1. A method of generating a photo mask layout, the method comprising: providing, by a processor, a first photo mask layout including main patterns and sub-resolution assist features (SRAF) patterns, wherein the SRAF patterns are configured to enhance a resolution of the main patterns on a wafer; dividing, by a processor, the first photo mask layout into regions of at least two rows and columns to generate a plurality of mesh cells; generating, by a processor, a rule based table having at least one entry including coordinate information for identifying at least one of the mesh cells and correction information for correcting defects in the SRAF patterns for the corresponding mesh cells; and correcting, by a processor, SRAF patterns by applying a value of the correction information of a corresponding one of the entries to the SRAF patterns located within the mesh cells identified by the coordinate information of the one entry.