Enhancing Ordering Dynamics in Solvent-Annealed Block
Copolymer Films by Lithographic Hard Mask Supports
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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 10-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 uptake 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