As the feature size of the semiconductor device is becoming increasingly smaller and the transistor has become 3D (e.g. Fin-FET structure), a simple line edge roughness (LER) measurement is no longer sufficient for characterizing these devices. Sidewall roughness (SWR) is now the more proper metric for these metrology applications. However, current metrology technologies, such as SEM and OCD, provide limited information on the sidewall of such small structures. The subject of this study is the SWR measurement with 3D atomic force microscopy (AFM) using a tilted Z scanner. This is based on a decoupled XY and Z scanning configuration, in which the Z scanner can be intentionally tilted to the side. A sharp conical tip is typically used for imaging, which provides high-resolution capability on both the flat surfaces (top and bottom) and the steep sidewalls.

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