本发明提供一种凸块结构与其形成方法。凸块结构包括：一接触组件形成于一基板之上；一保护层位于该基板上，其中该保护层具有一保护层开口暴露该接触组件；一聚亚酰胺(polyimide)层位于该保护层之上，其中该聚亚酰胺层具有一聚亚酰胺层开口暴露该接触组件；一凸块下方金属化(UBM)特征结构电性耦合到该接触组件，其中该凸块下方金属化(UBM)特征结构具有一凸块下方金属化特征结构宽度；以及一铜柱位于该凸块下方金属化(UBM)特征结构之上，其中该铜柱的一末端具有一柱状结构宽度，该凸块下方金属化特征结构宽度大于该柱状结构宽度。

The invention provides a bump structure and method of manufacturing same. The bump structure comprises a contact element formed over a substrate; a passivation layer overlying the substrate, the passivation layer having a passivation opening exposing the contact element; a polyimide layer overlying the passivation layer, the polyimide layer having a polyimide opening exposing the contact element; an under bump metallurgy (UBM) feature electrically coupled to the contact element, the under bump metallurgy feature having a UBM width; and a copper pillar on the under bump metallurgy feature, a distal end of the copper pillar having a pillar width, the UBM width greater than the pillar width.