PROFILE EVOLUTION DURING COLD-PLASMA BEAM ETCHING OF SILICON

Processing characteristics of cold, directional plasma beams have been studied by numerical simulation of the profile evolution of trenches etched in silicon with chlorine, where the cold plasma beams were char acterized by highly directional fluxes of neutrals as well as ions wit h their low temperatures or random thermal energies. The model include d ion and neutral transport in microstructures and ion-assisted surfac e chemistry for the chlorine-silicon system. The numerical results dem onstrate that the cold plasma beams achieve high etch anisotropy and m icroscopic uniformity: a tapered profile, inversely tapered profile, a nd reactive-ion-etching (RIE) lag, which often occur in usual plasma e tching environments, are significantly suppressed owing to preferentia l incidence of neutral reactants as well as ions onto the bottom of mi crostructural features. In addition, the increased directionality of n eutral fluxes not only offsets the RIE lag, but also further causes a weak inverse RIE lag without relying on surface inhibitors. Experiment al techniques are also discussed for generation of such cold, directio nal beams of reactive plasmas.