Extreme ultraviolet lithography

Extreme ultraviolet lithography (also known as EUV or EUVL) is a next-generation lithography technology using an extreme ultraviolet (EUV) wavelength, currently expected to be 13.5 nm. EUV is currently being developed for possible future use in combination with immersion lithography at 32 nm pitch resolution, sometimes referred to as the 7 nm node. The primary EUV tool maker, ASML, projects EUV at 5 nm node to require a higher numerical aperture than currently available and multiple patterning to a greater degree than immersion lithography at 20 nm node. Immersion lithography is still more than 4 times faster than EUV (275 WPH vs. 65 WPH as detailed below), due to source power limitations; hence, multiple patterning with immersion lithography has already been used where EUV had previously been expected to be used.

While source power is the chief concern due to its impact on productivity, significant changes in EUV mask infrastructure, including blanks, pellicles and inspection, are also under study. Particle contamination would be prohibitive if pellicles were not stable above 200 W, i.e., the targeted power for manufacturing. Without pellicles, particle adders would reduce yield, which has not been an issue for conventional optical lithography with 193 nm light and pellicles. The current lack of any suitable pellicle material, aggravated by the use of hydrogen plasma cleaning in the EUV scanner, is preventing the adoption of EUV lithography for volume production.