The real time changes occurring within films of cylinder-forming poly(α-methylstyrene-block-4-hydroxystyrene) (PαMS-b-PHOST) were monitored as they were swollen in tetrahydrofuran (THF) and acetone solvent vapors. In situ information was obtained by combining grazing incidence small angle X-ray scattering (GISAXS) with film thickness monitoring of the solvent vapor swollen films. We show that for self assembly to occur, the polymer thin film must surpass a swollen thickness ratio of 212% of its original thickness when swollen in THF vapors and a ratio of 268% for acetone vapor annealing. As the polymer becomes plasticized by solvent vapor uptake, the polymer chains must become sufficiently mobile to self assemble, or reorganize, at room temperature. Using vapors of a solvent selective to one of the blocks, in our case PHOSTselective acetone, an order-order transition occured driven by the shift in volume fraction. The BCC spherical phase assumed in the highly swollen state can be quenched by rapid drying. Upon treatment with vapor of a non-selective solvent, THF, the film maintained the cylindrical morphology suggested by its dry-state volume fraction. In situ studies indicate that self-assembly occurs spontaneously upon attaining the threshold swelling ratios.

Poly(alpha-methylstyrene)-block-poly(4-hydroxystyrene) acts as both a lithographic deep UV photoresist and a self-assembling material, making it ideal for patterning simultaneously by both top-down and bottom-up fabrication methods. Solvent vapor annealing improves the quality of the self-assembled patterns in this material without compromising its ability to function as a photoresist. The choice of solvent used for annealing allows for control of the self-assembled pattern morphology. Annealing in a nonselective solvent (tetrahydrofuran) results in parallel orientation of cylindrical domains, while a selective solvent (acetone) leads to formation of a trapped spherical morphology. Finally, we have self-assembled both cylindrical and spherical phases within lithographically patterned features, demonstrating the ability to precisely control ordering. Observing the time evolution of switching from cylindrical to spherical morphology within these features provides clues to the mechanism of ordering by selective solvent.

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Strongly segregating block copolymers (BCPs) are attractive as a means of forming 10 nm scale lithographic features. Here, we report directed self-assembly of polyhedral oligomeric silsesquioxane containing block copolymers (PMMA-b-PMAPOSS) with feature density multiplication to form long-range ordered arrays of dots having areal densities of ∼4 tera dots per square inch via controlled solvent annealing. The degree of swelling of PMMA-b-PMAPOSS thin film during the carbon disulfide solvent annealing was optimized to give the polymer chain mobility to form the desired microdomain structure. Because the annealing solvent is not fully neutral to the components of the BCP, the types of microstructures formed depend strongly on the degree of swelling. We demonstrated that the directed self-assembly with 4× density multiplication of the chemically patterned template can be performed successfully under the optimized condition of solvent annealing and hexagonally packed dots array with 12 nm lattice spacing was produced. We also showed that the microdomain structures formed by solvent-annealing the BCP on the chemically patterned template could tolerate several percent of mismatch between the lattice spacing of the BCP and that of the template. In this study the morphology was limited to hexagonally packed dots. However, the results strongly support the potential application of the technique to form 10 nm scale features of other desired geometries.