Method of producing smooth titanium nitride films having low resistivity

Abstract

The resistivity of titanium nitride films is reduced, by about 40% (to less than about 60 μOhm-cm), for example; and, the film surface roughness is reduced, by about 45% (to less than 6 Å) by using a combination of particular process conditions during deposition of the film. In particular, titanium atoms produced by impact of inert gas ions upon a titanium target travel through a high density, inductively coupled rf plasma, an ion metal plasma (IMP), in which the titanium atoms are at least partially ionized. The ionized titanium ions are contacted with ionized nitrogen atoms also present in the processing chamber. The resultant gas phase composition is contacted with the surface of a semiconductor substrate on which a titanium nitride barrier layer is to be deposited. By controlling the gas phase deposition mixture composition, the quantity of the deposition mixture contacting the substrate surface over a given time period, and the pressure in the process vessel, the resistivity and surface roughness of the titanium nitride layer is adjusted. The resistivity of the titanium nitride barrier layer is principally determined by the crystal orientation of the titanium nitride. The more nearly the crystal orientation approaches 100% of the {200} orientation (the lower the percentage of {111} orientation), the lower the film resistivity. Crystal orientation is obtained by increasing the ionized content of the deposition mixture and by slowing the rate of deposition of the titanium nitride film (barrier layer). The surface roughness of the titanium nitride layer is reduced principally by reducing the pressure in the process vessel, which affects the film formation dynamics. An increase in ionized content of the deposition mixture helps reduce surface roughness until an inflection point is reached, after which surface roughness increases with increased ionized content.

We claim:  
     
         1 . A titanium nitride film having a resistivity of less than about 75 μΩ-cm.  
     
     
         2 . The titanium nitride film of  claim 1 , having a resistivity of less than about 60 μΩ-cm.  
     
     
         3 . The titanium nitride film of  claim 1  having a surface roughness of less than about 11 Å.  
     
     
         4 . The titanium nitride film of  claim 2  having a surface roughness of less than about 8 Å.  
     
     
         5 . A titanium nitride film having a surface roughness of less than about 11 Å.  
     
     
         6 . The titanium nitride film of  claim 5 , having a surface roughness of less than about 8 Å.  
     
     
         7 . A method of producing a titanium nitride film having a resistivity of less than about 75 μΩ-cm, said method comprising the steps of: 
 a) controlling the gas phase deposition mixture composition from which said film is produced; and  
 b) controlling the deposition rate of said film on a substrate.  
 
     
     
         8 . 0  The method of  claim 7 , wherein said deposition is made using a reactive ion deposition process and wherein said gas phase mixture composition is controlled by controlling process variables including DC power applied to a sputtering target and RF power applied to an ionization source.  
     
     
         9 . The method of  claim 8 , wherein said ionization source is an ionization coil.  
     
     
         10 . The method of  claim 7 , wherein said deposition is made using a reactive ion deposition process and wherein said deposition rate of said film on said substrate is controlled by controlling a pressure in a process vessel in which said reactive ion deposition process is carried out.  
     
     
         11 . A method of producing a titanium nitride film having a resistivity of less than about 75 μΩ-cm, said method comprising controlling the crystal orientation of said titanium nitride film to have at least 70% of a {200} crystal orientation.  
     
     
         12 . The method of  claim 11 , wherein said titanium nitride film is produced using a reactive ion deposition process and wherein said crystal orientation is obtained by increasing the ionized content of a gas phase deposition mixture.  
     
     
         13 . The method of  claim 12 , wherein said crystal orientation is further obtained by slowing the rate of deposition of said titanium nitride film upon a substrate.  
     
     
         14 . A method of producing a titanium nitride film having a surface roughness of less than about 11 Å, wherein said method comprises a reactive ion deposition process which includes the steps of: 
 a) controlling the rate of deposition of a titanium nitride film upon a substrate; and  
 b) controlling an ionization content in a deposition mixture from which said film is deposited.  
 
     
     
         15 . The method of  claim 14 , wherein said deposition rate of a titanium nitride film is controlled by controlling the pressure in a process vessel in which said reactive ion deposition process is carried out.  
     
     
         16 . The method of  claim 15 , wherein said ionization content is the ionization content in a gas phase deposition mixture is controlled by controlling RF power to an ionization source.  
     
     
         17 . A method of producing a titanium nitride film having a resistivity of less than about 75 μΩ-cm and a surface roughness of less than about 11 Å, said method including a reactive ion deposition process and comprising the steps of controlling the rate of deposition of said titanium nitride film upon a substrate and by controlling the ionized content of a deposition mixture from which said titanium nitride film is deposited.  
     
     
         18 . The method of  claim 17 , wherein said rate of deposition is controlled by controlling a pressure in a process vessel in which said reactive ion deposition process is carried out.  
     
     
         19 . The method of  claim 18 , wherein said ionized content of said deposition mixture is controlled by controlling RF power applied to an ionization source.  
     
     
         20 . The method of  claim 19 , wherein said ionization source is an ionization coil.