1. Block Copolymer Micelle Nanolithography Roman Glass, Martin Moller and Joachim P Spatz University of Heidelberg IOP Nanotechnology (2003)
Erika Parra
EE235
4/18/2007

2. 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

3. 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)
PS(990)-b-P[2VP(Au0.5)](385)
PS(1350)-b-P[2VP(Au0.5)](400)
Side view TEM – treated wafer
Au ~ HAuCl4

4. 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 PS
P2VP Au
PS blocks form a shell around the less solvable P2VP blocks to reduce energetically unfavorable interactions with the solvent
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)

5. Cluster Pattern Characterization
Low
PDI
MW tunes nanodot distance (max of 200 nm micelle)
Low polydispersity permits regularity
Higher MW decreased pattern quality and position precision (softness in shell)

6. 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

7. Cluster Aggregation Vary PR thickness
Feature height (volume) defines cluster diameter
Figure: e-beam 200nm features on 2um square lattice
800nm
500nm
75nm

8. 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

9. Negative Patterning with E-beam
Spin-on micelles
Expose with e-beam (1KeV, ,000 μC/cm2), 200um width
Ultrasound bath + 30min plasma
Electrons stabilize micelle on Si due to carbon species formed during exposure

10. Micelles on Electrically Insulating Films
Glass substrate desired in biology
E-beam requires conductive substrate
Evaporate 5nm carbon layer

11. 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

12. Conclusions Simple process for sub-10nm clusters and lines
Block copolymer micelle size controls nano-cluster interspacing
Micelle size controlled by monometer concentrations
Micelles as masks for diamond field emitters
F. Weigl et al. / Diamond & Related Materials 15 (2006)