Effect of charged additive on SiO2 to poly-Si selectivity in wet ceria based CMP slurry

Abstract

CMP, a chemical mechanical planarization process, is an indispensable process for securing the depth of focus (DOF) for multiple interconnect layers and patterns in semiconductor processes. This study is to increase the selectivity of SiO2 to poly-Si in poly-Si stop CMP during NAND flash memory manufacturing process to reduce dishing and increase DOF margin. Ceria slurry was prepared by adding anionic polymer, nonionic polymer and cationic polymer respectively to polyethylene oxide (PEO) which is a nonionic surfactant in order to conduct CMP experiments. Through this CMP experiment, it was found that the selectivity was significantly increased when the anionic polymer was added, and the FTIR measurements was conducted to analyze the mechanism of the cause. The FTIR spectra analysis confirmed that PEO and anionic polymer form an interpolymer complex, which leads to an increase in the selectivity.