Lithography Optics Division
Optics for EUV Lithography
Peter Kürz, Thure Böhm, Stephan Müllender, Wolfgang Bollinger, Manfred Dahl, Martin
Lowisch, Christian Münster, Frank Rohmund, Thomas Stein, Erik Louis, Fred Bijkerk
Lithography Optics Division
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Design example
A collector module has been qualifed and is usedto test the illuminator at wavelength.
The early projection opticsis in the qualification phase
EUV alpha demo tool: Status at Zeiss
Key specificationsλ 13.5 nm NA 0.25Resolution 50 nmfield 26x33 mm2
Magnification 4x
One illuminator hasbeen qualified
and the secondis in process
N. Harned et al: this conference
Lithography Optics Division
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Illuminator
All mirrors have beenfabricated and coated
EUV qualification has beenfinished
System fully assembledand aligned
Lithography Optics Division
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EUV qualification: hardware
@ λ illuminator metrology tool
„reticle stage“ for metrology
Lithography Optics Division
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Camera
Lens
Metrology Reticle
Scintillator
Vacuum window
EUV Radiation
Scales, Markers
Reticle Stage
Metrology
EUV qualification: Results (1)
Magenta lines: circles around optical axis
Stitching of 3 Images
Ring field measurement
Lithography Optics Division
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EUV qualification: concept for field and pupil qualification
Camera
Lens
Metroloty Reticle, Pinhole
Telecentricity Screen
Vacuum window
Reticle Stage
Setup for Pupil Qualification
Metrology-Reticle
Slit + Filter +EUV-Photodiode Field
Scanning field with slit EUV photodiode. Integration in y-direction.
Setup for Field Qualification
Lithography Optics Division
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Uniformity EUVL-Source+SoCoMo+IlluMo, 21. Sept. 2005, 09:40
0.95
0.96
0.97
0.98
0.99
1
1.01
1.02
1.03
1.04
1.05
-60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60
x @ Reticle (mm)
Nor
mal
ized
Inte
nsity
measured uniformity at recticleplane < 2.5 %
Pupil: Telecentricity < 0.5%Ellipticity < 10% (calculated value for Sn source)
EUV qualification: Results (2)
Lithography Optics Division
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Projection Optics Box
reticle
wafer
Status:• all mirrors fabricated and coated
• assembly complete
• system metrology has been set up
• the POBox is in the qualification phase
Design example
Lithography Optics Division
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Status POBox: System Metrology
POBox test lens on system inteferometer
System Metrology for POBox alignment/qualification has been set up
Lithography Optics Division
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Early POBox: Alignment Status
Status today: - POBox is in the final qualification phase
Performance prediction:- 50 nm dense lines can be printed with the early POBox
248nm illumination (*converted by phosphor screen): image of the reticle mask in the wafer plane
July 22: first light
Lithography Optics Division
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2D-isotropic PSD
Errors … causes ….:
Challenge: reach about 0.2 nm rms for Figure, MSFR and HSFR simultaneously
Lateral Frequency [μm-1]
figure aberrations
Figure
MSFR Flare, contrast
in field of view scattering
MSFR
Optics Technology (1): Fabrication of EUV mirrors
HSFR reflectivity
HSFR
Lithography Optics Division
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Main challenge: flare reduction
( )2
24 ⎟⎟⎠
⎞⎜⎜⎝
⎛=
λπ surfacerms
TIS
Due to the very small wavelength EUV imaging is sensitive to scatter !!!
Total integrated scatter
2surfacemirrors rmsnTIS ⋅∝
Reduction of mid spatial frequency rms is essential to reduce the flare level
Lithography Optics Division
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flare reduces overlapof process windowsdue to dose offsets
proximity effects in dependence of thelocal reticletransmission
largest impact of flare on isolatedfeatures on bright-field masks
sensitivity of CD to dose errorsbecomes larger
Dose-to-targetchange
No flareWith flare
Main challenge: flare reduction
CD
Intensity cross-section
Lithography Optics Division
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0
5
10
15
20
25
early POB AD 1 AD 2 productiontool
flare
[%]
Flare roadmap
target
Lithography Optics Division
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MSFR at fine figuring processes
0.15
0.17
0.19
0.21
0.23
0.25
0 20 40 60 80 100 120
relative material removal / %
MSFR
/ %
EUV mirror fabrication: Process development
Critical process step: Fine Figuring
Relative material removal: 100% is representative for reaching figure spec on alphademo tool mirror
technology to reach MSFR of ≤ 0.2 nm rms on alpha tool mirrorshas been established (16% flare tool)
Mirror for 16% flare tool: M1 - 0.19 nm
MSFR = 0.2 nm rmsnm
Lithography Optics Division
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Learning curve – mid spatial frequency roughness
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
2000 2001 2002 2003 2004 2005 2006 2007 2008 2009
MSF
R [n
m rm
s](e
valu
ated
over
4.6
deca
des)
test mirror
Set 3
Set 1
Set 2
test mirror(MSFR opt.)
MET AD
early POBmirrors
M116% flare
production tool target
23 % flare
6% flare
Lithography Optics Division
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Optics Technoloy (2): Coatings
Recent developmentat FOM
xy
A complete set of alpha tool mirrorshas been coated at FOM…
… and ZeissNew capping layer:
reflectance 68.5%comparable to uncapped multilayer
New capping layer:reflectance 68.5%comparable to uncapped multilayer
0%
10%
20%
30%
40%
50%
60%
70%
12.8 13 13.2 13.4 13.6 13.8 14
Wavelength [nm]
Ref
lect
ance
@ 1
.5 º
E. Louis et al: this conference
Lithography Optics Division
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• alpha tool program is progressing:• illuminator
• alignment and EUV qualification has been finished• POBox
• all mirrors have been fabricated and coated• system metrology for the POBox is operational• the POBox has been assembled and is in the qualification phase
• technology development• 16% flare capability has been demonstrated on AD tool mirrors• new high reflectivity cap layer has been developed
Summary
EUV Optical Technology at Carl Zeiss SMT AG: has reached α-tool specsis progressing towards production tool capability
Lithography Optics Division
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Thanks to a huge team effort at…
• FOM-Rijnhuizen• TNO TPD• PTB-BESSY• Philips• The teams at ASML and Zeiss• …and many others
Part of this work was supported by:
Acknowledgment
Bundesministerum für Bildung und Forschung Projekt „Grundlagen der EUV-Lithographie“ 13N8088, MEDEA Project „EXTATIC“ and European Commission Project 507754 „More Moore“
Lithography Optics Division
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