Reliable Au Wire Bonding to Al/Ti/Al Pad

Abstract

In this paper, we describe bond degradation and the bondability of an Au wire to a thin-Al/Ti/Al pad. It is found that the pad structure of Al(300 nm)/Ti(300 nm)/Al(1000 nm) is useful for the prevention of bond degradation upon heat treatment at 473 K for 3.6 Ms. Use of the pad necessitated an annealing temperature of at least 723 K, because of its lower initial bond resistance. With heat treatment after thermosonic ball bonding, the bond resistance is almost invariable and the bond shear strength does not decrease. The life of the bond between the Au wire and the pad is extended with thickening of the Ti layer.