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In this paper, a detailed analysis is presented to characterize the performance of colloidal silica abrasives based slurry with different abrasive sizes on CMP of hexagonal 4H-SiC wafer, and indicates that the abrasive size is an important factor to determine the efficiency of CMP and the final planarization quality of wafer surface. The authors also present a detailed hypothesis to describe the material removal mechanism of 4H-SiC by colloidal silica abrasives during CMP process, and design two groups of experiments to demonstrate the rationality of the hypothesis. Furthermore, the authors put forward some suggestions to optimize the CMP efficiency and planarization quality of 4H-SiC wafer.

The application of catalyst nanoparticles in the slurry is developed for chemical mechanical planarization (CMP) of on-axis Si-face (0001) SiC wafer, so as to obtain higher material removal rate (MRR) and defect-free ultra-smooth surface. Fe nanoparticles, as well as Pt/C nanoparticles were used as a catalyst into the slurry, and the polishing experiment results indicate that an Fe catalyst is preferable to CMP of SiC. The removal behaviors of catalyst assisted CMP were studied and the removal mechanism was discussed. The detection results of *OH hydroxyl radicals reveal that the slurries with catalysts could produce *OH radicals so as to induce the oxidation of SiC. The relationship between the removal of SiC wafer by different catalysts and polishing time was investigated. The removal characteristics with different downward pressure and platen rotation speed and relative local temperature were presented. Optical microscope, optical interferometry profiler and atomic force microscope (AFM) were applied to observe the processed surface by the proposed method. Total planarization of the atomically flat defect-free surface with atomic step-terrace structure and extremely low Ra about 0.05 nm was achieved for SiC wafer by using an Fe catalyst slurry. The results affirm that the promising method is helpful to the surface preparation of super-hard and inert materials with high efficiency and high flatness.

In acid final chemical mechanical polishing (CMP) of aluminum alloy, the addition of a small amount of nitric acid (HNO3) is proved to be the effective measure for reducing the orange peel defect due to the protective film produced by HNO3 on aluminum alloy; however, it makes point defects worse. The effect of hydrolyzed polymaleic anhydride (HPMA) on point defects is investigated. HPMA adsorbs on the surface of aluminum alloy first, and the composite film formed by both HPMA and HNO3 is proved to be efficient for controlling both the orange peel and point defects. When the aluminum alloy is polished by the acid original slurry with 0.7 wt% HNO3 and 0.1 wt% HPMA, the roughness of the aluminum alloy surface is low to 0.678 nm.