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12005 International Symposium on Extreme Ultraviolet Lithography, Nov.7-9, 2005
Supported by NEDO
EUV Wavefront Metrology Systemin
EUVA
EUVA EUV Metrology LaboratoryUtsunomiya R&D Center (Canon)1
Sagamihara R&D Center (Nikon)2
University of Hyogo3
University of Electro-Communications4
Takayuki Hasegawa1, Seima Kato1, Chidane Ouchi1, Masanobu Hasegawa1, Hideo Yokota1, Yutaka Tanaka1, Katsumi Sugisaki2, Masashi Okada2,
Jun Kawakami2,Katsuhiko Murakami2, Yucong Zhu2, Katsura Otaki2, Zhi Qiang Liu2 Jun Saito2, Masahito Niibe3, Mitsuo Takeda4
E-mail: hasegawa.takayuki@canon.co.jp
22005 International Symposium on Extreme Ultraviolet Lithography, Nov.7-9, 2005
Supported by NEDOAbbreviations
EEI EUV Experimental InterferometerEWMS EUV Wavefront Measurement SystemPO Projection OpticsPDI Point Diffraction InterferometerLDI Line Diffraction InterferometerLSI Lateral Shearing InterferometeCGLSI Cross-Grating LSIFFT Fast Fourier Transform method
32005 International Symposium on Extreme Ultraviolet Lithography, Nov.7-9, 2005
Supported by NEDOOutline
1. Target of EUV Metrology Laboratory in EUVA
2. Reproducibility of PDI
3. Applicability of PDI to a six-mirror system
4. Improvement of CGLSI
5. Outline of EWMS
6. Summary
42005 International Symposium on Extreme Ultraviolet Lithography, Nov.7-9, 2005
Supported by NEDOTarget of EUV Metrology Laboratory in EUVA
20062005200420032002
End of the Project
TestDesign
ExperimentFabricationDesign
EWMS
EEI (Schwarzschild Test Optics installed)
Result
EWMS (EUV Wavefront Metrology System)
A prototype interferometer to determine measurement methods for EWMS
An interferometer for six-mirror Projection Optics with 0.1nm accuracy
EEI (EUV Experimental Interferometer)
Target
Approach
Fabrication
52005 International Symposium on Extreme Ultraviolet Lithography, Nov.7-9, 2005
Supported by NEDOReview of EEI
Cleanchamber
EEI Illuminator(NA:0.01)
Overall view of EEIInside View
Inside view of EEI
Test OpticsSchwarzschild NA 0.2Mag. 1/20
EUV beamline
Installed at NewSUBARU
of Univ. of Hyogo
EUV beam from undulator
62005 International Symposium on Extreme Ultraviolet Lithography, Nov.7-9, 2005
Supported by NEDOResults of evaluation
PDI and CGLSI are potential candidates for EWMS
DLSI(Double Grating)
SLSI(Slit type)
LSI
Easy alignmentCGLSI(Cross Grating)
Two interferograms necessaryDifficult to determine astigmatism
Two interferograms necessaryDifficult to determine astigmatism
Two interferograms necessaryDifficult to determine astigmatism
LateralShearingInterferometer
Higher contrast than PDITwo interferograms necessary
LDI(Line)
High accuracyNarrow cover range of aberrationLarge loss of the light Intensity
PDI(Point)
Diffraction typeInterferometer
FeaturesInterferogramAvailable Methods
One
dim
ensi
onal
gra
ting
Y
X
Y
Y
Y
X
X
X
4-Window
72005 International Symposium on Extreme Ultraviolet Lithography, Nov.7-9, 2005
Supported by NEDO
Pinhole
Test Optics
Window +Pinhole
CCD Camera
EUV Beam
Pinhole
Cross Grating
4 Windows
1-DimensionalGrating
Optical Configurations of PDI and CGLSI
PDI CGLSI(Cross Grating LSI)(Point Diffraction Interferometer)
Schwarzschild NA 0.2Mag. 1/20
Test Optics
Test Optics
CCD Camera
EUV Beam
82005 International Symposium on Extreme Ultraviolet Lithography, Nov.7-9, 2005
Supported by NEDOReproducibility of PDI
Precise pinhole alignment is necessary to improve the reproducibility.
Interferogram
Fringe pitch changes with respect to the position of the pinhole. The alignment was improved using the fringe pitch.
Pitch of the fringes
1.26148.321.923
1.3058.614.882
1.3526.7258.201
Wavefront aberrationnm RMS
Alignment error ∆Y nm
Alignment error ∆X nm
Measurement number
Alignment error of the pinhole and the focus point causes error in the measurement.
Reproducibility was 0.103 nm RMS
92005 International Symposium on Extreme Ultraviolet Lithography, Nov.7-9, 2005
Supported by NEDOReproducibility of PDI
7
5
3
0.0701.28Average
0.045Mean
wavefront Wm1.31
Average
0.0431.29
0.0501.32
0.040
0.032
0.0370.043
Difference from mean wavefront Wi-Wm nm RMS
1.31
1.33
1.321.36
WavefrontaberrationWi nm RMS
-0.3nm-10.0nm
-0.7nm-1.4nm
-5.5nm-17.7nm
-0.3nm-0.7nm6
-0.5nm0.9nm4
-18.7nm-6.0nm2
-8.0nm0.7nm1
Alignment error∆Y
Alignment error∆X
Measurement number i
Alignment error has been improved to better than 20 nm.Reproducibility of PDI has been improved to 0.045 nm RMS.
Measurement results after the improvement in alignment.
102005 International Symposium on Extreme Ultraviolet Lithography, Nov.7-9, 2005
Supported by NEDOApplicability of PDI to a six-mirror system
Test optics for EEI Six-mirror PO for EWMS
NA 0.2Pinhole diameter 50nm
Reflectance(60%)^2
NA 0.25Pinhole diameter 30nm
decrease of the light intensity
Decrease due to the pinhole diameter.
Reflectance(60%)^6
NA 0.01Pinhole diameter 650nm
NA 0.0625Pinhole diameter 100nm
Decrease due to the increase in number of mirror.
We evaluate PDI at 1/20 of the standard light intensity in EEI.
Can PDI be applicable to six-mirror system with the reduced light intensity?
112005 International Symposium on Extreme Ultraviolet Lithography, Nov.7-9, 2005
Supported by NEDOApplicability of PDI to a six mirror system
1/20 of the standard light intensity in EEIStandard light intensity in EEI
Obtained interferogramsThese interferograms were obtained under the same alignment of the pinhole and the focus point using ND Filter in the beam line.
High contrast interferograms were obtained even at 1/20 of the standard light intensity in EEI.
122005 International Symposium on Extreme Ultraviolet Lithography, Nov.7-9, 2005
Supported by NEDOApplicability of PDI to a six mirror system
1.31nm
1.37 nm
1/20 intensity
0.041 nm1.32nm
2nd trial
0.043 nm1.35nm
1st trial
DifferenceStandard intensity
nm RMS(Z5-36)
Results
PDI at 1/20 of the standard light intensity in EEI was in well agreement with PDI at a standard light intensity.
PDI is applicable to the measurement of a six-mirror PO.
132005 International Symposium on Extreme Ultraviolet Lithography, Nov.7-9, 2005
Supported by NEDOImprovement of CGLSI
Optimization of optical elements and alignment.
Optimization of the window size.
Pinhole
Cross Grating
4 Windows
Distance between the grating and the window was set to the design value precisely.
Difference between CGLSI and PDI was 0.28 nm RMS.(*1)To improve CGLSI we optimized the measurement
condition and the data analysis method.
Fringe pitch changes with respect to the distance between the grating and the window. We set the grating using this fact.
(*1)Ref. Hasegawa et. al, EIPBN 2, June 2005
142005 International Symposium on Extreme Ultraviolet Lithography, Nov.7-9, 2005
Supported by NEDOImprovement of CGLSI
FFT
iFFT
(Y-direction)
(X-direction)
Optimization of the data analysis method
InterferogramFrequency map
iFFT
Differential wavefront
Differential Zernike polynomial
fitting
Retrievedwavefront
Elimination of flare effect
Half Pitch Shift method(*2)
CGLSI wavefront
Optimization of the spatial filter.
Distance between two focus points calculated from the experiment was used for evaluating CCD tilt.
(*2)Ref. Kato et. al, SPIE vol. 5751, 110-117 (2005)
152005 International Symposium on Extreme Ultraviolet Lithography, Nov.7-9, 2005
Supported by NEDOImprovement of CGLSI
Wavefront Aberration nm RMS
CGLSI PDI1.24nm 1.26nm
0.17 nm
Comparison between PDI and CGLSI
-0.150
-0.100
-0.050
0.000
0.050
0.100
0.150
5 10 15 20 25 30 35
CGLSI
PDI
-0.015
-0.01
-0.005
0
0.005
0.01
0.015
0.02
0.025
5 10 15 20 25 30 35
RMS of difference
Difference between CGLSI and PDI is 0.17 nm RMS.This value is small enough to evaluate a six-mirror PO.
Zernike coefficients
Zernike coefficients
[λ]
[λ]
162005 International Symposium on Extreme Ultraviolet Lithography, Nov.7-9, 2005
Supported by NEDOOutline of EWMS
Stages at the object plane
Stages at the image plane
Main structure of EWMS
Illumination systemSchematic view of EWMS
FeatureSix-mirror PO can be evaluated.Arbitrary points in the exposure field are measurable.Multiple interferometric methods can be operated in succession without breaking
the evacuated condition of the chamber.
172005 International Symposium on Extreme Ultraviolet Lithography, Nov.7-9, 2005
Supported by NEDOOutline of EWMS
EWMS has been manufactured.EWMS will be transported to NewSUBARU in late November.
Surrogate PO and PO transport
Stages at the object plane
Stages at the image plane
Overall view of EWMS
182005 International Symposium on Extreme Ultraviolet Lithography, Nov.7-9, 2005
Supported by NEDOSummary
Reproducibility of PDI was improved to 0.045 nm RMS.
PDI is applicable to the measurement of a six-mirror PO.
Difference between CGLSI and PDI was improved to 0.17 nm RMS.
The manufacturing of EWMS is going on as scheduled.
192005 International Symposium on Extreme Ultraviolet Lithography, Nov.7-9, 2005
Supported by NEDOAcknowledgment
This work was performed under the management of
a research and development program of
NEDO/METI, Japan.
And the authors express their gratitude to
University of Hyogo
for the collaboration work with NewSUBARU.
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