AVS 45th International Symposium
    Electronic Materials and Processing Division Wednesday Sessions
       Session EM1-WeA

Paper EM1-WeA7
Structure of Ultrathin Silicon Oxide - Silicon Interfaces Studied by Ultraviolet Photoelectron Spectroscopy

Wednesday, November 4, 1998, 4:00 pm, Room 314/315

Session: Si Surface Chemistry
Presenter: J.W. Keister, North Carolina State University
Authors: J.W. Keister, North Carolina State University
J.E. Rowe, North Carolina State University
J.J. Kolodziej, Rutgers University
H. Niimi, North Carolina State University
T.E. Madey, Rutgers University
G. Lucovsky, North Carolina State University
Correspondent: Click to Email
Device-grade ultrathin (9-18 Å) films of silicon dioxide, prepared from crystalline silicon by remote-plasma oxidation, are studied by the surface-sensitive method of ultraviolet photoelectron spectroscopy. The 2p core-level spectra for silicon (at ~100 eV binding energy) show evidence of five distinct states of Si. These peaks are attributed to the five oxidation states of silicon between 0 (the Si substrate) and +4 (the thin SiO@sub 2@ film), although the precise configuration has recently been called into question.@footnote 1@ We find that the peaks for Si@super 1+@ through Si@super 4+@ are shifted relative to the Si@super 0@ bulk peak to higher binding energy by 0.92 eV, 1.90 eV, 2.51 eV and 3.86 eV. The relatively weaker signal found for the three intermediate states (+1, +2, and +3) is attributed to silicon atoms at the interface between these two materials. Estimates of the interface thickness from the intermediate valence signal agree with the value reported earlier of 3-5 Å (~ 2 ML).@footnote 2,3@ In this work, the position and intensity of the five peaks are measured as a function of post-growth annealing temperature (700 - 900 °C), crystal orientation, and incorporation of N@sub 2@ in the reactant gas flow. One result we have found is that annealing produces more abrupt interfaces, but never more abrupt than about one or two monolayers. This comes from the observation of a sudden drop in the interface thickness (in particular the Si@super 2+@ peak intensity) upon reaching 800-900 °C annealing temperature. A more complete and quantitative analysis will be presented which explores the effects of the other sample parameters and takes advantage of nonlinear least-squares fitting routines. @FootnoteText@ @footnote 1@McFeely, Zhang, Banaszak-Holl, Lee, Bender J. Vac. Sci. Tech. B 14(4), 2824-2831 (1996). @footnote 2@Himpsel, McFeely, Taleb-Ibrahimi, Yarmoff, Hollinger, Phys. Rev. B 38, 6084-6096 (1988). @footnote 3@Himpsel, Meyerson, McFeely, Morar, Taleb-Ibrahimi, Yarmoff Core Level Spectroscopy at Silicon Surfaces and Interfaces, in Campagna and Rosei, eds. Photoemission and Absorption of Solids and Interfaces with Syncrotron Radiation (Proceedings of the International School of Physics "Enrico Fermi", Course CVIII, Varenna, Italy. 1988.) North-Holland/Elsevier Science Publishers: 1990, pp. 203-236.