Laser system for LPP EUV light source T.Ohta*, K.Nowak*, - - PowerPoint PPT Presentation

T.Ohta*, K.Nowak*, T.Suganuma*, T.Yokotsuka*, K.Fujitaka*, M.Moriya*, A.Kurosu*, A.Sumitani**, J.Fujimoto*** and H.Mizoguchi*** * KOMATSU ** KOMATSU/EUVA *** Gigaphoton 2010 International symposium on Extreme Ultraviolet Lithography October 17-20, 2010 – Kobe, Japan

Improving efficiency of pulsed CO2 Laser system for LPP EUV light source

Confidential

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Abstract

Laser Produced Plasma (LPP) EUV light source system has been developed for EUV lithography. For this LPP EUV light source system, high pow er pulsed CO2 laser is required as a main drive laser. Current approach for this application is a MOPA system based on a small average pow er pulsed master oscillator and a chain of pow er

• amplifiers. The current MOPA system cannot provide more than 25%
• verall operation efficiency. The main reason is an insufficient

pow er level at initial amplifier stages. In this presentation, some of the pressing technical challenges of the LPP laser driver, such as efficiency and stability of operation, are show n. A new master oscillator system and a pre-amplifier system based on a novel configuration of a RF-excited CO2 laser are the key to high efficiency. Higher energy efficiency and multi-kW

• utput from low input pow er level are predicted and verified in our

experimental pre-amplifier. Feasibility of over 15kW CO2 laser system is show n by numerical modeling.

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OUTLINE

LPP EUV light source CO2 laser system High-quality 20kW CO2 laser system Current status of multi-kW CO2 Multi-line amplification for higher efficiency Initial performance Multi-line oscillator High efficiency Pre-Amplifier Main Amplifier Summary

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EUV source Scanner High power pulsed CO2 laser Beam transfer system EUV collector Plasma Intermediate Focus Plasma guiding magnet Sn supply

LPP EUV light source

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Droplet (liquid) Small fragments (liquid) Plasma (gas) Vaporization CO2 laser irradiation Ionization Guided ion

Neutral

• scattered by ion
• Charge exchange

Ions with low energy trapped by B field Neutrals tapped by charge exchange with ions

Atom 0

Pre-pulse Main-pulse CO2 laser EUV light High power High beam quality

EUV light generation process

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OSC Pre- Amplifier Main AMP1 Main AMP2

20 kW

(200mJ at 100kHz)

Main amplifier

150 W

(1.5mJ at 100kHz)

3 kW

(30mJ at 100kHz)

High pow er pulsed CO2 laser

Combination of short pulsed high rep. rate Osc. and Industrial RF-excited CO2 laser.

CO2 laser system

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CO2 laser system

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■ Laser System

Laser Power ： 13 kW @ 30% duty Pulse Width ： 20 ns Repetition Rate ： 100 kHz Beam quality : M2 <1.2

Main-Amplifier RF-excited CO2 laser Pre-Amplifier RF-excited CO2 laser Oscillator Wave length: 10.6um

• Rep. rate :100kHz

Pulse width :20 ns (FWHM)

13 kW

60W 3 kW

Laser beam profile

EUV100 W at I/F equivalent

Current status of multi-kW CO2

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Laser beam profile

. 1 . 2 . 3 . 4 . 5 . 6 . 7 . 8 . 9 T i m e 5 n s / d i v . I n t e n s i t y

Temporal pulse shape

Pulse duration : 20 ns (FWHM) Pedestal component : <10%

Current status of multi-kW CO2

Pulse shape and beam profile of current system

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Extraction efficiency Energy extraction

Low

Rotation level

• f CO2

Single line Multi-line

High

Efficiency of Multi-line amplification

prediction of 1.3 times higher than Single-line

This work was preformed by Research Institute for Laser Physics,

• St. Petersburg, Russia [V.E. Sherstobitov et al]

Multi-line Amplification Single-line Amplification

Extraction efficiency

CO2 Amplifier CO2 Amplifier Multi-line input

Multi-line amplification for higher efficiency

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Multi-wavelength seeded oscillator

Seeder Amplifier

λ1=Px1 λ2=Px2 (more planned)

(Far-field beam profile) High output beam quality M2<1.3

Multi-line Master Oscillator

Px1 Px2

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0.8 0.85 0.9 0.95 1 1.05 1.1 1.15 1.2 10000 20000 30000 40000 50000 Pulse number Pulse energy [A.U.] P.Energy

Energy stability High pulse energy stability

Closed loop operation

500msec

σ=0.56% (3.5Mpulses)

Multi-line Master Oscillator

Repetition rate : 100kHz

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Pre-amplifier

Input beam Gaussian (M2=1), 16mm 1/e2 diameter

• >3kW output achieved at

150W input pow er

• Good beam quality M 2 <

2 at multi-kW level

• Compact size
• Improved efficiency

Efficient pre-amplification – simulation results

150W >3kW

High efficient Pre-Amplifier

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Main amplifier characteristics – simulation

Good performance at 20kW average pow er predicted Beam tilts and offset typical for good alignment

Main Amplifier

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2 4 6 8 1 1 2 5 1 1 5 2 2 5 3 3 5 i n p u t p

• w

e r [ W ]

• u

t p u t p

• w

e r [ W ]

Input

Main amplifier characteristics : experimental results

>9kW output achieved at 3kW input pow er Good beam quality

Main-AMP

Output beam profile

Main Amplifier

Output

• 3kW

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Osc. Pre- Amplifier

Main amplifier system

100% duty operation modelled Single-lobe high quality spot at focal point (far-field) Output beam profile

20kW operation at 100% duty High beam quality maintained thanks to phase distortion compensation by adaptive optics Improved overall efficiency thanks to efficient pre- amplification Reduced footprint

20kW average pow er system

– simulation results

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500 1000 1500 2000 2500 3000 3500 4000 10 20 30 40 50 60 70 Time (minute) Power (W)

30% Duty operation for 1 Hour

3.4kW@ 30% Stability σ1%

30% duty operation for 1 hr has been achieved. 3.4kW @ 30% is equivalent of 11.3kW at 100% duty cycle operation.

Operation data of current system

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High pow er CO2 laser MOPA system has been achieved w ith :

13kW output pow er at 100kHz, 20ns, duty 30% (on 30msec, off 100msec)

Computer model capable of realistic performance prediction developed Efficient amplification w ith RF-excited CO2 laser – effective pre-amplification + multi-line

Efficiency of Multi-line amplification – prediction of 1.3 times higher than Single-line

20kW system technically feasible

No show stopper at 20kW pow er level (as predicted by numerical modelling)

Summary

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Acknowledgments

This work was supported by the New Energy and Industrial Technology Development Organization

• NEDO- Japan.