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Lawrence Livermore National Laboratory a job On a petawatt-class thulium laser that is said to be 10 times more efficient than the CO2 lasers used in UV instruments and could replace CO2 lasers in lithography systems many years down the road.
The LLNL-led initiative will evaluate Large aperture thulium (BAT) laser technology. To enhance the efficiency of the UV source by approximately ten times compared to current industry-standard CO2 lasers. This advance could pave the way for a new generation of “beyond-UV” lithography systems that produce chips faster and with lower energy. Of course, implementing BAT techniques in semiconductor production will require significant infrastructure changes, so it remains to be seen how long it will take for it to come to fruition; Current EUV systems have been developed over decades.
One of the peculiarities of extreme UV lithography is the extreme power consumption of the current generation of Low-NA EUV litho systems and the next generation of High-NA EUV: the tools consume 1170 and 1400 kilowatts, respectively. UV lithography tools consume such huge amounts of energy because they rely on high-energy laser pulses to vaporize tiny droplets of tin (at a temperature of 500,000°C) to form a plasma that emits 13.5 nanometers of light. Generating these pulses in the tens of thousands per second requires massive laser infrastructure and cooling systems. Generating and processing tin droplets also requires energy.
Additionally, vacuum requirements to prevent UV light from being absorbed by the air add to the overall energy use. Finally, since advanced mirrors in UV instruments reflect only a small portion of UV light, lasers must become more powerful to increase production capacity.
Lawrence Livermore’s team of researchers is testing whether the technologies behind the BAT laser — built on thulium-doped lithium yttrium fluoride and capable of petawatt-class output — can raise the energy efficiency of current UV instruments. Unlike the CO2 laser, which operates at a wavelength of about 10 microns, this system operates at a wavelength of about 2 microns, according to LLNL. This theoretically enables increased plasma-to-UV conversion efficiency when interacting with tin droplets. The diode-pumped solid-state technology used in BAT systems can also provide better overall electrical efficiency and heat management than gas-based CO2 setups.
First, the researchers aim to pair the compact, high-repetition-rate BAT laser (with different types of pulses) with systems that produce UV light to test how a laser that sends out joule-level pulses at a 2-micron wavelength interacts with tin droplets.
“We have performed theoretical plasma simulations and laser demonstrations over the past five years that have laid the foundations for this project,” said Brendan Regan, a laser physicist at LLNL. “Our work has already had a significant impact in the UV lithography community, so we are now excited to take this next step.”
The energy consumption of modern UV instruments and plants led the company’s industry analysts TechInsights to sound the alarm On the energy consumption of semiconductor factories. These plants are expected to consume 54,000 gigawatts of energy annually by 2030 – more than what Singapore or Greece consume annually. If next-generation Hyper-NA EUV lithography comes to market, power consumption could be even higher. As such, we can expect the industry to continue to look for more energy-efficient technologies to power future UV machines.
