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Low pass filtering taking place in the projection tools used by IC industry leads to a range of
optical proximity effects resulting in undesired IC characteristics. To correct these predicable
OPEs, EDA industry developed various, model-based correction methodologies. Of course, the
success of this mission is strongly dependent on how complete the imaging models are. To
represent the image formation and to capture the OPEs, the EDA community adopted various
models based on simplified representations of the projection tools. Resulting optical proximity
correction models are capable of correcting OPEs driven by the fundamental imaging conditions
such as wavelength, illuminator layout, reticle technology, and lens numerical aperture, to name
a few.
It is well known in the photolithography community that OPEs are dependent on the scanner
characteristics. Therefore, to reach the level of accuracy required by the leading edge IC designs,
photolithography simulation has to include systematic scanner fingerprint data. These tool
fingerprints capture excursions of the imaging tools from the ideal imaging setup conditions.
They quantify the performance of key projection tool components such as illuminator and lens
signatures. To address the imaging accuracy requirements, the scanner engineering and the EDA
communities developed OPC models capable of correcting for imaging tools engineering
attributes captured by the imaging tools fingerprints.
Deployment of immersion imaging systems has presented the photolithography community
with new opportunities and challenges. These advanced scanners, designed to image in deep
sub-wavelength regime, incorporate features invoking the optical phenomena previously
unexplored in commercial scanners. Most notably, the state of the art scanners incorporate
illuminators with high degree of polarization control and projection lenses with hyper-NAs. The
image formation in these advanced projectors exploits a wide range of vectorial interactions
originating at the illuminator, on the pattern mask, in the projection lens and at the wafer. The
presence of these, previously subdued phenomena requires that the imaging simulation
methodologies be refined, increasing the complexity of the OPE models and optical proximity
correction methodologies.
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