A novel integrated scheme to improve the electrical and electromigration performance of Cu interconnects

Process variations such as post etch cleaning, pre-cleaning prior to Cu barrier/seed deposition and Cu annealing can yield significant differences in electromigration (EM) failure populations even while maintaining general microstructure consistency. In this paper, focus-ion-beam (FIB) cross-sectional imaging is used to reveal how bimodal EM failures originate. In addition, a novel integrated scheme with an optimized post etch clean after nitride breakthrough, in-situ H₂ contained precursor treatment prior to Cu barrier/seed deposition and an optimized Cu anneal condition is introduced to improve the electrical and eliminate the bimodal EM failures of Cu interconnects.