Cost Effective Single Exposure Immersion Lithography … French... · Immersion Lithography With...
Transcript of Cost Effective Single Exposure Immersion Lithography … French... · Immersion Lithography With...
Cost Effective Single Exposure Immersion Lithography
With Second Generation Immersion Fluids For Numerical Apertures of 1.55
and 32 nm Half Pitches
R. H. French1, H. V. Tran1, D. J. Adelman1, N. S. Rogado1, W. Qiu1, J. Feldman1, O. Nagao2, M. Kaku2, M. Mocella3, R. C. Wheland1, M. K. Yang1,
M. F. Lemon1, L. Brubaker1, B. Fones1, B. E. Fischel1, C. Y. Chen4
1. DuPont Co. Central Research, Wilmington DE, 19880-04002. DuPont K. K., NBD-J, Utsunomiya-shi, Japan 321-32313. DuPont Co., Electronic Technologies, Wilmington DE, 198804. DuPont-EKC, Hayward CA, 94545
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Acknowledgements
MIT Lincoln Labs•Vlad Liberman•Keith Krohn•Mordy Rothschild
IMEC•E. Hendrickx, R. Gronheid,
Previous Work: • SPIE Proceedings on Optical Microlithography XVII, SPIE Vol. 5377-173, (2004). • Journal of Vacuum Science And Technology B, 22, 6, 3450-3, (2004). • SPIE Proceedings on Optical Microlithography XVIII, ML5754-76, (2005).• Journal of Microlithography, 4, 3, 031103, (2005). • SPIE Proceedings on Optical Microlithography XIX, ML6154-42, (2006). • SPIE Proceedings on Optical Microlithography XX, ML6520-59, (2007).
NIST•Simon Kaplan•John Burnett
Sematech•Bryan Rice
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Introduction
Three Elements For High Index Immersion•High Index Immersion Fluids With Recycle Technology •High Index Last Lens Element (HILLE)•High Index Scanners
Single Patterning With High Index Immersion Lithography• Intrinsically Lower Cost Of Ownership
•Versus Double Patterning With Water•Current Technological Gate Due To HILLE
Development Of Immersion Fluids And Active Recycle•Optimize High Index Immersion Imaging Performance•Minimize High Index Immersion Defectivity
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Outline
High-n Immersion Imaging and Defectivity•Leaching And Residues
Fluid Lifetimes and Daily Fluid Dose
Radiation Durability•Three Gen2 Immersion Fluids•Active Recycle Ver. 3 & 4 Performance
Conclusions
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High Index Immersion Fluids
193 nm Index• IF173: 1.679*• IF175: 1.664• IF169: 1.655• IF132: 1.644• IF131: 1.639• IF137: 1.638
Rad. Dur. Test Of Three Fluids• IF137, IF132, IF169• Compare Radiation Durability Of Different High-n Fluids
Current High Index Fluid Candidates
1.45
1.5
1.55
1.6
1.65
1.7
190 290 390 490 590Wavelength (nm)
Inde
x of
Ref
ract
ion
"n"
IF173-12015IF175-12107IF169-12722IF132-12790IF131-12610IF137-12022
IF173: extrapolated index at 193 and 206 nm
**
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Gen2a Type Immersion Fluid Candidates 193 nm Index• IF173: 1.679*• IF175: 1.664
• IF132: 1.644
Define Gen2a Fluids • Indices > 1.66
Current Optical Abs.
IF175• Abs/cm ~2/cm
IF173• Abs/cm >20/cm
Increased Numerical Aperture Possible• With A High Index Last Lens Element• And A Gen2a Fluid
But May Require Relaxed Absorbance Specification
1.45
1.5
1.55
1.6
1.65
1.7
190 290 390 490 590Wavelength (nm)
Inde
x of
Ref
ract
ion
"n" IF173-12015
IF175-12107IF132-12790
* IF173: extrapolated index at 193 and 206 nm
**
High Index Immersion Imaging and Defectivity
PAG Leaching
Materials Of Construction, Filters
Residues: Particles and Film Formers
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Issues In High Index Lithography: IF Lifecycle
Image Formation
High-n Imaging High-n Defectivity
From Immersion Fluid
From 193nm Laser Irradiation
Materials In Contact With IF:
Soluble: Film Former
Insoluble:Particles
Optical Absorbance
Impact
Source
Define Controlling Factors In High-n Imaging And Defectivity
Optimize Active Recycle To Address These High-n Immersion Issues
Fluid Handling System
Image Formation
High-n Imaging High-n Defectivity
Initial ProductionFrom Immersion Fluid
With Oxygen UptakePhotochemical Degradation
From 193nm Laser IrradiationFilters
Materials Of ConstructionResist PAG, Base
Materials In Contact With IF:
Soluble: Film Former
Insoluble:Particles
Optical Absorbance
Impact
Source
PossiblePossiblePossiblePossibleFluid Handling System
Possible
PossiblePossible
Possible
Image Formation
High-n Imaging High-n Defectivity
PossiblePossiblePossibleInitial ProductionFrom Immersion Fluid
PossiblePossibleWith Oxygen UptakePossiblePossiblePhotochemical Degradation
From 193nm Laser IrradiationPossiblePossiblePossibleFilters
PossiblePossibleMaterials Of ConstructionPossiblePossibleResist PAG, Base
Materials In Contact With IF:
Soluble: Film Former
Insoluble:Particles
Optical Absorbance
Impact
Source
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DuPont Joint
Leaching – Matching of Leaching MethodsProtocol Established With IMEC
Match The Analytical Methods•All Samples Were Split In Half•The Analysis Was Done At DuPont And At RIC (IMEC Analytical Lab)
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Leaching – PAG From PAR-817 Into Water / HILUnexposed PAG Leaching•Good Reproducibility At Two Sites
More Leaching Into Water, Than Into IF132 Or IF169PAG Leaching into Fluids at 6 Minutes
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
9.00
Water IF132 IF169
Fluid
Det
ecte
d PA
G (m
ol/m
L x
10-1
0 )
DuPont (MS/MS Method)IMEC (SIM Method)
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Leaching – PAG From PAR-817 Into IF132Good Repeatability• Each Bar Represents Average Of 5 Runs
Leaching Occurs Within First MinuteLevels Well Below Stepper Manufacturer PAG Limits
0.00
0.50
1.00
1.50
2.00
2.50
0 1 3 6Time (min)
Det
ecte
d PA
G (m
ol/m
L x
10 -1
0 )
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Residues Can Arise From Droplet Drying
Sources Of DefectivityFrom Fluid
•Soluble Impurities From Fluid (a)From Stepper
•Materials Of Construction • Insoluble Particles In Fluid (b)•Filters (c)•Photoresist• Irradiated byproducts•Resist / topcoat contaminants
Optical Images: Olympus LEXT Laser Confocal Microscope
Types of Residuing Seen From High Index Fluids
Initially Clean Fluid For Use
(a)
Active Recycle For In-Situ Cleaning
(b) (c)
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PTFE Pipe Tape : Absorbing, Not Film Former
Need To ControlFluid Contamination•From Materials Of Construction
Increases In Opt. Abs.•Can Degrade Imaging
•By High NA Apodization
Optical Absorbance Increased Due To Contact
But No Film Forming Residues Were Introduced
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PTFE Pipe Tape : Absorbing, Not Film Former
Need To ControlFluid Contamination•From Materials Of Construction
Increases In Opt. Abs.•Can Degrade Imaging
•By High NA ApodizationBefore Pipe Tape After Pipe Tape
Optical Absorbance Increased Due To Contact
But No Film Forming Residues Were Introduced
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Filters: Film Former, Yet Optically Transparent
Clean Fluid• Initially
PTFE Filter•Recirculate InFluid Handling System
Reduced Particles
Constant Abs/cm
No Increase In Optical Absorbance
But Film Formation Seen•Some Filters Also Cause Increased Optical Absorbance
No Residue Seen•Of 1mm Fluid Droplet
Film Forming Residue Seen•Of 1mm Filtered Fluid Droplet
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Filters: Film Former, Yet Optically Transparent
Clean Fluid• Initially
PTFE Filter•Recirculate InFluid Handling System
Reduced Particles
Constant Abs/cm
No Increase In Optical Absorbance
But Film Formation Seen•Some Filters Also Cause Increased Optical Absorbance
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Droplet Test Conditions
Droplet Dispense• 1-2 mm Diameter Fluid Droplet Dispensed Onto Bare Si Wafer• With A Clean Plastic Pipette
Droplet Evaporation• Droplet Evaporated By Baking At 100C To 400-500 um In Diameter
Confocal Microscope Analysis• Droplet Evaporation Monitored Under Microscope• Time Sequential Images Taken Of Droplet Evaporation At Room Temperature• For Some, Final Residue Baked At 100C For 1 min• Final Image Taken
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Heavier Particles Drop Out First During Evaporation
Soluble Contaminants Left Over In Center
Defectivity From Contaminated Fluid
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Film Forming Residues And Particles in Dirty Fluid1-2 mm
Diameter Droplet Of Dirty Fluid Evaporated On Bare Si Wafer
Particles Left Behind Along Edges And On Center Of Drying Droplet
Film Forming Residues Left In Center
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Cleaner Fluid1-2 mm
Diameter Droplet Of Cleaner Fluid Evaporated On Bare Si Wafer
No Particles Or Films Left Behind At Edges Of Drying Droplet
Still See Some Particle Collection In Center –Requires Further Optimization
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IF132 Drying on 150 nm PAR-817 Resist FilmIF132 Droplet
Dispensed On 150nm PAR-817
Worst Case Scenario: No Topcoat, Unmatched Resist And Fluid
Component Extraction From Film Leaves Stains On Film As Fluid Dries At Room Temp
Dried Center Shows Residuing
Baking At 100C Makes Residue Disappear
Fluid Lifetimes and Daily Fluid Dose
Factors Which Determine Fluid Lifetime
High Index Immersion Exposure Doses
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Factors Which Determine Fluid Lifetimes
Fluid Lifetime Determined By Many Stepper and Lithography Factors• e.g. Fluid Dose Of 193 nm Laser Radiation, Contaminants From Resist Exposure, etc.
System Design And Lithography Process Definition Required• For Quantitative Fluid Lifetimes
Contamination From UseResist Exposure
Materials Of ConstructionPhotodegradation, Oxygen
Stepper Design ParametersFluid Layer Thickness
Liters Of Fluid In PackageFluid Dose
Fluid Specification LimitsMaximum Absorbance Spec
Index Variation
Fluid Lifetime In Use
Wafer Level CharacteristicsResist Sensitivity
Clear Or Dark Field Level
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Expose A Day’s Wafers: What Is The Delivered Dose?
“Stepper Down” Perspective• Using Standard Stepper Tool1
• 6 kHz Laser• 0.8 mJ/cm2/pulse Laser• 28mm x 7 mm x 3mm Irradiated Volume
• 1.568 mJ/pulse• 0.5 Duty Cycle
Total Daily Dose = 406 kJ/Day
Fluid Dose Is 1.2 J/cm2
• For 3 mm Fluid Thickness• And 100 liter Reservoir
Real Values Dependent On Many Factors• Clear Field Or Dark Field Mask, Wafers/Hour, Resist Sensitivity, etc.
Since Stepper And Lithography Process Are “Owned” By Others• We’ll Use Relative, or Comparative Basis For Fluid Lifetimes
“Wafer Up” Perspective• For A Resist Sensitivity Of 30 mJ/cm2• 3000 Wafers Per Day• 300 mm Wafers
Total Daily Dose = 64 kJ/Day
Fluid Dose Is 0.2 J/cm2
• For 3mm Fluid Thickness• And 100 Liter Reservoir
1. SPIE Proceedings on Optical Microlithography XX, ML6520-59, (2007).
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Schematics of Fluid Recirculation System
The Induced Absorbance Aindcell
•Of The Exposure Cell
Two Critical ContributionsAind
fluid : Induced Fluid Absorbance •Measured Downstream In Spectrometer Cell
Aindwindow : Induced Window Absorbance
Flow Rate 115 ml/min•=> 1 l/min Stepper Flow Rate
Energy Density: 0.8 mJ/cm2
fluidind
windowind
cellind AAA +=
Flow
Laser
VentN2
N2
Pump
Fluid Cylinder
Spectrometer Cell
Laser Exposure Cell
Active Recycle Package
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0
0.05
0.1
0.15
0.2
0.25
0 0.2 0.4 0.6 0.8 1Fluid Dose (J/cm2)
Indu
c. F
luid
Abs
/cm IF169
IF137IF132
3 Fluids, No ARP: Comparative Radiation Durability
Relative DifferencesIn Radiation Durability•Set IF169 = 1
IF137: 2.5X Increased•Radiation Durability
IF132: 48X Increased•Radiation Durability
Radiation Durability Test Conditions•All Fluids Had Comparable Absorbances: ~ 0.09/cm•Two Samples Of Each Fluid Tested•No Active Recycle Used
Different Gen2 Fluids Show Very Different Radiation Durabilities
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Compare IF132 Active Recycle Performance
Radiation Durability Testing With•No ARP, Version 3 ARP, Version 4 ARP•5 Replicates, 15 Total Experiments
Exposure Time Chosen To Supply
Average Fluid Dose = 8.4 J/cm2
•14 Days Of Fluid Usage •At 0.6 J/cm2 Daily Fluid Dose
Average Window Dose = 18 kJ/cm2
•Approximately 1 Day Of Use In Scanner
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00.050.1
0.150.2
0.250.3
0.350.4
0.450.5
0 1 2 3 4 5 6 7 8 9 10
Fluid Dose (J/cm2)
Indu
c. F
luid
Abs IF169 No ARP
IF137 No ARPIF132 No ARPIF132 Ver. 3 ARPIF132 Ver. 4 ARP
No ARP
With ARP
00.050.1
0.150.2
0.250.3
0.350.4
0.450.5
0 1 2 3 4 5 6 7 8 9 10
Fluid Dose (J/cm2)
Indu
c. F
luid
Abs IF132 No ARP
IF132 Ver. 3 ARP
IF132 Ver. 4 ARP
No ARP
With ARP
IF132 Active Recycle: Fluid Life
Relative DifferencesIn Radiation Durability•Set No ARP = 1
ARP Version
Ver. 3: 3X Increased•Radiation Durability
Ver. 4: 9X Increased•Radiation Durability
Induced Fluid Absorbance Rate•Fit With Simple Linear Model•Observe Sub-linear Increase In Absorbance
Average 5 Radiation Durability Experiments
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0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
0.04
0 2 4 6 8 10 12 14Window Dose (kJ/cm2)
Indu
c. W
indo
w A
bs
IF132 No ARP
IF132 Ver. 4 ARP
IF132 Active Recycle: Window Life
0.01 Abs / Window•With Ver.4 ARP•After 14 kJ/cm2
2.3% Trans. Drop
Not Optimal Window Test •Dose ~1 Day Window Use
But In This Test•Only 1 liter Of Fluid•So Fluid Absorbance
Climbs During Test
Induced Window Abs. For Two WindowsLow Window Contamination Below 6 kJ/cm2
•Suggestive Of Incubated Process
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ConclusionsHigh Index Immersion Lithography Status• High-n Fluid and Active Recycle: Good• High-n Last Lens Element: ?
•Awaiting LuAG, BaLiF, etc.• High-n Scanners Status: Await Announcement
High-n Immersion Imaging and Defectivity• PAG Leaching Low• Materials Of Construction, Filters
•Can Cause Absorbance Increases, Removed By Active Recycle•Film Forming Residues, Avoided By Proper Materials Choices
• For Droplets Which Dry On Wafer
Radiation Durability Of Different High-n Fluids• Can Vary Dramatically
IF132 Active Recycle Ver. 4 Has Improved Performance• 9X Increase In Fluid Lifetime Compared To No ARP• Window Contamination Exhibits Incubation Period
Active Recycle Important For Reduced Window Contamination