Research progress on the application of ceria nanoparticles as abrasives in dielectric layer CMP and post cleaning: Structure, morphology, doping, and mechanism

Cerium oxide is the main abrasive used in the chemical mechanical polishing (CMP) process of shallow trench isolation (STI) in integrated circuit manufacturing. It is widely believed that the trivalent cerium ions (Ce3+) on the surface of cerium oxide particles can form Ce-O-Si bonds with silicon dioxide dielectric. Therefore, the application of cerium oxide in the medium CMP process has been widely studied. The particle size and morphology of cerium oxide particles, the concentration of Ce3+ and surface modification will all affect the performance of SiO2 dielectric CMP. In addition, due to the presence of the barrier layer of silicon nitride, the selectivity of the removal rates of silicon dioxide and silicon nitride is also an important factor to be considered in the CMP process. The current research on cerium oxide abrasives mainly focuses on the modification and doping of abrasive particles, as well as the control of particle size. In addition, the presence of Ce-O-Si bonds leads to the adsorption of cerium oxide particles on the surface of the medium after polishing, and the problem of particle adsorption is particularly prominent when using small particle size cerium oxide to reduce defects. Researchers have also done a lot of work to achieve better surface quality. How to achieve high removal rate, high selectivity and low surface defects after CMP is currently a research hotspot. This work mainly reviews the polishing mechanism of cerium oxide, the factors affecting the CMP rate and the improvement methods. In the aspect of CMP cleaning, the introduction of additives, water cleaning, chemical cleaning and other cleaning methods are summarized. On this basis, some suggestions were proposed to provide valuable references for the STI CMP and post cleaning based on cerium oxide abrasive.