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

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.