FAST FREEFORM SOURCE AND MASK CO-OPTIMIZATION METHOD

摘要

The present disclosure relates to lithographic apparatuses and processes, and more particularly to tools for optimizing illumination sources and masks for use in lithographic apparatuses and processes. According to certain aspects, the present disclosure significantly speeds up the convergence of the optimization by allowing direct computation of gradient of the cost function. According to other aspects, the present disclosure allows for simultaneous optimization of both source and mask, thereby significantly speeding the overall convergence. According to still further aspects, the present disclosure allows for free-form optimization, without the constraints required by conventional optimization techniques.

主权项

1. A computer-implemented method for optimizing a lithographic process having an illumination source and a mask, the method comprising:
a free-form optimization process; placing sub-resolution assist feature (SRAF) seeds in a description of the mask based on a result of the free-form optimization process; and a constrained optimization process, including growing the SRAF seeds while taking into account manufacturability constraints for both the illumination source and the mask, wherein one or more steps are performed by the computer.