In Situ Investigation of Amorphous Silicon / Silicon Nitride Interfaces by Infrared Ellipsometry

ABSTRACTA detailed in situ study, by Infrared Phase Modulated Ellipsometry (IRPME), of interfaces between amorphous silicon (a-Si:H) and silicon nitride (a-SiNx) is presented. A behaviour compatible with a sharp interface is observed when a-SiNx is deposited on top of a-Si:H, the underlayer material being very weakly influenced by the deposition of the overlayer. In contrast a graded transition is observed when a-SiNx is deposited first. In the latter case, the IR measurements directly reveal a nitrogen incorporation in the first monolayers of a-Si:H together with an increase of intensity of the SiH bonds at the interface.