The current lithography machines use 193 nm light, and for the past 10 years we've been waiting for extreme ultraviolet machines, that emit 13.5nm light.
It's pretty obvious that the this challange is far greater than anticipated — ASML was talking about shipping it in 2010 (!).
So why take such a huge leap? We're talking order-of-magnitude jump in wavelength. Why not go to 100nm light first? Or 50nm? Wouldn't it be easier to develop this EUV technology more iteratively and gradually improve and fix all the problems (light source, power, availability, pellicles, mirrors, etc.) one by one as they arise when stepping between wavelengths?
Best Answer
As the feature size decreases, the wavelength of the source and lithography system must also decrease. The problem is after 193nm materials and air are significant absorbers of UV which happens around 157nm. In addition, excimer lasers no longer work well as a source after 157nm.
So if a new lithography tech requires vacuum, mirrors and a new source, you might as well do it right and jump down to 13.5nm. This step has taken 15 or so years and required entire industries to be developed to achieve 13.5nm lithography, including two EUV steps would be very costly due to the costs of developing an EUV source alone.
Source, Slide-5 OR Extreme UV lithography - Electrical and Computer Engineering waterloo
Some other interesting notes are lenses are too absorbent at EUV wavelengths so mirrors must be used, and 13.5nm sources will need about 1MW to get 200W of EUV light.