AVS 53rd International Symposium
    Plasma Science and Technology Thursday Sessions
       Session PS2-ThA

Paper PS2-ThA6
Edge Effects in Reactive Ion Etching: The Wafer- Focus Ring Gap*

Thursday, November 16, 2006, 3:40 pm, Room 2011

Session: Plasma Modeling
Presenter: N.Y. Babaeva, Iowa State University
Authors: N.Y. Babaeva, Iowa State University
M.J. Kushner, Iowa State University
Correspondent: Click to Email
The termination of the edge of the wafer in reactive ion etching is important to obtaining uniform reactants (composition, magnitude and energy) across the entire substrate. The use of focus rings is designed to maintain a seamless transition of reactants across the edge of the wafer. Non-optimum termination may result in a larger than desired edge exclusion where useful product cannot be obtained. There is an unavoidable gap between the edge of the wafer and terminating structures, such as focus rings. The issue we have investigated is how influential the wafer-focus ring gap is in affecting the uniformity of reactants across and to the edge of the wafer and in affecting the ion flux into the gap. The latter is important in that the ion flux may be incident on the side edge or the bottom of the wafer in the case of beveled edges. This investigation was performed with a fluid model having an unstructured mesh that enables resolution of a large dynamic range in spatial scales and arbitrary shapes. The modeling platform, nonPDPSIM, was improved by incorporating ion momentum equations and ion drag on neutrals. Results will be presented for RIE plasmas sustained in Ar, Ar/Cl@sub 2@ and Ar/fluorocarbon systems at tens of mTorr. The width and depth of the wafer-focus ring gap was varied for different powers and frequencies. @FootnoteText@ *Work supported by Semiconductor Research Corp. and the National Science Foundation.