Analytic model of direct tunnel current through ultrathin gate oxides

A theoretical model for tunnel leakage current through 1.65-3.90-nm-thick g ate oxides in metal-oxide-semiconductor structures has been developed. The electron effective mass in the oxide layer and the Fermi energy in the n(+) poly-Si gate are the only two fitting parameters. It is shown that the cal culated tunnel current is well fitted to the measured one over the entire o xide thickness range when the nonparabolic E-k dispersion relationship for the oxide band gap is employed. The electron effective mass in the oxide la yer tends to increase as the oxide thickness decreases to less than 2.80 nm presumably due to the existence of compressive stress in the oxide layer n ear the SiO2/Si(100) interface. (C) 2000 American Institute of Physics. [S0 021-8979(00)05306-8].