HIGH-PRECISION OPTICAL REFLECTOMETER FOR THE STUDY OF SEMICONDUCTOR-MATERIALS AND STRUCTURES

The design and performance of a high-precision optical reflectometer are described. This instrument has been optimized for measuring the specular reflectivity of thin films and multilayer structures of interest in semiconductor technology. Its design emphasizes high spectral and spatial resolution, photometric accuracy, and stray light rejection. Use of a spectrometer drive linear in wavenumber (energy) and a flexible data acquisition system facilitates data analysis. The performance of the reflectometer is demonstrated using a set of specimens consisting of silicon-dioxide layers on silicon substrates for which the oxide thicknesses had been determined by ellipsometry. Excellent agreement is obtained between the thicknesses derived from the reflectivity spectra and those determined ellipsometrically.