Maskless EUV lithography, an alternative to e-beam

Background: The resolution capability of EUV lithography has reached parity with e-beam, raising the possibility that maskless EUV could supplant e-beam for mask writing and low-volume wafer patterning. Aim: We outline a maskless EUV scanner design with a 13.5-nm operating wavelength and numerical aperture of 0.55. Approach: A microlens array partitions radiation from a commercial laser-produced plasma EUV source into similar to 2 million individual beams, which are focused to separate, diffraction-limited focal points on a writing surface, and the surface is raster-scanned across the focal point array as the beams are individually modulated by MEMS microshutters integrated within the microlens array to construct a digitally synthesized raster exposure image. Results: Compared to state-of-the-art mask-projection EUV lithography, the system would have similar to 1000x lower throughput, but its power requirement would also be similar to 1000x lower, the exposure dose would be similar to 10x higher, scan velocity and acceleration would be similar to 1000x lower, and it would have the advantage of maskless operation. In comparison to e-beam mask writers, a maskless EUV scanner could provide higher resolution with at least double the throughput and over 10x higher dose. Conclusions: Maskless EUV lithography could provide significant cost and performance benefits for both direct-write applications and photomask production for mask-projection lithography. (C) 2019 Society of Photo-Optical Instrumentation Engineers (SPIE)