Spectral ellipsometry analysis of ultrathin amorphous silicon layers
Ultrathin layers of hydrogenated amorphous silicon (a-Si:H) are of high interest in todayâ s photovoltaics. A reliable characterization (layer thickness, optical constants) of such layers is essential for process control and development. Spectral ellipsometry is a fast and non-destructive method for analyzing thin layers. A common analysis procedure for ellipsometric data fails in case of ultrathin a-Si:H layers with thicknesses below 15 nm. For evaluation of such a-Si:H layers a new analysis procedure has been introduced. The procedure has been applied successfully to layers of a thickness down to 5 nm, verified by reflection and transmission measurements as well as transmission electron microscopy.