Thermal Adsorption-Enhanced Atomic Layer Etching of Si3N4

Atomic layer etching (ALE) is an alternative method for nanopatterning in which atomic layers of material are removed by sequential self-limiting surface reactions. In this study, the authors report a new cyclic process for atomic layer etching of Si3N4 films achieved by alternating exposure steps of CH3F gas adsorption and Arthorn bombardment. Self-limiting etching characteristics of the ALE process are demonstrated as a function of both CH3F etchant flow rate and CH3F exposure time. From comparative studies on the amount of Si3N4 etched using the ALE mode versus pure Arthorn ion sputtering, it is found that the ALE process operates with an ALE synergy factor of similar to 67% and also removes Si3N4 with better uniformity due to cooperative interactions between the self-limited CH3F chemisorption and the Arthorn ion sputtering. Based on both the chemical bonding changes following the CH3F etchant exposure and reaction product analyses during the Arthorn plasma step, possible etch reaction steps for the ALE Si3N4 process are proposed. Published by the AVS.This work was supported by the Samsung Electronics Project (D.S., S.O., J.W., S.L., and H.L.) and by the Department of Energy under Award No. DE-SC0004782 (W.H.K. and S.F.B.)