Molecular-Dynamics Simulations of Low-Energy (25-200 eV) Argon Ion Interactions with Silicon Surfaces: Sputter Yields and Product Formation Pathways

N. A. Kubota, D. J. Economou, S. J. Plimpton, J of Appl Phys, 83, 4055-4063 (1998).

The etch yield and subsurface damage are important issues in low energy (< 200 eV) ion interactions with surfaces. In particular, atomic layer etching requires etching of electronic materials with monolayer precision and minimal interlayer atomic mixing. In this study, the molecular dynamics technique is used to simulate the impact of argon ions on chlorine-free and chlorine- passivated silicon surfaces, under conditions relevant to atomic layer etching. Thousands of individual ion impact simulations are performed on a massively parallel supercomputer. The silicon sputter yield is obtained for Ar ion energies ranging from 25 to 200 eV. Where possible, simulation results are compared to available experimental data. Volatile product formation during ion bombardment of ordered surfaces tends to follow distinct local trajectories. For example, the formation of products due to 120 eV Ar ions impacting onto Si (001)(2x1) at normal incidence has been found to occur mainly by a mechanism in which the Ar ion impacts directly in-between a surface silicon dimer pair. The energetic recoiled silicon atoms undercut nearby silicon atoms resulting in product formation. Several other product formation pathways have also been observed.

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