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Comparison of nitrogen depth profile (N profile) and gate tunneling current for two kinds of SiON films with similar thicknesses and nitrogen concentrations. The N profile was measured using high resolution angle-resolved XPS. Sample A (open triangle) has a steeper N profile than that of sample B (open circle). Gate tunneling-current density was measured at , with other terminals being connected to ground potentials.
(a) Schematic showing for two kinds of N profiles: the steep vs the smooth profile. The maximum nitrogen was set to be the pure nitride . These two scenarios were used as simulation inputs to assess the impact of N profile to . The various constants used in simulations are listed as the inset. (b) Simulation output (at ) for the corresponding energy band diagrams shown in (a). It is assumed that the depth of distributed nitrogen concentration is kept equal. In the inset of Fig. 2(a), and are conduction band offset and valence band offset, respectively.
Tunneling probability (TP) for electrons and holes under various biasing conditions. TP was obtained from simulation result by using our proposed model. The tunneling probability ratio (TP ratio) is defined as .
The gate leakage current density for and under various bias conditions. The gate current density ratios of the steep profile to the smooth profile for were also presented. The carrier transport mechanism in the bias range of ratio can be attributed to the direct tunneling, which is verified by conduction processes fitting (see the Ref. 7).
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