Wavelet characterization of plasma etch nonuniformity

Using a wavelet, a profile nonuniformity was characterized and applied to a tungsten etching conducted in a SF₆ helicon plasma. The profile nonuniformity 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 nonuniformity or the fluorine radical measured by an optical emission spectroscopy. The profile nonuniformity increased with increasing all parameters but the source power. Etch mechanisms were estimated by investigating the nonuniformity dependency on ion or radical density distribution.