Design of a Novel Wet-Etch Reactor and Etch Chemistries: Simulations and Experimental Verification

Abstract

Dilute aqueous solutions of hydrofluoric acid (HF) have been used to etch or remove SiO¬¬2-based layers. Due to the various chemical equilibria established between ionic species in aqueous HF solutions, control of etchant species concentrations and thus etch selectivity is difficult. A short contact time prototype reactor for wet etching studies of silicon-based dielectric films has been designed to investigate the effects of various process parameters during the etch process . For comparison, simulations using Computational Fluid Dynamics (CFD) have been used to predict the effect of process parameters such as flow rates and HF concentrations, thermodynamic equilibria, species transport, intrinsic etch kinetics and geometric parameters of the reactor. Results from CFD and etch experiments are in good agreement. Non-aqueous solutions utilizing fluorine-containing tetrabutylammonium salts have been investigated to control desirable equilibria and tailor etch rates and selectivity.