Numerical Model of Plasma-Chemical Etching of Silicon in $CF_4/H_2$ Plasma

Abstract

The 2D mathematical model of plasma-chemical etching process, where the gas flow of the mixture was described by the equations of multicomponent physical-chemical hydrodynamics, was presented. The silicon etching in $CF_4/H_2$ gas mixture was studied. The chemical kinetic model contained 28 gas-phase reactions of dissociation and recombination processes and 6 heterogeneous reactions on the wafer, which included the products - F, $F_2$, $CF_2$, $CF_3$, $CF_4$, $C_2F_6$, H, $H_2$, HF, $CHF_3$, $CH_2F_2$. The concentrations of chemical components were calculated from the system of conservation equations included the mentioned gas-phase reactions. The governing equations were numerically solved by iterative finite difference splitting-up method. It is shown that the $CF_4/H_2$ system is characterized by lower fluorine concentrations and higher $CF_2$, $CF_3$ coverage of silicon surface compared to the $CF_4/O_2$ system.