Mechanisms of silicon nitride etching by electron cyclotron resonance plasmas using SF6- and NF3-based gas mixtures

The results of a study of SiNx, SiO2, and Si etching in a high-density electron cyclotron resonance plasma using mixtures containing SF6, NF3, N2, O2, and Ar are presented. Higher selectivities of SiNx etching over SiO2 (up to ∼100) were achieved with NF3, while higher selectivities over Si (up to 5–10) were obtained with SF6-based mixtures. Plasma and surface processes responsible for etching are analyzed, and mechanisms of nitride etching in NF3-based plasmas are proposed.