Source development for extreme ultraviolet lithography and water window imaging

Sources based on laser produced plasmas of tin (Sn) are currently being developed for extreme ultraviolet lithography for semiconductor fabrication. Since they operate at short wavelength (13.5 nm) they are capable of producing features with critical dimensions in the 10 nm range. Already next generation lithography sources operating at an even lower wavelength of around 6.7-6.8 nm have been proposed and research is ongoing on their feasibility for both large scale manufacturing and ‘at wavelength’ metrology. The high resolution afforded by such short wavelengths is also of use for applications such as surface patterning and microscopy and the results of recent experiments to identify sources for operation in the ‘water window’ (2.34-4.2 nm), where carbon absorbs strongly but water does not are summarized.