BGA 44um Fine Pitch Low K Wire Bonding Process Development

With the further shrink of the IC dimension, the low K material has been widely used to replace the traditional SiO2 ILD in order to reduce the interconnect delay, the introduction of low k material into silicon imposed challenges on assembly wire bonding process which is further magnified with the shrink of the bond pad. In this paper, 44um fine pitch CMOS90 nm low k device is chosen to develop the wire bond process capability on BGA package. The low k material structure and its impact on fine pitch wire bonding are introduced, the critical factors (wire type, bonding tool, bonding equipment and bonding parameters) and critical responses Ball size, Ball height / Bonded ball diameter ratio, bond placement, wire pull and ball shear) affecting 44um fine pitch low k wire bonding quality and manufacturability were explored, DOE (design of Experiment) was used to optimize the wire bond process, thermal aging test coupled with wire pull/ ball shear test and their corresponding failure mode was studied. The IMC (Inter Metallic coverage) of the Au-Al was addressed also. The optimized process window/ recipe passed package reliability test with 44um fine pitch C90 low K device.