Impact of carrier injection in 2.2 nm-thick SiO2 oxides after first and substrate enhanced electron injection

In this study, we have characterized the degradation of metal–oxide–semiconductor structures having a 2.2 nm-thick gate oxide, after uniform tunnelling injections in large metal–oxide–semiconductor field-effect-transistors or localized channel hot-carrier injections resulting from either first impact ionization or substrate enhanced secondary impact ionization in 50/0.1 μm or 50/0.15 μm N channel devices. The degradation of the oxide is investigated by following the changes of the electrical parameters of the transistor, the gate leakage current, and the interface state density measured by charge pumping measurements. Uniform tunnelling injections are found not to degrade the oxide and the structure up to 300 C/cm2 of injected charge. The induced damage is found to result from acceptor-type defects located at the Si/SiO2 interface and extends below the channel, without any recorded-trapped charge in the interior of the oxide. Substrate enhanced electron injection induce a reduction of carrier mobility and a larger increase in gate leakage current than the one recorded after first impact ionization injection and uniform stresses.