Functional Organic Materials for Directed Self-assembly of Block Copolymers
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Directed self-assembly (DSA) of block copolymers (BCPs) has attracted a great deal of attention due to the potential for fabricating next-generation microelectronic devices. A hybrid chemo-/grapho-epitaxial alignment strategy is an effective strategy that was developed to reduce the defect density. It was hypothesized that the DSA could be achieved only with the interaction of a polar block of a BCP with a polar sidewall of guidelines. The challenge was to increase the polarity of the sidewall while rendering the SiO2 substrate neutral to the BCP. This work shows the development of polymer brushes with the grafting selectivity required to control surface energies at the bottom interfaces of the BCP. It was found that hydroxyl-terminated brushes graft selectively on the SiO2, while amine-terminated brushes selectively graft on the sidewalls. Sequential grafting of these brushes resulted in the neutral SiO2 substrate and polar sidewalls necessary to achieve the hybrid DSA.