On Relationships between Plasma Chemistry and Surface Reaction Kinetics Providing the Etching of Silicon in CF₄, CHF₃, and C₄F₈ Gases Mixed with Oxygen

Abstract

In this work, we discuss the effects of component ratios on plasma characteristics, chemistry of active species, and silicon etching kinetics in CF4 + O2, CHF3 + O2, and C4F8 + O2 gas mixtures. It was shown that the addition of O2 changes electrons- and ions-related plasma parameters rapidly suppresses densities of CFx radicals and influences F atoms kinetics through their formation rate and/or loss frequency. The dominant Si etching mechanism in all three cases is the chemical interaction with F atoms featured by the nonconstant reaction probability. The latter reflects both the remaining amount of fluorocarbon polymer and oxidation of silicon surface.

Keywords

• fluorocarbon gases
• active species
• ionization
• dissociation
• etching