Aluminum bump, reworkable bump, and titanium nitride structure for tab bonding

摘要

A semiconductor chip carrying integrated circuits has lead lines terminating in conductive terminal pads exposed to the exterior through openings in a passivation layer. The pads include pedestals or bumps extending up from them. Each of the pedestals includes a thin metallic adhesion layer deposited on the pad. A thick metallic layer of aluminum or an alloy of aluminum is deposited upon said thin metallic adhesion layer. The thick metallic layer includes at least one metal selected from the group consisting of aluminum, aluminum plus a small percentage of Cu, Ni, Si, or Fe. Several other alternative metals can be added to aluminum to form an alloy. The thick metallic layer forms the bulk of the height of the pedestal. An adhesion layer is deposited on the bump of aluminum composed of a thin film of titanium or chromium. A barrier layer is deposited on the adhesion layer composed of copper, nickel, platinum, palladium or cobalt. A noble metal consisting of gold, palladium, or platinum is deposited on the barrier layer. In a variation of the top surface, a thick cap of a reworkable bonding metal is deposited above the metallic bump as the top surface of said bump. The bump can be composed of a number of metals such as gold, copper, nickel and aluminum in this case with aluminum being preferred. In place of the adhesion and barrier metals one can employ a layer of titanium nitride deposited on said thick layer of metal.