Study of Shallow Trench Isolation Gap Fill for 19nm NAND Flash

Polysilazane (PSZ) curing has been introduced for 19nm NAND Flash to ensure void free Shallow Trench Isolation (STI) gap fill. PSZ film was converted into oxide mainly depending on temperature and water vapor. The high temperature PSZ curing would give rise to Si dislocation and PSZ crack. However, lowering curing temperature would lead to an insufficient conversion of PSZ film and even generate voids. As a result, wet oxidation was utilized between curing 1 and curing 2 to improve conversion rate of PSZ film. The TEM images showed good gap fill performance of PSZ curing by using low temperature/wet oxidation method.