METHOD OF FABRICATING A WIRE BOND PAD WITH Ni/Au METALLIZATION

Abstract

A method for sealing an exposed surface of a wire bond pad with a material that is capable of preventing a possible chemical attack during electroless deposition of Ni/Au pad metallurgy is provided. Specifically, the present invention provides a method whereby a TiN/Ti or TiN/Al cap is used as a protective coating covering exposed surfaces of a wire bond pad. The TiN/Ti or TiN/Al cap is not affected by alkaline chemistries used in forming the Ni/Au metallization, yet it provides a sufficient electrical pathway connecting the bond pads to the Ni/Au pad metallization.

1 . A semiconductor structure comprising: 
 an interconnect structure containing an upper interconnect level having one or more metal lines, each metal line having a wire bond pad located on a surface thereof;    a metallic cap that is resistant to alkaline attack on a surface of the wire bond pad; and    Ni/Au pad metallurgy atop said metallic cap, said Ni/Au pad metallurgy is in electrical contact with said wire bond pad through said metallic cap.    
     
     
         2 . The structure of  claim 1  wherein the wire bond pad is comprised of Al or an Al stack.  
     
     
         3 . The structure of  claim 1  wherein each metal line is comprised of Cu.  
     
     
         4 . The structure of  claim 1  wherein each metal bond pad is in contact with a corresponding metal line through a via opening located in a lower passivation layer that is located on said interconnect structure.  
     
     
         5 . The structure of  claim 1  further comprising passivation layers encapsulating said wire bond pad and Ni/Au pad metallurgy.  
     
     
         6 . The structure of  claim 5  wherein said passivation layers includes a lower passivation layer and overlying final passivation layers, said overlying final passivation layers comprising an oxide layer, a nitride layer and a layer of polyimide or a layer of polysiloxane.  
     
     
         7 . The structure of  claim 1  wherein the metallic cap comprises TiN/Ti, said Ti is activated Ti.  
     
     
         8 . The structure of  claim 1  wherein the metallic cap comprises TiN/Al, said Al is cleaned/pretreated Al.