Patent Publication Number: US-2013247816-A1

Title: Film-forming apparatus for the formation of silicon carbide and film-forming method for the formation of silicon carbide

Description:
The entire disclosure of the Japanese Patent Applications No. 2012-066300, filed on Mar. 22, 2012 and No. 2013-042248, filed on Mar. 4, 2013 including specification, claims, drawings, and summary, on which the Convention priority of the present application is based, are incorporated herein in its entirety. 
     FIELD OF THE INVENTION 
     The present invention relates to a film-forming apparatus for the formation of silicon carbide and a film-forming method for the formation of silicon carbide. 
     BACKGROUND 
     Epitaxial growth technique is conventionally used to produce a semiconductor device such as a power device (e.g., IGBT (Insulated Gate Bipolar Transistor)) requiring a relatively thick crystalline film. 
     In the case of vapor-phase epitaxy used in an epitaxial growth technique, a substrate is placed inside a film-forming chamber maintained at an atmospheric pressure or a reduced pressure, and a reaction gas is supplied into the film-forming chamber while the substrate is heated. As a result of this process, a pyrolytic reaction or a hydrogen reduction reaction of the reaction gas occurs on the surface of the substrate so that an epitaxial film is formed on the substrate. The gas generated by the reaction, as well as the gas not used, is exhausted through the outer portion of the chamber. After the epitaxial film is formed on the substrate, the substrate is then carried out from the chamber. Another substrate is then placed into the chamber, and then an epitaxial film will be formed on that substrate. 
     In order to produce a thick epitaxial film in high yield, a fresh reaction gas needs to be continuously brought into contact with the surface of a uniformly heated substrate to increase a film-forming rate. Therefore, in the case of a conventional film-forming apparatus, a film is epitaxially grown on a wafer while the wafer is rotated at a high speed (see, for example, Japanese Patent Application Laid-Open No. 2009-170676). 
     In a conventional film-forming apparatus, a rotating unit is positioned in a film-forming chamber, and a substrate is positioned on a ring-shaped holder arranged on the top-surface of the rotating unit. A resistive heater functioning as an inner heater is positioned below the holder. 
     When the film forming process performed on the substrate has been completed, the substrate is removed from the film-forming chamber. Since the temperature within the film-forming chamber immediately after the film forming process is very high, it is necessary to remove the substrate after the temperature within the film-forming chamber has lowered. 
     After the substrate has been removed from the film-forming chamber, a substrate that will be next subjected to the film forming process is transferred into the film-forming chamber. The temperature within the film-forming chamber is increased up to a temperature required for the film forming process. However, it takes time in order to raise the temperature that was lowered, up to the film-forming temperature. Therefore, the time required from completion of the film forming process to the next film forming process results in a lowering a throughput in the manufacture process of semiconductor devices. 
     For example, a substrate is heated to approximately 1200° C. in film formation of a Si (silicon) vapor deposition film. After completion of the film formation, the heater is turned off to lower the temperature within the film-forming chamber to a predetermined temperature and the substrate is then removed from the film-forming chamber. Next, another substrate is transferred into the film-forming chamber and the heater is turned on. However, since the temperature within the film-forming chamber is considerably low in this stage, a long time is required for the temperature to rise to 1200° C. 
     Further, in recent years, attention has been given to SiC (silicon carbide) as a semiconductor material to be used in high-voltage power semiconductor devices, the film-forming temperature is required to be 1500° C. or higher. Therefore, after the temperature within the film-forming chamber has been lowered in order to remove the substrate, a time required to raise the temperature to the film-forming temperature becomes longer than that in the case of the Si vapor deposition film. Therefore, lowering of the throughput is further increased. 
     The present invention has been made to address the above issues. That is, an object of the present invention is to provide a film-forming apparatus and a film-forming method for the formation of silicon carbide in that the time elapsing from completion of the film forming process to performance of the next film forming process can be suppressed to a minimum, thus resulting in an improvement in throughput. 
     Other challenges and advantages of the present invention are apparent from the following description. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present invention, a film-forming apparatus for the formation of silicon carbide comprising, a film-forming chamber to which a reaction gas is supplied, where a film forming process is performed, a temperature-measuring unit which measures a temperature within the film-forming chamber, a plurality of heating units which are arranged inside the film-forming chamber, an output control unit which controls respective outputs of the plurality of heating units independently, a substrate-transferring unit which transfers a substrate to which a film forming process of silicon carbide is performed into, and out of the chamber, and a susceptor on which the substrate is placed, the susceptor being disposed within the film-forming chamber, wherein the output control unit turns off or lowers at least one output of the plurality of heating units when the film forming process to the substrate is completed, when the temperature measured by the temperature-measuring unit reaches a temperature at which the substrate-transferring unit is operable within the film-forming chamber, then at least one output of the plurality of heating units which has been turned off or lowered, is turned on or raised, and the substrate to which the film forming process has been performed is transferred out of the film-forming chamber by the substrate-transferring unit. 
     According to another aspect of the present invention, a film-forming method for the formation of silicon carbide, wherein, a reaction gas is supplied into a film-forming chamber and a film of silicon carbide is formed on a substrate while the substrate is being heated by a plurality of heating units; after the formation of a silicon carbide on a substrate, at least one output of the plurality of heating units is turned off or lowered, when the temperature within the film-forming chamber reaches T 1  or lower, at least one output of the plurality of heating units which has been turned off or lowered, is turned on or raised, and a substrate-transferring unit then enters the film-forming chamber, when the temperature within the film-forming chamber reaches T 2  (incidentally, T 1 &gt;T 2 ) or lower, the substrate is transferred out of the film-forming chamber by the substrate-transferring unit, and another substrate is then transferred into the film-forming chamber by the substrate-transferring unit and the outputs of the remaining heating units are turned on or raised. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic cross-section of a film-forming apparatus according to the present embodiment. 
         FIG. 2  is a cross-sectional view of a chamber in the film forming apparatus, as another example according to the first embodiment. 
         FIG. 3  is a cross-sectional view of a chamber in the film forming apparatus, as another example according to the present embodiment. 
         FIG. 4  is a plane view showing the construction of a film forming apparatus  100 . 
         FIG. 5  is a diagram showing the relationship among control systems in the film-forming apparatus  101 . 
         FIG. 6  is a graph illustratively showing a temporal change of the measurement result obtained by the temperature-measuring unit  400 . 
         FIG. 7  is a graph showing a relationship between the outputs of the respective heaters and time. 
         FIG. 8  is a flowchart of a film forming method according to the second embodiment. 
         FIG. 9  is a graph of a comparative example of this embodiment, and it illustratively shows the temporal change of the measurement result obtained by the temperature-measuring unit  400 . 
         FIG. 10  is a plane view showing an arrangement of the sensor of the film-forming apparatus in  FIG. 1 . 
         FIG. 11  shows a relationship between the control systems of a film forming apparatus in  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiment 1 
       FIG. 1  is a schematic cross section of a film-forming apparatus according to the present embodiment. For example, the control system is substantially same as a film-forming apparatus  101  of  FIG. 2  explained using  FIG. 5 ; therefore the control system is not shown in  FIG. 1 . The scale of this diagram is different from an actual apparatus so that each component is visible clearly. 
     As shown in  FIG. 1 , the film-forming apparatus  100  includes a chamber  1  as a film-forming chamber, a hollow tubular liner  2  that covers and protects the inner wall of the chamber  1 , flow paths  3  through which cooling water flows to cool the chamber  1 , a supply portion  5  for introducing a reaction gas  4 , a discharge portion  6  that discharges the reaction gas  4  subjected to reaction, a susceptor  8  that supports the substrate  7  placed thereon, a flange portion  10  that connects upper and lower sections of the chamber  1  with each other, a gasket  11  that seals the flange portion  10 , a flange portion  13  that connects the gas discharge portion  6  to a pipe  12 , the pipe  12  is used for discharging the gas out of the chamber  1 , and a gasket  14  that seals the flange portion  13 . These gaskets  11  and  14  are preferably made of fluorine-containing rubber, which have an allowable temperature limit of approximately 300° C. 
     The liner  2  is provided to separate the inner wall  1   a  of the chamber  1  from the space A in which the film will be formed on the substrate  7 . The inner wall  1   a  of the chamber  1  is made of stainless steel. Therefore, the liner  2  has the effect of preventing erosion of the inner wall  1   a  of the chamber  1  by the reaction gas  4 . 
     The liner  2  is made of a material having very high heat resistance, as the film-forming process is performed under high temperature. For example, a SiC member or a member formed by coating carbon with SiC or TaC can be used. 
     In the present embodiment, the liner  2  is separated into a body portion  2   a  and a top portion  2   b  for ease of explanation. The top portion  2   b  is a unit in which the susceptor  8  is placed. The top portion  2   b  has a smaller inner diameter than the body portion  2   a . The liner  2  consists of the body portion  2   a  and the top portion  2   b  combined into one whole portion. The top portion  2   b  is positioned above the body portion  2   a.    
     A shower plate  15  is fitted into the upper opening of the top portion  2   b . The shower plate  15  functions as a flow-straightening vane for uniformly supplying the reaction gas  4  to the surface of the substrate  7 . The shower plate  15  has a plurality of through-holes  15   a  thereon. When the reaction gas  4  is supplied from the supply portion  5  into the film-forming chamber  1 , the reaction gas  4  flows downward to the substrate  7  through the through-holes  15   a . It is preferable that the reaction gas  4  be efficiently focused on the surface of the substrate  7  without wastage. Accordingly, the inner diameter of the top portion  2   b  is designed so as to be smaller than the body portion  2   a . Specifically the inner diameter of the top portion  2   b  is determined in consideration of the position of the through-holes  15   a  and the size of the substrate  7 . 
     The susceptor  8  for supporting the substrate  7  is a ring-shaped susceptor, and is positioned in the film-forming chamber  1 , specifically, in the body portion  2   a  of the liner  2 . In order to form a SiC epitaxial film, the temperature of the substrate  7  needs to be 1500° C. or higher. For this reason, the susceptor  8  needs to be made of highly heat-resistant material. A susceptor  8  obtained by coating the surface of isotropic graphite with SiC or TaC by CVD (Chemical Vapor Deposition) can be used (as one example). The shape of the susceptor  8  is not particularly limited as long as the substrate  7  can be placed on the susceptor  8 , and may be designed as required. For example, the susceptor may be a disk shape. 
     The rotating shaft  16  and the rotating cylinder  17  positioned on the top of the rotating shaft  16  are placed in the body portion  2   a  of the liner  2 . The susceptor  8  is attached to the rotating cylinder  17 . The rotating shaft  16  is rotated, and then the susceptor  8  is rotated via the rotating cylinder  17 . When the film-forming process is performed, the substrate  7  is placed on the susceptor  8 , and the substrate  7  is rotated along with the susceptor  8 . 
     A pin (not shown), capable of moving in an up and down direction is provided in the rotating shaft  16 . The end of the pin extends to a substrate rising means (not shown) provided at the bottom of the rotating shaft  16 . The pin can be moved up and down by the substrate rising means. The pin is used when the substrate  7  is transferred into and out of the chamber  1 . The pin supports the bottom of the substrate  7 , and then rises to move the substrate  101  away from the susceptor  8 . The substrate  7  is then positioned above the rotating portion  104  separate from the susceptor  8  by the pin, allowing a transfer robot  332  to remove the substrate  7 . The transfer robot  332  corresponds to a substrate transfer unit in the present invention. 
     The reaction gas  4  passing through the shower plate  15 , flows downward toward the substrate  7  via the top portion  2   b . The reaction gas  4  is attracted by the substrate  7  while the substrate  7  is rotating, and the reaction gas  4  forms a so-called vertical flow in a region extending from the shower plate  15  to the surface of the substrate  7 . When the reaction gas  4  reaches the substrate  7 , the reaction gas  4  flows without turbulence as a substantially laminar flow in a horizontal direction along the upper surface of the substrate  7 . As described above, the reaction gas  4  comes into contact with the surface of the substrate  7 , and a vapor-phase growth film is formed on the surface of the substrate  7  by a pyrolytic reaction or a hydrogen reduction of the reaction gas  4  on the surface of the substrate  7 . Furthermore, the film-forming apparatus  100  is configured so that the gap between the periphery of the substrate  7  and the liner  2  is minimized to allow the reaction gas  4  to flow more uniformly onto the surface of the substrate  7 . 
     The reaction gas  4  not used for the vapor-phase growth reaction and the gas produced by the vapor-phase growth reaction, is exhausted from the discharge portion  6  provided at the bottom of the chamber  1 . 
     According to the above-mentioned apparatus, the vapor-phase growth reaction is performed while the substrate  7  is rotated. The reaction gas  4  can be efficiently supplied over the whole surface of the substrate  7 , and then an epitaxial film having high thickness uniformity is formed. It is noted that the film-forming rate can be increased when reaction gas  4  is continuously supplied to the surface of the substrate  7 . 
     In the present embodiment a heating unit, wherein the heating unit consists of a main heater  9  and sub-heater  18 , heats the substrate  7 . In the present invention the main heater corresponds to the first heater of the present invention, and the sub-heater corresponds to the second heater in the present invention, both of these heaters are resistive heaters. The main heater  9  is provided near the substrate  7 , and directly heats the substrate  7 . The sub-heater  18  is provided above the main heater  9 . The substrate is positioned between the main heater and sub-heater. The sub-heater  18  assists the main heater  9  and heats the substrate  7  in combination the main heater  9 . 
     The main heater  9  is provided in the rotating cylinder  17  and heats the substrate from below. The main heater  9  includes an in-heater  9   a , which is disk shaped, and an out-heater  9   b , which is provided above the in-heater  9   a  and is a disk-shape. This is based upon the fact that the temperature is liable to be cooled due to a combination of the fast flow rate of the reaction gas  4  at the outer peripheral portion of the substrate  7 , and the wall of the chamber  1  which has been cooled by cooling water. By providing the in-heater  9   a  and the out-heater  9   b , lowering of the temperature at the outer peripheral portion of the substrate  7  is suppressed so that an even temperature distribution can be obtained. 
     The in-heater  9   a  and the out-heater  9   b  are arranged such that their centers are positioned on the same vertical line as the center of the substrate  7 . By adopting such an arrangement, the in-heater  9   a  heats the whole substrate  7  while the out-heater  9   b  heats an outer peripheral portion of the substrate  7 . Further, by arranging the out-heater  9   b  above the in-heater  9   a , the outer peripheral portion of the substrate  7  liable to lower in temperature is effectively heated so that the temperature distribution of the substrate  7  can be made even. Incidentally, it is preferred that the temperature of the out-heater  9   b  be set higher than that of the in-heater  9   a . Thereby, a uniform temperature across the substrate can be attained. 
     The in-heater  9   a  and the out-heater  9   b  are supported by an electrically conductive arm-like busbar  20 . The busbar  20  is made of, for example, a SiC-coated carbon material. The busbar  20  is supported by the heater base  21  made of quartz, at the opposite side of the in-heater  9   a  and the out-heater  9   b . The busbar  20  is connected to connecting portions  22 . The connecting portions  22  are formed of a metal such as molybdenum. Electricity can be conducted from rod electrodes  23  through the busbar  20  to the in-heater  9   a  and the out-heater  9   b . Specifically, electricity is conducted from the rod electrodes  23  to a heat source of the in-heater  9   a  and the out-heater  9   b , and then the temperature of the heat source will increase. 
     The sub-heater  18  is provided around the top portion  2   b  of the liner  2 , and is supported by the heater-supporting portion  19 ; the heater is connected with a supporting portion by a connecting portion (not shown). Furthermore, the heater-supporting portion is connected through the sidewall of the chamber  1  to an outer electrode. Therefore, electricity can be conducted from the outer electrode to the heater. 
     The substrate  7  is heated from the top surface by the sub-heater  18 . The back surface of the substrate  7  is heated is also heated from the back surface by main-heater  9 . That is, the substrate  7  is heated from both sides by the main-heater  9  and the first sub-heater  18   a . As these heaters are the resistive heaters, the temperature of the substrate  7  can be precisely controlled. 
     The temperature of the chamber  1  is measured by radiation thermometers  24   a  and  24   b . In  FIG. 1 , the temperature at the center of the substrate  7  is measured by the radiation thermometer  24   a . The temperature of the outer position of the substrate  7  is measured by the radiation thermometer  24   b . Incidentally, by changing the positions of the radiation thermometers  24   a  and  24   b , the surface temperature of a member other than the substrate  7 , for example, the susceptor  8  can be measured. Since the substrate  7  is placed on the susceptor  8 , it can be thought the substrate  7  and the susceptor  8  are almost on the same position. Therefore, except for the film-forming time where a slight temperature difference is problematic, the temperature of the substrate  7  and the temperature of the susceptor  8  can be equated with each other. 
     The radiation thermometers  24   a  and  24   b  are positioned at the upper position of the film-forming chamber  1  as shown in  FIG. 1 . It is preferred that the top of the chamber and the shower plate  15  be formed of quartz, because the use of quartz prevents the temperature measurement of the radiation thermometers  24   a  and  24   b  from being affected. 
     After temperature measurement the data is sent to a heater output control unit (mentioned below) and then fed back to an output control unit of the in-heater  9   a , the out-heater  9   b , and the sub-heater  18 . Incidentally, when the sub-heater  18  is composed of, for example, a first sub-heater, a second sub-heater, a third sub-heater, a fourth sub-heater, and a fifth sub-heater like another example described later, the measurement temperature data is fed back for respective output controls of the first sub-heater, the second sub-heater, the third sub-heater, the fourth sub-heater, and the fifth sub-heater. 
     Further, in this embodiment, it is possible that the sub-heater is composed of a plurality of resistive-heating type heaters. For example, the sub-heater can be divided to two or more sub-heaters, for example, five sub-heaters, along a vertical direction upward, that is, from the side close to the substrate  7  upward. 
       FIG. 2  is a cross-sectional view of a chamber in the film forming apparatus, as another example according to the present embodiment. Incidentally, a film-forming apparatus  101  shown in  FIG. 2  has the same structure as that of the film-forming apparatus  100  shown in  FIG. 1  except that the sub-heater  118  which is a heating unit is composed of a plurality of resistive-heating type heaters. Therefore, constituent elements common to the film-forming apparatus  101  and the film-forming apparatus  100  shown in  FIG. 1  are attached with same reference numerals and explanation thereof is omitted. For example, since the control system is explained later with reference to  FIG. 5 , it is not shown in  FIG. 2 . 
     For example, in the film-forming apparatus  101  which is another example of this embodiment, when the sub-heater  118  is divided into five sub-heaters, the sub-heater  118  of this embodiment can have a first sub-heater  118   a , a second sub-heater  118   b , a third sub-heater  118   c , a fourth sub-heater  118   d , and a fifth sub-heater  118   e . It is preferred that these sub-heaters be arranged along a vertical direction upward, namely, in this order from the side near to the substrate  7 . 
     In the case that the sub-heater  118  is separated into five individual heaters, the first sub-heater  118   a , the second sub-heater  118   b , the third sub-heater  118   c , the fourth sub-heater  118   d , and the fifth sub-heater  118   e  are provided around the top portion  2   b  of the liner  2 , and are supported by the first heater supporting portion  119   a , the second heater supporting portion  119   b , the third heater supporting portion  119   c , the fourth heater supporting portion  119   d , and the fifth heater supporting portion  119   e  respectively, each heater is connected with each supporting portion by connecting portions (not shown). Changing the distance between each supporting portion can modify the distance between each heater. 
     Furthermore, the first heater supporting portion  119   a , the second heater supporting portion  119   b , the third heater supporting portion  119   c , the fourth heater supporting portion  119   d , and the fifth heater supporting portion  119   e  are respectively connected through the sidewall of the chamber  1  to an outer electrode. Therefore, electricity can be individually conducted from the outer electrode through each supporting portion to each heater. As a result, each heater can be individually controlled. 
     The first sub-heater  118   a  is provided at the lowest position of the sub-heater  118  and is closest to the substrate  7  in the sub-heater  118 . The substrate  7  is heated from the top surface by the first sub-heater  118   a . The back surface of the substrate  7  is heated is also heated from the back surface by main-heater  9 . That is, the substrate  7  is heated from both sides by the main-heater  9  and the first sub-heater  118   a . As these heaters are the resistive heaters, the temperature of the substrate  7  can be precisely controlled. 
     The second sub-heater  118   b  is provided above the first sub-heater  118   a . The third sub-heater  118   c  is provided above the second sub-heater  118   b . The fourth sub-heater  118   d  is provided above the third sub-heater  118   c . The fifth sub-heater  118   e  is provided above the fourth sub-heater  118   d.    
     As the above-mentioned, the sub-heater  118  is the resistive heater. Therefore, the first sub-heater  118   a  heats the top portion  2   b , and then the heat of the top portion  2   b  heats the substrate  7 . When the sub-heater  18  consists of only the first sub-heater  18   a , this heater can heat only a small section of the top portion  2   b . That is, the temperature of the top portion  2   b  is distributed to the lower temperature unit, specifically to the upper side of the top portion  2   b . Accordingly, in this case, the heat of the top portion  2   b  cannot efficiently heat the substrate  7 . 
     The second sub-heater  118   b  and the third sub-heater  118   c  can prevent the loss of the heat from the first sub-heater  118   a  to the upper side of the top portion  2   b  of the liner  2 . That is, these heaters can decrease the difference of the temperature of the top portion  2   b  of the liner  2 . Therefore, the substrate  7  can be efficiently heated by the first sub-heater  118   a . Furthermore, the combination of heaters can prevent a crack in the liner  2  caused by the difference of the temperature of the top portion  2   b . The distribution of the temperature of the top portion  2   b  can be controlled by changing each temperature that is set in the first sub-heater  118   a  to the fifth sub-heater  118   e , and the distance between these heaters. 
     Further, in this embodiment, it is possible that the sub-heater is a high-frequency induction heating type heater. Further, it is possible that the sub-heater is composed of a plurality of high-frequency induction heating type heaters. 
       FIG. 3  is a cross-sectional view of a chamber in the film forming apparatus, as another example according to the present embodiment. Incidentally, a film-forming apparatus  102  shown in  FIG. 3  has the same structure as that of the film-forming apparatus  100  shown in  FIG. 1  except that the sub-heater  128 , which is a heating unit, is composed of a plurality of high-frequency induction type heaters. Therefore, constituent elements common to the film-forming apparatus  101  and the film-forming apparatus  100  shown in  FIG. 1  are attached with same reference numerals and explanation thereof is omitted. For example, since the control system is explained later with reference to  FIG. 5 , it is not shown in  FIG. 3 . 
     For example, in the film-forming apparatus  101 , which is another example of this embodiment, when the sub-heater  118  is divided into five sub-heaters, the sub-heater  118  can have a first sub-heater  118   a , a second sub-heater  118   b , a third sub-heater  118   c , a fourth sub-heater  118   d , and a fifth sub-heater  118   e . It is preferred that these sub-heaters be arranged along a vertical direction upward, namely, in this order from the side near to the substrate  7 . The number of separated sub-heaters is not limited to five; for example, two or four sub-heaters may be used along a vertical direction upward, that is, from the side close to the substrate  7 . 
     In the case that the sub-heater  128  is separated into five individual heaters, the first sub-heater  128   a , the second sub-heater  128   b , the third sub-heater  128   c , the fourth sub-heater  128   d , and the fifth sub-heater  128   e  are provided around the top portion  2   b  of the liner  2 , and are supported by the first heater supporting portion  129   a , the second heater supporting portion  129   b , the third heater supporting portion  129   c , the fourth heater supporting portion  129   d , and the fifth heater supporting portion  129   e  respectively, each heater is connected with each supporting portion by connecting portions (not shown). Changing the distance between each supporting portion can modify the distance between each heater. 
     Furthermore, the first heater supporting portion  129   a , the second heater supporting portion  129   b , the third heater supporting portion  129   c , the fourth heater supporting portion  129   d , and the fifth heater supporting portion  129   e  are respectively connected through the sidewall of the chamber  1  to an outer electrode. Therefore, electricity can be individually conducted from the outer electrode through each supporting portion to each heater. As a result, each heater can be individually controlled. 
     The first sub-heater  128   a  is provided at the lowest position of the sub-heater  128  and is closest to the substrate  7  in the sub-heater  128 . The substrate  7  is heated from the top surface by the first sub-heater  128   a , the second sub-heater  128   b , the third sub-heater  128   c , the fourth sub-heater  128   d , and the fifth sub-heater  128   e  from the upper side. The back surface of the substrate  7  is heated is also heated from the back surface by main-heater  9 . That is, the substrate  7  is heated from both sides by the main-heater  9  and the first sub-heater  128   a , the second sub-heater  128   b , the third sub-heater  128   c , the fourth sub-heater  128   d , and the fifth sub-heater  128   e . These heaters can be controlled individually to accurately control the temperature of the substrate  7 . 
     As shown in  FIG. 3  the second sub-heater  128   b  is provided above the first sub-heater  128   a . The third sub-heater  128   c  is provided above the second sub-heater  128   b . The fourth sub-heater  128   d  is provided above the third sub-heater  128   c . As mentioned above, the sub-heater  128  comprises a plurality of high-frequency induction heaters; therefore the heating effect depends on the distance from the substrate  7 . Therefore, the first sub-heater  128   a , the second sub-heater  128   b , third sub-heater  128   c , the fourth sub-heater  128   d , and the fifth sub-heater  128   e  differ in that heating effect from the sub-heaters to the substrate  7  lowers as the sub-heater is positioned further away from the substrate. The substrate  7  can be heated uniformly and efficiently by controlling these heaters, and the main heater  9  independently. 
     Next, the movement of the substrate  7  in the film forming apparatus  100  will be explained using  FIG. 1  and  FIG. 4 . The movement of the substrate  7  in the film forming apparatus  101  shown in  FIG. 2  and film forming apparatus  102  as shown in  FIG. 3  is the same. 
       FIG. 4  is a plane view showing the construction of a film forming apparatus  100 . As shown in  FIG. 4 , the film forming apparatus  100  includes the chamber  1  and substrate transfer robot control unit  332  as shown in  FIG. 1 , the cassette stage  310  and  312 , load-lock chamber  320 , transfer chamber  330 , and a substrate transfer robot control unit  350 . 
     In the cassette stage  310 , a cassette is provided in which the substrate  7  is set before the film forming process. In the cassette stage  312 , a cassette is provided in which the substrate  7  is set after the film forming process. 
     The substrate-transferring robot  350  removes the substrate  7  from the cassette stage  310  to transfer the substrate  7  to the load lock chamber  320 . The substrate-transferring robot  332  is disposed in the transfer chamber  330 . The transfer chamber  330  is connected with the chamber  1  where the film forming process is performed, and the substrate  7 , which has been transferred to the load lock chamber  320 , is transferred into the chamber  1  via the transfer chamber  330  by the substrate-transferring robot  332 . It is preferred that an insertion port for the substrate-transferring robot  332  in the chamber  1  be set below the head portion  2   b  of the liner  2 . 
     The substrate  7  that has been transferred into the chamber  1  is delivered to the pin from the substrate-transferring robot  332 . Thereafter, the substrate  7  is placed on the susceptor  8  according to lowering of the pin. 
     Next, the film forming process to the substrate  7  is started, specifically; the substrate  7  is rotated at atmospheric pressure or under an appropriate reduced vacuum pressure. The main-heater  9  and the sub-heater  18  heat the substrate  7 . 
     After the temperature of the substrate reaches the predetermined temperature, the reaction gas  4  is supplied from the supply portion  5 ; thereby vapor-phase growth film will be formed on the substrate  7 . 
     After the film forming process to the substrate  7  has been completed, an output of at least one of the main heater  9  and the sub-heater  18  is turned off or lowered in order to lower the temperature of the substrate  7 . When the sub-heater  18  is composed of a plurality of heaters, as previously described, an output of at least one of the main heater  9  and the respective heaters constituting the sub-heater  18  is turned off or lowered. 
     After it is confirmed that the temperature of the substrate  7 , measured by the radiation thermometers  24   a  and  24   b , has reached a predetermined temperature, the substrate can be transferred. A pin (not shown), capable of moving in an up and down direction is provided in the rotating shaft  16 . The end of the pin extends to a substrate rising means (not shown) provided at the bottom of the rotating shaft  16 . The pin can be moved up and down by the substrate rising means. The pin is used when the substrate  7  is transferred into and out of the chamber  1 . The pin supports the bottom of the substrate  7 , and then rises to move the substrate  101  away from the susceptor  8 . The substrate  7  is then positioned above the rotating portion  104  separate from the susceptor  8  by the pin, allowing a transfer robot  332  to remove the substrate  7 . The transfer robot  332  corresponds to a substrate transfer unit in the present invention. 
     The substrate  7  delivered to the substrate-transferring robot  332  is removed from the chamber  1 , and transferred to the load lock chamber  320  via the transfer chamber  330 . Next, the substrate  7  is set on the cassette arranged on the cassette stage  312  by the substrate-transferring robot  350 . 
     Thereafter, a substrate  7  to which the film forming process should be next performed is removed from the cassette stage  310  and transferred to the load lock chamber  320  by the substrate-transferring robot  350 . Next, the substrate  7  is transferred from the load lock chamber  320  to the transfer chamber  330  by the substrate-transferring robot  332 , and it is further transferred into the chamber  1  where the film forming process is performed. Thereafter, the film forming process is performed in the same manner as explained above and the substrate  7  is removed from the chamber  1  to be transferred up to the cassette stage  312 . 
     In order to transfer the substrate  7  to which the film forming process has been performed outside the chamber  1 , it is necessary to wait for the temperature within the chamber  1  to lower, specifically, the temperature of the substrate  7  to a predetermined temperature or below. If the substrate  7  is transferred out of the chamber  1  before the temperature of the substrate  7  is sufficiently lowered from the film forming process temperature, there is a possibility that a crack will occur in the substrate  7  due to a temperature difference between the temperature of the substrate  7  and the temperature outside. Further, since the substrate  7  and the vapor deposition film are different in their coefficient of thermal expansion, there is a possibility that peeling or cracking will occur in the vapor deposition film. 
     Therefore, after the film forming process has been completed, all the outputs of the main heater  9  and the sub-heater  18  can be turned off. After it has been confirmed by the radiation thermometers  24   a  and  24   b  that the substrate  7  has lowered to the predetermined temperature, the substrate  7  is lifted up by the pin to be delivered to the substrate-transferring robot  332 . Thereafter, another substrate  7  is transferred into the chamber  1  to be placed on the susceptor  8 . 
     When all the heaters are turned off, the temperature within the chamber  1  lowers. This lowering of the temperature continues even after the substrate  7  has been removed from the chamber  1 , so that the temperature of the substrate  7  becomes considerably lower than the predetermined temperature required for transferring the substrate  7  at such a time that another substrate  7  is placed on the susceptor  8 . That is, a difference between the temperature within the chamber  1  and the temperature required for the film forming is large. In this state, when all the heaters are turned on, the temperature within the chamber  1  rises but a long period of time is required until the temperature of the substrate  7  reaches the film forming temperature. 
     The temperature within the chamber  1  is required only to be the predetermined temperature or lower than a predetermined temperature for transferring the substrate  7  in and out of the chamber  1 . In view of these circumstances, the present invention has been designed so that a time required until a substrate  7 , to which the film forming process should be next performed, reaches the film forming temperature can be shortened by suppressing further lowering of the temperature within the chamber  1  to a minimum. 
     The film-forming apparatus of the present invention has output control units which control respective outputs of a plurality of heaters independently, and the output control units turn off or lower at least one output of the plurality of heaters such as the main heater and the sub-heaters when a film forming process to a substrate is completed. For example, the output control units can turn on all the plurality of heaters. The output control units operate such that, when the temperature within the film-forming chamber reaches a temperature at which the substrate-transferring unit is operable within the film-forming chamber, an output of at least one heater of the heaters, whose output has been turned off or lowered previously, is turned on or raised and when the substrate to which the film forming process has been performed is transferred out by the substrate-transferring unit and another substrate is transferred in thereby, and an output(s) of the remaining heater(s) except for the heater whose output was turned off or lowered previously is (are) turned on or raised. 
     More specifically, in the film-forming apparatuses  101  and  102  shown in  FIG. 2  and  FIG. 3 , the sub-heaters  118  and  128  are each composed of a plurality of heaters. In this case, in the sub-heater  118 / 128  disposed above the susceptor  8  are composed of a plurality of heaters (the first sub-heater  118   a / 128   a , the second sub-heater  118   b / 128   b , the third sub-heater  118   c / 128   c , the fourth sub-heater  118   d / 128   d , and the fifth sub-heater  118   e / 128   e ) disposed in a vertical direction, an output of at least one heater of the respective heaters constituting the sub-heater  118 / 128  can be turned off or lowered. 
     Further, the output of the main heater  9  can be turned off or lowered. When the main heater  9  is composed of a plurality of heaters ( 9   a  and  9   b ), an output of at least one of the respective heaters ( 9   a  and  9   b ) can be turned off or lowered. 
     When outputs of at least one heaters of heaters constituting the sub-heaters  118  and  128  are turned off or lowered, it is preferred that the heaters closest to the substrate  7 , namely, the output of the first sub-heater  118   a  in  FIG. 2  and the output of the first sub-heater  128   a  shown in  FIG. 3  be turned off or lowered. Thereby, it is made possible to perform control for lowering the temperature in the vicinity of the substrate  7  and the susceptor  8  within the chamber  1  effectively. 
     The film-forming apparatuses of present embodiments will be described below in detail. The explanation is performed using the film-forming apparatus  101  shown in  FIG. 2 , which is one example of these embodiments. 
     In this embodiment, after an output of at least one heater of the plurality of heaters such as the main heater  9  and the sub-heater  118  is turned off or lowered, according to the temperature within the chamber  1 , specifically, the temperature of the substrate  7  or the susceptor  8 , the timing of turning on outputs of the respective heaters and magnitudes of the outputs thereof are changed. Thereby, it can be made possible to suppress further lowering of the temperature within the chamber  1  from the predetermined temperature. 
       FIG. 5  is a diagram showing the relationship among control systems in the film-forming apparatus  101 . As shown in FIG.  5 , a substrate-transferring robot control unit  401  controls an operation of the substrate-transferring robot  332 . Further, the outputs of the in-heater  9   a , the out-heater  9   b , the first sub-heater  118   a , the second sub-heater  118   b , the third sub-heater  118   c , the fourth sub-heater  118   d , and the fifth sub-heaters  118   e  are controlled by output control units  402 ,  403 ,  404 ,  405 ,  406 ,  407 , and  408 , respectively. These control units control the operation of the substrate-transferring robot  332  and the outputs of the respective heaters based upon information from a temperature-measuring unit  400 , respectively. 
     As shown in  FIG. 5 , the temperature-measuring unit  400  measures the temperature within the chamber  1 . As the temperature, specifically, the temperature of the susceptor  8  can be adopted. Further, the temperature-measuring unit  400  may be at least one of the radiation thermometers  24   a  and  24   b  described in  FIG. 2 . 
       FIG. 6  is a graph illustratively showing a temporal change of the measurement result obtained by the temperature-measuring unit  400 . 
     In  FIG. 6 , a temperature Tep is the film forming temperature. A completion time t 1  of the film forming process to the substrate  7  can be determined, for example, by a supply time of the reaction gas  4 . In this embodiment, as an example, the outputs of the in-heater  9   a , the out-heater  9   b , the first sub-heater  118   a , the second sub-heater  118   b , the third sub-heater  118   c , the fourth sub-heater  118   d , and the fifth sub-heater  118   d  are turned off at the time t 1 . Thereby, the temperature Tep measured by the radiation thermometer Tep will lower. 
     In  FIG. 6 , a temperature T 1  is an upper limit of the temperature at which the substrate-transferring robot  332  can operate, while a temperature T 2  is an upper limit of the temperature at which the substrate  7  can be transferred out of the chamber  1 . 
     Therefore, at a time point (time t 2 ) at which the measurement temperature obtained by the temperature-measuring unit  400  has reached T 1 , the substrate-transferring robot  332  enters the chamber  1 . That is, in  FIG. 5 , when the temperature obtained by the temperature-measuring unit  400  reaches T 1 , a signal is transmitted to the substrate-transferring robot control unit  401 . The substrate-transferring robot control unit  401  controls the substrate-transferring robot  332  to enter into the chamber  1 . At a time point (time t 3 ) at which the measurement temperature has reached T 2 , the substrate-transferring robot control unit  401  controls the pin to lift the substrate  7  separating the substrate  7  from the susceptor  8 . Next, the substrate-transferring robot control unit  401  lifts the pin to transfer the substrate  7  to the substrate-transferring robot  332 . 
     In this embodiment, the outputs of the second sub-heater  118   b , the third sub-heater  118   c , the fourth sub-heater  118   d , and the fifth sub-heater  118   e  are turned on at the time t 2 . That is, in  FIG. 5 , when the temperature obtained by the temperature control unit  400  reaches T 1 , a signal is transmitted to the output control units  405 ,  406 ,  407 , and  408 . The output control unit  405  performs control such that the output of the second sub-heater  118   b  is turned on. The output control unit  406  controls such that the output of the third sub-heater  118   c  turns on. The output control units  407  controls such that the output of the fourth sub-heater  118   d  turns on. The output control unit  408  controls so that the output of the fifth sub-heater  118   e  turns on. 
     Since the second sub-heater  118   b , the third sub-heater  118   c , the fourth sub-heater  118   d , and the fifth sub-heater  118   e  are positioned separated from the substrate  7 , even if the outputs thereof are turned on at the time t 2 , the temperature of the substrate  7  continues to lower. Further, since the second sub-heater  118   b , the third sub-heater  118   c , the fourth sub-heater  118   d , and the fifth sub-heater  118   e  are also separated from the position where the substrate-transferring robot  332  enters the chamber, even if the substrate-transferring robot  332  enters into the chamber  1  at the time t 2 , there is no possibility that the substrate-transferring robot  332  is exposed to a temperature equal to or more than the heatproof temperature of the robot. On the other hand, since the head portion  2   b  positioned near the second sub-heater  118   b , the third sub-heater  118   c , the fourth sub-heater  118   d , and the fifth sub-heater  118   e  is heated, temperature lowering in at least one portion of the chamber  1  is suppressed. 
     In this embodiment, it is preferred that, after the outputs of the second sub-heater  118   b , the third sub-heater  118   c , the fourth sub-heater  118   d , and the fifth sub-heater  118   e  are turned on, the outputs of these heaters are changed in a stepwise fashion for each of the heaters. Further, at this time, it is preferred that the outputs of the heaters are raised from a lower output of a heater, of the heaters that are positioned closer to the substrate  7 . 
       FIG. 7  is a graph showing a relationship between the outputs of the respective heaters and time. In  FIG. 7 , E 1  denotes output change of the third sub-heater  118   c , and E 2  denotes output change of the second sub-heater  118   b . Further, E 3  denotes output changes of the first sub-heater  118   a , the in-heater  9   a , and the out-heater  9   b . Incidentally, in this case, the outputs of the fourth sub-heater  118   d  and the fifth sub-heater  118   e  can be set to be equal to the output of the third sub-heater  118   c , and the output changes thereof can be set to E 1 . Therefore, explanation is made using only the third sub-heater  118   c , explanation of the outputs of the fourth sub-heater  118   d  and the fifth sub-heater  118   e , which show similar output changes (E 1 ) is omitted. 
     As shown in  FIG. 7 , in this embodiment, the second sub-heater  118   b  and the third sub-heater  118   c  are turned on at the time t 2 . On the other hand, the respective outputs of the first sub-heater  118   a , the in-heater  9   a , and the out-heater  9   b  remain off. 
     Further, the output of the third sub-heater  118   c  at the time t 2  is more than the output of the second sub-heater  118   b . It is preferred that the outputs of these heaters  118   c  and  118   b  are increased as possible in order to suppress temperature lowering of the chamber  1 . However, when the outputs large are increased excessively, there is a possibility that the temperature lowering of the substrate  7  is prevented. Therefore, the output of the third sub-heater  118   c  positioned separated from the substrate  7 , is set to, for example, 70% of the maximum output thereof, and the output of the second sub-heater  118   b  is set to, for example, 30% of the maximum output thereof. Thereby, it is possible to suppress the temperature lowering of the chamber  1  without preventing the temperature lowering of the substrate  7 . 
     When the measurement temperature obtained by the temperature-measuring unit  400  reaches T 2  at the time t 3  in  FIG. 6 , the substrate  7  to which the film forming process has been performed is transferred outside the chamber  1 . In this embodiment, the output of the second sub-heater  118   b  is raised up to, for example, 50% of the maximum output thereof at the time t 4  after the time t 3 . Thereby, since the temperature within the chamber  1  is reversed so as to rise as a whole, as shown in  FIG. 6 , the measurement temperature obtained by the temperature-measuring unit  400  is raised. Incidentally, the time t 4  may be a time during transferring-out of the substrate  7 , or it may be a time during transferring-in of another substrate  7  to which the film forming process should be next performed. 
     It is necessary to place a substrate  7  to which the film forming process should be newly performed on the susceptor  8  and maintain the temperature within the chamber  1  at a temperature of T 1  or lower until the substrate-transferring robot  332  exits from the chamber  1 . Therefore, the measurement result obtained by the temperature-measuring unit  400  is maintained at T 1  or lower by keeping the outputs of the first sub-heater  118   a , the in-heater  9   a , and the out-heater  9   b  off, until the substrate-transferring robot  332  exits from the chamber  1 , and adjusting the outputs of the third sub-heater  118   c  and the second sub-heater  118   b.    
     After the substrate  7  which has been newly transferred in is placed on the susceptor  8  and the substrate-transferring robot  332  exits from the chamber  1 , the output of the second sub-heater  118   b  and the third sub-heater  118   c  are raised up to the maximum outputs (100%). Further, the outputs of the first sub-heater  118   a , the in-heater  9   a , and the out-heater  9   b  are turned on. Here, since it is preferred that the temperature of the substrate  7  reaches the film forming temperature Tep as fast as possible, the magnitudes of the outputs of the first sub-heater  118   a , the in-heater  9   a , and the out-heater  9   b  are set to the maximum outputs (100%) from the start. 
     The timing (time t 5 ) where the outputs of all the heaters are raised up to 100% can be determined based upon the measurement result of the temperature-measuring unit  400 . For example, after the substrate  7  is placed on the susceptor  8  and the substrate-transferring robot  332  exits from the chamber  1 , if the measurement temperature obtained by the temperature-measuring unit  400  reaches the T 1  without delay, the outputs of the respective heaters can be raised up to 100% at a time when the measurement result at the temperature-measuring unit  400  has reached T 1 . Specifically, this process is performed in the following manner. 
     As described above, when the output of the second sub-heater  118   b  is raised at the time t 4 , the temperature within the chamber  1  rises. At this time, a relationship of t′≧t″ is established by adjusting the outputs of the second sub-heater  118   b  and the third sub-heater  118   c.    
     In the expression (1), t′ is a time (t 5 ) elapsing until the measurement temperature at the temperature-measuring unit  400  reaches T 1 . Further, t″ is a time required from placing of the substrate  7  on the susceptor  8  up to exiting of the substrate-transferring robot  332  from the chamber  1 . 
     It is preferred that a difference between t′ and t″ is as small as possible in order to improve the throughput of the film-forming apparatus. Here, t′ can be changed by adjusting the respective outputs of the second sub-heater  118   b  and the third sub-heater  118   c . For example, by raising the output of the second sub-heater  118   b  further finely after the time t  4 , or raising the output of the third sub-heater  118   c  in a stepwise fashion, t′ can be made short. Therefore, when the difference between t′ and t″ is large, t′ can be brought close to t″ by this method. 
     According to formula (1), when the temperature at the temperature-measuring unit  400  reaches T 1 , a signal is transmitted to the output control units  402  to  406 . The output control unit  402  turns on the output of the in-heater  9   a  and raises the magnitude of the output up to the maximum output (100%), as shown by E 3  in  FIG. 7 . Similarly, the output control unit  403  and the output control unit  404  turn on the output of the out-heater  9   b  and the output of the first sub-heater  118   a , respectively, and raise the respective outputs to the maximum outputs (100%). Further, the output control unit  405  controls the second sub-heater  118   b  to reach the maximum output (100%), as shown by E 2  in  FIG. 7 . Furthermore, the output control unit  406  controls the third sub-heater  118   c  to reach the maximum output (100%), as shown by E 1  in  FIG. 7 . 
     By raising the outputs of all the heaters up to the maximum outputs (100%), the temperature within the chamber  1  rises rapidly. That is, as shown in  FIG. 6 , the rising ratio of the temperature at the time t 5  at which the temperature has reached the temperature T 1 , thereafter becomes larger than the previous rising ratio. When the temperature reaches the film forming temperature Tep, the reaction gas  4  is introduced into the chamber  1  from the supply unit  5  shown in  FIG. 2  so that a vapor deposition film is formed on the substrate  7 . 
     Thus, according to the film-forming apparatus  101  of this embodiment, the timing for turning-on of the outputs, and the magnitudes of the outputs of the respective heaters can be changed in response to the temperature within the chamber  1 . Thereby, since it can be suppressed that the temperature within the chamber  1  lowers largely from the upper limit (T 2 ) of the temperature at which the substrate  7  can be transferred out of the chamber  1 , the time from completion of the film forming process up to performance of the next film forming process can be suppressed to a minimum, thereby improving the throughput. As one example, by setting T 1  to 1000° C., and setting T 2  to 900° C., and performing temperature control, a time from completion of the film forming process at the film-forming temperature of 1600° C. up to performance of the next film forming process can be considerably shortened, and the throughput can therefore be improved. 
     Incidentally, in this embodiment, the number of heaters constituting the sub-heater  118  can be changed appropriately. For example, two or more heaters assisting the main heater  9  may be used. Further, the number of heaters corresponding to the second sub-heater  118   b , the third sub-heater  118   c , the fourth sub-heater  118   d , and the fifth sub-heaters  118   e  may be set to any number. Regardless of the number of sub-heaters, the sub-heaters are independently temperature-controlled via supporting units supporting these sub-heaters, respectively. By increasing the number of heaters, the temperature within the chamber  1  can be controlled further, so that it becomes easy to inhibit excessive lowering of the temperature. 
     Further, in the respective examples of the above embodiments, the sub-heater is composed of the resistive-heating type heater or the high-frequency induction heating type heater, but the sub-heater of this embodiment can be composed of a combination of the resistive-heating type heater and the high-frequency induction heating type heater. Further, such a process is adopted that after the substrate, which has been newly transferred in the chamber  1 , is placed on the susceptor  8  and the substrate-transferring robot is caused to exit from the chamber, the heaters are raised up to the maximum outputs. However, such a process can be adopted that after a signal indicating that the substrate-transferring robot has exited is received, the outputs of the heaters are raised. The signal can be provided by providing the position sensor indicating that the substrate-transferring robot has exited, or a sensor  340  indicating that a lid positioned between the transfer chamber and the chamber where the film forming process is performed has been closed, as shown in  FIG. 10  and  FIG. 11 . Thereby, it is made possible to achieve improvement in throughput safely. 
     Embodiment 2 
     A film-forming method for the formation of silicon carbide, wherein, a reaction gas is supplied into a film-forming chamber and a film of silicon carbide is formed on a substrate while the substrate is being heated by a plurality of heating units, after the formation of a silicon carbide on a substrate, at least one output of the plurality of heating units is turned off or lowered, when the temperature within the film-forming chamber reaches T 1  or lower, at least one output of the plurality of heating units which has been turned off or lowered, is turned on or raised, and a substrate-transferring unit then enters the film-forming chamber, when the temperature within the film-forming chamber reaches T 2  (incidentally, T 1 &gt;T 2 ) or lower, the substrate is transferred out of the film-forming chamber by the substrate-transferring unit, and another substrate is then transferred into the film-forming chamber by the substrate-transferring unit and the outputs of the remaining heating units are turned on or raised. 
       FIG. 8  is a flowchart of a film forming method according to the present embodiment. The film forming apparatus  101  in embodiment 1 performs the film forming method. The vapor-phase growth film forming method of formation of Si or SiC according to the present embodiment will be mentioned referring to  FIG. 2 ,  FIG. 4  to  FIG. 8 . The film forming method according to the present embodiment can also be applied to other vapor-phase growth film. Next, an example of the film-forming method in the present embodiment is described referring to  FIG. 1 . 
     A SiC wafer can be used as the substrate  7 , as one example. However, the substrate  7  is not limited to a SiC wafer. The material of the substrate  7  may be, for example, Si, Sio2 (quartz) or another insulator. A highly resistive semi-insulating substrate such as GaAs (gallium arsenide) can also be used. 
     Firstly, the substrate  7  is transferred into the chamber  1  and then placed on the susceptor  8 . 
     Next, the substrate  7  is rotated at atmospheric pressure or under an appropriate reduced vacuum pressure. The susceptor  8  on which the substrate  7  is placed is positioned on the upper end of the rotating cylinder  17 . When the rotating cylinder  17  is rotated via the rotating shaft  16 , the susceptor  8  is rotated via the rotating cylinder  17 , and consequently the substrate  7  can be rotated via the susceptor  8 . The number of revolutions of the substrate  7  which can be rotated at is approximately 50 rpm. 
     In the present embodiment, the main-heater  9  and the sub-heater  18  heat the substrate  7 . In the Si vapor deposition reaction, it is necessary to heat the substrate  7  up to 1000° C. or higher, while it is necessary to heat the substrate  7  up to 1500° C. or higher in the SiC vapor deposition. It is preferred that the respective output, and therefore respective temperatures, of the heaters are set such that the output of the out-heater  9   b  is higher than the output of the in-heater  9   a , and the output of the first sub-heater  118   a  is higher than the second sub-heater  118   b , the output of the second sub-heater  118   b  is higher than the third sub-heater  118   c , the output of the third sub-heater  118   c  is higher than the fourth sub-heater  118   d , and the fourth sub-heater  118   d  is higher than the fifth sub-heater  118   e.    
     As mentioned above, allowing cooling water to flow through the flow path  3  provided in the wall of the chamber  1  can prevent an excessive increase in the temperature of the film-forming chamber  1 . 
     After it is confirmed that the temperature of the substrate  7  has reached a predetermined temperature, the number of revolutions of the substrate  7  is gradually increased. For example, the number of revolutions of the substrate  7  can be increased to 900 rpm. The reaction gas  4  is supplied from the supply portion  5 . 
     As the reaction gas  4 , trichlorosilane can be used when an Si film is formed, while when an SiC film is formed, monosilane, dichlorosilane, trichlorosilane, or silicone tetrachloride or the like can be used as an Si source, propane, ethylene or the like can be used as a C source, and HCl can be used as an additive gas, where these gases are introduced from the supply unit  5  in a state thereof mixed with hydrogen gas or argon gas serving as a carrier gas. 
     The reaction gas  4  passes via the through-holes  15   a  of the shower plate  15 , and then flows into the space A in which the vapor-phase growth reaction will be performed on the substrate  7 . At this time, the flow of the reaction gas  4  is straightened by the gas passing through the shower plate  15  serving as a straightening vane so that the reaction gas  4  flows substantially vertical downward toward the substrate  7  under the shower plate  15 . 
     When the reaction gas  4  reaches the surface of the substrate  7 , a thermal decomposition reaction or a hydrogen reduction reaction occurs so that a Si epitaxial film or a SiC epitaxial film is formed on the surface of the substrate  7 . Surplus reaction gas  4  that isn&#39;t used for the vapor-phase growth reaction, and gas generated by the vapor-phase growth reaction, is discharged through the discharge portion  6  provided in the lower unit of the film-forming chamber  1 . 
     The Si vapor deposition film or the SiC vapor deposition film can be formed on the substrate  7  in the above manner. After the film formation on the substrate  7  has been completed, a film forming process on another substrate  7  is performed. A process between the completion and start of the film forming process is performed according to a flowchart shown in  FIG. 8 . 
     First of all, as shown at step S 1  in  FIG. 8 , all the heaters, namely, the in-heater  9   a , the out-heater  9   b , the first sub-heater  118   a , the second sub-heater  118   b , the third sub-heater  118   c , the fourth sub-heater  118   d , and the fifth sub-heater  118   e  are turned off. 
     Next, the temperature T within the chamber  1  is measured (step S 2 ). Here, as the temperature T, the temperature of the susceptor  8  can be adopted. Further, the measurement is performed using at least one of the radiation thermometers  24   a  and  24   b.    
     At step S 3 , determination is as to whether or not the temperature T within the chamber  1  is at the upper limit T 1  of the temperature at which the substrate-transferring robot  332  is operable or less than the upper limit T 1 . When T&gt;T 1 , the process returns to step S 2  and the measurement is continued. On the other hand, when T≦T 1 , the control proceeds to step S 4 , where the substrate-transferring robot  332  is introduced into the chamber  1 . 
     As shown in  FIG. 5 , the substrate-transferring robot control unit  401  performs control of the substrate-transferring robot  332 . Here, the temperature-measuring unit  400  shown in  FIG. 5  is provided with not only a function of causing the radiation thermometers  24   a  and  24   b  to perform the temperature measurement but also a function of performing respective determinations (S 3 , S 6 , and S 13 ) shown in  FIG. 8 . When T≦T 1  is determined by the temperature-measuring unit  400 , a signal indicating the determination is transmitted to the substrate-transferring robot control unit  401 . Thereby, the substrate-transferring robot control unit  401  controls the substrate-transferring robot  332  so as to be introduced into the chamber  1 . 
     Subsequently, the temperature T within the chamber  1  is similarly measured at step S 5  as in the step S 2 . Next, determination is made at step S 6  as to whether or not the temperature T within the chamber  1  is the upper limit T 2  of the temperature at which the substrate  7  can be transferred out of the chamber  1  or less. When T&gt;T 2  is determined, the control returns to step S 5  and the measurement is continued. When T≦T 2  is determined, the control proceeds to step S 7 , where the substrate  7  is transferred out of the chamber  1  and the respective outputs of the second sub-heater  118   b , the third sub-heater  118   c , the fourth sub-heater  118   d  and the fifth sub heat  118   e  are turned on. This operation is performed through the output control units  405 ,  406 ,  407 , and  408  shown in  FIG. 5 . That is, when T≦T 2  is determined at the temperature-measuring unit  400 , a signal indicating the determination is transmitted to the output control units  405 ,  406 ,  407 , and  408 . Thereby, these output control units turn on the outputs of the second sub-heater  118   b , the third sub-heater  118   c , the fourth sub-heater  118   d , and the fifth sub-heater  118   e , respectively. Further, the output control units  405 ,  406 ,  407 , and  408  can control output values of heaters corresponding thereto as shown by chart in  FIG. 7 . For example, the output control units  406 ,  407 , and  408  can control the output values of the third sub-heater  118   c , the fourth sub-heater  118   d , and the fifth sub-heater  118   e  corresponding thereto as shown by E 1  of the chart shown in  FIG. 7 , respectively. 
     The transferring-out of the substrate  7  from the chamber  1  is performed in the same manner as described in the first embodiment. That is, the substrate  7  is supported from below by the pin (not shown); the substrate is then lifted up and separated from the susceptor  8 . After the pin is raised as it is, the substrate  7  is delivered to the substrate-transferring robot  332 . 
     The substrate  7 , which has been delivered to the substrate-transferring robot  332 , is removed from the chamber  1 , and is transferred to the load lock chamber  320  via the transfer chamber  330  shown in  FIG. 4 . Next, the substrate  7  is set in the cassette arranged on the cassette stage  312  by the substrate-transferring robot  350 . 
     Thereafter, a substrate  7  to which the film forming process should be next performed is removed from the cassette stage  310 , and it is transferred to the load lock chamber  320  by the substrate-transferring robot  350 . Next, the substrate  7  is transferred from the load lock chamber  320  to the transfer chamber  330  by the substrate-transferring robot  332  and it is further transferred into the chamber  1  where the film forming process is performed (step S 8 ). 
     In this embodiment, it is preferred that the outputs of the second sub-heater  118   b  to the fifth sub-heater  118   e  are raised in a stepwise fashion. Further, in this case, it is preferred that the output of the second sub-heater  118   b  is raised from its value lower than the value of the output of the third sub-heater  118   c . It is preferred that the output of the third sub-heater  118   c  is raised from its value lower than the value of the output of the fourth sub-heater  118   d . It is preferred that the output of the fourth sub-heater  118   d  is raised from its value lower than the value of the output of the fifth sub-heater  118   e.    
     In this embodiment, after the transfer of the substrate  7  to which the film forming process should be next performed into the chamber  1  starts, the output of the second sub-heater  118   b  is raised as shown in  FIG. 6  (step S 9 ). Thereby, the temperature change within the chamber  1  can be reversed, that is, the temperature can rise. 
     Next, the substrate  7  is placed on the susceptor  8 , and the substrate-transferring robot  332  is exits from the chamber  1  (step S 10 ). Thereafter, at step S 11 , the outputs of the second sub-heater  118   b  to the fifth sub-heater  118   e  are raised to the maximum outputs (100%). Further, the outputs of the first sub-heater  118   a , the in-heater  9   a , and the out-heater  9   b  are turned on. The magnitudes of these outputs are raised to the maximum outputs (100%) from the start. 
     At step S 12 , the temperature T within the chamber  1  is measured in the same manner as the case of step S 2  or S 5  and determination is made about whether or not the temperature T is the film forming temperature Tep or higher. When T&lt;Tep is determined, the process returns to the step S 12  and the measurement is repeated. On the other hand, when T≧Tep is determined, the process proceeds to step S 14 , where the reaction gas  4  is introduced into the chamber  1 . Thereby, a Si vapor deposition film is formed on the substrate  7 . 
     According to this embodiment, since the timing of turning-on the outputs of the respective heaters and the magnitudes of the outputs thereof are changed according to the temperature within the chamber  1 , it can be inhibited that the temperature within the chamber  1  lowers largely from the upper limit (T 2 ) of the temperature at which the substrate  7  can be transferred out of the chamber  1 . Therefore, the time elapsing from completion of the film forming process to the start of the next film forming process can be suppressed to a minimum thereby improving throughput. 
     Incidentally, in  FIG. 8 , the temperatures are measured at steps S 2 , S 5  and S 12 , but such a configuration can be adopted that the temperature measurement is always performed in parallel with the respective steps S 1  to S 14  and determinations based upon the respective measurement results at the steps S 3 , S 6 , and S 13  are made. 
       FIG. 9  is a graph of a comparative example of this embodiment, and it illustratively shows the temporal change of the measurement result obtained by the temperature-measuring unit  400 . In  FIG. 9 , the temperature Tep denotes a film forming temperature and the temperature T 2  denotes an upper limit of the temperature at which the substrate  7  can be transferred out of the chamber  1 . Further, the time t 1 ′ denotes the completion time of the film forming process and the time T 3 ′ denotes a time at which the temperature within the chamber  1  reaches the temperature T 2 . 
     In the example shown in  FIG. 9 , the outputs of all the heaters at the time t 1 ′, namely, the in-heater  9   a , the out-heater  9   b , the first sub-heater  118   a , the second sub-heater  118   b , the third sub-heater  118   c , the fourth sub-heater  118   d , and the fifth sub theater  118   e  are turned off. Then, when the temperature within the chamber  1  lowers to T 2 , the substrate  7  after the film forming process is transferred out of the chamber  1 , and instead, a substrate  7  to which the film forming process should be next performed is transferred into the chamber  1 . Next, after the substrate  7  is placed on the susceptor  8  and the substrate-transferring robot  332  is exits from the chamber  1 , the outputs of all the heaters are turned on at the time t 5 ′. The magnitudes of the outputs at this time are set to the maximum outputs (100%). When the temperature within the chamber  1  reaches the film forming temperature Tep at the time t 6 ′, the reaction gas  4  is introduced into the chamber  1  and a vapor deposition film is formed on the substrate  7 . 
     As described above, when the timing of turning-on of the outputs of all the heaters are set to be the same, the temperature continuously lowers until the time t 5 ′. Therefore, there is a large gap between the temperature within the chamber  1  at the time t 5 ′ and the temperature T 2 , and as a result, a long time is required to raise the temperature up to the film forming temperature Tep. 
     On the other hand, as in embodiment, by changing the timing of turning-on of the outputs of the heaters according to the respective heaters, and turning on some of the heaters at a time earlier than those in the example shown in  FIG. 9 , lowering of the temperature within the chamber  1  can be inhibited as compared to the example shown in  FIG. 9 . Further, when the output values of the heaters are changed in response to a situation of transferring-in/transferring-out of the substrate  7 , the above-described temperature lowering can be further suppressed. That is, according to this embodiment, it is possible to shorten the time elapsing from the completion of the film forming process, to the next film forming process, as compared with the example shown in  FIG. 9  thereby achieving an improvement in throughput. 
     Features and advantages of the present invention can be summarized as follows. 
     According to the present invention, such a film-forming apparatus for silicon carbide and a film-forming method for the formation of silicon carbide can be provided that the output control units operate to turn off or lower the output of at least one heating unit of a plurality of heating units when the film forming process to the substrate is completed and to turn on or raise the output of the at least one heating unit whose output has been turned off or lowered when the temperature measured by the temperature-measuring unit reaches the temperature at which the substrate-transferring unit is operable within the film-forming chamber to cause the substrate-transferring unit to transfer the substrate to which the film forming process has been performed out of the film-forming chamber, so that the time elapsing from completion of the film forming process to performance of the next film forming process can be suppressed to a minimum, thus resulting in an improvement in throughput. 
     The present invention is not limited to the embodiments described above and can be implemented in various modifications without departing from the spirit of the invention. For example, the above embodiment has described an example of a film-forming process while rotating the substrate in a film-forming chamber; the present invention is not limited to this. The film-forming apparatus of the present invention may be deposited on the substrate while stationary and not rotating. 
     In addition to the above embodiments, a vapor-phase growth system cited as the example of a film-forming apparatus in the present invention is not limited to this. Reaction gas supplied into the film-forming chamber for forming a film on its surface while heating the wafer can also be applied to other apparatus such as a CVD (Chemical Vapor Deposition) film-forming apparatus, and to form other epitaxial film in which the apparatus can transfer the substrate. 
     The above description of the invention has not specified apparatus constructions, control methods, etc. which are not essential to the description of the invention, since any suitable apparatus constructions, control methods, etc. can be employed to implement the invention. 
     Moreover, the scope of this invention encompasses all film-forming apparatus employing the elements of the invention and variations thereof, which can be designed by those skilled in the art.