Molecular Layer Methods for High
Throughput Tuning of Surface Properties
A. Anderson, B. Kobrin*, J. Chinn*,
W. Robert Ashurst
Department of Chemical Engineering
Auburn University
* AMST
TAPPI 2006 International Conference on Nanotechnology
April 28, 2006
Introduction/Outline
• Molecular Films – Conventional Processing and
Application to Cellulose
• Limitations of Conventional Processing
• The MVD Method
• Precursors used with MVD
• Results and Comparison of MVD Films with
Conventional Liquid Phase Processed Films
• Conclusion
2
1
Chlorosilane Reaction
CH3
CH3
Si
Cl Cl Cl
Si
Cl Cl Cl
OH
Si
water
layer
OH
O
Si
CH3
O
Si
O
CH3
O
Si
O
Si
Si
O
Si
CH3
Si
OH OH OH
Si
OH OHOH
OH
OH
Si
CH3
Si
Si
OH OH OH OH OHOH
OH
OH
Si
CH3
O
Si
CH3
O
Si
O
Si
CH3 CH3
Si
Si
Si
Si
O
O
O
O
O
O
O
Si
Si
Si
Si
O
O
O
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Application to Cellulose
Cellulose has many reactive OH groups exposed, similar
to native oxide of silicon.
Reactions on silicon oxide that can be done with these OH
groups on silicon should be possible with cellulose as well.
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2
Liquid Phase Processing
Surface Surfactant
(Ketone)
Oxidation
(H2O2, etc)
Water
Removal
(Iso-Octane)
Monolayer
Deposit
Excess
Precursor
Removal
Rinse
(IPA)
Final
Rinse
Methanol
(Iso-Octane)
Laborious
Depends on Environment (RH)
Costly
Need Expertise
Need Dry Reagents
Solvent Waste
Much Handling of Devices
Difficult to Scale Up
Particles
5
The MVD Process
1. Sample loaded to the MVD System
2. Plasma surface clean to activate the surface for MVD reaction
3. Adhesion seed layer deposition to increase reactive sites on
target surface
4. Surface reaction with the chosen precursor to generate
desired surface properties
6
3
Process Scale Evolution
(1 cm square, 2001)
(Single 150 mm wafer, 2002)
(Cassette of 200 mm
wafers – reality!)
Time
7
MVD Equipment Schematic
8
4
Useful Precursors (I)
FDTS
DDMS
V11TCS
VTS
FDDMCS
333TFPMDS
9
Useful Precursors (II)
APTS
γ-MAOPTS
34ECHETS
γ-MPTS
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5
Useful Precursors (III)
All precursors illustrated here undergo
hydrolysis to form a silanol intermediate.
The silanol intermediate participates in
condensation reaction with surface OH
groups to link the pendant group onto
the surface via *-O-Si-R linkage.
The resulting surface is prescribed by
the pendant group and can be further
derivatized as desired.
PF10TAS
11
Common Evaluation Tools
Contact Angle Analysis
(surface energy)
X-ray Photoelectron Spectroscopy
(film chemical composition)
12
6
Applicability to Various Substrates
120
Contact angle, deg.
100
80
60
Si
Glass
Acrylic
Polystyrene
St.Steel
40
20
FOTS
0
0
30
80
150
200
400
Seed thickness, A
MVD can be accomplished on a wide variety of substrates.
13
Immersion Stability
Seed layer improves immersion stability for FOTS on glass.
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7
Immersion Stability (II)
FOTS on TiN
Contact angle, deg.
140
120
100
80
60
40
FOTS
20
FOTS with seed
0
1
2
3
4
5
6
7
8
9
10 11 12 13 14
Days
Seed layer also improves immersion stability for FOTS on TiN.
15
Thermal Stability
FOTS on Al
Contact angle, deg.
120
100
80
60
40
FOTS
FOTS with seed layer
20
0
0
4
8
12
16
20
24
Hours of Heat Treatment at 250 C
Seed layer improves thermal stability for FOTS on Al.
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8
MVD Sequential Process Flow
Final structure is DDMS/Seed layer/FOTS/Silicon Oxide/Si Wafer.
17
Conclusions
• MVD is a highly general gas phase process with
high throughput and distinct advantages over
conventional liquid processing
• MVD allows facile sequencing of layers for
advanced molecularly engineered materials
• MVD can be carried out on a number of
substrates, and may provide improved film
qualities, such as enhanced thermal and
immersion stability
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9
Acknowledgements
AU-CRG: Contributed funding
for this project.
Applied
M
S
T
AMST: Contributed material support
for this research as well as research
data discussed in this presentation.
NSF: Contributed funding this
conference.
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