Comparison of the Tougaard, ARXPS, RBS and ellipsometry methods to determine the thickness of thin SiO2 layers

The Tougaard and angle-resolved x-ray photoelectron spectroscopy (ARXPS) methods were compared with ellipsometry and Rutherford backscattering (RBS) for their ability to determine the amount Of SiO2 on an Si substrate. The Tougaard and ARXPS methods give generally consistent results (root-mean-square deviation similar to12%), whereas the deviation between the other techniques is significantly larger (similar to30-40%). The Tougaard method gives consistent results for all angles of emission theta less than or equal to 60degrees. It is found also that the amount of SiO2 determined by the two methods depends approximately linearly on the inelastic mean free path. The ARXPS method also depends on the accuracy with which one can separate the peak area of the bulk and the oxide part of the peaks. The correction for elastic scattering in the ARXPS method gives a reduction of only 5-7% in the determined amount Of SiO2. Copyright (C) 2002 John Wiley Sons, Ltd.