AVS 45th International Symposium
    Plasma Science and Technology Division Monday Sessions
       Session PS-MoM

Paper PS-MoM6
The Influence of Insulator Charging on Ion Scattering and Feature Evolution During Plasma Etching

Monday, November 2, 1998, 10:00 am, Room 318/319/320

Session: Feature Evolution
Presenter: M.A. Vyvoda, University of California, Berkeley
Authors: M.A. Vyvoda, University of California, Berkeley
D.B. Graves, University of California, Berkeley
Correspondent: Click to Email
As aspect ratios of structures etched during semiconductor device fabrication increase, the flux of scattered ions from sidewall surfaces can become a significant component of the total ion flux to the feature bottom. Previous work@footnote 1@ has suggested that details of this scattering can strongly affect the ultimate shape of the feature bottom and therefore the success or failure of the etch process itself. However, relatively few studies describe a systematic investigation of the effects of insulator (e.g., hardmask) charging on ion scattering and feature profile evolution even though it is known that such charging can perturb ion trajectories and therefore affect ion scattering behavior.@footnote 2@ Using numerical simulations of electron and ion dynamics within trench structures in order to self-consistently calculate the local charging potential on insulating surfaces, combined with realistic ion scattering distributions from feature sidewalls,@footnote 3@ we show that charging of insulating materials during the etching of both semiconductors and insulators can have a large impact on the ion flux distribution along the feature bottom. Parameters varied in the simulation include mask angle, ion angular and energy distribution function, electron temperature, and trench aspect ratio. In general, under conditions of relatively low ion energy, narrow ion angular distribution function and near-vertical mask sidewalls, ion trajectories can be significantly perturbed by insulator charging, resulting in different ion flux distributions on the feature bottom. The coupling between the perturbation of ion trajectories incident upon feature sidewalls and the subsequent scattering characteristics of these ions is especially important. These results show that under certain combinations of independent variables, neglecting ion trajectory perturbation due to charging can lead to qualitative as well as quantitative errors in the prediction of local etch rates. @FootnoteText@ @footnote 1@ T.J. Dalton et al., J. Electrochem. Soc., 140(8), Pp. 2395 (1993); @footnote 2@ M. Schaepkens and G.S. Oehrlein, Appl. Phys. Lett., 72(11), pp.1293 (1998); @footnote 3@ C.F. Abrams and D.B. Graves, submitted to J. Vac. Sci. Technol. A (1998)