Benefiting from Polarization: Effects at High-NA Imaging

Transcription

1 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

2 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

3 Illumination Effects

4 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.

5 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 = nm H-V 5 Bar Target 45nm H-V 5 Bar Target Diffraction Energy in Pupil Prolith/8

6 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 = nm H-V 5 Bar Target 45nm H-V 5 Bar Target Diffraction Energy in Pupil

7 Images in Resist Polarized Cross Quad Illumination Polarized Cross Quad Dipole s c =., s r =.25 Contrast = nm H-V 5 Bar Target Diffraction Energy in Pupil

8 Unpolarized Annular Dipole s o =., s i =.8 Contrast =.2 Images in Resist Annular Illumination TM polarized (Radial) Annulus 45nm H-V 5 Bar Target Diffraction Energy in Pupil polarized (Azimuthal) Annulus

9 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 = nm H-V 5 Bar Target 45nm H-V 5 Bar Target Diffraction Energy in Pupil

10 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 = nm H-V 5 Bar Target 45nm H-V 5 Bar Target Diffraction Energy in Pupil

11 Images in Resist through Focus Radial vs. -Dipole.7.6 Modulation in Resist polarized dipole polarized cross-quad Azimuthal annular Unpolarized annular Defocus (nm) - Annular illumination will be used in dipole mode at low k - polarized cross quadrupole may be superior to annular

12 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

13 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 pairs pairs pairs pairs Transmission pair 2 pairs 3 pairs 4 pairs 5 pairs (s-plane) TM (p-plane) Incidence Angle (degrees)

14 Binary 6nm :, Polarized Imaging Focus (positive direction) (.5 µm steps) TM 6nm :, Binary mask DIPOLE illum.77s c/.s p

15 AltPSM 7nm :.3σ, Polarized Focus (positive direction) (. µm steps) Focus (positive direction) (.5 µm steps) TM Focus (positive direction) Unpolarized (.5 µm steps)

16 Mask Feature Effects

17 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 ()

18 Mask Polarization Graded Cr x O y N z over Cr x N y 8 atomic % C N O Cr Si Mask induced polarization effects at low k, A. Estroff et al 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 k Thickness (A)

19 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 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 Grating Period (µm) Cr-O-N 93nm - Zero Order Degree of Polarization Unpolarized Transmission 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

20 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 % 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 Degree of Polarization TM 8% 6% 4% 2% % -2% -4% -6% -8% -% th Order Grating Period (µm) 6% 4% 2% % -2% -4% -6% -8% -% -2% Transmission

21 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 Degree of Polarization TM Degree of Polarization TM 4% 3% 2% % % -% 4% 3% 2% % % -% +st Order Polarization Degree of Polarization Unpolarized Transmission Grating Period (mm) -st Order Polarization Degree of Polarization Unpolarized Transmission Grating Period (mm) 4% 2% % 8% 6% 4% 2% % 4% 2% % 8% 6% 4% 2% % Transmission Transmission

22 Thin Film Reflection Effects

23 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

24 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

25 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

26 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

27 Single Layer ARC Optimization for.2na Reflectance (%) optimized, ARC(.7,.5), 35nm Avg TM Reflectance (%) optimized, ARC(.7,.3), 52nm Avg TM Angle (degrees) Angle (degrees) Reflectance (%) TM optimized, ARC(.7,.5), 52nm Avg TM Reflectance (%) optimized, ARC(.7,.3), 48nm Avg TM Angle (degrees) Angle (degrees) TF Calc

28 ARC for -45 /TM Polarization Multilayer Designs Full angular optimization -45 (.2NA) 25. Reflectance (%) Avg TM ARC Resist (.7,.5) 42nm (.7,.2) 48nm (.7,.5) Poly-Si Angle (degrees) Reflectance (%) Avg TM Angle (degrees) Normal incidence optimized ARC(.7,.5) 35nm

29 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