Local Thinning-Induced Oxide Nonuniformity Effect on the Tunneling Current of Ultrathin Gate Oxide

The significance of the oxide thickness nonuniformity effect on the current density–voltage (J–V) characteristics of gate oxide in an ultrathin region is demonstrated. Theoretical J–V curves of metal-oxide-semiconductor (MOS) under small and large biases were derived according to the existing literature, and were used to study the J–V characteristics of an MOS capacitor containing different local oxide thicknesses was studied. An effect we called "local thinning", which stretches out the J–V curves, was observed. The magnitude of the tunneling current is governed by the thinner oxide region in the capacitor although this region only occupies a relative small area ratio. Experiments were performed on intentional etching of silicon wafers to reinforce the oxide thickness nonuniformity effect. The experimental results are explainable by the model observation.