Kinetics of Reactive Ion Etching of Si, SiO 2 , and Si 3 N 4 in C 4 F 8 + O 2 + Ar Plasma: Effect of the C 4 F 8 /O 2 Mixing Ratio

The kinetics of reactive ion etching of an Si, SiO2, and Si3N4 in the C4F8 + O2 + Ar mixture with a varied C4F8/O2 mixing ratio under the conditions of an rf inductive discharge (13.56 MHz) is investigated. Using the methods of plasma diagnostics and simulation, the data on the effect of the initial mixture’s composition on (a) the parameters of the electronic and ionic components of plasma and (b) the concentrations and densities of the fluxes of neutral species are obtained. It is established that nonmonotonic (with the maximum at ∼15% O2) changes in the etching rates for all three materials with an increasing O2 fraction in the mixture are provided by an increase in the atomic fluorine flux density with a simultaneous decrease in the effective probability of a heterogeneous chemical reaction with them. It is demonstrated that the behavior of the latter parameter does not reflect the changes in the kinetics of polymerization on the treated surface; however, this can be due to the heterogeneous processes involving oxygen atoms.