Effect of Ar addition to an O2 plasma in an inductively coupled, traveling wave driven, large area plasma source: O2/Ar mixture plasma modeling and photoresist etching

Abstract

We report on the effect of Ar addition to an ${\mathrm{O}}_{\mathrm{2}}$ plasma on photoresist etching in an inductively coupled, traveling wave driven, large area plasma source (LAPS). We also develop a simplified spatially varying ${\mathrm{O}}_{\mathrm{2}}\mathrm{/Ar}$ mixture discharge model corresponding to the LAPS in a two-dimensional geometry in order to account for the effect of Ar addition. A photoresist etch kinetics model and spatially varying ${\mathrm{O}}_{\mathrm{2}}\mathrm{/Ar}$ mixture discharge model are used to explain the experimental data. We find that the addition of 50% Ar increases the plasma density and etch rate approximately by a factor of 2. From the simulation we find that argon metastables (Ar^*) play an important role in the mixture plasma. The simulation predicts an enhancement in O-atom density due to Ar addition, even in the presence of dilution of the feed gas. The experimental data and predicted etch rates from the simulation are generally in good agreement, indicating that the increase in the etch rate with Ar addition is due to both the increase in the plasma density and the enhancement in O-atom density attributable to the dissociation of ${\mathrm{O}}_{\mathrm{2}}$ by Ar^*.