Detection of thin a-Si:H antireflective coatings on oxidized c-Si by resonant-detected spectroscopic ellipsometry

The cleaning procedures applied in the wafer processing of thin a-Si:H overlayers have been monitored by spectroscopic ellipsometry. By selecting a suitable sample configuration and exploiting a tunable angle of incidence, we show that spectroscopic ellipsometry is extremely sensitive to small modifications at the vacuum-a-Si:H interface induced by the cleaning procedures. Experimental results are presented on the characterization of thin (3-12-nm) a-Si:H films on top of thermally oxidized crystalline silicon. Submonolayer sensitivity of the ellipsometric measurement to changes in a-Si:H film thickness is shown.