Molecular dynamics simulations of silicon nitride atomic layer etching with Ar, Kr, and Xe ion irradiations

Molecular dynamics simulations were performed to understand the gas-surface interactions during silicon nitride (SiN) plasma-enhanced atomic layer etching (PE-ALE) processes with argon (Ar), krypton (Kr), and xenon (Xe) ion irradiations. Changes in the surface height, penetration depths of hydrofluorocarbon (HFC) species, and damaged layer thickness were examined over five PE-ALE cycles. The results showed that the PE-ALE process with Ar+ ions etched the SiN surface more efficiently than those with Kr+ or Xe+ ions under the otherwise same conditions. Slower etching in the case of Kr+ or Xe+ ion irradiation is likely caused by the accumulation of HFC species. It was also observed that the damaged layer thicknesses of the etched surfaces are nearly the same among those with Ar+, Kr+, and Xe+ ion irradiations.