Void formation failure mechanisms in integrated circuits

The several interfacial regions where voids and electrical opens occur in semiconductor discrete devices and monolithic integrated circuits are described. The metals used at these interfaces in circuits today are listed and a description is given of the void-producing mechanisms applicable to each area, along with techniques for their detection. Voids which develop in the bond of gold wire, which is ball bonded to aluminum metalization as a result of intermetallic purple plague formation, are explained as an example of the Kirkendall effect. However, the faster diffusion of one of the metals of a bond producing voids cannot explain the observation of voids in both the gold and the aluminum side of the bond. Recent thin film experiments account for this effect by a process which is rate limited by diffusion through the newly formed intermetallic phase. Analysis of five newer alternate metalization systems for circuits show them all to have the potential for compound formation, which may be expected to be accompanied by void formation.