Surface kinetics modeling of silicon and silicon oxide plasma etching. I. Effect of neutral and ion fluxes on etching yield of silicon oxide in fluorocarbon plasmas

Silicon oxide etching processes in C 2 F 6 and C 4 F 8 + 80 % Ar plasmas were investigated. Neutral and ion compositions in the plasma were measured using quadrupole mass spectrometry and etching yield was measured by a quartz-crystal microbalance. In C 2 F 6 plasma, the concentration of atomic fluorine in the neutral flux was 5%–25%, whereas there was less than 0.5% of atomic fluorine in C 4 F 8 + 80 % Ar plasma. A surface plot representing the etching yield as a function of neutral and ion fluxes was constructed and used to qualitatively explain the etching characteristics of silicon oxide in fluorocarbon plasmas. In C 2 F 6 chemistry, etching yield decreases slightly with increasing rf coil power. This is attributed to the decrease in both F/ion and C F x /ion, which is caused by an increase in ion flux, with a more significant effect due to a decrease in F/ion. In C 4 F 8 + 80 % Ar chemistry, however, etching yield increases with increasing rf coil power. This is attributed to the decrease in C F x , without the effect of F/ion due to the low atomic fluorine concentration. With increased operating pressure, etching yield decreases for both chemistries because as the pressure increases, ion current decreases, and C F x neutral concentration increases to have more deposition and less etching.