Wire bonding process for copper-metallized integrated circuits

Abstract

A robust, reliable and low-cost metal structure and process enabling electrical wire/ribbon connections to the interconnecting copper metallization of integrated circuits. The structure comprises a layer of barrier metal that resists copper diffusion, deposited on the non-oxidized copper surface in a thickness such that the barrier layer reduces the diffusion of copper at 250° C. by more than 80% compared with the absence of the barrier metal. The structure further comprises an outermost bondable layer which reduces the diffusion of the barrier metal at 250° C. by more than 80% compared with the absence of the bondable metal. Finally, a metal wire is bonded to the outermost layer for metallurgical connection. The barrier metal is selected from a group consisting of nickel, cobalt, chromium, molybdenum, titanium, tungsten, and alloys thereof. The outermost bondable metal layer is selected from a group consisting of gold, platinum, and silver.

1 . A structure for metallurgical connections between metal wires and bond pads positioned on integrated circuits having copper interconnecting metallization, comprising: 
 a bond pad surface of non-oxidized copper;    a layer of barrier metal that resists copper diffusion deposited on said copper surface, said barrier metal and the thickness thereof coordinated such that said layer reduces the diffusion of copper at 250° C. by more than 80% compared with the absence of such barrier metal;    an outermost layer of bondable metal, coordinated with thickness thereof such that said outermost layer reduces the diffusion of said barrier metal at 250° C. by more than 80% compared with the absence of said bondable metal; and    one of said metal wires bonded to said outermost bondable metal.    
     
     
         2 . The structure according to  claim 1  wherein said barrier metal layer is selected from a group consisting of nickel, cobalt, chromium, molybdenum, titanium, tungsten, and alloys thereof.  
     
     
         3 . The structure according to  claim 1  wherein said bondable metal layer is selected from a group consisting of gold, platinum, palladium, and silver.  
     
     
         4 . The structure according to  claim 1  further comprising a thin seed metal layer between said non-oxidized copper and said barrier metal layer.  
     
     
         5 . The structure of  claim 4  wherein said seed metal is palladium or tin.  
     
     
         6 . The structure according to  claim 1  wherein said metal wires are selected from a group consisting of gold, copper, aluminum, and alloys thereof.  
     
     
         7 - 15 . (canceled)