Tunneling Effective Mass of Electrons in Lightly N-Doped $\hbox {SiO}_{x} \hbox {N}_{y}$ Gate Insulators

In this paper, we study the dependence of the tunneling effective mass of electrons on gate dielectric nitrogen concentration and thickness in MOSFETs with lightly doped silicon oxynitride (SiO_xN_y) gates. The direct tunneling current is modeled by applying a Schrodinger-Poisson solver with one-side-open boundary condition. The dependences of the effective mass on nitrogen concentration and dielectric thickness are extracted by fitting the computation results for the gate leakage current to the experimental data that we measured for samples with different thicknesses and nitrogen concentrations. Nitrogen concentration and thickness of samples are determined using X-ray photoemission spectroscopy. The obtained results show a strong dependence of the effective mass on the sample thicknesses and nitrogen concentration. The electron effective mass is found to increase as the thickness decreases, and the higher nitrogen concentration causes a reduction in effective mass.