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5th international Symposium on immersion lithography extensions, 22-25 September, The Hague, The Netherlands
Development of Third Generation Immersion Fluids
Based on Dispersion of Nanoparticles
S. Jahromi, L. Bremer, R. Tuinier S. Liebregts
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5th international Symposium on immersion lithography extensions, 22-25 September, The Hague, The Netherlands
ContentContent
• Future of high index immersion: our view.• Why nanoparticles?• Theoretical considerations:
• Maximum achievable refractive index.• Effect of scattering on transmission.
• Experimental results:• Index of composite fluids.• Scattering through dispersion of nanoparticles.• Imaging through dispersion of nanoparticles.• Synthesis of nanoparticles.• Synthesis and dispersion of LuAG
nanoparticles
• Planning• Concluding remarks
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5th international Symposium on immersion lithography extensions, 22-25 September, The Hague, The Netherlands
High index immersion: This is how we at look at it!High index immersion: This is how we at look at it!
• Various cyclic organic compounds have indices of ~1.64 (Gen-2 fluids)!
• The key to transparency is not chemistry but purity!• Technical difficulties (high dn/dt, lens contamination etc)
are manageable, i.e. no potential showstopper.• Current technical hurdle: Lack of high index glasses • Even if there is a high index lens, the future of high index
immersion solely based on Gen-2 fluids is uncertain.
The need for G3 fluids with index~ 1.8
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5th international Symposium on immersion lithography extensions, 22-25 September, The Hague, The Netherlands
Why Why NanoparticlesNanoparticles??
• The limit of index for homogenous organic fluids is at ~1.64!
• Dispersion of nanoparticles
in organic fluids is the only viable way to produce fluids with index of 1.8!
• DSM Started the development of immersions fluids based on nanoparticles
already in 2003: Project Liquid Lens.
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5th international Symposium on immersion lithography extensions, 22-25 September, The Hague, The Netherlands
Technical Target for liquid lensesTechnical Target for liquid lenses
Technical requirementsHIFs
Preferred technical requirements liquid lenses
High transmission, i.e. low scattering Particle size < 5 nm
High refractive Index Particle Loading > 70 wt%
High scanning speed Liquid viscosity < 5 mPas
It’s a challenge!!!
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5th international Symposium on immersion lithography extensions, 22-25 September, The Hague, The Netherlands
What are the issues?What are the issues?
• Theoretical considerations:• Is it theoretically possible to produce a dispersion of high index
nanoparticles
with sufficient transparency (1.5/cm) and index (1.8) for imaging at 193 nm.
• Experimental Considerations:• How does the index of fluid increase with vol% of nanoparticles?• Is imaging through a solution of nanoparticles
possible?
• Is it possible to produce nanoparticles
< 5 nm?• Is it possible to produce DUV transparent nanoparticles
such as LuAG?
• Is it possible to produce stable dispersion of nanoparticles
at high loadings (>50 wt%)?
• Is it possible to keep viscosity low at such high loadings?• Is it possible to develop an in-line recycling system for such dispersions?• What are the implementations issues in a real stepper? (Abrasion,
defectivity
etc.)
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5th international Symposium on immersion lithography extensions, 22-25 September, The Hague, The Netherlands
INDEX: Theoretical Consideration: Maximum INDEX: Theoretical Consideration: Maximum achievable indexachievable index*)*)
• Parameters• Refractive index of the medium• Concentration particles that can be achieved• Refractive index of the particles
• Model• Particles with Van der Waals attraction• Stabilizer layer with minimum thickness Δ
needed to prevent colloidal instability. Based on percolation theory for concentrated dispersions and 2nd
virial
coefficient (Vliegenthart
and Lekkerkerker, J. Chem.Phys., 112:5364, 2000).• Result
• Van der Waals attraction is function of optical properties of particles and medium (Lifshitz).
• Higher density of particles higher index but stronger attraction and lower concentration
• More polarizability higher index and weaker attraction but limited because of deep UV transmission request.
• Calculations based on optical properties of materials that are proven to be transparent; LuAG
and decalin. Calculations on HfO2
.
Δ
*) L. Bremer, R. Tuinier and S. Jahromi:
Submitted to Langmuir.
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5th international Symposium on immersion lithography extensions, 22-25 September, The Hague, The Netherlands
6.5
Density particles
7 7.5
8 9
INDEX: Theoretical Consideration: Maximum achievable INDEX: Theoretical Consideration: Maximum achievable index; index; LuAGLuAG and HfOand HfO22 in water and transin water and trans--decalindecalin
1.6
1.7
1.8
nmax (193
nm)
φ = 0.64
φ = 0.4
φ = 0.3
1.8
1.9φ = 0.64
φ = 0.4
φ = 0.3
nmax (193
nm)
1.7
6.5
Density particles
7 7.5LuAG
8 9 HfO2
WATER
DECALIN•
The volume fraction φ
considers particles + stabilizer layer. Viscosity at φ=0.3 is 6 mPas, at φ=0.4 it is 20 mPas
and at φ=0.64 extremely high.•
Using materials such as LuAG
and HfO2 it should be possible to produce low viscous (<20 mPas) nanoparticle
dispersions with index above 1.8
LuAG HfO2LuAG HfO2
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5th international Symposium on immersion lithography extensions, 22-25 September, The Hague, The Netherlands
SCATTERING: Theoretical considerationSCATTERING: Theoretical consideration
• Scattering theories considering a single particle (Rayleigh, Mie) result in enormous over-estimation of the scattering of concentrated dispersions.
• The static structure factor has been estimated using the Percus
Yevick
approach by Wertheim and Thiele.
M.S. Wertheim, Phys. Rev. Lett. 10 p321 (1963)E. Thiele, J.Chem.Phys. 39 p474 (1963)
( )( )2
4
211)(
φφφ
+−
=S
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5th international Symposium on immersion lithography extensions, 22-25 September, The Hague, The Netherlands
SYNTHESIS: Theoretical considerationTheoretical consideration
• Input parameters:• Index of LuAG
at 193 nm= 2.14• Index of Decalin
at 193 nm= 1.63
• Size of LuAG
particles= 4 nm
Predicted Index and Absorption (/cm) at 193 nm for a dispersion of LuAG nanoparticles in Decalin
1.6
1.65
1.7
1.75
1.8
1.85
1.9
1.95
0 10 20 30 40 50 60
Volume (%)
0
0.2
0.4
0.6
0.8
1
1.2
IndexAbsorption (/cm)
Gen-3 fluids: Index of 1.7-1.8 and absorption< 1.5/cm should be achievable by dispersion of LuAG nanoparticles in Gen-2 fluids!!!
DSM Target Area
5th international Symposium on immersion lithography extensions, 22-25 September, The Hague, The Netherlands
00,20,40,60,8
11,21,41,61,8
0 2 4 6
Diameter (nm)
E(/c
m)
LuAG in decaline79% m/m; 33.3% vol/volRayleigh + PY static structure factor
D = 5.8 nmE = 1.5 /cm
SYNTHESIS: Theoretical consideration: What is the limit of Theoretical consideration: What is the limit of size of size of nanoparticlesnanoparticles??
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5th international Symposium on immersion lithography extensions, 22-25 September, The Hague, The Netherlands
1,61,651,7
1,751,8
1,851,9
1,952
0% 20% 40% 60% 80% 100%
Solids %(m/m)
n(19
3 nm
)Theoretical consideration: Calculation of the turbidity and Theoretical consideration: Calculation of the turbidity and index as a function of weight percentage of index as a function of weight percentage of nanoparticlesnanoparticles
0
0,2
0,4
0,6
0,8
1
Extin
ctio
n /c
m
Blue, 4 nm LuAG
in decaline Red, 4 nm LuAG
with ½
nm stabilizer
Very High Solid Dispersions!!
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5th international Symposium on immersion lithography extensions, 22-25 September, The Hague, The Netherlands
Summary of Theoretical considerationsSummary of Theoretical considerations
• It should theoretically be possible to prepare low viscous dispersions of nanoparticles
with index above 1.8 and
sufficient transparency for imaging at 193 nm.
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5th international Symposium on immersion lithography extensions, 22-25 September, The Hague, The Netherlands
INDEX: How does the index of fluid increase INDEX: How does the index of fluid increase with with volvol% of % of nanoparticlesnanoparticles??
Index of dispersion of ZrO2
nanoparticles
(< 3 nm)in water is measured with ellipsometer.
0)1( nnn D φ−+φ=
Index of liquid lens Vol% of particlesIndex of particles Index of host liquid
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5th international Symposium on immersion lithography extensions, 22-25 September, The Hague, The Netherlands
INDEX: INDEX: EllipsometerEllipsometer Results on ZrOResults on ZrO22 DispersionsDispersions
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5th international Symposium on immersion lithography extensions, 22-25 September, The Hague, The Netherlands
INDEX: Numerical values of index at different INDEX: Numerical values of index at different loading!loading!
Sample n (190.2 nm) N (193.4 nm)
Water 1.4477 1.4403
Water, 5 % ZrO2 1.4881 1.4766
Water, 10 % ZrO2 1.5066 1.4954
Water, 20 % ZrO2 1.5619 1.5274
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5th international Symposium on immersion lithography extensions, 22-25 September, The Hague, The Netherlands
INDEX: Linear relationship between index and INDEX: Linear relationship between index and loading!loading!
1,32
1,33
1,34
1,35
1,36
1,37
1,38
1,39
1,4
0 2 4 6 8 10 12
Volume fraction
nD
corundboehmitzirconia
Scaling between index and volume% of nanoparticles follows the theoretical predication.
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5th international Symposium on immersion lithography extensions, 22-25 September, The Hague, The Netherlands
SCATTERING: Silica SCATTERING: Silica NanoparticlesNanoparticles as model Systemsas model Systems
• We have conduced a series transmission measurement experiments plus actual imaging through these silica dispersions.
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5th international Symposium on immersion lithography extensions, 22-25 September, The Hague, The Netherlands
SCATTERING:SCATTERING: Transmission through a dispersion of silica Transmission through a dispersion of silica nanoparticlesnanoparticles: Comparison of theory with experiments!: Comparison of theory with experiments!
0
100
200
300
400
500
600
700
240 290 340 390Wavelength (nm)
Turb
idity
/m
turbidity + abs (measurement)
Turbidity calculated Rayleigh + S
Dispersion: 16 nm Silica nanoparticles (20wt% in water)
Scattering theory predicts well the transmission up to the point that the system absorb.
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5th international Symposium on immersion lithography extensions, 22-25 September, The Hague, The Netherlands
SCATTERING: Effect of structure factor on scattering!SCATTERING: Effect of structure factor on scattering!
0
500
1000
1500
2000
2500
3000
3500
0 0.1 0.2 0.3 0.4
Volume fraction
Turb
idity t (measurement)
t (Rayleigh)
• Large discrepancy between Rayleigh theory and experiments.• At high loadings scattering decreases because of the effect of
structure factor.
Turbidity measurements on dispersions of silica nanoparticles
with different volume fraction.
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5th international Symposium on immersion lithography extensions, 22-25 September, The Hague, The Netherlands
IMAGING: ProofIMAGING: Proof--OfOf--Principle: Is imaging through Principle: Is imaging through a solution of a solution of nanoparticlesnanoparticles possible?possible?
• Experimental Conditions at ASML in Wilton:• 248 nm Interfering beam immersion.• Resist Process
-
62 nm DUV 30 Bottom anti-reflective coating-
166 nm Sumitomo KX 923 S95 resist-
38 nm TOK TSP-3A Top coat
• Pitch: 260 nm -
130 nm Lines/Spaces
●
Basic feasibility of imaging through a liquid lens was demonstrated based on imaging experiments through a solution of silica nanoparticles
(~16 nm; 20wt%)
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5th international Symposium on immersion lithography extensions, 22-25 September, The Hague, The Netherlands
IMAGING:IMAGING: IImaging in silica dispersion ~16 nm particles (248 maging in silica dispersion ~16 nm particles (248 nm)nm)
DSM Liquid DIL 1-20,Wafer 3206 Distilled Water, Wafer 1426
2t-1b 2-4bResist height: 1488Å Resist height: 1612Å
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5th international Symposium on immersion lithography extensions, 22-25 September, The Hague, The Netherlands
IMAGING: Imaging through dispersion of IMAGING: Imaging through dispersion of nanoparticlesnanoparticles: Main findings!: Main findings!
• Imaging through dispersion of nanoparticles was successfully preformed.
• No handling or process problems were encountered.
• Resist profiles were acceptable but some top loss due to small light scattering was observed.
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5th international Symposium on immersion lithography extensions, 22-25 September, The Hague, The Netherlands
50 nm
ZnOZnO with Cwith C55 --COOHCOOH
PARTICLE SYNTHESIS: Is it possible to produce nanoparticles < 5 nm?
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5th international Symposium on immersion lithography extensions, 22-25 September, The Hague, The Netherlands
• A) Crystalline Al2 O3 with an index of ~ 1.9
• B) Magnesium oxide (MgO) with an index of 2.0
• C) Magnesium aluminium oxide (MgAl2 O4 ) with an index of 1.8
• D) Garnets (LuAG) with index of 2.14 (our main target).
Requirements are similar to those as used for high index glasses, i.e. combination of high index and high transparency: The candidates are:
Do not forget quantum effects (HfO2 )!!
PARTICLE SYNTHESIS: What are the candidate materials?
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5th international Symposium on immersion lithography extensions, 22-25 September, The Hague, The Netherlands
PARTICLE SYNTHESIS: Quantum effect TiOQuantum effect TiO22 : Effect of : Effect of Particles size (1)Particles size (1)
Without modifier Modified particles
Without modifier 20 nmModified particles 5 nm
Particle size
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5th international Symposium on immersion lithography extensions, 22-25 September, The Hague, The Netherlands
00.10.20.30.40.50.60.70.80.9
200 400 600 800波 長 (nm)
吸光
度 (-
) 30 nm TiO2
particles
5 nm TiO2
particles
Blue shift
Wavelength (nm)
Abs
.
PARTICLE SYNTHESIS: Quantum effect TiOQuantum effect TiO22 Effect Effect of Particles size (2)of Particles size (2)
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5th international Symposium on immersion lithography extensions, 22-25 September, The Hague, The Netherlands
PARTICLE SYNTHESIS: Different approaches to produce Different approaches to produce nanoparticlesnanoparticles ..
Top Down
Bottom up
Nanoparticles
• Grinding down to nanosize.• DSM’s
conclusion: Grinding is possible but
contamination is too high!!
• Preparation from solution of precursors.• DSM’s
conclusion: Preferred method!! Offers
best chance of success!!
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5th international Symposium on immersion lithography extensions, 22-25 September, The Hague, The Netherlands
PARTICLE SYNTHESIS: What are the considerations when What are the considerations when developing dispersion of developing dispersion of nanoparticlesnanoparticles as immersion fluids?as immersion fluids?
• Design of nanoparticles
for dispersion in organic solvents. Steric
stabilization (in water charge stabilization is valid)
5nm particlesof the right
material
Transparent linking unit
As short as possible tail (<1 nm)
We have developed a method to produce and disperse LuAG in decaline!!
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5th international Symposium on immersion lithography extensions, 22-25 September, The Hague, The Netherlands
10 nm
100 nm
50 nm
Decalin
water
PARTICLE SYNTHESIS: Is it possible to synthesis LuAG nanoparticles and disperse them in decaline?
• 10 nm LuAG particles have been produced and successfully dispersed in decaline.
10 20 30 40 50 60 70
2θ10 20 30 40 50 60 70
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5th international Symposium on immersion lithography extensions, 22-25 September, The Hague, The Netherlands
Timing: Production of GenTiming: Production of Gen--3 fluids based on 3 fluids based on nanoparticlesnanoparticles..
• The roadmap consists of three phases:
Phase 1: Proof-of Principle- Deliverable: Produce gram quantityof Gen-3 fluids for imaging at 193 nm.- Timing: Q2-09
Phase 2: Pilot line- Deliverable: Set up a pilot line to produce kg quantity of Gen-3 fluids.- Timing: Q2-2010
Phase 3: Upscaling- Deliverable: Set up a production line (Tons) for Gen-3 fluids.- Timing: Mid 2011
Significant allocation of resources is needed especially for phases 2 and 3.
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5th international Symposium on immersion lithography extensions, 22-25 September, The Hague, The Netherlands
ConclusionsConclusions
• Dispersion of nanoparticles
is the only way of producing Gen-3 fluids.
• Theoretical consideration have shown that it should be possible to produce low viscous Gen-3 fluids with sufficient transparency for imaging at 193 nm.
• Experimental results on scattering and index support the theoretical findings.
• Imaging through dispersion of nanoparticles
have been demonstrated.
• Nanoparticles
of LuAG
have been prepared and successfully dispersed in decaline.