A theoretical model is developed for plasma etching of silicon with SF6. The three-dimensional model developed includes diffusion and convection of molecular fragments in a duct geometry. Active species generation is described by electron impact dissociation reactions which are functions of the electric field and gas density. Dissociative chemisorption is also considered as a source of fluorine atom generation. Fundamental plasma parameters such as electron density and electric field are estimated from impedance measurements in a designed experiment. Good agreement is obtained between model predictions of silicon etching rate and experimental results obtained under various ranges of flow rate, pressure, power, and electrode gap. © 1990, The Electrochemical Society, Inc. All rights reserved.