Directed Assembly of Block Copolymer Blends into Nonregular Device-Oriented Structures

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Directed Assembly of Block Copolymer Blends into
Nonregular Device-Oriented Structures

• Mark P. Stoykovich,1 Marcus Muller,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
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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

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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
NATURE Vol 437 29 September 2005
SCIENCE VOL. 276 18 APRIL 1997
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Molecular Diffusion Experiment

• CO Diffusion on Cu(111)
• Effects of CO-CO Interactions

40 K CO/Cu(111) 14s/image
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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.

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Block copolymer lithographythe 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 Inexpensiv
e, parallel, and scalable technique
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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 copolymerhomopolymer blend
  was spin-coated and annealed.(43-nm at 193-C for
  7 days )

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

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The endthanks!
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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