development status of euv wavefront metrology system...
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1EUVL Symposium, October 31, 2007, K. Murakami
Development status of EUV wavefront Development status of EUV wavefront metrology system (EWMS)metrology system (EWMS)
October 31, 2007
Katsuhiko Murakami, Katsumi Sugisaki, Masashi Okada, Katsura Ohtaki, Zhu Yucong, Zhiqian Liu, Jun Saito, Chidane Ouchi, Seima Kato,
Masanobu Hasegawa, Takayuki Hasegawa, Hideo YokotaEUVA
Masahito NiibeUniversity of Hyogo
Mitsuo TakedaUniversity of Electro-Communications
2EUVL Symposium, October 31, 2007, K. Murakami
OutlineOutline
Introduction
EUV wavefront metrology methods
EUV wavefront metrology using EWMS
Summary
3EUVL Symposium, October 31, 2007, K. Murakami
IntroductionIntroduction
EUV wavefront system (EWMS) was developed by EUVA in NEDO project.
We have developed EUV wavefront metrology methods using EUV experimental interferometer (EEI). These metrology methods were applied to EWMS. We have obtained the first EUV wavefront data of full-field projection optics using EWMS with DTI (digital Talbot interferometry) method.
Non-EUV wavefront metrology systems installed in the factories will be used in the manufacturing of EUV lithography tools. EWMS will play an important role as a standard system of EUV wavefront metrology.
4EUVL Symposium, October 31, 2007, K. Murakami
Wavefront of high NA (0.25) full-field projection optics can be measured.
Concept of EUV wavefront metrology system (EWMS)Concept of EUV wavefront metrology system (EWMS)
grating
stage
CCD
vacuum chamber
pinhole/window
PO-boxholder
pinhole
stage
vibration isolator
vacuum pump
metrology frame
EUV light(provided fromSR undulator) PO-box
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Difficulties and solutions of EUV wavefront metrologyDifficulties and solutions of EUV wavefront metrology
No coherence light sourceCommon-path type interferometer
Limitation of optical elementsSimple interferometer design using pinholes and gratings
Extremely high accuracy requiredNo mechanical reference surface
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Principles of interferometers using EUV radiationPrinciples of interferometers using EUV radiation
Test optic
WindowsCCD
(b) CGLSI (c) DTI
1st Pinhole
Grating
CCDCCD
1st Pinhole
Window and2nd Pinhole
Grating
(a) PDI
Point Diffraction Interferometer Shearing Interferometer
7EUVL Symposium, October 31, 2007, K. Murakami
EUV experimental interferometer (EEI) at New SubaruEUV experimental interferometer (EEI) at New Subaru
Clean chamberEEI
Illuminator(NA:0.01) EUV beamline
Test optics
EUV beam
Inside of EEI
Entire view of EEI
8EUVL Symposium, October 31, 2007, K. Murakami
EUV interference fringes obtained with EEI EUV interference fringes obtained with EEI PDI
DTICGLSIDLSI
SLSILSILDI
EUV interference fringes were obtained for 7 different wavefront metrology methods.
9EUVL Symposium, October 31, 2007, K. Murakami
(a) PDI (b) LDI (c) CGLSI (f) DLSI(e) LSI1.29 nmRMS 0.95 nmRMS1.26 nmRMS 1.52 nmRMS1.21 nmRMS
(d) DTI
1.20 nmRMS
Diffraction typeinterferometers
Shearing typeinterferometers
Measured EUV wavefront using EEIMeasured EUV wavefront using EEI
EUV wavefront was measured using 6 different metrology methods.Good agreement between deferent metrology methods.
10EUVL Symposium, October 31, 2007, K. Murakami
EUV wavefront metrology system (EWMS)EUV wavefront metrology system (EWMS)
3.8m
Metrology frameOptical element stage
Illumination optics stagePO rotation stage
Optical element stageProjection optics (PO)PO loader
PO loading crane
EUV light
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EWMS at New Subaru synchrotron facility EWMS at New Subaru synchrotron facility
Vacuum pump
Main vacuum chamber Vacuum chamber forillumination optics
PO loader
Undulatorbeamline
12EUVL Symposium, October 31, 2007, K. Murakami
EUV wavefront metrology using EWMS startedEUV wavefront metrology using EWMS startedThermal clean chamber was installed. Temperature fluctuation is less than +/-0.1K.Prototype full-field EUV projection optics was installed in EWMS and metrology experiments started. However, EUV intensity through pinhole was very low.→ Illumination optical system was upgraded.
13EUVL Symposium, October 31, 2007, K. Murakami
BeamlineBeamline optics layout for EWMSoptics layout for EWMS
LU M0 M1 G S1
M4
M5M6
PO
MaskCCD
PH Mask
M8
M7
LU M0 M1
G
S1
M4M5
M6
Top View
Side View
F
F
PO
M7
M8Schwarzschild
Schwarzschild
:Illuminator optics. These mirrors were upgraded.
STOP
STOP
14EUVL Symposium, October 31, 2007, K. Murakami
M6 M8M7
MSFR (mid-spatial frequency roughness) of old mirrors were not small enough to collect synchrotron radiation light onto a pinhole.New mirrors with improved MSFR were polished.
Mirrors for illumination optics for EWMS were upgradedMirrors for illumination optics for EWMS were upgraded
0.13nmRMS0.79nmRMSM8
0.13nmRMS2.02nmRMSM7
0.18nmRMS0.56nmRMSM6
New mirrorsOld mirrors
0.13nmRMS0.79nmRMSM8
0.13nmRMS2.02nmRMSM7
0.18nmRMS0.56nmRMSM6
New mirrorsOld mirrors
MSFR of mirrors
15EUVL Symposium, October 31, 2007, K. Murakami
Illumination spot on a pinholeIllumination spot on a pinhole
800μm 800μm
Before upgrade After upgrade
Illumination spot on a pinhole mask was much reduced with upgraded illumination optics .Radiation intensity through the pinhole increased about thousand times.
16EUVL Symposium, October 31, 2007, K. Murakami
DTIDTI ((ddigital Talbot igital Talbot iinterferometrynterferometry))
CCD
PH
G
PO
Pinhole mask
Gratings
When the distance between gratings and image is equals to 2nd2/λ, high contrast interferogram is observed.(d: grating pitch, λ: wavelength, 2n: integer, n: Talbot order)
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InterferogramInterferogram obtained with EWMSobtained with EWMS
Clear interferogram was obtained with EWMS in DTI configuration.
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Wavefront reconstruction processWavefront reconstruction process
DZF: differential Zernike polynomial fittingRM: Rimmer method**M. P. Rimmer, Appl. Opt. 13 (3) 623 (1974)
fft Data
400 450 500 550 600
400
450
500
550
600
9
10
11
12
13
14
15
16
17
X-Shear
Y-Shear
ReconstructedWavefront
InterferogramResult
Removing Tilt & Power
Reconstructingby DZF or RM
FFT
i FFT
Spectrum
19EUVL Symposium, October 31, 2007, K. Murakami
Measured wavefront (differential Zernike polynomial fitting)Measured wavefront (differential Zernike polynomial fitting)
0.70 λ RMS
1.67 λ RMS
1.01 λ RMS
1.76 λ RMS
0.88 λ RMS
4.9 λ-5.4 λ
CT
UR
LR
UL
LL CT
UR
LR
UL
LLUL
LR
UR
CT
LL
20EUVL Symposium, October 31, 2007, K. Murakami
Measured Measured wavefrontswavefronts ((RimmerRimmer method)method)
0.72 λ RMS
1.67 λ RMS
1.02 λ RMS
1.53 λ RMS
0.79 λ RMS
4.9 λ-5.4 λ
CT
UR
LR
UL
LL CT
UR
LR
UL
LL
UL UR
LR
CT
LL
21EUVL Symposium, October 31, 2007, K. Murakami
Comparison of wavefront reconstruction methodComparison of wavefront reconstruction method
-2
-1.5
-1
-0.5
0
0.5
1
1.5
5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35
Zern
ike
coef
ficie
nt (w
ave) Dfferential Zernike Polynomial Fitting
Rimmer Method
Differential Zernikepolynomial fitting
1.013 λ RMS 1.017 λ RMS
Rimmer methodCT
UR
LR
UL
LLCT
UR
LR
UL
LL
22EUVL Symposium, October 31, 2007, K. Murakami
SummarySummary
EUV wavefront metrology using EWMS was started.
Mirrors for illumination optics were upgraded and collection efficiency of EUV radiation onto a pinhole was much improved.
The first EUV wavefront data of full-field projection optics using EWMS with DTI (digital Talbot interferometry) method were successfully obtained. Wavefront data reconstructed with DZPF and RM were in good agreement.
Future workWavefront metrology with CGLSI method.Comparison of EUV and visible-light wavefront.
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AcknowledgmentAcknowledgment
The authors would like to thank the operation staff of New Subaru
synchrotron facility for their help.
This work was supported by NEDO
(New Energy and Technology Development Organization) .