Patent ID: 8610267

Claim:
A device comprising: a die comprising: a metal pad; a passivation layer covering edge portions of the metal pad; a patterned buffer layer over the passivation layer, wherein the patterned buffer layer comprises a plurality of discrete portions separated from each other, and wherein one of the plurality of discrete portions of the patterned buffer layer comprises: a first top surface; a second top surface lower than the first top surface; a bottom surface contacting a top surface of the passivation layer; a first sidewall connecting the first top surface to the second top surface; and a second sidewall connecting the second top surface to the top surface of the passivation layer; an under-bump-metallurgy (UBM) in an opening in the patterned buffer layer and an opening in the passivation layer; and a metal bump over and electrically coupled to the UBM.