Apparent positive carrier conduction in SiO2 films and implications for MOSFET scaling

Summary form only given. Measurements of what has been called hole current in thin (90-Å) SiO₂ films with negative gate voltage are analyzed to show that the conduction mechanism can alternatively be explained as the bulk-limited process of field-assisted thermal emission of electrons from traps in the oxide, i.e., the Poole-Frenkel (P-F) effect. These results may help resolve the current debate over the exact mechanisms of gate current flow and subsequent degradation due to hot-carrier effects in MOSFETs. It seems reasonable that the component of gate current in MOSFETs that appears under high V_D, low V_G stress is due to a P-F mechanism of electron emission, rather than the conduction of holes through the oxide. The P-F effect can also explain the positive charge trapping found in MOSFETs under the bias conditions considered here; P-F emission of electrons from Coulombic traps aided by the applied field leaves positive space charge behind, since these traps are neutral when filled