block copolymer micelle nanolithography roman glass, martin moller and joachim p spatz university of...

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