CU PILLAR BUMP WITH ELECTROLYTIC METAL SIDEWALL PROTECTION

摘要

A method of forming a bump structure includes providing a semiconductor substrate and forming an under-bump-metallurgy (UBM) layer on the semiconductor substrate. The method further includes forming a mask layer on the UBM layer, wherein the mask layer has an opening exposing a portion of the UBM layer. The method further includes forming a copper layer in the opening of the mask layer and removing a portion of the mask layer to form a space between the copper layer and the mask layer. The method further includes performing an electrolytic process to fill the space with a metal layer and removing the mask layer.