STUDY ON CERIA-BASED SLURRY FOR STI PLANARIZATION

摘要

Chemical-mechanical polishing (CMP) is widely applied in the Shallow trench isolation (STI) process. In this process, gap fill oxide needs to be removed to completely expose silicon nitride across all active regions with minimal nitride loss and trench dishing. However, there is a small process window due to pattern dependency, trench oxide dishing and low oxide to nitride selectivity. In this paper, a new type of ceria-based slurry has been reported for STI planarization in a single step. The polishing mechanism and the behavior of the surfactant in the new Ceria CMP process is also discussed. A key advantage of the new slurry is having high selectivity for topography and for oxide to nitride, and self-stopping characteristics after planarization. These unique features provide a large over polish window for STI planarization.