Control of PS-b-PMMA directed self-assembly registration by laser induced millisecond thermal annealing

Directed self-assembly of PS-b-PMMA during laser spike annealing at peak temperatures of 300-800°C for dwells of 1- 10 ms has been explored. The enhanced mobility of polymer chains at these temperatures improves registration compared to conventional thermal anneals. PS-b-PMMA films (forming 15 nm line/space standing lamellae) were cast on chemically patterned substrates with a copolymer neutral layer and annealed by laser and hot-plate (2 minutes 250°C). Annealing by hot plate or multiple laser scans resulted in well-aligned features over micron length scales. By laser annealing multiple times, defectivity can be reduced by ~60%. However, laser annealing for only 10 ms before performing a hot plate anneal reduced defectivity by ~80%. Additionally, defects are more often localized as dislocation pairs rather than regions perpendicular to the underlying directing pattern resulting in far greater total alignment.