An under bump metallurgy (UBM) structure is described. Two UBM mask processes are utilized. First, a top layer of copper (Cu) and/or a middle layer of nickel-vanadium (NiV) or chrome-copper (CrCu) is personalized by standard photoprocessing and etching steps utilizing a bump based size mask. This is followed by patterning an underlying seed layer with a second, larger mask, thereby preventing damage to the aluminum cap and seed layer undercut during the etching process.