Effect of Trapped Solvent on the Interface between PS-b-PMMA Thin Films and P(S-r-MMA) Brush Layers

Abstract

The orientation of block copolymer (BCP) features in thin films can be obtained by spin-coating a BCP solution on a substrate surface functionalized by a polymer brush layer of the appropriate random copolymer (RCP). Although this approach is well established, little work reporting the amount and distribution of residual solvent in the polymer film after the spin-coating process is available. Moreover, no information can be found on the effect of trapped solvent on the interface between the BCP film and RCP brush. In this work, systems consisting of poly­(styrene)-b-poly­(methyl methacrylate) thin films deposited on poly­(styrene-r-methyl methacrylate) brush layers are investigated by combining neutron reflectivity (NR) experiments with simulation techniques. An increase in the amount of trapped solvent is observed by NR as the BCP film thickness increases accompanied by a significant decrease of the interpenetration length between the BCP and RCP, thus suggesting that the interpenetration between grafted chains and block copolymer chains is hampered by the solvent. Hybrid particle-field molecular dynamics simulations of the analyzed system confirm the experimental observations and demonstrate a clear correlation between the interpenetration length and the amount of trapped solvent.

Resist-Free Directed Self-Assembly Chemo-Epitaxy Approach for Line/Space Patterning

“…In this case, the chemical pattern created guides the perpendicular-oriented lamellae, achieving the DSA. As previously reported in the literature, experimental [24,25] and computational [26] studies confirmed that the interpenetration region between systems consisting of polymeric films deposited onto grafted brush layers increases with the molar mass of the brush layer by fixing the molar mass of the polymer film. Although these previous studies investigated the interpenetration between layers and not the lateral interpenetration, they can be useful to give a plausible explanation to the results obtained in the present work.…”

Influence of spin casting solvent on the self‐assembly of silicon‐containing block copolymer thin films via high temperature thermal treatment

“…In previous work we demonstrated that the presence of residual toluene in spin‐coated PS‐ b ‐PMMA thin films significantly affects the SA and grain coarsening processes 21–23 . This residual solvent is located at the interface between the random brush layer that is used to neutralize the substrate and the block copolymer thin film and represents a reservoir of solvent that is progressively released during the annealing process.…”

“…Recently, our group demonstrated that by properly increasing the heating rate at 18 °C s −1 in a rapid thermal processing (RTP) machine, the onset of the degradation process of PDMS‐containing DBC thin films shifts to T > 400 °C, permitting operation at T = 310 °C without any evidence of degradation 20 . Moreover, we demonstrated that the solvent that is naturally trapped in the polymeric film during the spin coating process significantly influences the correlation length ( ξ ) evolution in PS‐ b ‐PMMA (PMMA, polymethylmethacrylate) DBC films during a thermal treatment performed in the RTP machine 21–23 . In particular, we showed that, after a ramp to achieve the target temperature of the thermal treatment, there is still a considerable amount of residual solvent retained in the block copolymer films that increases the polymer chain diffusivity and accelerates the kinetics of the SA process 22 .…”

Full parameter space exploration of microphase separation of block copolymer brushes within a single simulation framework

“…Relaxing the assumption of uniform brush thickness and introducing selective affinity of the substrate or the top in a model can produce a more enriched phase behavior. The morphologies of BCP brushes under solvents have also been studied using SCFT [26][27][28][29][30] , lattice Monte Carlo 31,32 , single-chain-in-mean-field (SCMF) 33 , dissipative particle dynamics (DPD) 34,35 , hybrid Molecular Dynamics(MD) with field representation of non-bonded interactions 36,37 ,and density functional theory (DFT) simulations 38 . Despite such explorations, obtaining a comprehensive understanding on the formation of morphology in brush systems under different conditions, i.e., melt or exposed to solvent molecules, has been a key challenge.…”