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Fast freeform source and mask co-optimization method

  • US 9,111,062 B2
  • Filed: 11/08/2013
  • Issued: 08/18/2015
  • Est. Priority Date: 11/21/2008
  • Status: Active Grant
First Claim
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1. A computer-implemented method for optimizing a lithographic process in a simulation domain, the simulated lithographic process having data representing an illumination source and a mask, the method comprising:

  • performing, by the computer, a free-form optimization process;

    placing, by the computer, sub-resolution assist feature (SRAF) seeds in a description of the mask based on a result of the free-form optimization process; and

    performing, by the computer, a constrained optimization process, including growing the SRAF seeds while taking into account manufacturability constraints for both the illumination source and the mask.

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