| AVS 56th International Symposium & Exhibition | |
| Plasma Science and Technology | Thursday Sessions |
| Session PS1-ThA |
| Session: | Fundamentals of Plasma-Surface Interactions II |
| Presenter: | G.K. Choudhary, University of California, Berkeley |
| Authors: | G.K. Choudhary, University of California, Berkeley J.J. Végh, University of California, Berkeley D.B. Graves, University of California, Berkeley |
| Correspondent: | Click to Email |
The effects of ion bombardment on polymer surfaces can be profound, with implications for all plasma-based pattern transfer processes that involve the use of polymer etch masks in lithography and etching. It is known that Ar+ bombardment of various polymers results in the formation of a 1-2 nm deep cross-linked region at the exposed surface, and that virgin polymer sputtering yields can be several orders of magnitude higher than steady state yields after ion bombardment. [1]
In this talk, we report results from molecular dynamics (MD) simulations of Ar+ (~ 40 - 150 eV) sputtering of oxygen-containing polymers. The MD data are compared to available experimental results, with special focus on the so-called Ohnishi parameter, which has been shown to correlate with sputtering yields for many O-containing polymers. [2] The MD simulations match the published correlations well, and we present a quantitative model of sputtering for these polymers that shows why the Ohnishi parameter (a function of the polymer composition) is proportional to the steady state sputtering yield.
However, we also show that the Ohnishi parameter does not correlate with yields for other polymers, including polyfluoroethylene and polyethylene. The MD simulations show that the validity of this parameterization is dependent on whether or not the sputtering of the polymer transitions between ion-induced scissioning to cross-linking at steady-state.
Finally, we discuss the implications of the dynamics of ion-induced surface cross-linking for synergistic photoresist roughening that occurs in plasmas, especially in the presence of vacuum ultraviolet photon and/or beaming electron exposure.
[1] J. J. Végh, D. Nest, D. B. Graves et al. ” Near-surface modification of polystyrene by Ar+: molecular dynamics simulations and experimental validation” Applied Physics Letter, vol. 91, pp. 233113-1-3, 2007.
[2] H. Gokan, S. Esho, and Y. Ohnishi, “Dry etch resistance of organic materials,” J. EZectrochem. SOC., vol. 130, pp. 143-146, 1983.