Patent ID: 8025812

Claim:
A chemical etchant for etching titanium-tungsten alloys in microelectronics fabrication of capture pads for C4 solder bumps in the presence of one or more metals not to be etched, the etchant consisting essentially of: an aqueous solution maintained at a temperature between about 25° C. and 60° C. comprising; about 5% to 12% by weight of solution of H 2 O 2 ; about 0.06% to 0.6% by weight of solution of phosphate ions; an amount of a pH adjusting material to provide the aqueous solution with a pH of about 4-6; and the balance H 2 O, wherein said aqueous solution does not etch one or more metals selected from the group consisting of copper, copper/nickel, and copper/nickel alloys.