Abstract

Although the overall spatial resolution of backscattered electron (BSE) imaging suffers in comparison to secondary electron (SE) imaging, its superior sensitivity to atomic number (Z) contrast and ability to image through overlying insulation levels can provide a complementary approach for imaging subtle buried defects. BSE enables the localization and imaging of embedded defects through overlying insulator levels without the risk of compromising them with reactive ion etch (RIE) or plasma etch exposure or by anisotropic wet chemical delayering process steps. Once the embedded defect is localized with BSE in situ, subsequent imaging by cross sectional Transmission Electron Microscopy (XTEM) combined with elemental analysis by energy dispersive X-Ray analysis (EDX) or electron energy loss spectroscopy (EELs) can be performed without the risk of introducing artifacts. In this work, BSE imaging was successfully employed to image embedded subtle defects in 32nm node technologies through overlying insulator films not possible with conventional SE imaging techniques.

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