Patent Publication Number: US-8119518-B2

Title: Noble metal barrier for fluorine-doped carbon films

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 10/567,733, filed Feb. 10, 2006, which is a National Stage Application of PCT Application No. PCT/JP2004/10484, to filed Jul. 23, 2004, and claims priority to Japanese Patent Application No. 2003-293904, filed Aug. 15, 2003. The entire contents of U.S. patent application Ser. No. 10/567,733 are incorporated herein by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The present invention generally relates to method of forming insulation films and more particularly to a film forming method of a F (fluorine)-doped carbon film, fabrication method of a semiconductor device that uses such a film formation method of fluorine-doped carbon film, a semiconductor device formed with such a method, and a substrate processing system for fabricating such a semiconductor device. 
     BACKGROUND ART 
     In recent miniaturized semiconductor devices, so-called multilayer interconnection structure is used for electrically interconnecting a vast number of semiconductor elements formed on a substrate. In a multilayer interconnection structure, a large number of interlayer insulation films, each burying therein an interconnection pattern, are laminated, and an interconnection pattern of one layer is connected to an interconnection pattern of an adjacent layer or a diffusion region in the substrate via a contact hole formed in the interlayer insulation film. 
     With such miniaturized semiconductor devices, complex interconnection patterns are formed in the interlayer insulation film in close proximity, and delay of electric signals caused by the parasitic capacitance of the interlayer insulation film becomes a serious problem. 
     Thus, with the ultra-miniaturized semiconductor devices of these days called submicron devices or sub-quarter micron devices, a copper interconnection pattern is used as the interconnection layer constituting the multilayer interconnection structure, and a F-doped silicon oxide film (SiOF film) having a specific dielectric constant of 3-3.5 is used for the interlayer insulation film in place of conventional silicon oxide film (SiO 2  film) having the specific dielectric constant of about 4. 
     However, there is a limit in the effort of reducing the specific dielectric constant as long as an SiOF film is used. With such an insulation film based on SiO 2 , it has been difficult to achieve the specific dielectric constant of less than 3.0 as is required by the semiconductor devices of the generation characterized by the design rule of 0.1 μm or later. 
     Meanwhile there are various materials called low dielectric (low-K) insulation film having a low specific dielectric constant. On the other hand, an interlayer insulation film used for the multilayer interconnection structure is required not only to have a low specific dielectric constant but also high mechanical strength and high stability against thermal anneal processing. 
     A F-doped carbon (CF) film is a promising material for the low dielectric constant insulation film for use in ultra fast semiconductor devices of the next generation in view of its sufficient mechanical strength and its capability of achieving low specific dielectric constant of 2.5 or less. 
     Generally, a F-doped carbon film has a chemical formula represented by C n F m . It is reported that such an F-doped carbon film can be formed by a parallel-plate type plasma processing apparatus or an ECR type plasma processing apparatus. 
     For example, Patent Reference 1 obtains a F-doped carbon film by using a fluorocarbon compound such as CF 4 , C 2 F 6 , C 3 F 8 , C 4 F 8 , or the like, in a parallel-plate type plasma processing apparatus as a source gas. Further, Patent Reference 2 obtains a F-doped carbon film by using a fluorinated gas such as CF 4 , C 2 F 6 , C 3 F 8 , C 4 F 8 , or the like, in an ECR-type plasma processing apparatus. 
     Patent Reference 1 
     Japanese Laid-Open Patent Application 8-83842 
     Patent Reference 2 
     Japanese Laid-Open Patent Application 10-144675 
     DISCLOSURE OF THE INVENTION 
     Problems to be Solved by the Invention 
     In conventional F-doped carbon films, there has been a problem of large leakage current. Further, there occurs degassing from the film when a conventional F-doped carbon films is heated to a temperature of about 400° C., which is used in semiconductor process. Thus, the use of such a film for the interlayer insulation film raises a serious problem of reliability for the semiconductor device. Such large leakage current and occurrence of degassing indicate that conventional F-doped carbon films contain various defects therein. 
     Further, when attempt is made to form such a F-doped carbon film by using the conventional art, there is a need of adding a hydrogen gas to the source gas in order to remove the F radicals formed as a result of dissociation of the fluorocarbon compounds, while addition of such hydrogen gas leads to the situation that the fluorine-doped carbon film thus obtained contains a large amount of hydrogen therein. In such a fluorine-doped carbon film containing large amount of hydrogen, however, there occurs release of HF in the film, while this leads to the problem of corrosion in the interconnection layer or in the insulation film. 
     Further, as noted before, an F-doped carbon film is used frequently in a multilayer interconnection structure as an interlayer insulation film in combination with copper interconnection patterns. With such a multilayer interconnection structure that uses a copper interconnection pattern, it is essential to cover the sidewall surfaces of the interconnection grooves or via-holes, in which the interconnection patterns are formed, by a barrier metal film typically of Ta, or the like, in order to block the diffusion of Cu from the interconnection patterns. When a Ta barrier metal film is deposited on the surface of the F-doped carbon film, however, there occurs a reaction between F in the F-doped carbon film and Ta in the barrier metal film and there is formed a volatile compound of TaF. It should be noted that such formation of TaF occurs particularly on the sidewall surface of the via-holes where the F-doped carbon film is exposed, while formation of TaF causes degradation in the adherence and deteriorates the reliability or lifetime of the multilayer interconnection structure. 
       FIG. 1  shows an example of the via-contact structure that uses such a conventional F-doped carbon film. 
     Referring to  FIG. 1 , there is formed an interlayer insulation film  2  of an F-doped carbon film on a low-K dielectric interlayer insulation film  1  in which a copper interconnection pattern  1 A is embedded, wherein there is formed a via-hole  2 A in the F-doped carbon film  2  so as to expose the copper interconnection pattern  1 A while using a hard mask pattern  3  formed on the F-doped carbon film  2  as a mask. 
     On the sidewall surface of the via-hole  2 A, there is exposed the F-doped carbon film constituting the interlayer insulation film  2 , wherein the foregoing sidewall surface is covered with a Ta film  4  deposited on the hard mask pattern  3  so as to cover the via-hole  2 A. With such a contact structure, a large amount of hydrogen is contained in the film as explained before, and there is a concern that F constituting the film causes a reaction with the hydrogen to form HF of corrosive nature. 
     Further, at the sidewall surface of the via-hole  2 A in which the Ta barrier film  4  makes a contact with the fresh surface of the F-doped carbon film exposed by the dry etching process, there is formed a volatile TaF as a result of the reaction with F existing on such film surface. 
     Thus, it is the general object of the present invention to provide a novel and useful film forming method, fabrication method of a semiconductor device, semiconductor device and substrate processing system, wherein the foregoing problems are eliminated. 
     A more specific object of the present invention is to provide a film forming method capable of forming highly reliable multilayer interconnection structure while using a F-doped carbon film for the interlayer insulation film. 
     According to the present invention, there is provided a film forming method, comprising the steps of: 
     forming a F-doped carbon film by using a source gas containing C and F; and 
     modifying said F-doped carbon film by radicals, 
     said source gas having a F/C ratio, defined as a ratio of a number of F atoms to a number of C atoms in said source gas molecule, wherein said F/C ratio is larger than 1 but smaller than 2. 
     Further, according to the present invention, there is provided a method of fabricating a semiconductor device, comprising the steps of: 
     depositing a F-doped carbon film on a substrate by a plasma CVD process that uses a source gas that contains C and F in a molecule thereof; 
     forming an opening in said F-doped carbon film by a dry etching process of said F-doped carbon film; and 
     covering a sidewall surface and a bottom surface of said opening by a metal film, 
     wherein there is provided, after said step of forming said opening but before said step of covering said sidewall surface and bottom surface of said opening by said metal film, a step of modifying at least said sidewall surface of said opening by radicals, 
     said source gas having a CF ratio, defined as a ratio of a number of F atoms to a number of C atoms in said source gas molecule, wherein said F/C ratio is larger than 1 but smaller than 2. 
     In another aspect, there is provided a substrate processing system, comprising: 
     a vacuum transfer chamber; 
     a first processing chamber coupled to said vacuum transfer chamber for conducing a dry etching of a fluorine-doped carbon film; 
     a second processing chamber coupled to said vacuum transfer chamber for modifying a fluorine-doped carbon film; 
     a third processing chamber coupled to said vacuum transfer chamber for conducting dry cleaning of a fluorine-doped carbon film; and 
     a fourth processing chamber coupled to said vacuum transfer chamber for conducting deposition of a metal film, 
     wherein each of said first and second processing chambers comprises: 
     a processing vessel coupled to an evacuation system and having a stage for holding a substrate to be processed; 
     a microwave window provided so as to face said substrate to be processed on said stage and constituting a part of an outer wall of said processing vessel; 
     a planar microwave antenna provided outside said processing vessel in coupling to said microwave window; 
     a first gas supply system for supplying a noble gas to an interior of said processing vessel; and 
     a second gas supply system provided in said processing vessel so as to divide a space inside said processing vessel into a first space part in which said microwave window is included and a second space part in which said stage is included, said second gas supply system being formed with an opening enabling invasion of plasma formed in said first space part into said second space part. 
     In a further aspect, there is provided a method of fabricating a semiconductor device, comprising the steps of: 
     depositing a fluorine-doped carbon film on a substrate by a plasma CVD process that uses a source gas that contains C and F in a molecule thereof; 
     forming an opening in said fluorine-doped carbon film by a dry etching process; and 
     depositing a first metal film so as to cover a sidewall surface and a bottom surface of said opening, 
     wherein there is provided, after said step of forming said opening but before said step of depositing said first metal film, a step of depositing a second metal film that forms a stable compound when reacted with F, such that said second metal film covers at least said sidewall surface and bottom surface of said opening. 
     In a further aspect, there is provided a semiconductor device, comprising: 
     a substrate; 
     a fluorine-doped carbon film formed over said substrate; 
     an opening formed in said fluorine-doped carbon film; 
     a first metal film formed so as to cover at least a sidewall surface and a bottom surface of said opening, 
     wherein there is formed, between said fluorine-doped carbon film and said first metal film, a second metal film so as to cover said sidewall surface and bottom surface of said opening, there being formed a fluoride film in said second metal film along an interface to said sidewall of said opening where said fluorine-doped carbon film is exposed. 
     By modifying an exposed surface of a F-doped carbon film, F atoms existing on the film surface are removed according to the present invention, and it becomes possible to suppress formation of volatile fluoride film at the interface, even in the case a barrier metal film, or the like, is formed on such a film surface. Thereby, it becomes possible to realize a reliable electric contact. By using a plasma CVD process that uses a microwave and characterized by low electron temperature at the time of formation of the F-doped carbon film, and further by using a source gas having an F/C ratio, defined as a ratio of F to C in the molecule, larger than 1 but less than 2, it becomes possible to achieve deposition of the desired F-doped carbon film without adding a hydrogen gas. Because the F-doped carbon film thus formed does not contain hydrogen substantially in the film, and there occurs no problem of causing corrosion in the interconnection layer or other insulation layer when used for a multilayer interconnection structure. Further, because the F-doped carbon film of the present invention is substantially free from hydrogen, the film does not undergo etching when the foregoing modification processing is conducted by using nitrogen radicals. Thereby, it becomes possible to conduct the desired modification processing stably and with good reproducibility. 
     Further, according to the present invention, it becomes possible, by way of conducting the dry etching process of the F-doped carbon film and the dry cleaning process and further the metal film deposition process by using a cluster-type substrate processing system, to conduct the process from the dry etching process to the metal film deposition process without exposing the substrate to the air, and it becomes possible to avoid absorption of water in the air to the highly reactive exposed surface of the F-doped carbon film immediately after the dry etching process. 
     Further, according to the present invention, it becomes possible, at the time of depositing a metal film such as a Ta film on a F-doped carbon film, to avoid the problem of formation of volatile compound such as TaF and the interface between the interlayer insulation film and the barrier metal film becoming unstable, by interposing a second metal film that forms a stable with the reaction with F. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram explaining the problem with a conventional fabrication process of a semiconductor device. 
         FIG. 2A  is a diagram showing the construction of a microwave plasma processing apparatus used with the present invention. 
         FIG. 2B  is another diagram showing the construction of a microwave plasma processing apparatus used with the present invention. microwave plasma processing apparatus of  FIG. 2 . 
         FIG. 3  is a diagram showing a part of the microwave plasma processing apparatus of  FIG. 2 . 
         FIG. 4A  is a diagram showing an electron temperature distribution in the microwave plasma processing apparatus of  FIG. 2 . 
         FIG. 4B  is a diagram showing an electron density distribution in the microwave plasma processing apparatus of  FIG. 2 . 
         FIG. 5A  is a first diagram showing the fabrication process of a semiconductor device according to a first embodiment of the present invention. 
         FIG. 5B  is a second diagram showing the fabrication process of a semiconductor device according to a first embodiment of the present invention. 
         FIG. 5C  is a third diagram showing the fabrication process of a semiconductor device according to a first embodiment of the present invention. 
         FIG. 5D  is a fourth diagram showing the fabrication process of a semiconductor device according to a first embodiment of the present invention. 
         FIG. 5E  is a fifth diagram showing the fabrication process of a semiconductor device according to a first embodiment of the present invention. 
         FIG. 5F  is a sixth diagram showing the fabrication process of a semiconductor device according to a first embodiment of the present invention. 
         FIG. 5G  is a seventh diagram showing the fabrication process of a semiconductor device according to a first embodiment of the present invention. 
         FIG. 5H  is an eighth diagram showing the fabrication process of a semiconductor device according to a first embodiment of the present invention. 
         FIG. 6  is a diagram showing the construction of a cluster-type substrate processing apparatus according to a second embodiment of the present invention. 
         FIG. 7  is a diagram showing the construction of another cluster-type substrate processing apparatus used with the second embodiment of the present invention. 
         FIG. 8  is a diagram showing the construction of the semiconductor device according to a third embodiment of the present invention. 
     
    
    
     BEST MODE FOR IMPLEMENTING THE INVENTION 
     First Embodiment 
       FIGS. 2A and 2B  are diagrams showing the construction of a microwave plasma processing apparatus  100  used with the first embodiment of the present invention, wherein  FIG. 2A  shows the microwave plasma processing apparatus in a cross-sectional view, while  FIG. 2B  shows the construction of a radial line slot antenna. 
     Referring to  FIG. 2A , the microwave plasma processing apparatus  100  includes a processing vessel  11  evacuated from plural evacuation ports  11 D and a stage  13  is provided in the processing vessel  11  of holding a substrate  12  to be processed. In order to achieve uniform evacuation of the processing vessel  11 , there is formed a ring-shaped space  11 C around the stage  13 . Further, the plural evacuation ports  11 D are formed in communication with the space  11 C with a uniform interval, and hence in axial symmetry to the substrate to be processed. Thereby, it becomes possible to evacuate the processing vessel  11  uniformly via the space  11 C and the evacuation ports  11 D. 
     On the processing vessel  11 , there is provided a ceramic cover plate of low-loss dielectric in the location corresponding to the substrate  12  held on the stage  13  for processing, via a seal ring  16 A as a part of the outer wall of the processing vessel  11 , such that the ceramic cover plate  17  faces the substrate  12  to be processed. 
     The cover plate  17  is seated upon a ring-shaped member provided on the processing vessel via the foregoing seal ring  16 A, while the ring-shaped member  14  is provided with a ring-shaped plasma gas passage  14 B corresponding to the ring-shaped member  14  in communication with a plasma gas supply port  14 A. Further, the ring-shaped member  14  is formed with plural plasma gas inlets  14 C communicating with the plasma gas passage  14 B in axial symmetry to the substrate  12  to be processed. 
     Thus, the plasma gas such as Ar, Kr, Xe, H 2 , and the like, supplied to the plasma gas supply port  14 A, are supplied to the inlets  14 C via the plasma gas passage  14 B and is released from the inlets  14 C to a space  11 A right underneath the cover plate  17  inside the processing vessel  11 . 
     On the processing vessel  11 , there is further provided, over the cover plate  17 , a radial line slot antenna  30  having a radiation plane shown in  FIG. 2B  with a separation of 4-5 mm from the cover plate  17 . 
     The radial line slot antenna  30  is seated upon the ring-shaped member  14  via a seal ring  16 B and is connected to an external microwave source (not shown) via a coaxial waveguide  21 . Thereby, the radial line slot antenna excites the plasma gas released to the space  11 A by the microwave from the microwave source. 
     The radial line slot antenna  30  comprises a flat, disk-shaped antenna body  22  connected to an outer waveguide  21 A of the coaxial waveguide  21  and a radiation plate  18  formed on an opening of the antenna body  22  and formed with a large number of slots  18   a  and slots  18   b  perpendicular thereto as showing in  FIG. 2B , wherein a phase retardation plate  19  of a dielectric plate of constant thickness is inserted between the antenna body  22  and the radiation plate  18 . Further, a central conductor  21 B of the coaxial waveguide  21  is connected to the radiation plate  18 , and a cooling block  20  including a coolant passage  20 A is provided on the antenna body  22 . 
     With the radial line slot antenna  20  of such a construction, the microwave fed from the coaxial waveguide  21  spreads as it is propagated in the radial direction between the disk-shaped antenna body  22  and the radiation plate  18  and thereby experiences wavelength compression as a result of the action of the phase retardation plate  19 . Thus, by forming the slots  18   a  and  18   b  in a concentric manner in correspondence to the wavelength of the microwave propagating in the radial direction, it becomes possible to radiate a plane wave of circular polarization in a direction substantially perpendicular to the radiation plate  18 . 
     By using such a radial line slot antenna  30 , there is formed uniform high-density plasma in the space  11 A right underneath the cover plate  17 . Because the high-density plasma thus formed is characterized by low electron temperature, and because of this, there is caused little damages in the substrate  12  to be processed. Further, there is caused no metal contamination originating from the sputtering of the chamber wall of the processing vessel  11 . 
     With the plasma processing apparatus  100  of  FIGS. 2A and 2B , there is formed a conductive structure  24  inside the processing vessel  11  between the cover plate  17  and the substrate  12  to be processed such that the conductive structure is formed with a large number of nozzles  24 B that release a processing gas supplied from an external processing gas source (not shown) via the processing gas passages  23  and  24 A formed in the processing vessel  11 , where each of the nozzles  24 B releases the processing gas thus supplied to a space  11 B between the conductive structure  24  and the substrate  12  to be processed. Thus, the conductive structure  24  functions as a processing gas supplying part. Thereby, it should be noted that the conductive structure  24  constituting the processing gas supplying part is formed with openings  24 C between adjacent nozzles  24 B and  24 B as shown in  FIG. 3  with a size that allows efficient passage of the plasma formed in the space  11 A to the space  11 B by way of diffusion. 
       FIG. 3  shows the processing gas supplying part  24  in a bottom view. 
     As can be seen from  FIG. 3 , the nozzles  24 B are formed at the side of the processing gas supplying part  24  facing the substrate  12 , not in the side that faces the cover plate  17 . 
     Thus, the processing gas released from the processing gas supplying part  24  to the space  11 B in the plasma processing apparatus  100  of  FIGS. 2A  and  2 B via the nozzles  24 B is excited by the high density plasma formed in the space  11 A, and a uniform plasma processing is conducted on the substrate  12  to be processed efficiently at high speed, without damaging the substrate and the device structure on the substrate, and without contaminating the substrate. On the other hand, the microwave radiated from the radial line slot antenna  30  is blocked by the processing gas supplying part  24  of a conductive body and there occurs no damaging of the substrate  12  to be processed by the microwave thus emitted from the radial line slot antenna  30 . 
     With the substrate processing apparatus of  FIGS. 2A and 2B , the spaces  11 A and  11 B constitutes the processing space, wherein, in the case the processing gas supplying part  24  of  FIG. 3  is provided, excitation of plasma occurs primarily in the space  11 A and film formation by the processing gas takes place primarily in the space  11 B. 
       FIG. 4A  shows the distribution of the electron temperature formed in the processing space of the plasma processing apparatus of  FIGS. 2A and 2B  that includes the space  11 A and  11 B, for the case the processing pressure in the processing vessel  11  is set to about 67 Pa (0.5 Torr) by introducing an Ar gas from the plasma gas inlet  14 C and by feeding a microwave of 2.45 GHz or 8.3 GHz to the radial line slot antenna  30  with the power density of 1.27 W/cm 2 . In  FIG. 4A , it should be noted that the vertical axis represents the electron temperature while the horizontal axis represents the distance as measured from the bottom surface of the cover plate. 
     Referring to  FIG. 4A , the electron temperature becomes maximum in the region immediately underneath the cover plate  17  and takes the value of about 2.0 eV in the case the microwave frequency is 2.45 GHz and the value of about 1.8 eV in the case the microwave frequency is 8.3 GHz, while, in the so-called diffusion plasma region separated from the cover plate  17  by 20 mm or more, it can be seen that the electron temperature is generally constant and takes the value of 1.0-1.1 eV. 
     Thus, with the microwave plasma processing apparatus  100 , it is possible to form the plasma of extremely low electron temperature, and it becomes possible to conduct the process that requires low energy by using such plasma of low electron temperature. 
       FIG. 4B  shows the distribution of the plasma electron density caused in the processing vessel  11  in the plasma processing apparatus  100  of  FIGS. 2A and 2B . 
     Referring to  FIG. 4B , the illustrated example is the result for the case the processing pressure in the processing vessel  11  is set to about 67 Pa (0.5 Torr) by introducing an Ar gas from the plasma gas inlet  14 C and a microwave of 2.45 GHz or 8.3 GHz is fed to the radial line slot antenna  30  with the power density of 1.27 W/cm 2 , wherein it can be seen that a very high plasma density of 1×10 12  cm −2  is realized up to the distance of 60-70 mm from the bottom surface of the cover plate  17  in any of the case in which the frequency is 2.45 GHz and the case in which the frequency is 8.3 GHz. 
     Thus, with the present embodiment, it is possible to form a F-doped carbon film on the substrate  12  to be processed, by setting the position of the processing gas inlet  24  at the distance within 60 mm from the bottom surface of the cover plate  17  such that the foregoing plasma electron density of 1×10 12  cm −2  is realized and further by exciting the plasma in the processing vessel  11 A by introducing the Ar gas from the plasma gas inlet  14 C and by feeding the microwave of 1-10 GHz from the antenna, and further by introducing a C 5 F 8  gas to the processing space  11 B from the processing gas inlet  24  in this state. 
       FIGS. 5A-5H  are the diagrams showing the fabrication process of a semiconductor device according to a first embodiment of the present invention. 
     Referring to  FIG. 5A  there is formed a cap layer  43  of an SiN film or SiOC film on the Si substrate  41 , on which an insulation film  42  of SiO 2 , SiOC, or other low-K dielectric film is formed, and a F-doped carbon film  44  is formed on the cap layer  43  in the plasma processing apparatus  100  explained with reference to  FIGS. 2A and 2B  by introducing a C 5 F 8  source gas to the processing space  11 B from the processing gas supplying part  24 . Such deposition of the F-doped carbon film  44  can be conducted by setting the substrate temperature to 250° C. and by supplying an Ar gas to the space  11 A right underneath the cover plate  17  from the plasma gas supplying part  14 C under the pressure of about 100 Pa and further by supplying the microwave of the frequency of 2.45 GHz from the radial line slot antenna  30  with the power density of 2.0 W/cm 2 . In the illustrated example, an interconnection pattern  42 A of Cu, or the like, is embedded in the low-K insulation film  42 . 
     In the case of forming a F-doped carbon film  44  by a plasma CVD process that uses an ordinary plasma processing apparatus of parallel plate type (CCP type) or ICP type, there is a need of adding a hydrogen gas for removing the F radicals formed as a result of dissociation of the source gas molecules from the system, and thus, it is inevitable that the obtained F-doped carbon film contains a large amount of hydrogen. Contrary to this, in the case of causing dissociation of fluorocarbon source having the F/C ratio, defined as the ratio of the number of F atoms to the number of C atoms in a molecule, is larger than 1 but less than 2, such as the C5F8 source gas, in the plasma processing apparatus of  FIGS. 2A and 2B  by the microwave supplied from the radial line slot antenna  30 , it is possible to form a desired F-doped carbon film  44  without adding a hydrogen gas. Thus, the F-doped carbon film  44  formed in such a manner is a film substantially free from hydrogen. 
     After forming the F-doped carbon film  44  in this way, the step of  FIG. 5B  is conducted next, in which a hard mask film  45  of SiCN, SiN or SiO 2  is formed on the F-doped carbon film  44  by using the same plasma processing apparatus  100 . Further, in the step of  FIG. 5C , a resist pattern  46  having an opening  46 A is formed on the hard mask film  45  by an ordinary photolithographic process. In the case of forming the hard mask film  45  by an SiCN film in the plasma processing apparatus  100 , trimethyl silane is supplied from the processing gas supplying part  24  to the processing space  11 B as a source gas, and plasma containing nitrogen radicals is excited by supplying an Ar gas and a nitrogen gas to the space  11 A right underneath the cover plate  17  from the plasma gas supplying part  14 C. In a typical example, deposition of such an SiCN film  45  can be conducted by setting the substrate temperature to 350° C. and supplying the microwave of the 2.54 GHz frequency from the radial line slot antenna  30  under the pressure of about 200 Pa with the power density of 1.0 W/cm 2 . 
     Further, in the step of  FIG. 5C , a hard mask pattern  45 A is formed by patterning the hard mask layer  45  while using the resist pattern  46  as a mask, and in the step of  FIG. 5D , the F-doped carbon film  44  underneath the hard mask pattern  45  is patterned while using the hard mask pattern  45 A as a mask. As a result, there is formed an opening corresponding to the resist opening  46 A in the F-doped carbon film  44  such that the interconnection layer  42 A is exposed at the bottom of the opening  44 A. 
     With the present embodiment, the structure of  FIG. 5D  is introduced again into the plasma processing apparatus  100  of  FIGS. 2A and 2B  in the step of  FIG. 5E , and nitrogen radicals N* are formed by introducing a mixed gas of Ar and nitrogen into the space  11 A right underneath the cover plate  17  from the plasma gas inlet  14 C. 
     With the step of  FIG. 5E , the nitrogen radicals N* thus formed are used to process the substrate  41  in the processing space  11 B, such that there is caused decoupling of the F atoms existing on the surface of the F-doped carbon film  44  exposed at the sidewall surface of the opening  44 A. Further, as a result of such nitrogen radical processing, there is a possibility that a modified layer is formed on the exposed surface of the F-doped carbon film  44  by coupling of nitrogen. 
     After the step of  FIG. 5E , a Ta film  47  is formed on the structure of  FIG. 5E  in the step of  FIG. 5F  with the present embodiment as a barrier metal film, such that the Ta film  47  covers the surface of the hard mask film  45  and the exposed sidewall surface of the F-doped carbon film  44  and the surface of the interconnection pattern exposed at the bottom of the opening  44 A continuously. 
     Because the F atoms are removed from the surface of the F-doped carbon film  44  exposed at the sidewall surface of the opening  44 A in the step of  FIG. 5E  with the present embodiment, there occurs no substantial formation of volatile TaF even in the case the Ta film  47  is formed so as to cover the sidewall surface, and the Ta film  47  has excellent adherence. Further, because the F-doped carbon film is substantially free from hydrogen, release of HF from the film  44  is suppressed also effectively. 
     Meanwhile, in the case the conventional F-doped carbon film is processed by the nitrogen radicals as in the step of  FIG. 5E , it is common that there occurs severe etching, and it is extremely difficult to conduct a modification process, while there is a possibility that this problem is caused by the reaction of the hydrogen contained in the F-doped carbon film with the nitrogen radical to form an N—H group. Contrary to this, the F-doped carbon film of the present invention is film substantially free from hydrogen, and no such a problem takes place. 
     After the step of  FIG. 5F , a Cu layer  48  is formed on the structure of  FIG. 5D  in the step of  FIG. 5G  typically by a seed layer forming process conducted by a CVD process and an electrolytic plating process so as to film the opening  44 A. Further, in the step of  FIG. 5H , a part of the Cu layer  48  including the barrier metal film  47  and the hardmask film  45  is removed, and a structure is obtained such that a Cu pattern  48 A constituting a Cu interconnection pattern or plug is formed in the F-doped carbon film  44  via a Ta barrier metal film  47 . 
     As explained before, the structure thus obtained is stable and highly reliable contact is realized. 
     Second Embodiment 
     In the first embodiment of the present invention explained before, there is a need of conducting a cleaning process after the dry etching process of  FIG. 5D  for removing impurities deposited on the sidewall surface of the opening  44 A, and thus, the cleaning process has been conducted by taking out the structure from the dry etching apparatus. 
     However, in the case the cleaning process of the structure of  FIG. 5D  is conducted in the air, water vapor in the air is adsorbed upon the sidewall surface of the opening  44 A, and there is a possibility that formation of HF is caused. 
     Thus, with the present embodiment, all the process steps from  FIG. 5D  to  FIG. 5F  are conducted by using a cluster-type substrate processing system  60  shown in  FIG. 6 . 
     Referring to  FIG. 6 , the cluster-type substrate processing apparatus  60  comprises a vacuum transfer chamber  61  coupled with a load-lock chamber  62  for loading in and out a substrate and provided with a transfer robot therein, a dry etching chamber  63  coupled to the vacuum transfer chamber  61 , a modification processing chamber  64  coupled to the vacuum transfer chamber  61  and conducing modification processing of  FIG. 5E , a sputtering chamber  65  coupled to the vacuum transfer chamber  61  and conducting deposition of Ta film of  FIG. 5F , and a cleaning chamber  66  coupled to the vacuum transfer chamber  61  and conducting dry cleaning to the structure of  FIG. 5D , wherein each of the dry etching chamber  63  and the modification chamber  64  is provided with a plasma processing apparatus  100  of the construction identical to the one explained with reference to  FIGS. 2A and 2B . 
     Thus, after the step of  FIG. 5C , the substrate  41  is introduced, after removing the resist pattern  46  by an ashing process, or the like, from the load-lock chamber  62  to the dry etching chamber  63  via the vacuum transfer chamber  61 , and the dry etching process of  FIG. 5D  is conducted. 
     With this dry etching process, an Ar gas is introduced into the space  11 A from the plasma gas inlet  14 C and an etching gas such as N 2 +H 2  is introduced into the processing space  11 B from the processing part  24  in the plasma processing apparatus  100  provided in the dry etching chamber  63 , and the desired dry etching is conducted by introducing a microwave to the space  11 A from the radial line slot antenna  30  via the microwave window  17  while applying a high frequency bias to the stage  13  from the high frequency source  13 A. 
     After the dry etching process of  FIG. 5D , the substrate  41  under processing is transported to the modification chamber  64  via the vacuum transfer chamber  61 , and the modification processing of  FIG. 5E  is conducted. 
     With this modification processing, an Ar gas and a nitrogen gas are introduced into the space  11 A from the plasma gas inlet  14 C with the plasma processing apparatus  100  provided in the modification chamber  64 , and the modification processing of  FIG. 5E  is conducted by introducing a microwave to the space  11 A via the microwave window  17  from the radical line slot antenna  30 . 
     Further, after the modification processing of  FIG. 5E , the substrate  41  under processing is transferred to the dry cleaning chamber  66  via the vacuum transfer chamber  61 , and a dry cleaning processing is conducted by using NF 3 , F 2 , CO 2  or a chlorofluorocarbon family gas. 
     The substrate  41  thus completed with the dry cleaning processing in the processing chamber  66  is further forwarded to the sputtering processing chamber  65  via the vacuum transfer chamber  61 , and the Ta barrier metal film  47  is formed by the process of  FIG. 5F . 
     After the step of  FIG. 5F , the substrate  41  under processing is returned to the load-lock chamber  62  via the vacuum transfer chamber  61 . 
       FIG. 7  shows the construction of another cluster-type substrate processing system  80  that is used together with the substrate processing system  60  of  FIG. 6  for formation of the cap film  43 , the F-doped carbon film  44  and the hard mask film  45 . 
     Referring to  FIG. 7 , the cluster-type substrate processing apparatus  80  comprises a vacuum transfer chamber  81  coupled with a load-lock chamber  82  for loading in and out a substrate and provided with a transfer robot therein, a deposition chamber  83  coupled to the vacuum transfer chamber  81  and used for the formation of the cap film  43 , a deposition chamber  84  coupled to the vacuum transfer chamber  81  and used for the formation of the F-doped carbon film  44 , and a deposition chamber  85  coupled to the vacuum transfer chamber  81  and used for formation of the hard mask film  45 , wherein each of the deposition chambers  83 ,  84  and  85  is provided with the plasma processing apparatus  100  identical in construction with that explained with reference to  FIGS. 2A and 2B . 
     Thus, after formation of the insulation film  42  and the interconnection pattern  42 A, the substrate  41  under processing is transported to the deposition chamber from the load-lock chamber  82  via the vacuum transfer chamber  81 , the cap film  43  is formed on the insulation film  42  by supplying an Ar gas and a nitrogen to the space  11 A right underneath the cover plate  17  from the plasma gas supplying part  14 C and by supplying a Si-containing gas such as trimethyl silane or SiH4 to the processing space  11 B from the processing gas supplying part  24  in the plasma processing apparatus  100  provided in the processing chamber  83 , and further by exciting microwave plasma by feeding a microwave to the space  11 A from the radial line slot antenna  30  via the cover plate  17 . 
     After formation of the cap layer  43 , the substrate  41  under processing is transferred to the deposition chamber  84  from the deposition chamber  83  via the vacuum transfer chamber  81 , and in the plasma processing apparatus  100  in the deposition chamber  84 , an Ar gas and a nitrogen gas are supplied from the plasma gas supplying part  14 C to the space  11 A right underneath the cover plate  17 , and the F-doped carbon film  44  is formed on the cap layer  43  by supplying a fluorocarbon source gas having the F/C ratio in the molecule larger than 1 but less than 2, such as C 5 F 8 , into the processing space  11 B from the processing gas supplying part  24 , and further by exciting microwave plasma in the space  11 A by supplying a microwave in the space  11 A from the radial line slot antenna  30  via the cover plate  17 . As explained previously, it is not necessary to add a hydrogen gas to the source gas in the formation step of the F-doped carbon film, and thus, the obtained F-doped carbon film  44  is substantially free from hydrogen. 
     After such formation of the F-doped carbon film, the substrate  41  under processing is transported to the deposition chamber  85  from the deposition chamber  84  via the vacuum transfer chamber  81 , and the hard mask film  45  is formed on the F-doped carbon film in the plasma processing apparatus  100  in the deposition chamber  85  by supplying an Ar gas and a nitrogen gas to the space  11 A right underneath the cover plate  17  from the plasma gas supplying part  14 C and by supplying a Si-containing source gas such as trimethyl silane or SiH 4  to the processing space  11 B from the processing gas supplying part  24 , and further exciting microwave plasma in the space  11 A by supplying a microwave to the space  11 A from the radial line slot antenna via the cover plate  17 . 
     The substrate  41  thus formed with the hard mask film  45  is returned to the load-lock chamber via the vacuum transfer chamber  81  and is forwarded to the resist process and photolithographic process of  FIG. 5C . 
     Thus, by using the cluster-type substrate processing system  80  of  FIG. 7 , it becomes possible to form the hard mask film  45  on the F-doped carbon film  44  without exposing the F-doped carbon film  44  to the air, and it becomes possible to avoid water adsorption to the surface of the film  44 . 
     Third Embodiment 
       FIG. 8  is a diagram showing the construction of a semiconductor device  120  according to a third embodiment of the present invention, wherein those parts of  FIG. 8  explained previously are designated by the same reference numerals and the description thereof will be omitted. 
     Referring to  FIG. 8 , the illustrate shows the state after the Ta barrier metal film  47  is formed but before the Cu layer  48  of  FIG. 5G  is formed explained previously with reference to  FIG. 5F , wherein it should be noted that, with the present embodiment, an Al film  49  is deposited between the surface of the hard mask film  45  or the F-doped carbon film exposed at the opening  44 A and the Ta barrier metal film  47 . 
     By providing the Al film  49 , the Ta barrier film  47  is separated from the F-doped carbon film  44  and the problem of formation of volatile TaF as a result of reaction of the barrier film  47  with F is avoided. Because Al forms stable AlF when reacted with F, it can be seen that there is formed an AlF layer  50  in the construction of  FIG. 8  in the part of the Al film  49  that forms an interface contacting with the F-doped carbon film surface. Further, there is formed an Al—Cu alloy in the part of the Al film  49  that corresponds to the bottom of the opening  44 A where contact to the Cu interconnection pattern  42 A is to be made. 
     The Al film  49  is typically formed by a sputtering process, while it is also possible to form by an ALD process or CVD process. 
     For the film  49 , any metal film that forms a stable compound when reacted with F can be used. For example, it is possible to use Ru, Ni, Co, Pt, Au, Ag, or the like, in addition to Al. 
     With the present embodiment, too, it is preferable to form the F-doped carbon film  33  by using the fluorocarbon source in which the F/C ratio is larger than 1 but smaller than 2 for avoiding the formation of corrosive HF and by using the microwave plasma processing apparatus  100  explained with reference to  FIGS. 2A and 2B . 
     Thereby, it is also possible to use C 3 F 4 , C 4 F 6 , or the like, in addition to C 5 F 8 , for the fluorocarbon source. 
     Further, modification of the fluorine-doped carbon film of the present invention is not limited to nitrogen or Ar explained before, but it is also possible to conduct by using in the radicals containing any of Kr, C, B and Si. 
     While the present invention has been explained heretofore with reference to preferred embodiments, the present invention is by no means limited to such specific embodiments, and various variations and modifications can be made within the scope of the invention in patent claims. 
     INDUSTRIAL APPLICABILITY 
     The present invention is generally applicable to the method of forming an insulation film and is applicable particularly to the film forming method of a F (fluorine)-doped carbon film, the fabrication method of a semiconductor device that uses such a forming method of fluorine-doped carbon film, a semiconductor device fabricated with such a method, and further to a substrate processing system for fabrication of such a semiconductor device.