Optimization of SADP Process for Defect Reduction in Planar 2D NAND Flash

With 2D NAND flash technology reached 24nm and beyond, tiny defects including bridge and pattern collapse have become the major yield killer defect in AA loop. In this work, the mechanism of tiny bridge and pattern collapse defect formation and improvement solutions are studied. For tiny bridge defect, the results showed that PR residue by periphery AA photo insufficient development in self-aligned double patterning process is the major cause of tiny bridge defect. Enhanced photo rinse & puddle process, SADP core/spacer line CD inline control and core etch profile optimization are all effective solutions to reduce tiny bridge defect. For pattern collapse defect, repeating structures with high aspect ratio are vulnerable by surface tension of drying liquid between patterns. Optimized wet cleaning sequence to ensure structure in continuous wetting status showed great improvement for pattern collapse defect reduction.