Electron-Related Phenomena at the $\hbox {TaN/Al}_{2} \hbox {O}_{3}$ Interface

The goal of this work is to study the transient electrical features of metal/high-k interface in MOS stacks. To this aim, electrons are injected from the gate of TaN/Al₂O₃/SiO₂/p-Si capacitors in pulsed regime. The displacement current flowing during the pulse front is detected, and the capacitance is extracted. As a result, for the first time, a flat-band instability related to electron trapping in states near the metal/high-k interface is measured on a millisecond timescale. A picture of the time evolution of the charge density inside the oxide bulk is drawn, with the aid of a finite-element simulator. Reliability of the metal/high-k interface is also investigated by performing stress experiments in pulsed conditions. It is shown that after a certain number of pulses, the creation of new traps at the top interface of the MOS stack becomes relevant.