Reduction of Wafer Backside Aluminum Contamination for Harp STI Process

High Aspect Ratio Process (HARP®) is widely used for shallow trench isolation (STI) gap-filling from 55nm to 28nm node. It is a high temperature process with wafer chucking function. High temperature could enhance fluorine's attack on AlN heater, and chucking force would lead to backside particles generation. This paper discussed the generation mechanism of HARP STI wafer backside aluminum contamination, and proposed two reduction methods: backside scrubbing and season film thickness optimization.