Effect of O2 admixture: Competition of electron density and etching rate in CF4/O2 plasma-etching process

The effect of O₂ admixture concentration on silicon etching process in tetrafluoromethane - oxygen mixture is investigated on the base of numerical modeling. The calculations were carried out with using of the mathematical model of nonisothermal reactor that takes into account a peculiarities of plasma kinetics in RF-discharge. The gas flow mixture was described by the equations of multicomponent hydrodynamics including convective-diffusion transfer and production of all individual components of mixture. In the paper the numerical evaluations of electron density influence on the main characteristics of silicon etching are presented. It was shown that the fall of average density of energetic electrons in the reactor due to oxygen addition can decrease the etching rate in a range up to 30% but in any case the etching rate in mixture stays essentially more high that one in pure tetrafluoromethane.