Monolayer films of diblock copolymer microdomains for nanolithographic applications

Abstract

Several techniques have been investigated for creating large-area thin films of diblock copolymers, with well-ordered two-dimensional periodic microstructure on the scale of a few tens of nanometres. Such structures might potentially be used as templates for lithography, at a length scale not easily accessed by electron-beam methods. Using a copolymer with a spherical microdomain structure, we find that it is quite easy to obtain large-area films consisting of a monolayer of spherical domains, arranged on a hexagonal lattice with a lattice constant of 33 nm. Copolymers with cylindrical microstructure typically orient parallel to the substrate and free surface, it has been found that the perpendicular orientation is metastable: if a well- or poorly-ordered film is initially prepared with the cylinders perpendicularto the surface, annealing results in a well-ordered film with the same orientation, with a lattice constant of 27 nm for the polymer used in this study. For both cylinders and spheres, grains measuring typically 30×30 lattice constants are readily obtained.