Directed Self-Assembly of Polystyrene-(Polymethyl acrylate)2 Miktoarm Star Copolymers on 193 nm Immersion Lithography-Defined Chemical Patterns via Thermal Annealing

Directed self-assembly (DSA) of block copolymers in combination with 193 nm immersion lithography (193i) is one of the potential solutions for sub-10 nm patterning. Here we report the synthesis and DSA of a high-χ miktoarm star block copolymer, polystyrene-(poly(methyl acrylate)2 (PS–PMA2), for sub-10 nm nanolithography. Compared with diblock PS-b-PMA, PS–PMA2 has a higher effective χ value (0.095@150 °C) and a smaller period with the same molecular weights. The smallest achievable period (L0) was 12.8 nm for PS–PMA2, while a perpendicular orientation of lamellar domains was obtained in PS–PMA2 films with L0 down to 14.1 nm. DSA of PS–PMA2 with 5× density multiplication was successfully achieved on chemical patterns with the pattern period (LS) of 80–90 nm defined by 193i with a feature size down to 8 nm. In addition, DSA of PS-b-PMA was also demonstrated on 193i-defined patterns with a feature size of 9 nm.