Novel, At-Design-Rule, Via-To-Metal Overlay Metrology For 193nm Lithography

The effect of scanner aberrations on the pattern placement errors (PPE) in the copper interconnect lithography process is studied both in simulations and experimentally. New grating-based AIM overlay mark enables measuring device feature overlay. It is shown that AIM mark exhibits superior performance over conventional box-in-box (BiB) marks. Comparison between Archer AIM optical and direct CD SEM device overlay measurements was done. Both CD SEM and AIM optical measurements show sensitivity to PPE. Good matching between AIM and device overlays was demonstrated.