Improved Duplicate Photomask Matching using AIMS™ Metrology for 14nm and smaller

Abstract

In this paper, we demonstrate the use of Aerial Imaging Metrology System (AIMS™) during mask fabrication to deliver duplicate photomasks with matching iso-dense bias (IDB) to a reference photomask. The photomask IDB trend based on AIMS™ feedback showed a direct correlation to on-wafer IDB performance. We also show that the AIMS™ threshold energy is correlated to the photomask critical dimension (CD) mean to target (MTT), and correlates to the on-wafer exposure dose for both line/space and via mask levels in the 14nm technology node. This technique will enable improved photomask matching taking into account 2D and 3D mask effects comparable to wafer processing on lithography exposure tools. With AIMS™ metrology, corrections can then be applied to photomask rebuilds prior to shipment to Wafer Manufacturing Sites.