Development of Third Generation Immersion Fluids Based · PDF fileDevelopment of Third Generation Immersion Fluids ... Based on percolation theory for concentrated dispersions and

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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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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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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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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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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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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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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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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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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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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


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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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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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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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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INDEX: INDEX: EllipsometerEllipsometer Results on ZrOResults on ZrO22 DispersionsDispersions

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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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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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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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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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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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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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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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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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50 nm

ZnOZnO with Cwith C55 --COOHCOOH

PARTICLE SYNTHESIS: Is it possible to produce nanoparticles < 5 nm?

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• 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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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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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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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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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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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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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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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.

Documents

Development of Third Generation Immersion Fluids Based · PDF fileDevelopment of Third Generation Immersion Fluids ... Based on percolation theory for concentrated dispersions and