Plasma sputtering a metal or metal nitride with a magnetron having unequal poles

Abstract

A magnetron especially advantageous for low-pressure plasma sputtering or sustained self-sputtering having reduced area but full target coverage. The magnetron includes an outer pole of one magnetic surrounding an inner pole of the other polarity with a gap therebetween. The magnetron is small, primarily located on one side of the central axis, about which it is rotated. The total magnetic flux of the outer pole is at least 1.5 times that of the inner pole. Different shapes include a racetrack, an ellipse, an egg shape, a triangle, and a triangle with an arc conforming to the target periphery. The invention allows increased ionization of the sputtered atoms.

1 . A method of sputtering material from a target comprising a metal onto a working substrate supported on a pedestal in a system including a magnetron disposed on a side of said target opposite said pedestal along a central axis of a vacuum chamber containing said pedestal and including an outer pole having a first magnetic polarity and a first total magnetic flux and an inner pole surrounded by said outer pole and having a second magnetic polarity opposite said first magnetic polarity and a second total magnetic flux which is larger than said first total magnetic flux by a factor of at least 1.5, said method comprising the steps of: 
 rotating said magnetron about said central axis;    admitting a working gas into said vacuum chamber; and    applying DC power to said target to excite said working gas into a plasma to thereby sputter said metal of said target onto said substrate.    
     
     
         2 . The method of  claim 1 , wherein said metal is tantalum.  
     
     
         3 . The method of  claim 1 , wherein said metal is titanium.  
     
     
         4 . The method of  claim 1 , wherein said metal is tungsten.  
     
     
         5 . The method of  claim 1 , further comprising admitting gaseous nitrogen into said vacuum chamber, wherein a nitride of said metal is formed on said substrate.  
     
     
         6 . The method of  claim 5 , wherein said metal is tantalum.  
     
     
         7 . The method of  claim 5 , wherein said metal is titanium.  
     
     
         8 . The method of  claim 5 , wherein said metal is tungsten.  
     
     
         9 . The method of  claim 1 , wherein said factor is at least 2.0.  
     
     
         10 . The method of  claim 1 , wherein an area within a periphery of said magnetron is no more than ⅙ of a usable area of said target.  
     
     
         11 . The method of  claim 1 , further comprising RF biasing said pedestal.  
     
     
         12 . A tantalum sputtering method performed in a plasma sputter reactor having a tantalum target disposed on one side of a vacuum chamber and arranged about a central axis, comprising the steps of: 
 supporting a substrate to be sputter coated on a pedestal electrode arranged opposite said target along said central axis;    rotating a magnetron disposed on a side of said target opposite said pedestal about said central axis, said magnetron including an inner pole of a first magnetic polarity and having a first total magnetic flux and an outer pole of a second magnetic polarity opposite said first magnetic polarity, having a second total magnetic flux greater than said first total magnetic flux by a factor of at least 1.5, and surrounding said first magnetic pole;    admitting argon into said vacuum chamber;    applying negative DC power to said target to excite said argon into a plasma to sputter said target; and    RF biasing said pedestal electrode to induce a negative DC self-bias thereupon.    
     
     
         13 . The method of  claim 12 , wherein said factor is at least 2.0.  
     
     
         14 . The method of  claim 12 , wherein an area within a periphery of said magnetron is no more than ⅙ of an area of said target.  
     
     
         15 . The method of  claim 12 , further comprising admitting nitrogen into said vacuum chamber, whereby tantalum nitride is deposited on said substrate.  
     
     
         16 . A tantalum plasma sputter reactor, comprising: 
 a vacuum chamber;    a tantalum target disposed on a side of said vacuum chamber;    a pedestal electrode disposed in said vacuum chamber in opposition to said target for supporting a substrate to be sputter coated; and    a magnetron rotatable about said central axis and including an inner magnetic pole having a first magnetic polarity and a first total magnetic flux and an outer magnetic pole surrounding said inner magnetic pole and having a second magnetic polarity opposite said first magnetic polarity and a second total magnetic flux greater than said first total magnetic flux by a ratio of at least 1.5.    
     
     
         17 . The reactor of  claim 16 , wherein said ratio is at least 2.0.  
     
     
         18 . The reactor of  claim 16 , wherein an area within a periphery of said magnetron is no more than ⅙ of an area of said target.  
     
     
         19 . The reactor of  claim 16 , further comprising an RF power supply connected to said pedestal electrode.