Synthesis and self-assembly of high-χ poly(4-tertbutylstyrene)-block-poly(2-hydroxyethylmethacrylate)

Abstract

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, χ, and the degree of polymerization, N. The pitch is more dependent on N than χ, meaning a low N, high-χ 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 χ 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.

Polyacrylonitrile-containing amphiphilic block copolymers: self-assembly and porous membrane formation

“…PHEMA is a building block that has been scarcely investigated regarding its microphase separation capability in the bulk state. 22,79,80 The BCP investigated in this work carries functional moieties in both BCP segments, resulting in a highly interesting material whose overall properties are yet to be discovered. Aside from that, the capability of a BCP to form isoporous membranes by SNIPS depends strongly on their phase separation capabilities, as χ⋅N (where χ is the Flory-Huggins interaction parameter) is one of the most important variables herein.…”

Hydrolysis-Induced Morphology Evolution of Linear and Bottlebrush Block Copolymers in Thin Films with Acid Vapor or Photoacid Generators

“…The feature size of transistors is limited by the resolution of photolithography, despite the use of extreme ultraviolet lithography and multipatterning . As top-down photolithography approaches the diffraction limit, bottom-up self-assembly of block copolymers (BCPs) has proven to be a promising alternative route to give patterns on the nanometer level. − Lamellar and cylindrical patterns with sub-10 nm full pitch have been reported. − The feasibility of integrating BCP self-assembly into the fabrication of critical device layers has been verified at the 7 nm process of fin field-effect transistors (FinFET). − …”