Directed Self-Assembly of High-χ Block Copolymers for Advanced Patterning Applications

High-χ block copolymers (BCP) have gained interest to be used as an alternative to currently used multiple patterning techniques for obtaining sub-lithographic features due to their ability to self-assemble at the nanoscale. However, there is a challenge in controlling the orientation of high-χ BCPs at the air interface. This work describes the use of a formulation-based approach wherein different surface active polymers (SAP) were added as additives to control the orientation of poly(styrene-b-methyl carbonate) (PS-b-PMeCAR) lamellae at the air interface. The resulting thin films made from these formulations showed successful formation of perpendicular lamellae on neutral underlayer substrates upon thermal annealing. The higher surface active SAP demonstrated better orientation control with lower loadings and on thicker films. These films were characterized by atomic force microscopy, grazing incidence small angle x-ray spectroscopy, and x-ray photoelectron spectroscopy to confirm the perpendicular orientation of the lamellar domains and the distribution of the SAP in the BCP thin film. The vertically oriented BCP domains were used as an etch mask by selectively removing the more etch labile PMeCAR block by reactive ion etching using oxygen plasma. A technique called sequential infiltration synthesis (SIS), followed by removing the PS block to obtain ~9.5 nm half pitch domains, was also used. Directed self-assembly via graphoepitaxy was also successfully demonstrated. Future work includes investigation of different BCP platforms and morphologies other than lamellae for patterning work