Reactive ion etching with end point detection of microstructured Mo/Si multilayers by optical emission spectroscopy

Abstract

Reactive Ion Etching (RIE) of Mo/Si multilayers (MLs) with double layer thicknesses of about 10 nm and total layer thicknesses between 80 nm and 300 nm prepared by electron beam deposition onto Si or oxidized Si substrates was investigated in a fluorine based plasma. Patterns with line widths in the range of 200 nm to several microns produced by e-beam- and UV-lithography were transferred into the MLs. For this application it is necessary to stop the etching process just after the ML is totally removed. For end point detection optical emission spectroscopy was used. The plasma was analyzed by optical emission spectroscopy and a significant drop of the atomic fluorine concentration at the multilayer/substrate interface was observed. An algorithm was developed to stop the etching process at the end point. AFM and TEM measurements show that the ML is totally removed and an over-etching of less than 6 nm occurs.