Scanning Probe Microscope (SPM) Lithography
Or Scanning Probe Lithography (SPL)
A Scanning Probe Microscope tip,such as an
Atomic Force Microscope (AFM) or Scanning
Tunneling Microscope (STM) tip,is used to
locally modify a surface,much like a pen or knife
Scanning Probe Lithography (SPL)
Mechanical scratching
Anodization of Si surface
Electrochemical decomposition of self-assembled
monolayer
Electrofield induced chemical reaction
Electrochemical reaction in solution using protected
STM tips
Optical or Optical-Assisted Lithography
AFM Dip-Pen Nanolithography (DPN)
Surface modification by STM
tip with a voltage and current,
line spacing is 3nm
Mechanical Modification of
Surface with AFM Tip
Line pattern created by
NSOM-based Lithography
Surface oxidation of silicon
surface by STM
Ag line obtained by
electrochemical reduction
of Ag
+
in solution with
STM
SEM image of Chromium
Lines created by…
Dip-Pen Nanolithography
Dip-Pen Nanolithography (DPN) is an AFM lithography technique where
molecules are transported from AFM tip to surface to form nanostructures
From Piner et,al,Science 283,661.
Water meniscus spontaneously condenses
between AFM tip and surface,which
facilitates transport of the molecules from
tip to surface,Deposition occurs due to
surface affinity of the solutes.
Previous efforts (by Chad Mirkin,NWU):
serial patterning of alkanethiols on gold
parallel patterning using several AFM tips
patterning alkanethiol-based etch resists
Patterning hexamethyldithilathane on semiconductor surfaces
"Dip-Pen" Nanolithography
Richard D,Piner,Jin Zhu,Feng Xu,Seunghun Hong,and Chad A,
Mirkin,Science 1999 January 29; 283,661-663.
Multiple Ink Nanolithography,Toward a Multiple-Pen Nano-
Plotter
Seunghun Hong,Jin Zhu,and Chad A,Mirkin; Science 1999
October 15; 286,523-525,
A Nanoplotter with Both Parallel and Serial Writing
Capabilities
Seunghun Hong and Chad A,Mirkin;Science 2000 June 9; 288,
1808-1811,
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Pt(IV)+4e Pt(0)
Silicon
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AFM image of a platinum line drawn by the E-DPN method
under the condition of relative humidity 40% with a voltage
of 4 V and a translation speed of 5 nm/s,
(a) A silver line drawn by E-DPN method with AgNO
3
solution as
the ink,Experimental conditions,relative humidity,42%,voltage,
4V,translation speed,20nm/s.
(b) A germanium line with the saturated solution of GeO
2
in 0.05
M NaOH as the ink,relative humidity,42%,voltage,5V,
translation speed 100nm/s,
(c) A palladium line using PdCl
2
as the precursor,Relative
humidity,38%,voltage,3.5V,scan speed,10 nm/s,
(d) A copper square with CuCl
2
as precursor,Relative
humidity,46%,voltage,3V,scan speed,50 nm/s.
Factors that may affect the height and width of the
fabricated features using the E-DPN technique:
humidity
scan speed
applied voltage
character of tip (shape and conductivity)
property of the wafer(conductivity and surface property)
amount of salts on tip
property of metal salts
50% 46% 41%
Relative Humidity
Ink,saturated solution of GeO
2
in 0.05 M NaOH
AFM image and height profile of two Pt lines drawn at
different scan speed,Left line at 10 nm/s and right line at 20
nm/s,The voltage applied at the tip is 3V for both lines and
the relative humidity is 43%.
AFM images and height profiles of two Cu dots drawn at
different voltage,top dot at 2.0V and bottom dot at 5.0V,Scan
speed is 100 nm/s and the relative humidity is 50%.
(a) The character "V" composed of platinum (left) and silicon oxide (right),The
Pt line is drawn with a voltage of +4 V between the tip and the wafer and a scan
speed of 10 nm/s,The SiO
2
line is created with a -10 V voltage to oxidize the
surface and the scan speed is 50 nm/s,The relative humidity is 58%,(b) The
same area of the wafer after heated at 500 o C under the atmosphere of
ethylene in argon for an hour.
Au(III) + Si(0) Au(0) + Si(IV)
Letters,DU” drawn at 10 nm/sec at 40% relative humidity
USING THE TINY WATER DROPLET AS A
NANOMETER-SIZED REACTION VESSEL