Microelectronic Engineering 54 (2000) 303–314 www.elsevier.nl / locate / mee Reactive ion etching with end point detection of microstructured Mo / Si multilayers by optical emission spectroscopy a, a a a a a ,1 * L. Dreeskornfeld , R. Segler , G. Haindl , O. Wehmeyer , S. Rahn , E. Majkova , a a b b U. Kleineberg , U. Heinzmann , P. Hudek , I. Kostic a ¨ ¨ ¨ ¨ Fakultat f ur Physik, Universitat Bielefeld, Universitatsstr. 25, D-33615 Bielefeld, Germany b Institute of Informatics, Slovak Academy of Sciences, 84237 Bratislava, Slovakia Accepted 20 October 1999 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.  2000 Elsevier Science B.V. All rights reserved. Keywords: Reactive Ion Etching (RIE); Optical Emission Spectroscopy (OES); End point detection; Multilayer 1. Introduction Recently, an increased interest has been paid to the lateral structuring of periodic multilayers (MLs). The important property of these structures is that they are compositionally modulated in the direction perpendicular to the film plane. Laterally structured MLs with the feature size in submicron range revealed interesting magnetic, superconducting, electronic transport properties. Laterally patterned MLs with normal as well as lateral periodicities are important elements in XUV optics. E.g. ML gratings are superior both to simple multilayers and laminar gratings because of a high throughput and a high spectral resolution [1]. *Corresponding author. E-mail address: ldreesko@uni-bielefeld.de (L. Dreeskornfeld). 1 Permanent address: Institute of Physics, Slovak Academy of Sciences, 84228 Bratislava, Slovakia. 0167-9317 / 00 / $ – see front matter  2000 Elsevier Science B.V. All rights reserved. PII: S0167-9317(99)00449-9