Real case studies of failure mechanisms for Cu trench electromigration

The morphology of voids formed during electromigration testing of Cu lines provides important clues to solve process-related problems. In this work, deep and isolated voids are found in samples with shorter life times, while long and shallow voids are found in the ones with longer life times. Serious overetching of the SiN trench etching stop layer is found in early failures and result in nucleation of voids from the sidewalls of trenches.