They can do 7nm and 5nm. Multiple patterning basically. I don't know when it doesn't scale anymore. Moat likely 4x patterning is the max you want to do.

If you didn't care about exposure time, you could build 2nm chips with brute-force electron beam lithography. But the limited throughput confines EBL to research and very low-volume applications. ASML's EUV-based processes are what permit industrial-level scaling, ultimately because parallel beams of electrons repel each other while parallel beams of photons don't.

I don't personally understand why suitable EUV light sources are so hard to build, but evidently, they are. It sounds like a big deal if China is catching up in that area.