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 CFx 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.