Simultaneous measurement of six layers in a silicon on insulator film stack using spectrophotometry and beam profile reflectometry

We performed simultaneous measurements of all the layer thicknesses in six layer silicon on oxide film structures, Visible-near-infrared spectrophatometry was combined with beam profile reflectometry to produce enough information to discriminate between potential solutions the spectrometer or beam profile reflectometer alone is insufficient to solve such a complicated film stack. Development of a robust measurement recipe required a new global optimization method working in parameter spaces of up to 12 parameters, The recipe obtained was applied to a 50 site mapping of the wafer. We found excellent agreement between our optical measurement results and scanning electron micrograph data fur all thicknesses. (C) 1997 American Institute of Physics.