More light, higher productivity
Having demonstrated a throughput of 125 wafers per hour, EUV lithography moves closer to high-volume manufacturing
ASML’s EUV lithography team in Veldhoven has demonstrated the throughput specification of 125 wafers per hour (wph) on an NXE:3400B system. Having already proven the other performance specifications for EUV, including imaging quality, overlay and focus, throughput was the final key spec that needed to be demonstrated.
System wafer throughput is dependent on several parameters including the amount of power the EUV light source can generate. This is because an exposure has to happen with a certain amount of energy, the ‘dose’. The more EUV photons are available for exposure, the faster this dose can be delivered to the wafer, and thus the higher the throughput.
It all starts with a powerful CO2 laser. In the source, the CO2 laser beam hits a target of molten tin, turning it into plasma and generating EUV light.
Generating the required power level was more complex than originally thought. But just a few weeks ago, 250 W of source power was measured on a test system in ASML’s San Diego research labs.
“We didn’t get here the way we thought we would,” says Alex Schafgans, principal scientist. “We thought we would have to build more powerful lasers. Instead, we learned how to convert plasma into EUV light more efficiently. The biggest challenge then became controlling the laser power we already had,” explains Alex.
Once we knew we could generate 250W, the technology needed to be integrated into an EUV source in Veldhoven to demonstrate that it could let the scanner run at 125 wph. And that’s exactly what has now been achieved.
Hans Meiling, Vice President EUV Service- and Product Marketing and with the EUV program since its early days, recalls how far we’ve come: “I remember vividly that some of the first exposures on the Alpha Demo Tools (the first prototype EUV machines) in early 2006 took 800 seconds per field. I remember the number, because the TWINSCAN software timed out, with the message ‘exposure takes too long’! So with 96 fields on a wafer it would have taken 21.3 hours to expose a whole wafer, that’s 0.047 wph. At 125 wph, which translates to 0.3 seconds per field, that’s >2,600 times faster!”
Now that we have achieved 125 wph, we are focusing on ensuring that our EUV systems are stable and our customers can achieve the availability they need for high volume manufacturing.
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