Potassium Permanganate as Oxidizer in Alkaline Slurry for Chemical Mechanical Planarization of Nitrogen-doped Polycrystalline Ge2Sb2Te5 Film

Abstract

For phase-change memory beyond the 30 nm design rule, chemical mechanical planarization (CMP) performing at a high polishing rate, reasonable selectivity, and no corrosion-induced pits is essential for planarizing nitrogen-doped polycrystalline Ge2Sb2Te5 (GST) deposited on the confined memory cell structure. We develop a new alkaline slurry added with KMnO4 used as an oxidizer. The alkaline slurry added with 0.3 wt % KMnO4 has a polycrystalline GST film polishing rate of 5200 angstrom/min, a polishing rate selectivity between polycrystalline GST and SiO2 film of 100:1, and no corrosion-induced pit. In addition, polycrystalline GST film CMP using the alkaline slurry added with KMnO4 is observed to follow a cyclic reaction polishing mechanism.