INTERFACE ANALYSIS DURING ETCHBACK OF SILICON-OXIDE

Etching of thermal oxides on Si(100) wafers in acidic fluoride-containing solutions is monitored by simultaneous optical and electrical measurements, the lat-ter including the dark current and the probe light induced photocurrent. For in situ optical characterization a new ellipsometric configuration is used, which allows ac-curate measurements at low probe light intensity. This approach is shown to reduce photocorrosion of the investigated n-doped samples to a level where ellipsometric information about the silicon electrolyte interface becomes accessible. In situ ellipsometric results show some residual film. This is contrasted by ex situ STM giving no evidence for a silicon surface covered with several monolayers of an absorbing film.