Etching characteristics of Ta and TaN layers on SiO2 were investigated in Cl-2/Ar inductively coupled plasmas. Etch rate and selectivity to the photoresist and SiO2 under-layer were measured by varying Cl-2/Ar gas mixing ratio, the top electrode power, and the bottom electrode power. The etch rate results combined with OES and XPS measurements for the Cl radicals in the plasma and the etched surfaces, respectively, suggest that Cl radicals play an important role in determining the etch rates of Ta and TaN, in which the radical density is greatly affected by the percentage of Ar in the etch gas. Etch selectivities of Ta/SiO2 and TaN/SiO2 were increased with increasing the Cl-2/(Cl-2 + Ar) flow ratio. Increase in the bottom electrode power generally increased the SiO2 etch rate and, as a result, decreased the Ta and TaN etch selectivity over SiO2 significantly. (c) 2005 Published by Elsevier B.V.