Enhancing the Potential of Block Copolymer Lithography with Polymer Self-Consistent Field Theory Simulations

Abstract

Metallic nanowires are useful for fabricating highly integrated nanoscale electrical, magnetic, and photonic devices. However, conventional methods based on bottom-up growth techniques are subject to concerns such as broad distributions in their dimension as well and difficulties in precise placement of the nanowires. These issues can be solved by the guided self-assembly of block copolymer thin films that can produce periodic arrays of monodisperse nanoscale features with excellent positional accuracy. Here, we report transfer of high-quality linear block copolymer patterns into various metals, Ti, W, Pt, Co, Ni, Ta, Au, and Al, to fabricate highly ordered nanowire arrays with widths down to 9 nm. This novel patterning process does not require specific film deposition techniques or etch-chemistries. We also describe their structural, magnetic, and electrical properties.KEYWORDS Block copolymer lithography, metallic nanowires, magnetic nanowires, metal gratings, polystyrenepolydimethylsiloxane F or the past decade, there has been enormous interest in inorganic one-dimensional nanostructures, 1,2 and due to their unprecedented properties in the sub-100-nm regime, various kinds of electric, optical, optoelectronic, and biological devices based on nanowires or nanotubes have been demonstrated. [1][2][3][4] Nanowires are often fabricated directly by vapor deposition processes such as the vaporliquid-solid technique, in which the dimensions, composition, and crystallographic orientation can be controlled by manipulating various synthetic parameters. 5 However, these methods are frequently accompanied by inherent issues such as broad distributions in the length and properties of synthesized nanowires, limitations on available compositions, and difficulties in placing the nanowires precisely onto a substrate. To position the nanowires into specific locations on substrates requires additional methods based on, for example, electric or fluidic fluids. 6,7 Alternatively, techniques based on planar processing can be used to fabricate nanowires directly on a substrate such that their composition, dimensions, position, and orientation can easily be controlled. However, these methods are limited by the resolution of the lithography system used to make them, and in the case of electron-beam lithography, the low throughput. It is therefore valuable to develop alternative methods for nanowire fabrication which can rapidly produce nanowires of arbitrary composition and narrow line width.Block copolymer (BCP) nanolithography is well suited for fabrication of nanoscale structures due to its fine resolution, cost-effectiveness, and scalability. BCPs consist of two or more incompatible polymer blocks that form a single polymeric chain and can undergo microphase separation to form periodic nanostructures. 8 The morphology and length scale of the self-assembled patterns usually range from ∼10 to 100 nm and can be controlled by the degree of polymerization and the volume fraction of the blocks. Selective removal of one block le...

Rectangular Symmetry Morphologies in a Topographically Templated Block Copolymer

“…The templates were chemically functionalized with a hydroxyl-terminated PS brush (3 kg mol -1 and 1 kg mol -1 for high and low molecular weight Simulation methods:Using the same methods as presented by Mickiewicz et.al [26], threedimensional SCFT simulations were done to compare the equilibrium morphologies found in the experiment with those in the simulations. The simulations were used to explore a wider parameter space than allowed in the experiments in order to predict the commensurability conditions for the various morphologies.…”

Hierarchical nanostructures of diblock copolymer thin films directed by a saw-toothed substrate

“…14 More importantly, due to the advantages afforded by these materials, such as self-assembly, tunability of the pattern geometry and dimensions, and low cost, they can be used as templates and scaffolds to fabricate ultrafiltration membranes, 15,16 nanolithographic templates and scaffolds, [17][18][19] energy conversion and high-density magnetic storage media, 20,21 nanodots, 22 nanowires, 23,24 semiconductors, 25 polarizers and photonic band gap materials with well-ordered arrays of nanoscopic structures. 50 Consequently, some researchers turn their sights to the related simulation work inch by inch, and there is a wide variety of approaches to choose, such as Monte Carlo (MC), 51-53 dissipative particle dynamics (DPD), 54,55 dynamic density functional theory (DDFT), 24 brownian dynamics (BD), 54 and cell dynamics (CD). [28][29][30][31][32] Russell and co-workers investigated the unconventional morphologies of symmetric, diblock copolymers as a function of film thickness, 28 and interfacial interactions as early as 1990s.…”

Design rules for self-assembled block copolymer patterns using tiled templates

“…Furthermore, as shown in Fig. 4g,h, self-consistent field theory (SCFT) simulations [29][30][31][32][33] were used to calculate the block copolymer morphology resulting from the input templates of Fig. 4a,b.…”

“…The SCFT simulations used here use the same equations and computational methods as presented in the supporting information of previous work by Mickiewicz et al 31 In the SCFT simulations, the system was modelled by using hard-wall field boundary conditions that represented the topographic posts used in experiment and PDMS attractive potentials that represented the surface-air interface and brush layer. The system was discretized onto an N x -by-N y -by-N z grid with a course graining of nine grid points assigned to a distance of L 0 .…”