An automatic ellipsometer of picometer sensitivity has been developed for sputtering rate monitoring of extreme ultraviolet multilayer fabrication. With the automatic ellipsometer, the relative amplitude attenuation rho were measured at every 0.2 s during fabrication of a periodic multilayer composed of a 2.9-nm Mo layer and a 4.0-nm Si layer. The recorded data plotted with calibrated thickness by X-ray diffractometry proved the picometer sensitivity needed for 0.1% reflection wavelength matching of the mirror multilayers of nanometer periods. (C) 2003 Elsevier Science B.V. All rights reserved.