Mechanism of chemical mechanical polishing process for oxide-filled shallow trench isolation applications

Chemical and mechanical actions of the slurry on pilot wafers were studied in order to design a high oxide:nitride selectivity slurry for STI applications. Experimental results indicate that increased chemical action of a slurry increases the oxide removal rate while decreasing the nitride removal rate resulting in a high oxide:nitride selectivity. For a CMP process with a small process time window, high chemical and moderate mechanical action in a slurry are required. However, chemical effects play a dominant role in achieving high oxide:nitride selectivity. Results presented in this paper reveal that a suitable slurry for STI applications can be designed by balancing the chemical and mechanical actions.