Forming wafer-level chip scale package structures with reduced number of seed layers

摘要

A method includes forming a passivation layer over a metal pad, which is overlying a semiconductor substrate. A first opening is formed in the passivation layer, with a portion of the metal pad exposed through the first opening. A seed layer is formed over the passivation layer and to electrically coupled to the metal pad. The seed layer further includes a portion over the passivation layer. A first mask is formed over the seed layer, wherein the first mask has a second opening directly over at least a portion of the metal pad. A PPI is formed over the seed layer and in the second opening. A second mask is formed over the first mask, with a third opening formed in the second mask. A portion of a metal bump is formed in the third opening. After the step of forming the portion of the metal bump, the first and the second masks are removed.