Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session P55: Block Copolymer Thin Films Integrated with New Material Platforms I: Surface, Interfaces and LithographyFocus
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Sponsoring Units: DPOLY Chair: Reika Katsumata, UC Santa Barbara Room: LACC 515A |
Wednesday, March 7, 2018 2:30PM - 2:42PM |
P55.00001: Nanoscale surface topologies of non-neutral polymer adsorbed layers for the tailored control of BCP microdomain orientations Yuma Morimitsu, Justin Cheung, Daniel Salatto, Mani Sen, Naisheng Jiang, Maya Endoh, Keiji Tanaka, Tadanori Koga Nanoscale surface topography has received great attention for its ability to direct the self assembly of block copolymer (BCP) microdomain orientations in thin films. Here we report that the unique surface topological features of “non neutral polymer substrates” can be used to achieve highly aligned perpendicular lamellar orientation of BCP microdomains. The polymer substrates were composed of PS chains strongly adsorbed onto silicon substrates. Based on x-ray reflectivity and atomic force microscopy, we found that the thicknesses of the PS adsorbed layers remained constant (~2 nm in thickness) with different molecular weights (Mw), while the surface topologies changed from homogeneous for low PS to heterogeneous with a characteristic length of ~ 100 nm for high Mw PS. A lamellar forming PS-block-PMMA thin films were prepared on the polymer substrate. By using grazing incidence small angle X-ray scattering, we mapped out the phase diagram of BCP orientations at T =200 °C, a temperature which creates a neutral air surface so that the substrate surface is the only external field. The role of surface topologies in controlling the self assembly of BCP thin films from the buried interface will be discussed. |
Wednesday, March 7, 2018 2:42PM - 2:54PM |
P55.00002: Locally favored two-dimensional structures of block copolymer melts on non-neutral surfaces Tadanori Koga, Mani Sen, Naisheng Jiang, Maya Endoh, Alexander Ribbe, Daisuke Kawaguchi, Keiji Tanaka, Atikur Rahman, Detlef-M Smilgies Self-assembly of block copolymers (BCPs) into arrays of well-defined nanoscopic structures has attracted extensive academic and industrial interests over the last several decades. In contrast to the bulk, the morphologies and orientations of BCP thin films can be strongly influenced by the substrate surface energy/chemistry effect (considered as a “substrate field”). Here, we report the formation of locally favored structures where all constituent blocks coexist side-by-side on non-neutral solid surfaces irrespective of their chain architectures, microdomain structures, and interfacial energetics. The experimental results using a suite of surface-sensitive techniques intriguingly demonstrate that individual preferred blocks and non-preferred blocks lie flat on the substrate surface and form a two-dimensional percolating network structure as a whole. The large numbers of solid-segment contacts, which overcome a loss in the conformational entropy of the polymer chains, prevent the structure relaxing to its equilibrium state (i.e., forming microdomain structures) even in a solvent atmosphere. Our results provide direct experimental evidence of the long-lived, energetically favored non-equilibrium structures of BCPs. |
Wednesday, March 7, 2018 2:54PM - 3:06PM |
P55.00003: Effect of Self-assembled Wetting Layer in Block Copolymer Thin Film Dong Hyup Kim, So Youn Kim The role of the interface becomes more important in block copolymer (BCP) thin film self-assembly compared than in the bulk. The self-assembled BCP structures in the bulk are mainly governed by their segregation strength and relative block ratio, whereas in case of thin films it is additionally influenced by interface condition. Therefore, much efforts have been made to understand interfacial behaviors of BCPs and to control the self-assembled structure in the thin films. A common method is to modify substrate-BCP interactions such that the neutral polymers can be grafted onto the substrate to direct the self-assembly of BCPs. However, a simple physical coating of BCP instead of grafting cannot be employed as a wetting layer because subsequent layers can be easily intermixed upon thermal annealing. |
Wednesday, March 7, 2018 3:06PM - 3:42PM |
P55.00004: Dynamic Polymer Brush by Segregation of Amphiphilic Copolymers Invited Speaker: Hideaki Yokoyama A layer of polymer chains tethered by one end to a surface is called polymer brush and known to show various unique properties such as prevention of protein adsorption and anti-fouling activity. The surface segregation phenomena of copolymers with surface-active blocks should be useful for preparing such a brush layer in spontaneous process. We reported hydrophilic polymer brushes formed at the interface between water and hydrophobic polymer matrix by the segregation of amphiphilic diblock copolymers blended in the matrix. In this system, while the hydrophilic block with high surface energy avoids air surface it segregate to cover the interface between hydrophobic PDMS and water. The structures of formed brush layers at D2O/polymer interfaces were analyzed by neutron reflectivity (NR). The brush density was calculated to be as high as 2 chains/nm2, which is surprisingly comparable to the polymer brush fabricated by the “grafting-from” method. Moreover, even if the brush is lost or damage, the remaining block copolymers embedded in the elastomer can segregate again to repair the brush (self-repair). Therefore, the kinetics of dynamic polymer brush growth, which determines the time for self-repair, is very important. The kinetics of dynamic polymer brush formation was investigated using Quartz Crystal Microbalance (QCM), contact angle measurement and time-resolved NR. |
Wednesday, March 7, 2018 3:42PM - 3:54PM |
P55.00005: Abstract Withdrawn
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Wednesday, March 7, 2018 3:54PM - 4:06PM |
P55.00006: Improved Ordering Quality in Shear Aligned Block Copolymer Thin Films via Solvent Vapor Exposure Ye Chan Kim, Seok Joon Kwon, Su Mi Hur, So Youn Kim Block copolymers (BCPs) have the ability to create various nanoscale structures through microphase separation, but defects formed during the ordering process often interfere a successful lithographic application of BCPs. Furthermore, defect control in large area has been challenged at the application level. In this study, we introduce a facile method for the large-area defect control using solvent vapor annealing (SVA) in shear-aligned BCP thin films. Cylinder forming polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) was firstly shear-aligned and then exposed to the various solvent vapor. Grazing incidence small-angle X-ray scattering and SEM image analysis were used for quantitative characterization of SVA effects. Through the proper SVA process, it was confirmed that the correlation length of BCP film can be increased and the defect areal density and line edge roughness can be reduced, leading to a highly aligned line pattern in a large area. |
Wednesday, March 7, 2018 4:06PM - 4:18PM |
P55.00007: Orientation control of cylinder forming block-copolymer on a modulated substrate – a theoretical study Karim Gadelrab, Alfredo Alexander-Katz The self-assembly of block copolymers BCPs provides a robust tool for nano-scale patterning. The low miscibility of the polymers in each block drives phase segregation, while the arrangement of each block in the molecule limits the extent of spatial separation resulting in nanoscale periodic morphologies. Unfortunately, micro-phase separation of BCP thin films on uniform substrates are far from perfect. Corrugated substrates showed a strong influence of BCP self-assembly resulting in improved long range order and orientation control. In addition, the effect of spatial modulation was observed in multi-stacked BCP thin films, where the newly added BCP layers are influenced by the topographyand chemical characteristics of the preceding layers. |
Wednesday, March 7, 2018 4:18PM - 4:30PM |
P55.00008: Self-Alignment of Cylinder-Structured Silicon-Containing Block Copolymer Films Rong-Ming Ho, Kai-Yuan Lu, Hsiao-Fang Wang, Prokopios Georgopanos, Apostolos Avgeropoulos, An-Chang Shi The formation of well-ordered perpendicular cylinders of star-block copolymers (BCPs) composed of polystyrene and poly(dimethylsiloxane) blocks with high aspect ratio can be achieved by using a combination of architecture effect (entropy effect) and surface air plasma treatment (enthalpy effect). An interesting morphological evolution from disordered texture to hexagonally packed cylinders with perpendicular orientation can be found at which the perpendicular cylinders simultaneously develop from the top surface of the thin film and also the bottom substrate through the nucleation and growth process followed by the formation of span-thru cylinders through the self-alignment process with the improvement of lateral ordering. Those results suggest a unique mechanism for the induced orientation and lateral ordering of BCP thin films through the nucleation and growth process followed by self-alignment process; this finding may provide an insight for the mechanisms of BCP self-assembly in the thin-film state to give the nanopatterns with controlled orientation and long-range ordering. |
Wednesday, March 7, 2018 4:30PM - 4:42PM |
P55.00009: Generating long-range order in gyroid terpolymer films by controlled solvent annealing Karolina Korzeb, James Dolan, Narjes Abdollahi, Ulrich Wiesner, Ullrich Steiner, Ilja Gunkel Gyroid-structured triblock terpolymer films can be used as templates for the fabrication of optical metamaterials. For samples with large gyroid grains these plasmonic materials exhibit interesting optical properties, e.g. linear dichroism (1). However, generating templates with long-range order still remains a challenge as only little is known about the self-assembly of gyroid-structured polymer films. In this work, we show that gyroid films with long-range order can be prepared by controlled solvent vapor annealing of a PI-b-PS-b-PGMA (ISG) triblock terpolymer. Gyroid grains of about 5-15 µm in size were produced by slowly removing the solvent from swollen, ordered ISG terpolymer films. These films were shown to serve as templates for the fabrication of optical metamaterials as demonstrated by the replication of gyroid-structured polymer films into gold. Gyroid terpolymer templates and gold replica were characterized by a combination of scattering (GISAXS, SAXS) and microscopy techniques (AFM, SEM). |
Wednesday, March 7, 2018 4:42PM - 4:54PM |
P55.00010: Mechanisms of Directed Self-assembly in Cylindrical Hole Confinements Cody Bezik, Grant Garner, Juan De Pablo The directed self-assembly of block copolymers in cylindrical holes is a promising technology for lithographic patterning, particularly in the context of vertical interconnect accesses. While the hole-shrink process for single cylinders has been extensively explored, the proliferation of morphological defects remains a significant technological barrier. We use a coarse-grained model to explore morphologies that form within cylindrical confinements for combinations of template surface energies. We identify metastable defect morphologies, in addition to the desired cylindrical morphology, in majority-wetting sidewall templates. We use our coarse-grained model and the string method to identify transition pathways between defective morphologies and the cylindrical morphology to elucidate the mechanism of defect annihilation within the confinements; the transition pathway from a disordered state is also identified. This work demonstrates that the minimum free energy path for the formation of a cylinder goes through defective morphologies, and that designing confinements can eliminate these undesirable transition states. |
Wednesday, March 7, 2018 4:54PM - 5:06PM |
P55.00011: Templated Self-assembly of PS-branch-PDMS Janus Bottle Brush Copolymer Li-Chen Cheng, Ken Kawamoto, Karim Gadelrab, Kevin Yager, Alfredo Alexander-Katz, Jeremiah Johnson, Caroline Ross Self-assembly of block copolymers is a promising route for technological applications to fabricate numerous structures with length scales of a few to several hundred nm. However, scalability below 10 nm remains challenging. Here we show that novel Janus-type bottle brush copolymers (BBCPs) break conventional χN limit, scaling with the length of the side chains instead of the overall backbone length. We report the synthesis and self-assembly of PS-branch-PDMS BBCP, featuring a backbone with a tunable degree of polymerization connecting immiscible blocks, instead of having each type of sidechain at one end of the molecule as in conventional BBCPs. Thin morphologies of BBCP with fPDMS = 26% and Mn = 609 kg/mol were investigated using solvent vapor annealing. Long-range ordered 22-nm cylindrical microdomains in thin films were achieved, and the correlation length was quantified under different as-cast film thickness, solvent vapor pressure, and composition of the binary mixture of solvent vapors. Rapid dynamic self-assembly process was characterized using In-situ GISAXS. Templated self-assembly of BBCP within lithographically patterned substrate was demonstrated, showing distinct pattern orientation and dimensions that are difficult to achieve from traditional block copolymers. |
Wednesday, March 7, 2018 5:06PM - 5:18PM |
P55.00012: Fabrication of Sub 3 nm Feature Size Based on Block Copolymer Self Assembly for Next-Generation Nanolithography Kyuseong Lee, Jongheon Kwak, Avnish Mishra, Jin Kon Kim 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 nextgeneration 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 (fPS). 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 fPS = 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 fPS = 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 |
Wednesday, March 7, 2018 5:18PM - 5:30PM |
P55.00013: Simultaneous Fabrication of Line and Dot Dual Nanopatterns using Miktoarm Block Copolymer Thin Film with Photocleavable Linker Chungryong Choi, Seonghyeon Ahn, Jaeyong Lee, Kyuseong Lee, Jin Kon Kim Block copolymers with various nanodomains, such as spheres, cylinders, and lamellae have received attention for their applicability to nanolithography. However, those microdomains are determined by the volume fraction of one block. Meanwhile, nanopatterns with multiple shapes are required for the next-generation nanolithography. Although various methods have been reported to achieve dual nanopatterns, all the methods need sophisticated processes using E-beam. |
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