Patent ID: 8598030

Claim:
A method of forming an integrated circuit device, comprising: forming an under-bump-metallurgy (UBM) layer overlying a semiconductor substrate; forming a photoresist structure on the UBM layer, wherein the photoresist structure comprises a first photoresist film and a second photoresist film on the first photoresist film, and the first photoresist film and the second photoresist film have different photosensitivities; forming an opening in the photoresist structure to expose a portion of the UBM layer, wherein the opening comprises: a first opening in the first photoresist film, the first opening defined by sidewalls of the first photoresist film, and a second opening in the second photoresist film, wherein the first opening having a top diameter, and a bottom diameter greater than the top diameter; forming a conductive layer in the opening of the photoresist structure, electrically connected to the exposed portion of the UBM layer; and removing the photoresist structure, wherein the conductive layer forms a conductive post.