Ladder Bump Structures and Methods of Making Same

摘要

An embodiment ladder bump structure includes an under bump metallurgy (UBM) feature supported by a substrate, a copper pillar mounted on the UBM feature, the copper pillar having a tapering curved profile, which has a larger bottom critical dimension (CD) than a top critical dimension (CD) in an embodiment, a metal cap mounted on the copper pillar, and a solder feature mounted on the metal cap.