Abstract:
For depositing a metallic film, the following steps are repeatedly conducted: a step in which a precoat film is formed on the inside of a chamber; a step in which two or more substrates to be treated are subjected to the deposition of a metallic film thereon by introducing each substrate into the precoated chamber, placing the substrate on the stage, feeding a treating gas while heating the substrate to generate a plasma of the treating gas, and depositing a metallic film on the substrate by plasma CVD; and a step in which after the film deposition on the substrates has been completed, a cleaning gas is introduced into the chamber to conduct dry cleaning. In the step in which two or more substrates to be treated are subjected to the deposition of a metallic film thereon, a conductive film is formed on the stage one or more times in the course of the step.

Description:
This is a U.S. national stage application of International Application No. PCT/JP2009/055885, filed on 25 Mar. 2009. Priority under 35 U.S.C. §119(a) and 35 U.S.C. §365(b) is claimed from Japanese Application No. JP2008-087652, filed 28 Mar. 2008, the disclosure of which is also incorporated herein by reference. 
     FIELD OF INVENTION 
     The present invention relates to a method of depositing a metallic film by CVD in a chamber, and memory medium. 
     BACKGROUND OF THE INVENTION 
     In manufacturing semiconductor devices, owing to the recent demands of increased miniaturization and integration, circuit configuration is getting increasingly finer. Also, according to the requirement of forming a metallic film used for an interconnection layer, a burying layer, and a contact layer etc., with a favorable step coverage, CVD (Chemical Vapor Deposition) has been selected. 
     For example, a single type plasma CVD is utilized in case of depositing Ti film with CVD to be used as a contact layer. In the single type plasma CVD, semiconductor wafers (hereinafter, wafers) each of which is a substrate to be processed is introduced into a chamber one piece at a time, and plasma is generated using, for example, TiCl 4  gas as a source gas and H 2  gas as a reduction gas, thereby forming Ti film on the wafer disposed on a stage heated to about 400° C.˜700° C. 
     For the deposition of Ti film by the single type plasma CVD, the method includes a step of repeating a cycle in which a precoating process is performed in the chamber, the deposition of Ti film is continuously performed for hundreds to thousands pieces of wafers, and then, a dry cleaning is performed by using, for example, ClF 3  gas (for example, see JP Laid Open No. 2007-165479). 
     Recently, since a fine patterning process is performed in an etching process prior to the Ti film forming process by the plasma CVD, polymer base (C—F base) residue during the etching process may be remained at the periphery portion (near the bevel) of the back side of the wafer. Also, since the ashing process and the wet cleaning process are performed with a single wafer type, these processes may not be performed sufficiently for the back side of the wafer and the wafer is introduced into the Ti film forming chamber with the polymer residue at the back side of the wafer. The polymer residue at the back side of the wafer are adhered to the high temperature susceptor (specifically to the portion corresponding to the wafer periphery) serving as the wafer stage, and be thickened during the repeated operation of the Ti film forming process, thereby making a microgap between the wafer and the wafer stage. When the high frequency electric power is applied to generate plasma at this state, an abnormal discharge may occur at an area where the microgap is produced, and there is concern that troubles in products or damage in stage may occur. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a method of depositing metallic film in which an abnormal discharge between a substrate to be processed and a stage can be suppressed. Another object of the present invention is to provide a storage medium that stores a program performing the method. 
     According to the first aspect of the present invention, there is provided a method of depositing a metallic film by plasma CVD using a film forming apparatus including a chamber configured to receive a substrate to be processed, a stage configured to dispose the substrate to be processed in the chamber, a heater configured to heat the substrate to be processed on the stage, a gas supply device configured to supply process gas for film deposition and cleaning gas into the chamber, a plasma generating device configured to generate plasma of the process gas in the chamber, and an evacuation device configured to evacuate the inside of the chamber. And, the method comprises, forming a conductive precoat film inside the chamber, the precoat film including a metal which forms the metallic film; depositing the metallic film by the plasma CVD for a plurality of substrates to be processed in which a depositing step for each of the plurality of substrates to be processed includes disposing a substrate to be processed on the stage by introducing the substrate to be processed into the chamber after the precoating, generating plasma of the process gas by supplying the process gas into the chamber while heating the substrate to be processed by the heater, and depositing the metallic film by the plasma CVD; dry cleaning the chamber by introducing the cleaning gas into the chamber, after the film deposition process for the plurality of substrates to be processed has been completed; repeating the steps of forming, depositing, and dry cleaning; and forming a conductive film on the stage one or more times during the course of the depositing process of the metallic film for the plurality of substrates to be processed. 
     For the first aspect, the formation of the precoat film may be performed by repeating the step of forming a film that includes a metal which forms the metallic film, and the step of performing a nitriding process to the film plural times. And, the formation of the conductive film may refer to forming a film that includes a metal which forms the metallic film. 
     Also, for the first aspect, the formation of the conductive film may be performed in the film deposition process for every predetermined number of substrates. In this case, it is preferred that the formation of the conductive film is performed in the film deposition process for every 1 piece to 250 pieces of substrates, and is more preferred that the formation of the conductive film is performed in the film deposition process for every 1 lot, for example, 25 pieces of substrates. 
     Moreover, the metallic film may be formed by any one of Ti, TiN, W, WN, Ta and TaN. 
     According to a second aspect of the present invention, there is provided a storage medium that stores a program which operates on a computer to control a film forming apparatus that includes a chamber configured to receive a substrate to be processed, a stage configured to dispose the substrate to be processed in the chamber, a heater configured to heat the substrate to be processed on the stage, a gas supply device configured to supply a process gas for film deposition and a cleaning gas into the chamber, a plasma generating device configured to generate plasma of the process gas in the chamber, and an evacuation device configured to evacuate the inside of the chamber. The program, when executed, repeatedly conducts steps of forming a conductive precoat film inside the chamber where the precoat film includes a metal which forms the metallic film; depositing the metallic film by the plasma CVD for a plurality of substrates to be processed in which a depositing step for each of the plurality of substrates to be processed includes disposing a substrate to be processed on the stage by introducing the substrate to be processed into the chamber after the precoating, generating plasma of the process gas by supplying the process gas into the chamber while heating the substrate to be processed by the heater, and depositing the metallic film by the plasma CVD; dry cleaning the chamber by introducing the cleaning gas into the chamber, after the film deposition process for the plurality of substrates to be processed has been completed; repeating the steps of forming, depositing, and dry cleaning; and forming a conductive film on the stage one or more times during the course of the depositing process of the metallic film for the plurality of substrates to be processed. 
     According to the present invention, a process for performing the deposition of the metallic film for plural pieces of substrates to be processed includes a step of forming the conductive film in the chamber one or more times. Thus, an abnormal discharge between the substrate and a stage may be suppressed because the formed conductive film makes the electrical charge in the substrate to flow into the stage even when the polymer gets accumulated on the stage area corresponding to the periphery portion of the substrate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross sectional view of a film deposition apparatus which is used to perform a method of depositing metallic film, according to an exemplary embodiment of the present invention. 
         FIG. 2  is a flow chart showing the process of Ti film deposition. 
         FIG. 3  is a view showing a conventional method of film deposition. 
         FIG. 4  is a view showing a mechanism in which an abnormal discharge is occurred between a wafer and a susceptor. 
         FIG. 5  illustrates the method of film deposition according to one embodiment of the present invention. 
         FIG. 6  illustrates the effect of the conductive film which is used in a method of depositing film according to the present invention. 
         FIG. 7  is a view showing Vdc and Vpp of plasma in a normal case. 
         FIG. 8  is a view showing Vdc and Vpp of plasma when an abnormal discharge is occurring. 
         FIG. 9  is a view showing the condition of depositing Ti film and the status of Vdc of case  1  using a conventional method. 
         FIG. 10  is a view showing the condition of depositing Ti film and the status of Vdc of case  2  in which a precoating process is added after the change in Vdc occurs (after film deposition of 254 pieces of substrates). 
         FIG. 11  is a view showing the condition of depositing Ti film and the status of Vdc of case  3  in which a short precoating process is added in the film deposition process for every 1 lot of 25 pieces of wafers. 
         FIG. 12  is a view showing the condition of depositing Ti film and the status of Vdc of case  4  in which a short precoating process is performed after the film deposition process for first 200 pieces of wafers, and then a short precoating process is performed in the film deposition process for every 1 lot of 25 pieces of wafers. 
     
    
    
     DETAILED DESCRIPTION OF INVENTION 
     Hereinafter, embodiments of the present invention will be described specifically with reference to the attached drawings.  FIG. 1  is a cross sectional view of a film deposition apparatus device which is used to perform the method of depositing a metallic film, according to an exemplary embodiment of the present invention. Here, a case of depositing Ti film by plasma CVD is described as an example. 
     Also, for the description hereinafter, while ml/min is used for the unit of gas flow rate, a value which is converted to a standard state is used in the present invention because the volume of gas varies extensively according to the temperature and the air pressure. Further, sccm is written in parallel because the gas flow rate converted to the standard state is represented by sccm (Standard Cubic Centimeter per Minutes) in general. The standard state in the description refers to a state of 0° C. (273.15 K) of temperature and 1 atm (101325 Pa) of air pressure. 
     A film deposition apparatus  100  is configured as a plasma CVD-Ti film deposition apparatus which deposits Ti film by CVD while generating plasma by forming a high frequency electric field at a parallel plate electrode. 
     Film deposition device  100  has a chamber  1  of an approximately cylindrical shape. A susceptor  2  formed of AlN is disposed inside chamber  1  supported by a supporting member  3  of a cylindrical shape installed at the center of the bottom portion of chamber  1 , and susceptor  2  is a stage for horizontally supporting the wafer W which is a substrate to be processed. A guide ring  4  for guiding the wafer W is installed at the outside of the peripheral edge of susceptor  2 . Also, susceptor  2  includes a heater  5  embedded therein and formed with a high melting point metal such as molybdenum, and heater  5  heats the wafer W which is a substrate to be processed to a predetermined temperature when the power is supplied by a heater power supply  6 . Electrode  8  which functions as a bottom electrode of the parallel plate electrode is installed near the surface of susceptor  2 , and electrode  8  is electrically grounded. 
     At an upper wall la of chamber  1 , a shower head  10  which also functions as an upper electrode of a parallel plate electrode is installed through an insulating member  9 . Shower head  10  is configured with an upper block body  10   a , a center block body  10   b  and a bottom block body  10   c , and shower head  10  thereby forming a disk shape. Upper block body  10   a  includes a horizontal area  10   d  which forms the main body of the shower head along with center block body  10   b  and bottom block body  10   c , and a ring shaped supporting area  10   e  extended to the top side of the outer periphery of horizontal area  10   d , thereby forming a concave shape. The entire shower head  10  is supported by ring shaped supporting area  10   e . And, discharge holes  17 ,  18  are formed alternately at bottom block body  10   c  to discharge the gas. A first gas introduce hole  11  and a second gas introduce hole  12  are formed at the top surface of upper block body  10   a . Inside upper block body  10   a , a plurality of gas paths  13  are diverged from first gas introduce hole  11 . A gas path  15  is formed at center block body  10   b , and gas path  13  is connected to gas path  15  through a connection path  13   a  which is extended horizontally. Also, gas path  15  is connected to discharge hole  17  of bottom block body  10   c . And inside upper block body  10   a , a plurality of gas paths  14  are diverged from second gas introduce hole  12 . A gas path  16  is formed at center block body  10   b , and gas path  14  is connected to gas path  16 . And, gas path  16  is connected to a connection path  16   a  which is extended horizontally inside center block body  10   b , and connection path  16   a  is connected to plurality of discharge holes  18  of bottom block body  10   c . Further, first and second gas introduce holes  11 ,  12  are connected to the gas line of a gas supply apparatus  20 . 
     Gas supply apparatus  20  includes a ClF 3  gas supply source  21  which supplies ClF 3  gas as a cleaning gas, a TiCl 4  gas supply source  22  which supplies TiCl 4  gas as a Ti compound gas, an Ar gas supply source  23  which supplies Ar gas, a H 2  gas supply source  24  which supplies H 2  gas as a reduction gas, a NH 3  gas supply source  25  which supplies NH 3  gas as a nitriding gas, and a N 2  gas supply source  26  which supplies N 2  gas. Also, ClF 3  gas supply lines  27 ,  30   b  are connected to ClF 3  gas supply source  21 , TiCl 4  gas supply line  28  is connected to TiCl 4  gas supply source  22 , Ar gas supply line  29  is connected to Ar gas supply source  23 , H 2  gas supply line  30  is connected to H 2  gas supply source  24 , NH 3  gas supply line  30   a  is connected to NH 3  gas supply source  25 , and N 2  gas supply line  30   c  is connected to N 2  gas supply source  26 , respectively. Moreover, mass flow controller  32  and two valves  31  putting mass flow controller  32  between them are installed at each of the gas line. 
     TiCl 4  gas supply line  28  extending from TiCl 4  gas supply source  22  is connected to first gas introduce hole  11 , and ClF 3  gas supply line  27  extending from ClF 3  gas supply source  21  and Ar gas supply line  29  extending from Ar gas supply source  23  are connected to TiCl 4  gas supply line  28 . Also, H 2  gas supply line  30  extending from H 2  gas supply source  24  is connected to second gas introduce hole  12 . NH 3  gas supply line  30   a  extending from NH 3  gas supply source  25 , N 2  gas supply line  30   c  extending from N 2  gas supply source  26  and ClF 3  gas supply line  30   b  extending from ClF 3  gas supply source  21  are connected to H 2  gas supply line  30 . Thus, in a process, TiCl 4  gas from TiCl 4  gas supply source  22  together with Ar gas from Ar gas supply source  23  pass through TiCl 4  gas supply line  28  and reach into shower head  10  from first gas introduce hole  11  of shower head  10 . And TiCl 4  gas and Ar gas pass through gas paths  13 ,  15  and are discharged into chamber  1  by discharge hole  17 . In the mean time, H 2  gas from H 2  gas supply source  24  passes through H 2  gas supply line  30  and reaches into shower head  10  from second gas introduce hole  12  of shower head  10 . And H 2  gas passes through gas path  14 ,  16  and is discharged into chamber  1  by discharge hole  18 . That is, shower head  10  is configured as a post mix type which supplies TiCl 4  gas and H 2  gas into chamber  1  in a completely independent manner, so that TiCl 4  gas and H 2  gas are combined and react after they are discharged. Besides, shower head  10  is not limited to the post mix type, and may be configured as a pre mix type which mixes TiCl 4  gas and H 2  gas inside shower head  10  and supplies into chamber  1 . 
     High frequency power source  34  is connected to shower head  10  through a matching device  33 , and high frequency power is supplied to shower head  10  from high frequency power source  34 . By supplying the high frequency power from high frequency power source  34 , gas supplied into chamber  1  through shower head  10  becomes plasma and the film deposition process is performed. 
     Moreover, a heater  45  for heating shower head  10  is disposed at horizontal area  10   d  of upper block body  10   a  of shower head  10 . A heater power supply  46  is connected to heater  45  to supply the power to heat shower head  10  to a desired temperature. A heat insulating member  47  is disposed at the concave area of upper block body  10   a  to improve the heating efficiency by heater  45 . 
     A circular hole  35  is formed at the central area of bottom wall lb of chamber  1 , and an evacuation room  36  is provided covering circular hole  35  and protruding toward a downward direction. An evacuation pipe  37  is connected at the side surface of evacuation room  36  and an evacuation device  38  is connected to evacuation pipe  37 . Also, the pressure of the inside of chamber  1  may be reduced to a predetermined vacuum level by operating evacuation device  38 . 
     Three (only two are shown in  FIG. 1 ) wafer support pins  39  are provided at susceptor  2  in such a way that the support pins can protrude and descend thereby supporting and elevating the wafer W, and wafer support pins  39  are supported by a support plate  40 . And, wafer support pins  39  supported by support plate  40  are elevated by a driving device  41  such as an air cylinder. 
     At the side wall of chamber  1 , carry in/out port  42  is provided for carrying in/out the wafer W between chamber  1  and a wafer transfer room (not shown) which is disposed adjacent to chamber  1 , and gate valve  43  is provided to open and close carry in/out port  42 . 
     The components that form film deposition apparatus  100  including, for example, heater power supply  6 ,  46 , valve  31 , mass flow controller  32 , matching device  33 , high frequency power supply  34  and driving device  41  are connected to a controller  50  which includes a microprocessor (computer), and are controlled by controller  50 . And, a user interface  51  such as a keyboard for an operator to perform an input operation of a command for managing film deposition apparatus  100 , or a display which visualize and display the operating condition of film deposition apparatus  100  is connected to controller  50 . Also, a memory unit  52  that stores a recipe is connected to controller  50 , where the recipe is, for example, a program for realizing various processes performed by film deposition apparatus  100  by the control of controller  50 , or a program for making each components of film deposition apparatus  100  to perform processes according to the process condition. The recipe is stored in a storage medium  52   a  inside memory unit  52 . Storage medium  52   a  may be a fixed one such as a hard disk, or a portable one such as a CDROM or a DVD. Also, the recipe may be transmitted from other devices by, for example, a dedicated line. And, if needed, a necessary recipe may be called from memory unit  52  by a command from user interface  51  and performed the recipe in controller  50 , thereby performing a desired process at film deposition device  100  under the control of controller  50 . 
     Next, an explanation will be given of a Ti film deposition method according to the present embodiment performed by film deposition apparatus  100  as described above. In the present embodiment, as shown in  FIG. 2 , precoating process (process  1 ), film deposition process (process  2 ) and dry cleaning process (process  3 ) are repeated for a predetermined number of times, and wet cleaning process (process  4 ) is performed after the repeating. 
     According to the precoating process of process  1 , the precoat film is formed inside chamber  1  by repeating the deposition of Ti film and nitriding process a plurality of times with no wafer carried into chamber  1 . 
     According to the film deposition process of process  2 , after the precoating is completed as described above, the Ti film deposition and the nitriding process are performed in chamber  1  for plural pieces of wafers W, preferably no more than 3000 pieces, for example 500 pieces of wafers W. 
     According to the dry cleaning process of process  3 , under the condition that a wafer is not existing in chamber  1 , ClF 3  gas is introduced into chamber  1  and a dry cleaning process is performed. Dry cleaning is performed by heating susceptor  2  by heater  5 , and the temperature during the dry cleaning is preferably 170° C.˜250° C. Besides, other fluorinated gases such as NF 3 , F 2  than ClF 3  may be used in the dry cleaning process. 
     According to the wet cleaning process of process  4 , the inside of chamber  1  is wet cleaned by chemicals such as ammonia at a time when the processes  1 ˜ 3  are repeated for a predetermined number of times so that the accumulated pieces of substrates that are processed become predetermined pieces, for example, 5000˜30000 pieces. 
     Next, specific explanation will be given about the process  1  and the process  2 . In the precoating process of process  1 , with no wafer being carried into chamber  1 , the inside of chamber  1  is evacuated by evacuation device  38 . And while Ar gas and N 2  gas are introduced into chamber  1 , the temperature of susceptor  2  is elevated by heater  5 . At the time when the temperature of susceptor  2  is stabilized to a predetermined temperature, TiCl 4  gas is introduced with a predetermined flow rate, and Ar gas, H 2  gas and TiCl 4  gas introduced into chamber  1  become plasma by applying the high frequency power from high frequency power supply  34 . Thus, Ti film is formed at the inside wall of chamber  1 , the inside wall of evacuation room  36 , shower head  10  and susceptor  2 . Subsequently, the supply of only TiCl 4  gas is stopped, and NH 3  gas as a nitriding gas is made to be flowing into chamber  1 . And, by applying the high frequency power at shower head  10  and making plasma of these gases, Ti film is nitrided. Ti film deposition and nitriding as above are repeated for plural times, for example,  33  times to form the precoat film. Also, Ti film of a predetermined thickness may be formed without performing the nitriding process. 
     Preferable conditions of the precoating process are as follows.
         (1) Forming Ti Film   i) High frequency power from high frequency power supply  34     Frequency: 300 kHz˜27 MHz   Power: 100 W˜1500 W   ii) Gas flow rate of TiCl 4  gas: 1˜20 ml/min (sccm)   iii) Gas flow rate of Ar gas: 100˜2000 ml/min(sccm)   iv) Gas flow rate of H 2  gas:  250 ˜ 5000  ml/min (sccm)   v) Pressure inside the chamber: 440˜4333 Pa (3˜10 Torr)   (2) Nitriding Process   i) High frequency power from high frequency power supply  34     Frequency: 300 kHz˜27 MHz   Power: 400 W˜1500 W   ii) Gas flow rate of NH 3  gas: 100˜2000 ml/min (sccm)   iii) Gas flow rate of Ar gas: 100˜2000 ml/min (sccm)   iv) Gas flow rate of H 2  gas: 250˜5000 ml/min (sccm)   v) Pressure inside the chamber: 440˜1333 Pa (3˜10 Torr)       

     In the film deposition process of process  2 , after the precoating is completed as described above, Ti film deposition and nitriding process are performed in chamber  1  for the wafer W as described below. 
     The deposition of the Ti film is performed by elevating the temperature of susceptor  2  to a predetermined temperature by heater  5  in advance, and then controlling the inside of chamber  1  to have the same atmosphere as the outside atmosphere connected through gate valve  43 . Gate valve  43  is then opened to carry the wafer W into chamber  1  through carry in/out port  42  from a wafer transfer room (not shown) which has a vacuum condition. Subsequently, like the similar procedure that forms the Ti film at shower head  10  in the precoating process, Ar gas, H 2  gas and TiCl 4  gas introduced into chamber  1  become plasma and then are reacted thereby depositing the Ti film of a predetermined thickness on the wafer W. 
     In the nitriding process after the deposition of the Ti film is completed, the supply of TiCl 4  gas stops, and H 2  gas and Ar gas are made to flow, and the inside of chamber  1  (for example, chamber wall or shower head surface) is heated to an appropriate temperature. NH 3  gas as a nitriding gas is then made to flow, and the process gases become plasma by applying the high frequency power from high frequency power supply  34  to shower head  10 . As a result, the surface of the Ti film formed on the wafer W is nitrided by the plasma of the process gas. Also, the nitriding process is not essential. 
     Preferable condition of the film deposition process is as follows.
         (1) Deposition of Ti Film   i) High frequency power from high frequency power supply  34     Frequency: 300 kHz˜27 MHz   Power: 100 W˜1500 W   ii) Temperature of susceptor  2  by heater  5 : 500° C.˜700° C.   iii) Temperature of shower head  10  by heater  45 : 300° C.˜500° C.   iv) Gas flow rate of TiCl 4  gas: 1˜20 ml/min (sccm)   v) Gas flow rate of Ar gas: 100˜2000 ml/min (sccm)   vi) Gas flow rate of H 2  gas: 250˜5000 ml/min (sccm)   vii) Pressure inside the chamber: 440˜1333 Pa (3˜10 Torr)   (2) Nitriding Process   i) High frequency power from high frequency power supply  34     Frequency: 300 kHz˜27 MHz   Power: 100 W˜1500 W   ii) Temperature of susceptor  2  by heater  5 : 500° C.˜700° C.   iii) Temperature of shower head  10  by heater  45 : 300° C.˜500° C.   iv) Gas flow rate of NH 3  gas: 100˜2000 ml/min (sccm)   v) Gas flow rate of Ar gas: 100˜2000 ml/min (sccm)   vi) Gas flow rate of H 2  gas: 250˜5000 ml/min (sccm)   vii) Pressure inside the chamber: 440˜1333 Pa (3˜10 Torr)       

     In the conventional method, as shown in  FIG. 3 , the Ti film deposition process has been performed continuously for, for example, 500˜3000 pieces of wafers W, and then the dry cleaning process has been performed. However, by this method, there are cases that the abnormal discharge occurs as more and more wafers W are processed, and this abnormal discharge increases its frequency while repeating the Ti film deposition process between the dry cleaning processes. Especially, when the accumulated number of wafers W that are processed from the wet cleaning is 3000˜5000 pieces, the occurrence of the abnormal discharge becomes noticeable. 
     The abnormal discharge is occurred when the polymer residue, adhered along the peripheral edge of the backside of the wafer W to the bevel area of the wafer W, adheres to susceptor  2  of high temperature at an area which corresponds to the peripheral edge of the wafer W. And as the number of pieces processed is increased, as shown in  FIG. 4 , the polymer residue is accumulated and a gap between the wafer W and susceptor  2  is formed, thereby generating the abnormal discharge. 
     That is, since the polymer residue is an insulator, as shown in  FIG. 4 , when the gap between the wafer W and susceptor  2  is made by the accumulation of the polymer residue at susceptor  2 , electrical charge supplied from the plasma to the wafer W does not flow through susceptor  2 . Therefore, when the wafer W is charged to a specific level, a discharging phenomenon occurs to susceptor  2 . The polymer residue accumulates on the area of susceptor  2  corresponding to the peripheral edge of the wafer W, and the wafer W supported by the polymer residue accumulated on the peripheral edge of susceptor  2  bents downward. Especially, since the discharge may occur in the closest distance by Paschen&#39;s law, the abnormal discharge may easily occur near the central area of the wafer W. 
     Accumulation of the polymer residue continues after the dry cleaning since the polymer residue is hardly removed by the dry cleaning by ClF 3  gas. And, as the accumulated number of pieces of the wafer W which have been performed wet cleaning approaches to 5000 pieces, the occurrence of the abnormal discharge becomes noticeable. 
     Therefore, in the present embodiment, a conductive film is formed between the Ti film depositions of predetermined pieces of wafers W, for example 500˜3000 pieces, and preferably 1˜250 pieces of wafers W. Specifically, as shown in  FIG. 5 , for every predetermined pieces of wafers, for example 1 lot (for example, 25 pieces), a short precoating is performed in which a Ti film depositing process and a nitriding process are performed continuously in chamber  1 . Thus, as shown in  FIG. 6 , the conductive Ti film is deposited on the surface of the accumulated polymer residue which is insulative as well as on the surface of susceptor  2 . Therefore, the accumulated charge on the wafer W can be discharged (earthed) to susceptor  2  through the Ti film when the wafer W is located on susceptor  2  thereby suppressing the discharge between the wafer W and susceptor  2 . 
     That is, when the deposition of the Ti film is continuously performed for 500˜3000 pieces of the wafers W, the insulative polymer residue continuously accumulates on susceptor  2  and becomes thick. As a result, the possibility of the wafer W to contact the conductive film reduces, and it becomes difficult for the electric charge stored in the wafer W to be released thereby increasing the chance of the abnormal discharge to be occurred. However, as in the present embodiment, the conductive film is formed in the course of the Ti film deposition of for example, 500˜3000 pieces of the wafers W, and the possibility of releasing the electrical charges from the wafer W to susceptor  2  is increased when the wafer W is loaded on susceptor  2 . As a result, the possibility of the abnormal discharge to be occurred becomes distinguishably reduced. Also, the short precoating may be performed without the nitriding process, to form the Ti film of a predetermined thickness. 
     Preferable conditions of the short precoating are as follows.
         (1) Formation of the Ti Film   i) High frequency power from high frequency power supply  34     Frequency: 300 kHz˜27 MHz   Power: 100 W˜1500 W   ii) Gas flow rate of TiCl 4  gas: 1˜20 ml/min (sccm)   iii) Gas flow rate of Ar gas: 100˜2000 (sccm)   iv) Gas flow rate of H 2  gas: 250˜5000 ml/min (sccm)   v) Pressure inside the chamber: 440˜4333 Pa (3˜10 Torr)   (2) Nitriding Process   i) High frequency power from high frequency power supply  34     Frequency: 300 kHz˜27 MHz   Power: 400 W˜1500 W   ii) Gas flow rate of NH 3  gas: 100˜2000 ml/min (sccm)   iii) Gas flow rate of Ar gas: 100˜2000 ml/min (sccm)   iv) Gas flow rate of H 2  gas: 250˜5000 ml/min (sccm)   v) Pressure inside the chamber: 440˜1333 Pa (3˜10 Torr)       

     In view of preventing the abnormal discharge, the frequency of forming the conductive film is better to be often. However, since the throughput of the film deposition process for the wafers W reduces when the frequency is too often, the frequency of forming the conductive film may be controlled appropriately between the abnormal discharge preventing effect and the throughput. And, since the abnormal discharge does not easily occur in the initial stage of the film deposition because the accumulation of the polymer residue is little in the initial stage, the Ti film deposition process may be performed in succession for, for example, 100˜200 pieces of wafers W at first, and then the formation of the conductive film (short precoating) may be performed. And then, the formation of the conductive film may be performed for every 1 lot of 25 pieces of the wafers W. 
     Next, descriptions will be made for an experimental result performed about the possibility of the occurrence of the abnormal discharge during the Ti film deposition for a plurality of wafers under variety of conditions. In the experiment, as an index of the abnormal discharge, DC bias voltage (Vdc) of electrode  8  which functions as a lower electrode of the parallel plate electrode for generating plasma is used. That is, in general case, as shown in  FIG. 7 , while Vdc is stable when forming the Ti film, Vdc varies and becomes unstable when an arcing (abnormal discharge) occurs between the wafer and the susceptor as shown in  FIG. 8 . Therefore, the occurrence of the abnormal discharge or an abnormal symptom for the occurrence of the abnormal discharge may be understood by monitoring the behavior of Vdc. Moreover, as shown in  FIG. 8 , since the peak-to-peak voltage (Vpp) of the high frequency power varies when an arcing has occurred, Vpp may also be used as an index for the abnormal discharge. 
     Case  1  shown in  FIG. 9  is a conventional method performing a continuous film deposition process (Ti deposition+nitriding process) for 500 pieces of wafers W after the precoating, and then performing the dry cleaning process. As shown in  FIG. 9 , it is confirmed that the Vdc variation after 250 pieces of the wafers W is unstable, and the abnormal discharge may easily occur. 
     Therefore, in case  2  as shown in  FIG. 10 , the precoating process has been added after the Vdc variation occurred (after the film deposition of 254 pieces). And as a result, Vdc has been temporarily stabilized. That is, it is confirmed that performing the precoating process to form the conductive film on susceptor  2  in the course of repeating the film deposition process for a plurality of wafers W is effective for preventing the abnormal discharge. However, after the precoating process, Vdc becomes unstable again when the processed pieces of the wafers W are about 420 pieces, which proves that performing the precoating process after 250 pieces of film deposition is not enough for preventing the abnormal discharge. 
     Next, in case  3  as shown in  FIG. 11 , the short precoating (1 layer of Ti film+nitriding process) has been performed in the film deposition process (Ti deposition+nitriding process) for every 1 lot of 25 pieces of the wafers W. As a result, Vdc is stable even when the accumulated number of pieces of the wafers W processed is 500 pieces, and it is confirmed that no abnormal discharge occurs. 
     Next, in case  4  as shown in  FIG. 12 , the film deposition process has been performed for the first 200 pieces of the wafers W, and then the short precoating has been performed, and then the short precoating has been performed in the film deposition process for every 1 lot of 25 pieces of wafers W. As a result, although the occurrence of the abnormal discharge may not be completely prevented since Vdc becomes somewhat unstable at the end part of the film deposition process of the first 200 pieces, Vdc becomes stable after that and it is confirmed that no abnormal discharge occurs. 
     From the above results, it is confirmed that the abnormal discharge may be clearly prevented by performing the short precoating process in the film deposition process preferably for every 250 pieces of the wafers W or less, and more preferably in the film deposition process for every 1 lot of 25 pieces of the wafers W. That is, it is confirmed that the formation of the conductive film is preferably performed for every 1˜250 pieces of the wafers, and more preferably performed for every 25 pieces of the wafers. 
     And, the film deposition condition for the wafers W (Ti film deposition+nitriding process) and the short precoating condition are as follows.
         (1) Film Deposition Condition   &lt;Ti Film Deposition&gt;   i) High frequency power from high frequency power supply  34     Frequency: 450 kHz   Power: 800 W   ii) Gas flow rate of TiCl 4  gas: 12 ml/min (sccm)   iii) Gas flow rate of Ar gas: 1600 ml/min (sccm)   iv) Gas flow rate of H 2  gas: 4000 ml/min (sccm)   v) Pressure inside the chamber: 666.7 Pa (5 Torr)   &lt;Nitriding Process&gt;   i) High frequency power from high frequency power supply  34     Frequency: 450 kHz   Power: 800 W   ii) Gas flow rate of NH 3  gas: 1500 ml/min (sccm)   iii) Gas flow rate of Ar gas: 1600 ml/min (sccm)   iv) Gas flow rate of H 2  gas: 2000 ml/min (sccm)   v) Pressure inside the chamber: 666.7 Pa (5 Torr)   (2) Short Precoating Condition   &lt;Ti Film Deposition&gt;   i) High frequency power from high frequency power supply  34     Frequency: 450 kHz   Power: 800 W   ii) Gas flow rate of TiCl 4  gas: 18 ml/min (sccm)   iii) Gas flow rate of Ar gas: 1600 ml/min (sccm)   iv) Gas flow rate of H 2  gas: 3000 ml/min (sccm)   v) Pressure inside the chamber: 666.7 Pa (5 Torr)   &lt;Nitriding Process&gt;   i) High frequency power from high frequency power supply  34     Frequency: 450 kHz   Power: 800 W   ii) Gas flow rate of NH 3  gas: 1500 ml/min (sccm)   iii) Gas flow rate of Ar gas: 1600 ml/min (sccm)   iv) Gas flow rate of H 2  gas: 2000 ml/min (sccm)   v) Pressure inside the chamber: 666.7 Pa (5 Torr)       

     Moreover, the present invention is not limited to the embodiments described above, and can be modified into various aspects. For example, although only the aspect for forming the Ti film as a metallic film has been described in the above embodiments, the above embodiments can be applied to other metallic films such as TiN, W, WN, Ta and TaN. Also, in the above embodiments, while forming the conductive film is shown by performing the short precoating in the course of the film deposition process, it is not limited thereto, and the method itself may not be important as long as the conductive film can be precoated on susceptor  2  (stage). Also, in the above embodiments, plasma has been formed by applying the high frequency power to the shower head. However, it is not limited thereto. Also, for a substrate to be processed, it is not limited to the semiconductor wafer, and the substrate to be processed may be a substrate for liquid crystal display (LCD) devices, a glass substrate, a ceramic substrate and so on.