Influence of High Selectivity Slurry in Shallow Trench Isolation CMP on Junction Leakage Characteristics

摘要

Shallow trench isolation chemical mechanical polishing (CMP) using a conventional slurry has a number of problems such as variation of pattern density across the die, nonuniform polishing rate within wafer, and insufficient selectivity of oxide to nitride. These effects cause nonuniform thickness variation after polishing, which in turn degrade the junction leakage current characteristics. To solve these problems, high selectivity slurry (HSS) has been introduced, which is less dependent on the variation of pattern density because of high selectivity of oxide to nitride. By using HSS instead of the conventional slurry, the within die nonuniformity and the within wafer nonuniformity could be improved. Thereby, the HSS process led to better junction leakage current characteristics. Moreover, the HSS process could have a wider process window and eliminate the need tar a reverse etchback process, which is essential when the conventional slurry is used.