Mechanism of leakage current through the nanoscale SiO2 layer

Abstract

We clarify the mechanism of leakage current through the nanoscale ultrathin silicon dioxide (SiO2) layer in a metal-insulator-semiconductor structure based on the multiple scattering theory when technologically important phosphorus doped polycrystalline silicon is adopted as the gate electrode. We also derive an analytic expression for the direct tunneling current, and show that its measurement presents an excellent opportunity to determine the effective mass of an electron in the SiO2.

Ultrathin gate dielectrics for silicon nanodevices

“…The reported values of electron effective mass for the direct tunnel current regime are in the range 0.29-0.32m 0 for the WKB approximation with a parabolic Ek relationship [9,[17][18][19]. On the other hand, the tunnel current more accurately calculated by the multiple scattering theory has been fitted to measured current with the effective mass of 0.36m 0 for oxides thicker than 3 nm [9]. We have also compared measured tunnel current with the multiple scattering theory for sub [20].…”

“…In the analysis of tunnel current we encounter three crucial problems as follows. (1) An appropriate theoretical framework must be chosen on the basis of WKB approximation [8], multiple scattering theory [9], or transverse-resonant method [10,11]. (2) The effective mass of tunneling electron must be properly given although the reported values exhibit the broad distribution from 0.29 to 0.5m 0 .…”

Semi-empirical and practical model for low-electric field direct tunneling current estimation in nanometer-thick SiO2films

“…It is considered that Fowler-Nordheim tunneling characteristics are reasonably well understood [4,5], while a complete understanding of the direct tunneling current characteristics is a work in progress [6,7]. In particular, direct tunneling current characteristics in nanometer-thick SiO 2 films in the low-electric field regime are still not understood well; theoretical calculation results do not always coincide with experimental results [8,9]. This paper describes a simplified model of the direct tunneling current characteristics of thin SiO 2 films.…”

Effects of interface roughness and conducting filaments in metal–oxide–semiconductor tunnel structures

“…A somewhat similar treatment uses multiple scattering theory instead of the WKB approximation to compute tunneling coefficients to provide clarification of mechanisms for leakage currents through ultrathin oxides. 4 A still more advanced treatment solves Poisson and Schrödinger equations selfconsistently for accumulated layers in MOS devices to calculate tunneling currents. 5 Nonuniformity in oxides are, typically, not treated theoretically due to the much increased complexity and computational demands.…”