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Schematic illustration of the conduction band combination of a single layer oxide on silicon. Electrons are injected from the accumulated silicon interface into the oxide band gap followed by Fowler-Nordheim injection when reaching the oxide conduction band. Gap state injection occurs in the range xGI -xBI , Fowler-Nordheim injection beyond xBI . For a trap level below the silicon Fermi level, xGI = 0.
(a) Oxide conduction band for a stack with 1.5 nm SiO2 interlayer and an 18.5 nm thick high-k oxide with k = 25, for two values of the sharpness of the interlayer/high-k interface. (b) Probability Pt (x) for injection of an electron from the silicon Fermi level position at EF for the two potential distributions shown in (a). Band injection occurs at the end points of the Pt graphs, beyond which Pt is constant.
Trap distribution used in the calculations.
Time dependence of the flat-band voltage after switching on an oxide voltage of 4 V across the structure in Fig. 2 . Capture cross sections were set to σGI = 10−25 m2 and σBI = 10−21 m2. (a) Interlayer/high-k sharpness x 0 = 0.05 nm. (b) Interlayer/high-k sharpness x 0 = 0.3 nm. The dashed curves originate from capture into the oxide bulk and the point dashed curves from capture into the states close to the silicon interface in Fig. 3 . The solid curve is the total, given by the sum of those two.
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