Uniformity control of etching profile and etching rate across a wafer during damascene etching was investigated using a UHF-ECR etching apparatus with a dual-zone gas-injection system. Uniform etching rate was obtained under various conditions by controlling magnetic field distribution. It was found that etching profile could be controlled without affecting etching-rate uniformity by changing the ratio of inner- to outer-nitrogen-gas flow rate above the wafer. The effect of feed-gas control on radical distribution was evaluated by simulation and measurement of the radical distribution, which showed that controlling the gas-mixing ratio changed the distribution of the nitrogen-to-CFx ratio. With SiOC via hole etching, nanometer-level bottom-CD uniformity at high etching-rate uniformity was obtained. (c) 2006 Elsevier B.V. All rights reserved.