Thin films of block copolymers are extremely attractive for nanofabrication because of their ability to form uniform and periodic nanoscale structures by microphase separation. One shortcoming of this approach is that to date the design of a desired equilibrium structure requires synthesis of a block copolymer de novo within the corresponding volume ratio of the blocks. In this work, we investigated solvent vapor annealing in supported thin films of poly(2-hydroxyethyl methacrylate)-block-poly(methyl methacrylate) [PHEMA-b-PMMA] by means of grazing incidence small angle X–ray scattering (GISAXS). A spin-coated thin film of lamellar block copolymer was solvent vapor annealed to induce microphase separation and improve the long-range order of the self-assembled pattern. Annealing in a mixture of solvent vapors using a controlled volume ratio of solvents (methanol, MeOH, and tetrahydrofuran, THF), which are chosen to be preferential for each block, enabled selective formation of ordered lamellae, gyroid, hexagonal or spherical morphologies from a single block copolymer with a fixed volume fraction. The selected microstructure was then kinetically trapped in the dry film by rapid drying. To our knowledge, this paper describes the first reported case where in-situ methods are used to study the transition of block copolymer films from one initial disordered morphology to four different ordered morphologies, covering much of the theoretical diblock copolymer phase diagram.

Self-consistent field theory is used to model the self-assembly of a symmetric PMMA-block-PHEMA in the presence of two solvents, methanol and tetrahydrofuran (THF). The model predictions are compared to our experimental results of solvent-vapour annealing of thin polymer films, where the sequence of cylinder to gyroid (or micelles) to lamellar phases was found upon increasing the methanol-THF ratio and for particular extents of film swelling. The Hansen solubility parameters are used to estimate the Flory-Huggins interaction parameters (χ) needed in the theoretical model. However, because enacting the experimental range of high (χ)N values is computationally prohibitive, the use of moderate (χ)N values is compensated by employing larger values of the solvent-to-polymer size ratio (α). This approach is validated by showing that the predicted phase diagrams exhibit qualitatively similar trends whether (χ)N or α is increased. Using such an approach, the theory predicts a cylinder to gyroid to lamellar transition on increasing the THF-methanol ratio, a trend consistent with that observed in the experiments.

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The fluorine-containing block copolymers of poly(styrene-block-2,2,2-trifluoroethyl methacrylate)(PS-b-PTFEMA) and poly(4-hydroxystyrene-block-2,2,2-trifluoroethyl methacrylate) (PHOST-b-PTFEMA), which both are capable of both top-down and bottom-up lithography were developed. These block copolymers were synthesized by either anionic or ATRP living polymerization methods. Comparison is made to patternable block copolymers of poly(hydroxystyrene-block-α-methyl styrene) (PHOST-b-PAMS) and poly(hydroxyethyl methacrylate)-block-poly(methyl methacrylate) (PHEMA-b-PMMA). Thin films of the block copolymers were subjected to lithographic processing using e-beam and DUV radiation combined with vacuum processing to create integrated patterns such as dots in lines. Solvent annealing was used to create long range order.

The fluorine-containing block copolymers of poly(styrene-block-2,2,2-trifluoroethyl methacrylate) (PS-b-PTFEMA) and poly(4-hydroxystyrene-block-2,2,2-trifluoroethyl methacrylate) (PHOST-b-PTFEMA), which all are capable of both top-down and bottom-up lithography were developed. The reported block copolymers were synthesized by either anionic polymerization or atom transfer radical polymerization (ATRP). Characterization of bulk and thin films were carried out using differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS). Thin films of the resulting block copolymers were subjected to conventional lithographic processing using e-beam and deep-UV radiation to create integrated patterns such as dots in lines.