Interconnections for flip-chip using lead-free solders and having reaction barrier layers

Abstract

An interconnection structure suitable for flip-chip attachment of microelectronic device chips to packages, comprising a two, three or four layer ball-limiting composition including an adhesion/reaction barrier layer, and having a solder wettable layer reactive with components of a tin-containing lead free solder, so that the solderable layer can be totally consumed during soldering, but a barrier layer remains after being placed in contact with the lead free solder during soldering. One or more lead-free solder balls is selectively situated on the solder wetting layer, the lead-free solder balls comprising tin as a predominant component and one or more alloying components. With a two-layer ball-limiting composition comprising an adhesion/reaction barrier layer, wherein the adhesion/reaction barrier layer serves both as an adhesion layer and a reaction barrier layer, the adhesion/reaction barrier layer can be comprised of a material selected from the group consisting of Zr and ZrN

1 . In an interconnection structure suitable for flip-chip attachment of microelectronic device chips to chip carriers, a three-layer ball limiting metallurgy comprising:
 an adhesion layer for deposition on a wafer or substrate;   a solder reaction barrier layer of a material selected from the group consisting of Ti, TiN, Ta, TaN, Zr, ZrN, V and Ni; and   a solder wettable layer.   
     
     
         2 . The interconnection structure of  claim 1 , wherein the adhesion layer is formed of a material selected from the group consisting of Cr, TiW, TiN, TaN, Ti, Ta, Zr, and ZrN. 
     
     
         3 . The interconnection structure of  claim 1 , wherein the solder wettable layer is formed of a material selected from the group consisting of Cu, Pd, Co, Ni, Au, Pt, and Sn. 
     
     
         4 . The interconnection structure of  claim 1 , further comprising an optional fourth layer formed of a material selected from the group consisting of Au and Sn, if Au or Sn is not used in the third layer. 
     
     
         5 . The interconnection structure of  claim 1 , wherein said adhesion layer is comprised of one of Cr and TiW, said reaction barrier is comprised of Ti, and said solder wettable layer is comprised of one of Cu, Co, Ni, Pd and Pt. 
     
     
         6 . An interconnection structure suitable for flip-chip attachment of microelectronic device chips to packages, comprising:
 a three-layer ball-limiting composition comprising an adhesion layer, a reaction barrier layer on top of said adhesion layer and a solder wettable layer, wherein said adhesion/barrier layer is between a microelectronic device and said solder wettable layer and wherein said solder wettable layer is of a composition sufficiently reactive with components of a tin-containing lead free solder, and the reaction barrier layer is substantially less-reactive with solder after being placed in contact therewith in a solder joining process; and   one or more lead-free solder balls selectively situated on said solder wettable layer, said lead-free solder balls having tin as a predominant component and one or more alloying components selected from the group consisting of Cu, Zn, Ag, Bi and Sb, whereby said lead-free solder ball substantially avoids alpha particle emission and induced soft logic errors which result therefrom.   
     
     
         7 . The interconnection structure defined in  claim 6 , wherein said solderable layer is formed of a material selected from the group consisting of Cu, Ni, Co, Pd, PdNi, PdCo, NiCo, Au, Pt and Sn. 
     
     
         8 . A three layer ball limiting structure comprising a Cr adhesion layer for placement on a substrate; a Cu seed layer and a Ni reaction barrier layer on the Cu layer. 
     
     
         9 . The structure defined in  claim 8 , further comprising a lead free solder composition in which the Ni layer is reacted with solder during reflow of the solder.