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FEATURE EUV LITHOGRAPHY Mirror on semicon


EUV collector mirror for high-power laser-produced plasma sources


To bring EUV lithography into mainstream semiconductor production will require more powerful sources, but there is also a lot of development work underway on the optics for the systems, as Katia Moskvitch discovers


T


o maintain Gordon Moore’s law – the assumption that the number of transistors that can be packed onto


an integrated circuit will double every two years – lithography has to undergo a paradigm shift, away from optical laser light to dramatically shorter wavelengths in the extreme ultraviolet (EUV) portion of the


spectrum. EUV lithography could reduce the amount of multiple patterning steps needed in today’s microprocessors, which would reduce both the cost and complexity of laying the circuit on the chip. However, while EUVL has been around since the early 1990s, it is still the realm of lab research. Introducing it in full-scale production has been


14 ELECTRO OPTICS l FEBRUARY 2014


painfully slow – at the moment, only six of ASML’s first production level machine, NXE:3300, have been sold. One of the companies supporting the development of EUV lithography is silicon chip giant Intel. ‘If EUV can scale to high volume, it has the potential of improving manufacture productivity and thereby lower costs and improve functionality,’ said Intel


spokesman Chuck Mulloy. One of the main hurdles to deploying EUV lithography on an industrial scale is the source power, which at the moment isn’t high enough. The optical design of EUV systems is also markedly different to traditional lithography machines. EUV optical systems consist of mirrors and not lenses as in conventional lithography optics, because 13.5nm radiation is absorbed by all known lens materials – even air. So EUVL operates in a vacuum and requires a whole new overall concept of lithography optics, according to Zeiss, a renowned German company that fabricates EUVL optics.


@electrooptics | www.electrooptics.com


Fraunhofer IOF


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