Development of mix-and-match overlay for multiple metrology platforms utilization by using the cross-layer overlay simulation method

With stricter overlay requirements in advanced technology nodes, new overlay metrology solutions have been introduced, offering enhanced precision, accuracy, and measurement speed. To improve overlay performance, different metrology tools may sometimes be utilized on the same layer. This strategy, however, can degrade the stability of both statistical process control (SPC) and advanced process control (APC) compared to overlay control with a single metrology platform. In our study, we evaluated the overlay impact when using two metrology platforms within a single run-to-run control loop, i.e., mix-and-match overlay (MMO) metrology. We will highlight the key factors for successful MMO implementation in high-volume manufacturing (HVM). We evaluated two critical factors that could influence the performance of mix-and-match overlay metrology control. Firstly, we studied controlling high-order correction per exposure (HO-CPE) and metrology target design (MTD) on after etch Inspection (AEI) overlay (OVL) stability. Secondly, we simulated the run-to-run overlay performance of the target layer when using multiple metrology platforms and confirmed the lithography’s key performance indicators (KPIs), such as the stability of process correction and the out-of-control rate using statistical process control (SPC). Finally, we simulated the overlay impact on the subsequent layer using the cross-layer overlay simulation method, based on the process correction changes in the target layer resulting from mix-and-match overlay metrology control.