Novel overlay correction using inline alignment station(iAS) for scanner

Demand for on-product overlay (OPO) improvement is becoming increasingly crucial in semiconductor manufacturing. Alignment sampling plan is closely linked to OPO. However, alignment sampling plan is constrained by productivity. Inline Alignment Station (iAS) is the groundbreaking system which enable dense alignment without throughput impact. Remaining linear and high order grid of OPO can be corrected with iAS correction. iAS is a measurement tool placed inline with NSR and has its own measurement stage. Therefore, it is possible to measure dense sampling without throughput impact. However, matching two stages generally pose some difficulties. Chucking deformation of wafer is one of the challenging factors. We have overcome the problem by integrating new methods. In this paper, we introduce the detail of the method and show some actual results.