The optimization of overlay control for beyond sub-40nm lithography processes

The overlay performance in lithography process depends on both the machine control abilities and overlay residue control in processes. One of important optimization directions of lithography processes in advanced node is to decrease overlay residue in the lithography processes and the overlay margin must meet the stability requirement. In this paper, the investigation on the effect of alignment accuracy, reticle elasticity, and high order nonlinear components on the overlay accuracy are presented. Furthermore, the optimization of overlay performance based on the above factors is implemented to realize the high accuracy of overlay and ensure the process stabilities, paving the way for sub-40nm and beyond production requirement.