Water for Immersion Lithography - SEMATECH

Water for Immers

M. Switkes, V. Liberma
Lincoln L

Massachusetts Inst
Lexington,

sion Lithography

an, and M. Rothschild
Laboratory
titute of Technology

, MA 02420

MIT Lincoln Laboratory

Out

• Water treatment

– The symptoms

Differences among “DI” water
Water storage
Residue on optical surfaces

– The causes

“Total organic carbon”
Other organics
Gas content
Particulates

– MIT/LL water treatment

• Water–optic interaction
• Bubbles
• Alternative fluids

Immersion Workshop
MS 27 Jan. 2004

tline

rs

MIT Lincoln Laboratory

“DI” is No
Transmissio

Source

ot Enough:
on Variations

A

“DI” is No
Residue on Op

Immersion Workshop
MS 27 Jan. 2004

ot Enough:
ptical Surfaces

MIT Lincoln Laboratory

“Total” Orga

(/s
#X(X/X

anic Carbon

4/#

Other Water Q

• Gas content

– Bubble control
– Flow in small

channels

• Particulates

– Deposition on wafer
– Flare

• Temperature control

– Index stability

Immersion Workshop
MS 27 Jan. 2004

Quality Issues

Gas/Vacuum

300 nm

MIT Lincoln Laboratory

Out

• Water treatment

– The symptoms
– The causes
– MIT/LL water treatment test

Components
Troubleshooting

• Water–optic interaction
• Bubbles
• Alternative fluids

Immersion Workshop
MS 27 Jan. 2004

tline

tbed

MIT Lincoln Laboratory

#ITY

ment Testbed

Ultra-pure 10–30 ppb O2

17.6 MΩ 17.6 MΩ
1.5 ppb OOC < 1 ppb OOC

ERVOIR -ILLI
1
$EGAS

Water Treatm

#ITY
7ATER

-ILLI
1ment Testbed
$EGAS
ERVOIR

Water Treatm

Bare fused silica after !BSORBANCE

ment Issues

nonvolatile
liquid droplets

Water Treatme

• Close collaboration with

Mykrolis

• Careful measurements of

resistivity, OOC, and
nonvolatile residue (NVR) at
each stage of the purification

• One component seems to

have been the major source
of contamination

• NVR and OOC now < 1 ppb

each

• 48 h in flowing water leaves

windows clean

Immersion Workshop
MS 27 Jan. 2004

ent Solutions?

MIT Lincoln Laboratory

Out

• Water treatment
• Water–optic interaction

– Dark interaction

Water and bare CaF2
Protective coating

– Long-term exposure testbed

• Bubbles
• Alternative fluids

Immersion Workshop
MS 27 Jan. 2004

tline

d

MIT Lincoln Laboratory

Water–Optic

Bare C

pre-soak 2 hours

c Interaction

CaF2 7 days in H2O

in H2O

Water–Optic

pre-soak 100 nm
on Ca

2 hours

c Interaction

SiO2 7 days in H2O
aF2

in H2O

Water–Optic Inte

#ITY

eraction Testbed

ontaminant
optional)

Metrology

in-situ ex-situ

actinic microscopic/
transmission photographic
inspection
spectroscopic
transmission AFM
profiling
XPS

FTIR

small-spot
spectroscopic
ellipsometry
with profiling

MIT Lincoln Laboratory

Water–Optic Inte

laser output
exposure/
metrology

Immersion Workshop
MS 27 Jan. 2004

eraction Testbed

MIT Lincoln Laboratory

Exposure/Metro

UV-Vis lamp
ellipsometer
in

from laser

ellipsometer cell
out

Immersion Workshop
MS 27 Jan. 2004

ology Chamber

water in/out

to
l spectrometer

MIT Lincoln Laboratory

Cell for Long T

38x3 m
2 mm w

adapted from a design by
John Burnett, NIST
and from Harrick Scientific Corp.

Immersion Workshop
MS 27 Jan. 2004

Term Exposure

mm windows
water gap

• all stainless steel construction
• teflon-coated o-rings
• teflon (PTFE & PFA) fittings
• solvent and O2 plasma cleaned

MIT Lincoln Laboratory

First Results on

200 nm SiO2 coating on CaF2
deposited in house
~750 M pulses at
~3 mJ/cm2/pulse

N2

H2O

Immersion Workshop
MS 27 Jan. 2004

n Lincoln Coating

MIT Lincoln Laboratory

Out

• Water treatment
• Water–optic interaction
• Bubbles

– Nanobubbles
– Resist outgassing

• Alternative fluids

Immersion Workshop
MS 27 Jan. 2004

tline

MIT Lincoln Laboratory

Nano-B

§M

underwater AFM

J. W. G. Tyrrell and P. Attard,
Phys. Rev. Lett. 87, 176104/1 (2001).

Immersion Workshop
MS 27 Jan. 2004

Bubbles

Rapid Cryofixatio

"UBBLE (/
#U 3I

,.

0T#

with J. Ruberti gas-satu
Cambridge Polymer Group hydroph

Immersion Workshop
MS 27 Jan. 2004

on/Freeze Fracture

gas-saturated water
hydrophobic surface

degassed water
hydrophobic surface

urated water
hilic surface

MIT Lincoln Laboratory

Resist Outgassi

• Lens contamination less like

lithography

– Outgassing products diffus
~1000 times slower in water

– With 10x smaller gap, diffus

• Outgassed resist componen

significant changes in liquid

• Peak transient outgassing r

limits in the immersion fluid

– Hydrophobic organics exhib
– Calculations show outgassi

high end of current outgass

• Outgassing requirements will be

– No longer focused on photoc
– Driven by flux and product so

Immersion Workshop
MS 27 Jan. 2004

ing in Immersion

ely than in conventional

se across the same lens–wafer gap
r than in gaseous ambient
sion time still 10x greater in water

nts not likely to induce
d index (< 1 ppm)
rates could exceed solubility
d

bit solubility of 0.1–500 µg/cm3
ing could exceed 100 µg/cm3 for
sing rates
e different
contamination
olubility

MIT Lincoln Laboratory

Impact of Microbubb

bles on Lithography

%XPOSURE

Modeling Outgassin

Isobutene in Resist


;)SOBUTENE=

ng Product Concentration

;)SOBUTENE=