Sputter yields Y and sticking coefficients S are essential inputs for feature profile evolution studies. Molecular dynamics simulations are used to compute sputter yields and sticking coefficients for Cu+ ions impinging on a Cu surface at various incident energies 15<Ei<175 eV, and incident angles 0<θi<85°. Threshold energies for sputtering Eth are also predicted and shown to vary with θi. We show that for energies below what is experimentally considered as threshold for physical sputtering (Eth(expt)∼60eV) a yield between 0.01 and 0.1 Cu/ion is observed for some off-normal angles of incidence [C. Steinbrüchel, Appl. Phys. Lett. 55, 1960 (1989)]. We show that Y∝Ei - Eth below Eth(expt) when Y is a maximum with respect to θi (at θi=45°). We find that Y∝E1/2i - E1/2th at other angles of incidence. We show that S is sensitive to Ei and θi in this regime. In particular, when θi=85°, we see that 1nS∼1/Ei for Ei≥20eV. We discuss some assumptions commonly used in profile simulation studies which may now be relaxed, with an eye toward improving the predictive power of those simulations.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)