Directed Assembly of Block Copolymer Blends into Nonregular Device-Oriented Structures Mark P. Stoykovich,1 Marcus Mu¨ller,2 Sang Ouk Kim,3 Harun H. Solak,4 Erik W. Edwards,1 Juan J. de Pablo,1 Paul F. Nealey Science 308, 1442 (2005); By Erick Ulin-Avila

Outline Engineering Atomic and Molecular nanostructures at surfaces Block Copolymer Lithography Chemically nanopatterned surfaces Assembly of films of ternary block copolymer-homopolymer blends Results Conclusions

Engineering Atomic and Molecular nanostructures at surfaces Surface self-ordering processes can be tuned in metallic, semiconducting and molecular systems. Any growth scenario is governed by competition between kinetics and thermodynamics Transport mechanism involves random hopping processes at the substrate. –This Diffusion is thermally activated and obeys an Arrehnius law (Holds for atoms as well as rigid organic molecules) Type of growth is determined by D/F D is diffusion rate F is deposition flux SCIENCE VOL APRIL 1997 NATURE Vol September 2005

Molecular Diffusion Experiment CO Diffusion on Cu(111): Effects of CO-CO Interactions ‘Isolated’ Molecule ‘Embedded’ Molecule ‘Molecular Cluster’ 40 K CO/Cu(111) 14s/image

Objective Directing the assembly of blends of block copolymers and homopolymers on chemically nanopatterned substrates, The ability to pattern nonregular structures using selfassembling materials creates new opportunities for nanoscale manufacturing.

Block copolymer lithography the use of these ordered structures in the form of thin films as patterning templates. Diblock copolymers ( two chemically connected polymer chains ) –spontaneously form ordered nanostructures, including spheres, cylinders, and lamellae, Shape and dimensions depend on the molecular weight and composition of the polymer Inexpensive, parallel, and scalable technique

Chemically nanopatterned surfaces PS brush (A) A photoresist was spin-coated on a PS brush that was grafted to a Si substrate (B) patterned by using advanced lithography (period LS). (C) Oxygen plasma etching –chemically modify the exposed regions of the PS brush (chemical surface pattern). (D) Photoresist removed by solvent (E) a ternary block copolymer–homopolymer blend was spin-coated and annealed.( 43-nm at 193-C for 7 days )

Adequate thickness to act as templates for patterning through selective etching or deposition processes Top-down SEM images

(A) Schematic of the increased lamellar period at the corners of the bends. (B), the red (PS) and blue (PMMA) rich domains. (C) the total homopolymer concentration obtained from SCMF simulations for LS = LB = 70 nm show segregation of homopolymers to the 90 degrees bend corners In (C), the periodic red areas are enriched alternatively in PS and PMMA homopolymers, whereas the blue stripes represent the domain interfaces that are depleted of homopolymers. (D) Averaged total homopolymer concentration as a function of the distance from the line of corners for 45- and 90- bends. Upon increasing the bend angle, we observed an increased segregation of the homopolymers to the corners. The differences in domain structure and the formation of defects at the corners depend on the bend angle and the corner-to-corner lamellar period, LC

Conclusions Polymer substrate Interfacial energy enables –the directed assembly of block copolymer domains into structures that do not exist in the bulk. High densities of nonregular shaped structures –by optimizing blend compositions, polymer chemistry, and interfacial interactions. It may be scaled to dimensions of 10 nm or below with precise control over feature size and shape.

The end thanks!

Additional slide The ternary blend consisted of –60 weight % (wt. %) symmetric polystyrene-block -poly(methylmethacrylate) (PS-b-PMMA, 104 kg/mol,bulk lamellar period of 49 nm), –20 wt. % polystyrene homopolymer (PS, 40 kg/mol), and –20 wt. % poly(methylmethacrylate) homopolymer (PMMA, 41 kg/mol). Single chain in mean field (SCMF) simulations, a particle-based self-consistent field method