We recently looked at a novel approach used by Xtreme to generate enough photons for EUV lithography. Just last week, there was a meeting of EUV folks to update their latest results. I talked with Olivier Semprez about what Xtreme reported.
The goal here is to provide enough power to process 60 wafers/hr. That comes to 100 W with at least a 60% duty cycle.
The duty cycle issue comes from the logistics of exposing wafers. The scanner will scan across a wafer while exposing, and then will need to move to a new row, or perhaps a new wafer. The photons can be “blanked” during those transitions (and probably should be – any power used during that time is wasted). So the duty cycle refers to the amount of time that the source is on vs. blanked, and the goal is that the source be able to sustain a 60% duty cycle.
It turns out that, while LPP has some specific issues that require giving the source a break every now and then, the LDP setup can run continuously for hours if needed. So duty cycle isn’t an issue.
Specifically, they achieved 30 W at 100% duty cycle. They also got to 37% with a 50% duty cycle. Whoa! Wait, I thought we just said duty cycle doesn’t matter for them? Well, it doesn’t as far as photon generation goes. Apparently, it does matter as far as measuring them goes – they have to give the sensors a break so they don’t burn them out.
They’ve also found that the stability of the delivered dose is within specifications.
Meanwhile, they’re planning a demonstration of 50 W by the end of the year.
Of course, an obvious question is, how are they going to get from 30 to 100 W? There are three elements to that:
- Faster laser pulsing (which also means running the wheels faster to replenish the tin more quickly)
- A higher power supply
- Better cooling, although apparently the current cooling setup should be sufficient to get to 100 W; at some point, if they want to exceed that, they’ll need to make some changes.
Of course, they’ll also need to figure out how to measure this…