Bulletin of the American Physical Society
2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009; Pittsburgh, Pennsylvania
Session J19: Block Copolymer Thin Films II |
Hide Abstracts |
Sponsoring Units: DPOLY Chair: Kevin Cavicchi, University of Akron Room: 320 |
Tuesday, March 17, 2009 11:15AM - 11:27AM |
J19.00001: Self-assembled surface patterns from organometallic-containing triblock terpolymers Vivian Chuang, Caroline Ross, Jessica Gwyther, Ian Manners Block copolymers are useful in nanotechnology because they can self-assemble to form periodic nanoscale structures. Here, we demonstrate the formation of hollow ring arrays with a period of 54 nm from a core-shell cylindrical-morphology poly(styrene-b-ferrocenyldimethylsilane-b-2-vinyl pyridine) (PS-b-PFS-b-P2VP) triblock terpolymer thin film. By spin-coating and solvent annealing, thin films of the polymer were self-assembled into arrays of core-shell structures oriented perpendicular to the top surface of the film. Various chemically modified substrates were employed to investigate the effects of interfacial interaction between the substrate and the film, as well as the effects of solvent annealing, on the film morphology. Results will be compared with those obtained from a poly(butadiene-b-styrene-b-methyl methacrylate) triblock terpolymer [1]. The PS core and P2VP matrix blocks were partly removed simultaneously using oxygen plasma, and the remaining PFS ring pattern was successfully transferred into a PS layer by imprinting. \\[3pt] [1] Chuang et al., ACS Nano, 2008, 2, 2007. [Preview Abstract] |
Tuesday, March 17, 2009 11:27AM - 11:39AM |
J19.00002: Improvement of Extraction Efficiency of LED with Surface Relief Nanotructure Fabricated by Self-Assembled Block Copolymer Pattern Ryota Kitagawa, Akira Fujimoto, Koji Asakawa A surface relief nanostructure was fabricated on the emission surface of light-emitting diodes (LEDs) using a self-assembled diblock copolymer pattern. The pattern of the nanostructure possesses moderate short-range order with slightly deviation in size and spacing, which is different from conventional extraction surface structures, such as photonic crystal and randomly textured surface. The dot pattern of a self-assembled polystyrene -polymethylmethacrylate diblock copolymer (PS-b-PMMA) was used as an etched mask. An average dot spacing was controlled by changing blend ratio of PS-b-PMMA, homo (h-) PS, and h-PMMA in a polymer solution. In the photoluminescence (PL) measurement, the light extraction efficiency of the nanostructure exceeded over twice, compared with a flat surface, by optimizing the average spacing of the nanostructure. It was also revealed that the nanostructure showed more than 10{\%} higher extraction efficiency than the highly ordered nanostructure fabricated by a self-assembled nanosphere pattern. These results can be interpreted as a contribution of structural fluctuation in the nanostructure for enhancement of extraction efficiency. [Preview Abstract] |
Tuesday, March 17, 2009 11:39AM - 11:51AM |
J19.00003: Self-Assembling Block Copolymer Resist Mixtures towards Lithographic Resists for Sub-10 nm Features Curran Chandler, Vikram Daga, James Watkins Significant improvements in 193 nm photolithography have enabled the extension of device feature sizes beyond the 45 nm and 32 nm nodes, yet uncertainty lies beyond 22 nm features as no single replacement has emerged. Here we show that low molecular weight, nonionic block copolymer surfactant blends are capable of self-assembling into highly ordered domains with feature sizes on the order of 5 nm. These surfactants, most of which lack the required $\chi N$ for microphase separation on their own, exhibit strong segregation and long-range order upon addition of a component capable of multi-point hydrogen bonding that is specific for one of the blocks in the copolymer. This has been demonstrated by our SAXS data for several Pluronic (PEO-$b$-PPO-$b$-PEO) and Brij (PEO-$b$-[CH$_{2}$]$_{n}$CH$_{3})$ surfactants of various molecular weights and PEO volume fractions. Furthermore, we employ these highly-ordered systems as thin film, nanolithographic etch masks for the transfer of sub-10 nm patterns into silicon-based substrates. Small molecule, hydrogen bonding additives containing aromatic or silsesquioxane structure are also used to tune etch contrast between the blocks which is important for reducing line edge roughness (LER) of such small features. [Preview Abstract] |
Tuesday, March 17, 2009 11:51AM - 12:03PM |
J19.00004: Directed assembly of block copolymers on chemically nanopatterned substrates: enabling science for ultra high resolution lithography Paul Nealey Self-assembling materials based on block copolymers spontaneously form structures with well-defined dimensions and shapes at length scales of interest in nanotechnology. Unfortunately the thermodynamic driving forces for self-assembly are small and low-energy defects can get easily trapped. At issue is the extent of direction or guidance required to meet criteria related to perfection and registration for use of such materials in nanofabrication. Through fundamental understanding of the physics, chemistry, and surface and interfacial phenomena associated with equilibrating block copolymer films in the presence of chemically nanopatterned substrates, we demonstrate how block copolymers may be integrated into and advance the performance of the lithographic process. The technological importance of this approach is discussed with respect to patterned media and the fabrication of integrated circuits. [Preview Abstract] |
Tuesday, March 17, 2009 12:03PM - 12:15PM |
J19.00005: Conditions for the directed assembly of thick block copolymer films on chemically nano-patterned surfaces Adam M. Welander, Paul F. Nealey The extent to which a lamellae forming block copolymer (bulk period, $L_{0}$ = 48 nm) can be directed to assemble on chemically nano-patterned striped surfaces (period $L_{S})$ with domains registered to and extending vertically away from the underlying pattern with few defects was studied as a function of film thickness, commensurability between $L_{S}$ and $L_{0}$, and temperature. The thickness through which low defect assembly could be achieved increased as $L_{S}$ and $L_{0}$ became more commensurate and as the temperature increased from 190 \r{ }C to 230 \r{ }C. Under certain conditions ($L_{S} \quad \approx \quad L_{0}$, 230 \r{ }C), block copolymer films approaching 750 nm (aspect ratio $\approx $ 30) in thickness still exhibited low levels of defectivity. These results were interpreted in terms of a phenomenological model and minimization of free energy including surface and interfacial energies and chain configuration entropy. [Preview Abstract] |
Tuesday, March 17, 2009 12:15PM - 12:27PM |
J19.00006: Directed self-assembly of diblock copolymer thin films on chemically-patterned substrates for defect-free nano-patterning Mikihito Takenaka, Yasuhiko Tada, Satoshi Akasaka, Synsuke Aburaya, Hiroshi Yoshida, Hirokazu Hasegawa, Elizabeth Dobisz, Dan Kercher We demonstrate that Polystyrene-\textit{block}-poly(methyl methacrylate) (PS-$b$-PMMA) can self-assemble in a well-aligned, long-range ordered nano-pattern over arbitrarily large areas, commensurate with chemically pre-patterned templates prepared by electron beam (EB) lithography. We also demonstrate that the self-assembly process can interpolate points in between the EB generated pattern, thus multiplying the pattern density. Moreover, we show the results of the investigation about the time-evolution of the self-assembled structure during annealing process. [Preview Abstract] |
Tuesday, March 17, 2009 12:27PM - 12:39PM |
J19.00007: Lamellar and Non-bulk like Morphologies in Thin Films of Block Copolymer on Chemical Nanopatterned Surfaces Guoliang Liu, Francois Detcheverry, Juan J. de Pablo, Paul F. Nealey Thin films of symmetric PS-b-PMMA (bulk lamellae period L$_{o})$ were equilibrated on substrates patterned with periodic stripes such that the adjacent stripes are preferentially wet by the two blocks of the copolymer. The morphology of the films was quantified as a function of the following pattern characteristics: the pattern period, L$_{s}$, where L$_{s}=\delta $ L$_{o}$, 1 $\le \quad \delta \quad \le $ 3, the width of the PMMA wetting strips, W, and the interfacial energies between the blocks and the patterned stripes, $\Lambda _{i, j}$. Under different boundary conditions we can 1) direct the assembly of lamellae perpendicular to the substrate and ordered in linear arrays so as to increase the density of features of the chemical pattern, or 2) obtain a number of stable non-bulk like structures including asymmetric lamellae, mixed orientated lamellae, dots, and check-board structures. The experimental results are compared to a phase-diagram predicted from molecular simulations. [Preview Abstract] |
Tuesday, March 17, 2009 12:39PM - 12:51PM |
J19.00008: Self-confinement in Block Copolymer Thin Films Induced by Chemical Patterns Made from Electro-oxidation Nanolithorgraphy Ji Xu, Antonio Checco, Benjamin Ocko, Soojin Park, Shiliu Wang, Thomas Russell The effect of confinement from chemical patterns on the self-assembly of block copolymer and related wetting physics has been studied. A variety of geometries designed in a mesh fashion were chemically patterned on OTS modified silicon wafers by electro-oxidation nanolithography. Thin films of a cylinder-forming PS-b-PEO were spin coated onto these patterned substrates. Thermal annealing of these films showed that the films were pinned on the patterned regions, due to the strong interaction between PEO block and carboxylic acid group on patterned surface while, over the non-patterned areas, dewetting was suppressed. The non-favorable interactions of both blocks with the substrate in the non-patterned areas caused the cylindrical microdomains to orient normal to the surface, being confined geometrically by the patterned regions. Defect-free, hexagonally packed cylindrical microdomains that conformed to hexagonal pattern written onto the surface were obtained. Point defects arose in the hexagonal packing of the microdomains when the dimensions or shape of the pattern were not commensurate with the natural packing of the copolymers. [Preview Abstract] |
Tuesday, March 17, 2009 12:51PM - 1:03PM |
J19.00009: Time-Resolved SAXS Characterization of Block Copolymer Blends on Chemically Nanopatterned Surfaces Karl Stuen, Paul Nealey, Dillip Satapathy, Kim Nygard, Harun Solak The directed assembly of block copolymer/homopolymer ternary blend thin films on chemically nanopatterned substrates was investigated with \textit{in situ} transmission SAXS. A ternary blend was used to match the block copolymer period with the period of a chemical pattern fabricated by x-ray interference lithography. The domain assembly in a 24-nm-thick block copolymer blend film on the chemical nanopattern was monitored with SAXS in real-time as a sample was heated from 100 to 240 \r{ }C at about 20 \r{ }C per minute. The strongest diffraction from the sample was detected after just 4.5 minutes of annealing (maximum temperature $\sim $ 190 \r{ }C). Complementary results were obtained from top-down SEM images of films that were quenched to room temperature after various times during the temperature ramp. The SEM images revealed transient structures in the annealing process that may relate to the non-uniform distribution of homopolymer in the direction perpendicular to the substrate. The results were compared to previously reported Monte Carlo molecular simulations to better understand the three-dimensional structures that form during the annealing process. [Preview Abstract] |
Tuesday, March 17, 2009 1:03PM - 1:15PM |
J19.00010: Imaging Layer Effect on Density Multiplication in the Directed Assembly of Block Copolymer Thin Films Huiman Kang, Eungnak Han, Padma Gopalan, Paul Nealey Recently, we discovered the assembly block copolymer thin films on chemically nanopatterned surfaces markedly improve both the quality and resolution of the lithographic process. In comparing the assembled block copolymer structures to the lithographically defined chemical pattern, the density of features is increased by a factor of four and the dimensional uniformity is vastly improved, even on the strongly preferential background imaging layer. Here, we investigate the effect of the interactions between the patterned imaging layer and the components of the block copolymer, especially polystyrene-\textit{block}-poly(methyl methacrylate) (PS-$b$-PMMA), by controlling the fraction of styrene in the imaging layer of chemically patterned surfaces from preferential to non-preferential to the polymer. [Preview Abstract] |
Tuesday, March 17, 2009 1:15PM - 1:27PM |
J19.00011: Molecular Transfer Printing Using Block Copolymers Shengxiang Ji, Chi-Chun Liu, Guoliang Liu, Paul Nealey We report a new parallel patterning technique, molecular transfer printing (MTP), for replicating geometrically complex patterns over macroscopic areas with sub-15 nm feature dimensions, and the ability to replicate the same pattern multiple times. In MTP, inks are mixed with block copolymers (BCPs) and deposited as films on a substrate. The inks are compatible with only one block of the BCP, and sequestered into domains of nanometer scale dimensions after microphase separation. A second substrate is then placed in contact with the surface of the film. By designing the inks to react, adsorb, or otherwise interact with the second substrate, inks are transferred to the second substrate in the exact pattern of domains present at the surface of the ``master'' BCP film. Here we demonstrate high degrees of perfection on both line and dot patterns. We also show that 1) the master template can be regenerated, 2) the resultant replica can be used to direct the assembly of BCPs and as a daughter master for MTP, and 3) the master and daughter templates can be reused tens of times. [Preview Abstract] |
Tuesday, March 17, 2009 1:27PM - 1:39PM |
J19.00012: Pattern interpolation in thin films of lamellar, symmetric copolymers on nano-patterned substrates Francois Detcheverry, Umang Nagpal, Guoliang Liu, Paul Nealey, Juan de Pablo A molecular model of block copolymer systems is used to conduct a systematic study of the morphologies that arise when thin films of symmetric, lamellar forming block copolymer materials are deposited on nanopatterned surfaces. Over 500 distinct cases are considered. It is found that, in general, three distinct morphologies can arise depending on the strength of the substrate-polymer interactions, the film thickness, and the period of the substrate pattern. The relative stability of those morphologies is determined by direct calculation of the free energy differences. The dynamic propensity of those morphologies to emerge is examined by careful analysis of simulated trajectories. The results of this systematic study are used to interpret recent experimental data for films of polystyrene-PMMA copolymers on chemically nanopatterned surfaces. [Preview Abstract] |
Tuesday, March 17, 2009 1:39PM - 1:51PM |
J19.00013: Thin Films of Polydimethylsiloxane-Containing Block Copolymers Maurice Wadley, Kevin Cavicchi The self-assembly of block copolymers into ordered nanostructures such as spheres, cylinders, and lamellae in the range of 10-100 nm makes them interesting materials for patterning surfaces. Thin films of poly(dimethylsiloxane) (PDMS) containing block copolymers are attractive for patterning due to their high oxygen etch resistance compared to other polymers. The main disadvantage of these polymers for patterning is the low surface tension of PDMS. This causes the preferential migration of PDMS to the air/film interface driving the formation of domains parallel to the interface and surface wetting layers. In this work a series of AB block copolymers containing PDMS have been prepared via RAFT polymerization where the surface tension of the opposing block was varied. Using a macro chain transfer approach, it is possible to isolate the effect of changing the opposing block while keeping the PDMS the same in each different block copolymer. The effect of changing the surface tension mismatch between the blocks on the thin film morphology will be discussed. [Preview Abstract] |
Tuesday, March 17, 2009 1:51PM - 2:03PM |
J19.00014: Interfacial Bending of Lamellar Microdomains of Block Copolymers Sang-Min Park, Meng Dong, Charles Rettner, Qiang Wang, Ho-Cheol Kim We report our investigation on the interfacial bending property of the lamellar microdomains using a symmetric block copolymer of poly(styrene-b-methyl methacrylate) (PS-b-PMMA) deposited on a neutral surface. The degree of interfacial bending of lamellae on surface was controlled by varying the angle of elbow-like topographic guiding patterns prepared by E-beam lithography. The characteristic parameters of lamellae bending including the critical angles of elbow-like patterns which give maximum interfacial bending of lamellae, the lamellae tilting angle at sidewall were determined for both single and paired guiding patterns. The behavior of a block copolymer containing hybrid system, a mixture of poly(styrene-b-ethylene oxide) and organosilicate, was investigated as well. A computational calculation on the lamellae bending which provides more insights on the free energy and interfacial characteristics will be discussed as well. [Preview Abstract] |
Tuesday, March 17, 2009 2:03PM - 2:15PM |
J19.00015: Observation of Surface Corrugation-Induced Alignment of Lamellar Microdomains in PS-b-PMMA Thin Films. Ho-Cheol Kim, Sang-Min Park, Charles Rettner, Brian Berry, Elizabeth Dobisz Previously we reported the alignment of lamellar microdomains of a block copolymer containing hybrid on a corrugated surface, which provides self-assembled crossbar nanostructures. The alignment of lamellae of the hybrid system is believed due to the anisotropic bending perperty of lamellae. Attempts to similarly align the lamellae of PS-b-PMMA using the same length scales of surface corrugation were not successful. In this study, we investigated the alignment of lamellar microdomains of PS-b-PMMA using even broader ranges of length scales of the surface corrugation. Within specific ranges of roughness scales, we observed that the lamllar microdomains of PS-b-PMMA align perpendicular to the direction of surface corrugation. The effect of relative scales of periodicity and film thickness of PS-b-PMMA to those of surface corrugation on the alignment of lamellae is discussed in this paper. [Preview Abstract] |
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