Optical Spectroscopy in Reactive Sputter Etching and Its Application to Process Control

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Abstract
Optical emission spectra in the reactive sputter etching (RSE) of Si, SiO2 and Si3N4 have been investigated using a spectrometer with a collimating system. Emission lines of Si, F, CN and N2 reflecting the reaction products in the RSE of Si3N4 were observed. From the dependence of these lines on the etching conditions, the active species in RSE was found to be not F radicals, but CF x ions. The applicability of these lines for use as the end point monitor was also investigated. In addition, the plasma gas temperature was determined by rotational analysis of plasma etching and RSE in C2F6 gas mixed with O2 or C2H4 gas.