Improvements in post-OPC data constraints for enhanced process corrections
2006
Current state-of-the-art OPC (optical proximity correction) for 2-dimensional features consists of optimized
fragmentation followed by site simulation and subsequent iterations to adjust fragment locations and
minimize edge placement error (EPE). Internal and external constraints have historically been available in
production quality code to limit the movement of certain fragments, and this provides additional control for
OPC. Values for these constraints are left to engineering judgment, and can be based on lithography
process limitations, mask house process limitations, or mask house inspection limitations. Often times
mask house inspection limitations are used to define these constraints. However, these inspection
restrictions are generally more complex than the 2 degrees of freedom provided in existing standard OPC
software. Ideally, the most accurate and robust OPC software would match the movement constraints to
the defect inspection requirements, as this prevents over-constraining the OPC solution.
This work demonstrates significantly improved 2-D OPC correction results based on matching movement
constraints to inspection limitations. Improvements are demonstrated on a created array of 2D designs as
well as critical level chip designs used in 45nm technology. Enhancements to OPC efficacy are proven for
several types of features. Improvements in overall EPE (edge placement error) are demonstrated for
several different types of structures, including mushroom type landing pads, iso crosses, and H-bar
structures. Reductions in corner rounding are evident for several 2-dimensional structures, and are shown
with dense print image simulations. Dense arrays (SRAM) processed with the new constraints receive
better overall corrections and convergence. Furthermore, OPC and ORC (optical rules checking)
simulations on full chip test sites with the advanced constraints have resulted in tighter EPE distributions,
and overall improved printing to target.
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- Correction
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