Measurement of Thicknesses of High-$\kappa $ Gate-Dielectric Films on Silicon by Angle-Resolved XPS

We report on the use of a new NIST database for the Simulation of Electron Spectra for Surface Analysis (SESSA) in measuring thicknesses of candidate high-$\kappa $ gate-dielectric materials (HfO$_{2}$, HfSiO$_{4} $, ZrO$_{2}$, and ZrSiO$_{4})$ on silicon by angle-resolved XPS. For conventional measurements of film thicknesses, effective attenuation lengths (EALs) have been computed for these materials from SESSA as a function of film thickness and photoelectron emission angle (i.e., to simulate the effects of tilting the sample). These EALs are believed to be more accurate than similar EALs obtained from the transport approximation because realistic cross sections are used for both elastic and inelastic scattering in the film and substrate materials. We also present ``calibration curves'' showing calculated ratios of selected photoelectron intensities from thin films of HfO$_{2}$ on Si with an intermediate SiO$_{2}$ layer. These ratios provide a simple and convenient means of determining the thicknesses of SiO$_{2}$ and HfO$_{2}$ films for particular measurement conditions.