TARGET AND ALGORITHM TO MEASURE OVERLAY BY MODELING BACK SCATTERING ELECTRONS ON OVERLAPPING STRUCTURES

摘要

An overlay target includes a grating-over-grating structure with a bottom grating structure disposed on a specimen and a top grating structure disposed on the bottom grating structure. The overlay target further includes a calibration scan location including the bottom grating structure but not the top grating structure and an overlay scan location including the top grating structure and the bottom grating structure.