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Journal of the Electrochemical Society, Vol.149, No.1, G41-G50, 2002
Evolution of copper-oxide damascene structures in chemical mechanical polishing - II. Copper dishing and oxide erosion
Test wafers comprising damascene structures were designed and fabricated to investigate Cu dishing and oxide erosion. The mask design covered a wide range of linewidths and pitches, from 0.5 to 100 mum, to represent such features as signal and power transmission lines, and probing or wire-bonding pads. Experiments were conducted to investigate the evolution of the pattern profile during polishing and to determine the onset and rates of dishing and erosion. The effects of Cu linewidth and area fraction on the rates of pattern planarization, Cu dishing, and oxide erosion have been quantified. The effect of hardness of the composite surface on dishing and erosion were examined. An optimization scheme, employing particle size, particle hardness, and pad stiffness, to enhance the selectivity between SiO2, Ta, and Cu, and to reduce die-scale nonplanarity is proposed.