18 April 2013 Capturing buried defects in metal interconnections with electron beam inspection system
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In this paper we present a novel mode of electron beam inspection (EBI), entitled super wide optics (SWO) mode, which can effectively detect buried defects in tungsten (W) plugs and copper (Cu) wires. These defects are defects of interest (DOI) to integrated circuit (IC) manufacturers because they are not detectable in optical inspection, voltage contrast (VC) mode EBI or physical mode EBI. We used engineering systems to study two samples, a tungsten chemical mechanical polish (CMP) wafer and a copper CMP wafer with a silicon carbon nitride (SiCN) cap layer. EBI with our novel SWO mode was found to capture many dark defects on these two wafers. Furthermore, defect review with all three EBI modes found some of these dark defects were unique to SWO mode. For verification, physical failure analysis was performed on some SWO-unique DOI. The cross-sectional scanning electron microscope (SEM) images and transmission electron microscope (TEM) images confirmed that the unique DOI were buried voids in W-plugs and copper wire thinning caused by either buried particles or buried particle induced metal trench under-etch. These DOI can significantly increase the resistance of metal interconnects of IC chip and affect the chip yield. This new EBI mode can provide an in-line monitoring solution for these DOI, which does not exist before this study.
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Hong Xiao, Hong Xiao, Ximan Jiang, Ximan Jiang, David Trease, David Trease, Mike Van Riet, Mike Van Riet, Shishir Ramprasad, Shishir Ramprasad, Anadi Bhatia, Anadi Bhatia, Pierre Lefebvre, Pierre Lefebvre, David Bastard, David Bastard, Olivier Moreau, Olivier Moreau, Chris Maher, Chris Maher, Paul MacDonald, Paul MacDonald, Cecelia Campochiaro, Cecelia Campochiaro, "Capturing buried defects in metal interconnections with electron beam inspection system", Proc. SPIE 8681, Metrology, Inspection, and Process Control for Microlithography XXVII, 86810F (18 April 2013); doi: 10.1117/12.2011162; https://doi.org/10.1117/12.2011162

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