Performance and Properties of a High Power Light Source for EUV Lithography.

Transcription

1 Performance and Properties of a Hig Power Ligt Source for EUV Litograpy. I.V. Fomenkov, R.M. Ness, I.R. Oliver, S.T. Melnycuk, O.V. Kodykin, N.R. Böwering, C.L Rettig, J.R. Hoffman. Tis work was partially funded by DARPA contract N C-8017

2 Outline EUV Litograpy source requirements Overview of Cymer s EUV source and development Development progress Pulsed power system for ig rep.rate operation, termal engineering Electrodes: termal engineering, power loads, modeling Hig repetition rate operation, plasma dynamics, modeling, EUV conversion efficiency Source debris, contamination Source metrology, Imaging, Spectroscopy Alternative EUVL source elements: Sn Summary 2

3 Industry Source Requirements Central wavelengt 13.5 nm EUV Power (2% bandwidt) W Repetition frequency >6000 Hz Integrated energy stability (3σ, 50 pulses) +/- 0.3% Etendue of source output* mm 2 str Max. solid angle input to illuminator* str Source cleanliness >30,000 ours Spectral purity* duv/uv, nm infra-red, >800nm TBD 7% TBD presented at October 2003 EUVL Source Worksop, Antwerp * Not agreed among ASML,Nikon and Canon 3

4 Overview of Cymer s EUV Source and Development 4

5 Cymer DPF EUV Source System Xe Intensity (norm). Electrodes Pinc Insulator 1.0 Xe Spectrum 0.8 Mo / Si Mirror Reflectivity Wavelengt (nm). Open source geometry Hig collection angle (up to 2π steradian) Hig gas flow, good clearing of discarge zone for ig repetition rate operation All solid state pulse power system Reliable (based on Cymer s DUV excimer laser tecnology) Solid state switcing / magnetic pulse compression generate fast pulses for DPF Scalable to ig repetition rates (6 10 khz) Contains output magnetic switc for reliable ig repetition rate Source element flexibility Xenon is baseline design DPF also works wit Litium or Tin 5

6 EUV Ligt Source System Development Areas Pulsed Power development Power scaling, termal engineering Hig repetition rate operation, gas dynamics Plasma optimization, electrode geometries Metrology and EUV optics Lifetime and debris mitigation Alternative source elements 6

7 Pats to Higer EUV Output Power Output power can be scaled by increasing repetition rate, conversion efficiency and collection efficiency Increased repetition rate requires development in several areas improved pulse power system increased termal extraction capability optimized gas dynamics optimized electrode materials and geometry advanced pre-ionization system Increased conversion efficiency may be attained by optimizing plasma conditions using oter source elements 7

8 SSPPM Development 8

9 EUV DPF SSPPM Development Hig power SSPPM, termal management Lower inductance output drive wit additional pulse compression 9

10 Pulsed Power System Improvements Hig average power power supplies Multiple, parallel 30 kw power supplies provides ~100 kw of initial DC carging voltage after conversion from AC power lines. Resonant carger Energy transfer provides carging of Pulsed Power system wit tigt regulation in 75 µsec to support 10 khz rep-rate operation. Solid-state switcing and magnetic pulse compression, fast,step-up pulse transformer, output magnetic switc Termal management development for 100% duty cycle operation wit liquid cooling of Pulsed Power modules. 10

11 Power Dissipation Analysis for SSPPM Calculated Dissipation in SSPPM Components at 5 khz: C0 Capacitor Deck 500 W Air Cooled IGBTs 1800 W Water Cooled Series Diodes 2500 W Water Cooled Saturable Assist 400 W Air Cooled C1 Capacitor Deck 1300 W Air Cooled LS2 Magnetic Switc 1000 W Water Cooled Transformer 100 W Water Cooled C2 Capacitor Deck 5000 W Air Cooled LS3 Magnetic Switc 1800 W Water Cooled 11

12 FEA Termal Analysis of Output Switc Temperature Temperature Mandrel Core Fin I.D. Baseline design wit water cooling O.D. New design wit water cooling and 0.060" fin inserted between 2 magnetic cores Output magnetic switc temperature reduced by ~ 200 C 12

13 Electrodes Termal Management 13

14 Termal Management of DPF Heating of te source Radiation from plasma into electrodes and camber Radiation from plasma into debris sield, collector Conduction eating from plasma Omic eating of electrodes Electrodes cooling Open cannels water cooling Porous media water cooled Microcannels 14

15 Termal Modeling of Electrode for First Generation Design lpm/12 kw load case corresponds to >3 khz eat load in negative polarity configuration lpm flow rate as been demonstrated Modeling predicts manageable electrode temperatures for 3 khz operation wit first generation cooling design 15

16 Termal Modeling Wit Measured Temperature Profiles Utilizing actual measured temperature distributions for un-cooled electrodes to derive te eat flux distribution on te electrode results in a 2 x increase in te calculated wall temperatures. New calculated temperature profiles sow tat te maximum temperature on te electrode surface coincides wit te region of maximum electrode erosion. 16

17 Prototype of Cymer EUV Source Power Scaling and Termal Engineering Setup 17

18 Calorimetry of Positive and Negative Polarity DPF % of Total Power Removed Solid: Negative Polarity Open Positive Polarity, Inner Electrode, Outer Electrode, Vacuum Vessel Repetition Rate (Hz) Temperature ( C) Heat removal distribution Inner electrode: Pos. ~ 50%; Neg. ~ 35% Outer electrode: Pos. ~ 40%; Neg. ~ 40% Camber: Pos ~ 10%; Neg. ~ 25% Total Power Extracted: 21 kw Inner In Inner Out Outer In 1 Outer Out 1 Outer In 2 Outer Out 2 Outer In 3 Outer Out 3 Outer In 4 Outer Out 4 Vessel In Vessel Out/Lid In Lid Out 1000 Hz 1250 Hz 1500 Hz 1750 Hz 2000 Hz Ti ( d ) First generation porous metal inner electrode test power = 8.4 kw Open cannel inner electrode tested power = 10 kw 18

19 DPF Operation 19

20 Correlation of Potodiode and Imaging CCD Detectors CCD imaging system wit pinole aperture, a series of foil filters and a 45 degree ML mirror for 13.5 nm. Correlation between te EUV energy measured wit a potodiode and te integrated intensity on a CCD detector using a ML mirror Normalized CCD Signal CCD Detector Potodiode Detector Correlation Coefficient = Normalized Potodiode Signal Pulse Number 20

21 EUV Metrology For CW Source Operation EUV monitor wit debris suppression tube Source size measurements wit CCD camera and 45 deg ML mirror 76 Watts of in-band EUV radiation (2 % b.w., into 2 π) obtained at 2 khz repetition rate 3.5 mm lengt (FWHM) 0.35 mm widt (FWHM) 21

22 Energy of Negative Polarity DPF In-Band Energy / pulse (mj/2π /2% BW) Ptot100_EEUV Ptot60_EEUV Ptot40_EEUV Ptot30_EEUV Ptot20_EEUV Xe Flow Rate (au) Maximum CE ~0.5%. Xe injection into a very low pressure buffer gas produces more sperical EUV source. Source size at igest power: 3.0 mm x 0.4 mm. 22

23 DPF Operation at 5 khz 1.4 EUV in band energy (norm.) Energy Pulse number Demonstrated DPF operation at 5 khz in burst mode wit un-cooled electrodes. Optimization is required for electrode geometry, gas recipe and pre-ionization system. 23

24 Dependence of EUV Energy on Coupled Energy at 5KHz EUV In-band Energy in 2pi sr. [J] Recovered Energy 0.01 Correlation Coef. = Stored Energy Correlation Coef. = Dissipated Energy Correllation Coef. = Energy [J] C2 Voltage Anode Voltage Potodiode Voltage variation on output stage < 0.9% in open loop. Cange in energy coupling during te burst, coupling > 90 %. Observed effects may be due to electrode eating during te burst resulting in a cange in local gas density

25 Plasma Modeling 25

26 Elements of MHRDR and Spectra Modeling A MHD model of plasma dynamics is being utilized to model dependencies and scaling in te Cymer dense plasma focus EUV ligt source. Plasma condition are coupled to a collisional-radiative model of Xe emission to predict radiation scaling. Calculated features of te model dynamics are being compared to experimental measurements, including pinc timing, pinc time scaling, pinc size, EUV output scaling, current peak and waveform, inductance. Te goal of plasma modeling effort is to guide design efforts toward an optimum configuration. 26

27 Comparison of Simulation wit Experiment Experimental discarge current, and pinc timing are compared to MHRDR calculations. Two cases for simulation sown are Low inductance, low pressure (blue) Hig inductance, ig pressure (black) Simulation can be made to matc experimental current and pinc timing by reasonable model. Plasma Current (ka) EUV Ligt, Radial KE (AU) Voltage (kv) Experimental vs Calculated Waveforms Capacitor Voltage Current EUV Ligt (Measured) Radial Kinetic Energy Radial Kinetic Energy Fill pressure controls pinc timing Time (ns) Measured Computed: ig fill pressure, ig inductance low pressure, low inductance Circuit parameters control current waveform 27

28 Modeling Plasma Dynamics Radial Kinetic Energy Lengt Radial Kinetic Energy Radial Kinetic Energy Time (ns) 0.2 1E-6 1E-5 Fill Density (kg/m 3 ) Modeling of pinc dynamics as re-produced aspects of te experiment: optimum electrode lengt exists for matc to pulsed power, optimum gas pressure exists, current magnitude for a given driver circuit is witin approximately 30%. 28

29 Pinc Dynamics 29

30 Calculated Spectra at Different Electron Temperatures Hartree-Fock calculations of spectra for Xe 7+ to Xe 12+ at different electron temperatures, including ion stage populations and opacity effects. Comparison of calculated and measured spectrum in te 13.5 nm region at a resolution of λ = 0.02 nm. 30

31 EUV Source Debris and Contamination 31

32 Primary Collector Lifetime: Debris DPP systems can produce te following types of debris: Fast source element ions Fast source element neutrals Source element particles Fast electrode material ions Fast electrode material neutrals Electrode material particles Insulator material Optics lifetime is limited by system contamination: carbon growt due to cracking of ydrocarbons under EUV irradiation oxidation 32

33 1.0x10-9 Limit of turbo pump (experiment) Contamination Study 5.0x10-8 Improved discarge camber 8.0x10-10 Water 4.0x10-8 Water Pressure, torr 6.0x x10-10 Oxygen Pressure, torr 3.0x x10-8 Nitrogen / CO 2.0x10-10 CO 2 1.0x10-8 Oxygen Mass, AMU Magnetically levitated turbo- molecular pump (rated 400l/s for nitrogen, minimal pressure - 2*10-9 torr) Pumping - 8 days and baking - 5 days. Water - 8*10-10 torr Oxygen torr CO torr Mass, AMU Acieved levels: Hydrogen torr Water - 4*10-8 torr Nitrogen/CO- 3*10-8 torr Oxygen - 5*10-9 torr CO 2-2*10-9 torr 33

34 Debris Measurements Sield Test wafer 3 million pulses test. Si wafer was placed beind debris sield. Tin coating (< 5nm) was observed for 2mm, 1cm long cannels. Coating was analyzed by means of Auger and ESCA. Carbon, aluminum, oxygen, xenon, were detected. No signs of tungsten or brass (Cu, Pb, Sn). 34

35 Alternative Source Element: Sn 35

36 Prototype of Cymer EUV Source Alternative Source Elements Setup 36

37 DPF Operation wit Sn Spectral Intensity (AU) 1400 Ar only Sn+Ar EUV CE ~ 1.7% EUV Emission Spectra wit and witout Sn nm Tin line Wavelengt (nm) Initial experiments conducted wit Sn sow conversion efficiencies ~ 2%. Matcing spectrum to 13.5 nm Mo/Si multi layer mirror. 37

38 EUV Source Images for Negative Polarity DPF EUV image wit Xe EUV image wit Sn Operation of Sn in te DPF. Conversion efficiency ~ 2.5%. 38

39 Current Source Performance wit Xe EUV efficiency wit Xe, (2% BW, 2π sr) EUV energy per pulse (2% BW, 2π sr) Average source size (FWHM) Source position stability (centroid) Continuous repetition rate Burst repetition rate Energy Stability Avg. EUV Output Power (2% BW, 2π sr) EUV Output Power, Burst (2% BW, 2π sr) > 0.5% ~ 55 mj ~ 0.4 x 3.0 mm < 0.05 mm, rms 2000 Hz 5000 Hz ~ 7 %, rms 76 Watt 200 Watt 39

40 EUV Power Today Future Required Required Steady State Mode (Xe) (Xe) (Xe) (Sn) Termal Extraction Power (W) Conversion Eff. 0.45% 0.60% 0.70% 2.00% EUV Power (W), 2% bw,2π sr Collection Efficiency 20% 30% 30% 30% Collected EUV (W) Collector Trans. 70% 70% 70% 70% Debris Mitigation 80% 80% 80% 80% SPF 100% 100% 100% 100% Gas Trans. 90% 90% 90% 90% EUV at Interm. Focus (W)

41 Summary of DPF Development Te DPF EUV source configuration as sown continuous improvement in EUV power wit Xe. Higer conversion efficiency may be required for production level source power output, Sn sows ~ 4 times iger CE vs. Xe. Continued work in termal management is te key to iger power output at ig repetition rate and duty cycle. Operation at increasing repetition rate is not likely to be limited by pulsed power performance Burst mode operation at increasing repetition rate requires reoptimization of gas dynamics but does not appear to indicate fundamental limitations Remaining callenges include termal engineering, debris mitigation, EUV emission and source position stability. 41

42 Cymer EUV Source Outlook DPP DPF development ongoing LPP Source elements: Xe, Sn, In, Li Experiments wit Nd:YAG laser at 1064, 532, 355, 266 nm Test pulse duration effects at 248 nm Improve laser beam quality Compare different targets: jet, droplet, pellet Target position control Quantify major mirror erosion mecanisms 42

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