Low pass filtering of mask diffraction orders, in the projection tools used in microelectronics
industry, leads to a range of optical proximity effects, OPEs, impacting integrated circuit pattern
images. These predictable OPEs can be corrected with various, model-based optical proximity
correction methodologies, OPCs , the success of which strongly depends on the completeness of
the imaging models they use.
The image formation in scanners is driven by the illuminator settings and the projection lens
NA, and modified by the scanner engineering impacts due to: 1) the illuminator signature, i.e. the
distributions of illuminator field amplitude and phase, 2) the projection lens signatures
representing projection lens aberration residue and the flare, and 3) the reticle and the wafer scan
synchronization signatures. For 4x nm integrated circuits, these scanner impacts modify the
critical dimensions of the pattern images at the level comparable to the required image tolerances.
Therefore, to reach the required accuracy, the OPC models have to imbed the scanner illuminator,
projection lens, and synchronization signatures.
To study their effects on imaging, we set up imaging models without and with scanner
signatures, and we used them to predict OPEs and to conduct the OPC of a poly gate level of 4x
nm flash memory. This report presents analysis of the scanner signature impacts on OPEs and
OPCs of critical patterns in the flash memory gate levels.