Review on chemical mechanical polishing for atomic surfaces using advanced rare earth abrasives

During the past decades, high-performance devices and setups have been widely used in the fields of precision optics, semiconductors, microelectronics, biomedicine, optoelectronics and aerospace. It is a challenge to achieve ultralow surface roughness free of damages. Due to the unique physicochemical properties of rare earths, ceria has garnered great progresses for atomic surfaces induced by chemical mechanical polishing. Compared with conventional mechanical removal by alumina and silica, rare earth abrasives achieve selective material removal on surface via their special chemical activity, without introducing microscopic scratches and defects. Nevertheless, polishing performance of rare earth abrasives depends on series of factors, e.g. size of abrasive particles, microscale topological structure, configuration of chemical slurry, auxiliary energy fields etc. As a result, it is significant to conduct a comprehensive review to understand state-of-the-art polishing technologies. This review summarizes the effect of polishing slurries composed of different rare earth abrasives on polishing performance under different conditions. Additionally, various energy-assisted polishing strategies are discussed using diverse kinds of rare earth abrasives for distinct polishing forms. Finally, future directions of polishing on rare earth abrasives are addressed.