UBM etching methods for eliminating undercut

摘要

A method includes forming an under-bump metallurgy (UBM) layer overlying a substrate, and forming a mask overlying the UBM layer. The mask covers a first portion of the UBM layer, and a second portion of the UBM layer is exposed through an opening in the mask. A metal bump is formed in the opening and on the second portion of the UBM layer. The mask is then removed. A laser removal is performed to remove a part of the first portion of the UBM layer and to form an UBM.