AVS 45th International Symposium
    Plasma Science and Technology Division Friday Sessions
       Session PS-FrM

Paper PS-FrM10
Surface Chemistry of NF@sub 3@ Plasma and Si Surface Interaction

Friday, November 6, 1998, 11:20 am, Room 318/319/320

Session: Plasma-Surface Interactions - II
Presenter: T.W. Little, University of Washington
Authors: T.W. Little, University of Washington
A. Endou, Tohoku University, Japan
A. Miyamoto, Tohoku University, Japan
M. Kitajima, National Research Institute for Metals, Japan
F.S. Ohuchi, University of Washington
Correspondent: Click to Email
As an etchant gas, nitrogen trifluoride (NF@sub 3@) has become a viable contender to such mainstays in the semiconductor industry as carbon tetrafluoride (CF@sub 4@) and other perfluorocarbon compounds (PFCs) for certain plasma etching applications involving silicon (Si). Despite the technological importance of NF@sub 3@, there have been almost no studies on the interaction of NF@sub 3@ with Si from a surface science point of view. We have used x-ray photoelectron spectroscopy (XPS) and other diagnostics to determine the chemistry of interaction of NF@sub 3@ and Si surfaces. Although XPS results for the Si 2p core level are similar to those found for other etchants, we have seen unusual behavior in the F 1s core level and F 2s quasi-core level spectra. In addition to a F peak resulting from Si-F bonds, there are significant high-binding energy components which indicate that F is assuming a more positive or even neutral charge. The appearance of these peaks is closely related to both the type and amount of diluent gas. Upon heating, the high binding energy components are seen to disappear. These results lead to the supposition that F may be incorporated into the Si lattice as a result of an ion bombardment damage mechanism. While XPS is sensitive to changes in local chemistry, we have also applied a novel, in-situ Raman scattering technique which is sensitive to plasma surface interactions before they have progressed to the state in which chemical changes can be measured by XPS. The results of these measurements are described and compared with results obtained from XPS and other analytical techniques. In an effort to understand the energetics of F interaction with the Si lattice, we have also used cluster calculations to determine the most likely F sites.