Analyses of Interface Adhesion between Cu and SiCN Etch Stop Layers by Nanoindentation and Nanoscratch Tests

The interface chemistry and adhesion strength between Cu and SiCN etch stop layers have been investigated to evaluate the reliability of interconnect structures. Analyses of the chemical compositions and bonding configurations reveal that the SiCN etch stop layer was mostly composed of Si to N and Si to C bonding, including Si–N, Si–CN₂, and Si–C₂N. At the Cu/SiCN interface, an oxide layer was observed, and SiCN–O and Cu–O bonding was detected. In nanoindentation and nanoscratch tests, Cu/SiCN interface delamination occurred around indents and along scratch tracks, and the adhesion energy between Cu and SiCN layers was accordingly measured and calculated. The adhesion energy of the Cu/SiCN interface was measured to be about 4.98 J/m² in the nanoindentation test, while that measured using the nanoscratch test was lower, at about 0.98 J/m². The "mode mixity" effect was responsible for the difference between the adhesion energies obtained using these two methods.