Benefiting from Polarization: Effects at High-NA Imaging Bruce W. Smith L. Zavyalova, A. Estroff, Y. Fan, A. Bourov Rochester Institute of Technology P. Zimmerman International SEMACH and Intel J. Cashmore Exitech
Polarization Issues and High-NA Polarization is a concern with high-na Effects increase substantially with the large angles allowed with immersion lithography. Illumination effects 2. Mask feature effects 3. Thin film reflectivity at resist /AR
Illumination Effects
Oblique Angles from High NA Air n i =., s, or Y-polarized TM, p, or X-polarized Resist n i >. - Polarization effects scale with cosine of angle. - TM state will interfere exactly at normal incidence only. - Image is the sum of and TM. - Aerial image metrics no longer useful.
Images in Resist Dipole and Cross Quad Illumination Unpolarized Dipole s c =., s r =.25 Contrast =.42 Unpolarized Cross - Quadrupole s c =., s r =.25 Contrast =.23.26-.38.4-.26.2-.4.9-.2.78-.9.66-.78.54-.66.42-.54.3-.42.26-.38.4-.26.2-.4.9-.2.78-.9.66-.78.54-.66.42-.54.3-.42 45nm H-V 5 Bar Target 45nm H-V 5 Bar Target Diffraction Energy in Pupil Prolith/8
Images in Resist Polarized Dipole Illumination X-Orient / Y-Polarization Dipole s c =., s r =.25 Contrast =.69 Y-Orient / X-Polarization Dipole s c =., s r =.25 Contrast =..26-.38.4-.26.2-.4.9-.2.78-.9.66-.78.54-.66.42-.54.3-.42.26-.38.4-.26.2-.4.9-.2.78-.9.66-.78.54-.66.42-.54.3-.42 45nm H-V 5 Bar Target 45nm H-V 5 Bar Target Diffraction Energy in Pupil
Images in Resist Polarized Cross Quad Illumination Polarized Cross Quad Dipole s c =., s r =.25 Contrast =.38.26-.38.4-.26.2-.4.9-.2.78-.9.66-.78.54-.66.42-.54.3-.42 45nm H-V 5 Bar Target Diffraction Energy in Pupil
Unpolarized Annular Dipole s o =., s i =.8 Contrast =.2 Images in Resist Annular Illumination.26-.38.4-.26.2-.4.9-.2.78-.9.66-.78.54-.66.42-.54.3-.42 TM polarized (Radial) Annulus 45nm H-V 5 Bar Target Diffraction Energy in Pupil polarized (Azimuthal) Annulus
Images in Resist Radial and Azimuthal Annular Azimuthal Polarized Annular Dipole s c =., s r =.25 Contrast =.23 Radial Polarized Annular Dipole s c =., s r =.25 Contrast =.2.26-.38.4-.26.2-.4.9-.2.78-.9.66-.78.54-.66.42-.54.3-.42.26-.38.4-.26.2-.4.9-.2.78-.9.66-.78.54-.66.42-.54.3-.42 45nm H-V 5 Bar Target 45nm H-V 5 Bar Target Diffraction Energy in Pupil
Images in Resist Polarized Annular vs. C-Quad Azimuthal Polarized Annular Dipole s c =., s r =.25 Contrast =.23 Polarized C-Quad Dipole s c =., s r =.25 Contrast =.38.26-.38.4-.26.2-.4.9-.2.78-.9.66-.78.54-.66.42-.54.3-.42.26-.38.4-.26.2-.4.9-.2.78-.9.66-.78.54-.66.42-.54.3-.42 45nm H-V 5 Bar Target 45nm H-V 5 Bar Target Diffraction Energy in Pupil
Images in Resist through Focus Radial vs. -Dipole.7.6 Modulation in Resist.5.4.3.2. polarized dipole polarized cross-quad Azimuthal annular Unpolarized annular 5 5 2 25 3 Defocus (nm) - Annular illumination will be used in dipole mode at low k - polarized cross quadrupole may be superior to annular
Implementing Polarization ISMT / Exitech.85NA 57nm Polarization methods: Mirror Mirror Birefringence (Glan-Taylor) Selective absorption (Dichroic) Selective reflection (Wollaston) Illuminator Mask Projection Lens Polarizer Mirror Wafer F2 Laser polarizer plates assembly θ B =57.3 unpolarized input laser beam linearly polarized output beam VUV Brewster Angle Plate Polarizer CaF 2 Brewster angle of 57.3º
VUV Polarizer Performance Performance specifications Principal (TM) Transmittance: >96%T Extinction Ratio: ~.3 Transmission: 5.5% Efficiency -T(s)/T(p) Extinction T(s)T(p) Transmission [T(p)+T(s)]/2 pair.5.5.75 2 pairs.75.25.625 3 pairs.875.25.562 4 pairs.938.62.53 5 pairs.969.3.55 Transmission..9.8.7.6.5.4.3.2.. pair 2 pairs 3 pairs 4 pairs 5 pairs (s-plane) TM (p-plane) 2 3 4 5 6 7 Incidence Angle (degrees)
Binary 6nm :, Polarized Imaging Focus (positive direction) (.5 µm steps) TM 6nm :, Binary mask DIPOLE illum.77s c/.s p
AltPSM 7nm :.3σ, Polarized Focus (positive direction) (. µm steps) Focus (positive direction) (.5 µm steps) TM Focus (positive direction) Unpolarized (.5 µm steps)
Mask Feature Effects
Mask-induced Polarization Wire Grid Polarizers Sub-wavelength Zero-Order Grating Parallel reflected component (TM) Polarizing wires (Wood, Philosophical Magazine, 92). Resonant high orders (Rayleigh, Philosophical Magazine, 97). p l = ( n ± sinq ) k Perpendicular transmitted component ()
Mask Polarization Graded Cr x O y N z over Cr x N y 8 atomic % 6 4 2 C N O Cr Si Mask induced polarization effects at low k, A. Estroff et al 5377-22 2 4 6 8 2 Depth (Angstroms) Cr-O-N Stack Composition Layer Layer 2 Layer 3 Layer 4 Cr 9.% 8.9% 9.45%.% CrN.% 2.%.5%.% CrOx.% 79.% 89.5%.% Data for Cr-O-N Stack (Layer is closest to substrate, Layer 4 is furthest) Layer Layer 2 Layer 3 Layer 4 93nm 248nm 93nm 248nm 93nm 248nm 93nm 248nm n.829.8863.5649.842.674.9734.7782 2.26 k.825.87.42.739.3597.6584.348.598 Thickness (A) 9 9 33 33 33 33 33 33
Cr-O-N 93nm Binary Mask Polarization Normal incidence RCWA of mask structures Degree of Polarization = (-TM)/(+TM) Mask induced polarization effects at low k, A. Estroff et al 5377-22 Degree of Polarization Degree of Polarization TM 25% 2% 5% % 5% % % % -% -2% -3% -4% -5% -6% Cr-O-N 93nm - First Order st Order Polarization...2.3.4.5.6.7.8.9 Grating Period (µm) Cr-O-N 93nm - Zero Order Degree of Polarization Unpolarized Transmission...2.3.4.5.6.7.8.9 Grating Period (µm) Degree of Polarization Unpolarized Transmission th Order Polarization 9% 8% 7% 6% 5% 4% 3% 2% % % 3% 25% 2% 5% % 5% % Transmission Transmission G-Solver
93nm Attenuated PSM Polarization Normal incidence TaN-Si3N4 st-order Degree MoO3-SiO2 st-order Degree Degree of Polarization TM 3% 2% % % -% -2% -3% -4% -5% -6% TaN-Si3N4 Unpolarized st-order T MoO3-SiO2 Unpolarized st-order T 2% 5% st Order...2.3.4.5.6.7.8.9 % 5% % -5% -% Transmission -5% -2% Grating Period (µm) TaN-Si3N4 -Order Degree MoO3-SiO2 -Order Degree TaN-Si3N4 Unpolarized -order T MoO3-SiO2 Unpolarized -order T % Transmitting Attenuated PSM Materials TaN - Si 3 N 4 MoO 3 SiO 2 Mask induced polarization effects at low k, A. Estroff et al 5377-22 Degree of Polarization TM 8% 6% 4% 2% % -2% -4% -6% -8% -% th Order...2.3.4.5.6.7.8.9 Grating Period (µm) 6% 4% 2% % -2% -4% -6% -8% -% -2% Transmission
Asymmetrical Order Polarization Angular incidence.2na 4X Imaging System 7.45 in air,.5 in glass Mask induced polarization effects at low k, A. Estroff et al 5377-22 Degree of Polarization TM Degree of Polarization TM 4% 3% 2% % % -% 4% 3% 2% % % -% +st Order Polarization Degree of Polarization Unpolarized Transmission...2.3.4.5.6.7.8.9 Grating Period (mm) -st Order Polarization Degree of Polarization Unpolarized Transmission...2.3.4.5.6.7.8.9 Grating Period (mm) 4% 2% % 8% 6% 4% 2% % 4% 2% % 8% 6% 4% 2% % Transmission Transmission
Thin Film Reflection Effects
ARC Reflectivity at Normal Incidence 93nm in Resist (.7,.5), 2% reflectivity contours n(arc) =.5 ARC thickness (nm) 2 n(arc) =.7 ARC thickness (nm) 2 n(arc) =.9 n(arc) = 2. ARC thickness (nm) 2 ARC thickness (nm) 2
ARC Reflectivity at 45 Incidence Unpolarized radiation, 2% reflectivity contours n(arc) =.5 ARC thickness (nm) 2 n(arc) =.7 ARC thickness (nm) 2 n(arc) =.9 n(arc) = 2. ARC thickness (nm) 2 ARC thickness (nm) 2
ARC Reflectivity at 45 Incidence Polarization, 2% reflectivity contours n(arc) =.5 ARC thickness (nm) 2 n(arc) =.7 ARC thickness (nm) 2 n(arc) =.9 n(arc) = 2. ARC thickness (nm) 2 ARC thickness (nm) 2
ARC Reflectivity at 45 Incidence TM Polarization, 2% reflectivity contours n(arc) =.5 ARC thickness (nm) 2 n(arc) =.7 ARC thickness (nm) 2 n(arc) =.9 n(arc) = 2. ARC thickness (nm) 2 ARC thickness (nm) 2
Single Layer ARC Optimization for.2na Reflectance (%) 25. 2. 5.. 5. optimized, ARC(.7,.5), 35nm Avg TM Reflectance (%) 25. 2. 5.. 5. 45 optimized, ARC(.7,.3), 52nm Avg TM. 2 4 6 8. 2 4 6 8 Angle (degrees) Angle (degrees) Reflectance (%) 25. 2. 5.. 5. 45 TM optimized, ARC(.7,.5), 52nm Avg TM Reflectance (%) 25. 2. 5.. 5. 45 optimized, ARC(.7,.3), 48nm Avg TM. 2 4 6 8 Angle (degrees). 2 4 6 8 Angle (degrees) TF Calc
ARC for -45 /TM Polarization Multilayer Designs Full angular optimization -45 (.2NA) 25. Reflectance (%) 2. 5.. 5. Avg TM ARC Resist (.7,.5) 42nm (.7,.2) 48nm (.7,.5) Poly-Si. 2 4 6 8 Angle (degrees) Reflectance (%) 25. 2. 5.. 5.. Avg TM 2 4 6 8 Angle (degrees) Normal incidence optimized ARC(.7,.5) 35nm
Conclusions - polarized illumination can provide resolution enhancement, C-Quad may be useful - Early results at 57nm confirm polarized imaging - Mask induce polarization effects exist, the impact is to be seen (e.g. Mag). - Resist stacks require full angle / polarization optimization