Ion-surface interactions on at the radiofrequency-powered electrode in low-pressure plasmas: Ex situ spectroscopic ellipsometry and Monte Carlo simulation study
Pseudo-dielectric function measured by ex situ VASE for samples exposed to an plasma for at bias values ranging from : (a) real part ; (b) imaginary part .
Three ellipsometric models proposed to describe the modifications of : (a) a single layer film on (model 1), (b) a two-layer system with on an interfacial layer (model 2), and (c) a two layer system with a top layer (TL) on a BEMA mixed phase interfacial damage layer (DL) (model 3). The best fit to the ellipsometric data is obtained using model 3. All data refer to .
Experimental and fitted ellipsometric signals as a function of photon energy for a sample with : (a) Best fit using model 3. Deviation between experimental and fitted values for the three models are presented in (b) and (c) for the real and imaginary parts, respectively. For clarity, only data for are shown.
Evolution of the surface modifications according to model 3 extracted from ex situ VASE data: (a) TL thickness, (b) DL thickness, and (c)–(e) DL composition as a function of .
Schematic representation of (a) the ion energy distribution function of plasma at the rf-powered electrode and (b) the oxygen atom energy distribution function after dissociating molecules. (a) is modified after (Ref. 6).
Monte Carlo SRIM simulations of O ion bombardment in on Si. and the thickness is (a) 0.8, (b)3, (c) and ; and the thickness is (d) 0.8, (e) 3, (f) and .
Logarithmic plots of (a) theoretical and measured depth of modification as a function of from this work and from Williams et al. (Ref. 8), and (b) energy loss per unit depth of ions in as a function .
Schematic representation of ion distribution in Si at specific times during plasma treatment of : (a) before oxidation, (b) during surface swelling, and (c) and (d) after surface recession by sputtering. At first, surface swelling may lead to thicker DL formation, but as surface recession by sputtering overtakes swelling, a steady state DL (constant thickness and composition) is reached.
Estimation of sputtering rate, swelling, and O surface density. See text for details.
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