Patent Publication Number: US-2019194803-A1

Title: Susceptor cleaning method

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is based on and claims priority to Japanese Patent Application No. 2017-251954 filed on Dec. 27, 2017, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to a susceptor cleaning method that is implemented in a film forming apparatus. 
     2. Description of the Related Art 
     Methods for forming a thin film of silicon oxide (SiO 2 ) or the like using a film forming apparatus including a vacuum chamber that accommodates a susceptor, which is a rotating table for holding a plurality of substrates such as semiconductor wafers, are known. As a thin film is formed in a film forming process, deposits are formed on the surface of the susceptor, and particles are formed as a result of such deposits peeling off from the surface of the susceptor. In this respect, for example, a technique for performing a dry cleaning process is known that involves providing a cleaning gas nozzle in a film forming apparatus, and supplying a cleaning gas such as a fluorine-based gas from the cleaning gas nozzle to the susceptor after a film forming process has been performed a predetermined number of times (see, e.g., Japanese Unexamined Patent Publication No. 2015-142038). 
     When film forming processes are performed for forming an insulating film, a protective film, or the like on a substrate, a deposited film that adheres to the surface of the susceptor holding the substrate may not be sufficiently removed even when a cleaning gas such as a fluorine-based gas is supplied. For example, high-K films made of high-K materials, such as HfO, ZrO, AlO, and the like, cannot be easily removed with a cleaning gas. To remove such a deposited film, the susceptor has to be taken out of the film forming apparatus to perform a wet cleaning process that may involve immersing the susceptor in a cleaning solution, for example. 
     However, when a cleaning process using a cleaning solution is performed, although the deposited film may be removed, the susceptor may also be etched by the cleaning solution. As a result, the susceptor may be unsuitable for reuse and the service life of the susceptor may be shortened. 
     SUMMARY OF THE INVENTION 
     An aspect of the present invention is directed to providing a susceptor cleaning method that enables reuse of a susceptor by preventing etching of the susceptor while cleaning the susceptor. 
     According to one embodiment of the present invention, a susceptor cleaning method for cleaning a susceptor in a processing chamber is provided. The susceptor cleaning method includes a pre-coating film forming step of placing the susceptor in the processing chamber and forming a pre-coating film on a surface of the susceptor; a deposited film forming step of placing a substrate on the susceptor having the pre-coating film formed thereon and performing a film forming process in the course of which a deposited film is formed on the susceptor; a crack generating step of generating cracks in the deposited film; a pre-coating film removing step of supplying a pre-coating film removing gas into the processing chamber, causing the pre-coating film removing gas to reach the pre-coating film through the cracks, and removing the pre-coating film; and a deposited film removing step of removing the deposited film. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a longitudinal cross-sectional view of a film forming apparatus to be subjected to a susceptor cleaning method according to an embodiment of the present invention; 
         FIG. 2  is a schematic perspective view of an internal structure of the film forming apparatus of  FIG. 1 ; 
         FIG. 3  is a diagram showing a schematic plan view of the internal structure of the film forming apparatus of  FIG. 1  and an internal configuration of a control unit; 
         FIGS. 4A and 4B  are respectively example longitudinal cross-sectional views of a supply region and separation region of the film forming apparatus of  FIG. 1 ; 
         FIGS. 5A and 5B  are diagrams illustrating the size of the separation region; 
         FIG. 6  is another longitudinal cross-sectional view of the film forming apparatus of  FIG. 1 ; 
         FIG. 7  is another longitudinal cross-sectional view of the film forming apparatus of  FIG. 1 ; 
         FIG. 8  is a partial perspective view of the film forming apparatus of  FIG. 1 ; 
         FIG. 9  is a flowchart of a susceptor cleaning method according to an embodiment of the present invention; 
         FIG. 10  is a diagram schematically showing a process flow of a susceptor cleaning method according to a first embodiment; and 
         FIG. 11  is a diagram schematically showing a process flow of a susceptor cleaning method according to a second embodiment. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the following, embodiments for implementing a susceptor cleaning method according to the present invention will be described with reference to the accompanying drawings. First, a film forming apparatus to be subjected to a susceptor cleaning method according to an embodiment of the present invention will be described. Then, the susceptor cleaning method that is implemented in the film forming apparatus will be described. Note that in the following description and the drawings, elements having substantially the same features are given the same reference numerals and overlapping descriptions will be omitted. 
     [Film Forming Apparatus] 
     First, a film forming apparatus to be subjected to a susceptor cleaning method according to an embodiment of the present invention will be described. Although the susceptor cleaning method according to an embodiment of the present invention can be implemented in various film forming apparatuses, a film forming apparatus according to one embodiment that is suitable for implementing a susceptor cleaning method according to an embodiment of the present invention will be described below.  FIG. 1  is a longitudinal cross-sectional view of a film forming apparatus to be subjected to a susceptor cleaning method according to an embodiment of the present invention.  FIG. 2  is a schematic perspective view of an internal structure of the film forming apparatus of  FIG. 1 .  FIG. 3  is a diagram showing a schematic plan view of the internal structure of the film forming apparatus of  FIG. 1  and an internal configuration of a control unit.  FIGS. 4A and 4B  are longitudinal cross-sectional views of a supply region and a separation region in the film forming apparatus of  FIG. 1 .  FIGS. 5A and 5B  are diagrams illustrating the size of the separation region.  FIGS. 6 and 7  are other longitudinal cross-sectional views of the film forming apparatus.  FIG. 8  is a partial perspective view of the film forming apparatus of  FIG. 1 . 
     As shown in  FIG. 1  (cross-sectional view across line A-A of  FIG. 3 ) and  FIG. 2 , the film forming apparatus  1000  to be subjected to a susceptor cleaning method according to an embodiment of the present invention includes a processing chamber  100  and a control unit  200 . The processing chamber  100  includes a flat vacuum chamber  1  having a substantially circular plane shape and a susceptor  2  having a rotation center coinciding with the center of the vacuum chamber  1 . The control unit  200  controls the overall operation of the film forming apparatus  1000 . The vacuum chamber  1  is a processing chamber for accommodating a wafer W, as an example of a substrate, and performing a film forming process on the surface of the wafer W. The vacuum chamber  1  is composed of a chamber body  12  and a top plate  11  that can be detached from the chamber body  12 . The top plate  11  is attached to the chamber body  12  via a sealing member  13  such as an O-ring, for example, and in this way, the vacuum chamber  1  is hermetically sealed in an airtight manner. The top plate  11  and the chamber body  12  may be made of aluminum (Al), for example. Further, the susceptor  2  may be made of quartz, for example. 
     As shown in  FIG. 1 , the susceptor  2  is a disk-shaped rotating table having a circular opening at its center, and the susceptor  2  is held between a cylindrical core portion  21  that is arranged above and below the susceptor  2  near its center opening. The core portion  21  is fixed to an upper end of a rotating shaft  22  extending in the vertical direction. The rotating shaft  22  passes through a bottom portion  14  of the chamber body  12  and has a lower end attached to a driving unit  23  for rotating the rotating shaft  22  around a vertical axis. With such a configuration, the susceptor  2  can rotate around its center axis as the rotation center. The rotating shaft  22  and the driving unit  23  are accommodated in a cylindrical case body  20  that has an opening at an upper surface. The case body  20  is air-tightly attached to the bottom surface of the bottom portion  14  of the vacuum chamber  1  via a flange portion  20   a  provided on the upper surface of the case body  20 , and in this way, the internal atmosphere of the case body  20  is isolated from the external atmosphere. 
     As shown in  FIGS. 2 and 3 , a plurality of recessed portions  24  (five in the illustrated example) having circular shapes in planar view that can accommodate wafers W are formed at equiangular intervals on the upper surface of the susceptor  2 . Note, however, that in  FIG. 3 , only one recessed portion  24  has a wafer W accommodated therein. 
       FIG. 4A  is a longitudinal cross-sectional view of the susceptor  2  with the wafer W placed in the recessed portion  24 . As shown in  FIG. 4A , the recessed portion  24  has a diameter (e.g., 4 mm) that is slightly larger than the diameter of the wafer W. Further, the depth of the recessed portion  24  is substantially equal to the thickness of the wafer W. By arranging the depth of the recessed portion  24  to be substantially equal to the thickness of the wafer W, when the wafer W is placed in the recessed portion  24 , the surface of the wafer W will be at substantially the same height as the height of surface regions of the susceptor  2  other than the recessed portions  24  of the susceptor  2 . If the height difference between the wafer W and the surface regions of the susceptor  2  other than the recessed portions  24  of the susceptor  2  is relatively large, the height difference may cause turbulence in the gas flow and influence the film thickness uniformity of the wafer W. In order to reduce such an influence, the surface of the wafer W and the surface regions of the susceptor  2  other than the recessed portions  24  of the susceptor  2  are arranged to be substantially the same height. Note that the expression “substantially the same height” as used herein refers a height difference of about 5 mm or less, for example, but the height difference is preferably as close to zero as possible within the allowable range of machining accuracy. 
     Referring to  FIGS. 2 to 4B , two protruding portions  4  that are separated from one another are provided along the rotation direction of the susceptor  2  (e.g., arrow RD in  FIG. 3 ). Note that in  FIGS. 2 and 3 , illustration of the top plate  11  is omitted for the sake of illustrating the interior of the vacuum chamber  1 . As shown in  FIGS. 4A and 4B , the protruding portion  4  is provided on the lower surface of the top plate  11 . As can be appreciated from  FIG. 3 , the protruding portion  4  has a substantially fan-shaped planar shape with an apex portion of the substantially fan shape being positioned substantially at the center of the vacuum chamber  1  and a circular arc portion of the substantially fan shape being positioned along the inner peripheral wall of the chamber body  12 . Further, as shown in  FIG. 4A , a lower surface  44  (also referred to as “ceiling surface  44 ”) of the protruding portion  4  is arranged to be at height h 1  from the surface of the susceptor  2  or the surface of the wafer W placed in the recessed portion  24  of the susceptor  2 . 
     As shown in  FIGS. 3 to 4B , each protruding portion  4  has a groove portion  43  extending in the radial direction to divide the protruding portion  4  into two parts, and the groove portion  43  accommodates a separation gas nozzle  41  ( 42 ). Note that although the groove portion  43  is arranged to divide the protruding portion  4  into two equal parts in the present embodiment, the groove portion  43  may also be arranged to divide the protruding portion  4  so that the upstream side of the protruding portion  4  in the rotating direction of the susceptor  2  is larger than the downstream side, for example. As shown in  FIG. 3 , the separation gas nozzle  41  ( 42 ) is introduced into the vacuum chamber  1  from a peripheral wall portion of the chamber body  12 , and a gas introduction port  41   a  ( 42   a ) corresponding to a base end portion of the separation gas nozzle  41  ( 42 ) is arranged at an outer peripheral wall of the chamber body  12  to support the separation gas nozzle  41  ( 42 ). 
     The separation gas nozzle  41  ( 42 ) is connected to a separation gas supply source (not shown). Example gases that may be used as the separation gas include, nitrogen (N 2 ) gas, an inert gas, and the like, but the type of gas used is not particularly limited as long as it does not affect the film formation. In the present embodiment, N 2  gas is used as the separation gas. The separation gas nozzle  41  ( 42 ) also has discharge holes  40  ( FIGS. 4A and 4B ) for discharging N 2  gas toward the surface of the susceptor  2 . The discharge holes  40  are arranged at predetermined intervals along the length direction of the separation gas nozzle  41  ( 42 ). In the present embodiment, the discharge holes  40  have a diameter of about 0.5 mm and are arranged at intervals of about 10 mm along the length direction of the separation gas nozzle  41  ( 42 ). 
     With the above configuration, the separation gas nozzle  41  and the corresponding protruding portion  4  provide a separation region D 1  that defines a separation space H ( FIGS. 4A and 4B ). Similarly, the separation gas nozzle  42  and the corresponding protruding portion  4  provide a separation region D 2  that defines a separation space H. Also, a first region  48 A (first supply region) is formed downstream of the separation region D 1  in the rotating direction of the susceptor  2 . The first region  48 A is substantially surrounded by the peripheral edges of the separation regions D 1  and D 2 , the surface of the susceptor  2 , a lower surface  45  of the top plate  11  (hereinafter referred to as “ceiling surface  45 ”), and the inner peripheral wall of the chamber body  12 . Further, a second region  48 B (second supply region) is formed upstream of the separation region D 1  in the rotating direction of the susceptor  2 . The second region  48 B is substantially surrounded by the peripheral edges of the separation regions D 1  and D 2 , the surface of the susceptor  2 , the ceiling surface  45 , and the inner peripheral wall of the chamber body  12 . When N 2  gas is discharged from the separation gas nozzles  41  and  42  into the separation regions D 1  and D 2 , the pressures at the separation spaces H of the separation regions D 1  and D 2  become relatively high such that the N 2  gas flows from the separation spaces H toward the first region  48 A and the second region  48 B. That is, the protruding portions  4  in the separation regions D 1  and D 2  guide the N 2  gas supplied from the separation gas nozzles  41  and  42  toward the first region  48 A and the second region  48 B. 
     Also, as shown in  FIGS. 2 and 3 , a raw material gas nozzle  31  and a pre-coating gas nozzle  36  are introduced into the first region  48 A from the peripheral wall of the chamber body  12  to extend in the radial direction of the susceptor  2 , and an oxidizing gas nozzle  32  for supplying an oxidizing gas such as ozone is introduced into the second region  48 B from the peripheral wall of the chamber body  12  to extend in the radial direction of the susceptor  2 . Like the separation gas nozzles  41  and  42 , the raw material gas nozzle  31  and the oxidizing gas nozzle  32  are respectively supported by gas introduction ports  31   a  and  32   a  corresponding to base end portions of the raw material gas nozzle  31  and the oxidizing gas nozzle  32  arranged at the outer peripheral wall of the chamber body  12 . Note that the oxidizing gas is not limited to ozone, and for example, oxygen may also be used as the oxidizing gas. In the present embodiment, the raw material gas nozzle  31  and the pre-coating gas nozzle  36  are provided as separate gas nozzles under the premise that a high-K film (high dielectric film) is formed on the surface of the wafer W in a film forming process so that a reaction gas that is different from an organometallic gas or the like that is used for forming the high-K film is used as the pre-coating gas in the susceptor cleaning method according to the present embodiment. However, in other embodiments, for example, the pre-coating gas nozzle  36  may be eliminated and the raw material gas nozzle  31  may be configured to communicate with a raw material gas supply source and a pre-coating gas supply source via a switch valve, and the switch valve may be used to switch between supplying the raw material gas and supplying the pre-coating gas to the susceptor  2 . 
     The raw material gas nozzle  31  and the oxidizing gas nozzle  32  respectively have a plurality of discharge holes  33  and  34  for discharging the corresponding reaction gases toward the upper surface of the susceptor  2  (the surface having the recessed portions  24  for accommodating the wafers W) ( FIGS. 4A and 4B ). Similarly, the pre-coating gas nozzle  36  has a plurality of discharge holes (not shown) for discharging the pre-coating gas toward the upper surface of the susceptor  2 . In the present embodiment, the discharge holes  33  and  34  have a diameter of about 0.5 mm and are arranged at intervals of about 10 mm along the length direction of the raw material gas nozzle  31  and the oxidizing gas nozzle  32 . The discharge holes formed in the pre-coating gas nozzle  36  also have the same diameter and are arranged at the same intervals. 
     The raw material gas nozzle  31  is connected to a raw material gas supply source (not shown), the pre-coating gas nozzle  36  is connected to a pre-coating gas supply source (not shown), and the oxidizing gas nozzle  32  is connected to an ozone gas supply source (not shown). Although various gases may be used as the raw material gas, in the present embodiment, it is assumed that an organometallic gas or an organic metalloid gas is used, and the raw material gas to be used is selected according to the type of insulating film or protective film to be formed. For example, the organometallic gas may be an organometallic gas used for forming a high-K film. In this case, a gas such as tri(dimethylamino)cyclopentadienylzirconium (C 11 H 23 N 3 Zr) may be used, for example. In the following, an example case where an organometallic gas for forming a high-K film is used will be described. Also, in the following description, a region below the raw material gas nozzle  31  where the organometallic gas is adsorbed by the wafer W is referred to as “processing region P 1 ”, and a region below the oxidizing gas nozzle  32  where O 3  gas is to react with (oxidize) the organometallic gas adsorbed to the wafer W is referred to as “processing region P 2 ”. 
     Also, a cleaning gas nozzle  35  is provided in the first region  48 A. The cleaning gas nozzle  35  is not used during a film forming process but is used when performing a cleaning method for dry cleaning the interior of the vacuum chamber  1  including the susceptor  2  after the film forming process has been continually performed for some time and it has been determined that a deposited film formed by oxide films that have been deposited on the surface of the susceptor  2  and inside the vacuum chamber  1  should be removed. In one aspect of the susceptor cleaning method according to an embodiment the present invention, a pre-coating film is formed on the surface of the susceptor  2  before performing the film forming process, and after the film forming process, a fluorine-based gas such as ClF 3  gas is supplied from the cleaning gas nozzle  35 . Note that the susceptor cleaning method according to an embodiment the present invention will be described in detail below. 
     Referring back to  FIG. 4A , the ceiling surface  44  at the separation region D 1  is arranged to be a low ceiling surface (although not shown, a similarly low ceiling surface is provided at the separation region D 2 ). On the other hand, ceiling surfaces  45  at the first region  48 A and the second region  48 B are higher than the ceiling surface  44 . Therefore, the volumes of the first region  48 A and the second region  48 B are larger than the volumes of the separation spaces H in the separation regions D 1  and D 2 . As will be described below, the vacuum chamber  1  according to the present embodiment is provided with exhaust ports  61  and  62  for exhausting the first region  48 A and the second region  48 B, respectively. By providing these exhaust ports  61  and  62 , the pressures at the first region  48 A and the second region  48 B may be maintained at lower pressures as compared with the pressures at the separation spaces H of the separation regions D 1  and D 2 . In this case, because the pressures at the separation spaces H of the separation regions D 1  and D 2  are higher, the organometallic gas discharged from the raw material gas nozzle  31  in the first region  48 A cannot pass through the separation space H and reach the second region  48 B. Similarly, because the pressures at the separation spaces H of the separation regions D 1  and D 2  are higher, O 3  gas discharged from the oxidizing gas nozzle  32  in the second region  48 B cannot pass through the separation space H and reach the first region  48 A. In this way, the two reaction gases (i.e., the organometallic gas and the O 3  gas) can be separated by the separation regions D 1  and D 2  such that the reaction gases will hardly be mixed together in the gas phase inside the vacuum chamber  1 . 
     Although the height h 1  of the low ceiling surface  44  ( FIG. 4A ) measured from the upper surface of the susceptor  2  depends on the amount of N 2  gas supplied from the separation gas nozzle  41  ( 42 ), the height h 1  is suitably adjusted so that the pressures at the separation spaces H of the separation regions D 1  and D 2  will be higher than the pressures at the first region  48 A and the second region  48 B. For example, the height h 1  is preferably set to be in a range from 0.5 mm to 10 mm, and is more preferably set to be as low as possible. However, to avoid collision of the susceptor  2  against the ceiling surface  44  due to rotational blur of the susceptor  2 , the height h 1  is more preferably set to be in a range from about 3.5 mm to 6.5 mm within the above numerical range. Also, a height h 2  ( FIG. 4A ) of the lower edge of the separation gas nozzle  42  ( 41 ) accommodated in the groove portion  43  of the protruding portion  4  from the surface of the susceptor  2  is preferably adjusted to be in a range from 0.5 mm to 4 mm for the same reasons. 
     Also, referring to  FIGS. 5A and 5B , a length L of an arc corresponding to a path travelled by a wafer center WO across half the protruding portion  4  is preferably set to be about 1/10 to about 1/1 of the diameter of the wafer W, and more preferably at least about ⅙ of the diameter of the wafer W. By setting the length L of the arc to be within the above numerical range, the pressures at the separation spaces H of the separation regions D 1  and D 2  can be reliably maintained at desirably high pressures. 
     By arranging the separation regions D 1  and D 2  to have the above-described configuration, the organometallic gas and the O 3  gas can be more reliably separated even when the susceptor  2  rotates at a rotation speed about 240 rpm, for example. 
     Referring back to  FIGS. 1 to 3 , an annular protruding portion  5  surrounding the core portion  21  is provided on the ceiling surface  45  of the top plate  11 . The protruding portion  5  faces a region of the susceptor  2  at the outer side of the core portion  21 . In the present embodiment, as clearly shown in  FIG. 7 , a height h 15  of a space  50  defined by the lower surface of the protruding portion  5  from the susceptor  2  is slightly lower than the height h 1  of the space H. This is because the rotational blur around the center of the susceptor  2  is smaller than that at the periphery of the susceptor  2 . Specifically, the height h 15  may be set to be in a range from about 1.0 mm to 2.0 mm. Note that in other embodiments, the height h 15  and the height h 1  may be equal. Also, the protruding portion  5  and the protruding portion  4  may be integrally formed, or they may be separately formed. Note that  FIGS. 2 and 3  are views of the interior of the vacuum chamber  1  with the top plate  11  being omitted while leaving the protruding portion  4  in the vacuum chamber  1 . 
     As shown in  FIG. 6 , which is an enlarged partial view of about half of  FIG. 1 , a separation gas supply pipe  51  is connected to a center portion of the top plate  11  of the vacuum chamber  1 , and such a configuration allows N 2  gas to be supplied to a space  52  between the top plate  11  and the core portion  21 . By supplying the N 2  gas to the space  52 , the pressure in the narrow space  50  between the protruding portion  5  and the susceptor  2  can be maintained at a higher pressure than the pressures at the first region  48 A and the second region  48 B. Thus, the organometallic gas discharged from the raw material gas nozzle  31  in the first region  48 A can be prevented from reaching the second region  48 B via the high-pressure space  50 . Also, the O 3  gas discharged from the oxidizing gas nozzle  32  in the second region  48 B can be prevented from reaching the first region  48 A via the high-pressure space  50 . In this way, the two reaction gases can be separated by the space  50  and can be substantially prevented from mixing in the gas phase in the vacuum chamber  1 . That is, in the film forming apparatus according to the present embodiment, in order to separate the organometallic gas and the O 3  gas, a center region C that is maintained at a higher pressure than the pressures at first region  48 A and the second region  48 B is defined by the rotation center portion of the susceptor  2  and the vacuum chamber  1 . 
       FIG. 7  is a partial cross-sectional view of about half the film forming apparatus  1000  across line B-B of  FIG. 3 .  FIG. 7  shows the protruding portion  4  and the protruding portion  5  integrally formed with the protruding portion  4  at the separation region D 1  (D 2 ). As can be appreciated, the protruding portion  4  has a bent portion  46  bent into an L shape at its outer periphery. The bent portion  46  substantially fills the space (gap) between the susceptor  2  and the chamber body  12  and prevents the organometallic gas from the raw material gas nozzle  31  and the O 3  gas from the oxidizing gas nozzle  32  from passing through this gap and mixing with one another. The gap between the bent portion  46  and the chamber body  12  and the gap between the bent portion  46  and the susceptor  2  may be set up to be substantially equal to the height h 1  of the ceiling surface  44  of the protruding portion  4  from the susceptor  2 , for example. Also, by providing the bent portion  46 , the N 2  gas from the separation gas nozzles  41  and  42  ( FIG. 3 ) may be prevented from flowing toward the outer side of the susceptor  2 . In this way, the flow of the N 2  gas from the separation regions D 1  and D 2  to the first region  48 A and the second region  48 B may be promoted. Further, by providing a block member  71   b  below the bent portion  46 , the separation gas (N 2  gas) may be prevented from flowing toward a region below the susceptor  2 . 
     Note that the gap between the bent portion  46  and the susceptor  2  is preferably set up to have the above distance (about the height h 1  of the ceiling surface  44 ) in consideration of thermal expansion of the susceptor  2  that may occur when the susceptor  2  is heated by a heater unit as described below. 
     On the other hand, as shown in  FIG. 3 , at the first region  48 A and the second region  48 B, the inner peripheral wall of the chamber body  12  is recessed radially outward, and exhaust regions  6  are formed in the recessed regions. As shown in  FIGS. 3 and 6 , exhaust ports  61  and  62  may be arranged at the bottom of the exhaust regions  6 , for example. The exhaust ports  61  and  62  may be connected to a common vacuum pump  64  (see  FIG. 1 ) corresponding to a vacuum exhaust device via exhaust pipes  63 , for example. With such a configuration, gas may be evacuated mainly from the first region  48 A and the second region  48 B so that the pressures at the first region  48 A and the second region  48 B may be arranged be lower than the pressures at the separation spaces H of the separation regions D 1  and D 2  as described above. Note that although the exhaust regions  6  are provided at the regions where the inner peripheral wall of the chamber body  12  are recessed outward in  FIG. 3 , the exhaust regions do not necessarily have to have such configuration, and various other configurations are possible for providing the exhaust ports  61  and  62  at the bottom of the exhaust regions. 
     Also, in  FIG. 3 , the exhaust port  61  for the first region  48 A is positioned below the raw material gas nozzle  31  at the outer side (the exhaust region  6 ) of the susceptor  2 . In this way, the organometallic gas from the raw material gas nozzle  31  can flow along the upper surface of the susceptor  2  toward the exhaust port  61  in the longitudinal direction of the raw material gas nozzle  31 . 
     Referring back to  FIG. 1 , a pressure regulator  65  is provided in the exhaust pipe  63 , and in this way, the pressure in the vacuum chamber  1  can be adjusted. Note that in some embodiments, a plurality of pressure regulators  65  may be provided for the respective exhaust ports  61  and  62 . Also, note that the exhaust ports  61  and  62  are not limited to being provided at the bottom portion of the exhaust regions  6  (the bottom portion  14  of the vacuum chamber  1 ), but may alternatively be provided at peripheral wall portions of the chamber body  12  of the vacuum chamber  1 , for example. Further, the exhaust ports  61  and  62  may be provided on portions of the top plate  11  in the exhaust regions  6 , for example. However, when the exhaust ports  61  and  62  are provided on the top plate  11 , the gas in the vacuum chamber  1  will flow upward, and as a result, particles in the vacuum chamber  1  may be blown up to cause contamination of the wafer W. As such, the exhaust ports  61  and  62  are preferably provided at the bottom portions of the exhaust regions  6  as shown in  FIGS. 3 and 6 , or at peripheral wall portions of the chamber body  12 . Further, by providing the exhaust ports  61  and  62  at the bottom portions of the exhaust regions  6 , the exhaust pipe  63 , the pressure regulator  65 , and the vacuum pump  64  can be installed below the vacuum chamber  1  so that the footprint of the film forming apparatus  1000  can be reduced. 
     As shown in  FIGS. 1 and 6 to 8 , an annular heater unit  7  is provided in the space between the susceptor  2  and the bottom portion  14  of the chamber body  12 , and in this way, the susceptor  2  can be heated to a predetermined temperature, and if a wafer W is placed on the susceptor  2 , the wafer W may also be heated to the predetermined temperature via the susceptor  2 . Also, by providing a block member  71   a  surrounding the heater unit  7  below the susceptor  2  around the outer periphery of the susceptor  2 , the space where the heater unit  7  is placed can be separated from a region outside the heater unit  7 . Also, a slight gap is formed between the upper surface of the block member  71   a  and the lower surface of the susceptor  2  in order to prevent gas from entering the inner side of the block member  71   a . The region where the heater unit  7  is accommodated is connected to a plurality of purge gas supply pipes  73  for purging this region. The plurality of purge gas supply pipes  73  penetrate through the bottom portion of the chamber body  12  at predetermined angular intervals to be connected to the region where the heater unit  7  is accommodated. Note that a protective plate  7   a  for protecting the heater unit  7  is provided above the heater unit  7 . The protective plate  7   a  is supported by the block member  71   a  and a raised portion R (described below). In this way, even when the organometallic gas or the O 3  gas enters the space where the heater unit  7  is provided, the heater unit  7  can be protected from these reaction gases. The protective plate  7   a  is preferably made of quartz, for example. 
     As shown in  FIG. 6 , the bottom portion  14  of the chamber body  12  has a raised portion R arranged at the inner side of the annular heater unit  7 . The upper surface of the raised portion R is arranged close to the susceptor  2  and the core portion  21  such that there are only small gaps between the upper surface of the raised portion R and the lower surface of the susceptor  2  and between the upper surface of the raised portion R and the lower surface of the core portion  21 . Also, the bottom portion  14  has a center hole through which the rotating shaft  22  passes. The inner diameter of the center hole is slightly larger than the diameter of the rotating shaft  22  to thereby provide a gap that communicates with the interior of the case body  20  via a flange portion  20   a . A purge gas supply pipe  72  is connected to the upper portion of the flange portion  20   a.    
     With such a configuration, as shown in  FIG. 6 , N 2  gas from the purge gas supply pipe  72  may flow into the space below the susceptor  2  via the gap between the rotating shaft  22  and the center hole of the bottom portion  14 , the gap between the core portion  21  and the raised portion R of the bottom portion  14 , and the gap between the raised portion R of the bottom portion  14  and the lower surface of the susceptor  2 . Also, N 2  gas from the purge gas supply pipes  73  may flow into the space below the heater unit  7 . Then, the N 2  gas supplied from the purge gas supply pipes  72  and  73  flows into the exhaust port  61  through the gap between the block member  71   a  and the lower surface of the susceptor  2 . The N 2  gas flowing in this manner acts as a separation gas for preventing the organometallic gas (or O 3  gas) from circulating in the space below the susceptor  2  and mixing with the O 3  gas (or organometallic gas). 
     As shown in  FIGS. 2, 3 and 8 , a transfer port  15  is formed at a peripheral wall portion of the chamber body  12 . The wafer W can be transferred into the vacuum chamber  1  by a transfer arm  10  through the transfer port  15  or transferred out of the vacuum chamber  1  through the transfer port  15 . A gate valve (not shown) is provided at the transfer port  15 , and in this way, the transfer port  15  can be opened and closed. Three through holes (not shown) are formed at the bottom of the recessed portion  24  so that three lift pins  16  (see  FIG. 8 ) can move up and down through these through holes. The lift pins  16  support the rear surface of the wafer W to raise and lower the wafer W, and in this way, the wafer W can be passed to and from the transfer arm  10 . 
     Also, as shown in  FIG. 3 , the film forming apparatus  1000  according to the present embodiment includes a control unit  200  for controlling the operation of the entire apparatus. The control unit  200  includes a process controller  200   a  configured by a computer, a user interface unit  200   b , and a memory device  200   c , for example. The user interface unit  200   b  may include, for example, a display for displaying the operation status of the film forming apparatus and an input device, such as a keyboard or a touch panel, to be operated by an operator of the film forming apparatus to select a process recipe or a process manager to change parameters of the process recipe (not shown). 
     The control unit  200  also performs control for executing a susceptor cleaning method, which will be described below. 
     The memory device  200   c  stores a control program for causing the process controller  200   a  to execute various processes, process recipes, parameters for various processes, and the like. Also, the programs stored in the memory device include, for example, a program describing a set of steps for executing a susceptor cleaning method (described below). These control programs and process recipes are read and executed by the process controller  200   a  in accordance with an instruction from the user interface unit  200   b . Further, these programs may be stored in a computer readable storage medium  200   d  and installed in the memory device  200   c  via a corresponding input/output device (not shown). The computer-readable storage medium  200   d  may be a hard disk, a CD, a CD-R/RW, a DVD-R/RW, a flexible disk, a semiconductor memory, or the like. Further, the program may be downloaded to the memory device  200   c  via a communication line, for example. 
     Susceptor Cleaning Method According to First Embodiment 
     In the following, a susceptor cleaning method according to a first embodiment of the present invention will be described with reference to  FIGS. 9 and 10 .  FIG. 9  is a flowchart of the susceptor cleaning method according to the first embodiment, and  FIG. 10  is a diagram schematically illustrating the process flow of the susceptor cleaning method according to the first embodiment. 
     As shown in  FIGS. 9 and 10 , in the susceptor cleaning method according to the first embodiment, first, the susceptor  2  that does not have a wafer W placed thereon is set inside the processing chamber  100 , and a pre-coating film forming step of forming a pre-coating film  90  on the surface of the susceptor  2  is executed (step S 300 ). 
     In the pre-coating film forming step, a method substantially similar to a method of forming a silicon oxide film (SiO 2  film) on the surface of a wafer W is used to form a silicon oxide film on the surface of the susceptor  2  instead of the surface of a wafer W. 
     The internal atmosphere of the processing chamber  100  is set to a vacuum atmosphere, the heater unit  7  is operated to heat the susceptor  2 , and the heated susceptor  2  is rotated at a predetermined rotation speed. Then, N 2  gas as the separation gas is supplied from the separation gas nozzles  41  and  42  to the rotating susceptor  2 , a pre-coating gas is supplied from the pre-coating gas nozzle  36  to the rotating susceptor  2 , and ozone (O 3 ) gas as the oxidizing gas is supplied from the oxidizing gas nozzle  32  to the rotating susceptor  2 . These plural types of gases are supplied at the same time so that the reaction gases and the separation gas are simultaneously supplied to the susceptor  2 . 
     Note that a silicon-containing gas is used as the pre-coating gas. Specific examples of silicon-containing gases that may be used as the pre-coating gas include aminosilane-based gases, such as 3DMAS tris(dimethylamino)silane (3DMAS, Si(N(CH 3 ) 2 ) 3 H), tetrakis(dimethylamino)silane (4DMAS, Si(N(CH 3 ) 2 ) 4 ), tetrachlorosilane (TCS, siCl 4 ), dichlorosilane (DCS SiH 2 Cl 2 ), monosilane (SiH 4 ), hexachlorodisilane (HCD, Si 2 Cl 6 ), and the like. 
     As described above, a silicon-containing gas is used as the pre-coating gas, and a silicon-containing gas is also supplied from the raw material gas nozzle  31 . As such, in the present embodiment, the pre-coating gas nozzle  36  does not necessarily have to be used and the raw material gas nozzle  31  may be used to supply the pre-coating gas, for example. 
     That is, in a manner similar to the method of forming a silicon oxide film on the surface of a wafer W, ALD (Atomic Layer Deposition) is implemented to sequentially cause adsorption of the silicon-containing gas onto the surface of the susceptor  2  and oxidization of the silicon-containing gas adsorbed on the surface of the susceptor  2  multiple times while rotating the susceptor  2 . 
     By implementing such film forming method, a pre-coating film  90  made of a silicon oxide film may be formed on the surface of the susceptor  2 . For example, the pre-coating film  90  may be made of a silicon oxide film having a thickness of about 300 nm. Note that the oxidizing gas corresponding to a reaction gas is not limited to ozone gas and may also be oxygen gas, for example. 
     As described above, in the present embodiment, a high-K film is formed on the surface of the wafer W, but the pre-coating film formed in the pre-coating film forming step is a film having an etch rate (or etching selectivity) that is different from the etch rate (or etching selectivity) of the insulating film or protective film that is formed in the film forming process (a high-K film corresponding to an insulating film in the present embodiment). For example, a high-K film made of HfO, ZrO, AlO or the like and a SiO 2  film have substantially different etch rates; the etch rate of the SiO 2  film is substantially higher than the etch rate of the high-K film. 
     As described above, in the susceptor cleaning method according to the first embodiment, the pre-coating film formed in the pre-coating film forming step and the film formed on the wafer surface (and the deposited film formed on the surface of the susceptor  2 ) in the film forming process are respectively arranged to be different types of films having different etch rates. More specifically, the pre-coating film  90  that is formed on the surface of the susceptor  2  in the pre-coating film forming step is arranged to be a film having a higher etch rate than the etch rate of the film formed on the wafer surface in the film forming process. Thus, in the case where a high-K film is formed in the film forming process as in the present embodiment, a film that has a higher etch rate than the high-K film such as a silicon nitride film may also be formed as the pre-coating film, for example. 
     In the case of forming a pre-coating film made of a silicon nitride film, for example, the same silicon-containing gas as described above may be discharged from the pre-coating gas nozzle  36 , and the oxidizing gas nozzle  32  may be used as a nitriding gas nozzle for discharging a nitrogen-containing gas, such as NH 3  gas, as a reaction gas to thereby form a pre-coating film made of a silicon nitride film on the surface of the susceptor  2 . 
     After forming the pre-coating film  90  made of a silicon oxide film on the surface of the susceptor  2  in the processing chamber  100 , a wafer W as a substrate to be processed is loaded into the processing chamber  100  via the transfer port  15  of the processing chamber  100 , and the wafer W is placed on the susceptor  2 . Then, the internal atmosphere of the processing chamber  100  is set to a vacuum atmosphere, the heater unit  7  is operated to heat the susceptor  2  having the wafer W placed thereon, the susceptor  2  is rotated at a predetermined rotation speed, N 2  gas as the separation gas is supplied from the separation gas nozzles  41  and  42 , and an organometallic gas or the like as the raw material gas is supplied from the raw material gas nozzle  31 . 
     The organometallic gas that is used as the raw material gas may be a gas such as tri(dimethylamino)cyclopentadienylzirconium (C 11 H 23 N 3 Zr), for example. Other example gases that may be used as the raw material gas include various organometallic gases generated by vaporizing an organometallic compound containing a metal such as aluminum, hafnium, titanium, or the like, or a semimetal such as silane, for example. By supplying ozone gas from the oxidizing gas nozzle  32  and causing the organometallic gas to react with the oxidizing gas and undergo oxidization, a high-K film  95  is formed. Note that the high-K film  95  is formed under a relatively low temperature atmosphere of about 300° C. 
     Specifically, ALD (atomic layer deposition) is implemented to sequentially cause adsorption of the organometallic gas to the surfaces of the wafer W and the susceptor  2  and oxidation of the organometallic gas adsorbed to the surfaces of the wafer W and the susceptor  2  multiple times while rotating the susceptor  2 . By implementing such a film forming method, a high-K film  95  having a predetermined thickness is formed on the surface of the wafer W, and a deposited film  96  made of the high-K film corresponding to a cleaning target is formed on the surface regions of the susceptor  2  other than the recessed portions  24  accommodating the wafer W (step S 302 : deposited film forming step). 
     At the point where the high-K film  95  having a film thickness of about several nanometers (nm) has been formed on the surface of the wafer W, the wafer W is unloaded from the processing chamber  100 , a different wafer W is loaded into the processing chamber  100  and placed on the susceptor  2 . Then, the same film forming process as described above is carried out to form a high-K film  95  having a thickness of about several nanometers (nm) on the surface of the wafer W in the same manner, and after the high-K film  95  is formed, the wafer W is unloaded from the processing chamber  100 . By performing the above film forming process a predetermined number of times, the deposited film  96  made of the high-K film corresponding to the cleaning target accumulates on regions other than the recessed portions  24  of the susceptor  2 . For example, a cleaning process for removing the deposited film  96  from the susceptor  2  may be executed when the film thickness of the deposited film  96  reaches approximately 20 μm. 
     In the cleaning process, a crack generation step for generating cracks in the deposited film  96  is executed (step S 304 ). Specifically, the processing chamber  100  that has been set to a vacuum atmosphere during the film forming process is opened to the atmosphere to be placed under an atmospheric pressure atmosphere, and the temperature of the processing chamber  100  that was raised to a high temperature by the heater unit  7  is set to room temperature. In this way, a large number of cracks  97  penetrating through the deposited film  96  from its outer surface to the inner surface facing the susceptor  2  are automatically generated in the deposited film  96  made of the high-K film. 
     After the cracks  97  penetrating through the deposited film  96  have been generated, the susceptor  2  is rotated once again, N 2  gas as the separation gas is supplied from the separation gas nozzles  41  and  42  into the processing chamber  100 , and a fluorine-based gas, such as ClF 3 , as a cleaning gas for removing the pre-coating film is supplied from the cleaning gas nozzle  35  to the susceptor  2 . The fluorine-based gas supplied to the susceptor  2  permeates through the deposited film  96  through the cracks  97  and reaches the susceptor  2 . Although the pre-coating film  90  is formed on the surface of the susceptor  2 , because the pre-coating film  90  has a higher etch rate in the fluorine-based gas as compared with the etch rate of the deposited film  96 , the pre-coating film  90  is etched by the fluorine-based gas, gasified, and dissipated (step S 306 : pre-coating film removing step). 
     In the pre-coating film removing step, while the pre-coating film  90  is etched by the fluorine-based gas, the susceptor  2 , which is made of quartz or the like, is effectively prevented from being etched by the fluorine-based gas. 
     After the pre-coating film  90  is removed by the pre-coating film removing step, the deposited film removing step is executed (step S 308 ). The deposited film removing step refers to a step of completely removing the deposited film  96  from the surface of the susceptor  2 . However, in practice, the deposited film  96  may be lifted off from the susceptor  2  as a result of the dissipation of the pre-coating film  90 . Accordingly, in the case where removal of the deposited film  96  can be deemed completed after the deposited film  96  is lifted off from the surface of the susceptor  2 , the deposited film removing step may be automatically terminated upon completion of the pre-coating film removing step. In this case, the susceptor cleaning method according to the first embodiment ends when the pre-coating film removing step ends. Note that the above susceptor cleaning method is based on the dry cleaning method. 
     However, when the deposited film  96  is lifted off, residual strands of the deposited film  96  formed by the generation of the cracks  97  may remain on the surface of the susceptor  2 . When the deposited film  96  is still present, the surface of the susceptor  2  cannot be deemed to have been completely cleaned. Accordingly, in the deposited film removing step, the interior of the processing chamber  100  is opened to the atmosphere, and a vacuum cleaner  98  is used to remove the deposited film  96  through vacuum suction. 
     When it can be determined that the deposited film  96  has been completely removed as a result of using the vacuum cleaner  98  to remove the deposited film  96  by vacuum suction, the deposited film removing step ends when the vacuum suction removal process is completed, and the susceptor cleaning method according to the first embodiment ends at this point. 
     On the other hand, at the time the vacuum suction removal process using the vacuum cleaner  98  has been completed, traces of the deposited film  96  may still remain adhered to the surface of the susceptor  2  without being lifted off from the susceptor  2 . When the susceptor  2  having such traces of the deposited film  96  remaining thereon is reused, the traces of the deposited film  96  may cause the generation of particles. Thus, as a finishing process of the deposited film removing step, a wet cleaning process that involves removing the susceptor  2  from the processing chamber  100  and immersing the susceptor  2  with a cleaning solution  99  may be executed. 
     In the case where the deposited film  96  is made of a high-K film as described above, for example, a hydrofluoric acid solution (HF), a dilute hydrofluoric acid solution (DHF), a buffered hydrofluoric acid solution (BHF, NH 4 /HF/H 2 O), and the like may be used as the cleaning solution  99 , and in this way, the high-K film can be dissolved in these cleaning solutions  99  and effectively removed from the surface of the susceptor  2 . 
     Note that because most of the deposited film  96  is lifted off from the surface of the susceptor  2  in the previous processes of the deposited film removing step, the processing time of the wet cleaning process may be relatively short. In this way, the susceptor  2  may be prevented from being etched by DHF or the like in the wet cleaning process. Note that when there is not much residue of the deposited film  96  to be removed in the wet cleaning process, pure water may be used in the wet cleaning process, for example. 
     As described above, in the susceptor cleaning method according to the first embodiment, the susceptor  2  made of quartz or the like may be prevented from being etched by a fluorine-based gas or being etched by a cleaning solution such as DHF. In this way, the number of times the susceptor  2  can be reused may be increased and the service life of the susceptor  2  may be prolonged while periodically cleaning (maintaining) the susceptor  2 . 
     Susceptor Cleaning Method According to Second Embodiment 
     In the following, a susceptor cleaning method according to a second embodiment of the present invention will be described with reference to  FIGS. 9 and 11 .  FIG. 11  is a diagram schematically illustrating the process flow of the susceptor cleaning method according to the second embodiment. 
     The differences between the susceptor cleaning method according to the first embodiment and the susceptor cleaning method according to the second embodiment lie in the type of film that is formed as the pre-coating film in the pre-coating film forming step and the type of reaction gas that is used in the pre-coating film removing step due to the difference in the film type of the pre-coating film. In the susceptor cleaning method according to the first embodiment, the pre-coating film is etched based on the differences in the etch rates of the pre-coating film and the deposited film (film formed by film forming process). In susceptor cleaning method according to the second embodiment, the pre-coating film is oxidized and removed by ashing. Note that in the following description of the susceptor cleaning method according to the second embodiment, explanations of process steps that are substantially the same as those implemented in the susceptor cleaning method according to the first embodiment will be omitted. 
     In the pre-coating film forming step according to the second embodiment, after placing the susceptor  2  in the processing chamber  100 , the susceptor  2  is heated and rotated, N 2  gas as the separation gas is supplied from the separation gas nozzles  41  and  42 , and a carbon-based gas as the pre-coating gas is supplied from the pre-coating gas nozzle  36 . Because the susceptor  2  is heated and the interior of the processing chamber  100  is in a high-temperature atmosphere, chemical vapor deposition (CVD) of the carbon-based gas occurs and a pre-coating film  90 A made of a CVD-carbon-based film is formed on the surface of the susceptor  2 . Note that although the illustrated example shows a method of forming a CVD film by thermal energy, in other examples, a radio frequency power source may be provided in the processing chamber  100  and a method of forming a plasma CVD film by plasma energy may be implemented to form the pre-coating film. 
     In the deposited film forming step, a high-K film  95  is formed on a wafer W and a deposited film  96  is formed on the surface of the susceptor  2 . At the stage where the deposited film  96  that has been formed on the surface of the susceptor  2  reaches a predetermined thickness, the crack generating step is executed to generate cracks  97  in the deposited film  96 . 
     In the pre-coating film removing step of the susceptor cleaning method according to the present embodiment, an oxidizing gas, such as O 3  gas, as a pre-coating film removing gas is supplied from the oxidizing gas nozzle  32  to the susceptor  2 . 
     The oxidizing gas that penetrates through the deposited film  96  through the cracks  97  and reaches the pre-coating film  90 A made of the CVD-carbon-based film promotes ashing of the CVD-carbon-based film. Note that oxygen gas may also be used as the pre-coating film removing gas, and in the case where oxygen gas is used, the CVD-carbon-based film may be subjected to plasma ashing using oxygen gas that has been subjected to a plasma process. 
     By causing ashing of the pre-coating film  90 A made of the CVD-carbon-based film using the oxidizing gas, the deposited film  96  may be lifted off from the surface of the susceptor  2 . As with the susceptor cleaning method according to the first embodiment, after the deposited film  96  has been lifted off from the surface of the susceptor  2 , residues of the deposited film  96  remaining on the susceptor  2  may be removed by vacuum suction as necessary, and the susceptor  2  may further be subjected to a wet cleaning process using a cleaning solution as necessary. 
     The susceptor cleaning method according to the second embodiment can similarly prevent the susceptor  2  made of quartz or the like from being etched by the fluorine-based gas or being etched by a cleaning solution such as DHF. In this way, the number of times the susceptor  2  is reused may be increased and the service life of the susceptor  2  may be prolonged while periodically cleaning (maintaining) the susceptor  2 . 
     Susceptor Cleaning Method According to Other Embodiment 
     Although not shown in the drawings, a susceptor cleaning method according to still another embodiment will be described below. 
     First, in the cleaning method according to the first and second embodiments, the processing chamber  100  that is used in the film forming process is used to form the pre-coating film on the surface of the susceptor  2 . However, in a susceptor cleaning method according to another embodiment, a processing chamber that is different from the processing chamber  100  that is used in the film forming process may be used to form a pre-coating film on the surface of the susceptor  2 . After the pre-coating film has been formed on the susceptor  2  in a different processing chamber, the susceptor  2  having the pre-coating film formed thereon may be accommodated in the processing chamber  100  that is used in the film forming process, and the subsequent process steps including the deposited film forming step, the crack generating step and the like as described above may executed in the processing chamber  100 . 
     Although the present invention has been described above with respect to illustrative embodiments, the present invention is not limited to these embodiments and various variations and modifications may be made without departing from the scope of the present invention. For example, features and configurations described in connection with the above-described embodiments of the present invention may be combined to the extent practicable, and the present invention is not limited to the features and configurations of the above-described embodiments.