Dry etching of NiO thin films masked with a photoresist was performed in a Cl 2 /Ar gas mix. The etch rate of NiO films decreased as Cl 2 concentration increased. The surface morphology etched at high Cl 2 concentration was smoother than that etched at low Cl 2 concentration. The etch profiles were improved with increasing coil radio-frequency ͑rf͒ power and dc-bias voltage. An X-ray photoelectron spectroscopy analysis confirms the formation of NiCl 2 compound due to a chemical reaction with

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... orine radicals. These results indicate that the etching of NiO films is governed by a physical sputtering etching mechanism with a surface chemical reaction.