What is EUV?

Fundamentals

The term EUV is coming up more and more as semiconductor shortages loom, but what does it mean exactly, and why is it crucial? If you use a relatively new smartphone or smartwatch, or one of the latest generations of gaming consoles, you are benefitting from EUV lithography technology.

In the semiconductor industry, EUV refers to extreme ultraviolet lithography, a soft X-ray technology with a wavelength of 13.5nm. This means it enables very fine resolutions when fabricating electronics via photolithography, one of the most important steps in semiconductor manufacturing, and as such, is expected to create the potential for radical progress in the industry. The most cutting-edge microchips contain billions of transistors; with each new generation of chip, manufacturers pack in more and more to create chips that are faster, more powerful, and more energy efficient.

Photolithography is a patterning process in which a silicon wafer coated with a photosensitive polymer photoresist is selectively exposed to light through a photomask. The exposed pathways on the polymer surface can then be dissolved, providing patterned access to an underlying substrate. These patterns are later used for the formation of the ultrafine, microscopic structures that make up a semiconductor chip.

ASML fine chip
Semiconductor chips are comprised of billions of ultra-fine structures. A tighter packing of these structures is made possible with the precision EUV systems provide. (ASML )

Since light is unable to directly define features smaller than its own wavelength, the short wavelength of EUV light sources allows for finer and denser patterns than any previous method. The 13.5nm wavelength, in particular, is less than one-tenth of what ArF (Argon Fluoride) excimer laser scanners provide. To generate extreme ultraviolet light during the lithography process, a CO2 laser fires two distinct laser pulses at a fast-moving drop of tin, vaporizing the tin. The tin vapor becomes plasma, which in turn emits EUV light—and this all happens 50,000 times per second.

EUV is a departure from deep ultraviolet lithography methods; since all matter absorbs EUV radiation, EUV lithography requires a vacuum. Current systems utilize at least two condenser multilayer mirrors and six projection multilayer mirrors—which manufacturer ASML claims are the flattest surface in the world—that guide the light to the wafer. But these mirrors absorb 96% of the light emissions, meaning an ideal source needs to be much brighter than those used in preceding systems.

mirrors and bouncing light
Optimizing the light source in EUV lithography requires a complex scheme of mirrors, which must bounce the light accurately. (ASML)

The current semiconductor shortage can be understood as a result of challenges presented by the COVID-19 pandemic but also as a result of longstanding challenges within the industry, such as insufficient capacity at semiconductor fabs.

Implementing EUV scanners has made scaling more affordable and allowed chipmakers to continue the pursuit of Moore’s law, an observation that the number of transistors in an integrated circuit double about every two years. Yet EUV systems are only made by one company: Advanced Semiconductor Materials Lithography (ASML).

Demand for ASML’s technology has soared, resulting in backorders and skyrocketing the company’s stock price by more than 340% since the end of 2018. In fact, ASML is valued higher than some of its top customers, including Intel. Producing their machines presents a unique challenge, however, as modules needed to make it are held up by chip shortages. The machines that make the chips also need them.

Ultimately, EUV system availability looks like it will gate the ability of chip manufacturers like Intel, Samsung, and Taiwan Semiconductor Manufacturing Company (TSMC) to implement all of their planned production fabs. This looping supply and demand affects decisions by ASML’s customers on how to design their fabrication portfolios in the coming years and, ultimately, how quickly fabrication capacity might catch up to demand.