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IC manufacturing at 65 nm node requires careful selection of imaging technology. To select appropriate
approach, a wide range of impacts has to be considered. In particular, imaging, mask, and resist
technologies all contribute to final CD control of the features patterned and their imaging latitude during IC
manufacture.
To select imaging strategy, we conducted simulation analysis of dry ArF, dry F2, and immersion ArF
imaging technologies. During the selection process, each technology has to be evaluated at its imaging
optimum defined in terms of projection lens NA and illuminator design as well as the mask design details;
such analysis has to be specific to the requirements of the IC design critical levels.
One of the key technology characteristics is the imaging tool impact on patterned level. This impact can be
quantified by the projection lens aberration residue and its flare, both dependent on the image location.
Introduction of aberration and flare signatures into the imaging analysis enables definition of tool
performance metric common to the entire image field, and it spotlights across-field imaging tradeoffs.
In addition to these factors (i.e. the imaging technology- and the tool-related impact), the impact of wafer
stack on image formation in resist has to be considered. In particular, Fresnel losses, resist photochemistry,
and optical path differences of diffraction orders in dense medium have to be accounted for. Such approach
leads to estimates of resist refraction and contrast on the formation of critical features.
This review presents comprehensive analysis of all key factors driving imaging latitude of critical levels at
65 nm node. These factors were representing impacts of imaging strategy, mask and resist technologies.
The analysis presented below spotlights imaging tradeoffs of dry ArF, dry F2, and immersion ArF imaging
technologies.
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