AVS 47th International Symposium
    Plasma Science and Technology Tuesday Sessions
       Session PS-TuP

Paper PS-TuP11
Molecular Dynamics Simulation of Oxide Etching by Energetic Halogens

Tuesday, October 3, 2000, 5:30 pm, Room Exhibit Hall C & D

Session: Poster Session
Presenter: H. Ohta, Kyoto University, Japan
Authors: H. Ohta, Kyoto University, Japan
S. Hamaguchi, Kyoto University, Japan
Correspondent: Click to Email
We have performed molecular dynamics (MD) simulations of silicon dioxide (SiO@sub 2@) etching by energetic halogen (chlorine or fluorine) atoms (or ions) in the energy range of 50-150 eV. To classically simulate such systems, we have constructed Tersoff and Stillinger-Weber type inter-atomic potentials for systems containing Si, O, and Cl (or F) by nonlinearly fitting the inter-atomic potential functions to potential energy data obtained from ab-initio quantum mechanical calculations. Although it is experimentally known that etching rates of oxide by halogen ions are relatively low and it is generally considered that the etching mechanism is essentially physical sputtering, the goal of this study is to clarify details of oxide etching by halogen ions. Our preliminary simulation results based on the newly constructed inter-atomic potentials seem to indicate that, in addition to ordinary physical sputtering, chemical etching is also taking place in oxide etching by halogens. As oxygen atoms with two atomic bonds are more likely to be removed by physical sputtering than silicon atoms with four atomic bonds, oxygen atoms are first removed from the oxide surface by physical sputtering. The remaining excessive silicon atoms are then removed efficiently by the combination of physical and chemical sputtering by halogen ions, as in the case of silicon etching by energetic halogen ions, generating SiCl@sub x@ (SiF@sub x@) compounds as etching products. We have also observed that there are considerable differences in etching mechanisms between chlorine and fluorine ions due to their difference in atomic size. In the meeting, we shall present numerically obtained macroscopic etching properties such as etching rates as well as details of the microscopic etching mechanism and compare the simulation data with experimental observations.