SPECTROSCOPIC ELLIPSOMETRY DETERMINATION OF THE PROPERTIES OF THE THIN UNDERLYING STRAINED SI LAYER AND THE ROUGHNESS AT SIO2 SI INTERFACE/

The existence of both the strain and microroughness at the interface o f thermally grown SiO2 films on Si was ascertained unambiguously for t he first time by high accuracy spectroscopic ellipsometry. The dielect ric function of the interface was determined by a comprehensive data a nalysis procedure. By carefully examining the dielectric function obta ined by our model, the strain was seen to cause a red shift of 0.042 e V of the interband critical point E1 compared with the bulk silicon va lue. The thickness of the interface region was found to be 2.2 nm of w hich a significant part is due to the strain.