Electron-Related Phenomena at the TaN / Al 2 O 3 Interface

• Published in: IEEE transactions on electron devices Vol. 57; no. 3; pp. 637 - 643
• Main Authors: Rao, Rosario, Lorenzi, Paolo, Ghidini, Gabriella, Palma, Fabrizio, Irrera, Fernanda
• Format: Journal Article
• Language: English
• Published: 01.03.2010
• Subjects: Aluminum; Capacitance; Devices; Instability; Metal oxide semiconductors; Pictures; Stacks; Trapping
• DOI: 10.1109/TED.2009.2039100
• ISSN: 0018-9383

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 / Al 2 O 3 / SiO 2 / 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.