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

摘要

We studied solvent-driven ordering dynamics of block copolymer filmssupported by a densely cross-linked polymer network designed as organic hardmask (HM) for lithographic fabrications. The ordering of microphase separateddomains at low degrees of swelling corresponding to intermediate/strongsegregation regimes was found to proceed significantly faster in films on a HMlayer as compared to similar block copolymer films on silicon wafers. Theten-fold enhancement of the chain mobility was evident in the dynamics ofmorphological phase transitions and of related process of terrace-formation ona macroscale, as well as in the degree of long-range lateral order ofnanostructures. The effect is independent of the chemical structure and on thevolume composition (cylinder-/ lamella-forming) of the block copolymers.In-situ ellipsometric measurements of the swelling behavior revealed acumulative increase in 1-3 vol. % in solvent up-take by HM-block copolymerbilayer films, so that we suggest other than dilution effect reasons for theobserved significant enhancement of the chain mobility in concentrated blockcopolymer solutions. Another beneficial effect of the HM-support is thesuppression of the film dewetting which holds true even for low molecularweight homopolymer polystyrene films at high degrees of swelling. Apart fromimmediate technological impact in block copolymer-assisted nanolithography, ourfindings convey novel insight into effects of molecular architecture onpolymer-solvent interactions.