Patent Publication Number: US-2022223463-A1

Title: Deposition apparatus and deposition method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application is based on and claims priority to Japanese Patent Application No. 2021-003756 filed on Jan. 13, 2021, the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a deposition apparatus and a deposition method. 
     BACKGROUND 
     In a substrate processing apparatus that performs a process by supplying a process gas to a wafer while causing the wafer mounted on a susceptor in a processing chamber to revolve, a configuration in which a recess for mounting the wafer on the surface of the susceptor is provided is known (see, for example, Patent Document 1). In the substrate processing apparatus, a stage that supports the center of the wafer from a lower side is provided in the recess, and a circumferential edge portion of the wafer floats from the bottom of the recess. 
     RELATED ART DOCUMENT 
     Patent Document 
     
         
         [Patent Document 1] Japanese Laid-open Patent Application Publication No. 2013-222948 
       
    
     SUMMARY 
     According to one aspect of the present disclosure, a deposition apparatus includes a processing chamber, and a susceptor provided in the processing chamber. The susceptor has a recess on a surface of the susceptor. The recess includes a support and a groove, the support supports a region that includes a center of a substrate and that does not include an edge of the substrate, the groove is located around the support, and the groove is recessed relative to the support. The deposition apparatus further includes a process gas supply configured to supply a process gas to the surface of the susceptor and a purge gas supply configured to supply a purge gas to the groove. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view illustrating an example of a deposition apparatus according to an embodiment; 
         FIG. 2  is a horizontal cross-sectional view of the deposition apparatus in  FIG. 1 ; 
         FIG. 3  is a horizontal cross-sectional view of the deposition apparatus in  FIG. 1 ; 
         FIG. 4  is a perspective view illustrating a portion of an interior of the deposition apparatus in  FIG. 1 ; 
         FIG. 5  is a plan view illustrating an example of a susceptor of the deposition apparatus in  FIG. 1 ; 
         FIG. 6  is a drawing illustrating an enlarged recess of the receptor of  FIG. 5 ; 
         FIG. 7  is a drawing illustrating a cross-section cut along a dash-dot-dash line IIV-IIV in  FIG. 6 ; 
         FIG. 8  is an enlarged view of a region A 1  in  FIG. 7 ; 
         FIG. 9  is an enlarged view of a region A 2  in  FIG. 7 ; 
         FIG. 10  is a cross-sectional view illustrating a function of a conventional susceptor; 
         FIG. 11  is a cross-sectional view illustrating the function of the conventional susceptor; 
         FIG. 12  is a cross-sectional view illustrating the function of the conventional susceptor; 
         FIG. 13  is a cross-sectional view illustrating the function of the conventional susceptor; 
         FIG. 14  is a graph for describing a film deposited on a wafer when using the conventional susceptor; 
         FIG. 15  is a cross-sectional view illustrating another example of the susceptor of the deposition apparatus of  FIG. 1 ; and 
         FIG. 16  is a flow chart illustrating an example of a deposition method of the embodiment. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     According to the present disclosure, deposition on a back surface edge portion of a substrate can be suppressed. 
     In the following, an embodiment, which is a non-restrictive example, of the present disclosure will be described with reference to the accompanying drawings. In all the accompanying drawings, the same or corresponding reference numerals will be used to refer to the same or corresponding members or parts and the overlapped description will be omitted. 
     [Deposition Apparatus] 
     An example of a deposition apparatus according to an embodiment will be described with reference to  FIGS. 1 to 4 . The deposition apparatus according to the embodiment includes a processing chamber  1  having a substantially circular shape as a plane shape and a susceptor  2  that is provided in the processing chamber  1  and that has a center of rotation at the center of the processing chamber  1 . The deposition apparatus is configured as an apparatus that performs a deposition process on a substrate (for example, a wafer W). In the following, each part of the deposition apparatus will be described. 
     The processing chamber  1  is a vacuum chamber that can decompress the inside. The processing chamber  1  includes a top plate  11  and a chamber body  12 . The top plate  11  is removably attached to the chamber body  12  through a seal member  13 . A separation gas supply line  51  is provided at the center in the upper surface of the top plate  11 . The separation gas supply line  51  supplies a nitrogen (N 2 ) gas as a separation gas in order to suppress mixing of different process gases in a central region C in the processing chamber  1 . 
     A heater  7  is provided above a bottom  14  of the processing chamber  1  ( FIG. 1 ). The heater  7  heats the wafer W on the susceptor  2  to the deposition temperature (e.g., 300° C.) through the susceptor  2 . A cover member  71   a  is provided at the side of the heater  7 , and a cover member  7   a  that covers the heater  7  is provided above the heater  7 . On the bottom  14  below the heater  7 , multiple purge gas supply lines  73  are provided over a circumferential direction to purge a space in which the heater  7  is provided. 
     The susceptor  2  is fixed to a core  21  that has a substantially cylindrical shape, at the center of the susceptor  2 . The susceptor  2  is configured to rotate clockwise about the vertical axis in this example, by a rotating shaft  22  that is connected to the lower surface of the core  21  and that extends in the vertical direction. The rotating shaft  22  is rotated about the vertical axis by a drive section  23 . The rotating shaft  22  and the drive section  23  are accommodated in a case body  20 . An upper flange of the case body  20  is airtightly attached to the lower surface of the bottom  14  of the processing chamber  1 . Additionally, a purge gas supply line  72  is connected to the case body  20  for supplying the N 2  gas as the purge gas to a lower region of the susceptor  2 . The bottom  14  of the processing chamber  1  is annularly formed at the outer circumferential side of the core  21  to come closer to the lower side of the susceptor  2  to form a protrusion  12   a.    
     A recess  24  is provided on the surface of the susceptor  2 . The recess  24  has a circular shape in a plan view and holds the wafer W with the wafer W being dropped in the recess  24 . The wafer W may be, for example, a silicon wafer having a circular plate shape (a circular shape). The recesses  24  are formed at multiple locations along the direction of rotation (the circumferential direction) of the susceptor  2 . In the examples of  FIGS. 1-4 , the recesses  24  are formed at five locations along the direction of rotation (the circumferential direction) of the susceptor  2 . Each recess  24  is formed such that the diameter thereof is greater than the diameter of the wafer W in a plan view in order to provide a clearance area between the outer edge thereof and the outer edge of the wafer W. The diameter of the susceptor  2  is about 1000 mm, for example. In the recess  24 , through-holes  24   a  through which, for example, three lift pins (not illustrated) protrude and retract to move the wafer W up and down from the lower side are formed. In  FIG. 2  and  FIG. 3 , the diameter dimensions of the recesses  24  are simplified. In  FIGS. 1 to 3 , the through-holes  24   a  are not illustrated. 
     At respective positions opposite to regions where the recesses  24  pass by, six nozzles  31 ,  32 ,  34 ,  35 ,  41 , and  42  made of, for example, quartz are radially provided spaced from each other in the circumferential direction of the processing chamber  1 . Each of the nozzles  31 ,  32 ,  34 ,  35 ,  41 , and  42  is attached, for example, to extend horizontally from the outer wall surface of the processing chamber  1  toward the central region C, and to be opposite to the wafer W. In this example, a plasma generation gas nozzle  34 , a separation gas nozzle  41 , a cleaning gas nozzle  35 , a first process gas nozzle  31 , a separation gas nozzle  42 , and a second process gas nozzle  32  are arranged in this order in the direction of rotation of the susceptor  2  as seen from a transfer port  15  described below. A plasma generator  80  is provided above the plasma generation gas nozzle  34  to make plasma from a gas discharged from the plasma generation gas nozzle  34 . The plasma generator  80  will be described later. 
     The first process gas nozzle  31  and the second process gas nozzle  32  respectively serve in a first process gas supply and a second process gas supply, the separation gas nozzles  41  and  42  respectively serve in separation gas supplies, and the cleaning gas nozzle  35  serves in a cleaning gas supply.  FIG. 2  and  FIG. 4  illustrate a state in which the plasma generator  80  and a housing  90  described later are detached such that the plasma generation gas nozzle  34  can be seen.  FIG. 3  illustrates a state in which the plasma generator  80  and the housing  90  are attached. 
     The nozzles  31 ,  32 ,  34 ,  35 ,  41 , and  42  are respectively connected to the following gas supply sources (not illustrated) through flow control valves. That is, the first process gas nozzle  31  is connected to a supply source of the first process gas that contains silicon (Si). The first process gas may be, for example, a BTBAS (vistar-butyl aminosilane, SiH 2  (NH—C(CH 3 ) 3 ) 2 ) gas. The second process gas nozzle  32  is connected to a supply source of the second process gas (e.g., a mixed gas of an ozone (O 3 ) gas and an oxygen (O 2 ) gas) (in detail, an oxygen gas source with an ozonizer). The plasma generation gas nozzle  34  is connected to a supply source of the plasma generation gas formed of, for example, a mixed gas of an argon (Ar) gas and an O 2  gas. The separation gas nozzles  41  and  42  are respectively connected to gas supply sources of an N 2  gas, which is the separation gas. At the lower surfaces of the nozzles  31 ,  32 ,  34 ,  41 , and  42 , gas discharge holes (not illustrated) are formed at multiple locations along the radial direction of the susceptor  2  to be equally spaced, for example. 
     The lower region of the first process gas nozzle  31  is a first process region P 1  for adsorbing the first process gas onto the wafer W. The lower region of the second process gas nozzle  32  is a second process region P 2  for reacting the component of the first process gas adsorbed onto the wafer W with the second process gas. The separation gas nozzles  41  and  42  respectively form separation regions D that separate the first process region P 1  and the second process region P 2 . A convex portion  4  having an approximate fan shape as illustrated in  FIG. 2  and  FIG. 3  is provided on the top plate  11  of the processing chamber  1  in the separation region D, and the separation gas nozzles  41  and  42  are accommodated in the convex portions  4 . Thus, at both sides of the separation gas nozzles  41  and  42  in the circumferential direction of the susceptor  2 , lower ceiling surfaces that are a lower surface of the convex portion  4  are provided in order to prevent the process gases from mixing with each other, and at both sides in the circumferential direction of the ceiling surface, ceiling surfaces higher than the ceiling surface (i.e., the lower surface of the convex portion  4 ) are provided. A circumferential edge portion of the convex portion  4  (a portion on the outer edge side of the processing chamber  1 ) is bent in an L-shape so as to face the outer edge surface of the susceptor  2  and be slightly spaced from the chamber body  12  in order to prevent the process gases from mixing with each other. 
     Next, a plasma generator  80  will be described. The plasma generator  80  is configured by winding an antenna  83  made of a metal wire in a coil form and is disposed so as to be over the passing area of the wafer W from the central portion to the circumferential edge portion of the susceptor  2 . The antenna  83  is disposed to connect, through a matcher  84 , a high-frequency power supply  85  having a frequency of 13.56 MHz and output power of 5000 W, for example, and to be airtightly partitioned from the internal area of the processing chamber  1 . The plasma generator  80 , the matcher  84 , and the high-frequency power supply  85  are electrically connected by a connection electrode  86 . That is, the top plate  11  has an opening having an approximate fan shape above the plasma generation gas nozzle  34  in a plan view and is airtightly sealed by a housing  90  made of, for example, quartz. The housing  90  is formed such that the circumferential edge portion extends horizontally over the circumferential direction in a flange form and the center portion is recessed toward the internal area of the processing chamber  1 , and the antenna  83  is accommodated inside the housing  90 . A sealing member  11   a  is provided between the housing  90  and the top plate  11 . The circumferential edge portion of the housing  90  is pressed downwardly by a pressing member  91 . 
     An outer edge portion of the lower surface of the housing  90  extends vertically over the circumferential direction to the lower side (the susceptor  2  side) to form a protrusion  92  for gas control, in order to prevent the entry of the N 2  gas, the O 3  gas), or the like into the lower area of the housing  90 , as illustrated in  FIG. 1 . The plasma generation gas nozzle  34  is accommodated in an area surrounded by the inner circumferential surface of the protrusion  92 , the lower surface of the housing  90 , and the upper surface of the susceptor  2 . 
     Between the housing  90  and the antenna  83 , a substantially box-shaped Faraday shield  95  having an opening upward, as illustrated in  FIGS. 1 and 3 , is disposed. The Faraday shield  95  is formed of a metal plate that is an electrically conductive plate and is grounded. Slits  97  formed so as to extend in a direction orthogonal to the winding direction of the antenna  83  are provided on the bottom surface of the Faraday shield  95  and are positioned at the lower position of the antenna  83  over the circumferential direction. The slit  97  prevents the electric field component of the electric field and the magnetic field (the electromagnetic field) generated at the antenna  83  from moving downward toward the wafer W and allows the magnetic field to reach the wafer W. An insulating plate  94  is interposed between the Faraday shield  95  and the antenna  83 . The insulating plate  94  is formed, for example, of quartz, and insulates the Faraday shield  95  and the antenna  83 . 
     An annular side ring  100  is disposed on the outer circumferential side of the susceptor  2  slightly below the susceptor  2 . On the upper surface of the side ring  100 , two exhaust ports  61  and  62  are formed to be spaced from each other in the circumferential direction. In other words, two exhaust ports are formed in the bottom  14  of the processing chamber  1 , and the exhaust ports  61  and  62  are formed in the side ring  100  at positions corresponding to these exhaust ports. The exhaust port  61  is formed at a position that is between the first process gas nozzle  31  and the separation region D on the downstream side of the susceptor in the rotation direction from the first process gas nozzle  31  and that is closer to the separation region D. The exhaust port  62  is formed at a position that is between the plasma generation gas nozzle  34  and the separation region D on the downstream side of the susceptor in the rotation direction from the plasma generation gas nozzle  34  and that is closer to the separation region D. 
     The exhaust port  61  is for exhausting the first process gas and the separation gas, and the exhaust port  62  is for exhausting the plasma generation gas in addition to the second process gas and the separation gas. Additionally, the exhaust port  62  exhausts the cleaning gas during cleaning. A gas flow path  101  having a groove shape is formed on the upper surface of the side ring  100  on the outer edge side of the housing  90  for allowing gas to flow through the exhaust port  62  while flowing around the housing  90 . As illustrated in  FIG. 1 , the exhaust ports  61  and  62  are connected to a vacuum pump  64  that is a vacuum exhaust mechanism, for example, through exhaust piping  63 , such as butterfly valves, in which a pressure adjuster  65  is provided between the exhaust ports  61  and  62  and the vacuum pump  64 . 
     In the center in the lower surface of the top plate  11 , as illustrated in  FIG. 2 , a protrusion  5  is provided. The protrusion  5  is formed in a substantially annular shape over the circumferential direction that continues from a portion of the central region C of the convex portion  4  and is formed such that the lower surface of the protrusion  5  is at the same height as the lower surface of the convex portion  4 . A labyrinth structure  110  is provided above the core  21  on the side of the center of rotation of the susceptor  2  from the protrusion  5  to prevent the first process gas and the second process gas from mixing with each other in the central region C. The labyrinth structure  110  has a structure in which a first wall  111  extending vertically from the susceptor  2  side toward the top plate  11  side over the circumferential direction and a second wall  112  extending vertically from the top plate  11  side to the susceptor  2  over the circumferential direction are alternately disposed in the radial direction of the susceptor  2 . 
     On the side wall of the processing chamber  1 , a transfer port  15  is formed for transferring the wafer W between an external transfer arm (not illustrated) and the susceptor  2 , as illustrated in  FIG. 2  and  FIG. 3 . The transfer port  15  is airtightly opened and closed by a gate valve G. A lift pin (not illustrated) is provided on the lower side of the susceptor  2  at a position facing the transfer port  15 . The lift pin lifts the wafer W from the back side through the through-hole  24   a  of the susceptor  2 . 
     The deposition apparatus includes a controller  120  formed of a computer that controls an operation of the entire apparatus. A memory of the controller  120  stores a program for performing a deposition method described later. The program includes a group of steps for performing an operation of the apparatus described later and is installed in the controller  120  from a storage unit  121  that is a storage medium such as a hard disk drive, a compact disk, an optical disk, a memory card, or a flexible disk. 
     &lt;Susceptor Structure&gt; 
     An example of the susceptor  2  of the deposition apparatus according to the embodiment will be described with reference to  FIGS. 5 to 9 . 
     The susceptor  2  is formed, for example, of quartz. The susceptor  2  is fixed to the core  21  having a substantially cylindrical shape, at the center of the susceptor  2 , as described above. The susceptor  2  is configured to rotate clockwise about the vertical axis in this example, by the rotating shaft  22  that is connected to the lower surface of the core  21  and that extends in the vertical direction ( FIGS. 1 to 4 ). 
     The susceptor  2  includes the recess  24 , a support  25 , a groove  26 , a porous ring  27 , the purge gas supply  28 , and an annular protrusion  29 . 
     The recesses  24  are formed at multiple locations (six locations in  FIG. 5 ) along the direction of rotation (the circumferential direction) of the susceptor  2 . Each recess  24  has a circular shape. Each recess  24  is formed such that the diameter thereof is greater than the diameter of the wafer W in a plan view in order to provide a clearance area between the outer edge thereof and the outer edge of the wafer W. In one embodiment, a diameter size r of the wafer is 300 mm and a diameter size R of the recess is 302 mm. 
     The support  25  is provided on the bottom surface of each recess  24 . The support  25  supports the center of the wafer W from the lower side. The support  25  is configured to have a cylindrical shape and have a horizontal surface on the top. The support  25  is formed to be in the shape of a smaller circle than the wafer W in a plan view so that a circumferential edge portion of the wafer W floats from the bottom surface of the recess  24  in the circumferential direction, i.e. the circumferential edge portion does not touch the support  25  (protruded from the support  25 ). Thus, the support  25  is formed such that when the wafer W is mounted on the support  25 , the circumferential edge portion of the wafer W faces the bottom surface of the recess  24  over the circumferential direction. 
     A height h of the support  25  is set such that the surface of the wafer W and the surface of the susceptor  2  are aligned, for example, when the wafer W is mounted on the support  25 . In one embodiment, the height h of the support  25  is about 0.03 mm to 0.2 mm, and a diameter d of the support  25  is 297 mm. 
     The groove  26  is formed around the support  25 , and more specifically, is formed between an inner wall surface of the recess  24  and an outer wall surface of the support  25 . The groove  26  has an annular shape. The support  25  is disposed in the center of the recess  24  in a plan view. That is, the center position of the support  25  and the center position of the recess  24  match in a plan view. Thus, a width L of the groove  26  is constant over the circumferential direction in a plan view. In one embodiment, the width L of the groove  26  is 2.5 mm. 
     The porous ring  27  is disposed at the circumferential edge portion of the support  25  between the back surface of the wafer W supported by the support  25  and the bottom surface of the groove  26 . The porous ring  27  has an annular shape. In one embodiment, the porous ring  27  is disposed such that an inner edge of the porous ring  27  is on a step  25   a  formed on the outer wall surface of the support  25  and there is a clearance V between the inner wall surface of the recess  24  and the porous ring  27 . The porous ring  27  is formed of, for example, a porous material, such as SiC, SiN, or the like. 
     The purge gas supply  28  supplies the purge gas to the groove  26 . In one embodiment, the purge gas supply  28  includes a gas flow path that radially extends from the central region C in the processing chamber  1  to the groove  26  formed in each recess  24  ( FIG. 5 ). The purge gas supply  28  may be, for example, a flow path through which the separation gas supplied from the separation gas supply line  51  to the central region C in the processing chamber  1  is directed to the groove  26  formed in each recess  24 . The purge gas supplied to the groove  26  is supplied to the back surface of the wafer W through the porous ring  27 . This can suppress the floating of the wafer W caused by the purge gas because the flow rate of the purge gas can be suppressed and the purge gas can be widely and evenly supplied. The purge gas supply  28  supplies the purge gas to the groove  26  when the process gas is supplied to the surface of the susceptor  2  in a state where the wafer W is mounted on the support  25 , for example. The purge gas supplied to the groove  26  prevents the process gas from contacting a back surface edge portion of the wafer W, the inner wall surface of the groove  26 , the bottom surface of the groove  26 , and the like. Thus, the deposition on the back surface edge portion of the wafer W, the inner wall surface of the groove  26 , the bottom surface of the groove  26 , and the like is suppressed. As a result, particles generated in the grooves  26  by the accumulation of the deposited films can be reduced, thereby improving throughput yield. Additionally, because the deposition on the back surface edge portion of the wafer W can be suppressed, the time of the process of etching and removing the film deposited on the back surface edge portion of the wafer W can be reduced or removed, thereby improving productivity. Further, because the deposition on the groove  26  is suppressed, the time of dry cleaning to remove the films deposited on the susceptor  2  can be reduced, thereby reducing the time in which the susceptor  2  is exposed to the etching gas and extending the life of the susceptor  2 . As a result, the cost associated with replacing the susceptor  2  can be reduced. In addition, the maintenance cycle can be extended, thereby improving productivity. 
     In one embodiment, the purge gas supply  28  starts supplying of the purge gas to the groove  26  before starting supplying the process gas to the surface of the susceptor  2 , and stops supplying of the purge gas to the groove  26  after stopping supplying the process gas to the surface of the susceptor  2 . The purge gas supply  28  may be formed, for example, by making holes in the interior of the susceptor  2  or by providing a groove on the surface of the susceptor  2 . 
     The annular protrusion  29  is provided along the groove  26 . The annular protrusion  29  has a circular shape in a plan view and protrudes from the bottom surface of the groove  26 . In one embodiment, the annular protrusion  29  has a height  29   h  that is less than a height  27   h  of the lower surface of the porous ring  27  relative to the bottom surface of the groove  26 . The annular protrusion  29  distributes the purge gas supplied from the purge gas supply  28  from the inner wall surface side of the recess  24  toward the outer wall surface side of the support  25  in the circumferential direction of the groove  26 . This allows the purge gas supplied from the purge gas supply  28  to the groove  26  to be supplied uniformly throughout the whole circumference of the back surface of the wafer W. 
     The reason why the groove  26  is formed between the inner wall surface of the recess  24  and the outer wall surface of the support  25  and the purge gas supply  28  that supplies the purge gas to the groove  26  is provided will be described with reference to  FIGS. 10 to 14 . 
     First, a case in which the wafer W is directly mounted on the bottom surface of the recess  24  without providing the support  25  will be described. If the unprocessed wafer W before being mounted on the susceptor  2  is at the ambient temperature, when the wafer W is mounted on the susceptor  2 , a temperature variation is generated in the plane, and then the temperature rises toward the deposition temperature, and the temperature variation is reduced. With respect to the above, if another heat treatment has already been performed on the wafer W by a heat treatment apparatus other than the deposition apparatus, spontaneous heat radiation of the wafer W is performed during the transfer to the deposition apparatus, and the temperature drop rate at this time becomes non-uniform in the plane of the wafer W. Thus, if a heat treatment is performed on the wafer W in advance, when the wafer W is mounted on the susceptor  2 , a temperature variation of the wafer W is already generated, and then the temperature variation gradually is reduced by the heat input from the susceptor  2 . 
     Therefore, when the wafer W is mounted on the susceptor  2 , the temperature variation is generated in the plane, regardless of whether the unprocessed wafer is at the ambient temperature or the heat treatment has already been performed on the wafer. At this time, based on the temperature variation of the wafer W, the wafer W may be curved in a shape of a mountain (convex upward). If the wafer W is curved in a shape of a mountain as described, the central portion of the wafer W is separated from the surface of the susceptor  2  and the circumferential edge portion of the wafer W comes into contact with the susceptor  2 . Then, as illustrated in  FIG. 10 , when the wafer W is mounted directly on the bottom surface of the recess  24 , the circumferential edge portion of the wafer W and the surface of the susceptor  2  (in particular, the bottom surface of the recess  24 ) rub against each other while the wafer W extends flatly as the temperature of the wafer W becomes uniform. As a result, particles P are generated. When the wafer W has extended flatly, for example, the particle P moves around the circumferential edge portion side of the wafer W and is adhered to the surface of the wafer W, as illustrated in  FIG. 11 . Thus, in order to minimize the number of particles P adhered on the surface of the wafer W, it is not preferable that the wafer W is directly mounted on the bottom surface of the recess  24 . 
     Therefore, as illustrated in  FIG. 12  and  FIG. 13 , it is conceivable that by providing the support  25  on the bottom surface of the recess  24 , the circumferential edge portion of the wafer W does not contact the bottom surface of the recess  24 , thereby reducing the number of particles adhered on the surface of the wafer W. In this case, when the process gas is supplied to the wafer W to apply the deposition process, a portion of the process gas supplied to the circumferential edge portion of the wafer W may pass between the circumferential edge portion of the wafer W and the inner wall surface of the recess  24  and move to the back surface side of the wafer W, and a film may be deposited on the back surface edge portion of the wafer W. The film thickness of the film deposited on the back surface edge portion of the wafer W can be greater than or equal to the film thickness of the film deposited on the surface of the wafer W, as illustrated in  FIG. 14 , for example. Then, if the film thickness of the film deposited on the back surface edge portion of the wafer W becomes thick, peeling of the film occurs, and a particle is generated. In  FIG. 14 , the horizontal axis indicates a radial direction position of the wafer W having a diameter r of 300 mm, and the vertical axis indicates the film thickness of the film deposited on the back surface of the wafer W when the film thickness of the film deposited on the surface of the wafer W is assumed to be 1. 
     In the embodiment, the annular groove  26  is formed between the inner wall surface of the recess  24  and the outer wall surface of the support  25 , and the purge gas supply  28  that supplies the purge gas to the groove  26  is provided. This allows the purge gas to be supplied to the groove  26  when the process gas is supplied to the surface of the susceptor  2  in a state where the wafer W is mounted on the support  25 . The purge gas supplied to the groove  26  prevents the process gas from contacting the back surface edge portion of the wafer W, the inner wall surface of the groove  26 , the bottom surface of the groove  26 , and the like. Therefore, the deposition of the film on the back surface edge portion of the wafer W, the inner wall surface of the groove  26 , the bottom surface of the groove  26 , and the like is suppressed. As described above, in the embodiment, the generation of particle P due to the rubbing of the circumferential edge portion of the wafer W and the surface of the susceptor  2  can be suppressed, and the deposition of the film on the back surface edge portion of the wafer W, the inner wall surface of the groove  26 , the bottom surface of the groove  26 , and the like can be suppressed. 
     [Modified Example of a Susceptor Configuration] 
     Another example of the susceptor of the deposition apparatus according to the embodiment will be described with reference to  FIG. 15 . A susceptor  2 A illustrated in  FIG. 15  differs from the susceptor  2  previously described in that the susceptor  2 A includes a porous portion  25   b  communicating from a front surface to a back surface in a region including the support  25 . Other configurations may be the same as in the configuration of the susceptor  2  previously described. 
     The porous portion  25   b  communicates from the front surface thereof to the back surface thereof in the region including the support  25 . The porous portion  25   b  is formed such that the diameter of the porous portion  25   b  is smaller than the diameter of the wafer W in a plan view for example. The porous portion  25   b  may be fixed to the susceptor  2  and may be removable from the susceptor  2 . If the porous portion  25   b  is removable from the susceptor  2 , the porous portion  25   b  may be configured to rotate with respect to the susceptor  2 . The porous portion  25   b  is formed of, for example, SiC, SiN, or the like that is the same material as the porous ring  27 . 
     As described, by providing the porous portion  25   b  in the region including the support  25 , the purge gas that enters between the upper surface of the support  25  and the back surface of the wafer W can be discharged below the susceptor  2 A through the porous portion  25   b  when the wafer W is mounted on the support  25 . This can suppress misalignment caused when the purge gas enters between the upper surface of the support  25  and the back surface of the wafer W mounted on the support  25 . 
     &lt;Deposition Method&gt; 
     An example of a deposition method according to the embodiment will be described with reference to  FIG. 16 . In the following, an example in which a silicon oxide film (SiO 2  film) is deposited on the wafer W in the deposition apparatus described above will be described. Here, the following description assumes that the susceptor  2  has already been heated by the heater  7  so that the wafer W mounted on the susceptor  2  is heated to a deposition temperature (for example, about 300° C.) 
     First, the wafer W is transferred into the processing chamber  1  (step S 1 ). In one embodiment, the gate valve G is opened, and while the susceptor  2  is intermittently rotated, five wafers W, for example, are mounted on the susceptor  2  through the transfer port  15  by the transfer arm (not illustrated). These wafers W are each mounted at the central position in the recess  24  and are therefore separated from (or are not contacted with) the inner wall surface of the recess  24  over the circumferential direction. At this time, the wafer W may be at the ambient temperature, or another heat treatment may be already applied to the wafer W, and when the wafer W is mounted on the susceptor  2 , the wafer W may be curved in a shape of a mountain based on the temperature variation in the plane of the wafer W, as illustrated in  FIG. 13 . 
     The gate valve G is then closed and the processing chamber  1  is vacuumed by the vacuum pump  64 , and the susceptor  2  rotates clockwise at 2 rpm to 240 rpm, for example. At this time, because the groove  26  is formed in the recess  24 , the circumferential edge portion of the wafer W is separated from the surface of the susceptor  2  and the surface of the support  25  even when the wafer W is curved in a mountain shape, so that the generation of particles caused by sliding the circumferential edge portion against the support  25  is suppressed. 
     The supply of the purge gas to the groove  26  is then started (step S 2 ). In one embodiment, the N 2  gas is discharged from the separation gas supply line  51  at a predetermined flow rate and the N 2  gas is supplied as the purge gas to the groove  26  through the purge gas supply  28 . 
     The supply of the process gas to the surface of the susceptor  2  is then started (step S 3 ). In one embodiment, the first process gas and the second process gas are respectively discharged from the first process gas nozzle  31  and the second process gas nozzle  32 , and the plasma generation gas is discharged from the plasma generation gas nozzle  34 . Additionally, the separation gas is discharged from the separation gas nozzles  41  and  42  at a predetermined flow rate, and the N 2  gas is discharged from the separation gas supply line  51  and the purge gas supply lines  72  and  72  at a predetermined flow rate. The inside of the processing chamber  1  is adjusted to a preset process pressure by the pressure adjuster  65 , and the high-frequency power is supplied to the plasma generator  80 . 
     At this time, each process gas supplied to the wafer W attempts to move around in the area on the back surface side of the wafer W through the clearance between the circumferential edge portion of the wafer W and the inner circumferential surface of the recess  24 . However, because the purge gas is supplied to the groove  26 , the movement of the process gas into the groove  26  is suppressed. This prevents the film from being deposited on the back surface edge portion of the wafer W, the inner wall surface of the groove  26 , the bottom surface of the groove  26 , and the like. 
     On the surface of the wafer W, the first process gas is adsorbed in the first process region P 1  by the rotation of the susceptor  2 , and the reaction between the first process gas adsorbed on the wafer W and the second process gas occurs in the second process region P 2 . This forms one or more molecular layers of silicon oxide film, which is a thin film component, on the surface of the wafer W to form a reaction product. At this time, the reaction product may contain impurities such as water (a hydroxyl group (OH)), organic matter, and the like, for example, due to the residue group contained in the first process gas. 
     On the lower side of the plasma generator  80 , the electric field among the electric field and magnetic field generated by the high-frequency power supplied from the high-frequency power supply  85  is reflected or absorbed (attenuated) by the Faraday shield  95 , thereby preventing (blocking) the arrival of the electric field into the processing chamber  1 . The magnetic field passes through the slit  97  of the Faraday shield  95  and arrives into the processing chamber  1  through the bottom surface of the housing  90 . Thus, the plasma generation gas discharged from the plasma generation gas nozzle  34  is activated by the magnetic field passing through the slit  97  to produce a plasma, such as an ion, a radical, or the like. 
     When the plasma (the active species) generated by the magnetic field contacts the surface of the wafer W, the modification treatment is performed on the reaction product. Specifically, by the plasma colliding with the surface of the wafer W, for example, the impurities are released from the reaction product, or the elements in the reaction product are rearranged to achieve densification. By continuing the rotation of the susceptor  2 , the adsorption of the first process gas to the surface of the wafer W, the reaction of the component of the first process gas adsorbed to the surface of the wafer W, and the plasma modification of the reaction product are performed in this order and over many times, the reaction products are laminated to form a thin film. 
     Additionally, because the N 2  gas is supplied between the first process region P 1  and the second process region P 2 , each gas is evacuated such that the first process gas, the second process gas, and the plasma generation gas do not mix with each other. Further, because the purge gas is supplied to the lower side of the susceptor  2 , the gas to be diffused to the lower side of the susceptor  2  is pushed back to the exhaust ports  61  and  62  by the purge gas. 
     After the deposition process is completed, the supply of the process gas to the surface of the susceptor  2  is stopped (step S 4 ). In one embodiment, the supply of the gas from each of the nozzles  31 ,  32 ,  34 ,  41 , and  42  is stopped. 
     After stopping the supply of the process gas to the surface of the susceptor  2 , the supply of the purge gas to the groove  26  is stopped (step S 5 ). In one embodiment, the supply of the N 2  gas from the purge gas supply  28  to the groove  26  is stopped. 
     Subsequently, the wafer W is transferred to the outside of the processing chamber (step S 6 ). In one embodiment, the rotation of the susceptor  2  is stopped. Then, the susceptor  2  is intermittently rotated to transfer the wafers W one by one through the transfer port  15 . When all wafers W are transferred, one run (one rotation of the deposition process) is completed. 
     The embodiments disclosed herein should be considered to be examples and not restrictive in all respects. Omission, substitution, and modification can be made to the above embodiments in various forms without departing from the scope of the appended claims and spirit thereof.