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Printing electronic devices
School of Engineering and Science
Amare Benor
22.11. 2005
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� Motivation
� Different printing techniques
� Microcontact printing
� Self assembly process
� Selective surface wetting
� Applications
� Summary
Outline
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Motivation
Macroelectronicsmanufacturing needs a paradigm change:
�Photolithography�Printing:Flexible substrates0
10
20
30
40
50
60
2000 2001 2002 2003 2004 2005 2006 2007
mar
ket s
ize
($B
illio
n)
The display market is big and getting rapidly bigger
DisplaySearch data
Big LCD TVs are coming …..30”, 40”, 50”, 60”….
Gen 5 → Gen 7 fabs. Substrates are getting really large
Philips
Philips
Vision!
Alternativeprocessing Technologies:
Roll-to-Roll, Sheet vs Batch Processing
Learning form Printing Processes
Motivation
Different Printing Technologies
Offset printing Microcontact printingInkjet printing
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Photolithography and Microcontact Printing
Microcontact Printing
Advantages:Low cost, Additive process (mostly)High resolutionApply to non-planar surfaces/ConformalUses a variety of materials
Disadvantages:Emerging TechnologyRegistration problems
Photolithography
Advantages:High resolutionVery good registration/alignmentMass production
Disadvantages:High costSubtractive processLimited by optical diffraction
resolution ~ 100 nm
photo resist
UV light
Substrate
Mask
� soft stamp
� conformal contact,
� molecules wet
� resolution ~ 35 nm
Microcontact Printing
Advantages:Low cost, Additive process (mostly)High resolutionApply to non-planar surfaces/ConformalUses a variety of materials
Disadvantages:Emerging TechnologyRegistration problems
Advantages:Low cost Additive process (mostly)High resolutionApply to non-planar surfaces
Disadvantages:Emerging TechnologyRegistration problems
Microcontact Printing
resolution ~ 35 nm
soft stamp
moleculesSubstrate
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Basic elements of �CP:
� Stamp
- made of silicon based elastomer
(poly-dimethylsiloxane, PDMS)
- conformal contact with substrate
� Self assembled monolayers (SAMs)
���� for different applications
(functionalize surface,etch resist,
selective deposition, ...)
Microcontact Printing (�CP)
Principles of �CP (one of the printing techniques)
Substrate
Master
Coating stamp with SAM
Transfer of SAM
Patternformation
Manufacturing of the stamp
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Self Assembly Process
Self Assembled Monolayer as Resist (Whiteside’s Approach)
• Thiol molecule printed on metal
surface (gold, silver)
• Thiol used as etch resist
• Interface chemistry is essential
• Resolution: < 100 nm
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Functionalizing Surfaces
• Printing of OTS (octadecyltrichlorosilane) molecules on silicon or glass
• Hydrophilic/hydrophobic pattern is formed
• Stamped region ���� Hydrophobic
• Unstamped region ���� Hydrophilic
• Reactive site on unstamped region
Hydrophobic SAMs
Eg. OTS, ...
Stamped region
(Hydrophobic)Unstamped region
(Hydrophilic)
OTS (CH3(CH2)17SiCl3) SAMs
Self Assembly Process
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Selective Surface Wetting
Patternable polymer:
Resist, Polymer, Semiconducting polymer
Dipcoat polymer
UV exposure to remove OTS SAMs
Patterned Polymer
Patterned OTS SAMs
General approach to pattern polymer and metal
100 µµµµm
S D S D
F8T2 TFT fabricated by micro-contact patterning [M. Chabinyc et al.]
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Selective Surface Wetting
Metal pattern:
Ti, Au, Pt,...
After e-beam evap. of (Ti/Au) and lift off
E-beam evap. of (Ti/Au)
Patterned Polymer
General approach to pattern polymer and metal
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Resolution (~ 20 �m)
Application: Passive Components (Coils)
RFID (Radio Frequency IDentification) Tags:
� Chip
� Antenna/coli
Radio Frequency (RF) coils
PMMA
OTSAu
Stamp
50 �m
50 �m50 �m
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Electrodes and Interconnects
20 �m 20 �m 10 �m
Electrodes with 20, 10 and 5 �m gap
Resolution (~ 10 �m)
Application: Interconnects and electrodes
• Smallest features size depends on the geometry of the features.
• The resolution is limited by the selective wetting rather than the micro contact printing.
Dielectric
Gate
Highly doped silicon
Source
Org. Semicon.
DrainVD
VG
VS
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DiscussionEffect of film (PMMA) thickness and geometry on dewetting
Homogeneous surface3/2)(Calh c=
glc ρ
σ=
Heterogeneous surface3/1)(CaWh =
where, σ
µUCa =and
σ = surface tension
ρ = surface density
µ = viscosity of the liquid
U = withdrawal speed of the substrate
As h increases ���� budging effect and pattern distortion
PMMAOTS
w
w
substrate
h
Top view
Side viewDifferent geometry can result different resolution
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Summary� Micro Contact Printing (µCP) is a promising technique for applications in organic electronics and photonics devices
� µCP of SAMs allows for surface energy modifications
� A combination of �CP and dewetting can be used used a universal patterning process
� Microcontact printing and dewetting can be used to pattern polymers
� Microcontact printing and dewetting was used for to pattern metal films for interconnects, rf coils and OFET electrodes
� The film thickness is crucial parameter to get the required width of a patterned polymer