Simulating SEM imaging of via bottoms

Scanning electron microscope (SEM) imaging is widely used in semiconductor manufacturing, including for defect inspection. One use is to identify contact holes that are potentially scummed (not completely cleared to the substrate). However, the visibility of the bottom of a contact hole (and thus the ability to identify scumming) is limited when the aspect ratio of the hole becomes high. In this work, a large designed experiment simulation study using AMAG SimuSEM will thoroughly explore the parametric influences of profile and CD for via bottom detection in the secondary electron regime, including not only aspect ratio, but also influences of sidewall angle and footing, along with defect cases of incomplete etch or resist residues in hole bottoms. We will show the expected trends to the signal evolution as a function of the applied perturbations, and demonstrate that simulation can be used to understand and estimate the thresholds for detecting via footing and scumming.