  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.
