Advanced method for run-to-run control of photolithography overlay registration in high-mix semiconductor production

摘要

The application of overlay run-to-run control in high-mix production fabs (such as development fabs, ASIC fabs or foundries) encounters some unique problems. A new observer algorithm called JADE™ (Just-in-Time Adaptive Disturbance Estimation) was developed to solve the high-mix run-to-run control problem. JADE uses recursive weighted least-squares parameter estimation to identify the contributions to variation that are dependent upon tool, product, reference tool, and reference reticle. With the JADE Observer algorithm, run-to-run controllers use all available feedback data independent of the length of time since a particular product was processed. The application of JADE, compared to traditional control techniques, will be demonstrated on high and low-mix fab lithography overlay data. This comparison illustrates the degradation of the typical streamline observer formulation under high-mix operation, with an actual worsening of overlay control relative to open-loop (no run-to-run control) operation. In contrast, the JADE algorithm control performance, while matching the typical streamline formulation at low-mix operation, will be shown to be unaffected under very high-mix photolithography operation.