Extreme ultraviolet lithography

Current microlithography used in high-volume integrated circuit manufacturing employs some form of optical projection technology. The most advanced tools use deep-ultraviolet (DUV) radiation having a wavelength of 248 nm and are used to print 250-nm features. These tools will likely be extended for use at the 180-nm generation and perhaps below. New DUV tools using 193-nm radiation are actively under development and are expected to be used for 130-nm generation and perhaps even 100-nm generation. Extending these DUV optical projection tools for manufacturing in the 100-200-nm region will be paced by the development of new high numerical aperture imaging systems and highly complex phase shift masks. For future generations of integrated circuits with minimum feature sizes below 100 nm, 193-nm tools will have great difficulty meeting all manufacturing requirements. This paper describes an alternate optical approach, for sub-100-nm generations, based on extreme ultraviolet radiation at around 13 nm, called extreme ultraviolet lithography (EUVL). This approach uses a laser-produced plasma source of radiation, a reflective mask, and a 4× reduction all-reflective imaging system. The technology is currently in the engineering development phase for an alpha machine. This paper reviews its current status and describes the basic modules or building blocks of a generic EUVL exposure tool