Nikon F2 Exposure Tool

Transcription

1 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

2 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

3 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

4 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

5 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

6 Off-axis Catadioptric Optics Type A Type B Type C NA >0.8, Scanning slit length 22mm NSR 157nm Data Review 6

7 Intrinsic Birefringence (IB) NIST report (May and July) NIST Dn (157.63nm) = nm/cm measurement Dn (156.96nm) = nm/cm Data are consistent. NSR 157nm Data Review 7

8 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

9 Intrinsic Birefringence of [111] axis [111] Distribution of Birefringence [101] [011] [110] CaF2 Plate NSR 157nm Data Review 9

10 Intrinsic Birefringence of [100] axis Distribution of Birefringence [100] [110] [-1-10] [-10-1] [101] CaF2 Plate NSR 157nm Data Review 10

11 Intrinsic Birefringence of [110] axis [110] Distribution of Birefringence [100] [111] [11-1] [010] CaF2 Plate NSR 157nm Data Review 11

12 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

13 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

14 Effect on Point Spread Function No birefringence With IB before correction Strehl Intensity ~ 1.00 Strehl Intensity = 0.56 NSR 157nm Data Review 14

15 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

16 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

17 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 NSR 157nm Data Review 17

18 Coating Water-free process is expected to improve performance and durability. Condition: AR-Coatings with Both sides of CaF2 substrate 100 Transmittance [%] Water Free 80 V-Coat Conventional 75 Water Free W-Coat Conventional Wavelength [nm]? Incident Angle NSR 157nm Data Review 18

19 Coating (Water-Free) Transmittance(%) IR transmittance Water free process Wide type Conventional process V-type OH stretching vibration Conventional process Wide type wavelength(nm) NSR 157nm Data Review 19

20 Purging of closed space Closed space purging shows steady progress % Oxygen [ppm] Diffusion model Experiment 0:00 5:00 10:00 15:00 Purging Time (Min:Sec) Concentration [ppm] H 2 O O :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

21 Purging of closed space Concentration [ppm] O2 H2O :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

22 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

23 Pellicle Our primary preference is SOFT (or thin) pellicle. We expect the improvement of durability by 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

24 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 NSR 157nm Data Review 24