This report describes the design and synthesis of a series of lamella‐forming, silicon‐containing block copolymers (Si‐BCPs) and evaluation of these materials as potential candidates for lithographic applications. The interaction parameter χ of each Si‐BCP is measured by both the mean‐field theory predicted order‐disorder transition and by analysis of X‐ray scattering profiles. The introduction of more‐polar methoxy and less‐polar methylsilyl moieties increases χ to about 2–3 times that of the reference material, poly(styrene‐block−4‐trimethylsilylstyrene). The incremental increases appear to be essentially additive in this family of block copolymers, suggesting that improvements in χ can be predicted from appropriate monomer choice. Perpendicularly oriented thin‐films of the ordered Si‐BCPs generated by thermally annealing between two “neutral” polymeric surfaces and developed by etching on commercial RIE equipment show excellent image fidelity. These images demonstrate the excellent etch contrast of the Si‐BCPs and document improvements in pattern fidelity that are realized with more strongly segregated BCPs. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 344–352

The directed self-assembly (DSA) and pattern transfer of poly(5-vinyl-1,3-benzodioxole-block-pentamethyldisilylstyrene) (PVBD-b-PDSS) is reported. Lamellae-forming PVBD-b-PDSS can form well resolved 5 nm (half-pitch) features in thin films with high etch selectivity. Reactive ion etching was used to selectively remove the PVBD block, and fingerprint patterns were subsequently transferred into an underlying chromium hard mask and carbon layer. DSA of the block copolymer (BCP) features resulted from orienting PVBD-b-PDSS on guidelines patterned by nanoimprint lithography. A density multiplication factor of 4× was achieved through a hybrid chemo-/grapho-epitaxy process. Cross-sectional scanning tunneling electron microscopy/electron energy loss spectroscopy (STEM/EELS) was used to analyze the BCP profile in the DSA samples. Wetting layers of parallel orientation were observed to form unless the bottom and top surface were neutralized with a surface treatment and top coat, respectively.

Directly photopatternable interfaces are introduced that facilitate two-dimensional spatial control of block copolymer (BCP) orientation in thin films. Copolymers containing an acid labile monomer were synthesized, formulated with a photoacid generator (PAG), and coated to create grafted surface treatments (GSTs). These as-cast GST films are either inherently neutral or preferential (but not both) to lamella-forming poly(styrene-block-trimethylsilylstyrene) (PS-b-PTMSS). Subsequent contact printing and baking produced GSTs with submicron chemically patterned gratings. The catalytic reaction of the photoacid generated in the UV-exposed regions of the GSTs changed the interfacial interactions between the BCP and the GST in one of two ways: from neutral to preferential (“N2P”) or preferential to neutral (“P2N”). When PS-b-PTMSS was thermally annealed between a chemically patterned GST and a top coat, alternating regions of perpendicular and parallel BCP lamellae were formed.

In this report, we describe the preparation and characterization of a new class of thermoset fibers with high elongation and elastic recovery. Integrating UV-activated thiol-ene photopolymerization and electrospinning, we demonstrate an environmentally friendly single step approach to convert small monomeric precursor molecules into highly elastic fibers and nonwoven mats. The fibers were derived by in situ photopolymerization of a trifunctional vinyl ether monomer and a tetrafunctional thiol. Although thermosets often offer good chemical and thermal stability, these fibers also have a high average elongation at break of 62%. The elastomeric nature of these vinyl-ether based fibers can be partly attributed to their subambient Tg and partly to the cross-link density, monomer structure, and resulting network homogeneity. Nonwoven mats of these fibers were also stretchable and exhibited a much higher elongation at break of about 85%. These thermoset stretchable fibers could have potential applications as textile, biomedical, hot chemical filtration, and composite materials.

The directed self-assembly (DSA) of a 20 nm full-pitch silicon-containing block copolymer (BCP), poly­(4-methoxystyrene-b-4-trimethylsilylstyrene), was performed using a process that produces shallow topography for hybrid chemo-/grapho-epitaxy. This hybrid process produced DSA with fewer defects than the analogous conventional chemo-epitaxial process, and the resulting DSA was also more tolerant of variations in process parameters. Cross-sectional scanning transmission electron microscopy (STEM) with electron energy loss spectroscopy (EELS) confirmed that BCP features spanned the entire film thickness on hybrid process wafers. Both processes were implemented on 300 mm wafers initially prepatterned by 193 nm immersion lithography, which is necessary for economic viability in high-volume manufacturing. Computational analysis of DSA extracted from top-down SEM images demonstrates the influence of process parameters on DSA, facilitating the optimization of guide stripe width, guide stripe pitch, and prepattern surface energy. This work demonstrates the ability of a hybrid process to improve the DSA quality over a conventional chemo-epitaxial process and the potential for high-volume manufacturing with high-χ, silicon-containing BCPs.