F2 Exposure Tool Soichi Owa, Naomasa Shiraishi, Issei Tanaka, Yasuhiro Ohmura, Toshihiko Ozawa, Teruki Kobayashi, Kazushi Nomura, Takashi Aoki, and Takayuki Mizutani Corporation NSR 157nm Data Review 1
Outline 1. F2 Exposure Tool Basic Specification 2. Optics design 3. Intrinsic birefringence Birefringence by axis direction Correction method Correction result Polishing 4. Coating 5. Purging 6. Pellicle NSR 157nm Data Review 2
Exposure Tool Basic Spec. NA > 0.8 Reduction ratio 4X Field size 22mm x 33mm Throughput (300mm wafer) > 90 wph (10mJ/cm2 resist, 40W laser) Optics Off-axis catadioptric NSR 157nm Data Review 3
F2 Exposure Tool Imaging By imaging simulations: F2 (157nm) lithography with NA>0.8 can cover: With binary mask: 80-70nm L/S With attenuated PSM 70-60nm L/S 90-80nm contact hole With alternating PSM 60-55nm L/S 35-25nm isolated line (double exposure) NSR 157nm Data Review 4
Projection Optics and Laser Optics Catadioptric Optics (off-axis) Laser Line selected laser Spectrum bandwidth 1.0pm FWHM 2.5pm 95%width Output power 40W NSR 157nm Data Review 5
Off-axis Catadioptric Optics Type A Type B Type C NA >0.8, Scanning slit length 22mm NSR 157nm Data Review 6
Intrinsic Birefringence (IB) NIST report (May and July) NIST Dn (157.63nm) = 11.2 +- 0.5nm/cm measurement Dn (156.96nm) = 11.5 +- 0.8nm/cm Data are consistent. NSR 157nm Data Review 7
Crystal structure and IB CaF2 axes [101] [001] [111] [011] Zero Birefringence on [100] and [111] Axes. Max. Birefringence on [110] Axis. [010] [100] [110] NSR 157nm Data Review 8
Intrinsic Birefringence of [111] axis [111] Distribution of Birefringence [101] [011] [110] CaF2 Plate NSR 157nm Data Review 9
Intrinsic Birefringence of [100] axis Distribution of Birefringence [100] [110] [-1-10] [-10-1] [101] CaF2 Plate NSR 157nm Data Review 10
Intrinsic Birefringence of [110] axis [110] Distribution of Birefringence [100] [111] [11-1] [010] CaF2 Plate NSR 157nm Data Review 11
Correction Methods [111] Axis [100] Axis [110] Axis + 60 deg. rotation + 45 deg. rotation + 90 deg. rotation ( NIST mentioned ) [111] Axis [100] Axis [110] Axis NSR 157nm Data Review 12
Correction Software At present, is using a combination of: In-house software Evaluation and optimization Code-V (since Oct. 2001) Automatic optimization NSR 157nm Data Review 13
Effect on Point Spread Function No birefringence With IB before correction Strehl Intensity ~ 1.00 Strehl Intensity = 0.56 NSR 157nm Data Review 14
Correction Status With birefringence (11nm/cm) after correction Other than PSF, we are checking, CD uniformity, line width abnormality, etc. We are in the final stage of correction, but have not finished it. S.I. = 0.96 NSR 157nm Data Review 15
Polishing of New Surfaces Hardness is different between [111], [100] and [110]. Polishing speed is different. is doing R&D, and is getting data: 1. By a modified polishing method, polishing speed difference has become small enough. 2. Surface roughness became good in all [111], [100] and [110] surfaces. NSR 157nm Data Review 16
Intrinsic birefringence status and Timing Optics design is in the final stage, but is not completed. Polishing R&D on new surfaces is ongoing, we are getting good data. Delay due to IB amounts to several months. #1 exposure tool shipment is also delayed, but we are trying to have the timing in 2004. NSR 157nm Data Review 17
Coating Water-free process is expected to improve performance and durability. Condition: AR-Coatings with Both sides of CaF2 substrate 100 Transmittance [%] 95 90 85 Water Free 80 V-Coat Conventional 75 Water Free W-Coat Conventional 70 140 145 150 155 160 165 170 175 180 Wavelength [nm]? Incident Angle NSR 157nm Data Review 18
Coating (Water-Free) Transmittance(%) 100 98 96 94 92 90 IR transmittance Water free process Wide type Conventional process V-type OH stretching vibration Conventional process Wide type 1500 2000 2500 3000 wavelength(nm) NSR 157nm Data Review 19
Purging of closed space Closed space purging shows steady progress. 1000000 21% 100000 Oxygen [ppm] 10000 1000 100 10 1 0.1 Diffusion model Experiment 0:00 5:00 10:00 15:00 Purging Time (Min:Sec) Concentration [ppm] 10 1 0.1 0.01 H 2 O O 2 0.001 0:00 0:30 1:00 1:30 2:00 2:30 3:00 3:30 4:00 Purge Time [h:m] [O 2 ] < 1ppm [O 2 ] < 0.1ppm [H 2 O] < 1ppm NSR 157nm Data Review 20
Purging of closed space Concentration [ppm] 1000 100 10 1 0.1 O2 H2O 0.01 0:00 0:10 0:20 0:30 0:40 0:50 1:00 Purge time [Hour:Min] Recent experiment: [O 2 ] ~ 0.01ppm [H 2 O] ~ 0.1ppm NSR 157nm Data Review 21
Purging of wafer and reticle space Frequent exchange of wafer and reticle, and purging should be attained at the same time. Global purging (whole space purging surrounding W/R stages) and local purging (limited space purging of optical path) are being studied by Computational Fluid Dynamics simulations. NSR 157nm Data Review 22
Pellicle Our primary preference is SOFT (or thin) pellicle. We expect the improvement of durability by 2004. Thin, inorganic pellicle seems to be better than hard pellicle from the optical viewpoint. Hard pellicle is the second choice. Distortion caused by mounted pellicle is the issue. Distortion pattern should be same for every mounted pellicles. Because we cannot measure the distortion beforehand. (Distortion correction parameter should be constant for all pellicles) Removable pellicle is a common subject with EUV, but it takes time for R&D. It will not be in time for 2004 exposure tool shipment. NSR 157nm Data Review 23
Summary Optics design correcting for IB is in the final stage, but is not finished yet. Polishing of [100], [110] seems to be feasible. Coating performance and durability is being improved by water-free process. Purging development shows steady progress. Delay due to IB will amount to several months. #1 Exposure tool shipment is also delayed, but we are trying to have the timing in 2004. NSR 157nm Data Review 24