Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session X38: Block Copolymer Thin Films: Directed AssemblyFocus
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Sponsoring Units: DPOLY Chair: Ryan Hayward, U Mass Amherst Room: 341 |
Friday, March 18, 2016 8:00AM - 8:12AM |
X38.00001: Out-of-plane Block Copolymer Microdomains in High Aspect-Ratio Templates Karim Gadelrab, Wubin Bai, Alfredo Alexander-Katz, Caroline Ross The use of directed self-assembly DSA of block copolymers BCP proved to be a power approach for nanoscale fabrication. It combines the ability of BCPs to self-assemble into nanoscale features with the use of lithographic tools to create controlled long range order. In addition, BCP with highly incompatible blocks (high Flory-Huggins interaction parameter ($\chi ))$ offer improvement in resolution, and line edge fluctuations of the self-assembled patterns. Unfortunately, high-$\chi $ BCPs usually exhibit large differences in surface affinity between the two blocks, leading to the formation of a surface layer of the lower surface energy block and favoring in-plane orientation of lamellae or cylindrical microdomains. Here, we explore the conditions under which a high $\chi $ BCP creates an out-of-plane lamellar structure using functionalized high aspect ratio trenches with preferential walls. We employ the free energy analysis of self-consistent field theory SCFT to identify whether an in-plane or out-of-plane structure is stable for a particular trench width. In addition, we employ the single mode expansion of Ginzburg-Landau free energy expression in the weak segregation limit to analytically construct a phase diagram of the in-plane and out-of-plane lamellae as a function of aspect ratio and surface attraction strength. It is found that achieving an out of plane lamellar structure necessitates a coupling between aspect ratio and surface functionality. In particular, strong side wall attraction results in out-of-plane lamellae when the trench aspect ratio is greater than unity. The results are validated for a lamellar forming polystyrene-block-polydimethylsiloxane (PS-b-PDMS) within trenches made using interference lithography. [Preview Abstract] |
Friday, March 18, 2016 8:12AM - 8:24AM |
X38.00002: Characterizing the interfaces of block copolymers with high $\chi $ Daniel Sunday, Michael Maher, Gregory Blachut, Yusuke Asano, Summer Tein, C. Grant Willson, Christopher Ellison, R. Joseph Kline In order for block copolymer (BCP) directed self-assembly (DSA) to be able to pattern features below 10 nm there must be materials which can spontaneously assembly at the required length scales. For the smallest features this will require phase separation where the total chain lengths are under 50 monomer units, demanding very large interaction parameters ($\chi )$ to have an order-disorder transition. One of the key parameters for DSA will be the interfacial width between the blocks, which is expected to be correlated to the interaction parameter and will help determine the line edge roughness (LER). We have used resonant soft X-ray reflectivity to investigate a series of high $\chi $ BCPs with different compositions and molecular weights to determine the interfacial width and degree of phase separation. We use these results to estimate the value of $\chi $ and determine relationships between $\chi $ and the interfacial mixing. [Preview Abstract] |
Friday, March 18, 2016 8:24AM - 8:36AM |
X38.00003: Reducing Line Edge Roughness of PS-b-PMMA pattern by inducing hydrogen bonding at the interface of the block copolymer microdomains Kyu Seong Lee, Sung Hyun Han, Sangshin Jang, Jicheol Park, Jongheon Kwak, Jin Kon Kim Sharp interface between two blocks in block copolymer nano pattern is one of the important issues in industrial applications to nano-patterning. We utilized hydrogen bonding between N-(4-aminomethyl-benzyl)-4-hydroxymethyl-bezamide (BA) and urea (U) at the interface of polystyrene-\textit{block}-poly(methyl methacrylate) copolymer (PS-PMMA). For this purpose, we first synthesized PS by ATRP, then the end group was converted to amino group. Next, it was reacted with BA, followed by reaction with 4-pentynoic acid, resulting in alkyne-terminated group (PS-U-BA-alkyne). Also, azide-terminated PMMA was prepared by anionic polymerization followed by end functionalization. Finally, by the azide-alkyne click reaction between PS-U-BA-alkyne and PMMA-azide, PS-U-BA-PMMA was synthesized. We prepared vertical oriented lamellar nanopatterns on pre-patterned wafers and investigated line edge roughness (LER) after removing PMMA block by dry etching process. We found that LER was reduced compared with PS-PMMA without hydrogen bonding. [Preview Abstract] |
Friday, March 18, 2016 8:36AM - 9:12AM |
X38.00004: Photothermal assembly of block copolymers Invited Speaker: Kevin Yager This talk will discuss recent work on the use of photothermal methods to control the ordering of block copolymer thin films. Photothermal methods can be used to generate temperature gradients and shear fields, which have a strong influence on block copolymer assembly. For example, assembly can be accelerated, and morphology can be aligned. These methods also highlight the non-equilibrium, pathway-dependence of self-assembly. We present examples of exploiting these effects to control alignment, and to iteratively construct arbitrary lattice symmetries. [Preview Abstract] |
Friday, March 18, 2016 9:12AM - 9:24AM |
X38.00005: Numerical Simulations of Directed Self-Assembly in Diblock Copolymer Films using Zone Annealing and Templating Techniques Joseph Hill, Paul Millett Bulk fabrication of surface patterns with sub-20 nm feature sizes is tremendously desirable for many existing and emerging technologies. Directed self-assembly (DSA) of block copolymers (BCPs) has been a recently demonstrated approach to achieve such feature resolution over large-scale areas with minimal defect populations. Much work however remains to understand and optimize DSA methods in order to move this field forward. This talk will present results from large-scale numerical simulations of zone annealing and topological template processing of BCP films to achieve long-range orientational order. The simulations utilize a Time-Dependent Ginzburg-Landau model and parallel processing to elucidate relationships between thermal gradient velocities and domain orientations as well as defect densities. Additional simulations have been conducted to study to what degree orientational order can be further enhanced with both zone annealing and topological templating techniques. It is found that these two DSA methods do synergistically enhance long-range order with a particular relationship between thermal gradient velocity and topological template spacing. [Preview Abstract] |
Friday, March 18, 2016 9:24AM - 9:36AM |
X38.00006: Rapid microwave annealing for perpendicular oriented cylinders in PS-$b$-PMMA thin films Zhe Qiang, Kevin Cavicchi, Bryan Vogt Self-assembly of block copolymer (BCP) has been extensively studied for decades due to their wide range of potential applications such as lithography. Direct microwave annealing provides rapid ordering kinetics. However, the knowledge regarding the structural and orientation evolution of morphology during microwave annealing without solvents remains sparse. Herein, we report on how microwave-annealing conditions impact the morphology developed in cylinder forming PS-b-PMMA films on unmodified silicon wafers. The fraction of perpendicular cylinders developed during microwave annealing is primarily determined by temperature ramp from microwave heating itself. The heating of the substrate during microwave annealing is varied from 0.5 \textdegree C/s to 2.8 \textdegree C/s by two factors: (1) the microwave output energy and (2) the local heating position of BCP film in the microwave reaction vessel. A maximum in the fraction of perpendicular cylinders (97 {\%}) occurs at 1.83 \textdegree C/s and appears independent of the microwave power used. This work demonstrates the importance of controlling conditions of microwave annealing in the morphology developed. [Preview Abstract] |
Friday, March 18, 2016 9:36AM - 9:48AM |
X38.00007: Directed Self-assembly of Block Copolymer with Sub-15 nm Domain Spacing Using Nanoimprinted Photoresist Templates Zhiwei Sun, Zhenbin Chen, Wenxu Zhang, E. Bryan Coughlin, Shuaigang Xiao, Thomas Russell There has been increasing interest in preparing block copolymer thin films with ultra-small domain spacings for use as etching masks for ultra-high resolution nanolithography. One method to prepare block copolymer materials with small feature sizes is salt doping, increasing the Flory-Huggins interaction and allowing microphase separation to be maintained at lower molecular weights. Lamellae-forming P2VP-$b$-PS-$b$-P2VP block copolymer with various molecular weight was synthesized using RAFT polymerization with a dual functional chain transfer agent. Copper (II) Chloride or Gold (III) chloride was found to be selectively associated with P2VP block and increase the unfavorable interactions between PS and P2VP blocks, driving the disordered block copolymer into the ordered state. A 14 nm lamellar spacing of P2VP-$b$-PS-$b$-P2VP thin film was prepared using copper (II) Chloride doping after acetone vapor annealing on neutral brushes. Metallic nano-wire arrays were prepared after selective infiltration of platinum salt into the P2VP domain and oxygen plasma treatment. The directed self-assembly of salt doped P2VP-$b$-PS-$b$-P2VP triblock copolymer having long-rang lateral order on nanoimprinted photoresist templates with shallow trenches was also studied. [Preview Abstract] |
Friday, March 18, 2016 9:48AM - 10:00AM |
X38.00008: Exploring the Use of Additives to Optimize the Directed Self-Assembly of Block Copolymers via Self-Consistent Field Theory Simulations Adam Hannon, Daniel Sunday, R. Joseph Kline The directed self-assembly (DSA) of block copolymers (BCPs) is being investigated for the fabrication of next generation memory and integrated circuit technologies. Much progress has been made showing how these materials can be processed to produce a variety of transferable patterned morphologies that meet the requirements for fabricating integrated circuit geometries. One lingering issue in using these materials to produce sub-10 nm structures is finding new BCPs with a high enough $\chi $Flory-Huggins interaction parameter to create small resolution features with low interfacial widths that are also easily processable. An alternative approach to synthesizing new materials is to instead blend the BCP with additives that strongly interacts with one of the blocks. Here we present findings on how the addition of a hydrogen bonding homopolymer affects the overall effective $\chi $, the periodicity, and the morphology of the BCP. Self-consistent field theory simulations are used to explore how the relative $\chi $ values and degrees of polymerization between the BCP and homopolymer affect these parameters and suggest optimal blending conditions. Results are compared with experimental X-ray and neutron scattering studies of a polystyrene-$b$-poly(methyl methacrylate)/poly(vinyl phenol) blend. [Preview Abstract] |
Friday, March 18, 2016 10:00AM - 10:12AM |
X38.00009: Controlled Ordering of Long-range Perpendicular Lamellae by Block Copolymer Self-assembly Du Yeol Ryu, Kyunginn Kim, Sungmin Park, Yeongsik Kim We introduce a simple approach to fabricating highly stable, perpendicularly oriented lamellae through the self-assembly of high-molecular-weight polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA). The desired morphology was achieved over a narrow annealing period (5 ~ 10 min) under solvent vapor, since the SVA process need to terminate immediately before the saturated BCP films begin to dewet the substrate. This narrow processing period impeded practical applications to continuous industrial processes. A controlled SVA process at a selected temperature gap was found to show the excellent long-term stability, at which highly ordered line-arrays of perpendicularly oriented lamellae were confined to topographic line patterns. [Preview Abstract] |
Friday, March 18, 2016 10:12AM - 10:24AM |
X38.00010: Using chemically patterned substrates to suppress thermal placement errors in the directed self-assembly of block copolymer multi-cylinder linear arrays Corinne Carpenter, Kris Delaney, Glenn Fredrickson Directed self assembly (DSA) of block copolymers is a promising alternative approach for \textasciitilde 10nm microelectronics patterning, both for feature-size reduction and rectification. One prototypical application of DSA is the use of vertical interconnect access (VIA) cylinders for fabricating conducting channels between circuit layers. Typically a compromise exists between the fidelity and low defect density obtained by using a small number of cylinders per pre-pattern guide and the objective to further increase feature density. In particular for 1D linear arrays of multiple VIAs in a single prepattern, prior experimental and theoretical work has demonstrated that thermal fluctuations in larger arrays cause cylinder placement to vary widely around the equilibrium positions in a manner analogous to the collective excitations in a simple 1D coupled oscillator model (Landau-Peierls instability). In the present work, we assess the efficacy of using chemically patterned substrates to suppress the thermal placement errors using both a phenomenological oscillator model and full field theoretic simulations. [Preview Abstract] |
Friday, March 18, 2016 10:24AM - 10:36AM |
X38.00011: Minimal Topographic Patterns for Guiding Hexagonal Arrays of Cylindrical Microdomains in Block Copolymer Thin Films Jaewon Choi, Yinyong Li, Ilja Gunkel, Zhiwei Sun, Feng Liu, Kenneth Carter, Thomas Russell Topographically patterned substrates have been widely studied to control the lateral order of block copolymer (BCP) microdomains in thin films. However, most studies have been focused on deep topographic patterns, where a confinement depth is comparable to or larger than domain spacing of BCP, limiting the grain size of BCP due to the confinement width. Also, the investigation of BCP microdomains using grazing incidence small angle X-ray scattering (GISAXS) is limited because the scattering peaks from BCP are generally hidden by the strong scattering peaks from the deep topographic pattern. Here, we present the use of minimal topographic patterns for guiding hexagonal arrays of cylindrical microdomains of poly(styrene-b-ethylene oxide) (PS-b-PEO) thin films. Since the confinement depth of the minimal pattern is much smaller than domain spacing of BCP, this enables cylindrical microdomains to overcome the confined width, generating macroscopic ordered hexagonal arrays. In the GISAXS experiment, we confirmed that the (10) plane of hexagonal arrays was parallel to the direction of the trench by rotating the sample stage and changing the incident angle of X-ray. [Preview Abstract] |
Friday, March 18, 2016 10:36AM - 10:48AM |
X38.00012: Polarized Resonant Critical Dimension Small Angle X-Ray Scattering for the Characterization of Polymer Patterns Christopher Liman, Daniel Sunday, Hyun Wook Ro, Lee Richter, Adam Hannon, R. Joseph Kline Critical dimension small angle X-ray scattering (CDSAXS) is a recently developed technique that enables the characterization of the three-dimensional shape of periodic patterns, such as directed self-assembled (DSA) block copolymer (BCP) lamellae thin films. Information about the polymer patterns is extracted by fitting simulated scattering patterns to the experimental ones using an inverse iterative algorithm. Conducting CDSAXS at resonant energies near the carbon or nitrogen edge can enhance the strength of the scattering, but also causes the scattering to be influenced by any anisotropic orientation of the polymer chains. In this work, to assess the degree to which the scattering may be influenced by orientation, we simulate polarized resonant CDSAXS patterns for BCP lamellae with varying degrees of orientation, as well as orientation as a function of location within the lamellae, for different polarizations of the incident X-rays. Also, to assess the influence of a higher degree of orientation, we use capillary force lithography to pattern nanogratings of two semiconducting homopolymers which are known to orient strongly. We characterize these nanogratings, which have similar length scales to DSA BCP lamellae, with polarized resonant CDSAXS and spectroscopic ellipsometry. Finally, we fit simulated CDSAXS and ellipsometric data to the experimental data to obtain information about the shape and the orientation of the nanogratings. [Preview Abstract] |
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