Effect of CMP downward pressure on nano-scale residual stresses in dielectric films with Cu interconnects assessed by cathodoluminescence spectroscopy

Engineering of the residual stress fields related to the backend process of LSI devices with Cu interconnects is required together with the adoption of low-k materials that have quite low Young´s modulus. We measured the nano-scale residual stresses stored within interlayer dielectric (ILD) films according to a cathodoluminescence piezospectroscopic technique. We confirmed that stresses in ILD could be successfully detected with less than 50 nm resolution and that a higher chemical mechanical polishing (CMP) downward pressure led to a shift toward the tensile side of the residual stress field stored in the ILD film.