Statistical insights into the reaction of fluorine atoms with silicon

Rimantas Knizikevičius

doi:10.1038/s41598-020-70432-0

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.

Highlights

The dependences of silicon etching rate on the concentration of F atoms are investigated theoretically
The most common observations are following: (a) SiF4 molecules detected by mass spectrometry of exhaust s pecies[8]; (b) SiFx (x ≤ 3) radicals found on the etched Si surface using X-ray photoemission spectroscopy[9]; (c) SiF2 molecules detected by c hemiluminescence[10] and laser-induced fluorescence s pectroscopy[11]; (d) SiF2 molecules polymerize on the s urface12. (e) SiF radicals passivate the Si s urface[13]; The experimental measurements are subsequently analysed using theoretical models
The reaction of fluorine atoms with silicon at constant temperature is investigated using the nonlinear regression of the experimental data

Summary

Reaction product

The experimental scientists described steady-state etching rate using the empirical equation V = ε†[F]γ , where ε† is the rate constant and γ is the kinetic reaction order. Kinetic reaction order describes how silicon etching rate depends on the concentration of F atoms. When the substrate temperature is determined accurately, the absolute error of desorption activation energy reaches maximum value ω. Otherwise, when the desorption activation energy of the reaction product is determined accurately, the absolute error of temperature reaches maximum value kT2 ω. The following differential equation includes rate expressions of the processes mentioned earlier and describes the concentration kinetics in the adsorbed layer: dc dt. The steady-state etching rate, which is equal to the desorption rate of formed SiFn species, is calculated using the following equation: Vst The overall reaction order does not depend on the partial pressure of F atoms

Results and discussion

Conclusions

Additional information