Stress tunable tantalum and tantalum nitride films

Abstract

The present disclosure pertains to our discovery that the residual stress residing in a tantalum (Ta) film or a tantalum nitride (TaN x , where 0<x≦1.5) film can be controlled (tuned) by controlling particular process variables during deposition of the film. Process variables of particular interest during film deposition, for sputter applied Ta and TaN x films, include the following. The power to the sputtering target; the process chamber pressure (i.e. the concentration of various gases and ions present in the chamber); the substrate DC offset bias voltage (typically an increase in the AC applied substrate bias power); and, the temperature of the substrate upon which the film is being deposited. When the Ta or TaN x film is deposited using IMP sputtering, the power to the ionization coil can be used for stress tuning of the film. Of these variables, the process chamber pressure and the substrate offset bias most significantly affect the tensile and compressive stress components, respectively. The most advantageous tuning of a sputtered film is achieved using Ion Metal Plasma (IMP) as the film deposition method. This sputtering method provides for particular control over the ion bombardment of the depositing film surface. Tantalum (Ta) films deposited using the IMP method typically exhibit a residual stress ranging from about +1×10 +10 dynes/cm 2 (tensile stress) to about −2×10 +10 dynes/cm 2 (compressive stress), depending on the process variables described above. Tantalum nitride (TaN x ) films deposited using the IMP method typically can be tuned to exhibit a residual stress within the same range as that specified above with reference to Ta films. We have been able to reduce the residual stress in either the Ta or TaN x films to range between about 6×10 +9 and about −6×10 +9 dynes/cm 2 using tuning techniques described herein. The Ta and TaN x films can also be tuned subsequent to deposition using ion bombardment of the film surface and annealing of the deposited film.

We claim:  
     
         1 . A Ta film tuned to have a residual film stress ranging between about 1.0×10 +10  and about −2×10 +10  dynes/cm 2 .  
     
     
         2 . The Ta film of  claim 1 , wherein said Ta film was sputter deposited.  
     
     
         3 . The Ta film of  claim 2 , wherein said Ta film was IMP sputter deposited.  
     
     
         4 . The Ta film of  claim 1 , wherein said film residual stress ranges between about 6×10 +9  and about −6×10 +9  dynes/cm 2 .  
     
     
         5 . The Ta film of  claim 1 , wherein a crystalline structure of said tantalum film is bcc Ta.  
     
     
         6 . The Ta film of  claim 1 , wherein a crystalline structure of said tantalum film is S Ta.  
     
     
         7 . A TaN x  film, where 0<x≦1.5, tuned to have a residual film stress ranging between about 1.0×10 +10  and about −2×10 +10  dynes/cm 2 .  
     
     
         8 . The TaN x  film of  claim 7 , wherein said TaN x  film was sputter deposited.  
     
     
         9 . The TaN x  film of  claim 8 , wherein said TaN x  film was reactive IMP sputter deposited.  
     
     
         10 . The TaN x  film of  claim 7 , wherein said film residual stress ranges between about 6×10 +9  and about −6×10 +9  dynes/cm 2 .  
     
     
         11 . The TaN x  film of  claim 7 , wherein said film resistivity is less than about 1,000 μΩ-cm and said film stress ranges between about 6×10 +9  and about −6×10 +9  dynes/cm 2 .  
     
     
         12 . The TaN x  film of  claim 11 , wherein said film comprises more than about 30 atomic % nitrogen.  
     
     
         13 . The TaN x  film of  claim 12 , wherein said film comprises and less than about 60% nitrogen.  
     
     
         14 . A method of tuning the residual film stress of a Ta film, wherein said residual stress is tuned by controlling the amount of ion bombardment of the depositing film surface.  
     
     
         15 . The method of  claim 14 , wherein said Ta film is deposited using a sputtering technique.  
     
     
         16 . The method of  claim 15 , wherein said Ta film is deposited using IMP sputtering.  
     
     
         17 . The method of  claim 15 , wherein said tantalum film comprises bcc Ta.  
     
     
         18 . The method of  claim 15 , wherein a crystalline structure of said tantalum film is β Ta.  
     
     
         19 . A method of tuning tile residual film stress of a Ta film by adjustment of a film deposition process variable selected from the group consisting of process chamber pressure, substrate DC offset bias voltage, power to a sputtering target, power to an ionization coil, substrate temperature, or a combination thereof.  
     
     
         20 . The method of  claim 19 , wherein said residual film stress is tuned to range between about 1×10 +10  and about −2×10 +10  dynes/cm 2 .  
     
     
         21 . A method of tuning the residual film stress of a Ta film subsequent to deposition, wherein said treatment is selected from the group consisting of ion bombardment, annealing, and combinations thereof.  
     
     
         22 . The method of  claim 21 , wherein said residual film stress is tuned to range between about 1×10 +10  and about −2×10 +10  dynes/cm 2 .  
     
     
         23 . The method of  claim 21 , wherein said method of tuning is ion bombardment.  
     
     
         24 . The method of  claim 21 , wherein said method of tuning is annealing, and wherein said annealing is carried out at a temperature of at least about 25° C.  
     
     
         25 . The method of  claim 24 , wherein said temperature is at least about 250° C.  
     
     
         26 . The method of  claim 25 , wherein said temperature is at least about 350° C.  
     
     
         27 . A method of tuning the residual film stress of a TaN x , film, wherein said residual stress is tuned by controlling the amount of ion bombardment of the depositing film surface and where 0<x≦1.5.  
     
     
         28 . The method of  claim 27 , wherein said TaN x  film is deposited using a sputtering technique.  
     
     
         29 . The method of  claim 28 , wherein said TaN film is deposited using reactive IMP sputtering.  
     
     
         30 . The method of  claim 29 , wherein said TaN x  film comprises at least about 30 atomic % nitrogen.  
     
     
         31 . The method of  claim 30 , wherein said nitrogen content is less than about 60 atomic % nitrogen.  
     
     
         32  A method of tuning the residual film stress of a TaN x  film by adjustment of a film deposition process variable selected from the group consisting of process chamber pressure, substrate DC offset bias voltage, power to a sputtering target, power to an ionization coil, substrate temperature, or a combination thereof.  
     
     
         33 . The method of  claim 32 , wherein said residual film stress is tuned to range between about 1×10 +10  and about −2×10 +10  dynes/cm 2 .  
     
     
         34 . A method of tuning the residual film stress of a TaN x  film subsequent to deposition, wherein said treatment is selected from the group consisting of ion bombardment, annealing, and combinations thereof.  
     
     
         35 . The method of  claim 34 , wherein said residual film stress is tuned to range between about 1×10 +10  and about −2×10 +10  dynes/cm 2 .  
     
     
         36 . The method of  claim 34 , wherein said method of tuning is ion bombardment.  
     
     
         37 . The method of  claim 34 , wherein said method of tuning is annealing, and wherein said annealing is carried out at a temperature of at least about 25° C.  
     
     
         38 . The method of  claim 37 , wherein said temperature is at least about 250° C.  
     
     
         39 . The method of  claim 38 , wherein said temperature is at least about 350° C.