Using a wavelet, a profile nonuniformity was characterized and applied to a tungsten etching conducted in a SF6 helicon plasma. The profile nonumformity was examined as a function of process parameters, including radio frequency source power, bias power, SF6 flow rate, and substrate temperature. It was correlated to the etch rate nonumformity or the fluorine radical measured by an optical emission spectroscopy. The profile nonumformity increased with increasing all parameters but the source power. Etch mechanisms were estimated by investigating the nonuniformity dependency on ion or radical density distribution. (C) 2004 Elsevier B.V. All rights reserved.