Surface kinetics and plasma equipment model for Si etching by fluorocarbon plasmas

Abstract

Plasma-surface interactions during plasma etching are important in that, in addition to determining the rate and quality of the etch, they can also influence the properties of the bulk plasma. To address this coupling of bulk and surface processes the surface kinetics model (SKM) was developed as a module in the two-dimensional hybrid plasma equipment model (HPEM) with the goal of combining plasma chemistry and surface chemistry in a self-consistent fashion. The SKM obtains reactive fluxes to the surface from the HPEM, and generates the surface species coverages and the returning fluxes to the plasma by implementing a user defined surface reaction mechanism. Although the SKM is basically a surface-site-balance model, extensions to those algorithms have been made to include an overlying passivation layer through which reactants and products diffuse. Etching of Si in an inductively coupled plasma sustained in Ar/C2F6 was investigated using the SKM. Results from parametric studies are used to demonstrate the sensitivity of etching rates and polymer thickness to the sticking coefficient of fluorocarbon radicals on the reactor walls, polymer erosion rates and F atom diffusion through the polymer layer.