Control of the critical dimensions and line edge roughness with pre-organized block copolymer pixelated photoresists

Sphere-forming polystyrene-block-poly(t-butyl acrylate) (PS-b-PtBA) diblock copolymer with catalytic amounts of photo-acid generator (PAG) formulated a pixelated photoresist. In thin films with single-sphere thickness, hexagonal arrays of spheres (similar to 20 nm diameter on a 40 nm pitch) of PS within a matrix of PAG segregated in PtBA was obtained through solvent annealing. Upon exposure and post-exposure baking, the soluble PtBA matrix was converted to insoluble poly(acrylic acid), such that a negative pattern could be formed in the chlorobenzene developer. The concept of pixelation was demonstrated by exposing line and space patterns with increasing widths. In contrast to the width of the exposure fields that increased monotonically, the widths of the pixelated resist structures after development were quantized with respect to an integer number of rows of spheres. Furthermore, line edge roughness could be correlated with the size of each pixel (diameter of spherical domain).