block copolymer micelle nanolithography roman glass, martin moller and joachim p spatz university of...
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Block Copolymer Micelle NanolithographyRoman Glass, Martin Moller and Joachim P SpatzUniversity of HeidelbergIOP Nanotechnology (2003)Erika Parra
EE235
4/18/2007
Motivation
Market Trends Small features
Sub-10nm clusters deposited Patterns 50nm to 250nm and greater
Lower cost of tedious fabrication processes for conventional lithography
Increase throughput (from e-beam) – parallel process Bottom line: bridge gap between traditional self-
assembly and lithography
Process Overview
Dip wafer (Si) into micelle solution
Retrieve at 12mm/min
Air-evaporate solvent
Plasma (H2, Ar, or O2) removes polymer shell
Results: Uniform Hexagonal 2, 5, 6, or 8nm Spherical
PS(190)-b-P[2VP(Au0.2)](190) PS(500)-b-P[2VP(Au0.5)](270)
Side view TEM – treated wafer
PS(990)-b-P[2VP(Au0.5)](385) PS(1350)-b-P[2VP(Au0.5)](400)
Au ~ HAuCl4
Diblock Copolymer Micelles
Dendrite shaped macromolecule Corona is amphiphilic Micelle MW and shape controlled by
initial monomer concentration Polymer corona with “neutralized” core
(Au, Ag, AgOx, Pt, Pd, ZnOx, TiOx, Co, Ni, and FeOx)
Nanodot “core” size is controlled by the amount of metal precursor salt
In this paper:Water-in-oil micelle (toulene solvent)Polystyrene(x)-b-poly(2-vinylpyridine)(y) (PS(x)-b-P2VP(y))Au core from chloroauric precursor (HAuCl4)
Au
P2VP
PS
Cluster Pattern Characterization
MW tunes nanodot distance (max of 200 nm micelle) Low polydispersity permits regularity Higher MW decreased pattern quality and position precision
(softness in shell)
Low PDI
Guided Self-Assembly (>250nm) Predefine topographies
using photo or e-beam Spin-on concentrated
micelle solution (capillary forces of evaporating solvent adheres them to sides)
Micelles are pinned to the substrate by plasma (100W, 0.4mbar, 3min)
Lift-off removes PR and micelles
2nd plasma treatment removes micelle polymer (100W, 0.4mbar, 20min)
PS(1350)-b-P[2VP(Au0.5)](400)D = 8nm, L = 85nm
Cluster Aggregation
Vary PR thickness
Feature height (volume) defines cluster diameter
Figure: e-beam 200nm features on 2um square lattice
800nm
500nm
75nm
Line Patterning
Cylindrical micelle Formed if corona
volume fraction < core PS(80)-b-P2VP(330) Length of several
microns Substrate patterned
with grooves & dipped in micelle solution
4nm line
Negative Patterning with E-beam Spin-on micelles Expose with e-beam (1KeV, 400-
50,000 μC/cm2), 200um width Ultrasound bath + 30min plasma Electrons stabilize micelle on Si due
to carbon species formed during exposure
Micelles on Electrically Insulating Films Glass substrate
desired in biology
E-beam requires conductive substrate
Evaporate 5nm carbon layer
Mechanical Stability of Nano-Clusters Treated and unaffected by:
Pirahna, acids, many bases, alcohols, ultrasonic water bath
Hypothesis: edge formed by the substrate-cluster borderline is partly wetted by surface atoms during plasma treatment
Thermal 800 C evaporated clusters but no migration
occured
Conclusions
Simple process for sub-10nm clusters and lines
Block copolymer micelle size controls nano-cluster interspacing
Micelle size controlled by monometer concentrations
F. Weigl et al. / Diamond & Related Materials 15 (2006)
Micelles as masks for diamond field emitters