Comments by "Grak70" (@Grak70) on "Why 157nm Lithography Failed" video.

  1. Fun story: the first full field functioning scanner ever made for 157 was manufactured by SVG (later acquired by ASML for their catadioptric lens designs). At the time, it was thought the entire lens train, including the condenser optics, would need to be made from ultra-pure calcium fluoride. It was later discovered that fluorine doped quartz would do the trick for all but the few final lens elements. At the time, that one scanner contained the largest concentration of lithography suitable CaF2 in existence. The projection lens was literally worth its weight in gold.
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  2. I assure you, stepper optics makers knew about immersion as a concept from the beginning. The problems were 1) why solve a bunch of novel engineering issues before you absolutely have to and 2) once you have solved them, how to convince fabs that having liquid in contact with their wafers during exposure wouldn’t cause killer defects.
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  3.  @sooocheesy  very true. It’s much more difficult to make a large piece of CaF2 with uniform optical properties than fused silica/quartz. As such, high NA optics were always going to be a problem.
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  4. A lot of the reason 450mm died was the equipment folks NOT wanting to get screwed like they did with 300mm. They still got screwed on 450, but not as bad as if they’d gone all in.
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  5.  @rkan2  ah…no? Lol
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  6. The bigger problem is that 157 is not simpler and wouldn’t really push very far beyond what can be done with KrF and phase shift masks. Even before 157 was de facto cancelled by Intel dropping its support, researchers were struggling to find resists transparent enough for decent patterning. And the search for high RI liquids transparent to 157 that would work for immersion was even less fruitful. Combined with CaF2 birefringence issues even the experts at the time struggled with, and I can’t see this ever being worthwhile or fruitful.
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  7.  @imeakdo7  a lot of papers were written about 157 for a solid decade and it’s still dead. I worked in one of the chemistry labs whose focus was resist formulation when 157 resist screening was hot. It’s not coming back. Inevitably any fluid used for immersion is going to be a fluorinated hydrocarbon and they release fluorine and HF when irradiated. The last thing you want in your quartz optics train is HF. And that’s just one problem with 157 nobody ever figured out a way around. China is not going to solve the myriad problems with 157 when it can’t even produce a 248 scanner that works.
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  8. Lower reticle demagnification reduces active write area on the mask, making defects easier to tolerate. 5x masks still exist at all because legacy equipment requires them. Canon for example used 5x reduction in its steppers, but left the advanced lithography market after dry ArF.
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  9. Gate-all-around (a finFET with the gate completely wrapped around the channel) is already planned by Samsung and TSMC. High-NA EUV is a beast so difficult it’s really more of a successor technology to today’s EUV. Beyond that, there’s not really any clear solution for further pattern scaling. EUV itself was a pipe dream for decades until it became a necessity. We don’t really even have a serious contender for pipe dreams at this point…
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  10.  @imeakdo7  this is an important caveat to anything China does to play catch up. Even their home grown stepper/scanner electromechanics aren’t up to snuff. China is still missing a great deal of basic know-how to even build a KrF scanner worth two farts, let alone try to solve 157’s problems.
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  11. Nikon tried, but they backed the wrong horse on EUV source technology (DPP vs LPP). That coupled with ASML’s patents on dual stage technology to augment the throughput requirements at the low wafer plane powers EUV started at and ASML’s strong partnership with Zeiss who were way ahead on the reflective optics pretty much doomed Nikon’s efforts. Canon, the only other major exposure tool maker, largely dropped off the map after dry ArF and never recovered.
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  12.  @agsystems8220  I’ll believe China will catch up on EUV after they’ve produced, say, a working KrF scanner.
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  13.  @agsystems8220  I’m not saying they can’t do it. They just have a hell of a long row to hoe first.
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  14. I’d be interested to read that if you have a link handy.
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  15. State of the art production is TSMC 3nm and 5nm node and whatever Samsung is calling their equivalent node, I forget.
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