Interaction between ILD-process and metal-etch induced gate charging effect

Interaction between ILD-process and metal-etch induced gate charging damage was investigated using via-intensive test structures and edge-intensive metal antenna structures. Strong interaction between the two effects was observed in multiple metal layer test structures. This interaction results in a marked turnaround behavior of the charging damage. This study also reveals that charging damage to gate oxide during via etch is dominated by the ILD deposition or etch process. This damage is independent of the number of vias but strongly depends on the relative position and the area of the metal holding the vias. The study also concludes that via-etch induced charging risk can be assessed by the metal area (to gate area) ratio rule DRC check at the layer of the metal holding the vias.