Polymer Synthesis CHEM 421 Semiconductor Manufacturing.
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Transcript of Polymer Synthesis CHEM 421 Semiconductor Manufacturing.
Polymer SynthesisCHEM 421Semiconductor Manufacturing
Polymer SynthesisCHEM 421
Photolithographic Process
J. Phys. Org. Chem. 2000, 13, 767.
Coat
Exposure
Develop
Strip
Etch
Photoresist
Substrate
Maskh
PositiveNegative
Polymer SynthesisCHEM 421
Important Properties of a Photoresist
• Resist Thickness (etch resistance)Resist Thickness (etch resistance)
• Solubility for deposition/developmentSolubility for deposition/development
• WettabilityWettability
• Lithographic performanceLithographic performance
–Sensitivity, contrastSensitivity, contrast
• TransparencyTransparency(more important for 193 nm and beyond)(more important for 193 nm and beyond)
Polymer SynthesisCHEM 421
Optics of Imaging
R = resolution = smallest feature sizeR / NA
• is the wavelength of light• NA is the numerical aperture (a function of the optics)
Wavelength Wavelength 365 nm 248 nm 193 nm 157 nm
NotationNotation i-line DUV 193 nm 157 nm
mercury KrF ArF F2 excimer Source Source lamp excimer excimer laser laser laser
Feature Size Feature Size 365+ nm 500 - 100 nm 130 - 70 nm* 90 - 45 nm*
Polymer SynthesisCHEM 421
G- and I-line Resists
• Novolac resinNovolac resin– Base-soluble positive resist (TMAH)Base-soluble positive resist (TMAH)– Variety of structures and MW’sVariety of structures and MW’s
• Diazonapthaquinone (DNQ)Diazonapthaquinone (DNQ)– Photoactive compound (Wolfe Rearrangement)Photoactive compound (Wolfe Rearrangement)– Inhibits base-dissolution of novolacInhibits base-dissolution of novolac
OH
CH3
OH
CH3
CH2
O
N2
R
O
R R
C
O
H2O
R
CO2H
h
-N2
Polymer SynthesisCHEM 421“Transitions” in Optical Lithography
365 nm365 nm
248 nm248 nm
Polymer SynthesisCHEM 421
Chemical Amplification
• DUV exposure generates catalytic DUV exposure generates catalytic amount of acid from a photoacid amount of acid from a photoacid generator (PAG)generator (PAG)
• 1-2 min PEB to trigger 1-2 min PEB to trigger deprotectiondeprotection
• Catalytic chain length is extremely Catalytic chain length is extremely longlong
– About 500 - 1000 About 500 - 1000 carbonate cleavages per carbonate cleavages per protonproton
H+
CH CH2
O
O
O
H+
J. Phys. Org. Chem. 2000, 13, 767.Acc. Chem Res. 1994, 27, 150.
CH CH2
O
O
O
CH CH2
O
OH
O
CH CH2
OH
C
O
OH
H+
Polymer SynthesisCHEM 421
Challenges with Chemical Amplification
• What if trace amounts of base (NMP solvent) What if trace amounts of base (NMP solvent) was found in the air in a FAB?was found in the air in a FAB?
Levinson, Harry J. Principles of Lithography. SPIE Press, 2001.
• Catalyst Catalyst susceptible to susceptible to poisoning by poisoning by atmospheric atmospheric basesbases
Polymer SynthesisCHEM 421
Model for Constructing a Chemically Amplified Resist
Levinson, Harry J. Principles of Lithography. SPIE Press, 2001.
Etch Barrier
Backbone
Protecting Group
Acidic Group
CH CH2 CH CH2
OOH
O
O
Polymer SynthesisCHEM 421
Low- and High-Activation Energy Chemically Amplified Resists
CH CH2
O
O
O
CH CH2
OH
• 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
CH CH2
C
CH CH2
OH
O
O
• 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
Polymer SynthesisCHEM 421“Transitions” in Optical Lithography
365 nm365 nm
248 nm248 nm
193 nm193 nm
Polymer SynthesisCHEM 421Absorption of Resins
190 200 210 220 230 240 250 260 270 280 290 300 310 320 330 340 350
1.8
1.5
1.1
0.8
0.5
0.3
0.1
AbsorptionCoefficient(micron-1)
Wavelength (nm)
Poly(p-hydroxy styrene)
Polyacrylate
Optimal range
Polymer SynthesisCHEM 421Design Criteria for 193 nm Resists
• Optical transparency
• Hydrophilicity
• High Tg (130-170 °C)
• Good etch resistance
• Easily blocked hydroxyl group
Polymer SynthesisCHEM 421
Photoresists for 193 nm Lithography
CH2 C
CH3
CH2 C
CH3
CH2 C
CH3
O
OCH3
O
OH
O
O
C(CH3)3
CH2 C
CH3
CH2 C
CH3
CH2 C
CH3
O
OCH3
O
OH
O
OH
PAG
• Extremely transparent at 193 nm
• Tunable composition
• Property diversity
• Good hydrophilicity
• High activation energy
cleavable group
• Easily synthesized
• But poor etch resistance…
Polymer SynthesisCHEM 421
Photoresists for 193 nm Lithography
CH2 C
CH3
CH2 C
CH3
CH2 C
CH3
O
O
O
OH
O
O
O
Dry etch resistance &transparency
Cleavablegroup
Hydrophilicity
Polymer SynthesisCHEM 421
Photoresists for 193 nm Lithography
AT&T / Lucent / Agere
O
O
OO O
+ AIBN
THF
O
O
OO O
Polymer SynthesisCHEM 421“Transitions” in Optical Lithography
365 nm365 nm
248 nm248 nm
193 nm193 nm
157 nm157 nm
Absorptionat 157 nm??!!
Polymer SynthesisCHEM 421
PolymerPolymer
Absorbtion Absorbtion Coefficient Coefficient
(157 nm)(157 nm)
Thickness (nm)Thickness (nm)
(OD = 0.4)(OD = 0.4)
Poly(hydrosilsesquioxane)Poly(hydrosilsesquioxane) 0.060.06 66676667
Poly(tetrafluoroethylene)Poly(tetrafluoroethylene) 0.700.70 571571
Poly(tetrafluoroethylene-co-Poly(tetrafluoroethylene-co-ethylene) (30% TFE)ethylene) (30% TFE) 1.341.34 298298
Poly(dimethylsiloxane)Poly(dimethylsiloxane) 1.611.61 248248
Poly(vinyl alcohol)Poly(vinyl alcohol) 4.164.16 9696
Poly(methyl methacrylate)Poly(methyl methacrylate) 5.695.69 7070
Poly(norbornene)Poly(norbornene) 6.106.10 6666
PolystyrenePolystyrene 6.206.20 6464
Poly(p-hydroxystyrene)Poly(p-hydroxystyrene) 6.256.25 6464
Poly(p-chlorostyrene)Poly(p-chlorostyrene) 10.1510.15 3939
R. R. Kunz et.al. J. Vac. Sci. Technol. B 17(6), Nov/Dec 1999
Polymeric Materials Outlook for 157 nm Resist Design
Polymer SynthesisCHEM 421
Emerging 157 nm Resist Platforms
CF2CF2
A. E. Feiring and J. Feldman,DuPont WO 00/67072.
SO2
OHCF3
CF3
H. Ito, G. Walraff, et. al. IBM
CH2 C
C
OCH3
O
CF3
G. Willson, UT
O
O CF3
OHF3C
x y
G. Willson, UT
R. Dammel, Clariant
CH2 CH CH2
CH
O
O
O
O
CF3F3C
F3C CF3
OH
nm
O
C. Ober, Cornell
O.D. @ 157 nm1.4 micron-1
O.D. @ 157 nm3.1 micron-1
O.D. @ 157 nm2.7 micron-1 O.D. @ 157 nm
2.8 micron-1O.D. @ 157 nm
2.5 micron-1
Polymer SynthesisCHEM 421
Poly(TFE-co-NB-co-EVE)
•Lowers Absorbance
•Increases CO2 Solubility
•Increases Etch Resistance
•Increases Tg
•Provides Contrast
•Lowers Absorbance
•Increases CO2 Solubility
EVE is EVE is EEster ster VVinyl inyl EEtherther
CF2CF2 CF2 CF
OCF2 CF
CF3
OCF2
CF2
O
OMe
Polymer SynthesisCHEM 421
Poly(TFE-co-NB-co-EVE)
TFETFE(mol %)(mol %)
NBNB(mol %)(mol %)
FGFG(mol %)(mol %)
TTgg
((°°C)C)Mn /Mn /
MWDMWDLiq. COLiq. CO22
Sol.Sol.Abs.Abs.
@ 157 nm@ 157 nm
5050
3838
5050
5959
00
33
125125
126126
????
3300 /3300 /1.471.47
Insol.Insol.
Insol.Insol.
1.41.4
1.381.38
4040 5555 55 1151153600 /3600 /1.321.32 Insol.Insol. 1.291.29
4141 5252 77 92923500 /3500 /1.421.42 Insol.Insol. To be To be
determineddetermined
CF2CF2 CF2 CF
OCF2 CF
CF3
OCF2
CF2
O
OMe
Polymer SynthesisCHEM 421
157/193 nm PhotoresistsTeflon® AF as Backbone Material
• Due to its amorphous structure and rigid backbone, Teflon® AF has unique Due to its amorphous structure and rigid backbone, Teflon® AF has unique properties that are desirable in a photoresist backboneproperties that are desirable in a photoresist backbone
Advantages 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
Tetrafluoroethylene(TFE)
2,2-Bis(trifluoromethyl)-4,5-difluoro-1,3-dioxole
(PDD)
CF2 CF2 + CF2 CF2 / CF CF
O O
F3C CF3
i
CF CF
O O
F3C CF3
Teflon® AFTeflon® AF
Polymer SynthesisCHEM 421
157/193 nm PhotoresistsAbsorbance at 157 nm and 193 nm
• Values for Teflon® AF and Values for Teflon® AF and the CO2 synthesized the CO2 synthesized copolymer are very close copolymer are very close and well below 1 and well below 1 mm-1 -1 at at 157 nm 157 nm
• Values at 193 nm are Values at 193 nm are slightly different but both slightly different but both extremely lowextremely low
Sample 157.6 (nm)
193 (nm)
Teflon® AF 0.154 0.004
CO2 Synthesized Copolymer
0.153 0.019
Absorbance [Absorbance [mmOptical Density
0
0.5
1
1.5
2
2.5
145 155 165 175 185 195
wavelength (nm)
(m
-1)
Teflon AF CO2 Synthesized Copolymer
T
Polymer SynthesisCHEM 421
157/193 nm PhotoresistsTeflon® AF as Backbone Material
Protected Functional Monomer
Acidic Group
CF2 CF2 CF CF
OO
CF3F3C
CF2 CF2 CF CF
OO
CF3F3C
PAG
• In order for a Teflon® AF In order for a Teflon® AF derivative to serve as a derivative to serve as a photoresist, a functionalized photoresist, a functionalized monomer that can be monomer that can be cleaved by an acid must be cleaved by an acid must be incorporated into the incorporated into the backbonebackbone
• After cleaving with a photo After cleaving with a photo acid generator (PAG) the acid generator (PAG) the functional monomer will functional monomer will exhibit different solubility exhibit different solubility properties from unexposed properties from unexposed regionsregions
Polymer SynthesisCHEM 421
157/193 nm Photoresists EVE/PDD/TFE Plackett-Burman Experiment Scheme
• Chose to explore Ester Vinyl Ether (EVE) Chose to explore Ester Vinyl Ether (EVE) as a prototype for potential EVE derived as a prototype for potential EVE derived functional monomersfunctional monomers
• Conducted a Plackett-Burman Conducted a Plackett-Burman experimental scheme varying five experimental scheme varying five parameters (composition, initiator parameters (composition, initiator concentration, temperature, pressure and concentration, temperature, pressure and reaction time) to study the reaction of EVE reaction time) to study the reaction of EVE with PDD and TFEwith PDD and TFE
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
CF2 CF2 CF CF
OO
CF3F3C
F2C
O
CF
CF3
O CF2 CF2
O
OCH3
CF CF
poly(TFE-co-PDD-co-EVE)
Polymer SynthesisCHEM 421
157/193 nm Photoresists EVE/TFE/PDD - Absorbance
• Absorbance values at 157 nm increase with increasing EVE Absorbance values at 157 nm increase with increasing EVE content but still remain well below 1 content but still remain well below 1 mm
• Values at 193 nm are very low and vary only slightlyValues at 193 nm are very low and vary only slightly
Sample Composition(mol %)
157.6(nm)
193(nm)
REH-004 7/73/20 EVE/PDD/TFE (Charged) 0.128 0.013
REH-013 12/59/29EVE/PDD/TFE 0.252 0.011
REH-005 18/54/28EVE/PDD/TFE 0.574 0.017
VASE® Absorbance [VASE® Absorbance [mmMeasurementsMeasurements
Polymer SynthesisCHEM 421
Bilayer Resist Processes
Levinson, Harry J. Principles of Lithography. SPIE Press, 2001.
Polymer SynthesisCHEM 421
Top-Surface Imaging
Levinson, Harry J. Principles of Lithography. SPIE Press, 2001.
Polymer SynthesisCHEM 421
Comparisons
Spin coating
Expose
Develop
1st Spin coating
2nd Spin coating
Expose
Develop
O2-RIE
Spin coating
NegativeExposure
Single LayerResist
Top-SurfaceImaged Resist
Bi-LayerResist
O2-RIE
Silylate
Polymer SynthesisCHEM 421“Transitions” in Optical Lithography
365 nm365 nm
248 nm248 nm
193 nm193 nm
157 nm157 nm
E-beamE-beam
X-rayX-ray
EUVEUV
?
Polymer SynthesisCHEM 421
“Advances in Patterning Materials for 193 nm Immersion Lithography”
Chem. Rev. 2010, 110, 321–360
“Organic imaging materials: a view of the future”
J. Phys. Org. Chem. 2000, 13, 767
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