EUV-lithography

The transition to "extreme" ultraviolet seems to be a logical development of photolithography. An increase in the number of transistors in microcircuits (an increase in the degree of integration) was constantly accompanied by a decrease in the wavelength. However, in the case of EUV, we can talk about a new kind of lithography. Transitions from 365 to 248 and further to 193 nm required new equipment and materials. For example, for each new wavelength, new lenses had to be created from new special types of glass. However, the principle of building a stepper - an exposure system - remained the same. Radiation with a wavelength of 15-13nm (EUV) interacts with matter differently than radiation of 400-200nm. EUV is strongly absorbed in all glasses. An optical system for such radiation can only be built using special multilayer mirrors. 

Production of such mirrors is a separate oh-oh-very difficult task. By the way, masks for EUV lithography are also made as multilayer mirrors. Their manufacture is much more complicated and expensive than lenses and masks for photolithography. Technical difficulties also arise due to the fact that the optical system in EUV cannot be radially symmetrical. Because of this, additional distortion occurs in the mask image.

 The high photon energy of EUV radiation in pair with small sizes of exposed elements creates additional difficulties (generation of secondary electrons, non-uniformity of the absorbed dose in the resist ...) 

In addition, it is oh-so-very difficult to build a sufficiently powerful and stable source of EUV radiation.

In January 2023, ASML published the following - Our ASML Research in San Diego has set two new EUV power world records – a one-hour run of 600W EUV power meeting EXE:5200 dose stability specifications, and a demonstration of 700W open-loop EUV power.  Five years ago, ASML’s first 250W source delivered the power to enable EUV high volume manufacturing. This latest achievement shows how far our technology has come and our role in innovation.

All this makes EUV lithography significantly more complex and expensive than "conventional" photolithography. However, only EUV makes it possible to reduce the size of printed elements to record 5nm, 3nm, 2nm.

The first talk about EUV lithography dates back to the mid-1980s. The first prototype of an industrial EUV stepper was introduced by ASML in 2010. ASML Celebrates Sale of 100th Industrial EUV System / Stepper Early 2020. https://www.asml.com/en/company/about-asml/history

More than 20 years of development (before the prototype) and another 10 years before entering industrial production.  It's a lifetime! 

BTW: at the beginning of 2023, the cost of one EUV system is about $150 million.