EUV lithography and etching rooms require ISO class 1 clean rooms. Those can have a maximum of 10 particles of size 0.1 microns per cubic meter.
While a shopping mall can get away with 2 - 4 air changes per hour, an ISO class 1 clean room requires 400-600 an hour, or about 10 a minute. Airflow needs to also be controlled: vertical and laminar. Every human entering the cleanroom needs to undergo an air shower with speeds of 60-90 mph to shear off loose skin flakes, hair and lint. This area needs to maintain constant positive air pressure to repel outside dust as humans move in and out.
In the EUV lithography systems, temperature control is measured in milliKelvins (0.001 C). If a wafer stage has a temperature variation of 0.05 C, the silicon expands by a few nanometers and the multimillion dollar batch is toast. Meanwhile in the same room, the EUV machine is generating extreme ultraviolet light using a plasma light source that gets to above 200,000 C. That's 40x hotter than the surface of the sun.
> I always thought of these as high-precision, not-too-high-volume processes
EUV rooms are churning out about 150 wafers an hour, 24/7. That sounds like not too high of a volume, but each wafer is about 500 cpus. So 75,000 cpus an hour.