Ellipsometric determination of optical constants for silicon and thermally grown silicon dioxide via a multi-sample, multi-wavelength, multi-angle investigation

Authors

C. M. Herzinger, J. A. Woollam Co.
B. Johs, J. A. Woollam Co.
W. A. McGahan, J. A. Woollam Co.
John A. Woollam, J. A. Woollam Co.Follow
W. Paulson, Advanced Products Research and Development Lab, Motorola, 3501 Ed Bluestein, Austin, Texas

Date of this Version

3-15-1998

Comments

Published in J. Appl. Phys., Vol. 83, No. 6, 15 March 1998. © 1998 American Institute of Physics. Used by permission.

Abstract

Optical constant spectra for silicon and thermally grown silicon dioxide have been simultaneously determined using variable angle of incidence spectroscopic ellipsometry from 0.75 to 6.5 eV. Spectroscopic ellipsometric data sets acquired at multiple angles of incidence from seven samples with oxide thicknesses from 2 to 350 nm were analyzed using a self-contained multi-sample technique to obtain Kramers–Kronig consistent optical constant spectra. The investigation used a systematic approach utilizing optical models of increasing complexity in order to investigate the need for fitting the thermal SiO₂ optical constants and including an interface layer between the silicon and SiO₂ in modeling the data. A detailed study was made of parameter correlation effects involving the optical constants used for the interface layer. The resulting thermal silicon dioxide optical constants were shown to be independent of the precise substrate model used, and were found to be approximately 0.4% higher in index than published values for bulk glasseous SiO₂. The resulting silicon optical constants are comparable to previous ellipsometric measurements in the regions of overlap, and are in agreement with long wavelength prism measurements and transmission measurements near the band gap.