AVS 45th International Symposium
    Applied Surface Science Division Monday Sessions
       Session AS-MoA

Paper AS-MoA7
XPS Characterization of Nitrogen Profile and Chemical States in Ultrathin Silicon Oxynitrides

Monday, November 2, 1998, 4:00 pm, Room 307

Session: Oxides and Insulators - Surface Characterization and Applications
Presenter: J.P. Chang, Bell Laboratories, Lucent Technologies
Authors: J.P. Chang, Bell Laboratories, Lucent Technologies
M.L. Green, Bell Laboratories, Lucent Technologies
V.M. Donnelly, Bell Laboratories, Lucent Technologies
R.L. Opila, Bell Laboratories, Lucent Technologies
Correspondent: Click to Email
Continuous scaling of the gate dielectric thickness to @<=@ 40Å makes X-ray photoelectron spectroscopy (XPS) a viable technique for analyzing the composition and stoichiometry of a thin film and its interface with silicon, since the film thickness is comparable to the escape length of photoelectrons. Photoemission of various species is acquired at different take-off angles, and the maximum entropy method is employed to convert the angular dependent photoemission intensities to compositions as a function of depth.@footnote 1,2@ Angular resolved XPS (ARXPS) analysis permits nondestructive characterization of the nitrogen profile and interfacial compositions of ultrathin silicon oxynitride films grown by furnace oxidation. The incorporation of nitrogen in SiO@sub 2@ improves the electrical reliability and prevents boron penetration. In this work, nitric oxide (NO) and oxygen gases have been used to engineer the nitrogen profile in SiO@sub 2@ films. With furnace growth at 800°C, 1-4 at. % of nitrogen can be incorporated in the ultrathin (@<=@ 40Å) oxide films. Additional nitrogen can be incorporated by plasma ion nitridation. The nitrogen profile and nitrogen chemical bonding states are analyzed as a function of the depth to understand the mechanism of nitrogen incorporation during the NO/O@sub 2@ thermal growth process. Reoxidation of a thermal oxide grown in NO leads to a peak nitrogen concentration at the upper oxide interface, ideal to prevent boron penetration. Annealing of thermal oxide in NO leads to a peak concentration of nitrogen at the SiO@sub 2@/Si interface. Nitrogen bonds primarily to silicon at low total nitrogen content (1-4 at. %), but also bonds to oxygen at higher total nitrogen content. The improved reliability as determined by charge to breakdown (Q@sub bd@) measurement will be correlated with compositions and stoichiometry of the bulk film and its interfaces. The mechanism of nitrogen incorporation in NO or plasma ion nitridation will be discussed. @FootnoteText@ @footnote 1@G. C. Smith and A. K. Livesey, Surf. and Interface Anal. 19, 175 (1992). @footnote 2@N. Layadi, V. M. Donnelly, and J. T. C. Lee, J. Appl. Phys., 81, 6738 (1997).