Here is the Veritasium video where they review ASML's EUV lithography in depth: https://www.youtube.com/watch?v=MiUHjLxm3V0 https://www.youtube.com/watch?v=MiUH

Here is the Veritasium video where they review ASML's EUV lithography in depth: https://www.youtube.com/watch?v=MiUHjLxm3V0 https://www.youtube.com/watch?v=MiUHjLxm3V0 High thermal conductivity, inertness, and low absorption of the EUV wavelength used are the primary characteristics needed, and purity is needed to eliminate contamination of numerous ultrasensitive stages. AI summarized it as follows: EUV tools require ultra‑high‑purity helium, typically grade 9N (99.9999999%) or better, with strict ppb‑level limits on: Nitrogen, Oxygen, Moisture, Hydrocarbons, Refractory compounds, Particulates. How helium is used: - Cooling the EUV plasma source - Purging and protecting optics - Maintaining inert, ultra‑clean environments - Leak detection