PHENOMENOLOGICAL MODELING OF ION-ENHANCED SURFACE KINETICS IN FLUORINE-BASED PLASMA-ETCHING

A multiple beam apparatus has been constructed to facilitate the study of ion-enhanced fluorine chemistry on undoped polysilicon and silicon dioxide surfaces by allowing the fluxes of fluorine (F) atoms and arg on (Ar+) ions to be independently varied over several orders of magnit ude. The chemical nature of the etching surfaces has been investigated following the vacuum transfer of the sample dies to an adjoining x-ra y photoelectron spectroscopy facility. The etching ''enhancement'' eff ect of normally incident Ar+ ions has been quantified over a wide rang e of ion energy through the use of Kaufman and electron cyclotron reso nance-type ion sources. The increase in per ion etching yield of fluor ine saturated silicon and silicon dioxide surfaces with increasing ion energy (E(ion)) was found to scale as (E(ion)1/2 - E(th)1/2), where E (th) is the etching threshold energy for the process. Simple near-surf ace site occupation models have been proposed for the quantification o f the ion-enhanced etching kinetics in these systems. Acceptable agree ment has been found in comparison of these Ar+/F etching model predict ions with similar Ar+/XeF2 studies reported in the literature, as well as with etching rate measurements made in F-based plasmas of gases su ch as SF6 and NF3.