Simulation of the polymerization process on a silicon surface under plasma-chemical etching in CF₄/H₂

Abstract

The hydrodynamic approach is used to simulate silicon passivation by unsaturated CF _x radicals under plasma-chemical etching in CF₄/H₂. The plasma-chemical kinetics model contains 28 determinative gas-phase reactions with the participation of F, F₂, CF₂, CF₃, CF₄, C₂F₆, H, H₂, HF, CHF₃, and CH₂F₂. The extended kinetics of heterogeneous reactions on a silicon surface comprises the competing processes of the adsorption of CF₂ and CF₃ radicals. It is demonstrated that a major portion of atomic fluorine is actively involved in the formation of hydrogen fluoride, reducing the silicon etching rate to a significant extent. It is established that CF₂ adsorption is predominant among the competing processes of the passivation of a silicon surface and that the CF₂ layer covers the entire silicon surface at a 40% H₂ content, thereby causing its etching to cease.