Transient, Reusable Top-Coats for the Vertical Orientation of High-χ Block Copolymers for Nanopatterning

Block copolymer (BCP) self-assembly is a promising nanopatterning technique capable of efficiently forming ultrafine patterns in large areas. One of the fundamental challenges encountered in the successful application of BCP templates to nanolithography is the vertical orientation of block copolymers with high Flory–Huggins interaction parameters (χ). Recent advances in top-coat approaches have enabled the facile vertical orientation of high-χ block copolymer (BCP) patterns, thereby increasing the applicability of high-resolution BCP nanolithography. Herein, a method for the fabrication of a transient and reusable top-coat is reported to address the limitations of a traditional top-coat approach for achieving the vertical orientation of high-χ BCPs. An elastomeric top-coat pad composed of a neutral polymer brush is designed such that it adheres to various surfaces and readily detaches itself after self-assembly, thus simplifying the fabrication process and enabling multiple uses of the top-coat. This method successfully produces the vertically oriented lamellar structures of poly(styrene- b -(2-vinyl pyridine)), a representative high-χ BCP. In addition, unidirectionally aligned patterns are obtained over a large area by applying shear stress during the self-assembly of the BCPS using the top-coat pad. The transient neutral top-coat pads can also be reliably reused several times in different BCP thin films. This innovative top-coat method can be potentially used for inducing vertical orientations of high-χ BCPs and can be integrated with ultrafine pattern fabrication processes, especially in the semiconductor industry.