What are the ways in which semiconductor-grade neon is critical for manufacturing?

Question

This is a question about material use specifically in semiconductor manufacturing.

CNN's Ukraine halts half of world's neon output for chips, clouding outlook begins:

Ukraine's two leading suppliers of neon, which produce about half the world's supply of the key ingredient for making chips, have halted their operations as Moscow has sharpened its attack on the country, threatening to raise prices and aggravate the semiconductor shortage.

Some 45%-54% of the world's semiconductor grade neon, critical for the lasers used to make chips, comes from two Ukrainian companies, Ingas and Cryoin, according to Reuters calculations based on figures from the companies and market research firm Techcet. Global neon consumption for chip production reached about 540 metric tons last year, Techcet estimates.

and later says:

Before the invasion, Ingas produced 15,000 to 20,000 cubic meters of neon per month for customers in Taiwan, Korea, China, the United States and Germany, with about 75% going to the chip industry, Nikolay Avdzhy, the company's chief commercial officer, said in an email to Reuters.

The CNN article mentions lasers, and it certainly can't be HeNe lasers (e.g. as used in interferometric nano-positioning stages) because they are sealed and long-lived and no where near consumable on this scale.

Is neon perhaps used in large volumes in KrF or ArF excimer lasers for DUV lithography? Or perhaps is it really used in reactive ion etching instead and they've got it wrong? Helium is often used in etch gas chemistries as both a buffer and a way to limit and control the plasma temperature, but I'd never heard of neon being used.

Question: What are the ways in which semiconductor-grade neon is critical for manufacturing?

Answer 1

Neon is used the buffer gas in most excimer lasers. Both KrF and ArF excimer lasers contain roughly 98-99% neon, with the balance being the actual krypton or argon (and of course fluorine).

Due to its nature as a carrier gas, it doesn't just need to be any old neon gas, it must be extremely pure 'semiconductor grade' neon, which very few companies are able to produce. The purification process is long and complicated and there is not a lot of demand from other industries. There is a small demand from the medical industry, but it is minor compared to the semiconductor industry.

It is worth emphasizing that Ukraine didn't produce 50% of the global neon supply, but rather 50% of the global semiconductor grade neon. As stated earlier, purifying neon to this grade is not easy and and the few companies that can do it will require the better part of a year to increase their production capacity to pick up the slack.

It is also worth noting that the gas in excimer lasers is a consumable. In fact, something called 'gas lifetime' is one of the primary performance metrics for an excimer laser. Commercial ArF excimer lasers typically achieve only 1,000,000 shots before requiring that the gas be purged completely and refilled with a fresh mix of mostly neon with a little bit of argon and fluorine of course.

The gas is not actually consumed, but each shot dislodges a small amount of impurities from various sources like the electrodes, and these impurities are quite opaque to 193nm light. Eventually, the concentration of impurities grows too high and the laser will require too high of a voltage to achieve the needed dose to the wafer, and at that point, the gas is simply purged and replaced. Purifying the used gas would be the same challenge and difficulty as purifying the raw neon in the first place, so little is solved by reusing the gas. In fact, it might even be recycled, but the purifying process would be made no easier or cheaper for it.