The Influence of Plasma Silicon Nitride Passivation Film Quality on Aluminum Void Formation

Voiding in wide aluminum interconnects at high-temperature heat-treatment has been studied in conjunction with plasma silicon nitride passivation film formation conditions. Void formation largely depends on the plasma silicon nitride deposition temperature, lower void density for higher temperature deposited films, and higher density voiding for lower temperature deposited films, which cannot be explained by a simple stress model. Experiments are described to study these dependencies and the results are explained by proposing model. The combination of the different temperature dependence of the transient pseudo-elastic stress change and the successive plastic stress relaxation of plasma silicon nitride film induces different stress states in aluminum lines when samples are heated up. The dependence of aluminum void density on the plasma silicon nitride formation condition can be explained with this stress difference.