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Polymer Synthesis
CHEM 421
“Organic imaging materials: a view of the future”
J. Phys. Org. Chem. 2000, 13, 767
“Advances in Patterning Materials for 193 nm
Immersion Lithography”
Chem. Rev. 2010, 110, 321–360
“Block Copolymer Nanolithography: Translation of
Molecular Level Control to Nanoscale Patterns”
Adv. Mater. 2009, 21, 4769–4792
“Tech Focus – Lithography”
Nature Photonics 2010, 4, 19-30
Semiconductor Manufacturing
Polymer Synthesis
CHEM 421
Photolithographic Process
Photoresist
Substrate
Polymer Synthesis
CHEM 421
Coat
h
Negative
Mask
Positive
Exposure
Develop
Etch
Strip
J. Phys. Org. Chem. 2000, 13, 767.
Model for Constructing a ChemicallyPolymer Synthesis
CHEM 421
Amplified Resist
Backbone
CH
CH2
CH
CH2
Etch
Barrier
Acidic
Group
OH
O
O
O
Protecting
Group
Levinson, Harry J. Principles of Lithography. SPIE Press, 2001.
Low- and High-Activation Energy
Chemically Amplified Resists
Polymer Synthesis
CHEM 421
• Copolymer of hydroxy styrene and
t-BOC protected hydroxy styrene
• Good hydrophilic/hydrophobic balance
• IBM’s Apex Resist
• Low activation energy, very reactive
• PAB below Tg
•
•
•
•
IBM’s ESCAP Resist
High activation energy, lower reactivity
Allows for high T bake
PAB above Tg
• removes stress
• removes residual solvent
• higher density films
• Low diffusion of PAG
“Transitions” in Optical Lithography
Polymer Synthesis
CHEM 421
365 nm
248 nm
193 nm
?
E-beam
EUV
157 nm
X-ray
How?
Polymer Synthesis
CHEM 421
R: resolution or critical dimension
k1: Rayleigh coefficient of resolution
Λ0: vacuum wavelength
n: refractive index of the incident medium
θ: angular aperture of the lens
n · sin θ is also referred to as the numerica
aperture (NA) of the imaging system.
Polymeric Materials Outlook for
157 nm Resist Design
Polymer
Absorbtion
Coefficient
(157 nm)
Polymer Synthesis
CHEM 421
Thickness (nm)
(OD = 0.4)
Poly(hydrosilsesquioxane)
0.06
6667
Poly(tetrafluoroethylene)
0.70
571
Poly(tetrafluoroethylene-coethylene) (30% TFE)
1.34
298
Poly(dimethylsiloxane)
1.61
248
Poly(vinyl alcohol)
4.16
96
Poly(methyl methacrylate)
5.69
70
Poly(norbornene)
6.10
66
Polystyrene
6.20
64
Poly(p-hydroxystyrene)
6.25
64
Poly(p-chlorostyrene)
10.15
39
R. R. Kunz et.al. J. Vac. Sci. Technol. B 17(6), Nov/Dec 1999
Emerging 157 nm Resist Platforms
Polymer Synthesis
CHEM 421
SO2
CF3
OH
A. E. Feiring and J. Feldman,
DuPont WO 00/67072.
CF3
O.D. @ 157 nm
1.4 micron-1
O.D. @ 157 nm
3.1 micron-1
H. Ito, G. Walraff, et. al. IBM
CF3
CH2
CH2 CH
C
H
CH
2
O
C
C
m
O
O
F3C
n
x
O
O
CF3
O
O
CF3
F3C
OCH3
G. Willson, UT
O.D. @ 157 nm
2.7 micron-1
y
O
OH
G. Willson, UT
F3C
CF3
R. Dammel, Clariant
O.D. @ 157 nm
2.5 micron-1
C. Ober, Cornell
OH
O.D. @ 157 nm
2.8 micron-1
Poly(TFE-co-NB-co-EVE)
Polymer Synthesis
CHEM 421
•Lowers Absorbance
•Increases CO2 Solubility
•Provides Contrast
•Increases Etch
Resistance
•Increases Tg
•Lowers Absorbance
•Increases CO2
Solubility
EVE is Ester Vinyl Ether
Poly(TFE-co-NB-co-EVE)
TFE
(mol %)
NB
(mol %)
FG
(mol %)
Tg
(°C)
50
50
0
125
38
59
3
126
40
41
55
52
5
7
Mn /
MWD
Polymer Synthesis
CHEM 421
Liq. CO2
Sol.
Abs.
@ 157 nm
Insol.
1.4
Insol.
1.38
115
3600 /
1.32
Insol.
1.29
92
3500 /
1.42
Insol.
To be
determined
??
3300 /
1.47
157/193 nm Photoresists
Teflon® AF as Backbone Material
Polymer Synthesis
CHEM 421
• Due to its amorphous structure and rigid backbone, Teflon® AF has unique
properties that are desirable in a photoresist backbone
Tetrafluoroethylene
(TFE)
2,2-Bis(trifluoromethyl)-4,5difluoro-1,3-dioxole
(PDD)
Advantages
Teflon® AF
Challenges
• very low absorbance
• cost of PDD monomer
• rigid structure (good etch
resistance)
• need functional monomer without
significantly increasing absorbance
• forms smooth films
• broad range of Tgs available
157/193 nm Photoresists
Absorbance at 157 nm and 193 nm
Absorbance [a10(mm-1)]
193
(nm)
Teflon® AF
0.154
0.004
CO2 Synthesized
Copolymer
0.153
0.019
• Values for Teflon® AF and
the CO2 synthesized
copolymer are very close
and well below 1 mm-1 at
157 nm
• Values at 193 nm are
slightly different but both
extremely low
2.5
2
-1
157.6
(nm)
Optical Density
a 10 (m m )
Sample
Polymer Synthesis
CHEM 421
1.5
T
1
0.5
0
145
155
165
175
185
wavelength (nm)
Teflon AF
CO2 Synthesized Copolymer
195
157/193 nm Photoresists
Teflon® AF as Backbone Material
• In order for a Teflon® AF
derivative to serve as a
photoresist, a functionalized
monomer that can be
cleaved by an acid must be
incorporated into the
backbone
CF2 CF2
CF
O
F 3C
Polymer Synthesis
CHEM 421
CF
O
Protected
Functional
Monomer
CF3
PAG
• After cleaving with a photo
acid generator (PAG) the
functional monomer will
exhibit different solubility
properties from unexposed
regions
CF2 CF2
CF
O
F 3C
CF
O
CF3
Acidic
Group
157/193 nm Photoresists
EVE/PDD/TFE Plackett-Burman Experiment Scheme
•
Chose to explore Ester Vinyl Ether (EVE)
as a prototype for potential EVE derived
functional monomers
•
Conducted a Plackett-Burman
experimental scheme varying five
parameters (composition, initiator
concentration, temperature, pressure and
reaction time) to study the reaction of EVE
with PDD and TFE
Exp. #
1
2
3
4
5
6
7
8
EVE/PDD/TFE
(mol %)
7/73/20
25/55/20
25/55/20
25/55/20
7/73/20
7/73/20
25/55/20
7/73/20
Initiator
(mol %)
1
0.2
0.2
1
1
0.2
1
0.2
Polymer Synthesis
CHEM 421
poly(TFE-co-PDD-co-EVE)
Temp (oC)
15
35
15
15
35
35
35
15
Pressure
(psi)
3500
3500
3500
1500
3500
1500
1500
1500
Rxn Time
(hr)
4
4
0.5
4
0.5
4
0.5
0.5
157/193 nm Photoresists EVE/TFE/PDDPolymer
Synthesis
Absorbance
CHEM 421
VASE® Absorbance [a10(mm-1)] Measurements
Sample
REH-004
REH-013
REH-005
Composition
(mol %)
7/73/20 EVE/PDD/TFE
(Charged)
12/59/29
EVE/PDD/TFE
18/54/28
EVE/PDD/TFE
157.6
(nm)
193
(nm)
0.128
0.013
0.252
0.011
0.574
0.017
• Absorbance values at 157 nm increase with increasing EVE
content but still remain well below 1 (mm-1)
• Values at 193 nm are very low and vary only slightly
157/193 nm Photoresists
Absorbance at 157 nm and 193 nm
Absorbance [a10(mm-1)]
193
(nm)
Teflon® AF
0.154
0.004
CO2
Synthesized
Copolymer
0.153
0.019
• Values for Teflon® AF and
the CO2 synthesized
copolymer are very close
and well below 1 mm-1 at
157 nm
• Values at 193 nm are
slightly different but both
extremely low
2.5
2
-1
157.6
(nm)
Optical Density
a 10 (m m )
Sample
Polymer Synthesis
CHEM 421
1.5
T
1
0.5
0
145
155
165
175
185
wavelength (nm)
Teflon AF
CO2 Synthesized Copolymer
195
157/193 nm Photoresists
Teflon® AF as Backbone Material
• In order for a Teflon® AF
derivative to serve as a
photoresist, a functionalized
monomer that can be
cleaved by an acid must be
incorporated into the
backbone
CF2 CF2
CF
O
F 3C
Polymer Synthesis
CHEM 421
CF
O
Protected
Functional
Monomer
CF3
PAG
• After cleaving with a photo
acid generator (PAG) the
functional monomer will
exhibit different solubility
properties from unexposed
regions
CF2 CF2
CF
O
F 3C
CF
O
CF3
Acidic
Group
157/193 nm Photoresists
Polymer Synthesis
CHEM 421
EVE/PDD/TFE Plackett-Burman Experiment Scheme
•
•
Chose to explore Ester Vinyl Ether (EVE)
as a prototype for potential EVE derived
functional monomers
Conducted a Plackett-Burman
experimental scheme varying five
parameters (composition, initiator
concentration, temperature, pressure and
reaction time) to study the reaction of EVE
with PDD and TFE
CF 2 CF 2
CF
O
CF
O
CF
CF
F2C
F3C
O
O
CF 3
CF
O
CF 2 CF 2
CF 3
poly(TFE-co-PDD-co-EVE)
Exp. #
EVE/PDD/TFE
(mol %)
Initiator
(mol %)
Temp (oC)
Pressure
(psi)
Rxn Time
(hr)
1
7/73/20
1
15
3500
4
2
25/55/20
0.2
35
3500
4
3
25/55/20
0.2
15
3500
0.5
4
25/55/20
1
15
1500
4
5
7/73/20
1
35
3500
0.5
6
7/73/20
0.2
35
1500
4
7
25/55/20
1
35
1500
0.5
8
7/73/20
0.2
15
1500
0.5
OCH 3
157/193 nm Photoresists EVE/TFE/PDDPolymer
Synthesis
Absorbance
CHEM 421
VASE® Absorbance [a10(mm-1)] Measurements
Sample
REH-004
REH-013
REH-005
Composition
(mol %)
7/73/20 EVE/PDD/TFE
(Charged)
12/59/29
EVE/PDD/TFE
18/54/28
EVE/PDD/TFE
157.6
(nm)
193
(nm)
0.128
0.013
0.252
0.011
0.574
0.017
• Absorbance values at 157 nm increase with increasing EVE
content but still remain well below 1 (mm-1)
• Values at 193 nm are very low and vary only slightly
“Transitions” in Optical Lithography
Polymer Synthesis
CHEM 421
365 nm
248 nm
193 nm
?
E-beam
EUV
157 nm
X-ray
Immersion: Win of 193 nm over 157 Polymer Synthesis
CHEM 421
nm
Polymer Synthesis
CHEM 421
http://www.almaden.ibm.com/st/chemistry/lithography/immersion/
Polymer Synthesis
CHEM 421
http://www.almaden.ibm.com/st/chemistry/lithography/immersion/NEMO/
EUV: 13.5 nm wavelength
Polymer Synthesis
CHEM 421
38 nm: feature size can be
resolved by most advanced
193 nm immersion
lithography systems
< 10 nm: by EUV
Technically Very Challenging!
Polymer Synthesis
CHEM 421
Block Copolymer Lithography
• a thin film of PS-b-PMMA
BCP thermally annealed to
produce the PMMA
cylindrical microdomains
oriented normal to the
surface.
• Exposed to UV radiation
i. PMMA block is
degraded
ii. PS matrix is cross
linked.
• removing the
decomposition products
with acetic acid
• nanoporous crosslinked PS
templates are produced
Polymer Synthesis
CHEM 421
Cross-linking units
Polymer Synthesis
CHEM 421
Tri-block
Polymer Synthesis
CHEM 421
E-Beam Lithography
Polymer Synthesis
CHEM 421
http://nextbigfuture.com/2009/06/double-triple-and-quadruple-patterning.html
Nanoimprint Lithography (NIL)
Polymer Synthesis
CHEM 421