New approach for mapping and monitoring Damascene Trench depth using CD-SEM tilt imaging

摘要

As Interconnect delays increasingly become the performance limiting factor for advanced integrated circuits, the transformation of the interconnect technology from Al to Cu and the migration from metal etch to damascene process, is inevitable. The Dual Damascene process brings with it new challenges. The Damascene trench etch is frequently done without an etch stop to simplify the process sequence and to eliminate the effective K increase caused by etch stop material. In this case, the trench depth is controlled by etch rate and etch time. Since the depth of the trench has a linear correlation with the interconnect resistance, and the trench depth needs to be carefully controlled and monitored. In this work we showed that we can monitor the damascene etch process in a non-destructive and quick method by measuring the trench depth using the unique tilt imaging capability of the AMAT VeraSEM 3D We show how we can easily map the heights across the wafer in a simple, quick and automatic Operator Free method, and compare the VeraSEM 3D accuracy to AFM.