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Comment by DoctorOetker | Hacker News Reader

> South Korea is among the most exposed countries, which, according to the Korea International Trade Association, imported 64.7% of its helium from Qatar in 2025. The country relies heavily on helium imports to cool silicon wafers during fabrication and is understood to have no viable substitute.

I assume the helium is enclosed in a a chip's hermetically sealed package, if it were just for cooling wafers I don't understand why it can't reuse the helium?

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It's not enclosed in the final product. It is used during manufacturing. For example, you mechanically compress helium to get liquid helium, then when it depressurizes back to ambient pressure, it's -269 C, which is pretty close to "as cold as possible", and colder than any alternatives.

why can't this happen in a closed loop, using helium as the working fluid?

I assume purity matters. It probably picks up a lot of contaminants during use, and chip manufacturing is pretty sensitive to contaminants.

you can put He in a closed loop system and still use it for cooling, by using it as the thermodynamic working fluid, and then selecting any other fluid as the heat carrier?

That's not clear actually. It's been awhile since I watched the video on the ASML EUV system for etching wafers, but from my recollection, the UV light ablates away layers of wafers and so particles of silicon presumably contaminate the noble gas that's flowing over it. I don't think a closed loop is possible in the existing setups.

thats what I am questioning, wouldn't another gas be feasible?

I do know that some parts and components actually do have helium enclosed in the part package (can or so, not the shipping packaging!)

I'm getting mixed signals: its for the phase transition temperature, its for cleaning, ...

is EUV actually ablating layers of wafer? I thought the EUV was for patterning photoresist, you make it sound like ASML eliminated photoresist?

Here is the Veritasium video where they review ASML's EUV lithography in depth: 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

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