Effect of gas additives on reaction barriers in cryo etching of silicon oxide and nitride

Vertical scaling of 3D NAND devices calls for higher SiO2 and SiN etching rates and meaningful reduction of aspect ratio dependent etching. Recently, evolutionary improvements of the fluorocarbon gas process have been replaced by novel so-called cryo etching processes using HF as the main etch gas. In this paper, we report computational results for the activation Gibbs free energies ΔG‡ for the reaction of HF and various additive gases with SiO2 and SiN. The results are compared with available experimental trends. We find that the dipole moment of the additive gas is an indicator of its catalytic effect.