Defect removal by solvent vapor annealing in thin films of lamellar diblock copolymers

Solvent vapor annealing (SVA) is known to be a simple, low-cost and highly efficient technique to produce defect-free diblock copolymer (BCP) thin films. Not only can the solvent dilute the BCP segmental interactions, but also it can vary the characteristic spacing of the BCP microstructures. We systematically investigate the effect of adding solvent into lamellar BCP thin films and its evaporation rate on the BCP defect removal. We find that the increase of the lamellar spacing as is induced by solvent removal facilitates more efficient removal of defects. The stability of a particular defect in a lamellar BCP thin film is given in terms of the swelling ratio and the solvent evaporation rate. Our results highlight the mechanisms of SVA in obtaining defect-free BCP thin films, as is desired in nanolithography and other industrial applications.