Impact of wafer transfer process on STI CMP scratches

Abstract

Shallow trench isolation chemical mechanical polishing (STICMP) technology has been widely applied in the fabrication of ultra large scale integrated (ULSI). In STI-CMP, the defect, topography control, thickness uniformity and so on are all so critical, especially, scratch defect is the major problem. Pad, disk, agglomerated slurry particles and foreign particles are the main sources of the tiny scratch. In this article, impact of transfer process on scratch during STI-CMP, such as pre CMP, bulk polish post treatment, and pre selective polish was studied. Variable down force, DIW rinse time, slurry flow rate, slurry buff treatment were verified respectively. It was found that the pre CMP slurry buff can reduce the scratch by 55%, and bulk polish post step with optimized buff condition also can reduce scratch by 30%. Besides, the backside clean also can reduce the scratch significantly.