A Novel Feedforward and Feedback Method for Overlay Control

Overlay (OVL) is one of the most critical process control parameters required to enable successful semiconductor manufacturing and the specifications for on-product overlay (OPO) have become much tighter in today's advanced technology nodes. To ensure overlay performance meets the required product specifications, a combination of feedforward and feedback run-to-run approaches have been adopted to minimize Iot-to-Iot variations to better control OPO. In this work, we utilize traditional feedforward correction techniques used to compensate for non-alignment overlay, but also incorporate and leverage other fingerprints which can also impact overlay. Our new method selects the feedforward layer based on multiple metrology and process indicators and demonstrates significant improvement compared to the current solution.