Chemical kinetics mechanism for chemical mechanical polishing diamond and its related hard-inert materials

Abstract

Hard-inert materials such as diamond, silicon carbide, gallium nitride, and sapphire are difficult to obtain from the smooth and damage-free surfaces efficiently required by semiconductor field. Therefore, this study proposed a chemical kinetics model to evaluate the material removal rate of diamond in chemical mechanical polishing process and to investigate the material removal mechanism by examining the surface information with optical microscopy, surface profilometry, and atomic force microscopy as well as X-ray photoelectron spectroscopy. The theoretical and experimental results show that chemical and mechanical synergic effect may promote the diamond oxidation reaction in chemical kinetics. The material removal rate is acceptable when the mechanical activation coefficient is smaller than 0.48. The 2.5 μm B4C abrasives, the polishing temperature of 50 °C, and the polishing pressure of 266.7 MPa are optimal parameters for diamond polishing with potassium ferrate slurry. It provides the highest material removal rate of 0.055 mg/h, the best surface finish (about Ra 0.5 nm) and surface quality (no surface scratches or pits). It then discusses how mechanical stress may promote the chemical oxidation of oxidant and diamond by forming “C-O,” “C=O,” and “O=C-OH” on diamond surface. The study concludes that chemical kinetics mechanism is effective for the investigation of the synergic effect in chemical mechanical polishing hard-inert materials.