Directed Self-Assembly of Block Copolymer Thin Films into Useful Organized Patterns for Microelectronics and Nanofabrication.

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This grant supports research that creates new understanding and capabilities regarding a manufacturing process enabling the fabrication of patterns and features on surfaces that are extremely small -- only a few billionths of a meter (a few nanometers) in extent. Precision fabrication at these lengths is driving manufacturing advances in areas of national importance including microelectronics, optical materials, sensors, chemical purification membranes, and quantum materials. This award supports fundamental research on block copolymer-based nanofabrication. When two different conventional polymers that do not “like” each other are mixed, the two polymers separate – like oil and water. However, when these two polymers are bonded to each other – to form a block copolymer – macroscopic separation is inhibited, and nanoscale segregation occurs instead. Features smaller than hundred (100), ten (10), and even five (5) nanometers are generated automatically, that cannot be easily created otherwise. This project focuses on spatially directing this nanoscale segregation on surfaces so that rationally organized and useful (as opposed to random) patterns can be formed. An example is nanopatterning the surfaces of semiconductors for computer chips so that they perform faster, are more energy efficient, and can be more complex. The research integrates advanced concepts from materials science and engineering, chemistry, and nanomanufacturing. The interdisciplinary research helps widen the involvement of diverse groups in fundamental research and constructively influences science and engineering education.This research specifically addresses the challenge of registering and directing the self-assembly of vertically oriented block copolymer lamellar domains into rationally controlled sub-lithographic patterns through the exploitation of boundary-directed epitaxy. Boundary-directed epitaxy uses the abrupt chemical contrast that is inherent at spatial boundaries between regions on a substrate with different surface composition to direct the registration, alignment, and self-assembly of block copolymers. The advantages are substantial: the boundaries can be defined between features that are planar and relatively large – circumventing the need for trenches or high-resolution chemical patterns. The mechanisms that drive self-assembly are highly unexplored. The project determines the chemical composition / preferentiality window for boundary-directed epitaxy; quantifies the impact of boundary-roughness on assembly; characterizes how defects arise; and understands how the assembly evolves over time. The project studies and demonstrates boundary-directed epitaxy for nanofabrication, materials synthesis, and nanolithography; investigates assembly on templates with curved boundaries and complex shapes – essential for many applications; and, broadens the library of template materials that can be exploited to advance the generality of the phenomenon.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.