Synthesis And Self-Assembly Of High-Chi Poly(4-Tertbutylstyrene)-Block-Poly(2-Hydroxyethylmethacrylate)

Block copolymers (BCPs) are utilized by the microelectronics industry for their ability to phase separate at very small length scales (< 20 nm). By casting these BCPs as a thin film on a substrate, the BCPs can phase separate into patterns that can be used as an etching template to transfer features into the substrate. The spacing between features is determined by the natural pitch of the BCP which is dependent on both the Flory-Huggins interaction parameter, chi, and the degree of polymerization, N. The pitch is more dependent on N than chi, meaning a low N, high-chi material is required to reach small pitches. Here, the synthesis and characterization of the BCP, poly(4-tertbutylstyrene)-b- poly(hydroxyethylmethacrylate) (PtBS-b-PHEMA), is reported. Small angle x-ray scattering and atomic force microscopy showed that PtBS-b-PHEMA was able to form cylindrical and lamellar forming morphologies with a pitch of 10 nm and sub-7 nm, respectively. With these pitches, the chi of PtBS-b-PHEMA is expected to be greater than 0.4. Random copolymer underlayers were crafted for the BCP to phase separate on in an attempt to perpendicular features; however, a neutral underlayer has yet to be found. Published by the AVS.