Transcript Scanning Probe Lithography (SPL)

Scanning Probe Lithography
(SPL)
CHEM *7530/750
Olivier Nguon
February 7th, 2006
Outlines
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Definition
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Scanning Probe Microscopes (SPMs)
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Scanning Probe Lithography
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Conclusions
Definition: Lithography
Greek Lithos: stone
“Printing process in which the
image to be printed is rendered
on a flat surface, and treated to
retain ink while the nonimage
areas are treated to repel ink.”
(The American Heritage® Dictionary of the English
Language, Fourth Edition Copyright © 2004)
"Girl with Flowers",
Lithography by Angel
Botello (1980)
Definition: Scanning Probe Lithography
Scanning probe lithography:
Lithography using a sharp tip in
proximity to a sample to
pattern nanometer-scale
features
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Instrument:
Scanning Probe Microscope
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100-nm-wide, 2-nm-thick spiral
of polymer (poly(ethyl)amine)
(Lloyd Whitman,
US Naval Research 1100)
Scanning Probe Microscope (SPMs)
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Monitor local interactions between a tip and a
sample
Physical, electrical or chemical information
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Types of SPMs:
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Scanning Tunneling Microscope
Atomic Force Microscope
SPMs: Scanning Tunneling Microscope
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Voltage bias between tip
and sample
Electrons tunnel between
two electrodes
Current sensitive to the
distance
_______________
Resolution: atomic scale
Vacuum needed
Substrate: conductive
Scanning tunneling microscope
(Ludwig-Maximilians-Universität,
München, W.M. Heckel)
SPMs: Atomic Force Microscope
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Flexible cantilever with
sharp tip
Forces between
surface and tip
detected by deflection
_____________
No vacuum needed
Non-conductive
material allowed
(Helen G. Hansma, Department of
Physics, University of California)
Scanning Probe Lithography
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SPMs used to modify a sample surface:
1.
Atomic Manipulation
2.
Mechanical and Termomechanical Pattering
3.
Local Oxidation
4.
Electron Exposure of Resists
1. Atomic Manipulation
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SPM probe tip used to
“push” or “pull” a particle
Push: Electric field and dipole
moment of atom lead to
potential energy gradient
Pull: Chemical binding force
between tip and atoms
or
Magnetic interactions
Pick-up of magnetic beads with the
magnetizable tip in the presence of an
external magnetic field
(Jörn F. Lübben, EMPA swizerland)
2. Local Oxidation
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Voltage bias between probe tip and sample
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Intense electric field
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Local oxidation
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Silicon: Growth of silicon oxide from crystal Si
Electric-field-enhanced oxidation
3. Mechanical & Termomechanical
Patterning
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Probe tip used to “plough” a soft layer
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Heating of the tip to melt the layer
Mechanical patterning
(Graham Leggett, 2002)
4. Electron Exposure of Resist
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Electric bias between conductive probe
tip and sample
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Field emission of electrons
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Chemical changes induced (crosslinking, scissions bonds, etc.)
Electron lithogaphy
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Etching
K. Kobayashi Tokyo
Institute of Technology
Conclusions
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Ability to pattern nanometer-scale features
Attracting method to semi-conductor industry
Limits
Throughput capabilities (coverage rates mm/s
->cm/s)
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Future evolution
Carbon Nanotubes as scanning probes
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References
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C. F. Quate, H. Soh, Scanning Probe
Lithography, Kluwer Academic Publishers,
(2001). TK 7874 S648 2001
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L. L. Sohn, Appl. Phys. Lett., 67,1552-4
(1995).
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J.A. Stroscio, Science, 254, 1319-26, (1991).
Thank you !!
48 Fe atoms on a Cu (111) surface, Crommie et al., Science 1993