Enhancing ordering dynamics in solvent-annealed block-copolymer films by lithographic hard masks supports

TL;DR

This study demonstrates that using a lithographic hard mask support significantly accelerates the ordering dynamics of solvent-annealed block copolymer films, enhancing chain mobility and stability, with implications for nanolithography.

Contribution

It reveals that hard mask supports increase chain mobility and ordering speed in block copolymer films independently of chemical structure, providing new insights into polymer-solvent interactions.

Findings

Ten-fold increase in chain mobility on hard mask supports.

Enhanced long-range order and faster morphological transitions.

Suppression of film dewetting even at low molecular weights.

Abstract

We studied solvent-driven ordering dynamics of block copolymer films supported by a densely cross-linked polymer network designed as organic hard mask (HM) for lithographic fabrications. The ordering of microphase separated domains at low degrees of swelling corresponding to intermediate/strong segregation regimes was found to proceed significantly faster in films on a HM layer as compared to similar block copolymer films on silicon wafers. The ten-fold enhancement of the chain mobility was evident in the dynamics of morphological phase transitions and of related process of terrace-formation on a macroscale, as well as in the degree of long-range lateral order of nanostructures. The effect is independent of the chemical structure and on the volume composition (cylinder-/ lamella-forming) of the block copolymers. In-situ ellipsometric measurements of the swelling behavior revealed a cumulative increase in 1-3 vol. % in solvent up-take by HM-block copolymer bilayer films, so that we suggest other than dilution effect reasons for the observed significant enhancement of the chain mobility in concentrated block copolymer solutions. Another beneficial effect of the HM-support is the suppression of the film dewetting which holds true even for low molecular weight homopolymer polystyrene films at high degrees of swelling. Apart from immediate technological impact in block copolymer-assisted nanolithography, our findings convey novel insight into effects of molecular architecture on polymer-solvent interactions.