AVS 52nd International Symposium
    Electronic Materials and Processing Tuesday Sessions
       Session EM2-TuM

Paper EM2-TuM10
Measurement of Thicknesses of HfO@sub 2@, HfSiO@sub 4@, ZrO@sub 2@, and ZrSiO@sub 4@ Films on Silicon by Angle-Resolved XPS

Tuesday, November 1, 2005, 11:20 am, Room 312

Session: High-k Dielectric Characterization
Presenter: C.J. Powell, National Institute of Standards and Technology
Authors: W. Smekal, Vienna University of Technology, Austria
W.S.M. Werner, Vienna University of Technology, Austria
C.J. Powell, National Institute of Standards and Technology
Correspondent: Click to Email
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@sub 2@, HfSiO@sub 4@, ZrO@sub 2@, and ZrSiO@sub 4@) on silicon by angle-resolved XPS. Practical effective attenuation lengths (EALs) have been computed from SESSA as a function of film thickness and photoelectron emission angle (i.e., to simulate the effects of tilting the sample). EALs have been calculated in two ways. First, realistic (Mott) cross sections have been used to describe the elastic scattering of the signal electrons in the substrate and overlayer film; appropriate inelastic mean free paths have also been selected for each material. Second, the transport approximation (TA) has been utilized in which isotropic elastic-scattering is assumed; in addition, it is assumed that elastic- and inelastic scattering parameters for the film can also be used for the substrate. These EALs have been compared with similar values obtained from the NIST Electron Effective-Attenuation-Length Database (SRD 82) that utilizes an algorithm based on the TA (and where it is again assumed that substrate and overlayer have similar scattering properties). Excellent agreement is found between EALs from SRD 82 and those from SESSA with the TA. Generally good agreement was found between these EALs and those from SESSA with the Mott cross sections, but there were some differences for film thicknesses less than the inelastic mean free path of the photoelectrons in the high-@kappa@ material. The SESSA EALs with the Mott cross sections are considered more reliable than those from the TA because realistic cross sections are used for both elastic and inelastic scattering in the film and substrate materials. These EALs should thus provide more accurate measurements of film thickness, particularly in applications where the film and substrate have different electron-scattering properties.