Assembly of block copolymer films between chemically patterned and chemically homogeneous surface

Many technologically useful block copolymer systems other that poly(styrene-block-methylmethacrylate) are currently not amenable for directed assembly because one of the blocks has a lower surface energy, segregates to the free surface of the film, and disrupts directed assembly of the film (at least with respect to realizing perpendicularly oriented through-film domains) on the underlying chemical pattern. Cross-linkable random copolymer mats were developed as well as methods to deposit them on the surfaces of block copolymer films. The chemistry of these ``top coats'' can be tuned to impart preferential and non-preferential wetting properties towards the blocks of the block copolymer films. The three-dimensional morphology of block copolymers assembled between lithographically-defined chemically patterned surfaces and top coats of varying wetting properties were characterized using specialized sample preparation techniques and cross-sectional scanning electron microscopy. The resulting structures compare favorably with molecular simulations. A primary technological objective of the top coat strategy is to direct the assembly of block copolymer systems that allow for sub-10 nm patterning and perpendicularly oriented domains.