unconventional nanotechnology & nanopatterning (~2 lectures) scanning probe lithography (done)...

33
Unconventional Nanotechnology & Nanopatterning (~2 lectures) Scanning Probe Lithography (done) Soft-Lithography & Nanoimprint (Today) Lecture 9

Upload: lester-russell

Post on 16-Dec-2015

226 views

Category:

Documents


2 download

TRANSCRIPT

Unconventional Nanotechnology & Nanopatterning (~2 lectures)

Scanning Probe Lithography (done)

Soft-Lithography & Nanoimprint (Today)

Lecture 9

Electric Scanning Probe Lithography

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

Hot Embossing, Injection Molding, Casting on a nanoscale...

Old concepts with new names?

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

Soft Mask Fabrication using PDMS

PDMS: Polydimethylsiloxane

Frankel & Whitesides

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

.

Xia & Whitesides, Angew. Chem. Int. Ed. Engl. 1998, 37, 551.

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

Interfacial Engineering

Copyright of Whitesides

Selective Attachment of Cells

Chen & Whitesides et al, Science. 1997, 276, 1425.

Formation of CuSO4 Crystals

Qin & Whitesides et al, Advanced Materials, 1999, 11,1433.

Patterns of Silver and Silicon

Xia & Whitesides, Angew. Chem. Int. Ed. Engl. 1998, 37, 551.

Kumar & Whitesides et al, Langmuir, 1995, 11, 825

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

Microcontact Printing of Proteins

Nanotech User Facility at the University of Washington

(anti-Goat IgG – Alexa 488 and 594)

Patterned Proteins

Dong Qin

Chad Mirkin at Northwestern University

Dip-Pen Lithography (PDN)

Compare with Serial Writing Techniques such as:

Chad Mirkin at Northwestern University