SEMATECH 157nm Technical Review

Transcription

1 SEMATECH 157nm Technical Review Technical Status Report on F2 - Lasers for 157nm Lithography I. Klaft a), F. Voss a), I. Bragin a), E. Bergmann a), T. Nagy a), N. Niemöller a), K.Vogler a), S. Spratte a), G. Hua b), S. Govorkov b) a) Lambda Physik AG, Hans-Böckler-Str. 12, D-3779 Göttingen, Germany b) Lambda Physik Inc., 321 West Commercial Blvd, Fort Lauderdale, FL 3339, USA Tel: Fax: RandD@lambdaphysik.com < 1 > KV SEMATECH, 157nm Technical Review, Orlando

2 Technical Status Report on F2 - Lasers for 157nm Lithography Outline: Review of the 2kHz F2 - laser system current specification long term field data New aspects of metrology spectral aspects polarization tool beam propagation coherence measurements Ongoing development increase of repetition rate < 2 > KV SEMATECH, 157nm Technical Review, Orlando

3 NovaLine F22 Key Specifications Optimized module performance result in safer margin within specification: Specifications: power 2W ( single line ) gas life > 5Mio pulses wavelength nm bandwidth < 1.pm, FWHM spectral purity > 95% ± 4pm, E95 line ratio < 1%) dose stability < ±.5% MAV5 beam profile 23 ± 5mm / 5.5 ± 2mm divergence 6 ± 2mrad / 1.5 ± 1mrad peak power < 1MW (related to TIS) polarization > 95% < 3 > KV SEMATECH, 157nm Technical Review, Orlando

4 Dose Stability and Pulse Energy Sigma Long term AT run : worst value plot Histogram: worst case distribution MAV (5) < ±.2 % MAV (5): 99.9% < ±.15 % 2kHz, 1mJ single line 3 Sigma = 1.5 % Sigma simultaneously: 99.9% <.6 % < 4 > KV SEMATECH, 157nm Technical Review, Orlando

5 F22 long term operation in the field Long term trend of a F22 at customer site: Pulse energy margin & Pulse energy stability Sigma over 6.7 Bio F22 long term operation Pulse energy ( mj ) ,5 1,5 Sigma ( % ) Max.pulse energy E 13mJ Pulse stability 1 σ.7 % Total tube counter ( Mio shots ) E@2kHz, HV=const < 5 > KV SEMATECH, 157nm Technical Review, Orlando

6 Lambda Physik`s Compact High Resolution VUV 157nm Spectrometer Individual laser check: dependence of spectral properties Features: very compact ~ 1 m vacuum tight N 2 purged slit function FWHM <.9 pm E (95) <.35 pm moveable adequate SW background subtraction inspection range = 15 pm dispersion = 13.8 fm / px < 6 > KV SEMATECH, 157nm Technical Review, Orlando

7 Wavelength and Bandwidth of 157nm Emission as Function of Total Gas Pressure Linear dependence of bandwidth of the F2-emission line E 95 dependence about 3-times stronger Predictable absolute wavelength of emission LP / NIST data of wavelength shift confirmed 3.5 λp = P[ kpa].234 pm / kpa λe95 P = P[ kpa].748 pm / kpa 6 λp = ( P[ kpa] 26kPa) nm / kpa nm Wavelength as a function of total pressure F2 Laser E95 bandwidth FWHM } Fit error width [pm] wavelength Cymer NIST fit curve NIST data pressure [mbar] pressure [mbar] < 7 > KV SEMATECH, 157nm Technical Review, Orlando

8 Energy Level Scheme and Laser Transitions of the F2 - Laser 9 D' - state rovibrational levels v' = v' = 1 Theoretical results explain *) : the corresponding levels involved in the several transitions λ 1, λ 2,... λ 6-1 Rovibrational Energy ( cm ) v 6 v 5 v v j' = j m j' = 1 j'' = j - 1 m j'' = 1 v -1 v v +1 A' - state rovibrational levels 1 v 2 t t t *) will be discussed in an upcoming paper v 4 blue tail of the main transition line λ 1 the fast dissociation of the lower A state sub-ns lower level life time (no self termination) Transition Number Wavelength (nm) < 8 > KV SEMATECH, 157nm Technical Review, Orlando

9 Asymmetry of the nm Emission Line Shape of nm emission of operating point Result: asymmetric line shape blue tail no dependence on pressure difference between Max. and COG: λmax - λcog ~.19pm degree of asymmetry intensity EGY Asymmetry = EGY blue [pm] < 9 > KV SEMATECH, 157nm Technical Review, Orlando red

10 Asymmetry of the nm Emission Line F22 spectral line asymmetry versus tube pressure Asymmetry 1,8 ratio = ,6 1,4 Asymmetry 1,2 1,8,6,4 Asymmetry = EGY EGY blue red Almost no pressure dependence of line asymmetry Deviation of line center (λ max - λ cog ) ~.19pm, Pressure [mbar] < 1 > KV SEMATECH, 157nm Technical Review, Orlando

11 Full- Power Polarization Measurement Tool Polarization 2 Hz, 2W with high precision 1..9 N 2 relative power horizontal polarization > 95% 157 nm vertical horizontal measurement < 11 > KV SEMATECH, 157nm Technical Review, Orlando Features: reflection angle to vertical axis [ ] rotate-able device accuracy < 1 % direction of polarization detectable operating at full power

12 WIGNER Measurements of Beam Properties Outputcoupler variable attenuator rotate-able lens f = 985 mm General Scheme of the WIGNER measurement setup Laser Beam Profiler With CCD camera 55mm z NLF 22 measured data vertical horizontal Beam diameter (mm) 2ω 23 mm 5,5 mm Divergence (mrad) 2θ 6. mrad 1.5 mrad Lateral coherence length (µm) l C 3 µm 3 µm Beam quality for Gauss-Schell- Bundle with large M² π M ² = ω θ λ M ² = ω 1 + l C Results from Wigner measurement vertical horizontal Beam quality M Lateral coherence length l C Derived beam parameters by WIGNER measurements: beam dimensions divergence beam quality factor coherence < 12 > KV SEMATECH, 157nm Technical Review, Orlando

13 Investigations on Spatial Coherence of the F2 - Lasers YOUNG Coherence measuring tool: vacuum tight setup range of measurable coherence lengths: 5µm < l Coh < 15µm exchangeable holes D = 25µm compact moveable useable for highest reprates < 13 > KV SEMATECH, 157nm Technical Review, Orlando

14 Scheme of the YOUNG Setup for Coherence Measurements Experimental Setup: Perforated dressing Interference figure CCD sensor Interference figure Test system: He-Ne λ = nm Distance of openings: 1 mm Contrast = I I max max + I I min min.96 1-dim. projection of interference figure < 14 > KV SEMATECH, 157nm Technical Review, Orlando

15 Results of the YOUNG Measurements 1. F22 Spatial Coherence length of the beam measured by YOUNG tool in the middle of the 2 Hz: Visibility horizontal vertical 1/e horizontal direction: l coh < 35µm vertical direction: l coh < 35µm lateral length [µm] < 15 > KV SEMATECH, 157nm Technical Review, Orlando

16 Scheme of Shearing Spectrometer for Spatial Coherence Measurements F22: Spatial coherence measurement by lateral shearing interferometer main diffraction in 1st order independent of temporal coherence Lateral Shearing Principle shear adjustment Transmission - Grating - Shearing - Interferometer < 16 > KV SEMATECH, 157nm Technical Review, Orlando

17 Results of Investigations on Spatial Coherence by Shearing Spectrometer F22 Spatial Coherence : Dependence on alignment of laser resonator Distribution within the beam well adjusted : higher coherence - Distribution of regions of high and low coherence within the beam profile - not homogeneously distributed [mm] de-adjusted : lower coherence < 17 > KV SEMATECH, 157nm Technical Review, Orlando

18 Results of Investigations on Spatial Coherence of the F2 - Lasers F22 Spatial Coherence : Dependence on repetition rate Lower spatial coherence at higher repetition rate Horizontal coherence distance [µm] [1, 2.2kV] [4, 2.2kV] [16, 1mJ] [4, 1mJ] free running (multi shot) few shot [pulses per frame, egy mode] [4, 1mJ] [1, 1mJ] [8, 2.kV] [8, 1mJ] [2, 1mJ] Result: clear dependence on repetition rate high reprates reduce spatial coherence same in single shot measurement Repetition rate [Hz] < 18 > KV SEMATECH, 157nm Technical Review, Orlando

19 4 khz F2-Laser and High Repetition Rate Development High reprate behavior: configuration 1 3 POWER SDEV Power(W) SDEV(%) Reprate(Hz) High repetition rate F 2 module test results: Configuration 1: Optimized LDU-resonator current 4kHz prototype Conclusion: There is still margin for future improvements < 19 > KV SEMATECH, 157nm Technical Review, Orlando

20 Technical Status Report on F 2 Lasers for 157nm Lithography Acknowledgement Lambda Physik likes to acknowledge: Our cooperation partners for joint work within the German 157nm BMBF project The partners from Laser Zentrum Hannover (LZH) for the precise manufacturing of the coherence tool Horst Schreiber and John Bruning of Tropel for their support in the measurement of coherence by the shearing spectrometer Vitaly Datsyuk for performing assisting theoretical calculations on the F2-laser transition The project was partially supported by the BMBF, project FKZ 13N7442/ The authors appreciate the good cooperative work with the project partners: Zeiss, Schott, Jenoptik, Infineon, Heraeus < 2 > KV SEMATECH, 157nm Technical Review, Orlando