Method for manufacturing fine-pitch bumps and structure thereof

Abstract

A method for manufacturing fine-pitch bumps comprises the steps of providing a silicon substrate; forming a titanium-containing metal layer on the silicon substrate, wherein the titanium-containing metal layer comprises a plurality of first zones and a plurality of second zones; forming a photoresist layer on the titanium-containing metal layer; patterning the photoresist layer to form a plurality of opening slots; forming a plurality of copper bumps at the opening slots, wherein each of the copper bumps comprises a first top surface and a ring surface; heating the photoresist layer to form a plurality of body portions and a plurality of removable portions; etching the photoresist layer; and removing the second zones to enable each of the first zones to form an under bump metallurgy layer having a bearing portion and an extending portion.

What is claimed is: 
     
         1 . A fine-pitch bump structure at least comprising:
 a silicon substrate having a surface, a plurality of bond pads disposed at the surface and a protective layer disposed at the surface, wherein the protective layer comprised a plurality of openings, and the bond pads are revealed by the openings;   a plurality of under bump metallurgy layers formed on the bond pads, each of the under bump metallurgy layers comprises a bearing portion and an extending portion;   a plurality of copper bumps formed on the under bump metallurgy layers, each of the copper bumps comprises a first top surface and a ring surface, the bearing portion of each of the under bump metallurgy layers is located under each of the copper bumps, and the extending portion of each of the under bump metallurgy layers is protruded to the ring surface of each of the copper bumps;   a plurality of bump protection layers formed on the extending portions of the under bump metallurgy layers, the first top surface and the ring surface of each of the copper bumps, each of the bump protection layers comprises a metallic coverage portion and a bump coverage portion having a second top surface, wherein the first top surface and the ring surface of each of the copper bumps are covered with each of the bump coverage portions, and each of the extending portions is covered with each of the metallic coverage portions; and   a plurality of wettable layers formed on the second top surfaces of the bump coverage portions.   
     
     
         2 . The fine-pitch bump structure in accordance with  claim 1 , wherein each of the bump coverage portions comprises a first outer lateral surface, each of the metallic coverage portions comprises a second outer lateral surface and is protruded to the first outer lateral surface of the bump coverage portion. 
     
     
         3 . The fine-pitch bump structure in accordance with  claim 2 , wherein the extending portion of each of the under bump metallurgy layers comprises a third outer lateral surface coplanar with the second outer lateral surface. 
     
     
         4 . The fine-pitch bump structure in accordance with  claim 1 , wherein the material of the bump protection layers can be chosen from one of nickel, palladium or gold. 
     
     
         5 . The fine-pitch bump structure in accordance with  claim 1 , wherein the under bump metallurgy layers are made of a material selected from one of titanium/tungsten/gold, titanium/copper and titanium/tungsten/copper.