Understanding CMP-induced delamination in ultra low-k/Cu integration

Abstract

In-situ friction characterization during chemical-mechanical polishing (CMP) was investigated to understand delamination mechanisms of a porous ultra low-k (ULK)/Cu stack. By quantifying the delaminated area within the wafer, it was shown that adhesion failure is driven by the work done against the CMP-induced friction force, and is correlated to the adhesion strength of the weakest interface. A low-stress CMP was successfully achieved on a first level of ULK/Cu interconnects having a low adhesion SiC/ULK interface (Gc=1.3 J/m/sup 2/) and a porous dielectric material with low mechanical properties (Young's modulus E=3.5 GPa, hardness H=0.7 GPa).