Integrated method of mask data checking and inspection data prep for manufacturable mask inspection: inspection rule violations

Many mask patterns contain small un-inspectable features (Inspection Rule Violations or IRVs) that create significant through-put time (TPT) impact at mask inspection due to excessive false defects. These small features include a) drawn test designs purposely intended to be small for evaluating process capabilities, and b) un-intended small features that result from errors such as overlap of designs, gaps between cells or synthesis errors. Typically, an IRV is a feature smaller than the minimum feature size capability of the mask inspection tool. This paper describes an integrated method to find such IRVs in the data and either fix them or declare that area as not inspectable. The method includes documented drawn size limits for inspectability, data checks at drawn level, data checks at post-fracture, and functions to define "Do Not Inspect Regions (DNIRs)" for any remaining IRVs in the data. Data checking at post-fracture must comprehend Optical Proximity Correction (OPC), which generates small features that are not IRV's. The defined DNIRs are listed in the jobdeck for automated inspection data preparation with no engineering intervention. The result is improved mask inspection TPT as well as early detection and correction of certain design or synthesis errors.