Bump and fabricating process thereof

Abstract

A bump structure on a contact pad and a fabricating process thereof. The bump comprises an under-ball-metallurgy layer, a bonding mass and a welding lump. The under-ball-metallurgy layer is formed over the contact pad and the bonding mass is formed over the under-ball-metallurgy layer by conducting a pressure bonding process. The bonding mass having a thickness between 4 to 10 μm is made from a material such as copper. The welding lump is formed over the bonding mass such that a sidewall of the bonding mass is also enclosed.

1 . A bump structure on a contact pad, comprising: 
 an under-ball-metallurgy layer over the contact pad;    a bonding mass over the under-ball-metallurgy layer, wherein the bonding mass is formed over the under-ball-metallurgy layer by pressure-bonding; and    a bump over the bonding mass.    
   
   
       2 . The bump structure of  claim 1 , wherein the under-ball-metallurgy layer comprises: 
 an adhesion layer over the contact pad; and    a barrier layer over the adhesion layer, wherein the bonding mass is formed over the barrier layer.    
   
   
       3 . The bump structure of  claim 2 , wherein material constituting the adhesion layer is selected from the group consisting of titanium, titanium-tungsten alloy, aluminum and chromium.  
   
   
       4 . The bump structure of  claim 2 , wherein material constituting the barrier layer is selected from the group consisting of nickel-vanadium alloy and nickel.  
   
   
       5 . The bump structure of  claim 1 , wherein the bonding mass is made from a material including copper.  
   
   
       6 . The bump structure of  claim 1 , wherein the bonding mass has a thickness between about 4 μm to 10 μm.  
   
   
       7 . The bump structure of  claim 1 , wherein material constituting the bump includes a lead-tin alloy.  
   
   
       8 . The bump structure of  claim 1 , wherein material constituting the bump includes a lead-free alloy.  
   
   
       9 . The bump structure of  claim 7 , wherein material constituting the bump is selected from the group consisting of tin, gold, silver, copper, bismuth, antimony, indium, zinc or combinations thereof in the form of an alloy.