Selective Polishing of Amorphous Silicon Carbonitride (a-SiCN) Films Over Silicon Dioxide and Silicon Nitride Films for Hardmask Applications

Abstract

We show that several amino acids and taurine, an aminosulfonic acid, when used as additives in 1 wt% silica slurries enhance a-SiCN removal rates (RRs) in the pH range 3–9. High RRs of 120 nm min−1 and 160 nm min−1 were obtained with 0.13 M glycine + 1 wt% silica at pH 5 and with 0.13 M taurine + 1 wt% silica at pH 6, respectively, both at an applied pressure of 3 psi. These compositions suppressed silicon nitride and silicon dioxide RRs to < 2 nm min−1, making them excellent candidates for polishing a-SiCN hard mask layers during semiconductor fabrication. The role of the amino acids and taurine in polishing a-SiCN films was investigated using zeta potential measurements, attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The reactivity of the deprotonated carboxyl species of the amino acids with SiCN surface is responsible for the observed rate enhancement while the binding of the protonated amine species of the amino acids with the silicon nitride surface suppresses nitride RRs at pH 5 and higher. The higher reactivity of taurine’s sulfonic group is responsible for its higher polish rate. Oxide RR is low due to low silica particle loading of 1 wt%.