Wafers were polished with an experimental slurry containing strong oxidizing components for revealing grain structures. Two types of surface morphologies, twinned and equiaxed grains, were observed on 2 groups of wafers, following chemical mechanical polishing. An atomic force microscope surface analysis indicated that the equiaxed grain structure provided better overall surface quality than did the twinned structure. A polishing model was proposed in order to explain the surface relief among the twinned sub-grains. The results suggested that Cu electroplating and the subsequent annealing processes should be optimized so as to promote uniform equiaxed grains for better integration with chemical mechanical polishing and other processes.

CMP Surface Characteristics of Twinned Copper Subgrains. C.Ni, I.W.Hall, T.M.Thomas, J.K.So, J.Quanci: Journal of Physics D, 2004, 37[17], 2446-8