Extreme ultraviolet (EUV) radiation is seen as the most promising candidate for the next generation of lithography and
semiconductor chip manufacturing for the 32 nm node and below. The paper describes experimental results obtained with
discharge produced plasma (DPP) sources based on pinch effect in a Xe and Sn vapour as potential tool for the EUV
lithography. Problems of DPP source development are discussed.
Xenon-fueled gas discharge produced plasma (DPP) sources were integrated into Micro Exposure Tools already in 2004.
Operation of these tools in a research environment gave early learning for the development of EUV sources for Alpha
and Beta-Tools. Further experiments with these sources were performed for basic understanding on EUV source
technology and limits, especially the achievable power and reliability. The intermediate focus power of Alpha-Tool
sources under development is measured to values above 10 W. Debris mitigation schemes were successfully integrated
into the sources leading to reasonable collector mirror lifetimes with target of 10 billion pulses due to the effective debris
flux reduction. Source collector mirrors, which withstand the radiation and temperature load of Xenon-fueled sources,
have been developed in cooperation with MediaLario Technologies to support intermediate focus power well above
10 W. To fulfill the requirements for High Volume chip Manufacturing (HVM) applications, a new concept for HVM EUV
sources with higher efficiency has been developed at XTREME technologies. The discharge produced plasma (DPP)
source concept combines the use of rotating disk electrodes (RDE) with laser exited droplet targets. The source concept
is called laser assisted droplet RDE source. The fuel of these sources has been selected to be Tin. The conversion
efficiency achieved with the laser assisted droplet RDE source is 2-3x higher compared to Xenon. Very high pulse
energies well above 200 mJ / 2&pgr; sr have been measured with first prototypes of the laser assisted droplet RDE source. If
it is possible to maintain these high pulse energies at higher repetition rates a 10 kHz EUV source could deliver
2000 W / 2&pgr; sr. According to the first experimental data the new concept is expected to be scalable to an intermediate
focus power on the 300 W level.
In the paper we give an update about the development status of gas discharge produced plasma (GDPP) EUV sources at XTREME technologies.
Already in 2003 first commercial prototypes of xenon GDPP sources of the type XTS 13-35 based on the Z-pinch with 35 W power in 2π sr have been delivered and integrated into micro-exposure tools from Exitech, UK. The micro-exposure tools with these sources have been installed in industry in 2004. The first tool has made more than 100 million pulses without visible degradation of the source collector optics.
For the next generation of full-field exposure tools (we call it Beta-tools) we develop GDPP sources with power of > 10 W in intermediate focus. Also these sources use xenon as fuel which has the advantage of not introducing additional contaminations. Here we describe basic performance of these sources as well as aspects of collector integration and debris mitigation and optics lifetime.
To achieve source performance data required for high volume chip manufacturing we consider tin as fuel for the source because of its higher conversion efficiency compared to xenon. While we had earlier reported an output power of 400 W in 2π sr from a tin source we could reach meanwhile 800 W in 2π sr from the source in burst operation. Provided a high power collector is available with a realistic collector module efficiency of between 9% and 15 % these data would support 70-120 W power in intermediate focus. However, we do not expect that the required duty cycle and the required electrode lifetimes can be met with this standing electrode design Z-pinch approach.
To overcome lifetime and duty cycle limitations we have investigated GDPP sources with tin fuel and rotating disk electrodes. Currently we can generate more than 200 W in 2π sr with these sources at 4 kHz repetition rate. To achieve 180 W power in intermediate focus which is the recent requirement of some exposure tool manufacturers this type of source needs to operate at 21-28 kHz repetition rate which may be not possible by various reasons.
In order to make operation at reasonable repetition rates with sufficient power possible we have investigated various new excitation concepts of the rotating disk electrode configurations. With one of the concepts pulse energies above 170 mJ in 2π sr could be demonstrated. This approach promises to support 180 W intermediate focus power at repetition rates in the range between 7 and 10 kHz. It will be developed to the next power level in the following phase of XTREME technologies' high volume manufacturing source development program.
We report the perspective development at TRINITI of the UV and IR lasers. Results of experimental investigations of the following lasers are presented: ArF laser (λ = 193 nm) with average power up to 100 W and high repetition rate, CO-laser (λ = 5.3 ÷ 6.6 μm) with average power up to 50W and CO<sub>2</sub>-laser (λ = 10.6 μm) with laser pulse duration 3 - 5 μs and energy per pulse ~5J.
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.
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.
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.
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 today's 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.
According to Sematech International's 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.
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..
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.
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.
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.
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.