The radial distribution of defects in a percolation path
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(a) HAADF image showing the gate stack of a typical -type MOS transistor after BD. A DBIE nanomarker is identified. EEL spectra at positions 1–6 (indicated in the oxide layer) were acquired at the breakdown spot, respectively. The TEM sample was prepared using FIB with low energy clean and in situ lift-out. The STEM/EELS experiments were performed on a FEI TITAN microscope operated at . (b) The Si edge spectra collected at positions 1–3. The different Si oxidation states are labeled. The inserted graph shows the zoomed-in plot from , which is the onset portion of signals. The intersections of the fitted onset slopes shift towards lower energy which indicate that the local oxide conduction band minimum are lowered for as moving from position 1 to 3.
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(a) The as-measured O edge intensities at all the 6 positions near the breakdown spot. The diameter of the percolation path (defective oxide area laterally) is estimated to be around . (b) Top view schematic diagram of the oxide area with a breakdown in the TEM sample. A three-shell percolation model is proposed for the thickness correction. The O edge intensities at position 3, 5, and 6 are used for the calculation. The different dimensions in the percolation path are labeled as and the TEM sample thickness is . (c) The corrected oxygen deficiency in the percolation path. The O deficiency in the center of the percolation path is as high as 65% .
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