unconventional nanotechnology & nanopatterning (~2 lectures) scanning probe lithography (done)...
TRANSCRIPT
Unconventional Nanotechnology & Nanopatterning (~2 lectures)
Scanning Probe Lithography (done)
Soft-Lithography & Nanoimprint (Today)
Lecture 9
Throughput vs. Resolution
traditional $$$
"cheap" < $200k
unconventional (inexpensive, $0-$100k)
traditional (available at most top 20 research
universities$2000k)
traditional (>$2000k)unconventional
(inexpensive, $0-$100k)
Proc. Nanostructured Materials 2004
Science 291, 1763 (2001).
Exposure times 10 seconds
Electric Nanocontact Lithography
A large part of the following slides have been provided by
Dong Qin
Center for NanotechnologyUniversity of Washington who gave a talk on Soft-
Lithography at the Nanotechnology BootCamp in 2006.
Acknowledgements:
George M WhitesidesGeorge M Whitesidesand His Group at Harvardand His Group at Harvard
Parallel Techniques: Patterning with micro and nanocontacts...
Return of Investment (ROI)
Rapid PrototypingInvestment
Emerging nanopattering methods (replication)
pioneer (Whitesides) pioneer (Steven Choi) IBM
Early adaptors (IBM and HP)
The Father of Soft-Lithography
Soft lithography represents a new conceptual approach to the fabrication and manufacturing of new types of micro- and nano-structures at low cost
Soft-Lithography is the collective name for a set of new techniques:
micro-contact printing (µCP), replica molding (REM), micro-molding in capillaries (MIMIC), micro-transfer molding (µTM), solvent assisted embossing (SAE),
electric nanocontact lithography (ENL), nanotransfer lithography, micro and nanofluidics, etc.
Everything that uses a patterned elastomer (soft mask) as a stamp, mold, or mask to generate patterns and structures
instead of a rigid photomask.
Definition of Soft-Lithography
PDMS Stamp
• Two important properties: no adhesion to the substrate and no side chemical reactions taking place
• So, it is important that it has low interfacial energy and good chemical stability
• PDMS has good thermal stability and durability (can be used many times)
Soft-Lithography
The key to soft lithography are elastomers that form conformal contacts
provide a piece of PDMS.
• Polydimethylsiloxane (PDMS, silicone)
– Si-based organic polymer: (CH3)2SiO unit
– Elastomer after curing: chemically inert, durable
– Passes gas easily, not liquid
– Good thermal stability (~186oC in air)
– Optically transparent down to 300 nm
– Isotropic and homogeneous
– Good adhesion on Si and glass (surface modifiable)
• Curing process– 10:1 ratio of PDMS mix, PDMS oligomer and cross-link agent (Sylgard184, Dow Corning) is cast on the
mold and cured for 2 hour at 80oC in an oven.
De
mo
nst
rate
wh
at c
onfo
rma
l con
tact
s m
ean
.
Microcontact Printing
Exploration of µCP forchemical patterning of
surfaces and high-resolutionlithographies. The transfer ofink from a relief structure to atarget surface is a commonprocess in classical printing
techniques. In µCP thisprinciple is used to fabricate
chemical patterns withmicron-scale resolution on
technological surfaces.
http://zurich.ibm.com
Microcontact Printing (µCP)Self-Assembled Monolayers
(SAMs)• Relies on self-assembled
monolayers (SAMs)• Formed by substrate (AU
or Ag) immersion in ligand containing solution
• Thickness can be determined by changing methylene groups on alkyl chain
Microcontact Printing (µCP)•PDMS stamps are wetted with ink (hexadecanethiol in ethanol)
• Stamps are placed on top of SAMs for a short time (10-20s)
• Ink transfers to the substrate and forms hexadedecanethiolate to generate patterns
•SAMS must be autophobic and they must form rapidly with high order
PDMS
PDMS
Si
PDMS
Au/Ti
"ink"
Au/Ti"ink"
PDMS(a)
(b) (c)
Si
Si
Si Si
Au/Ti
SAM
Print SAMs
DepositEtch
X
(CH2)n
"S"60o
Au
2-3
nm
Glass
Microcontact Printing (µCP)•PDMS stamps are wetted with ink (hexadecanethiol in ethanol)
• Stamps are placed on top of SAMs for a short time (10-20s)
• Ink transfers to the substrate and forms hexadedecanethiolate to generate patterns
•SAMS must be autophobic and they must form rapidly with high order
PDMS
PDMS
Si
PDMS
Au/Ti
"ink"
Au/Ti"ink"
PDMS(a)
(b) (c)
Si
Si
Si Si
Au/Ti
SAM
Print SAMs
DepositEtch
X
(CH2)n
"S"60o
Au
2-3
nm
Glass
Substrate Molecules
AuAgCuPdGaAsInP
Alkanethiols (RSH) andAlkyldisulfides (RS-SR’)
Glass, Mica, Si/SiO2
HO-Terminated Polymer
Ag2O, Al2O3
ZrO2
Pt
Alkylsilanes, RSiCl3 or RSi(OEt)3
Alkylcarboxylic Acids (RCOOH)
Alkylphosphates (RPO3)
Alkylamines, Alkylisonitriles
"Inks" /SAMs
High-resolution µCP: (a)Scanning electron micrographof a stamp with 60 nm dots.The corresponding gold dots(b) fabricated by printing and
etching were slightlybroadened due to ink
diffusion and substrateroughness. (c) The gold
pattern served as a mask toetch the bare regions 250 nm
deep into the underlyingsilicon by reactive ion etching.
http://zurich.ibm.com
PDMS Stamp
PDMS + Ink
Si + Au
2. Gold Etch
3. Si etch
1. Print
Si + Au + Ink
Microcontact Printing
Microcontact Printing on Curved Substrates
Rogers & Whitesides et al, Science, 1995, 269, 664; Adv. Mater. 1997, 9, 475
Problems
• Gold and silver are not compatible with microelectronic devices based on silicon (SAMs). This is a slight problem if the purpose of these is for the microelectronic world
Chad Mirkin at Northwestern University
Dip-Pen Lithography (PDN)
Compare with Serial Writing Techniques such as: