Reflectance of thinly oxidized silicon at normal incidence.

Calculated values of reflectance at normal incidence for thinly oxidized silicon wafers are presented. The calculations, which use published, experimentally derived optical constants, cover the spectral range from ultraviolet (0.38 microm) to near infrared (1.24 microm). Oxide thickness varied in 0.1-microm steps from 0 to 1 microm, the range of practical interest to technologists in silicon and integrated circuits. Reflectance curves are correlated with the interference color chart for oxidized silicon. Finally, the dependence of reflectance on oxide thickness at three common laser wavelengths is graphed, for those interested in the recently developed endpoint detection techniques of plasma etching.