Three kinds of via electromigration failure mode in multilevel interconnections

Abstract

The via electromigration performance of four metallization systems has been investigated for via chains of 1500-4400 vias of 1.0 mu m diameter. AL(AL/Ti), (Al/Ti)AL, and AL/(WSi/AL) metallization systems have longer electromigration lifetime than AL/AL. The via failures have been analyzed by the contrast scanning ion microscope technique. Further failure analysis by focused ion beam milling on the opened via has revealed that at least three kinds of failure modes exist for via electromigration. Models for the failure mechanism in each metallization system are discussed.<>