ANNEALING BEHAVIOR OF THE SPECIFIC CONTACT LAYER RESISTIVITY FOR AN AU BUMP-TIW-AL PAD STRUCTURE

The specific contact layer resistivity between gold bumps and aluminiu m pads with a TiW barrier layer has been determined. It is about 1.2-1 .5 OMEGA mum2 and increases visibly after heat treatment at temperatur es greater than 350-degrees-C for 1 h but only increases a little belo w temperatures of 350-degrees-C. The processes are associated with the formation of intermetallic compounds which is governed by diffusion o f metallic elements. The activation energy of the processes was determ ined to be 1.15 eV, which is more than that for the structures without a TiW barrier layer. The barrier function of the TiW layer has been c onfirmed.