Amorphous carbon is replacing conventional hard masks in semiconductor fabrication due to its exceptional etching selectivity towards silicate. After amorphous carbon deposition, a chemical mechanical polishing (CMP) is essential for planarizing the surface locally and globally. This study investigated the chemical oxidation and mechanical abrasion of amorphous carbon based on several factors, including pH, polishing pressure, and oxidants. Oxidants promoted the formation of C-O, C=O, and –COOH. Mechanical abrasion accelerates carbon surface oxidation and the removal of oxidized film. In addition, slurries containing three potent oxidants were evaluated: ferric nitrate with hydrogen peroxide, potassium permanganate, and cerium ammonium nitrate (CAN). These oxidants accelerated C–C breakage and increased the removal rate. In comparison, the slurry containing 1 wt% CAN exhibited a maximum removal rate of 480 Å/min and an atomic-scale roughness of 0.056 nm.