Solvent vapor annealing of block copolymer thin films can produce a range of morphologies different from the equilibrium bulk morphology. By systematically varying the flow rate of two different solvent vapors (toluene and n-heptane) and an inert gas, phase maps showing the morphology versus vapor pressure of the solvents were constructed for 45 kg/mol polystyrene-block-polydimethylsiloxane diblock copolymer films of different thicknesses. The final morphology was correlated with the swelling of the block copolymer and homopolymer films and the solvent vapor annealing conditions. Self-consistent field theory is used to model the effects of solvent swelling. These results provide a framework for predicting the range of morphologies available under different solvent vapor conditions, which is important in lithographic applications where precise control of morphology and critical dimensions are essential.

The registration and alignment of a monolayer of microdomains in a self-assembled block copolymer thin film can be controlled by chemical or physical templating methods. Although planar patterns are useful for nanoscale device fabrication, three-dimensional multilevel structures are required for some applications. We found that a bilayer film of a cylindrical-morphology block copolymer, templated by an array of posts functionalized with a brush attractive to the majority block, can form a rich variety of three-dimensional structures consisting of cylinder arrays with controllable angles, bends, and junctions whose geometry is controlled by the template periodicity and arrangement. This technique allows control of microdomain patterns and the ability to route and connect microdomains in specific directions.

A perpendicular orientation of high-aspect-ratio polystyrene-block-polydimethylsiloxane (PS-b-PDMS) cylindrical and lamellar PDMS microdomains was achieved by solvent annealing and then slowly drying thick PS-b-PDMS films. Perpendicularly oriented microdomains occurred throughout the film thickness, except at the air interface, where a layer of inplane microdomains formed due to the surface energy difference between PS and PDMS. In contrast, thermal annealing produced in-plane orientation throughout the film thickness. The solvent-annealed perpendicular orientation was observed for cylindrical morphology PS-b-PDMS of 16 and 45 kg/mol, where PDMS is the minority block, and lamellar PS-b-PDMS of 43 kg/ mol. To obtain fully perpendicular microdomain patterns, a nonselective high-powered 450 W CF 4 /O 2 reactive ion etching process was performed to remove the top layer of the films. Substrate patterning using electron beam lithography produced local registration of 17 nm period hexagonal cylinder patterns.

A two-stage annealing process for block copolymer films was introduced consisting of a solvent vapor exposure followed by a thermal cycle. By heating the film but not the chamber, changes in the ambient vapor pressure of the solvent were avoided. Films of block copolymers and homopolymers showed transient nonmonotonic swelling behavior immediately after solvent exposure that was dependent on how the thin film was cast before the anneal. Thermal cycling of the solvent-swelled block copolymer films during the solvent vapor anneal (SVA) caused the films to deswell in 1-10 s and produced well-ordered microdomains in templated 45.5 and 51.5 kg/mol polystyrene-block-polydimethylsiloxane films annealed in toluene and n-heptane vapors for total process times of 30 s to 5 min.

Random copolymer brushes of poly(styrene-r-methyl methacrylate) (PS-r-PMMA) have previously been used to control the wetting behavior of poly(styrene-b-methyl methacrylate) (PS-b-PMMA) block copolymer.Here we demonstrate that the use of random copolymer may be generalized to other block copolymer systems. A series of poly(styrene-r-2-vinylpyridine-r-hydroxyethyl methacrylate) (PS-r-P2VP-r-PHEMA) random copolymers was synthesized and evaluated as brush layers to control the orientation of domains in thin films of poly(styrene-b-2-vinylpyridine) (PS-b-P2VP) block copolymer. On nonpreferential brushes, thin films of PS-b-P2VP had a mixed orientation of domains consisting of a perpendicular orientation of lamellar domains near the copolymer-substrate interface and a parallel orientation of lamellar domains at free surface because of the lower surface energy of the PS block. The composition window of brushes that induce vertical orientation of domains near the substrate ranges from 47.8% styrene to 57.0% styrene, as determined by SEM and GISAXS measurements of films after removal of the parallel-oriented domains at surfaces (remaining film thickness ≈ 50 nm). When the PS-b-P2VP film was confined between two brushes having compositions within the above range, perpendicularoriented lamellae that traversed the film thickness were obtained.