The type of equipment ASML produces generally gets brought in at a specific time during the construction. They kinda build the cleanrooms around ASML's machines instead of bringing them in afterwards.

Retooling for EUV (or any new generation of such equipment) is very hard. Most (if not all) foundries build new factories rather than retooling old ones.

> They kinda build the cleanrooms around ASML's machines instead of bringing them in afterwards.

I know they're massive, but do you have a source for this? I was under the impression that construction and tool installation are two distinctly separate phases of construction due to the requirements for an immaculate environment. Also, my understanding is that companies like to bring the tools in as late as possible to shorten the delay between capex outlay (tools are expensive) and first production.

My source for this is my professors at the TU/e in Eindhoven and guest lecturers from ASML (TU/e is the closest university to the ASML campus in Veldhoven).

Unfortunately I don't have a more reliable source on that though.

> Is there any reason they couldn’t just start with multipatterning 193nm immersion?

Time, yields, line size.

Quadruple patterning quadrupples the lithography steps counts. And quadrupples thermal cycles. Which adds more than 4x impact on the number of bad wafers.

100% - 2% * 4 != 100% * 0.98⁴

You need 4x the equipment to complete the same volume of wafers in the same time, which means 4x the line length.

Retooling of anymuch modern fabs is not economical.

I don't see much retooling for anything below 45nm, if not 65nm.

multipatterning DUV will get you up to a point if thats what you were asking. You cant reach 5nm with that. (if that were possible you wouldnt see everyone jumping on ASMLs euv bandwagon)

As for lightsource, sure, that was/is a US company, but there's a lot more to a machine then just the light source.