For ultrahigh-density storage media and D-RAM, the feature size of lithography should be much reduced (say less than 10 nm). Though some research groups reported feature size of 5–6 nm, further reduced feature size is needed for next-generation lithography. We synthesized, via a reversible addition–fragmentation chain-transfer polymerization, polydihydroxystyrene-block-polystyrene (PDHS-b-PS) copolymers showing lamellar and cylindrical microdomains by adjusting the volume fraction of PS block (f PS). We found that the Flory–Huggins interaction parameter (χ) between PDHS and PS was very large, 0.7 at 170 °C. Because of the huge χ, the lamellar domain spacing (L) of PDHS-b-PS with a total molecular weight of 2.1 kg mol–1 and f PS = 0.5 was only 5.9 nm; thus, a sub-3 nm feature size (half-pitch) was successfully obtained. Furthermore, PDHS-b-PS with a molecular weight of 4.2 kg mol–1 and f PS = 0.79 showed hexagonally packed cylinders with 4 nm diameter. We also obtained thin films of PDHS-b-PS with cylindrical microdomains, showing 8.8 nm center-to-center spacing. Furthermore, we fabricated ultrahigh-density ZrO2 nanowire arrays from the cylindrical monolayer thin films via atomic layer deposition, indicating an applicability of PDHS-b-PS for next-generation lithography.

Highly asymmetric lamellar microdomains, such as those required for many lithographic line patterns, cannot be straightforwardly achieved by conventional block copolymer self-assembly. We present a conceptually new and versatile approach to produce highly asymmetric lamellar morphologies by the use of binary blends of block copolymers whose components are capable of hydrogen bonding. We first demonstrate our strategy in bulk systems and complement the experimental results observed by transmission electron microscopy and small-angle X-ray scattering with theoretical calculations based on strong stretching theory to suggest the generality of the strategy. To illustrate the impact on potential lithographic applications, we demonstrate that our strategy can be transferred to thin film morphologies. For this purpose, we used solvent vapor annealing to prepare thin films with vertically oriented asymmetric lamellar patterns that preserve the bulk morphological characteristics. Due to the highly asymmetric lamellar microdomains, the line width is reduced to sub-10 nm scale, while its periodicity is precisely tuned.

wileyonlinelibrary.comspeed, and simplicity of the process. [1][2][3][4][5] Although vertical orientation of lamellar and cylindrical nanodomains of block copolymers on a substrate is desirable, parallel orientation is usually obtained in a thin fi lm because of different affi nity between two block segments in a block copolymer toward the substrate and/or air. To induce vertical orientation, diverse preor post-treatments to neutralize the preferential affi nity have been introduced in the literature, for instance, solvent vapor annealing, [6][7][8][9] surface neutralization by random copolymer brush treatment, [10][11][12] blend system, [ 13 ] graphoepitaxy, [ 14,15 ] temperature gradient, [ 16,17 ] electric fi eld [ 18,19 ] or top coating. [20][21][22] Among them, solvent vapor annealing is one of the most powerful post-treatment methods for developing vertical orientation of block copolymer nanodomains. However, this method is diffi cult to apply for industrial applications owing to the use of solvents and the dewetting problem. To avoid using solvent, thermal annealing of block copolymer thin fi lms would be the most promising platform for commercialization of DSA due to easy and large scale process. However, to induce vertically oriented nanodomains, neutralization of a substrate by various surface modifi cations, for instance, functionalization with random copolymers, introducing rough substrates, employing graphene fi lms or nanoparticle monolayers, [ 11,13,[23][24][25] is still needed to tune interfacial interactions between a substrate and each block of the block copolymer. Therefore, a simple and cost-effective DSA process that does not require above-mentioned neutralization methods and solvent vapor annealing is demanded for the fabrication of vertically oriented nanodomains to compete with conventional top-down lithography.Kramer and co-workers [ 26 ] investigated the effect of block copolymer chain architecture on the orientation of nanodomains in relatively thick fi lms (600-800 nm) using poly(cyclohexylethylene)-block -poly(ethylene) (PCHE-b -PE) block copolymers. They found that PCHE-b -PE-b -PCHE triblock copolymer showed perpendicularly oriented nanodomains by introducing lower surface energy block as the midblock, whereas PCHE-b -PE diblock copolymer exhibited parallel Vertical Orientation of Nanodomains on Versatile Substrates through Self-Neutralization Induced by Star-Shaped Block CopolymersSangshin Jang , Kyuseong Lee , Hong Chul Moon , Jongheon Kwak , Jicheol Park , Gumhye Jeon , Won Bo Lee , and

We investigated, via small-angle X-ray scattering and transmission electron microscopy, the morphologies of binary blend of polyisoprene-b-polystyrene-b-poly­(2-vinylpyridine) (ISP) triblock terpolymer and polyisoprene-b-polystyrene (IS) diblock copolymer. An asymmetric ISP with volume fractions (f) of 0.12, 0.75, and 0.13 for PI, PS, and P2VP blocks, respectively, showed a new morphology: coexistence of spheres and cylinders with tetragonal packing. Asymmetric IS with f I = 0.11 and f S = 0.89 showed conventional body-centered cubic spherical microdomains. Very interestingly, a binary blend of ISP and IS with overall volume fractions of f I = 0.12, f S = 0.79, and f P = 0.09 exhibited core–shell double gyroid (CSG: Q230 space group), where PI consists of thin core and PS forms thick shell, while P2VP becomes thin matrix. It is very unusual to form CSG even at highly asymmetric volume fractions.

No abstract

The phase behavior of 18-arm star-shaped polystyrene-block-poly(methyl methacrylate) copolymers ((PS-b-PMMA)18) with various volume fractions of PMMA block (f PMMA) was investigated by transmission electron microscopy and small-angle X-ray scattering. (PS-b-PMMA)18 was synthesized by atom transfer radical polymerization from α-cyclodextrin (α-CD) having 18 functional groups for the initiation. We also prepared the corresponding linear PS-b-PMMAs by cutting the ester groups connecting α-CD and PS chains in (PS-b-PMMA)18 through the hydrolysis. The microdomains of (PS-b-PMMA)18 changed from body-centered-cubic spheres (BCC), hexagonally packed cylinders (HEX), perforated lamellae (PL), and lamellae (LAM), with increasing f PMMA from 0.3 to 0.8. Interestingly, (PS-b-PMMA)18 with f PMMA of 0.77 showed highly asymmetric lamellar microdomains, while the corresponding linear PS-b-PMMA with the same volume fraction should not have lamellar microdomains. Thus, the microdomains are highly affected by the molecular architecture of block copolymer. The experimental results are discussed with the prediction based on the self-consistent mean-field theory.

No abstract

To apply well-defined block copolymer nanopatterns to next-generation lithography or high-density storage devices, small line edge roughness (LER) of nanopatterns should be realized. Although polystyrene-block-poly(methyl methacrylate) copolymer (PS-b-PMMA) has been widely used to fabricate nanopatterns because of easy perpendicular orientation of the block copolymer nanodomains and effective removal of PMMA block by dry etching, the fabricated nanopatterns show poorer line edge roughness (LER) due to relatively small Flory-Huggins interaction parameter (χ) between PS and PMMA chains. Here, we synthesized PS-b-PMMA with urea (U) and N-(4-aminomethyl-benzyl)-4-hydroxymethyl-benzamide (BA) moieties at junction of PS and PMMA chains (PS-U-BA-PMMA) to improve the LER. The U-BA moieties serves as favorable interaction (hydrogen bonding) sites. The LER of PS line patterns obtained from PS-U-BA-PMMA was reduced ∼25% compared with that obtained from neat PS-b-PMMA without BA and U moieties. This is attributed to narrower interfacial width induced by hydrogen bonding between two blocks, which is confirmed by small-angle X-ray scattering. This result implies that the introduction of hydrogen bonding into block copolymer interfaces offers an opportunity to fabricate well-defined nanopatterns with improved LER by block copolymer self-assembly, which could be a promising alternative to next-generation extreme ultraviolet lithography.