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

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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.