ELLIPSOMETRY FOR RAPID CHARACTERIZATION OF SI1-XGEX LAYERS

We report on the ability of ellipsometry to rapidly determine the germanium content and the film thickness of Si1-xGex layers deposited on silicon substrates. The technique is used to evaluate thickness on single- and for the first time, double-layer Si/SixGe1-x films. We estimate the refractive index of Si1-xGex from ellipsometry measurements and find that only the real part differs significantly from that of silicon for 0 < x < 0.30. We examine the sensitivity of ellipsometry to changes in germanium content and film thickness. We find that sensitivity is cyclical with film thickness and, in the best case, ellipsometry can be used to determine germanium content within +/- 1 at. % or thickness within +/- 20 angstrom for x approximately 0.10.