Statistical insights into the reaction of fluorine atoms with silicon

Abstract

The dependences of silicon etching rate on the concentration of F atoms are investigated theoretically. The nonlinear regression analysis of the experimental data indicates that the reaction of F atoms with silicon is 2nd overall order reaction. The relationship between overall reaction order and kinetic reaction order is established using the etching rate equation. It is found that kinetic reaction order monotonically decreases with the increase in concentration of F atoms due to the increased surface coverage. Surface passivation by the reaction products is not observed under the investigated experimental conditions. Scanning tunnelling microscopy (STM) is widely used to analyse chemical reactions taking place on the silicon surface. STM enabled to measure the etching rate dependences on the initial concentration of SiCl, SiBr, and SiI radicals 1,2. During the experiments, silicon substrates were dosed with molecular halogens at room temperature in order to obtain the desired initial concentration. Subsequently, silicon substrates were heated because chemical reactions between the chemisorbed radicals occur only at elevated temperatures. STM provided useful information about the reaction and desorption pathways 3 and confirmed that silicon dihalides are the final reaction products. The same experimental procedure is used to investigate chemical reaction between SiF radicals on the silicon surface. The etching rate is measured only at low initial concentration of SiF radicals because fluorine atoms due to small atomic radius penetrate into the silicon lattice 4,5. The experimental measurements 6 shown that at temperature 825 K planar removal of silicon atoms occurs together with multilayer pitting, which result in the increased surface roughness. Steady-state reaction of F atoms with silicon is investigated using large array of diagnostic techniques 7. The most common observations are following: (a) SiF 4 molecules detected by mass spectrometry of exhaust species 8 ; (b) SiF x (x ≤ 3) radicals found on the etched Si surface using X-ray photoemission spectroscopy 9 ; (c) SiF 2 molecules detected by chemiluminescence 10 and laser-induced fluorescence spectroscopy 11 ; (d) SiF 2 molecules polymerize on the surface 12. (e) SiF radicals passivate the Si surface 13 ;

Etching characteristics of hydrogenated amorphous carbon with different sp2/sp3 hybridization ratios in CF4/O2 plasmas

“…[ 1 ] R spontaneous is the etch rate obtained during spontaneous chemical removal, which is determined by the surface reaction between carbon atoms and O radicals. A spontaneous etch rate model was adopted [ 29,30 ] and the following reaction was considered for O radical absorption on the surface of a‐C:H films: where . The reaction rate can be estimated with the following spontaneous etch rate model.…”

First-Principles Dynamics of Fluorine Adsorption on Clean and Monohydrogenated Si{001}

“…For example, treatment with hydrofluoric acid (HF in aqueous solution) is used to remove layers of silicon oxide (SiO 2 ), leaving behind a hydrogen-passivated silicon surface . On the other hand, treatment with atomic fluorine (in either plasma or gaseous state) can abstract hydrogen from a passivated surface and even etch into the silicon substrate itself via a process that liberates SiF x ( x = 2–4) species into the gas phase. − Similar processes occur too on the surfaces of silicon compounds, such as SiO 2 , Si 3 N 4 , and SiC, , and much insightful discussion of the wider field may be found in recent review articles by Kanarik et al and by Rahman and Runyon …”