Investigation of spatial and energetic trap distributions in 1 nm EOT SiO2/HfO2 by discharging-sweep mode amplitude charge pumping

초록

In this study, the spatial and energetic distributions of electrons trapped within a SiO2/HfO2 dual layer gate stack (EOT = 1 nm) of fully processed high-k/metal gate nFETs were investigated by discharging-sweep mode amplitude charge pumping (DSACP). DSACP enables the separate energy profiling of the traps in the SiO2 and HfO2 layers of a SiO2/HfO2 gate stack. The electrical measurement of the spatial/energetic trap profiles with DSACP is based on the electron de-trapping mechanism, which allows scanning to be performed below the conduction band of Si in terms of both the depth and energy. The results show that shallower traps appear in the HfO2 layer with increasing discharging time and a significant correlation exists between the density of the shallow traps and positive bias temperature instability (PBTI) characteristics. (C) 2011 Elsevier Masson SAS. All rights reserved.

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