There are many devices which require multi-level or grayscale structures. Examples include PBG (photonic band gap) crystals, DOE's (diffractive optical elements), blazed gratings, MEMS/NEMS (micro/nano-electro-mechanical systems), etc. The grayscale E-beam lithography which eliminates the shortcomings of the binary E-beam lithography may be employed for fabrication of such structures. When the feature size is reduced down to the nanometer scale, proximity effect can make the fabricated structure much different from the designed one in terms of its dimensions (shape and size of features). The PYRAMID approach has been adopted in developing an effective spatial dose control scheme for minimizing the dimensional error in the fabricated multi-level (grayscale) structures.
Ideal Structure Uncorrected Corrected
Staircase Structure Sawtooth Structure