Numerical Simulation of Cryogenic Etching: Model with Delayed Desorption

A numerical model of the evolution of the trench profile during cryogenic etching in SF6/O2 plasma based on the cellular representation of the surface state, the Monte Carlo method for calculating particle fluxes, and the scheme of delayed desorption of reaction products is proposed. This description combines the advantages of the cell method (the ability to describe phenomena of a stochastic nature) and the string method (parameterization of the model in terms of physically observable quantities). The consistency of the model for etching silicon and silicon oxide in a fluorine-containing plasma, as well as etching in a SF6/O2 mixture at different temperatures is demonstrated. Spontaneous etching of silicon under the action of fluorine radicals, ion-stimulated etching, surface passivation in plasma containing oxygen radicals are simulated. A model that describes the temperature dependence of the etching character is proposed.