Aleksandr Yu. Vinokhodov

Development of high-power EUV sources for lithography

We report on the experimental status of the development of gas discharge produced plasma EUV sources for lithography based on the Z-pinch concept. The plasma size of approximately 1.3 mm X 1.5 mm has been matched to come close to the requirements resulting from the etendue of the optical system. The spatial stability of the plasma size as well as the plasma center is better than 15 percent standard deviation. The solid angle of emission is 1.8 sr, i.e. +/- 45 deg. The sources can be operated continuously at 1000 Hz repetition frequency and provide an EUV in-band power of 10 W in 1.8 sr. Spectral measurements providing in-band and out-of-band spectral distribution of the source are discussed.

High-power EUV sources for lithography: a comparison of laser-produced plasma and gas-discharge-produced plasma

Next generation semiconductor chip manufacturing using extreme ultraviolet (EUV) lithography requires a brilliant radiation source with output power between 50 W and 120 W in intermediate focus. This is about five to ten times higher power than that of current DUV excimer lasers used in optical lithography. Lifetime and cost of ownership however, need to be comparable to todays technology. In the present paper experimental results of both laser produced plasma and gas discharge produced plasma EUV source development at XTREME technologies - the EUV joint venture of Lambda Physik AG, Goettingen, and Jenoptik LOS GmbH, Jena, Germany - are presented. Source characterization has been performed with calibrated metrology tools for measurement of energy, power, size, spectra and stability of the EUV emission. The laser plasma investigations are performed with a 1st experimental facility comprising a commercial 40 W Nd:YAG laser coupled to a liquid xenon-jet target system, which was developed by XTREME technologies. The EUV in-band power emitted from the 0.25 mm diameter plasma into 2p solid angle is 0.2 W, the conversion efficiency amounts 0.5 percent. Estimated EUV emission parameters using a 500 W laser for plasma generation to be installed in spring 2002 are discussed. The gas discharge EUV sources described here are based on efficient Xenon Z-pinches. In the 3rd prototype generation the plasma pinch size and the available emission angle have been matched to the etendue of the optical system of 2-3 mm2. The solid angle of emission from the pinch of 1.3 mm x 1.5 mm amounts 1.8 sr. The Z-pinch EUV source can be operated continuously at 1000 Hz with an in-band output power of 10 W in 1.8 sr. This corresponds to 4.5 W in intermediate focus, if no spectral purity filter is needed. The power emitted into a solid angle of 2p sr is 35 W. Emission energy stability ranges between 1 percent and 4 percent standard deviation. Spectral, temporal as well as spatial emission characteristics of the discharge source in dependence on the gas discharge geometry have been evaluated. The potentials as well as limits for power scaling of the two technological source concepts are discussed.

Compact Z-pinch EUV source for photolithography

According to Sematech Internationals analysis extreme ultraviolet (EUV) photolithography is one of the most promising approaches for next generation lithography (NGL). The insertion point of NGL is likely at the 50 nm node. To establish EUV lithography all basic technologies have to be developed t material suppliers, source suppliers, coating manufacturers, optics, lens and tool manufacturers, mask houses, pellicle manufacturers and resist suppliers over the next years. To achieve the required throughput in production various concepts of EUV sources are currently under investigation. Here we discuss new results of design studies on gas discharge Z-pinch sources. Form the EUV source 1 W output power at 100 Hz repetition rate could be obtained in continuous operation. Pulse energy stability is 4% (sigma). In burst operation repetition rate of up to 400 Hz is possible with the current design.

Kilowatt-range high-repetition-rate excimer lasers

High-power operation of excimer lasers was investigated using UV-preionization schemes based on a dielectric surface creeping discharge. The design and operation of the high average power excimer laser systems are described. A large-aperture (10 X 7 cm2) XeCl laser with UV preionization can produce 10 J per pulse at a repetition rate of up to 100 Hz. When the aperture was decreased, the XeCl laser operated at repetition rates of up to 500 Hz and could produce average output power of more than 600 W.

High-average-power excimer lasers

A review of recent achievements and new tendencies in the development high energy, high repetition rate excimer lasers will be presented. The paper mainly focuses on the features of KrF, XeCl lasers with different combinations of output energy x pulse repetition frequency, for example: 1 J X 600 Hz (KrF); 3 J X 200 Hz or 10 J X 100 Hz (XeCl), which have been developed as candidates for industrial applications.

Prospects for high-power high-repetition-rate industrial excimer lasers

Recent progress in excirner laser technology developed at TRINITI is reported. The key of the technologT is a combination of simple reliable UV preionizer based on creeping discharge on surface of a sapphire plate and the compact highly efficient gas flow system. This technology allows to develop very compact, high power, high repetition rate models of excimer lasers capable to deliver stabilized average power up to 500W (XeC1, KrF), 250W (ArF) and realise pulse repetition rate of more then 5 kHz..

Development of next generation excimer lasers for industrial applications

The report reviews the results of developments of the perspective excimer lasers which has been carried out in Pulsed Laser System Laboratory at TRINITI. We present parameters of XeCl laser (λ=308 nm) with average power up to 500 W and ArF laser (λ=193 nm) with a pulse repetition rate ≥6 kHz.

Recent advances in the development of coherent and incoherent UV and EUV discharge sources

We report on the experimental status of the development of compact high power (up to 500 W) high repetition rate (up to 6 kHz) excimer lasers and discharge produced plasma sources radiating in an extreme ultraviolet (EUV) region. EUV power more than 70 W (around 13.5 nm wavelength, a bandwidth of 2%) into 2π sr at 1250 Hz was obtained for continuous operation of a source.

Theoretical and experimental investigations of the 1-kW XeCl laser with UV pre-ionization

This paper describes recent results achieved in the development of a compact 1 kW XeCl laser GEFEST - 4, intended for using in various technologies. The laser was designed to obtain various output combinations of pulse energy (epsilon) and pulse repetition rate (f) with the same average output power P equals epsilon times f approximately equals 1 kW. Different excitation system for discharges with various cross sections are considered. Using the excitation system with UV preionization on the base of creeping discharge on dielectric surface we obtained an average output power of 1 kW at a pulse repetition rate of 100 Hz and 150 Hz (10 J multiplied by 100 Hz and 6.6 J multiplied by 150 Hz) with an efficiency of 1.65%. To obtain the combination of parameters 3.3 J multiplied by 300 Hz a spiker-sustained excitation system is developed which ensures in monopulse mode a pulse energy of 3.6 J with an efficiency of 3.6%. For this system the influence of macro- and micro-instabilities in discharge on energy and duration of the laser pulse is investigated. Capability of obtaining other combinations of epsilon and f at the epsilon multiplied by f approximately equals 1 kW is briefly considered.

Intense high-repetition-rate excimer lasers and applications

Building of high average output power excimer lasers requires the solution of several complex problems. The main challenge is the creation of a uniform discharge which can be easily reproduced even at high pulse repetition rates. Some approaches to solving this problem are discussed. They resulted in creation of lasers with aperture of 4 sq cm operating at 1 kHz producing the output of 420 W at 308 nm. A large-aperture XeCl laser can produce 10 J per pulse at 50 Hz.