Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session B6: Thin Films - Block CopolymersFocus
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Sponsoring Units: DPOLY Chair: Bryan Vogt, University of Akron Room: 265 |
Monday, March 13, 2017 11:15AM - 11:27AM |
B6.00001: Solvent-Vapor-Mitigation of Electrostatics in 3D Cyclopropenium Diblock Copolyelectrolyte Network Sebastian Russell, Sanat Kumar, Luis Campos Photolithography is progressively becoming an obsolete manufacturing technique in the microelectronic industry as block copolymer (BCP) nanoassembles approach sub 10-nm features sizes. Thermodynamically, the morphology and limiting feature size, for BCP, are determined by the relative volume fraction and magnitude of the incompatibility ($\chi $N) between each block. Therefore, to achieve smaller dimensions, it is imperative to devise copolymer systems that are strongly segregating ($\chi $N \textgreater \textgreater 10) by utilizing high monomer incompatibility, large $\chi $. For synthetic cylinder forming BCPs, achieving sub-10 nm features with a high degree of lateral ordering still remains a challenge. Covalently bound ions could potentially be a route towards enhancing the segmental incompatibility and this presentation will focus on the self-assembly of post-polymerization functionalized cyclopropenium-ion diblock copolyelectrolytes (DBCPE) through solvent vapor annealing. By varying the BCPE's total degree of polymerization and charge fraction we have mapped the kinetic phase-space. This control over morphology has opened the door to sub-10nm features with tunable densities by varying the length of the neutral and polyelectrolyte block, respectively. [Preview Abstract] |
Monday, March 13, 2017 11:27AM - 11:39AM |
B6.00002: String method study of heterogeneous nucleation Sarah Dawson, An-Chang Shi The self-assembly of block copolymers into ordered microphases typically proceeds through nucleation. The free-energy barrier and the nucleation pathway are altered in the presence of a nucleating agent. By exploiting this fact, recent theoretical work has shown that an appropriately designed substrate may be used to fabricate defect-free films of block copolymers in an ordered phase. In this work, we look at a method for quantifying the effect of heterogeneities on the nucleation pathway in a model system. We find the minimum free energy path between the initial, metastable state and the stable state using the string method. We investigate the change in height of the free-energy barrier when the interface is included. The results obtained are compared with those from classical nucleation theory. [Preview Abstract] |
Monday, March 13, 2017 11:39AM - 11:51AM |
B6.00003: Reduced defectivity in lamellae through combined thermal and solvent annealing Corinne Carpenter, Kris Delaney, Glenn Fredrickson We present a combination of string calculations and self-consistent field theoretic (SCFT) calculations of a symmetric block copolymer (BCP) in the presence of a small molecule solvent in order to examine its effects on the stability of dislocations and disclinations in confined lamellar systems. The use of string calculations provides information about the relevant energy barriers in the melting pathways of the two relevant defects at a range of solvent concentrations. As the defect is resolvated, we expect its extensive free energy difference from the perfect lamellar structure to increase, leading to a lower concentration of these defects at equilibrium. By combining these defect energies and their solvent conditions, we propose potential experimental annealing conditions for the removal of the two most prominent defects in the confined lamellar system. [Preview Abstract] |
Monday, March 13, 2017 11:51AM - 12:27PM |
B6.00004: Block copolymer films: Hierarchical meshes and bottlebrush morphologies Invited Speaker: Caroline Ross Thin films of microphase separated block copolymers have applications in diverse fields including nanolithography, porous membranes, and nanostructured surfaces. Block copolymers with a polydimethylsiloxane (PDMS) block, such as polystyrene-b-PDMS (PS-b-PDMS), are particularly attractive for producing nanoscale patterns due to their high interaction parameter and to the etch selectivity and etch resistance of the PDMS block with respect to the organic block. In this presentation we will first illustrate how sequential multilevel assembly of PS-b-PDMS with different molecular weights can produce nanomesh structures consisting of overlaid orthogonal cylindrical microdomains, without requiring layer-by-layer alignment or high-resolution lithographic templating. The mechanism for orthogonal self-assembly is investigated using both experiment and self-consistent field theory, showing that the height and chemical preference of the underlying surface are critical process parameters. Furthermore, these hierarchical topographical surfaces show extreme hydrophobicity, providing a simple method for surface property modification. We then discuss how the well-known relationship between microdomain period and degree of polymerization, which limits the scaling of block copolymers, can be overcome through the use of novel molecular architectures. Thin films of pseudo-alternating bottlebrush block copolymers show a microdomain period governed by the brush length instead of the backbone length, leading for example to <10-nm microdomains from polymers of 600 kg/mol. These patterns can be guided using topographical templates. Finally, we demonstrate the thin-film morphologies of PS-b-PDMS with majority PDMS, including the use of UV irradiation to stabilise the microdomains after solvent vapor annealing. These results illustrate the diversity of possible morphologies, periods and microdomain orientations obtained from PS-b-PDMS block copolymers. [Preview Abstract] |
Monday, March 13, 2017 12:27PM - 12:39PM |
B6.00005: Annihilation Kinetics of Dislocation Pairs in Directed Self-Assembly of Block Copolymer Thin Films Su-Mi Hur, Vikram Thapar, Abelardo Ramírez-Hernández, Paulina Rincon Delgadillo, Paul Nealey, Juan de Pablo Understanding the mechanism of defect annihilation in block copolymer self-assembly is critical in developing materials and processes leading to target morphologies. The complex interactions between unstable defects in a high defect density drive the ordering formation at the beginning stage of self-assembly. But, the latter stage involves metastable distinguishable defects. Here, our study is focused on understanding the motion of these defects and interactions among them. Previous studies have predicted the minimum free energy path (MFEP) connecting a jog defect (adjacent dislocations with the opposite sign of Burgers vector) to a perfect lamellae, and showed that defect annealing is an activated process. This MFEP shows a kinetic energy barrier only in the order of kT, implying that the system can make a transition to perfect lamellae easily. However, since the attraction between the dislocations decays with distance, two initially separated dislocation pair will interact weakly and the precise route to their annihilation has to be investigated. In this work, we present calculations aiming to understand how such dislocation pairs interact and move toward perfect lamellae both on patterned and unpatterned substrates. We also discuss how pinning on guiding stripes alters the MFEP. Our results further provide an explanation of experimental observations, which show a difference in the frequency of encountering dislocation pairs depending on the relative position to the guiding stripes. [Preview Abstract] |
Monday, March 13, 2017 12:39PM - 12:51PM |
B6.00006: Coarse-Graining Polymer Field Theory for Fast and Accurate Simulations of Directed Self-Assembly Jimmy Liu, Kris Delaney, Glenn Fredrickson To design effective manufacturing processes using polymer directed self-assembly (DSA), the semiconductor industry benefits greatly from having a complete picture of stable and defective polymer configurations. Field-theoretic simulations are an effective way to study these configurations and predict defect populations.\\ Self-consistent field theory (SCFT) is a particularly successful theory for studies of DSA. Although other models exist that are faster to simulate, these models are phenomenological or derived through asymptotic approximations, often leading to a loss of accuracy relative to SCFT.\\ In this study, we employ our recently-developed method to produce an accurate coarse-grained field theory for diblock copolymers. The method uses a force- and stress-matching strategy to map output from SCFT simulations into parameters for an optimized phase field model. This optimized phase field model is just as fast as existing phenomenological phase field models, but makes more accurate predictions of polymer self-assembly, both in bulk and in confined systems. We study the performance of this model under various conditions, including its predictions of domain spacing, morphology and defect formation energies. [Preview Abstract] |
Monday, March 13, 2017 12:51PM - 1:03PM |
B6.00007: Film growth kinetics and electric field patterning during electrospray deposition of block copolymer thin films Kristof Toth, Hanqiong Hu, Youngwoo Choo, Michael Loewenberg, Chinedum Osuji The delivery of sub-micron droplets of dilute polymer solutions to a heated substrate by electrospray deposition (ESD) enables precisely controlled and continuous growth of block copolymer (BCP) thin films. Here we explore patterned deposition of BCP films by spatially varying the electric field at the substrate using an underlying charged grid, as well as film growth kinetics. Numerical analysis was performed to examine pattern fidelity by considering the trajectories of charged droplets during flight through imposed periodic field variations in the vicinity of the substrate. Our work uncovered an unexpected modality for improving the resolution of the patterning process via stronger field focusing through the use of a second oppositely charged grid beneath a primary focusing array, with an increase in highly localized droplet deposition on the intersecting nodes of the grid. Substrate coverage kinetics are considered for homopolymer deposition in the context of simple kinetic models incorporating temperature and molecular weight dependence of diffusivity. By contrast, film coverage kinetics for block copolymer depositions are additionally convoluted with preferential wetting and thickness-periodicity commensurability effects. [Preview Abstract] |
Monday, March 13, 2017 1:03PM - 1:15PM |
B6.00008: Vertically Oriented Microdomains of Lamellar Block Copolymer Films with High Temperature Gradient Cold Zone Annealing Monali Basutkar, Saumil Samant, Joseph Strzalka, Alamgir Karim Directed Self-Assembly (DSA) to orient lamellar Block Copolymer ($l$-BCP) microdomains vertical is essential to future nanotechnology applications ranging from ion conducting membranes for batteries to nanolithography owing to their high surface area to volume ratio, aspect ratio and smooth sidewall profile. Progress has been made in developing vertically ordered $l$-BCP thin films through strategies such as neutral substrate brushes and top coats, graphoepitaxy, nanoscale roughness, etc. We report the DSA design and development of highly ordered vertical $l$-BCP microdomains of polystyrene-b-polymethyl methacrylate films by a dynamic thermal gradient process, Cold Zone Annealing with Sharp thermal gradient (CZA-S). This rapid (2-4 min.) one-step CZA-S process demonstrates vertical ordering in $l$-BCP films that are multiple times thicker than the domain spacing L$_{\mathrm{o}}$ (upto 850nm, 23L$_{\mathrm{o}})$ without any substrate pretreatment. We demonstrate the dynamics of nanostructure formation and morphology evolution in $l$-BCP films along the CZA-S thermal gradient through \textit{insitu} Grazing Incidence Small Angle X-ray Scattering that reveals fundamental insights into the physics of vertical ordering in $l$-BCPs through this process. [Preview Abstract] |
Monday, March 13, 2017 1:15PM - 1:27PM |
B6.00009: Pathway-engineered highly aligned block copolymer array using soft-shear laser zone annealing Youngwoo Choo, Pawel Majewski, Kevin Yager, Chinedum Osuji Directed self-assembly (DSA) of block copolymers (BCPs) using soft-shear laser zone annealing (SS-LZA) was employed as a scalable and cost-effective method to fabricate highly ordered nanoscale templates. A systematic series of studies were conducted to elucidate the roles of surface neutrality and alignment pathway on the SS-LZA process. BCP thin films were prepared in a simple and rapid two-step non-equilibrium process that enables to engineer the alignment pathway of the block copolymers to achieve high unidirectional order of the BCP array. Cylinder-forming poly(styrene-b-methylmethacrylate) (PS-b-PMMA) thin films were deposited on non-preferential substrates followed by SS-LZA to align the cylinders parallel to the substrate. The resulting cylinders show high correlation length over large area (\textasciitilde 100 $\mu $m) with order parameter (S) \textasciitilde 1. The films were then thermally annealed using rapid photothermal processor. After the post-annealing, we observe that the orientation of BCP microdomain shifts to perpendicular orientation while it maintains its lateral order. We explore the effect of SS-LZA on the revolution of correlation length and retention of the grain size after post-annealing process. [Preview Abstract] |
Monday, March 13, 2017 1:27PM - 1:39PM |
B6.00010: Designing a Cubically Packed Contact Hole Template based on a simple Flat Plate Confinement of di-Block Copolymers: A Coarse-Grained Molecular Dynamics Study Shubham Pinge, Guanyang Lin, Durairaj Baskaran, Munirathna Padmanaban, Yong Joo Using a large-scale coarse-grained molecular dynamics framework, we investigate the interplay between confinement length and morphology formed by asymmetric di-block copolymers (BCPs) like PS-b-PMMA with 30 vol \% minor phase under various confinements by surfaces selectively biased towards the minor phase. In particular, we demonstrate that a length scale argument in a simple flat plate confinement can offer a predictive tool in designing the confined morphology formed in an intricate nano-lithographic template such as cubically packed pillars. Studies on a tight confinement of BCPs between two flat plates with separation of 17σ show the presence of a critical polymer chain length above which a transition from a 3-layers of minor domain to 2-layers is observed. Relaxing the confinement length to 42σ showed a transition from multi-layer morphology (>3) to a three layer morphology. These results are used to design a topographic template of cubically packed pillars forming cubically packed contact-hole patterns. The least and largest radial separation between adjacent pillars are kept at 17σ and 42σ, respectively. A direct correlation was observed in the number of minor domain layers of the maximum and minimum confinement dimensions with the 17σ and 42σ flat plate trials. [Preview Abstract] |
Monday, March 13, 2017 1:39PM - 1:51PM |
B6.00011: Parametric Conditions for the Directed Self Assembly of Block Copolymers using a Topographically Patterned Angled Substrate and Grafted Brush Nathan Rebello, Vaidyanathan Sethuraman, Gregory Blachut, Christopher Ellison, Grant Willson, Venkat Ganesan Single chain in mean field theory simulations is utilized to study the self-assembly of block copolymers (BCP) in thin films that are guided by a trapezoidal substrate and backfilled with random copolymers. The influence of the sidewall and substrate surface geometry guidelines on the self-assembly of BCPs are explored, and we identify the conditions that lead to the formation of perpendicular lamellar morphologies. We tune the chemical affinity of the substrate sidewall and its angle of inclination in order to obtain optimal conditions for self assembly, and compare these results with the traditional rectangular substrate. We find that when the substrate surface and sidewall are preferential to the same BCP component, lamellar formation occurs with high fidelity across all substrate angular modifications and becomes moderately favorable at a shorter substrate width with upper and lower angular extremities. On the other hand, when the sidewall and substrate surface are preferential to different blocks, high favorability is displayed with intermediate taper angles, and with shallower angles with short or large substrate widths. [Preview Abstract] |
Monday, March 13, 2017 1:51PM - 2:03PM |
B6.00012: Orienting Block Copolymer Thin Films via Entropy and Surface Plasma Treatment Rong-Ming Ho, Kai-Yuan Lu, Ting-Ya Lo, Ashkan Dehghan, An-Chang Shi, Georgopanos Prokopios, Apostolos Avgeropoulos Controlling the orientation of nanostructured thin films of block copolymers (BCPs) is essential for next generation lithography. In the thin-film state, how to achieve the perpendicular orientation of the nanostructured microdomains remains challenging due to the interfacial effects from the air and also the substrate, especially for the blocks with silicon containing segments which usually have different surface energies, favoring parallel microdomain orientation. Here, we show that entropic effect can be used to control the orientation of BCP thin films. Specifically, we used the architecture of star-block copolymers consisting of polystyrene (PS) and poly(dimethylsiloxane) (PDMS) blocks to regulate the entropic contribution to the self-assembled nanostructures. Moreover, we aim to achieve the formation of perpendicular orientation from the air surface via surface plasma treatment to neutralize the interfacial energy difference. By combining the architecture effect (entropy effect) on BCP self-assembly and the surface plasma treatment (enthalpy effect), well-defined perpendicular PDMS microdomains in the PS-b-PDMS thin film can be formed from the bottom of non-neutral substrate and the top of the thin film surface, giving great potential for lithographic applications. [Preview Abstract] |
Monday, March 13, 2017 2:03PM - 2:15PM |
B6.00013: Line and Dot Dual Nanopatterns by using Miktoarm Block Copolymer with Photocleavable Linker Chungryong Choi, Jichoel Park, K. L. Vincent Joseph, Jae Yong Lee, Seonghyeon Ahn, Jongheon Kwak, Jin Kon Kim Block copolymers capable of various nanodomains with size of 10$\sim$100 nm, for instance, spheres, cylinders, and lamellae, have received great attention because of their applicability to nanolithography. However, a nanodomain having a single shape (or size) is only achieved at a given block copolymer, because the volume fraction of one of the block in a block copolymer thermodynamically controls nanodomain. However, nano-patterns with multiple shapes and sizes are required for the next-generation of nanolithography. In this study, we synthesize a miktoarm block copolymer of which microdomains are transformed from cylinders to lamellae by UV irradiation. We fabricate dot and line patterns on a single substrate. [Preview Abstract] |
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