US Patent 7863742 Back end integrated WLCSP structure without aluminum pads

An integrated circuit structure includes a passivation layer; a via opening in the passivation layer; a copper-containing via in the via opening; a polymer layer over the passivation layer, wherein the polymer layer comprises an aperture, and wherein the copper-containing via is exposed through the aperture; a post-passivation interconnect (PPI) line over the polymer layer, wherein the PPI line extends into the aperture and physically contacts the copper-via opening; and an under-bump metallurgy (UBM) over and electrically connected to the PPI line.