Patent Publication Number: US-2010107977-A1

Title: Film forming apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of Ser. No. 10/467,293, filed Aug. 7, 2003, which is the National Stage of International Application PCT/JP02/01110 filed on Feb. 8, 2002 in the Japanese language, and claims the benefit of JP 2001-034520 filed Feb. 9, 2001, which applications are incorporated herein by reference. 
     This application is also a continuation of U.S. patent application Ser. No. 12/404,878 filed Mar. 16, 2009, which is a continuation of U.S. Ser. No. 11/727,485 filed Mar. 27, 2007, now abandoned, which is a divisional application of U.S. Ser. No. 10/467,293 filed Aug. 7, 2003 which is a national stage application of PCT/JP02/01110 filed Feb. 8, 2002 in the Japanese language and claims the benefit of JP 2001-034520 filed Feb. 9, 2001, each of which are incorporated herein in its entirety. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to a film-forming apparatus that forms a predetermined thin film onto a substrate to be processed by means of chemical vapor deposition process (CVD). 
     BACKGROUND ART 
     In a semiconductor-device manufacturing process, in order to fill holes between electric wirings formed on a semiconductor wafer as an object to be processed, or in order to provide barrier layers, a metal such as Ti, Al or Cu and/or a metal compound such as WSi, TiN or TiSi is deposited to form a thin film. 
     Conventionally, such thin film of the metal or metal compound is deposited by means of physical vapor deposition process (PVD). However, recently, it is requested to make devices micro and highly integrated, so that design-rule is especially severe. Thus, it is difficult to obtain sufficient properties by PVD, which is inferior in filling performance. Then, such thin film starts to be deposited by CVD, which we can expect forms a film of better quality. 
     As a conventional CVD film-forming apparatus, an apparatus for forming a Ti film is explained as an example. In the CVD film-forming apparatus for forming a Ti film, a pedestal, in which a heater is embedded and onto which a semiconductor wafer is placed, is arranged in a chamber having another heater. A showerhead for discharging a process gas is provided above and opposite to the pedestal. The chamber is heated to a predetermined temperature, and the inside of the chamber is vacuumed to a predetermined vacuum level. Then, the semiconductor wafer placed on the pedestal is heated to a predetermined temperature, while the process gas such as TiCl 4 , H 2  and the like is supplied from the showerhead. In addition, a high-frequency electric power is applied to the showerhead, so that the process gas is changed to plasma thereof. Then, the film-forming process is conducted. 
     However, recently, the semiconductor wafer starts to be enlarged to 300 mm. Thus, the film-forming apparatus has to be enlarged correspondingly. Therefore, the following problems appear manifestly. 
     When the temperature of the heater embedded in the pedestal rises up, the showerhead provided opposed to the pedestal is heated by radiant heat thereof. However, when the unit is enlarged, the showerhead is also enlarged, that is, heat capacity thereof becomes larger, so that it takes a longer time for the temperature to become stable when the showerhead is heated. That is, the throughput is deteriorated. If the temperature of the showerhead, that is, the surface temperature of the showerhead is not stable during a process, the process is not uniformly conducted. In addition, the conventional showerhead has a structure with high heat-insulating properties, in order to secure temperature stability during a process. Thus, if the showerhead is enlarged, it takes also a longer time to lower the temperature to a predetermined temperature, for example for a cleaning process. If the cleaning process is conducted under a high-temperature state, the showerhead member may be damaged. 
     In addition, during an idling state, the temperature of the pedestal has to be set higher than that during the process, in order to maintain the temperature of the showerhead at a predetermined temperature. This is explained in detail. Conventionally, during the plasma process, the temperatures of members in the chamber are raised by the plasma. Especially, the surface temperature of the showerhead tends to be raised because it has a large area opposed to the wafer surface and exposed to the plasma. However, when a film-forming process is conducted after an idling state or a cleaning process, it is possible that a film-forming rate for the first wafer is low. It is thought that the reason is that the temperature of the showerhead is low. That is, the temperature thereof is about 500° C. during a normal film-forming process, but it is thought that the temperature falls down by about 20 to 30° C. In order to prevent this, during the idling state or the cleaning process, the temperature of the pedestal had to be set higher than the film-forming temperature. 
     Furthermore, conventionally, at a maintenance process of the showerhead, an upper lid including the showerhead is opened by a degree not larger than 90 degrees, and then the showerhead is removed or the like. However, as the film-forming apparatus is enlarged, when the showerhead is also bulked or enlarged, it is difficult to conduct the maintenance process of the showerhead in accordance with the conventional method. 
     SUMMARY OF THE INVENTION 
     This invention is intended to solve the above problems. The object of this invention is to provide a film-forming apparatus that can lead a showerhead to a predetermined temperature within a short time and wherein temperature stability of the showerhead is high, and to provide a film-forming apparatus wherein maintenance of the showerhead can be easily conducted. 
     This invention is a film-forming apparatus comprising: a processing container that defines a chamber; a pedestal arranged in the chamber, on which a substrate to be processed can be placed; a showerhead provided opposite to the pedestal, which has a large number of gas-discharging holes; a gas-supplying mechanism that supplies a process gas into the chamber through the showerhead; and a showerhead-temperature controlling unit that controls a temperature of the showerhead. 
     According to the invention, since the showerhead is provided with the temperature controlling unit, the showerhead can be actively controlled to a desired temperature, when the showerhead is heated. Thus, even if the film-forming apparatus is larger, the temperature of the showerhead can be raised and lowered within a short time. In addition, by actively controlling the temperature of the showerhead, temperature stability of the showerhead can be enhanced. 
     Furthermore, for example in a case of Ti-film-forming apparatus, when a pre-coated film is formed on the showerhead or the like before a process to the substrate to be processed, or when a Ti film is formed on the substrate to be processed, the film is also formed (deposited) on a surface of the showerhead. At that time, in order to form a stable film on the surface of the showerhead, Ticl x , which is generated by an intermediate reaction, has to be volatilized. Thus, the showerhead has to be heated over 425° C., in particular over 500° C. In a conventional art, it takes a long time to heat the showerhead, and it is uncertain whether the showerhead is at a desired temperature, so that such a stable film may not be generated. However, by providing the temperature-controlling unit in the showerhead, the showerhead can be controlled to a desired temperature during a film-forming process or a pre-coating process, so that a stable film can be surely formed on the showerhead. Therefore, the first film-forming process can be stably conducted. 
     Preferably, the processing container is formed in such a manner that the processing container can be vacuumed. 
     In addition, preferably, the film-forming apparatus further comprises a heating unit that heats the pedestal. 
     In addition, preferably, the showerhead has: a chamber-inside part that includes a surface in which the large number of gas-discharging holes appear; and an atmosphere-side part that contacts with atmospheric air outside the chamber; and the showerhead-temperature controlling unit is provided in the atmosphere-side part. 
     In the case, the showerhead-temperature controlling unit can be handled in the atmospheric air. 
     In addition, preferably, the film-forming apparatus further comprises a second heating unit that heats the chamber. 
     In addition, preferably, the showerhead-temperature controlling unit includes: a heating mechanism that heats the showerhead; a cooling mechanism that cools the showerhead; a temperature-detecting mechanism that detects a temperature of the showerhead; and a controller that controls at least the heating mechanism, based on a result detected by the temperature-detecting mechanism. 
     In the case, the showerhead can be rapidly controlled to a desired temperature when the showerhead is both heated and cooled. 
     In addition, in the case, more preferably, the heating mechanism has: an inside heater that heats an inside portion of the showerhead; and an outside heater that heats an outside portion of the showerhead; and the temperature detecting mechanism has: an inside-temperature detecting part that detects a temperature of the inside portion; and an outside-temperature detecting part that detects a temperature of the outside portion. 
     In the case, more preferably, the controller is adapted to control the inside heater in such a manner that a value detected by the inside-temperature detecting part coincides with a set temperature, and to control the outside heater in such a manner that a difference between a value detected by the outside-temperature detecting part and the value detected by the inside-temperature detecting part coincides with zero. 
     In the case, heat dissipation from the outside portion of the showerhead can be inhibited, so that more accurate temperature control can be achieved. 
     In addition, preferably, a thermal-insulating member is arranged on a surface of the showerhead reverse to the chamber. 
     In the case, during the process, heat dissipation from the showerhead can be effectively inhibited. 
     In addition, preferably, the showerhead has: a showerhead body; and a circular supporting part continued upward from on an outside periphery of the showerhead body; and the supporting part has a rib structure. 
     In the case, since the portion of the supporting part other than the rib structure can be made thin, heat dissipation from the supporting part can be reduced. Thus, temperature controlling performance can be more enhanced. 
     In the case, more preferably, an insulating member is arranged on the showerhead body and inside the supporting part. 
     In addition, preferably, a circular infilling member and a fixing member for fixing the infilling member to the showerhead or the processing container are arranged between the showerhead and the processing container. 
     In the case, more preferably, a resilient member is interposed between the infilling member and the fixing member. In the case, even when quartz, ceramics and so on is used as the infilling member, it can be prevented that the infilling member is damaged. In addition, by means of the resilient member, the interval between the infilling member and the fixing member can be made uniform. 
     In addition, preferably, the film-forming apparatus further comprises a plasma-generating unit for generating plasma of the process gas in the chamber. 
     In addition, preferably, the film-forming apparatus further comprises an inverting mechanism that inverts the showerhead by turning the showerhead outwardly from the chamber. 
     In the case, the showerhead is turned outwardly from the chamber, and thus inverted, so that the showerhead can be taken out from the chamber substantially completely. Thus, maintenance of the showerhead can be conducted very easily. 
     In addition, this invention is a film-forming apparatus comprising: a processing container that defines a chamber; a pedestal arranged in the chamber, on which a substrate to be processed can be placed; a showerhead provided opposite to the pedestal, which has a large number of gas-discharging holes; a gas-supplying mechanism that supplies a process gas into the chamber through the showerhead; and an inverting mechanism that inverts the showerhead by turning the showerhead outwardly from the chamber. 
     According to the invention, the showerhead is turned outwardly from the chamber, and thus inverted, so that the showerhead can be taken out from the chamber substantially completely. Thus, maintenance of the showerhead can be conducted very easily. 
     Preferably, a circular infilling member and a fixing member for fixing the infilling member to the showerhead or the processing container are arranged between the showerhead and the processing container. 
     In the case, more preferably, a resilient member is interposed between the infilling member and the fixing member. In the case, even when quartz, ceramics and so on is used as the infilling member, it can be prevented that the infilling member is damaged. In addition, by means of the resilient member, the clearance between the infilling member and the fixing member can be made uniform. 
     More preferably, the fixing member is outwardly removable in a state wherein the showerhead is inverted, and the infilling member is upwardly removable in a state wherein the fixing member has been outwardly removed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view showing a CVD film-forming apparatus of an embodiment according to the present invention; 
         FIG. 2  is a plan view showing an upper portion of the showerhead of the CVD film-forming apparatus of the embodiment according to the present invention; 
         FIG. 3  is an enlarged sectional view showing a filler portion of the apparatus of  FIG. 1 ; 
         FIG. 4  is a schematic view showing a portion corresponding to a heating mechanism in a temperature-controlling unit of the apparatus of  FIG. 1 ; 
         FIG. 5  is a schematic view showing a preferable control manner in heating and controlling by means of the temperature-controlling unit of the apparatus of  FIG. 1 ; 
         FIG. 6  is a sectional view showing a state wherein a showerhead of the apparatus of  FIG. 1  is inverted by an inverting mechanism; 
         FIG. 7  is an enlarged view of the showerhead of the apparatus of  FIG. 1 ; 
         FIG. 8  is a sectional view taken along A-A line of  FIG. 7 ; 
         FIG. 9  is a sectional view taken along B-B line of  FIG. 7 ; 
         FIG. 10  is a plan view showing a lower plate wherein a gas-diffusion-promoting pipe is provided; 
         FIG. 11  is a sectional view of the lower plate and a middle plate wherein the gas-diffusion-promoting pipe of  FIG. 10  is attached; 
         FIG. 12  is a schematic view showing a variant of the portion corresponding to a heating mechanism of  FIG. 4 ; 
         FIG. 13  is a schematic view showing a variant of the control manner of  FIG. 5 ; 
         FIG. 14  is a sectional view showing a CVD film-forming apparatus of another embodiment according to the present invention; and 
         FIG. 15  is a sectional view showing a variant of the filler member of  FIG. 3 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Hereinafter, a CVD film-forming apparatus for forming a Ti thin film according to an embodiment of the present invention is explained concretely. 
       FIG. 1  is a sectional view showing the CVD film-forming apparatus for forming a Ti thin film according to the embodiment of the present invention.  FIG. 2  is a plan view showing an upper portion of a showerhead of the CVD film-forming apparatus of  FIG. 1 . The film-forming apparatus  1  has a sealed chamber  2  of a substantially cylindrical shape or a box-like shape. A pedestal  3 , on which a semiconductor wafer W as an object to be processed is placed horizontally, is provided in the chamber  2 . A pedestal supporting member that protrudes downward is attached at a central bottom of the chamber  2  via a sealing ring. A cylindrical supporting member  4  joined to a bottom surface of the pedestal  3  is fixed to the pedestal supporting member  7 . The chamber  2  and the pedestal supporting member  7  have heating mechanisms not shown. An electric power source not shown supplies electric power to the heating mechanisms, so that the chamber  2  and the pedestal supporting member  7  are heated to respective predetermined temperatures. 
     A ring  5  for stabilizing generation of plasma is provided at an outside peripheral portion of the pedestal  3 . In addition, a heater  6  is embedded in the pedestal  3 . An electric power source not shown supplies electric power to the heater  6 , so that the semiconductor wafer W placed on the pedestal  3  as an object to be processed is heated to a predetermined temperature. 
     A showerhead  10  is arranged opposite to the pedestal  3  at an upper portion of the chamber  2 . The showerhead  10  has an upper plate  10   a , a middle plate  10   b  and a lower plate  10   c . The plane shape of the showerhead  10  is a circle. 
     The upper plate  10   a  has a horizontal portion  10   d  that forms a showerhead body together with the middle plate  10   b  and the lower plate  10   c , and a circular supporting portion  10   e  continued upward from on an outside periphery of the horizontal portion  10   d . The upper plate  10   a  is generally concave. As shown in  FIGS. 1 and 2 , inside the supporting portion  10   e , ribs  10   f  are arranged toward the center of the showerhead  10  at regular distance. As the ribs  10   f  are formed, while strength against heat deformation of the supporting portion  10   e  and supporting strength of the supporting portion  10   e  are enhanced, the other portion of the supporting portion  10   e  can be made thin. Thus, heat dissipation from the showerhead  10  can be inhibited. 
     Preferably, each rib  10   f  protrudes toward the center by 5 mm or more, in particular 10 mm or more. In addition, preferably, a width of each rib  10   f  is 2 mm or more, in particular 5 mm or more. In addition, preferably, the ribs  10   f  are arranged at regular distance. 
     The upper plate  10   a  serves as a base member. An upper portion of an outside periphery of the circular concave middle plate  10   b  is fixed to a lower portion of an outside periphery of the horizontal portion  10   d  of the upper plate  10   a  by means of screws. An upper surface of the lower plate  10   c  is fixed to a lower surface of the middle plate  10   b  by means of screws. A space  11   a  is hermetically formed between a lower surface of the horizontal portion  10   d  of the upper plate  10   a  and an upper surface of the middle plate  10   b  having a concave portion. A plurality of grooves are formed radially and uniformly in the lower surface of the middle plate  10   b . The middle plate  10   b  and the lower plate  10   c  are hermetically joined. A space  11   b  is formed between the plurality of grooves formed in the lower surface of the middle plate  10   b  and the upper surface of the lower plate  10   c . In the middle plate  10   b , a large number of first gas-passages  12   a , which run from the space  11   a  toward the lower plate  10   c  through a plurality of holes formed in the middle plate  10   b , and a second gas-passage  12   b , which communicates not with the space  11   a  but with the space  11   b , are formed. In the lower plate  10   c , a large number of first gas-discharging-holes  13   a , which communicate with the first gas-passages  12   a , and a large number of second gas-discharging-holes  13   b , which communicates with the space  11   b , are formed. 
     Herein, the inside diameter of each first gas-passage  12   a  formed in the middle plate  10   b  is for example 0.5 to 3 mm, preferably 1.0 to 2.0 mm. The inside diameter of each first gas-discharging-hole  13   a  formed in the lower plate  10   c  has a two-tier structure, wherein the diameter is for example φ1.0 to 3.5 mm, preferably φ1.2 to 2.3 mm, at a portion on the side of the space  11   a  and for example φ0.3 to 1.0 mm, preferably φ0.5 to 0.7 mm, at the other portion on the side of the lower opening. 
     A first gas-introducing-pipe  14   a  and a second gas-introducing-pipe  14   b  are connected to an upper surface of the upper plate  10   a . The first gas-introducing-pipe  14   a  communicates with the space  11   a . The second gas-introducing-pipe  14   b  communicates with the second gas-way  12   b  of the middle plate  10   b  and the space  11   b . Thus, a gas introduced from the first gas-introducing-pipe  14   a  is discharged out from the first gas-discharging-holes  13   a  through the space  11   a  and the first gas-passages  12   a . On the other hand, a gas introduced from the second gas-introducing-pipe  14   b  is introduced into the space  11   b  through the second gas-passage  12   b  and then discharged out from the second gas-discharging-holes  13   b . That is, the showerhead  10  is a postmix type wherein the gas supplied from the first gas-introducing-pipe  14   a  and the gas supplied from the second gas-introducing-pipe  14   b  are independently supplied into the chamber  2 . That is, the gas supplied from the first gas-introducing-pipe  14   a  and the gas supplied from the second gas-introducing-pipe  14   b  are not mixed in the showerhead  10 , and supplied separately. 
     Herein,  FIG. 7  is an enlarged view of the showerhead of  FIG. 1 . As shown in  FIGS. 1 and 7 , a sealing ring  10   h  can be interposed between a lower surface of a portion of the upper plate  10   a  surrounding a connecting portion with the second gas-introducing-pipe  14   b , which introduces the second process gas, and a flange  10   g  at a portion of the middle plate  10   b  forming the second gas-passage  12   b . Thus, it can be prevented more surely that the respective gases supplied from the first gas-introducing-pipe  14   a  and the second gas-introducing-pipe  14   b  mix with each other. 
       FIG. 8  is a sectional view taken along A-A line of  FIG. 7 , and  FIG. 9  is a sectional view taken along B-B line of  FIG. 7 . In  FIGS. 7 and 8 , a numeral sign  101  indicates bolts. The bolts  101  fasten the middle plate  10   b  and the lower plate  10   c . Arrows in  FIG. 9  indicate flow directions of gas supplied from the second gas-passage  12   b  into the space  11   b.    
     As shown in  FIGS. 7 and 9 , slits  212   b  as gas-discharging-holes are formed on right and left sides at a lower end of the second gas-passage  12   b . The direction in which the slits  212   b  are formed may be not only a right and left direction but also a vertical direction or a diagonal direction. Instead of the slits  212   b , discharging holes may be formed. The diameter of each discharging hole is preferably 1.0 to 3.0 mm, in particular 2.0 mm. The number of the discharging holes is optional. 
     On the other hand, as shown in  FIG. 1 , a flange  14  is commonly welded to respective base ends of the first gas-introducing-pipe  14   a  and the second gas-introducing-pipe  14   b , which are connected to the upper plate  10   a . An insulating member  24  including a first gas-passage  24   a  and a second gas-passage  24   b  is connected to the flange  14 . A gas introducing member  26  including a first gas-passage  26   a  and a second gas-passage  26   b  is connected to the other end of the insulating member  24 . Then, the gas introducing member  26  is connected to an upper surface of the lid member  15 . The lid member  15  and the chamber  2  have, respectively, a first gas-passage  15   a ,  2   a  and a second gas-passage  15   b ,  2   b . The first gas-passages  24   a ,  26   a ,  15   a  and  2   a  and the second gas-passages  24   b ,  26   b ,  15   b  and  2   b  from the flange  14  to the chamber  2  are, respectively, communicated in series, and sealing rings such as O-rings are interposed at connecting portions thereof. In addition, a first gas pipe  25   a  is connected to the first gas-passage  2   a  in the chamber  2 , and a second gas pipe  25   b  is connected to the second gas-passage  2   b . And the respective base ends of the gas pipes  25   a  and  25   b  are connected to a gas supplying part  30 . 
     The gas supplying part  30  has: a ClF 3  gas source  31  that supplies ClF 3  gas, which is a cleaning gas; a TiCl 4  gas source  32  that supplies TiCl 4  gas, which is a film-forming gas; an Ar gas source  33  that supplies Ar gas, which is a carrier gas; a H 2  gas source  34  that supplies H 2  gas, which is a reduction gas; and a NH 3  gas source  35  that supplies NH 3  gas, which is used for nitriding a Ti film. The ClF 3  gas source  31 , the TiCl 4  gas source  32  and the Ar gas source  33  are respectively connected to gas pipes  36 ,  37  and  38 . The gas pipes  36 ,  37  and  38  are connected to the second gas pipe  25   b . The H 2  gas source  34  and the NH 3  gas source  35  are respectively connected to gas pipes  39 ,  40 . The gas pipes  39  and  40  are connected to the first gas pipe  25   a.    
     Thus, the respective gases from the ClF 3  gas source  31 , the TiCl 4  gas source  32  and the Ar gas source  33  arrive in the second gas-passage  12   b  of the middle plate  10   b  of the showerhead  10 , through the gas pipe  25   b , the second gas-passages  2   b ,  15   b ,  26   b  and  24   b  of the above respective members and the gas-introducing-pipe  14   b . Then, the respective gases are introduced into the space  11   b , and discharged out from the second gas-discharging-holes  13   b  of the lower plate  10   c.    
     The respective gases from the H 2  gas source  34  and the NH 3  gas source  35  are introduced in the space  11   a  of the showerhead  10 , through the gas pipe  25   a , the first gas-passages  2   a ,  15   a ,  26   a  and  24   a  of the above respective members and the gas-introducing-pipe  14   a . Then, the respective gases are discharged out from the first gas-discharging-holes  13   a  of the lower plate  10   c  through the first gas-passages  12   a  of the middle plate  10   b.    
     Therefore, during a film-forming process, the TiCl 4  gas and the H 2  gas are not mixed with each other on the way to be supplied, but mixed after discharged into the chamber  2 . Plasma is generated, a predetermined reaction is produced, and a Ti film is deposited on the semiconductor wafer W. A mass-flow controller  41  and a pair of opening/closing valves  42  and  43 , between which the mass-flow controller  41  is sandwiched, are provided in each gas pipe  36 ,  37 ,  38 ,  39 ,  40  from each gas source. The gas supplying part  30  includes an N 2  gas source, another pipe, and another opening/closing valve and so on, which are not shown. In addition, for example, the gases supplied into the spaces  11   a  and  11   b  may be changed by changing the gas sources connected to the first gas-passage  26   a  and the second gas-passage  26   b , which are formed in the gas introducing member  26 . 
     A lid member  15  having an opening is mounted on an upper side of the chamber  2 . A circular insulating member  16  is mounted on an inside peripheral portion of the lid member  15 . Then, the supporting portion  10   e  of the upper plate  10   a  is supported by the insulating member  16 . An upper portion of the supporting portion  10   e  is covered by a circular insulating member  21  for the purpose of heat insulation. The insulating member  21  is supported by the lid member  15 . The insulating member  16  has an effect of electrical insulation between the showerhead  10  and the chamber  2  and an effect of heat (thermal) insulation. Sealing rings such as O-rings are respectively interposed between the chamber  2  and the lid member  15 , between the lid member  15  and the insulating member  16 , and between the insulating member  16  and the supporting portion  10   e . Thus, a sealed state is formed. 
     An inside heater  17  is arranged on an upper surface of the horizontal portion  10   d  of the upper plate  10   a , correspondingly to the whole surface of the semiconductor wafer W placed on the pedestal  3 . For example, the inside heater  17  may be formed by sandwiching a thin plate-like heater member between mica insulating plates. A circular (doughnut-like) outside heater  18 , for example a sheath heater, is fitted so as to surround an outside periphery of the inside heater  17 . ( FIG. 14  shows a structure wherein the same heater as the inside heater  17  is arranged as an outside heater.) These heaters function as elements of a showerhead-temperature controlling unit, which is explained below. 
     A space  19  is provided above the inside heater  17 . A heat insulating member  20  is arranged above the space  19 . The heat insulating member  20  may be a ceramics resin such as Al 2 O 3  or the like. The heat insulating member  20  has a cooling-gas passage  20   a  and a discharging port  20   b . A dry-air supplying pipe  61   a  for cooling an inside portion is connected to an upper portion of the cooling-gas passage  20   a . A dry-air supplying pipe  61   b  for cooling an outside portion is arranged above the supporting portion  10   e  of the upper plate  10   a . The pipe  61   b  has a pipe portion  61   c  along an inside periphery of the insulating member  21 . A large number of jetting-holes for jetting out dry air are uniformly and downwardly provided at the pipe portion  61   c . The jetted dry air is supplied into a gap between the insulating member  16  and the heat insulating member  20  and its vicinity, so as to cool the outside heater and its vicinity. 
     A power supply line  45  is connected to an upper surface of the upper plate  10   a  of the showerhead  10 . The power supply line  45  is connected to a high-frequency electric power source  47  via a matching unit  46 . Then, a high-frequency electric power is supplied from the high-frequency electric power source  47  to the showerhead  10 . Thus, a high-frequency electric field is formed, the process gas supplied into the chamber  2  is made plasma, and the film-forming reaction is promoted. 
     A circular filler  48  made of quartz is provided so as to prevent that plasma is generated around a lower portion of the showerhead  10 , especially in a space surrounded by lateral surfaces of the upper plate  10   a , the middle plate  10   b  and the lower plate  10   c , a lower surface of the insulating member  16 , a lower surface of the lid member  15  and a side wall of the chamber  2 . As shown in  FIG. 3 , the filler  48  has a concave portion  48   a  at an outside portion thereof. Convex portions  49   a  of a plurality of supporting members  49  fastened to the lid member  15  by means of screws are fitted in the concave portion  48   a  to support the filler  48 . An elastic (resilient) member  50  such as a fluoro rubber is interposed between a lateral surface of the concave portion  48   a  of the filler  48  and a lateral surface of each convex portion  49   a  of each supporting member  49 . Because of the elastic member  50 , centering of the showerhead  10  can be easily achieved and the filler  48  can be simply attached and removed. In addition, breakage of the filler  48  caused by thermal expansion and contraction can be prevented. An elastic (resilient) member  51  is interposed between the filler  48  and the lid member  15 . The elastic member  51  also has a function of preventing the breakage of the filler  48 . 
     An exhaust pipe  52  is connected to a side wall at a base portion of the cylindrical pedestal supporting member  7  attached at a base portion of the chamber  2 . An exhaust unit  53  is connected to the exhausting pipe  52 . Thus, the chamber  2  can be evacuated. A unit that traps unreacted materials and/or by-products is not shown but provided on an upstream side with respect to the exhausting unit  53 . The chamber  2  can be vacuumed to a predetermined vacuum level by driving the exhausting unit  53 . In addition, a sealed box  23  is provided over the lid member  15 . An exhausting port  54  is provided at an upper portion of the sealed box  23 . Inside heated dry air and outside heated dry air in the sealed box  23  are adapted to be exhausted from the exhausting port  54 . 
     The CVD film-forming apparatus  1  according to the embodiment has a showerhead-temperature controlling unit  60  that controls a temperature of the showerhead  10 . The showerhead-temperature controlling unit  60  is explained hereinafter. 
     As main elements, the showerhead-temperature controlling unit  60  has: the inside heater  17  and the outside heater  18 , which are described above as a heating mechanism; the dry-air supplying pipes  61   a  and  61   b  for supplying dry air as a cooling mechanism; a temperature-detecting mechanism consisting of thermocouples  65   a ,  65   b ,  66   a  and  66   b  that monitor temperatures of the inside heater  17 , the outside heater  18  and the lower plate  10   d  of the showerhead  10 ; and a controller  62  that controls the above elements. 
     As enlargedly shown in  FIG. 4 , an electric power source  63  is connected to the inside heater  17 , and an electric power source  64  is connected to the outside heater  18 . At a position corresponding to the inside heater  17  arranged at the inside portion on the upper plate  10   a  of the showerhead  10 , the thermocouple  65   a  for detecting the temperature contacts with an insulating sheet  131  of high thermal conductivity on the upper plate, and the thermocouple  65   b  contacts with the inside of the lower plate. At a position corresponding to the outside heater  18  arranged at the outside portion on the upper plate  10   a , the thermocouple  66   a  for detecting the temperature of the outside portion of the upper plate  10   a  contacts with the inside of the upper plate and the thermocouple  66   b  for detecting the temperature of the outside portion of the lower plate  10   c  contacts with the inside of the lower plate. Each thermocouple  65   a ,  65   b ,  66   a ,  66   b  may be a plurality of thermocouples. In addition, provided is an inside-temperature controller that controls the temperature by means of a PID control to the output of the inside heater  17 , based on an instruction of the controller  62  and a signal detected by the thermocouple  65   a  or  65   b , and provided is an outside-temperature controller  68  that controls the temperature by means of a PID control to the output of the outside heater  18  or the like, based on an instruction of the controller  62  and a signal detected by the thermocouple  66   a  or  66   b . Thus, when the showerhead  10  is heated, temperature control of the showerhead  10  can be achieved by the temperature controllers  67  and  68 . 
     On the other hand, the dry air supplied from the dry-air supplying pipe  61   a  is introduced into the space through the cooling-gas passage  20   a  of the heat insulating member  20 , as a cooling material. The dry air takes heat emitted from the inside heater  17  into the space  19 , flows through the exhausting port  20   b , and is exhausted from the exhausting port  54  of the sealed box  23  provided on the upper portion of the lid member  15 . The dry air supplied from the dry-air supplying pipe  61   b  is discharged out from the discharging-holes on the lower side of the pipe, takes heat in the outside portion of the showerhead including the outside heater  18  or the like, and is exhausted from the exhausting port  54  of the sealed box  23 . Air operation valves  69   a  and  69   b  are respectively provided in the dry-air supplying pipes  61   a  and  61   b . The air operation valves  69   a  and  69   b  are controlled by the controller  62 . 
     When the showerhead is heated while the showerhead controlling unit  60  is used, a preferable temperature control can be achieved in accordance with a control shown in  FIG. 5 . In the control shown in  FIG. 5 , a set temperature is set at the controller  62 . Then, the temperature controller  67  controls the output of the inside heater  17  in such a manner that a temperature detected by the thermocouple  65   a  or  65   b  coincides with the set temperature. The value detected by the thermocouple  65   a  or  65   b  is also outputted to the temperature controller  68  via the controller  62 . Then, the temperature controller  68  controls the output of the outside heater  18  in such a manner that the difference between a temperature detected by the thermocouple  66   a  or  66   b  at the position corresponding to the outside heater  18  and a temperature detected by the thermocouple  65   a  or  65   b  at the position corresponding to the inside heater  17  coincides with zero. Therefore, the temperature of the outside portion of the showerhead  10  and the temperature of the inside portion of the showerhead  10  are controlled to be substantially the same. 
     The upper surface of the upper plate  10   a  of the showerhead  10  and a portion above it are exposed to atmospheric air. The thermocouples  65   b  and  66   b  of the showerhead-temperature controlling unit  60  are arranged in the showerhead, which can be a vacuum. However, the other elements are arranged in the atmospheric air. 
     In addition, as shown in  FIG. 2 , the showerhead  10  can be inverted outwardly from the chamber  2  by an inverting mechanism  80  having a hinge mechanism. Thus, as shown in  FIG. 6 , the showerhead  10  can be positioned substantially completely outside the chamber  2  in such a manner that the gas-discharging surface is directed upward. Thus, maintenance of the showerhead  10  can be very easily conducted. Concretely, from the state shown in  FIG. 6 , the plurality of supporting members  49  can be easily taken out outwardly by removing the fastening screws (arrow ( 1 )). After the supporting members  49  are taken out, the filler  48  can be easily taken out upwardly (arrow ( 2 )). Then, after the filler  48  is taken out, maintenance of the showerhead  10  itself can be conducted. For example, the lower plate  10   c  and the middle plate  10   b  can be easily taken out upwardly (arrow ( 3 )). After the showerhead  10  is inverted, it is preferable that the showerhead  10  is held at a position inverted by 180 degrees. It is sufficient that the inverted degrees are around 180 degrees. In order to hold the showerhead  10  at such position, a gas spring or the like can be used. 
     Next, a processing operation of the CVD film-forming apparatus  1  as structured above is explained. At first, before a Ti thin film is formed on a semiconductor wafer W, a pre-coated film is formed on the surfaces of the showerhead  10  and the pedestal  3  and so on in accordance with the following steps. First, environs of the chamber  2 , the heater  6  of the pedestal  3 , and the inside and outside heaters  17  and  18  of the showerhead  10  are heated. Then, the chamber  2  is exhausted by the discharging unit  53 , a predetermined gas is introduced into the chamber  2  at a predetermined flow rate, and the inside of the chamber  2  becomes a predetermined pressure. Then, a film-forming gas, which includes H 2  gas, Ticl 4  gas and other gases, is introduced into the chamber  2  at a predetermined flow rate, and a high-frequency electric power is supplied from the high-frequency electric power source  47  to the showerhead  10 , so that plasma is generated in the chamber  2 . Thus, a Ti film is deposited on the showerhead  10  and the pedestal  3  and so on. Then, the supply of the electric power from the high-frequency electric power source  47  and the supply of the TiCl 4  gas are stopped. Then, NH 3  gas and other gases are supplied at predetermined flow rates, and again the high-frequency electric power is supplied from the high-frequency electric power source  47  to the showerhead  10 , so that plasma is generated. Thus, a surface of the deposited Ti film is nitrided, so that a stable pre-coated film is formed on the showerhead  10  and pedestal  3  and so on. After the nitriding process is completed, the supply of the electric power from the high-frequency electric power source  47  and the supply of the NH 3  gas are stopped. 
     After the pre-coating process is completed, a gate valve not shown is opened, and a semiconductor wafer W is conveyed into the chamber  2  and placed onto the pedestal  3 . Then, the H 2  gas, the Ticl 4  gas and the other gases are supplied at predetermined flow rates, and a high-frequency electric power is supplied from the high-frequency electric power source  47  to the showerhead  10 , so that plasma is generated in the chamber  2 . Thus, a Ti film is deposited on the semiconductor wafer W. Then, the supply of the electric power from the high-frequency electric power source  47  and the supply of the TiCl 4  gas are stopped. Then, the NH 3  gas and the other gases are supplied at predetermined flow rates, and again the high-frequency electric power is supplied from the high-frequency electric power source  47  to the showerhead  10 , so that plasma is generated. Thus, the Ti film deposited on the semiconductor wafer W is nitrided. After the nitriding process is completed, the supply of the electric power from the high-frequency electric power source  47  and the supply of the NH 3  gas are stopped. After the film-forming process is completed as described above, the processed semiconductor wafer W is conveyed out from the chamber  2 , another semiconductor wafer W to be successively processed is conveyed into the chamber, and the same film-forming process is conducted to the latter semiconductor wafer W. 
     After the film-forming process is conducted to a predetermined number of semiconductor wafers W, the pedestal  3  and the showerhead  10  are cooled to a predetermined temperature, and ClF 3  gas as a cleaning gas is supplied into the chamber  2  in order to conduct a cleaning process. 
     In the series of processes, in accordance with the embodiment, the following effects can be achieved because the showerhead  10  is provided with the showerhead-temperature controlling unit  60 . 
     In the pre-coating process and the film-forming process, unreacted products TiCl x  (x=1, 2, 3) may be formed. The TiCl x  has to be volatilized in order to form a stable film on the showerhead. For that purpose, a temperature not lower than 425 C.°, preferably not lower than 500° C., is necessary. As the conventional showerhead is passively heated by the heater in the pedestal, there is no certification of that the conventional showerhead is heated to or over 425° C. Thus, conventionally, there were possibilities that a stable pre-coated film may not be formed on the showerhead. However, in the embodiment, the showerhead is provided with the showerhead-temperature controlling unit  60 , so that the showerhead  10  can be actively heated to or over 425° C. In addition, by supplying a gas including the NH 3  gas so as to reduce and nitride TiCl x , a stable pre-coated film can be surely formed on the showerhead  10 . 
     In addition, when the inside of the chamber  2  is heated to a film-forming temperature, if the showerhead  10  is heated only by radiant heat from the pedestal  3  like a conventional manner, it takes a long time for the temperature of the showerhead  10  to become stable at a predetermined heating temperature. However, according to the embodiment, in addition to being passively heated by the heater  6  of the pedestal  3 , the showerhead  10  is in advance actively heated by the heaters  17  and  18  that are elements of the showerhead-temperature controlling unit  60 . Thus, within a shorter time, the whole showerhead  10  is heated, so that the temperature of a surface of the lower plate of the showerhead  10  can be stabilized to a constant temperature. Thus, the temperature in the chamber  2  can be stabilized to a predetermined temperature within a short time. As described above, as the temperature of the showerhead  10  is controlled uniformly, the Ti film can be formed uniformly on the semiconductor wafer W. Especially, when a semiconductor wafer is enlarged to 300 mm and thus the apparatus is also enlarged, the above effect is remarkable. 
     During an idling state, the high-frequency electric power source is turned off. Thus, conventionally, in order to maintain the temperature of the showerhead  10  at a predetermined temperature, the temperature of the heater in the pedestal was set higher. On the other hand, according to the embodiment, as the temperature of the showerhead  10  is controlled by the showerhead-temperature controlling unit  60 , the temperature of the showerhead  10  can be maintained and stabilized at a predetermined temperature, even during an idling state. 
     For a cleaning process, the temperature of the showerhead  10  has to be lowered from the film-forming temperature to a cleaning temperature of 200 to 300° C. Conventionally, heat-radiating performance of the showerhead was so poor that it took a long time for the temperature to fall down. However, according to the embodiment, dry air as a cooling medium is supplied to the upper portion of the showerhead  10  through the dry-air supplying pipes  61   a  and  61   b  by the showerhead-temperature controlling unit  60 , in order to cool the showerhead. Thus, the inside temperature of the chamber  2  can be fast lowered to a cleaning temperature. 
     In the unit of the embodiment, the upper part of the upper plate  10   a  of the showerhead  10  is exposed to atmospheric air. Thus, almost all the elements of the showerhead-temperature controlling unit  60  can be disposed inside atmosphere. Therefore, it is easy to handle the showerhead-temperature controlling unit  60 . 
     In addition, in the embodiment, the inside heater  17  and the outside heater  18  are provided as a heating mechanism of the showerhead-temperature controlling unit  60 , in order to achieve a two-zone control. Then, as shown in  FIG. 4 , the output of the inside heater  17  is controlled by the temperature controller  67  in such a manner that a temperature detected by the thermocouple  65   a  or  65   b  coincides with a set temperature, and the output of the outside heater  18  is controlled by the temperature controller  68  in such a manner that the difference between a temperature detected by the thermocouple  66   a  or  66   b  located correspondingly to the outside heater  18  and the temperature detected by the thermocouple  65   a  or  65   b  located correspondingly to the inside heater  17  coincides with zero, so that the inside portion and the outside portion of the showerhead  10  are controlled to be always at the same temperature. Thus, heat dissipation from the outside portion of the showerhead  10  can be inhibited, so that temperature controlling performance can be enhanced. Especially, when the size of a semiconductor wafer is enlarged to 300 mm, as heat tends to be dissipated from the outside portion of the showerhead  10 , the above two-zone control is more effective. 
     At the maintenance of the showerhead  10 , the showerhead  10  is inverted outwardly from the chamber  2  by the inverting mechanism  8 . Thus, as shown in  FIG. 6 , the maintenance of the showerhead  10  can be conducted while the gas-discharging surface of the showerhead  10  is directed upward. That is, the maintenance of the showerhead  10  can be conducted very easily. Concretely, from the state shown in  FIG. 6 , the plurality of supporting members  49  are taken out outwardly. Then, the filler  48  is taken out upwardly. Then, the lower plate  10   c  and the middle plate  10   b  of the showerhead  10  are taken out upwardly. As described above, each operation for taking-out each element is so easy that the maintenance of the showerhead  10  can be conducted very easily. 
     This invention is not limited to the above embodiment, but may be variably modified within a scope of spirit of the invention. For example, although the film-forming process of a Ti film is explained in the above embodiment, this invention is not limited thereto, but applicable to a CVD film-forming process of another film such as a TiN film. In addition, although the case wherein the plasma is generated is explained, the plasma is not necessary. The showerhead-temperature controlling unit is also not limited to the above structure. The controlling method is also not limited to the above method. For example, although the dry air is used as a cooling medium, another gas such as Ar or N 2  can be also used. If plasma is not used, liquid such as water or coolant can be used as a cooling medium. In addition, although the process to the semiconductor wafer is explained, this invention is not limited thereto, but also applicable to a process to another substrate such as a Liquid-Crystal-Display glass substrate. 
     Next, a variant of the above embodiment is explained in detail. 
     As shown in  FIG. 9 , in the above embodiment, the second gas-supplying portion  12  communicating with the second gas-passage  12   b  is arranged in the substantially central portion of the space  11   b  formed below the middle plate. The openings  12   c  are formed on the lateral sides of the gas-supplying portion  12 . Thus, the gas supplied through the second gas-passage  12   b , which communicates with the second gas-supplying pipe  14   b  and is formed above the middle plate, is discharged from the openings  12   c  of the gas-discharging portion  12  and directly diffused into the space  11   b.    
     However, according to that manner, the gas supplied through the second gas-passage  12   b  may not be sufficiently uniformly diffused into the space  11   b  of the middle plate  10   c.    
     Then, it is preferable that one or more gas-diffusion promoting pipes are connected to the openings  12   c  of the second gas-discharging portion  12  arranged in the substantially central portion of the space  11   b.    
     In the case of the middle plate  10   c  shown in  FIG. 10 , a substantially H-shaped gas-diffusion promoting pipe  110  is arranged in the space  11   b  below the middle plate  10   c  in order to uniformly diffuse the second gas. The central portion of the substantially H-shaped gas-diffusion promoting pipe  110  is connected to and fitted in the second gas-discharging portion  12 . Gas-discharging holes  110   a  are formed at four tip portions of the gas-diffusion promoting pipe  110 . The gas-diffusion promoting pipe  110  is formed integratedly by welding. Supporting pillars  110   b  that supports the gas-diffusion promoting pipe  110  are fixed to the middle plate  10   b  and the upper surface of the lower plate  10   c , in order to prevent motion of the gas-diffusion promoting pipe  110 . 
     In this case, the gas-discharging holes  110   a  formed at the respective tip portions are open toward the upper plate, so that the gas supplied through the second gas-discharging portion  12  can be sufficiently uniformly diffused into the space  11   b . Arrows in  FIG. 10  schematically show flows of the gas supplied from the gas-discharging holes  110   a  into the space  11   b . The shape, the orientation and the position of the gas-diffusion promoting pipe  110 , the number of gas-discharging holes  110   a  and the manner of openings are not limited, if the gas supplied through the second gas-passage  12   b  can be diffused sufficiently uniformly into the space  11   b . For example, the gas-discharging holes  110   a  may be formed to open to a lateral direction. The gas-discharging holes  110   a  may be formed uniformly on the way to the tip ends of the pipe, preferably uniformly in the space  11   b.    
       FIG. 11  shows a sectional view of the middle plate  10   b  attached to the lower plate  10   c  and the gas-diffusion promoting pipe  110  shown in  FIG. 10 .  FIG. 11  shows a section piercing a central pipe  110   c  of the gas-diffusion promoting pipe  110  basically, but shows a section piercing a gas-discharging hole  110   a  at a right-end portion of the gas-diffusion promoting pipe  110 . 
       FIGS. 12 and 13  show a variant regarding the control system.  FIG. 12  is a schematic view showing the variant at a portion corresponding to the heating mechanism of  FIG. 4 , and  FIG. 13  is a view showing the variant of the controlling manner of  FIG. 5 . 
     In the case shown in  FIGS. 12 and 13 , noise filters  120  are provided between the control system and the respective thermocouples  65   a ,  65   b ,  66   a  and  66   b , and between the control system and the respective heaters  17  and  18 . Preferably, they are arranged nearer to the control system. Providing the noise filters  120  like this is effective in removing noises from the high-frequency electric power source  47  to improve the controlling performance. 
     In a variant shown in  FIG. 14 , instead of the circular outside heater  18  having a circular section, a flat doughnut-like outside heater  118  is provided. Like this, the shape of the heater is not limited in particular. 
     In the variant shown in  FIG. 14 , an insulating sheet  131  is formed between the inside heater  17  and the upper plate  10   a , and an insulating sheet  132  is similarly formed between the outside heater  118  and the upper plate  10   a . The thickness of the respective insulating sheets  131  is a degree not affected by noises, for example 0.5 mm to 1.0 mm. The upper plate  10   a  functions as an electrode for generating plasma, so that the insulating sheets  131  and  132  are preferably thick in order to inhibit effects of the noises that the heaters receive. Herein, the insulating sheets  131  and  132  have to have high heat conductivity and high heat resistance. Thus, ceramics such as aluminum nitride is suitable as a material of the insulating sheets  131  and  132 . 
     In a variant shown in  FIG. 15 , instead of the elastic member  50  made of a fluorine rubber or the like, a corrosion-resisting metal spring, for example an elastic member  150  made of a Ni-alloy such as inconel, is provided. Like this, the manner of an elastic member interposed between the lateral surface of the concave portion  48   a  of the filler  48  and the lateral surface of the convex portion  49   a  of the supporting member  49  is not limited in particular. 
     Herein, regarding during the idling state and during the cleaning process, the respective features of temperature control according to this invention and prior art are shown in the following table. 
     
       
         
           
               
               
               
               
             
               
                   
                   
               
               
                   
                 Temperature 
                 Temperature of 
                   
               
               
                   
                 of showerhead 
                 pedestal 
                 Operation 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Prior art 
                 470~480° 
                 C. 
                 640~650° 
                 C. 
                 Temperature of pedestal 
               
               
                   
                   
                   
                   
                   
                 has to be raised not 
               
               
                   
                   
                   
                   
                   
                 lower than film-forming 
               
               
                   
                   
                   
                   
                   
                 temperature 
               
               
                 Invention 
                 500° 
                 C. 
                 640° 
                 C. 
                 Temperature of 
               
               
                   
                   
                   
                   
                   
                 showerhead is directly 
               
               
                   
                   
                   
                   
                   
                 controlled