Methods of producing ultra -low resistivity tantalum films.

Abstract

We have discovered that, by depositing a tantalum layer upon a substrate at a temperature of at least 325° C., it is possible to obtain an ultra low resistivity which is lower than that previously published in the literature. In addition, it is possible deposit a Ta x N y film having an ultra low resistivity by depositing the Ta x N y film upon a substrate at a temperature of at least 275° C., wherein x is 1 and y ranges from about 0.05 to about 0.18. These films having an ultra low resistivity are obtained at temperatures far below the previously published temperatures for obtaining higher resistivity films. A combination of elevated substrate temperature and ion bombardment of the film surface during deposition enables the use of lower substrate temperatures while maintaining optimum film properties. In another development, we have discovered that the ultra low resistivity tantalum and Ta x N y films produced by the method of the present invention also exhibit particularly low residual stress, so that they are more stable and less likely to delaminate from adjacent layers in a multilayered semiconductor structure. Further, these films can be chemical mechanical polished at significantly higher rates (at least 40% higher rates) than the higher resistivity tantalum and Ta x N y films previously known in the industry. This is particularly useful in damascene processes when copper is used as the interconnect metal, since it reduces the possibility of copper dishing during a polishing step.

We claim:  
     
         1 . A tantalum film having a resistivity of less than 25 μΩ-cm.  
     
     
         2 . A tantalum film according to  claim 1 , wherein said film has a residual stress ranging between about 5.0×10 9  and −5.0×10 9  dynes/cm 2 .  
     
     
         3 . A tantalum film according to  claim 1 , having a chemical-mechanical polishing rate which is at least 40% increased over the polishing rate of a tantalum film having a resistivity of at least 100 μΩ-cm.  
     
     
         4 . A method of producing the tantalum film according to  claim 1 , or  claim 2 , or  claim 3 , wherein said film is produced by sputter deposition upon a substrate at a temperature of about 325° C. or greater.  
     
     
         5 . The method according to  claim 4 , wherein said sputter deposition is high density plasma sputter deposition, and the surface of said tantalum film is ion bombarded during deposition, whereby said substrate temperature is reduced by as much as about 40% during said deposition without an increase in the resistivity of said deposited tantalum film.  
     
     
         6 . The method according to  claim 4 , wherein said tantalum film is produced by sputter deposition upon a substrate at a temperature within the range of about 350° C. to about 550° C.  
     
     
         7 . The method according to  claim 6 , wherein said sputter deposition is high density plasma sputter deposition, and the surface of said tantalum film is ion bombarded during deposition, whereby said substrate temperature is reduced by as much as about 40% during said deposition without an increase in the resistivity of said deposited tantalum film.  
     
     
         8 . A method of producing the tantalum film according to  claim 1 , wherein said film is produced by sputter deposition upon a substrate at a temperature of less than about 325° C. and wherein said film is subsequently annealed at a temperature greater than about 325° C.  
     
     
         9 . A Ta x N y  film having a resistivity of less than 25 μΩ-cm, wherein x is 1 and y ranges from about 0.05 to about 0.18.  
     
     
         10 . A Ta x N y  film according to  claim 9 , wherein said film has a residual stress ranging between about 5.0×10 9  and −5.0×10 9  dynes/cm 2 .  
     
     
         11 . A Ta x N y  film according to  claim 9 , having a chemical-mechanical polishing rate which is at least 40% increased over the polishing rate of a Ta x N y  film having a resistivity of at least 100 μΩ-cm.  
     
     
         12 . A method of producing the Ta x N y  film of  claim 9 , wherein said film is produced by sputter deposition upon a substrate at a temperature of about 275° C. or greater.  
     
     
         13 . A method of producing the Ta x N y  film according to  claim 9 , wherein said film is produced by sputter deposition upon a substrate at a temperature of less than about 275° C. and wherein said film is subsequently annealed at a temperature of about 275° C. or greater.  
     
     
         14 . A tantalum film according to  claim 1 , wherein said film has a chemical-mechanical polishing rate of at least 270 Å per minute.  
     
     
         15 . A Ta x N y  film according to  claim 9 , wherein said film has a chemical-mechanical polishing rate of at least 270 Å per minute.  
     
     
         16 . A method of producing a sputtered tantalum film having a resistivity of less than 25 μΩ-cm, said method comprising: 
 placing a substrate on a temperature-controlled support platen in a physical vapor deposition process chamber; and  
 controlling the temperature of said support platen during the sputtering of said tantalum film upon said substrate, in a manner such that said substrate temperature is about 325° C. or higher during deposition of said sputtered tantalum film.  
 
     
     
         17 . The method according to  claim 16 , wherein said support platen temperature is controlled to be at an individual temperature between about 350° C. and about 550° C. or is controlled over a temperature ranging between about 350° C. and about 550° C.  
     
     
         18 . A method of producing a sputtered Ta x N y  film, said method comprising: 
 placing a substrate on a temperature-controlled support platen in a physical vapor deposition process chamber; and    controlling the temperature of said support platen during the sputtering of said Ta x N y  film upon said substrate, in a manner such that said substrate temperature is about 275° C. or greater during deposition of said sputtered Ta x N y  film.    
     
     
         19 . The method according to  claim 18 , wherein said support platen temperature is controlled to be at an individual temperature between about 275° C. and about 550° C. or is controlled over a temperature ranging between about 275° C. and about 550° C.  
     
     
         20 . The method according to  claim 16 , wherein said sputter deposition is high density plasma sputter deposition, and the surface of said tantalum film is ion bombarded during deposition, whereby said substrate temperature is reduced by as much as about 40% during said deposition without an increase in the resistivity of said deposited tantalum film.  
     
     
         21 . The method according to  claim 18 , wherein said sputter deposition is high density plasma sputter deposition, and the surface of said Ta x N y  film is ion bombarded during deposition, whereby said substrate temperature is reduced by as much as about 40% during said deposition without an increase in the resistivity of said deposited Ta x N y  film.