MEASUREMENT OF THE THICKNESS AND OPTICAL-PROPERTIES OF THERMAL OXIDES OF SI USING SPECTROSCOPIC ELLIPSOMETRY AND STYLUS PROFILOMETRY

Thermal oxides of Si were grown in dry oxygen at 1000-degrees-C. Spectroscopic ellipsometry measurements were performed on these samples over the photon energy range from 1.6-5.0 eV. Effective medium modeling of these measurements was used to determine the thicknesses of the oxides and their effective refractive indexes. The oxide thicknesses were also measured directly using high accuracy stylus profilometry. The thickness values obtained using the two techniques differed by an average of +/- 5 angstrom. The effective refractive indexes of the oxides were found to be significantly larger than those of fused silica. The larger values result from the larger densities of the thermal oxides as compared to fused silica. The thermal oxides were found to have an average density 1.91% greater than that of fused silica. This density increase, and consequent large effective refractive indexes for the samples, is discussed in the context of previous ellipsometry studies on thermal oxides of Si. In addition, a procedure is described in which spectroscopic ellipsometry measurements can be used, with no analysis, to determine the optical properties of the substrate.