AFM-in-SEM for Precise Endpoint Delayering of SRAMs

Abstract Milling experiments were undertaken with an AFM-in-SEM system to examine various layers in the SRAMs of a 3 nm finFET node technology chip. The simultaneous Conductive AFM and tomographic milling operation provided feedback as to the exact state of delayering in the sample. Despite the relatively rough appearance of some areas of the chip, the milling by the AFM tip was able to create local areas with high planarity. The AFM measurement provided the exact moment certain structures were polished through. Discussion of various electrical modes in the analysis that might provide clearer indications of breakthrough is also undertaken in this paper.