Enhanced Lateral Ordering in Cylinder Forming PS-b-PMMA Block Copolymers Exploiting the Entrapped Solvent.

The self-assembly of block copolymer (BCP) thin films produces dense and ordered nanostructures. Their exploitation as templates for nanolithography requires the capability to control the lateral order of the nanodomains. Among a multiplicity of polymers, the widely studied all-organic polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) BCP can easily form nanodomains perpendicularly oriented with respect to the substrate, since the weakly unbalanced surface interactions are effectively neutralized by grafting to the substrate an appropriate poly(styrene-random-methyl methacrylate) P(S-r-MMA) random copolymer (RCP). This benefit along with the selective etching of the PMMA component and the chemical similarity with the standard photoresist materials deserved for PS-b-PMMA the role of BCP of choice for the technological implementation in nanolithography. This work demonstrates that the synergic effect of thermal annealing with the initial solvent naturally trapped in the basic RCP + BCP system after th...