We are developing a CO2 laser driven Tin plasma EUV source for HVM EUVL. This approach enables cost-effective EUV power scaling by high-conversion efficiency and full recovery of Tin fuel. The RF-excited, multi 10 kW average power pulsed CO2 laser system is a MOPA (master oscillator power amplifier) configuration and operates at 100 kHz with 20 ns pulse width. The EUV light source is scalable to in-band 200 W IF power with a single 20-kW CO2 laser beam. EUV chamber is kept uncontaminated by using a small size droplet target and effective Tin exhaust by magnetic plasma guiding. Characterization of the plasma flow in uniform magnetic field was studied by monitoring the motion of Tin plasma stream in a large vacuum chamber, depending on the magnetic flux up to 2 T. Topics relevant for HVM source is reported on continuous operation and Tin vapor evacuation.
We are developing a high power CO2 laser system for a LPP EUV light source. Recent theoretical and experimental data
demonstrate the advantages of the combination of a CO2 laser with a Sn target including the generation of a high CE and
low debris plasma with low energy ions and low out-of-band radiation. Our laser system is a short pulse CO2 MOPA
(Master Oscillator Power Amplifier) system with 22 ns pulse width and multi kW average power at 100 kHz repetition
rate. We achieved an average laser power of 8 kW with a single laser beam having very good beam quality. A EUV in-band
power of 60 W at the intermediate focus was generated irradiating a rotating tin plate with 6 kW laser power.
We are developing a laser produced plasma light source for high volume manufacturing (HVM) EUV lithography. The
light source is based on a high power, high repetition rate CO2 laser system, a tin target and a magnetic ion guiding for
tin treatment. The laser system is a master oscillator power amplifier (MOPA) configuration. We have achieved an
average laser output power of 10 kW at 100 kHz by a single laser beam with good beam quality. EUV in-band power
equivalent to 60 W at intermediate focus was produced by irradiating a tin rotating plate with 6 kW laser power. This
light source is scalable to more than 200 W EUV in-band power based on a 20-kW CO2 laser. Collector mirror life can
be extended by using droplet target and magnetic ion guiding. Effectiveness of the magnetic ion guiding is examined by
monitoring the motion of fast Sn ion in a large vacuum chamber with a maximum magnetic flux density of 2 T.
We are developing a laser produced plasma light source for high volume manufacturing (HVM) EUV lithography. The
light source is based on a short pulse, high power, high repetition rate CO2 master oscillator power amplifier (MOPA)
laser system and a Tin droplet target. A maximum conversion efficiency of 4.5% was measured for a CO2 laser driven Sn
plasma having a narrow spectrum at 13.5 nm. In addition, low debris generation was observed. The CO2 MOPA laser
system is based on commercial high power cw CO2 lasers. We have achieved an average laser power of 7 kW at 100 kHz
by a single laser beam with good beam quality. In a first step, a 50-W light source is under development. Based on a 10-kW CO2 laser, this light source is scalable to more than 100 W EUV in-band power.
We evaluated Sn debris generated from a CO2 laser (10.um) and a Nd:YAG laser (1064nm) plasma. Experiments were
performed with bulk Sn-plates (t=1mm) and freestanding Sn-foils (t=15um). Quartz Crystal Microbalances (QCM) were
used for debris analysis. We observed a drastically lower deposition for the CO2 laser driven plasma compared with the
Nd:YAG laser plasma. In addition, several Sn coated targets with different Sn thickness were investigated for the CO2
drive laser with respect to the generated plasma debris. In general, a 100nm Sn coated glass target generated more debris
than the solid Sn target. Especially, we observed for the Sn-plate target that the deposition rate is smaller than the erosion
(sputter) rate caused by the plasma ions.
We develop a laser produced plasma light source for high volume manufacturing (HVM) EUV lithography. The light
source is based on a short pulse, high power, high repetition rate CO2 master oscillator power amplifier (MOPA) laser
system and a Tin droplet target. A maximum conversion efficiency of 4.5% was measured for a CO2 laser driven Sn
plasma having a narrow spectrum at 13.5 nm. In addition, low debris generation was observed. The CO2 MOPA laser
system is based on commercial high power cw CO2 lasers. We achieve an average laser power of 3 kW at 100 kHz with a
single laser beam that has very good beam quality. In a first step, a 50-W light source is developing. Based on a 10-kW
CO2 laser this light source is scalable to more than 100 W EUV in-band power.
Extreme ultraviolet lithography (EUVL) is the candidate for next generation lithography to be introduced by the
semiconductor industry to HVM (high volume manufacturing) in 2013. The power of the EUVL light source has to be at
least 115W at a wavelength of 13.5nm. A laser produced plasma (LPP) is the main candidate for this light source but a
cost effective laser driver is the key requirement for the realization of this concept. We are currently developing a high
power and high repetition rate CO2 laser system to achieve 50 W intermediate focus EUV power with a Tin droplet
target.
We have achieved CE of 2.8% with solid Tin wire target by a transversely excited atmospheric (TEA) CO2 laser MOPA
system with pulse width, pulse energy and pulse repetition rate as 10~15 ns, 30 mJ and 10 Hz, respectively. A CO2 laser
system with a short pulse length less than 15 ns, a nominal average power of a few kW, and a repetition rate of 100 kHz,
based on RF-excited, fast axial flow CO2 laser amplifiers is under development. Output power of about 3 kW has been
achieved with a pulse length of 15 ns at 130 kHz repletion rate in a small signal amplification condition with P(20) single
line. The phase distortion of the laser beam after amplification is negligible and the beam can be focused to about 150&mgr;m
diameter in 1/e2. The CO2 laser system is reported on short pulse amplification performance using RF-excited fast axial
flow lasers as amplifiers. And the CO2 laser average output power scaling is shown towards 5~10 kW with pulse width
of 15 ns from a MOPA system.
Laser produced plasma is the candidate for high quality, 115 W EUV light source for the next generation lithography. Cost effective laser driver is the key requirement for the realization of the concept as a viable scheme. A CO2 laser driven LPP system with a Xenon or Tin droplet target, is therefore a promising light source alternative. We are developing a high power and high repetition rate CO2 laser system to achieve 10 W intermediate focus EUV power. High conversion efficiency (CE) from the laser energy to EUV in-band energy, is the primarily important issue for the concept to be realized. Experimental and numerical simulation analysis of a Xenon plasma target shows that a short laser pulse less than 15 ns is necessary to obtain high CE by a CO2 laser. This paper describes on the development of a CO2 laser system with a short pulse length less than 15 ns, a nominal average power of a few kW, and a repetition rate of 100 kHz based on RF-excited, axial flow CO2 laser amplifiers. Output power of 1 kW has been achieved with a pulse length 15 ns at 100 kHz repletion rate in a small signal amplification condition. The phase distortion during the amplification is negligible and the beam is focused down to 100μm diameter onto a fast Xenon jet. The conceptual design of the CO2 laser system for LPP EUV light source, and amplification performance in short pulse using RF-excited axial flow laser as amplifiers, are reported. Additional approach to increase the amplification efficiency is discussed.
A CO2 laser driven Xe droplet plasma is presented as a light source for EUV lithography. A short-pulse TEA CO2 master oscillator power amplifier system and a pre-pulse Nd:YAG laser were used for initial experiment with 0.6% of CE from a Xe jet. A target technology is developed for high average power experiments based on a Xe droplet at 100kHz. Magnetic field ion mitigation is shown to work well in the pre-pulsed plasma combined with a CO2 laser main pulse. This result is very promising with respect to collector mirror lifetime extension by magnetic field mitigation. A master oscillator power amplifier (MOPA) CO2 laser system is under development with a few kW and 100 kHz repetition rate with less than 15ns laser pulse width using a waveguide Q-switched CO2 laser oscillator and RF-excited fast axial flow CO2 laser amplifiers.
Laser produced plasma EUV source is the candidate for high quality, 115 W EUV light source for the next generation lithography. Cost effective laser driver is the key requirement for the realization of the concept as a viable scheme. A CO2 laser driven LPP system with a Xenon droplet target is therefore a promising light source alternative for EUV. We are developing a high power and high repetition rate CO2 laser system to achieve 10 W intermediate focus EUV power.
High conversion efficiency (CE) from the laser energy to EUV in-band energy is the primarily important issue for the concept to be realized. Numerical simulation analysis of a Xenon plasma target shows that a short laser pulse less than 15 ns is necessary to obtain a high CE by a CO2 laser. This paper describes on the development of a CO2 laser system with a short pulse length less than 15 ns, a nominal average power of a few kW, and a repetition rate of 100 kHz, based on RF-excited, axial flow CO2 laser amplifiers.
Output power of 1 kW has been achieved with a pulse length 15 ns at 100 kHz repletion rate in a small signal amplification condition with P(20) single line. The CO2 laser system is reported on the conceptual design for a LPP EUV light source, and amplification performance in CW and short pulse using RF-excited axial flow lasers as amplifiers. Additional approach to increase the amplification efficiency is discussed.
Laser produced plasma EUV source is the candidate for high quality, 115 W EUV light source for the next generation lithography. Cost effective laser driver is the key requirement for the realization of the concept as a viable scheme. A CO2 laser driven LPP system with a Xenon droplet target is therefore a promising light source alternative for EUV. We are developing a high power and high repetition rate CO2 laser system to achieve 10 W intermediate focus EUV power. High conversion efficiency (CE) from the laser energy to EUV in-band energy is the primarily important issue for the concept to be realized. Numerical simulation analysis of a Xenon plasma target shows that a short laser pulse less than 15 ns is necessary to obtain a high CE by a CO2 laser. This paper describes on the development of a CO2 laser system with a short pulse length less than 15 ns, an average power of a few kW, and a repetition rate of 100 kHz based on RF-excited, axial flow CO2 laser modules. Various issues are reported on the laser system design, namely l00W seeder, parasitic oscillation suppression, small signal gain and saturation fluence, and beam quality. Additional approach to increase the amplification efficiency is discussed.
Acknowledgement: This work was supported by NEDO.
A CO2 laser driven Xe jet plasma is presented as light source system for EUV lithography. A short-pulse TEA C02 master oscillator power amplifier system and a pre-pulse Nd:YAG laser were used for plasma generation. The dependence of EUV plasma parameters, e.g. conversion efficiency, plasma image and in-band and out-of-band spectra, on the delay time between the pre-pulse and the main pulse laser was investigated. A maximum conversion efficiency of 0.6 % was obtained at a delay time of about 200 ns. In addition, characteristics of fast ions were measured by the time-of-flight method. The peak energy of the fast ion energy distribution decreased significantly at delay times larger than 200 ns. This result is very promising with respect to collector mirror lifetime extension by magnetic field mitigation.
The status of the next generation lithography laser produced plasma light source development at EUVA is presented. The light source is based on a Xenon jet target and a Nd:YAG driver laser. The laser, having a master oscillator power amplifier (MOPA) configuration, operates at 10 kHz repetition rate and generates an average output power of 1.5 kW. The fwhm pulsewidth is 6 ns. The EUV system currently delivers an average EUV source power of 9.1 W (2% bandwidth, 2π sr) with a conversion efficiency of 0.6 %. Based on the development it is concluded that solid-state Nd:YAG laser technology can be cost efficiently used to produce 10 W level EUV light sources. In order to generate an average power of 115 W for a future extreme ultraviolet (EUV) light source, however, the cost of a Nd:YAG based LPP source will be too high. Therefore RF-CO2 laser technology will be used. The designed CO2 driver laser system has a MOPA configuration. The oscillator has ns-order pulsewidth and the laser system operates at a repetition rate of 100 kHz. Due to its inert cleanliness Xenon droplets will be the target material.
Collector mirror lifetime evaluation and damage prevention are important technical challenge for the EUV light source
development. High-energy xenon ions emitted from laser-produced EUV plasmas are expected to considerably damage
the collector mirror of the light source. Related to future collector mirror lifetime considerations, fast ions from the laserproduced
plasma have been characterized by time-of -flight (TOF) measurements. Using a low repetition rate 8-ns, 100-
mJ Nd:YAG laser, Xe+ to Xe6+ ions were observed with Xe2+ being the main charge state. In addition, the effects of fast
ions on Mo/Si multilayer mirrors have been studied using a Xe ion gun. Ion sputtering of the multilayer structure is the
main damage mechanism but layer boundary mixing and surface roughness increase are also observed. A magnetic
confinement scheme is evaluated for ion mitigation.
The main technological challenge of a future extreme ultraviolet (EUV) light source is the required average power of
115W at the intermediate focus. High repetition rate laser produced plasma (LPP) sources are very promising to face
this challenge. We report the current status of the laser produced light source system we started to develop in 2002. The
system consists of the following main components: The plasma target is a liquid xenon jet with a maximum diameter of
50 micrometer and a velocity of more than 30 m/s. A Nd:YAG laser oscillating at 1064 nm produces the plasma. The
laser is a master oscillator power amplifier (MOPA) configuration with a maximum repetition rate of 10 kHz and an
average power of 1kW. The EUV system currently delivers an average EUV in-band power of 4 W (2% bandwidth, 2π
sr) having a stability of 0.54 % (1σ, 50-pulse moving average). In order to evaluate a further increase of the repetition
rate, xenon jet characteristics and EUV plasma images have been investigated at 10 kHz. In addition, a conversion
efficiency of 0.67% (2% bw, 2π sr) has been obtained at low repetition rate operation. This paper presents the progress
of our LPP light source development.
Important design factors are evaluated for a high average power, clean EUV light source by laser produced plasma. The basic requirements are high average power, high stability, and long lifetime, and these are closely relating with absorption loss by xenon, repetition rate, and fast ion generation. These subjects are evaluated based on experimental data and analytical model of a laser produced xenon plasma.
The Extreme UV Lithography System Development Association (EUVA) was established in Japan in May 2002 and is supported by the Ministry of Economy, Trade and Industry (METI). EUVA started the light soruce development in September 2002. This development is done by the assocaition members Gigaphoton, Ushio, Komatsu, Canon, Nikon, the National Institute of Advanced Industrial Sciecne and Technology (AIST) and several Japanese universities. The target of the four-year project is the development of a EUV light source with 10W clean focus point power. For the end of the fiscal year 2003 the development of a 4W EUV light source (clean focus point power) is planned. Both, Laser-Produced-Plasma (LPP) and Discharge-Produced-Plasma (DPP) EUV light sources are investigated at first. Our group at the EUVA Hiratsuka R&D Center is working on LPP sources. We are currently focusing on the development of a driver laser and a liquid Xenon plasma target. The laser is a Nd:YAG MOPA (Master Oscillator and Power Amplifier) system oscillating at 1064 nm. Average power, repetition rate and pulse duration of the laser system are 500 Watt, 10 kHa and 30nsec, respectively. The Xenon liquefication system operates at a maximum pressure of 5MPa and a temperature range between 160 K and 190 K. The pressure inside the vacuum chamber is below 0.1Pa during system operation. This paper presents the current status of the EUV system component development as well as first experimental results of generated EUV radiation.
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