Golden Curve Method for OPC Signature Stability Control in high MEEF Applications

The super-sensitivity of wafer critical dimensions (CDs) to mask CDs at low k(1), known as the Mask Error Enhancement Factor (MEEF) drives the need for increasingly tighter mask CD control. In addition, the accuracy of the model based optical proximity correction (OPC) used to compensate systematic lithographic errors is partially dependent on a stable mask CD error signature that expands mask CD control requirements over multiple feature types. This paper presents the need for improved quantification and monitoring of mask CD signatures that includes CD characteristics relevant to OPC model calibration. It also introduces and discusses a new method to characterize, quantify, and control mask signatures in a mask manufacturing environment to limit the impact of mask CD variations on the OPC model validity. Multiple approaches to implementing this "golden curve" method are discussed in terms of their advantages and disadvantages.