Utility of Oxy-Anions for Selective Low Pressure Polishing of Cu and Ta in Chemical Mechanical Planarization

Abstract

Slurry chemistries utilizing several simple oxy-anions are proposed to meet some of the requirements for low pressure chemical mechanical polishing of Ta barrier and Cu lines in nonalkaline dispersions. Polish rates (PRs) were measured for Cu and Ta disks using H 2 O 2 based slurries containing anions of phosphate, sulfate, chlorate, carbonate, nitrate, or persulfate. Polishing of Cu, Ta, TaN, and SiO 2 wafers using the sulfate-containing slurry demonstrated a high selectivity (∼15) of Ta:Cu PRs and could be controlled by varying the anion and/or the pH of the slurry. The processed wafers showed surface morphologies with acceptable roughness (< 1 nm) and peak-to-valley distances (< 10 nm).