Abstract:
Disclosed is a method for film formation, characterized by comprising allowing a treatment gas stream containing a metal carbonyl-containing treatment gas and a carbon monoxide-containing carrier gas to flow into a region on the upper outside of the outer periphery of a substrate to be treated in a diameter direction of the substrate while avoiding the surface of the substrate and diffusing the metal carbonyl from the treatment gas stream into the surface of the substrate to form a metal film on the surface of the substrate.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 12/933,979, filed Dec. 14, 2010, which is a U.S. national stage application of International Application No. PCT/JP2009/051088, filed on 23 Jan. 2009, which claims to Japanese Application No. JP2008-084551, filed 27 Mar. 2008, all of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention generally relates to a manufacturing of a semiconductor device, specifically, to a method for a film formation by the decomposition of a gas-state base material and a film forming apparatus. 
     BACKGROUND 
     In today&#39;s semiconductor integrated circuits, the diameter of the via plug formed with copper (Cu) inside of an insulating film between layers is reduced from 65 nm to 45 nm along with the miniaturization. It is expected that the diameter of the via plug will be further reduced to 32 nm or 22 nm in recent future. 
     As the semiconductor integrated circuits are miniaturized, it is difficult to form a bather metal film or a Cu seed layer by the conventional PVD method in a miniaturized via hole or a wiring groove in view of the step coverage. Accordingly, a film forming technology by the MOCVD method or the ALD method is studied in which an improved step coverage can be realized at a low temperature that does not damage the insulating film between layers formed with a low dielectric material (low-K material). 
     However, the MOCVD method and the ALD method generally use an organic metal as a base material where metal atoms are combined with an organic group. As a result, impurities tend to reside in the formed film, and thus, the quality of the film is not stable even if the step coverage looks satisfactory. For example, when a Cu seed layer is formed on a metal film of Ta bather by the MOCVD method, the formed Cu seed layer tends to generate a condensation thereby making it difficult to form a Cu seed layer that stably covers the Ta barrier film with a uniform film thickness. When an electrolysis plating is performed using the seed layer that generated the condensation as an electrode, potential defects may be included in the Cu layer charged at the wiring groove or the via hole. As a result, problem occurs such as the increase of the electric resistance as well as the electro-migration tolerance or a deterioration of the stress-migration tolerance. 
     Thus, a method has been recently suggested where a barrier metal film or a Cu seed layer is formed directly on the insulating film between layers by the MOCVD technology of a metal film using a metal carbonyl base material. Metal carbonyl base material is readily dissociated at a relatively low temperature to form a metal layer, and the CO, which is the ligand of metal carbonyl base material, does not reside in the formed film and immediately discharged to outside of the film forming reaction system. As a result, the barrier metal film or the Cu seed layer can be formed with a good quality having extremely low impurities. Using this method, a W film can be formed using, for example, W(C) 6 , as a barrier metal layer, or a ruthenium (Ru) film can be formed using, for example, Ru 3 (CO) 12 , as the Cu seed layer. 
     SUMMARY 
     Problems to be Solved by the Invention 
     In the mean time, since the metal carbonyl base material has a characteristic that can be easily dissociated at a relatively low temperature, a technology has been proposed where the carbon monoxide gas is supplied as a carrier gas to suppress the dissociation of the base material during the transport of the base material (base material supply system). It is known that the carbon monoxide has an effect to suppress the dissociation. 
     For example, in the technology that forms an Ru film as a Cu seed film, Ru carbonyl base material such as Ru 3 (CO) 12  is supplied to the base material supply system using CO gas as a carrier gas to suppress the dissociation of the Ru carbonyl base material during the transport procedure. 
       FIG. 1  illustrates the constitution of a film forming apparatus  10 , according to the above-described relevant technology. 
     Referring to  FIG. 1 , film forming apparatus  10  is exhausted by an exhaust system  11 , and includes a processing chamber  12  equipped with a substrate holding plate  13  that holds a substrate to be processed W. A gate valve  12 G is formed at process chamber  12  allowing the substrate to be processed W passes through. 
     A heater is embedded in substrate holding plate  13 , and the substrate to be processed W is maintained at a desired process temperature by driving the heater through a driving line  13 A. 
     Exhaust system  11  is formed with a turbo molecular pump  11 A and a dry pump  11 B connected serially, and nitrogen gas is supplied to turbo molecular pump  11 A via a valve  11   b . A variable conductance valve  11   a  is provided between process chamber  12  and turbo molecular pump  11 A to maintain the entire pressure of process chamber  12  being constant. Also, in film forming apparatus  10  of  FIG. 1 , an exhaustion path  11 C is provided configured to bypass turbo molecular pump  11 A for a rough vacuum of process chamber  12  by dry pump  11 B, a valve  11   c  is provided in exhaustion path  11 C and another valve  11   d  is provided at the downstream side of turbo molecular pump  11 A. 
     In process chamber  12 , a film forming base material is supplied with a gas state via a gas introducing line  14 B from a base material supply system  14  that includes a base material container  14 A. 
     In the illustrated embodiment, Ru 3 (CO) 12  which is the carbonyl compound of Ru is maintained in base material container  14 A, and the CO gas is provided as a carrier gas via bubble ring gas line  14   a  that includes MFC (a mass flow controller). As a result, evaporated Ru 3 (CO) 12  raw gas is supplied to process chamber  12  as a carrier gas that contains the raw gas and CO carrier gas via gas introduce line  14 B and shower head  14 S, along with the CO carrier gas from line  14   d  that includes line MFC  14   c.    
     Also, in the constitution of  FIG. 1 , along with valves  14   g ,  14   h  and MFC  14   e , a line  14   f  is provided that supplies inert gas such as Ar, and the inert gas is added to Ru 3 (CO) 12  raw gas supplied to process chamber  12  via line  14 B. 
     Also, in film forming apparatus  10 , a controller  10 A is provided to control process chamber  12 , exhaust system  11  and base material supply system  14 . 
     Also, the formation of Ru film on the substrate to be processed W is performed by Ru 3 (CO) 12 →3Ru+12CO which is the dissociation reaction of the Ru 3 (CO) 12  base material. 
     The reaction proceeds toward the right side when the partial pressure of the CO gas existing in the film forming reaction system is low. As a result, the reaction proceeds instantly as soon as the CO gas is exhausted outside of process chamber  12  thereby deteriorating the step coverage of the formed film. Due to this, the inside of process chamber  12  is maintained with a high concentration CO gas atmosphere to prevent an excessive reaction of the dissociation (Patent Literature 2). 
     However, the inventor of the present invention discovered that when film forming apparatus  10  having a conventional shower head  14 S is used as shown in  FIG. 1 , the deposition rate of the Ru film becomes non-uniform on the substrate W to be processed as shown in  FIG. 2 . More specifically, the deposition rate is higher at the center of the substrate than the periphery portion so that a distribution profile is generated regarding the deposition rate in the surface. Accordingly, as shown in  FIG. 3 , it has been discovered that the Ru film formed on the substrate to be processed W has a film thickness profile in which the thickness is thicker at the center of the substrate to be processed W and thinner at the periphery portion, and the variation of the film thickness in the surface reaches up to 15%. 
     It is noted that the results of  FIG. 2  and  FIG. 3  are based on a case where an approximately cylindrical processing chamber having an inner diameter of 505 mm is used as process chamber  12 , a silicon wafer W having a diameter of 300 mm is held on substrate holding plate  13  as the substrate to be processed W, the distance between shower head  14 S and the substrate to be processed W is set to be 18 mm, Ru 3 (CO) 12  gas is supplied with a flow rate of 1 sccm˜2 sccm as a source gas along with CO carrier gas with a flow rate of 100 sccm, and the Ru film is formed at 190° C. of substrate temperature. 
     Therefore, a technology is required to suppress the deposition rate distribution profile in the surface or film thickness distribution profile in the surface.
     Patent Literature 1: Japanese Laid-Open 2002-60944   Patent Literature 2: Japanese Laid-Open 2004-346401   

     Means to Solve the Problems 
     According to an aspect, the present invention provides a film forming method characterized by forming a metal film on the surface of the substrate to be processed. In the method, a process gas including a raw gas containing metal carbonyl and a carrier gas containing carbon-monoxide flows to the region of an upper-outer side of the diameter direction than the outer periphery of the substrate to be processed while avoiding the surface of the substrate to be processed, and the metal carbonyl is diffused into the surface of the substrate to be processed by the flow of the process gas to form the metal film. 
     According to another aspect, the present invention provides a film forming apparatus characterized by including a substrate holding plate that supports a substrate to be processed, a process chamber that defines a process space along with the substrate holding plate, and an exhaust system that exhaust the process space at the upper-outer side of the diameter direction of the substrate holding plate. The film forming apparatus further includes a process gas supply unit provided at the process chamber to face the substrate holding plate to supply the process gas formed with the raw gas and carrier gas to the process space. In particular, a process gas introduce unit is provided at the process gas supply unit in such a way that the process gas flows at the upper-outer side of the diameter direction than the substrate to be processed on the substrate holding plate when the substrate holding plate is viewed from a vertical direction, to the exhaust system in the process space while avoiding the substrate to be processed. 
     According to yet another aspect, the present invention provides a computer-readable medium characterized by storing the software that, when executed by a general purpose computer, controls a film forming apparatus. The film forming apparatus includes a substrate holding plate that supports a substrate to be processed, a process chamber that defines a process space along with the substrate holding plate, and an exhaust system that exhaust the process space at the upper-outer side of the diameter direction of the substrate holding plate. The film forming apparatus further includes a process gas supply unit provided at the process chamber to face the substrate holding plate to supply the process gas formed with the raw gas and the carrier gas to the process space. In particular, a process gas introduce unit is provided at the process gas supply unit in such a way that the process gas flows at the upper-outer side of diameter direction than the substrate to be processed on the substrate holding plate when the substrate holding plate is viewed from a vertical direction, to the exhaust system in the process space while avoiding the substrate to be processed. Moreover, the process gas supply unit is provided with metal carbonyl base material as the process gas and carbon-monoxide as a carrier gas, and the general purpose computer controls the temperature of the substrate holding plate to be lower than the temperature at which the carbon-monoxide suppresses the dissociation of the metal carbonyl. 
     Effects of the Invention 
     According to the present invention, it is possible to suppress the thickness variation of the formed film in the surface by flowing the process gas which includes a process gas and a carrier gas to the space of an upper-outer side of the diameter direction than the outer periphery of the substrate to be processed while avoiding the substrate to be processed, and performing the film formation on the surface of the substrate to be processed by diffusing the chemical species of the process gas into the surface of the substrate to be processed from the flow of the process gas. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of a CVD apparatus having a shower head used for a conventional film forming of an Ru film. 
         FIG. 2  is a graph that explains the project of the present invention. 
         FIG. 3  is a graph that explains the project of the present invention. 
         FIG. 4  illustrates a conventional film formation of the Ru film using the shower head. 
         FIG. 5  is a graph illustrating the pressure distribution and the moving fluid speed distribution of the process gas in the surface that occurs during the film formation of  FIG. 4 . 
         FIG. 6  illustrates base material distribution and film thickness distribution in the surface generated during the film formation of  FIG. 4 . 
         FIG. 7  illustrates the outline of the film formation of the Ru film according to the present invention. 
         FIG. 8  illustrates the outline of the film formation of the Ru film according to the present invention. 
         FIG. 9  illustrates the outline of the film formation of the Ru film according to the present invention. 
         FIG. 10  illustrates the outline of the film formation of the Ru film according to the present invention. 
         FIG. 11   a  is a schematic diagram of a film forming apparatus according to a first embodiment of the present invention. 
         FIG. 11   b  is a schematic diagram of a film forming apparatus according to a first embodiment of the present invention. 
         FIG. 11   c  is a schematic diagram of a film forming apparatus according to a first embodiment of the present invention. 
         FIG. 12   a  is a graph illustrating the uniformity of the deposition rate in the surface during the film forming of the Ru film according to the first embodiment. 
         FIG. 12   b  is a graph explaining the measurement of  FIG. 12   a.    
         FIG. 13  is a graph illustrating the size effect of a baffle plate in the film forming apparatus of  FIG. 11   a  through  FIG. 11   c.    
         FIG. 14  is a graph illustrating the temperature dependence of the dissociation suppression effect of the Ru carbonyl base material in the carbon monoxide atmosphere. 
         FIG. 15  is a graph illustrating the relationship between the uniformity of the Ru film thickness deposited on the substrate to be processed at various temperatures and the substrate temperature. 
         FIG. 16  is a graph illustrating the variation of the Ru film forming speed according to the temperature changes of the base material chamber. 
         FIG. 17  is a graph illustrating the variation of the Ru film forming speed according to the gas flow rate changes of the CO carrier gas. 
         FIG. 18  illustrates a modified example of the first embodiment. 
         FIG. 19  illustrates another modified example of the first embodiment. 
         FIG. 20  is a schematic diagram of a film forming apparatus according to a second embodiment. 
         FIG. 21  is a first diagram illustrating a film forming procedure using the film forming apparatus of  FIG. 20 . 
         FIG. 22  is a second diagram illustrating a film forming procedure using the film forming apparatus of  FIG. 20 . 
         FIG. 23  is a third diagram illustrating a film forming procedure using the film forming apparatus of  FIG. 20 . 
         FIG. 24  is a fourth diagram illustrating a film forming procedure using the film forming apparatus of  FIG. 20 . 
         FIG. 25  is a fifth diagram illustrating a film forming procedure using the film forming apparatus of  FIG. 20 . 
         FIG. 26  a sixth diagram illustrating a film forming procedure using the film forming apparatus of  FIG. 20 . 
         FIG. 27  is a seventh diagram illustrating a film forming procedure using the film forming apparatus of  FIG. 20 . 
         FIG. 28  is an eighth diagram illustrating a film forming procedure using the film forming apparatus of  FIG. 20 . 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Inventors of the present invention investigated, as a research on which the present invention is based, the cause of the non-uniformity of the deposition rate and film thickness in the surface as shown in  FIG. 2  or  FIG. 3  in film forming apparatus  10  using the shower head illustrated in  FIG. 1  by examining the moving fluid speed simulation, and obtained the following information. 
       FIG. 4  illustrates the simulation results of the moving fluid speed distribution of the process gas flow that occurs in the process space between shower head  14 S and the substrate to be processed W when the Ru film is deposited by film forming apparatus  10  of  FIG. 1  by supplying the process gas mentioned above from the shower head to the surface of the substrate to be processed using the conventional shower head having the same discharge holes formed at a surface that faces the substrate to be processed while exhausting from the exhausting system formed at the outer periphery of substrate holding plate  13 . Also, in the simulation results of  FIG. 4 , the lighter portion represents the gas concentration, and, accordingly represents the portion where the pressure is high. In  FIG. 4 , while the gas flow rate at each point is represented as a tiny arrow, the process gas pressure and the distribution of the moving fluid speed in the surface of the substrate to be processed W are represented as a graph in  FIG. 5  since it is difficult to represent in  FIG. 4  due to the resolution. 
     Referring to  FIG. 4 , when the gas is discharged from shower head  14 S to stage  13 , that is, when the gas is discharged from gas discharge holes  14   s  equally formed at the side of shower head  14 S that faces the substrate to be processed W disposed on substrate holding plate  13 , the discharged gas flows along the surface of the substrate to be processed to the exhaustion system of the outer periphery with a high speed. At that time, as indicated with the dotted line in the figure, the gas pressure is slightly higher near the center of the shower head to which the gas is provided from line  14 B as shown in  FIG. 5 . Also, the moving fluid speed of the process gas toward the outer periphery direction is slow at the center of the substrate to be processed. As a result, as shown in  FIG. 6 , the concentration of the base material becomes higher near the center portion of the substrate to be processed W, and corresponding to this, the film thickness is increased at the center portion of the substrate to be processed W thereby generating the film thickness distribution as shown in  FIG. 2 . 
     Meanwhile, a gas flow is formed on the surface of the substrate to be processed W along the diameter direction to the outer periphery and the moving fluid speed is increased toward the outer periphery of the substrate to be processed W, which can be known from  FIG. 4  and  FIG. 5 . In the simulation of  FIG. 4  or  FIG. 6 , a wafer having a diameter of 300 mm is used as a substrate to be processed, and shower head  14 S with a diameter of 370 mm has discharge holes  14   s  with a diameter of 6.5 mm spaced equally with 13.8 mm intervals. Also, the distance between shower head  14 S and the substrate to be processed W is set to be 18 mm, and the gas is supplied to the shower head with the flow rate of 100 sccm. 
     Based on the above knowledge, the inventors of the present invention conceived the formation of the Ru film on the substrate to be processed W as shown in  FIG. 7 , in which process gas supply member  24 S, instead of shower head  14 S, having a gas discharge opening  24   s  as a gas introduction unit at the outer side than the outer periphery of the substrate to be processed W, is used to supply the gas to the outer side than the outer periphery of the substrate to be processed W. Also, a constitution is used that exhausts from an exhaust system (not shown) formed at the outer side than the outer periphery of the substrate to be processed W to form the Ru film on the substrate to be processed W by the chemical species of the process gas diffused from the outer periphery portion to the surface of the substrate to be processed W. 
     In the constitution of  FIG. 7 , the direct supply of the gas to the surface of the substrate to be processed W is blocked by baffle unit  24 B formed at the inner side than opening  24   s  of process gas supply member  24 S, and the chemical species diffused from the gas flowing the outer periphery of the substrate to be processed W reaches the surface of the substrate W. 
     As a result, as roughly illustrated in  FIG. 8 , it appears that a uniform base material concentration is formed on the surface of the substrate to be processed W and the Ru film is formed on the substrate to be processed W with the same thickness. 
     Each of  FIG. 9  and  FIG. 10  shows the thickness distribution and deposition rate distribution, respectively, of the Ru film in the surface of the substrate when the Ru film is formed with the same film forming apparatus as used in the experiment of  FIG. 2  and  FIG. 3  but with the discharge holes of shower head  14 S are blocked except for the holes at the most outer 3 rows. It is noted that the results from  FIG. 2  and  FIG. 3  are overlapped with the results of  FIG. 9  and  FIG. 10 . 
     Referring to  FIG. 9 , by supplying the process gas to the outer side than the outer periphery of the substrate to be processed W to perform the film formation, it is confirmed that the standard deviation (σ) of the film thickness variation of the Ru film formed on the substrate to be processed W decreased to about 15% to 3% as compared to the case where shower head  14 S having equally formed discharge holes is used, and the maximum thickness difference (Δ) of the surface is decreased from 12.8 Å to 2.8 Å. Likewise, as is clear from  FIG. 10 , the deposition rate in the surface is greatly improved as compared to the case where shower head  14 S is used. 
     First Embodiment 
       FIG. 11   a  illustrates the constitution of film forming apparatus  40  according to the first embodiment of the present invention. Referring to  FIG. 11   a , film forming apparatus  40  includes an outside chamber  41  exhausted by an exhaust system (not shown), and an inside process chamber  42  formed at the inside of outside chamber  41  and is provided with an exhaust pipe  42 A at the outer periphery. Inside process chamber  42  is exhausted via outside chamber  41 . Substrate holding plate  43  is provided at the bottom portion of inner process chamber  42  to support the substrate to be processed W and carries a cover ring  43 A coupled at the periphery portion. Cover ring  43 A is coupled with the lower end portion of the outside wall of inner process chamber  42 , and inner process chamber  42  defines a closed process space  42 S. 
     Although, process space  42 S is provided with the process gas from process gas supply line  42 D, a baffle plate  42 B is provided in process space  42 S between opening  42   d  at inner process chamber  42  of process gas supply line  42 D and the substrate to be processed W on substrate holding plate  43 , as illustrated in  FIG. 11   b  and  FIG. 11   c . The supplied process gas flows to exhaust pipe  42 A through opening  42 C formed at the periphery of baffle plate  42 B. Here,  FIG. 11   b  illustrates the plan view of baffle plate  42 B, and  FIG. 11   c  is a cross-sectional view along the line B-B′ of  FIG. 11   b.    
     Referring to  FIG. 11   b  and  FIG. 11   c , baffle plate  42 B is formed with a flange unit  42 Ba which forms a portion of inner process chamber  42  and a baffle unit  42 Bb supported by a bridge unit  42 Bc. And for baffle unit  42 Bb, flange unit  42 Ba is supported at inner process chamber  42 . Flange unit  42 Ba is provided with screw holes  42 Bd to fix into inner process chamber  42 . 
     Substrate holding plate  43  includes a baffle plate  43 B which is different from baffle plate  42 B. The process gas exhausted from opening  42 C through exhaust pipe  42 A flows into the exhaustion system identical to exhaust system  11  of  FIG. 1  through opening  43   b  inside baffle plate  43 B. 
     As a result, the desired Ru film is formed by the dissociation from the reaction of the Ru 3 (CO) 12  molecules described above and diffused from the flow of the process gas that passes opening  42 C. 
     Meanwhile, when process gas supply member  24 S of  FIG. 7  is used instead of shower head  14 S in film forming apparatus  10  of  FIG. 1 , while the distribution of the thickness and the deposition rate of the formed Ru film in the surface are improved as explained in  FIG. 9  and  FIG. 10 , the deposition rate is decreased drastically as shown in  FIG. 10 . 
     Therefore, in order to improve the deposition rate without degrading the distribution of the Ru film thickness and the deposition rate in the surface, an experiment has been performed in which the diameter D of baffle plate  42 , the distance between baffle plate  42 B and the substrate to be processed W, the width C of exhaust pipe  42 A and the width A of opening  43   b  formed at baffle plate  43 B are varied to form the Ru film. Exhaust pipe  42 A and opening  43   b  are working as an iris or an aperture inserted into the exhaust system of film forming apparatus  40 . In the experiment, the Ru 3 (CO) 12  raw gas is supplied from process gas supply line  42 D with a flow rate of 1 sccm˜2 sccm along with 100 sccm of CO carrier gas, and the Ru film is formed at 190° C. of substrate temperature. 
       FIG. 12   a  illustrates the experimental results where the horizontal line represents the deposition rate and the vertical line represents the position in the surface of the substrate to be processed W. In  FIG. 12   a , the position in the surface of the substrate indicates a position along the A-A′ line of a silicon wafer having a diameter of 300 mm used as a substrate to be processed W. 
     Referring to  FIG. 12   a , “Ref” indicates the experiment of  FIG. 10 , and “I” represents a case where a disk type member having a diameter of 200 mm is used as baffle plate  42 B, the distance G is set to be 67 mm, the width C of exhaust pipe  42 A is set to be 19.5 mm, and the width A of opening  43   b  is set to be 77 mm “II” represents a case where a disk type member having a diameter of 300 mm is used as baffle plate  42 B, the distance G is set to be 67 mm, the width C of exhaust pipe  42 A is set to be 19.5 mm, and the width A of opening  43   b  is set to be 77 mm “III” represents a case where a disk type member having a diameter of 300 mm is used as baffle plate  42 B, the distance G is set to be 25 mm, the width C of exhaust pipe  42 A is set to be 19.5 mm, and the width A of opening  43   b  is set to be 77 mm “IV” represents a case where a disk type member having a diameter of 300 mm is used as baffle plate  42 B, the distance G is set to be 67 mm, the width C of exhaust pipe  42 A is set to be 2 mm, and the width A of opening  43   b  is set to be 77 mm “VI” represents a case where a disk type member having a diameter of 300 mm is used as baffle plate  42 B, the distance G is set to be 67 mm, the width C of exhaust pipe  42 A is set to be 19.5 mm, and the width A of opening  43   b  is set to be 2 mm. 
     While the average deposition rate is 3.6 Å/min and the standard deviation (σ) of the variation in the surface is 2.8% in the “Ref” experiment, the average deposition rate is 11.1 Å/min and the standard deviation (σ) of the variation in the surface is 11.6% in the experiment “I”. In the experiment “II”, the average deposition rate is 12.4 Å/min and the standard deviation (σ) of the variation in the surface is 5.0%. In the experiment “III”, the average deposition rate is 8.9 Å/min and the standard deviation (σ) of the variation in the surface is 17.7%. In the experiment “IV”, the average deposition rate is 15.0 Å/min and the standard deviation (σ) of the variation in the surface is 5.5%. In the experiment “V”, the average deposition rate is 14.9 Å/min and the standard deviation (σ) of the variation in the surface is 5.7%. In the experiment “VI”, the average deposition rate is 15.5 Å/min and the standard deviation (σ) of the variation in the surface is 5.4%. 
     Referring to  FIG. 12   a , as illustrated in  FIG. 11   a , it can be known that the deposition rate is improved by making the conductance of the exhaustion path from processing chamber  42  at exhaust pipe  42 A and opening  43   b  small. Moreover, it can be also known that the distribution of the deposition rate in the surface is improved when the diameter D of baffle plate  42 B is 300 mm which is the same as the diameter of the substrate, rather than 200 mm. 
     As described above, it is confirmed that the uniformity of the film formation on the substrate to be processed strongly depends on the diameter D of baffle plate  42 B, and the inventors of the present invention investigated the uniformity of the Ru film thickness in the surface obtained when the diameter D of baffle plate  42 B is further increased to 340 mm in film forming apparatus  40  of  FIG. 11   a  or  FIG. 11   c . The results are shown in  FIG. 13  where the horizontal line represents the position in the surface along the line A-A′ of  FIG. 12   b , and the vertical line represents the standardized thickness of the Ru film at the center portion (substrate inside position=0 mm) of the substrate to be processed W, as in  FIG. 12   a.    
     Referring to  FIG. 13 , the uniformity inside the surface is superior when the diameter D of baffle plate  42 B is 300 mm (the standard deviation of the variation of the film thickness is 5.9%) as compared to when the diameter D of baffle plate  42 B is 200 mm (the standard deviation of the variation of the film thickness is 11.6%). Specifically, when the diameter D is changed from 200 mm to 300 mm, the degree of the improvement of the uniformity in the surface is extremely large such that the standard deviation of the film thickness variation in the surface ranges from 11.6% to 5.9%. Accordingly, it can be decided that the improvement of the uniformity of the formation of the Ru film on the substrate to be processed W is more effective when the diameter of the baffle plate  42 B is larger than that of the substrate to be processed W. 
     However, as described above, in the present invention, the dissociation is suppressed during the transport of the base material by using the CO as a carrier gas during the formation of the metal film by the CVD method using the metal carbonyl base material such as Ru. Also, as in the present embodiment, in a substrate processing apparatus having an apparatus where the metal carbonyl is diffused into the center portion of the substrate to be processed W and the dissociation during the diffusion is suppressed and transported by using the carbon monoxide atmosphere, it is important to maintain the suppression effect of the dissociation of the metal carbonyl during the diffusion by the CO to perform a film formation that has an excellent characteristic of, for example, the step coverage. 
       FIG. 14  is a graph that illustrates the effect of the substrate temperature with respect to the dissociation suppression effect by the addition of the CO gas to the base material of Ru 3 (CO) 12 . In  FIG. 14 , the vertical line represents the deposition rate of the Ru film, and the horizontal line represents the substrate temperature. Also, the line I indicates the formation of the Ru film where the CO is not added to the Ru 3 (CO) 12 , and the line II indicates the formation of the Ru film from the base material of Ru 3 (CO) 12  under the CO atmosphere. 
     Referring to  FIG. 14 , it is confirmed that when the substrate temperature is below 200° C., the deposition rate of Ru 3 (CO) 12  film under the CO atmosphere is very low and the dissociation is practically suppressed. However, it is also confirmed that when the substrate temperature exceeds 200° C., the suppression effect is gradually decreased, and the effectiveness is almost lost when exceeding 230° C. Accordingly, when the temperature of the substrate to be processed W is set to be 235° C. or higher in film forming apparatus  40  of  FIG. 11   a  or  FIG. 11   c , the film is preferentially formed at the periphery of the substrate and the uniformity of the desired film formation in the surface is damaged. 
     In view of this, when a metal film is formed in film forming apparatus  40  of  FIG. 11  using the metal carbonyl base material, for example, when the Ru film is formed using Ru 3 (CO) 12  base material, it is preferable that the substrate temperature is set to be 230° C. or lower where the dissociation suppression effect of the metal carbonyl by the CO is effectively act. Also, it is more preferable to set the substrate temperature to be 200° C. or lower because the dissociation suppression effect acts sufficiently at the temperature range. Moreover, since the dissociation of Ru 3 (CO) 12  base material begins at 100° C. or higher when the CO exists, it is preferable to set the substrate temperature to be 100° C. or higher. 
     Also, the deposition rate of the Ru film on the substrate to be processed W can be improved as well by increasing the temperature of the base material container that constitute a portion of base material supply system  14  as shown in  FIG. 1 . 
       FIG. 16  is a graph that illustrates the variation of the uniformity of the deposition rate in the surface when the temperature of a base material container  14 A is changed in the film forming apparatus having the constitution of  FIG. 7  that uses process gas supply member  24 S instead of shower head  14 S in film forming apparatus of  FIG. 1 . 
     In  FIG. 16 , data “I” indicates a case where the temperature of the base material container is set to be 75° C. and corresponds to the result of prior  FIG. 10 . In contrast, data “II” is a case where a baffle plate identical to baffle plate  43 B of  FIG. 11   a  is provided around substrate holding plate  13  in the constitution of  FIG. 7 . It is confirmed that while other conditions are the same as in data “I”, the average deposition rate is increased up to 6 Å/min because the conductance of the exhaust path is reduced. In data “II”, the variation of the deposition rate of the formed Ru film in the surface is suppressed as 2% of standard deviation, and an improved uniformity in the substrate surface is achieved. 
     Also, in  FIG. 16 , data “III” indicates the distribution of the deposition rate in the surface when the maintaining temperature of base material container  14 A is set to be 85° C. in the film forming apparatus where the baffle plate is added to the constitution of  FIG. 7  based on the constitution of  FIG. 1 . As can be known from  FIG. 16 , the average deposition rate is improved 60% from 6 Å/min to 10 Å/min by increasing the maintaining temperature of base material container  14 A from 75° C. to 85° C. and maintaining other conditions to be the same. In data “III” as well, the variation of the deposition rate in the surface is suppressed by 2.6% of standard deviation to obtain an improved uniformity in the substrate surface. 
     Also, in the constitution of  FIG. 7  through  FIG. 11 , the deposition rate of the Ru film can be improved by maintaining the partial pressure of the CO gas in the process chamber and by increasing the flow rate of the CO carrier gas. 
       FIG. 17  is a graph that illustrates the uniformity of the deposition rate of the Ru film in the surface when only the flow rate of the CO carrier gas is increased from 100 sccm to 200 sccm and other conditions are maintained to be the same, in film forming apparatus  40  of  FIG. 11   a  through  FIG. 11   c    
     Referring to  FIG. 17 , it is indicated that the average deposition rate is 14.9 Å/min when the flow rate of CO carrier gas is 100 sccm. However, when the CO carrier gas flow rate increases to 200 sccm, the deposition rate increases about 30% to 19.4 Å/min Also, the variation of the deposition rate in the surface is maintained in the range of 5.5%˜5.7% of standard deviation under any circumstances and an excellent uniformity in the substrate surface is achieved. 
       FIG. 18  and  FIG. 19  each illustrates the constitution of a baffle plate  52 B as a modified embodiment of baffle plate  42 B of  FIG. 11   b.    
     Referring to  FIG. 18  and  FIG. 19 , when viewed from a vertical direction with respect to substrate holding plate  43 , baffle plate  52 B is provided with 3 rows of opening  52   b  or 2 rows of opening  52   c  positioned along the outer periphery of the substrate to be processed W corresponding to opening  42 C of  FIG. 11   a  through  FIG. 11   c . For example, it is possible to supply the process gas to the outside of outer periphery of the substrate to be processed W as in film forming apparatus  40  of  FIG. 11   a  by setting the diameter of opening  52   b  or  52   c  to be 6.5 mm and the distance to be 13.8 mm. 
     Second Embodiment 
       FIG. 20  illustrates the constitution of film forming apparatus  60  in an idling state, according to the second embodiment. Referring to  FIG. 20 , film forming apparatus  60  has a structure in which an outer chamber  62  is fixed on a base unit  61  and an inner process chamber  63  formed with a process gas introduce opening  63 A is installed to a flange unit  63 F. Outer chamber  62  corresponds to outer chamber  41  of  FIG. 11   a , and a carry in/out space  62 A for the substrate is provided at the side wall. 
     Meanwhile, inner process chamber  63  corresponds to inner process chamber  42  of  FIG. 11   a  and has a cylindrical shape. Also, process gas introduce opening  63 A is provided on the upper portion of inner process chamber  63  roughly coinciding with the central shaft. Also, a cool/heat medium path  63 B is provided in inner process chamber  63  to control the temperature. 
     The bottom portion of inner process chamber  63  is opened, and a substrate holding plate  64  corresponding to substrate holding plate  43  of  FIG. 11   a  is provided at the front end of a support unit  64 A covering the bottom portion. As a result, inner process chamber  63  along with substrate holding plate  64  defines a process space  63 S. 
     Support unit  64 A of substrate holding plate  64  is maintained by an actuator  61 A and an arm  61   a  with respect to base unit  61 , and the actuator may be either an electronic type or an oil pressure type. An up/down movement indicated as arrows is performed by driving actuator  61 A. Also, the combined portion of support unit  64 A and outer chamber  62  is sealed by a seal member  62 C that includes bellows  62   c.    
     The bottom portion of outer chamber  62  is provided with an exhaust pipe (not shown), and by connecting exhaust system  11  of  FIG. 1 , process space  63 S is exhausted through the exhaust path formed in between substrate holding plate  64  along with support unit  64 A and outer chamber  62 . 
     As shown in  FIG. 20 , a flange-type baffle unit  64 F is provided near substrate holding plate  64 , and a continuous exhaust pipe  63 C is provided in between baffle unit  64 F and the bottom portion of inner process chamber  63 . Exhaust pipe  63 C is provided continuously at an outer side than the outer periphery of the substrate to be processed W held on inner process chamber  63 . The conductance of exhaust pipe  63 C varies by moving substrate holding plate  64  into up/down direction. 
     A heater  64 H is embedded in substrate holding plate  64  and driven by the driving current from an electrode  64   h . Also, a lifter pin  64 L is formed on substrate holding plate  64  with the lower end portion  641  including a pin driving unit is fixed to a portion of outer chamber  62 . Therefore, when substrate holding plate  64  is descended by actuator  61 A, lifter pin  64 L is protruded to an upper direction than substrate holding plate  64  thereby lifting the substrate to be processed on substrate holding plate  64 . Also, a cool/heat medium path  64 B is provided at the lower part of heater  64 H inside substrate holding plate  64  to pass the cool/heat medium. 
     Also, substrate holding plate  64  includes a cover ring  64 R which is coupled to the outer periphery of the substrate to be processed held thereon. Cover ring  64 R passes through substrate holding plate  64  and extends to the lower direction. Also, cover ring  64 R includes a drive unit  64   r  which is coupled to a portion of outer chamber  62  and clears the combination with the substrate to be processed when substrate holding plate  64  descends. 
     Also, in film forming apparatus  60  of  FIG. 20 , a baffle plate  65  corresponding to baffle plate  42 B of  FIG. 11   a  is provided inside inner process chamber  63  facing the substrate to be processed on substrate holding plate  64  and with a diameter bigger than that of the substrate to be processed. Also, opening  65 A corresponding to opening  42 C of  FIG. 11   a  is provided at the outer side than the outer periphery of the substrate to be processed on substrate holding plate  64 . Baffle plate  65  includes flange unit  65 F at the outside of opening  65 A, and flange unit  65 F is fixed to the upper half body  63 U of inner process chamber  63  by screw  65   d . The lower portion of flange unit  65 F is fixed to the lower half body  63 L of inner process chamber  63  by screw  65   e . Upper half body  63 U and lower half body  63 L along with flange unit  65 F form inner process chamber  63 . 
     Also, film forming apparatus  60  of  FIG. 20  is equipped with a controller  66  formed with a general purpose computer loaded with a program to control the entire operation including the operation of actuator  61 A. 
     Next, referring to  FIG. 21  through  FIG. 28 , an exemplary process of forming the Ru film on a silicon substrate is described using film forming apparatus  60  of  FIG. 20 . 
     Referring to  FIG. 21 , actuator  61 A is driven toward the lower direction by controller  66 , and substrate holding plate  64 A is separated from inner process chamber  63  and descends. As a result, exhaust pipe  63 C is widely opened corresponding to substrate carry in/out space  62 A of outer chamber  62 . In the state of  FIG. 21 , exhaust pipe  64 C has the width of 32.3 mm in an up/down direction. In the state of  FIG. 21 , as substrate holding plate  64  descends, lifter pin  64 L protrudes from the surface of substrate holding plate  64 , and cover ring  64 R also changes its positional relationship which is separated toward the upper direction than the surface of substrate holding plate  64 . 
     Next, as illustrated in  FIG. 22 , an arm  71  of the substrate transport mechanism supporting the substrate to be processed W from substrate carry in/out space  62 A is inserted into a position between lifter pin  64 L and cover ring  64 R through the widely opened exhaust pipe  63 C, and as illustrated in  FIG. 23 , the substrate to be processed W is separated from arm  71  by driving drive unit  641  to ascend lifter pin  64 L. 
     Also, as illustrated in  FIG. 24 , arm  70  is retreated from carry in/out space  62 A and the gate valve (not shown) is closed. 
     Next, as illustrated in  FIG. 25 , actuator  61 A is driven and substrate holding plate  64  is elevated putting support unit  64 A in between, and the substrate to be processed W supported on lifter pin  64 L is supported by substrate holding plate  64 . At this state, exhaust pipe  63 C has a 10 mm width along the up/down direction. 
     Next, as illustrated in  FIG. 26 , actuator  61 A is driven by a tiny amount, and substrate holding plate  64  is elevated by a tiny amount thereby setting the width of exhaust pipe  63 C to be 8 mm Also, at this state, cover ring  64 R is combined to the side surface of the substrate to be processed W and maintained. 
     Also, in the process of  FIG. 27 , substrate holding plate  64  is elevated a little further by the driving of actuator  61 A and the distance between baffle plate  65  and the substrate to be processed W is set to be 67 mm Also, the up/down direction width of exhaust pipe  63 C is set to be 2 mm, and the process gas containing Ru 3 (CO) 12  gas and CO carrier gas is introduced from process gas introduce opening  63 A. The introduced process gas is exhausted from opening  65 A of the outer periphery of baffle plate  65  to exhaust pipe  63 C. As a result, the Ru film is deposited with an identical rate in the surface of the substrate to be processed W out of the Ru 3 (CO) 12  molecules diffused from the process gas flow, and the Ru film having an improved uniformity is deposited on the surface of the substrate to be processed W. Also, the process gas discharged from exhaust pipe  63 C is exhausted from the exhaust pipe (not shown) through exhaust path  62 B formed between outer chamber  62  and substrate holding plate  64 , or between support unit  64 A. 
     In the process of  FIG. 27 , by controlling the temperature of the substrate to be processed W with 200° C. or higher and 230° C. or lower, the preemptive Ru film deposition at the periphery of the substrate to be processed W is effectively suppressed by the CO gas and the problem of a selective deposition of the Ru film at the periphery of the substrate to be processed W, as described in  FIG. 15 , can be avoided 
     After the process of  FIG. 27 , although the description is omitted, the substrate to be processed W is taken out by arm  71  of the substrate transport mechanism, the condition of film forming apparatus  60  is returned to the condition of  FIG. 20  as illustrated in  FIG. 28 , and the inside of inner process chamber  63  is purged. 
     In the present embodiment, as for baffle plate  65 , not only the baffle plate described in  FIG. 11   b  and  FIG. 11   c  but also the baffle plate described in  FIG. 18  and  FIG. 19  may be used. 
     Also, in the present embodiment, by flowing the cool/heat medium to cool/heat medium path  63 B or  64 B, the temperature of outer chamber  62  and inner process chamber  63  can be maintained at 80° C. and the deposition of the Ru film other than the substrate to be processed W can be suppressed. 
     As can be known from the above description, the present invention is not limited to the method of the Ru film formation in which Ru 3 (CO) 12  gas is used as a base material and the CO gas is supplied along with, but may be effective to form other metal film such as W, Co, Os, Ir, Mn, Re, Mo by supplying the carbonyl base material along with the CO gas. 
     While preferred embodiments are described above, the present invention is not limited to the specific embodiments, but various modifications may be possible within the scope of the claims. 
     The present invention is based on and claims priority from Japanese Patent Application No. 2008-084551 filed on Mar. 27, 2008, the disclosure of which is incorporated herein in its entirety by reference.