Measurement of the interface layer thickness in SiO2/Si structures by single-wavelength null ellipsometry

A procedure for the determination of the interface layer thickness between the bulk SiO2 film and the Si substrate from single-wavelength null ellipso metric data is described. The effect of the angular errors in the angle of incidence is eliminated because it is found along with the film and interfa ce layer thicknesses. Optimum film thickness ranges minimizing the propagat ion of angular errors in measured ellipsometric quantities are deduced from error analyses. Immersion ellipsometry is thus shown to reduce further the effect of these errors. A 10 Angstrom interface layer can thus be determin ed within 10 +/- 2 Angstrom under these conditions. The dominant uncertaint y produced in the interface layer thickness obtained from the ellipsometric angles measured to one or a few hundredths of a degree under these conditi ons is only due to the inaccurate knowledge of the interface layer refracti ve index. A minimum thickness for the interface layer mag be specified at a particular value of the refractive index irrespective of its real value, T he procedure is illustrated regarding these results with determining the in terface layer thickness from simulated and experimental data on SiO2/Si str uctures. (C) 1998 John Wiley & Sons, Ltd.