Measurement of Silicon Dioxide Film Thicknesses by X-ray Photoelectron Spectroscopy

Published

February 1, 2001

Author(s)

Cedric J. Powell, Aleksander Jablonski

Abstract

It is now customary for the effects of elastic-electron scattering to be ignored in measurements of the thicknesses of overlayer films by X-ray photoelectron spectroscopy (XPS). It is known, however, that elastic scattering can cause the effective attenuation length (EAL), needed for the thickness measurement, to be often different from the corresponding inelastic mean free path (IMFP). We have investigated the effects of elastic-electron scattering in measurements of thicknesses of SiO ₂ films on Si from XPS measurements with Al and Mg Kα x rays. Calculations were made of substrate and oxide Si 2p photoelectron currents for different oxide thicknesses and emission angles using an algorithm based on the transport approximation. This algorithm accounts for the occurrence of elastic scattering along electron trajectories in the solid. The calculations simulated an angle-resolved XPS experiment in which the angle between the x-ray source and the analyzer axis was 54 degrees. It was found that the average EAL, determined from the substrate currents with and without an oxide overlayer of a certain thickness, varied weakly with oxide thickness and emission angle α for a restricted range of emission angles. For emission angles equal to or less than 55 degrees and for oxide thicknesses such that the substrate current was reduced to not less than 1 % of its original value, the average EAL was between 0.89 and 0.93 of the corresponding IMFP for Mg Kα x rays and between 0.90 and 0.94 for Al Kα x rays. For emission angles between 60 degrees and 80 degrees; the average EAL was between 0.92 and 1.33 of the IMFP for Mg Kα x rays and between 0.93 and 1.30 of the IMFP for Al Kα x rays.

Proceedings Title

Characterization and Metrology for ULSI Technology 2000, International Conference | | Characterization and Metrology for ULSI Technology |AIP

Volume

550

Conference Dates

June 26-29, 2000

Conference Title

AIP Conference Proceedings

Pub Type

Conferences

Keywords

effective attenuation lenth, elastic-electron scattering, film thickness, inelastic mean free path, silicon, silicon dioxide, xray photoelectron spectroscopy

Citation

Powell, C. and Jablonski, A. (2001), Measurement of Silicon Dioxide Film Thicknesses by X-ray Photoelectron Spectroscopy, Characterization and Metrology for ULSI Technology 2000, International Conference | | Characterization and Metrology for ULSI Technology |AIP (Accessed April 24, 2024)