Uncertainty of the linewidth of a nanoobject at control it in a low-voltage SEM

Abstract

The relief structure (RS) with vertical sidewalls (SW) is promising as the linewidth measure for low-voltage (LV)SEM due to similarity of its profile to the one of the SCCDRM linewidth standards. So it can be used as the terminal link in the metrological traceability chain beginning from this standard. But there is an obstacle for its calibration: RS image are changing over time during continuous scanning the measure by electron beam that is natural for measure usage. Changes arise from the variation of the emission of slow secondary electrons (SSE) forming the image of the RS surface. This emission variation appears in turn due to the change of induced charge on the RS surface. Changes of the charge disposed near RS edges have critical influence on RS linewidth that leads to its value uncertainty. It is revealed that the degree of the influence depends on the layout of emitting site on RS sidewall (SW). Emission variations from its lower sites have a less induction on the RS image. So if one uses a regime of SSE extraction from these lower SW sites then the linewidth uncertainty is bound to decrease. Internal parts of the vertical SW are preferred not only due to its higher degree of its surface smoothness compared to its upper parts but also due to its SSE emission stability during scanning.