Effect of electron density in RF-discharge on etching rate in plasma-chemical reactor

The effect of O₂ additive concentration on silicon etching process in a tetrafluoromethane-oxygen mixture is investigated on the base of numerical modeling. The calculations were carried out using an advanced mathematical model of a plasma-chemical reactor. The model takes into account peculiarities of plasma kinetics in a RF-discharge. The gas flow is described by the equations of multicomponent hydrodynamics including convective-diffusion transfer and production of all mixture components. In the paper the electron density influencing the main characteristics of silicon etching is presented. It is 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 the mixture stays essentially higher than that in pure tetrafluoromethane.