Quantitative control of plasma and surface reactions for dielectric film etching

Abstract

Abstract This paper reviews reaction control in the dry etching of insulating films. High ion fluxes are required for high-speed SiO2 processing. However, because atomic F generation due to excessive fluorocarbon gas dissociation causes reduced selectivity, the number of electron collisions should be reduced by using short residence times. The C–F-based polymer thickness formed during processing varies based on the oxygen content of the material to be etched. To achieve high etch selectivity, the incident flux balance must be adjusted quantitatively to ensure that the polymer becomes thinner during etching and thicker as the underlying material is exposed. Even under high selectivity conditions, incident ions cause damage at the moment the underlying material is exposed. To suppress this damage, the ion penetration depth, which depends on both ion energy distribution and ion composition, must be reduced. Recently, atomic layer etching combined with C–F polymer deposition and removal using Ar ion irradiation has been studied. To improve the accuracy of such cyclic etching processes, it is important to understand and control the transient states of both plasma and surface reactions quantitatively.