With reduction of ULSI feature size, copper becomes wiring layers on silicon materials in deep submicron technics(0.18 um and below) and tantalum(Ta) barrier layer is the best choice to prevent the diffusion of copper to silicon. In the copper CMP process, dishing occurs due to the inconsistent removal rate of copper and Ta; In addition, the metal ion contamination is a serious problem. In this paper, a kind of alkaline slurry with high concentration of nano-silica sol as abrasive and hydrogen peroxide as oxidant was studied for final CMP of Cu/Ta. Oxidizer and complexation of polishing slurry has important influence on the polishing rate because of the different properties of copper and Ta. By reducing slurry oxidation, improving the complexing effect and accelerating the formation of soluble products of the Ta to be removed, the removal rate of copper decreased whilst that of Ta enhanced to get to the same.
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