment; 
         FIG.  5 B  is a cross-sectional view of the seed layer and the bulk layer in the recess formed in a conventional deposition process; and 
         FIG.  5 C  is a graph indicating a comparison of film thicknesses of the seed layer formed in the recess. 
     
    
    
     DETAILED DESCRIPTION 
     One or more embodiments of the present disclosure will be described below with reference to the drawings. In each of the drawings, the same components are denoted by the same numerals, and accordingly, duplicate description will be omitted. 
     As illustrated in  FIG.  1   , a method for forming a polycrystalline silicon film according to one embodiment disclosure includes sequentially performing a first deposition step S 1 , a second deposition step S 2 , and a crystallization step S 3 . A film deposition method according to one embodiment relates to a deposition process in the first deposition step S 1 . 
     As illustrated in  FIG.  2   , a substrate  100  for which the method for forming a polycrystalline silicon film is performed is, for example, a semiconductor wafer applied to a memory such as a VNAND. The substrate  100  may be used for a purpose other than the memory. 
     The substrate  100  includes an insulating film (base layer)  110  on a surface of the substrate  100 . The insulating film  110  insulates a gate in a memory. Examples of the insulating film  110  include a silicon oxide film (SiO 2  film), a silicon nitride film (SiN film), and the like. In the method for forming a polycrystalline silicon film, an amorphous silicon film is deposited on the insulating film  110 . When the amorphous silicon film is formed, the surface of the insulating film  110  is preferably coated with organic silane such as aminosilane. 
     In the second deposition step S 2 , the first amorphous silicon film (seed layer  121 ) and the second amorphous silicon film (bulk layer  122 ) are laminated on and above the insulating film  110 . That is, in the method for forming a polycrystalline silicon film, the seed layer  121  is deposited on the insulating film  110  in the first deposition step S 1 , and the bulk layer  122  is deposited on the seed layer  121  in the second deposition step S 2 . 
     In the crystallization step S 3 , the seed layer  121  and the bulk layer  122  are crystallized by heating the substrate  100  that includes the seed layer  121  and the bulk layer  122  to a predetermined temperature. With this approach, in the substrate  100 , a polycrystalline silicon film is formed on the insulating film  110 . 
     Hereafter, an example of a processing apparatus  1  that performs the method for forming a polycrystalline silicon film will be described with reference to  FIG.  3   . The processing apparatus  1  is a batch-type apparatus that performs a process in which substrates  100  each of which includes the insulating film  110  are processed at the same time. 
     The processing apparatus  1  includes a processing chamber  10 , a gas supply  30 , an exhaust device  40 , a heater  50 , a controller  80 , and the like. 
     An interior of the processing chamber  10  can be depressurized, and the processing chamber  10  accommodates substrates  100 . The processing chamber  10  includes a cylindrical inner tube  11 . The inner tube  11  has a lower end that is open and has a ceiling. The processing chamber  10  also includes a cylindrical outer tube  12  that covers the outer side of the inner tube  11 . The lower end of the outer tube  12  is open and the outer tube  12  has a ceiling. The inner tube  11  and the outer tube  12  are each formed of a heat-resistant material such as quartz, and are coaxially arranged to form a double tube structure. 
     The ceiling of the inner tube  11  is flat, for example. An accommodation portion  13  that accommodates a gas nozzle along the longitudinal direction (vertical direction) of the inner tube  11  is formed at one side of the inner tube  11 . The accommodation portion  13  is a region portion of a protruding portion  14  that is formed by protruding a portion of a sidewall of the inner tube  11  toward the outside. 
     A rectangular opening  15  is formed at the sidewall of the inner tube  11  on an opposite side of the inner tube  11  from the accommodation portion  13 , so as to be along the longitudinal direction (vertical direction) of the inner tube  11 . 
     The opening  15  is a gas exhaust port formed so as to be capable to exhaust the gas in the inner tube  11 . The opening  15  has the same length as a length of a wafer boat  16 , or extends in both the upper and lower directions to be longer than the length of the wafer boat  16 . 
     A lower end of the processing chamber  10  is supported by a cylindrical manifold  17  made of, for example, stainless steel. A flange  18  is formed on an upper end of the manifold  17 , and a lower end of the outer tube  12  is provided to be supported on the flange  18 . A sealing member  19 , such as an O-ring, is interposed between the flange  18  and the lower end of the outer tube  12  so that an interior of the outer tube  12  is hermetically sealed. 
     An annular support  20  is provided at an inner wall of the upper portion of the manifold  17 , and the lower end of the inner tube  11  is provided to be supported on the support  20 . A cover  21  is hermetically attached to an opening at the lower end of the manifold  17  through the sealing member  22  such as an O-ring, so as to hermetically close the opening at the lower end of the processing chamber  10 , that is, the opening of the manifold  17 . The cover  21  is made of stainless steel, for example. 
     A rotation shaft  24 , which rotatably supports the wafer boat  16  through a magnetic fluid sealing portion  23 , is provided at the central portion of the cover  21  to pass through the cover  21 . A lower portion of the rotation shaft  24  is rotatably supported by an arm  25 A of an elevation mechanism  25  that includes a boat elevator. 
     A rotation plate  26  is provided at an upper end of the rotation shaft  24 , and the wafer boat  16  that holds the substrates  100  is provided above the rotation plate  26 , via a heated platform  27  made of quartz. With this arrangement, the cover  21  and the wafer boat  16  are integrally moved up and down by raising and lowering the elevation mechanism  25 . Thus, the wafer boat  16  can be inserted into or removed from the processing chamber  10 . The wafer boat  16  can be accommodated by the processing chamber  10  and substantially horizontally holds a plurality of (for example, 50 to 150) substrates  100 , such that the substrates  100  are spaced apart from one another when viewed in the vertical direction. 
     The gas supply  30  includes a gas nozzle  31  via which process gas and purge gas are supplied into the inner tube  11  in each of the first deposition step S 1  and the second deposition step S 2 . As the process gas, monosilane (SiH 4 ) gas that is a silicon-containing gas is used, and as the purge gas, for example, nitrogen gas (N 2 ) or argon gas (Ar) can be used. 
     The gas nozzle  31  is made of, for example, quartz, and is provided in the inner tube  11  along a longitudinal direction of the inner tube  11 . Also, a base end of the gas nozzle  31  is bent in an L-shape, and is supported so as to pass through the manifold  17 . Gas holes  32  are formed at the gas nozzle  31  along the longitudinal direction of the gas nozzle  31 , and the process gas is horizontally discharged via the gas holes  32 . The gas holes  32  are arranged at the same intervals as intervals of the substrates  100  that are supported by the wafer boat  16 , for example. The process gas of which a flow rate is controlled is introduced into the gas nozzle  31 . 
     Although  FIG.  3    illustrates a case where the gas supply  30  includes one gas nozzle  31 , the gas supply  30  is not limited to the manner described above. For example, the gas supply  30  may include gas nozzles. For example, the monosilane gas and the purge gas may be respectively supplied into the inner tube  11  from different gas nozzles. 
     The exhaust device  40  exhausts the gas discharged from the interior of the inner tube  11 , through the opening  15 . Also, the exhaust device  40  exhausts the gas discharged from a gas outlet  41 , through a space P 1 , which is between the inner tube  11  and the outer tube  12 . The gas outlet  41  is formed at the sidewall of the upper portion of the manifold  17  so as to be situated above the support  20 . An exhaust passage  42  is connected to the gas outlet  41 . A pressure regulating valve  43  and a vacuum pump  44  are separately provided downstream of the exhaust passage  42  to allow an internal pressure of the processing chamber  10  to be adjusted. 
     The heater  50  is provided to enclose a periphery of the outer tube  12 . The heater  50  is fixed, for example, above the base plate  28 . The heater  50  has a cylindrical shape so as to cover the outer tube  12 . The heater  50  includes, for example, a heating element, and heats the substrates  100  in the processing chamber  10 . 
     The controller  80  controls the operation of each component of the processing apparatus  1 . The controller  80  may be implemented, for example, by a computer that includes one or more processors, a memory, an input-and-output interface, and an electronic circuit that are not illustrated. Each processor includes a combination of one or more among a central processing unit (CPU), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a circuit constituted by discrete semiconductors, and the like. The memory includes a volatile memory and a non-volatile memory. The memory also includes a storage medium  90  (for example, a compact disk, a digital versatile disc (DVD), a hard disk, a flash memory, or the like) coupled to the controller  80 . A program, which causes the processing apparatus  1  to operate, and a recipe (process condition) for a substrate process are stored in the storage medium  90 . 
     Hereafter, the operation of the processing apparatus  1  will be described. The controller  80  controls the operation of each component of the processing apparatus  1  to perform the method for forming a polycrystalline silicon film, as follows. 
     First, in the substrate process in the processing apparatus  1 , the wafer boat  16  on which the substrates  100  are mounted is transferred to the processing chamber  10 . Next, the opening at the lower end of the manifold  17  is closed by the cover  21 , and thus the interior of the processing chamber  10  forms a sealed space. 
     After forming the sealed space, the processing apparatus  1  performs the first deposition step S 1 . In the first deposition step S 1  according to the present embodiment, the deposition process for each substrate  100  is performed under the following process condition.
         Processing gas: monosilane (SiH 4 ) gas   Temperature in processing chamber  10 : greater than or equal to 300° C. and less than or equal to 440° C.   Pressure of processing chamber  10 : greater than or equal to 10 Torr (i.e., about 1.3 kPa) and less than or equal to 100 Torr (i.e., about 13 kPa)   Flow rate of process gas: greater than or equal to 0. 1 slm and less than or equal to 3 slm       

     That is, in the processing apparatus  1 , a thermal decomposition temperature of the monosilane gas in the first deposition step S 1  is set to a temperature (300° C. to 440° C.) less than a thermal decomposition temperature (450° C. to 530° C.) generally used in a conventional deposition process. The thermal decomposition temperature of the monosilane gas in the first deposition step S 1  is less than a thermal decomposition temperature of the monosilane gas in the second deposition step S 2  described below. 
       FIG.  4 A  is a logarithmic graph indicating the relationship of a hydrogen concentration in a film that constitutes the seed layer  121  to the temperature in the processing chamber  10  in the first deposition step S 1 . On the graph, the horizontal axis represents the temperature in the processing chamber  10 , and the vertical axis represents the hydrogen concentration in the film. As can be seen from this graph, in the deposition process that uses the monosilane gas, the hydrogen concentration in the film increases as the temperature in the processing chamber  10  decreases. That is, by performing the deposition process in an environment in which a thermal decomposition temperature of the monosilane gas is reduced, more hydrogen contained in the monosilane gas remains in the seed layer  121 . 
     With this approach, when the hydrogen concentration in the film is increased, in a case where crystallization is carried out in the crystallization step S 3 , a polycrystalline silicon film having a large grain size can be formed due to desorption of hydrogen. In other words, in the first deposition step S 1 , the seed layer  121  is formed by heating the substrate  100  at a temperature in the range of greater than or equal to 300° C. and less than or equal to 440° C., thereby facilitating increases in the grain size of the polycrystalline silicon film. 
     The processing apparatus  1  performs the deposition process, while maintaining the pressure of the processing chamber  10  at high pressure, in order to suppress reductions in a particle size of silicon nucleus in the seed layer  121  due to the reduced thermal decomposition temperature of the monosilane gas in the first deposition step S 1 . Specifically, as specified in the above process condition, the processing apparatus  1  sets the pressure of the processing chamber  10  in the first deposition step S 1  to a pressure (e.g., 10 Torr to 100 Torr) greater than a pressure (5 Torr or less, i.e., about 667 Pa or less) generally used in the conventional deposition process. The pressure of the processing chamber  10  in the first deposition step S 1  is greater than the pressure of the processing chamber  10  in the second deposition step S 2  described below. 
       FIG.  4 B  is a logarithmic graph indicating the relationship of the hydrogen concentration in a film that constitutes the seed layer  121  to the pressure of the processing chamber  10 , in a case where the temperature in the processing chamber  10  is 430° C. On the graph, the horizontal axis represents the pressure of the processing chamber  10 , and the vertical axis represents the hydrogen concentration in the film. As can be seen from this graph, in the deposition process that uses the monosilane gas, when the temperature in the processing chamber  10  stays constant, the hydrogen concentration in the film increases as the pressure of the processing chamber  10  increases. That is, by performing the deposition process in an environment in which the pressure of the processing chamber  10  is increased, more hydrogen contained in the monosilane gas remains in the seed layer  121 . 
     In order to maintain the pressure of the processing chamber  10  at a constant level, the processing apparatus  1  preferably sets a flow rate of the monosilane gas that the gas supply  30  supplies into the processing chamber  10 , to be in the range of 0. 1 slm to 3 slm. With this approach, the processing apparatus  1  can stably supply the monosilane gas onto each substrate  100  that is placed in the processing chamber  10 , thereby enabling the deposition of the seed layer  121  to progress. 
     In order to satisfy the process condition in the first deposition step S 1 , the controller  80  controls the exhaust device  40  to vacuum-evacuate the interior of the processing chamber  10  to thereby maintain the interior of the processing chamber  10  at a predetermined pressure (for example, 19 Torr) in the range of greater than or equal to 10 Torr and less than equal to 100 Torr, as specified in the process condition. The controller  80  also controls the power supplied to the heater  50  to increase the temperature in the processing chamber  10  to a predetermined temperature (for example, 380° C.) in the range of greater than or equal to 300° C. and less than or equal to 440° C., as specified in the process condition. 
     When the pressure of the processing chamber  10  is stabilized at a predetermined pressure and the temperature in the processing chamber  10  is stabilized at a predetermined temperature, monosilane gas is supplied into the processing chamber  10 . For a supplied amount of the monosilane gas, a predetermined flow rate (for example, 0. 3 slm) is set in the range of greater than or equal to 0. 1 slm and less than or equal to 3 slm, as specified in the process condition. In the processing apparatus  1 , the wafer boat  16  may rotate in response to supplying of the monosilane gas. The processing apparatus  1  performs the above deposition process over any process time. 
     With this approach, the processing apparatus  1  can deposit the first amorphous silicon film (seed layer  121 ) having a uniform film thickness on the insulating film  110 . When the seed layer  121  having a desired film thickness is formed, the processing apparatus  1  terminates the first deposition step S 1 . The processing apparatus  1  continues to rotate the wafer boat  16  even after the first deposition step S 1  is terminated. 
     Subsequently, the processing apparatus  1  performs the second deposition step S 2 . In the second deposition step S 2 , the deposition process for each substrate  100  is performed under the following process condition.
         Process gas: silicon-containing gas   Temperature in processing chamber  10 : greater than 450° C. and less than or equal to 530° C.   Pressure of the processing chamber  10 : 5 Torr (i.e., about 1. 3 kPa) or less   Flow rate of process gas: greater than or equal to 0. 1 slm and less than or equal to 5 slm       

     As the silicon-containing gas in the second deposition step S 2 , for example, monosilane gas, a high order silane gas, a halogen-containing silicon gas, or a mixture gas of two or more among the monosilane gas, the high order silane gas, and the halogen-containing silicon gas can be used. Examples of the halogen-containing silicon gas include (i) a fluorine-containing silicon gas such as SiF 4 , SiHF 3 , SiH 2 F 2 , or SiH 3 F, (ii) a chlorine-containing silicon gas such as SiCl 4 , SiHCl 3 , SiH 2 Cl 2  (DCS), or SiH 3 Cl, and (iii) a bromine-containing gas such as SiBr 4 , SiHBr 3 , SiH 2 Br 2 , or SiH 3 Br. As the silicon-containing gas in the second deposition step S 2  according to the present embodiment, monosilane gas is applied from the viewpoint of an increased deposition rate and low costs. 
     When the process shifts from the first deposition step S 1  to the second deposition step S 2 , the processing apparatus  1  continues to supply the monosilane gas into the processing chamber  10  while continuing to rotate the wafer boat  16 . Then, the processing apparatus  1  changes from the pressure of the processing chamber  10  in the first deposition step S 1 , to a predetermined pressure in the range of 5 Torr or less, as specified in the process condition used in the second deposition step S 2 . The processing apparatus  1  also adjusts the power supplied to the heater  50  to adjust the temperature in the processing chamber  10  to a predetermined temperature (for example, 470° C.) in the range of greater than or equal to 450° C. and less than or equal to 530° C., which is specified in the process condition. 
     Then, the processing apparatus  1  performs the second deposition step S 2  over any process time, in a state where the pressure of the processing chamber  10  is stabilized at a given pressure specified in the second deposition step S 2  and the temperatures of the processing chamber  10  is stabilized at a given temperature specified in the second deposition step S 2 . With this approach, the bulk layer  122  that covers the seed layer  121  is formed. After the seed layer  121  is entirely covered with the bulk layer  122 , supplying of the monosilane gas into the processing chamber  10  is stopped. The processing apparatus  1  continues to rotate the wafer boat  16  even after the second deposition step S 2  is terminated. 
     Finally, the processing apparatus  1  performs the crystallization step S 3 . At this time, in the processing apparatus  1 , the interior of the processing chamber  10  is subject to an inert gas atmosphere. The inert gas atmosphere may be, for example, a nitrogen atmosphere or an argon atmosphere. Instead of the inert gas atmosphere, a reducing gas atmosphere such as a hydrogen atmosphere may be used. In the present embodiment, although the crystallization step S 3  is performed by the same apparatus as a given apparatus that performs the first deposition step S 1  and the second deposition step S 2 , such a manner is not limiting. The crystallization step S 3  may be performed by a different apparatus from the given apparatus that performs the first deposition step S 1  and the second deposition step S 2 . 
     In the processing apparatus  1 , the temperature in the processing chamber is adjusted to a given temperature in the crystallization step S 3 , by adjusting the power supplied to the heater  50 . The given temperature in the crystallization step S 3  may be a predetermined temperature (for example, 650° C.) in the range of greater than or equal to 550° C. and less than or equal to 700° C. With this approach, crystallization of the seed layer  121  and the bulk layer  122  progresses. As described above, in the present embodiment, the seed layer  121  is formed in a low temperature and high pressure environment, and thus silicon in the seed layer  121  is nucleated significantly, and thus the nucleated silicon causes the bulk layer  122  to be crystallized. With this approach, the polycrystalline silicon film having a large grain size can be formed. 
     As illustrated in  FIG.  5 A , the deposition process in the first deposition step S 1  according to the present embodiment is particularly effective for the insulating film  110  that includes (i) a flat portion  111  that is flat and continuous along a plane of the substrate  100  and (ii) a recess  112  recessed from the flat portion  111  in a thickness direction of the substrate  100 . The recess  112  in the insulating film  110  may include a hole, a trench, or the like. In each of  FIG.  5 A  and  FIG.  5 B  below, positions TOP, MID 1 , MID 2 , MID 3 , and BTM, which are each marked at a location among seed layers  121  and  221  present in recesses  112 , indicate measurement positions where film thicknesses of a given film are measured, and each measurement position is set along a depth direction of a given recess  112 . TOP is the measurement position where the film thickness is measured around an opening of a given recess  112 , and BTM is the measurement position where the film thickness is measured proximal to an bottom of the given recess  112 . MID 1 , MID 2 , and MID 3  are measurement positions where film thicknesses are measured, and those measurement positions are set at intervals in this order, when viewed in the direction from the TOP to the BTM. 
     In the deposition process according to the present embodiment, the seed layer  121  is formed on the insulating film  110  by using the monosilane gas, thereby allowing increased coverage for coating of the recess  112 , as illustrated in  FIG.  5 A . In other words, each of the above film deposition method and the method for forming a polycrystalline silicon film can form the seed layer  121  having a uniform film thickness on an inner surface of the recess  112  and along the depth direction of the recess  112 . 
     In contrast, in the conventional deposition process, as illustrated in  FIG.  5 B , a seed layer  221  is formed on an insulating film  210  using a high order silane gas such as disilane (Si 2 H 6 ) gas. The disilane gas does not easily enter a deep portion of a recess  212 , and consequently coverage for the coating of the recess  212  is decreased. With this arrangement, the disilane gas forms the seed layer  221  that is thin, when viewed from an opening (TOP-side) of the recess  212  toward a bottom (BTM-side) thereof. 
     Specifically, when the film thickness of the seed layer  121 , which is obtained in the deposition process according to the present embodiment, is compared with the film thickness of the seed layer  221 , which is obtained in the conventional deposition process, a comparison result is as illustrated in  FIG.  5 C . On the graph in  FIG.  5 C , TOP, MID 1 , MID 2 , MID 3 , and BTM on the horizontal axis respectively correspond to TOP, MID 1 , MID 2 , MID 3 , and BTM in each of  FIGS.  5 A and  5 B . Also, on the graph in  FIG.  5 C , the vertical axis represents a ratio (which indicates a ratio of film thicknesses) of a given film thickness at each given measurement position, to a given film thickness at TOP, with respect to each of the recesses  112  and  212 . 
     As illustrated in  FIG.  5 C , for the seed layer  221  formed in the conventional deposition process, a ratio of a given film thickness at BTM to a given film thickness at TOP was 67.9%. With this arrangement, the thickness of the bottom film is reduced, and thus in a subsequent step process, the film thickness of the bulk layer  222 , which is laminated on the seed layer  221 , may be nonuniform. 
     In contrast, for the seed layer  121  formed in the deposition process according to the present embodiment, a ratio of a given film thickness at BTM to a given film thickness at TOP was 97.7%. That is, it can be seen that in the deposition process according to the present embodiment, the seed layer  121  having a uniform film thickness is formed on the inner surface of the recess  112 , compared to the conventional deposition process. With use of the seed layer  121  having a more uniform film thickness, the bulk layer  122  deposited in the second deposition step S 2  is also deposited on the inner surface of the recess  112  to have a more uniform film thickness. 
     The coverage for the seed layer  121  formed by the film deposition method according to the present embodiment is superior to the coverage for the seed layer  221  formed by the conventional deposition process. With this approach, in the deposition process according to the present embodiment, the film thickness of the seed layer  121  formed on the flat portion  111  can be made uniform, compared to the film thickness of the seed layer  221  formed on a flat portion  211  in the conventional deposition process. Also, the film deposition method according to the present embodiment is not limited to depositing of the seed layer  121 , and may be applied to any other deposition in accordance with a purpose such as achieving of a uniform film thickness. 
     The technical concept and effect described in the above embodiments will be described below. 
     A first aspect of the present disclosure relates to a film deposition method for forming an amorphous silicon film (seed layer  121 ) in a substrate  100 . The film deposition method includes performing a deposition process under process condition of (a) and (b) below, while supplying monosilane (SiH 4 ) gas into a processing chamber  10  that accommodates the substrate  100 . 
     (a) Setting a temperature in the processing chamber  10  to be in the range of greater than or equal to 300° C. and less than or equal to 440° C.
 
(b) Setting a pressure of the processing chamber  10  to be in the range of greater than or equal to 10 Torr and less than or equal to 100 Torr.
 
     According to the above aspect, the film deposition method supplies monosilane (SiH 4 ) gas into the processing chamber  10  in a low temperature and high pressure environment. As a result, an amorphous silicon film having a more uniform film thickness can be formed in the substrate  100 . With this approach, for example, when the amorphous silicon film to be deposited is the seed layer  121  that is nucleated at an interface portion in the substrate  100 , coverage for the seed layer  121  can be increased. Also, in the film deposition method, when the amorphous silicon film is crystallized, the crystallized amorphous silicon film can have a large grain size. 
     A film deposition process further includes the process condition of (c) below. 
     (c) Setting a flow rate of monosilane (SiH 4 ) gas supplied into a processing chamber  10  to be in the range of greater than or equal to 0.1 slm and less than or equal to 3 slm. 
     With this approach, in the film deposition method, even under the above process condition of (a) and (b), monosilane gas can be stably supplied into the processing chamber  10 , and thus deposition can be facilitated in the substrate  100 . 
     The substrate  100  has a flat portion  111  that is flat and continuous along a plane of the substrate  100 , and in a deposition process, an amorphous silicon film (seed layer  121 ) is deposited on the flat portion  111 . With this approach, in the film deposition method, an amorphous silicon film having a more uniform film thickness can be formed on the flat portion  111 . 
     The substrate  100  further has a recess  112  recessed from a flat portion  111  in a thickness direction of the substrate  100 , and in a deposition process, an amorphous silicon film (seed layer  121 ) is deposited on each of the flat portion  111  and the recess  112 . As described above, even when the substrate  100  has the recess  112 , in the film deposition method, an amorphous silicon film (seed layer  121 ) having a more uniform film thickness can be formed on an inner surface of the recess  112  along the thickness direction of the substrate  100 , by supplying monosilane gas in a low temperature and high pressure environment. 
     An insulating film  110  is formed in a substrate  100 , and an amorphous silicon film (seed layer  121 ) is formed on the insulating film  110 . With this approach, in a film deposition method, an amorphous silicon film having a more uniform film thickness can be formed on the insulating film  110 . 
     A second aspect of the present disclosure relates to a method for forming a polycrystalline silicon film. The method includes (i) forming a first amorphous silicon film (seed layer  121 ) in a substrate  100 , (ii) forming a second amorphous silicon film (bulk layer  122 ) that covers the first amorphous silicon film, and (iii) heating the substrate  100 . The forming of the first amorphous silicon film in the substrate  100  includes performing a deposition process under the process condition of (a) and (b) below, while supplying monosilane (SiH 4 ) gas into a processing chamber  10  that accommodates the substrate  100 . 
     (a) Setting a temperature in the processing chamber  10  to be in the range of greater than or equal to 300° C. and less than or equal to 440° C.
 
(b) Setting a pressure of the processing chamber  10  to be in the range of greater than or equal to 10 Torr and less than or equal to 100 Torr.
 
     With this approach, in the method for forming a polycrystalline silicon film, a first amorphous silicon film having a more uniform film thickness can be formed in a substrate  100 . 
     The forming of a second amorphous silicon film (bulk layer  122 ) is performed at a high temperature and a low pressure, compared to the forming of a first amorphous silicon film (seed layer  121 ) in a substrate  100 . With this approach, in the method for forming a polycrystalline silicon film, the bulk layer  122  can be efficiently formed on the seed layer  121 . 
     The forming of a second amorphous silicon film (bulk layer  122 ) includes performing a film deposition process under the process condition of (d) and (e) below, while supplying monosilane (SiH 4 ) gas into a processing chamber  10 . 
     (d) Setting a temperature in a processing chamber  10  to be in the range of greater than or equal to 450° C. and less than or equal to 530° C.
 
(e) Setting a pressure of a processing chamber  10  to 5 Torr or less.
 
     With this approach, in the method for forming a polycrystalline silicon film, a second amorphous silicon film having a desired film thickness can be stably formed on a first amorphous silicon film (seed layer  121 ). 
     While certain embodiments are described using the film deposition method and the method for forming a polycrystalline silicon film, these embodiments are 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 scope of the disclosures. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope of the disclosures. 
     The above embodiments are described using a case where the processing apparatus is a batch-type apparatus in which substrates are processed at the same time. However, the present disclosure is not limited to the above type. For example, the processing apparatus may be a single-substrate processing apparatus in which substrates are processed one by one. 
     According to the above embodiments, an amorphous silicon film having a more uniform film thickness is capable of being formed.