Fluorocarbon (C4F8) assisted plasma-enhanced atomic layer etching of SiO2 with high repeatability of cycles in industrial ICP reactor. II. Simulation

A numerical etching model was developed based on kinetic balance equations for surface site coverages on the fluorocarbon polymer surface and at the polymer-processed material interface. This 0D etching model is coupled with a 2D fluid simulation of an inductively coupled plasma reactor. To test the developed cyclic atomic layer etching (ALE) model, simulations were conducted under experimentally selected SiO2 ALE recipes. These recipes include Ar/C4F8 plasma for deposition step, Ar plasma for activation step, and Ar/O2 plasma for cleaning step with a gas pressure of 3 Pa at each step. The developed ALE model allows for an adequate description of the general principles of cyclic ALE operation for two recipes with different plasma conditions at all stages of the ALE cycle. The calculated etch per cycle value is in good agreement with experimental data. The crucial reactions in SiO2 ALE cycles with the additional cleaning step are discussed.