As the semiconductor industry proceeds to develop ever better sources of extreme ultraviolet (EUV) light for photolithography applications, two distinct technologies have come to prominence: Tin-plasma and free electron laser (FEL) sources. Tin plasma sources have been in development within the industry for many years, and have been widely reported. Meanwhile, FELs represent the most promising alternative to create high power EUV frequencies and, while tin-plasma source development has been ongoing, such lasers have been continuously developed by academic institutions for use in fundamental research programmes in conjunction with universities and national scientific institutions. This paper follows developments in the field of academic FELs, and presents information regarding novel technologies, specifically in the area of RF design strategy, that may be incorporated into future industrial FEL systems for EUV lithography in order to minimize the necessary investment and operational costs. It goes on to try to assess the cost-benefit of an alternate RF design strategy, based upon previous studies.
A Free Electron Laser (FEL) is a highly coherent, highly collimated light source capable of creating extremely high
power beams of precisely controlled wavelengths. The semiconductor industry is currently examining these as sources
extreme ultraviolet (EUV) light for photolithography applications. An important factor to achieve high quality FEL
emission is the careful development of the amplifying RF system as a complete integrated unit, considering each
component as part of the amplification chain to maximise RF stability and FEL beam quality. In this paper we review
methods to optimise RF amplifier systems without compromising on output stability, compare solid-state with tube based
technologies, and discuss the state-of-the-art in RF amplifier technology, highlighting recent case studies. We conclude
by examining the benefits of integrated systems and highlight the solutions offered by available technologies to a range
of technological challenges, in order to design and build the best possible systems with maximum possible efficiency for
the demanding requirements of the semiconductor industry.