Model-based pupil-fill optimization for the SEMATECH Berkeley EUV microfield exposure tool

Extreme ultraviolet (EUV) resist development has been enabled over the past few years in large part by high numerical aperture (NA) exposure tools such as the 0.3-NA microfield exposure tools (METs) at SEMATECH and Intel. Of these tools, the SPMATECH Berkeley MET tool is unique in its ability to provide lossless pupil fill control enabling extremely low k(1) printing (down to 0.25). It is well known that illumination settings can be tailored to optimize printing performance for particular features. The optimal illumination settings, however, depend not only on the feature type but also on the specifics of the pupil function, including phase (or aberrations) and amplitude (or pupil obscurations). Here, aerial image modeling is used to study the optimal illumination conditions for the SEMATECH Berkeley MET tool as a function of feature size and type. The modeling accounts for the known pupil function (amplitude and phase) of the optic.