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Performance Characterization of the EUV optical imaging module of the Reticle Imaging Microscope (RIM)
R. HudymaHyperion Development LLC
H. Glatzel, J. Daniel, K. Khajehnouri, U. Mueller, T. Roff, J. Rosenbohm, S. Sporer Tinsley Labs
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C2
C1
C3
C4
M1M2
Y
XZ
The EUV optical system
Koehler Ilumination:Source imaged to intermediate pupil plane w/ coherence apertures
source
Off-axis Schwarzschild condensor
Equal-radii Cassegrain10x Microscope
• Diffraction-limited imaging and inspection of Reticles at 13.5 nm (EUV)
• Description of entire RIM system by M. Booth et al, SPIE vol 5751 (2005), p. 78 [Ref 1]
• Areas of Responsibilities:• Exitech: entire tool
• Hyperion Development:optical design, lithographic modeling
• Osmic: High-Reflectivity coatings
• Tinsley: EUV optical system –imaging and illumination modules, system integration & alignment
Reticle
Scintillator
Relay optics
700mm
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The imager module
M1 mirror
M2 mirror
3 bipods w/ flexures
6 Struts w/ flexures & picomotors
3 bipods w/ flexures
All metal parts in Invar
Optics in Zerodur
• Equal-radii Cassegrain
• 10x mag
• NA = 0.0625 (off-axis subaperture)
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Scope of this Poster
optical surface topology of imager mirrors- typical surface data - 3D maps using various instruments- average Power Spectral Density (PSD)- PSD fit- MSFR and HSFR RMS
transmitted wavefront error of imager module- full annulus- subaperture- Zernike expansion
optical performance predictions- comparison as-designed versus as-build- 128 nm L/S and 72 nm isolated lines- aerial images- ED and DOF analysis
Surface Metrology
•
Phase Shifting Interferometer (PSI)
Phase Measuring Microscope (PMM)4x Mag
Phase Measuring Microscope (PMM)50x Mag
Atomic Force Microscope (AFM)
95 mm
0.3 mm
3.3 mm
2 um
FoV+ 3 nm
- 3 nm
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1.00E-08
1.00E-07
1.00E-06
1.00E-05
1.00E-04
1.00E-03
1.00E-02
1.00E-01
1.00E+00
1.00E+01
1.00E+02
0.01 0.1 1 10 100 1000 10000 100000 1000000spatial frequency (1/mm)
PSD
(nm
^2*m
m)
+ 3 nm
- 3 nm
Fourier Transformation of surface maps
1D Power Spectral Density (PSD)
PSD(f) = A*f Slg(PSD) = lg(A) + s*lg(f)
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1.00E-08
1.00E-07
1.00E-06
1.00E-05
1.00E-04
1.00E-03
1.00E-02
1.00E-01
1.00E+00
1.00E+01
1.00E+02
0.01 0.1 1 10 100 1000 10000 100000 1000000
spatial frequency (1/mm)
PSD
(nm
^2*m
m)
MiniFiz4X50Xf^(-1.06)*10^(-1.67)AFM
Typical PSD of surface errors
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Achieved integrated Surface Errors for various imager mirrors
Error type spatial period WFE RMS range (nm)
Surface Figure Error (LSFR) CA … 1 mm 0.25 .. 0.39Mid-Spatial Frequency Error (MSFR) 1 mm … 1 μm 0.28 .. 0.36High-Spatial Frequency Error (HSFR) 1 μm … 1 nm 0.33 .. 0.37
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TWF RMS = 0. 79 nm nm
nm
Transmitted Wavefront Error of imager module
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Simulation of as-designed and as-built performanceshows excellent agreement for 128 nm L/S
• Modeling assumptions– 128 nm dense L/S– NA = 0.0625– Sigma = 0.60– Flare = 0%– “As-designed” =
Zernikes computed from optical design code
– “As-built” = Measured Zernikes
– Thin mask• Results
– Contrast, NILS, and CD are in excellent agreement
– Image shift that can be removed via system alignment
RIM Aerial Image Comparison "As-Designed "vs. "As-Built" for 128 nm L/S (s = 0.60, no flare)
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-128 -96 -64 -32 0 32 64 96 128Simulatin domain (nm)
As-DesignedAs-Built
Inte
nsity
(au)
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ED analysis shows no meaningful degradation in measurement capability due to aberrations for 128 nm L/S
RIM As-designed RIM As-built
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• Modeling assumptions– 72 nm isolated– NA = 0.0625– Sigma = 0.60– Flare = 0%– “As-designed” =
Zernikes computed from optical design code
– “As-built” = Measured Zernikes
– Thin mask• Results
– Contrast, NILS, and CD are in excellent agreement
– Image shift that can be removed via system alignment
RIM Aerial Image Comparison "As-Designed " vs."As-Built" for 72 nm isolated lines (s = 0.60, no flare)
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-128 -96 -64 -32 0 32 64 96 128Simulatin domain (nm)
As-DesignedAs-Built
Inte
nsity
(au)
Simulation of as-designed and as-built performance shows excellent agreement for isolated 72 nm lines
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ED analysis shows no meaningful degradation in measurement capability due to aberrations for 72 nm
isolated linesRIM As-designed RIM As-built
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Summary: optical performance prediction
• Simulations using as-designed Zernikes and as-built Zernikes demonstrate that the imagery shows excellent correlation under the stated simulation assumptions– Predicted as-built image contrast, NILS, CD, and ED
characteristics show excellent correlation to baseline design
• Low-order aberrations induced by mirror fabrication and alignment errors will have little or no impact on RIM tool performance– Zernike based tolerance method and error budgeting
procedure developed specifically for the RIM tool has been validated
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Acknowledgements & References
Acknowledgements
• Special thanks to the teams at - Exitech, - Hyperion, - LLNL, - Osmic, - SSG and - Tinsleyfor supporting this work with passion and dedication
• Ian Wallhead at Exitech for supporting our development activities and providing specifications and valuable feedback
• Layton Hale at LLNL for contributions to the mechanical design and structural analysis
References1. M. Booth et al, “High-resolution EUV imaging tools for resist exposure and aerial
image monitoring” , SPIE vol 5751 (2005), p. 78.
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End of presentation
