| abstract |
A process for making a copper post with footing profile employs dual photoresist films of different photosensitivities and thicknesses on an under-bump-metallurgy (UBM) layer. After an exposure lithography process, a first opening with a substantially vertical sidewall is formed in a first photoresist film, and a second opening with a sloped sidewall is formed in a second photoresist film. The second opening has a top diameter and a bottom diameter greater than the top diameter, and the bottom diameter is greater than the diameter of the first opening. A conductive layer is then formed in the first opening and the second opening followed by removing the dual photoresist films. |