The Relevance of Trapped Charge for Leakage and Random Telegraph Noise Phenomena

The current understanding of key reliability phenomena such as leakage and Random Telegraph Noise (RTN) is still incomplete. Models exist that explain simple cases (2-level RTN), yet experimental reports showed the occurrence of complex cases (e.g., coupled RTN, anomalous and temporary RTN) that deserve deeper investigation. In this paper, we focus on the often overlooked role of trapped charge in the electrostatic coupling among defects, entailing a multi-body problem, and on the related effects on leakage and RTN. The electric field in the dielectric is found to be usually dominated by the trapped charge rather than by the applied voltage, defying common beliefs and elegantly explaining some of the aforesaid complex scenarios. We demonstrate that such defects interactions are responsible for a strong modulation of the capture and emission time constants over time. Moreover, we highlight how defects capture/emission source/destination can change with the local field and therefore with the applied voltage, which gives rise to non-monotonic trends in c/e vs. applied voltage plot. This last point reveals that the classical formula adopted for the estimation of the defects vertical position within the dielectric is oversimplified and may lead to significant errors. The results of this study advance the understanding of leakage and RTN, and can be useful for the design of applications such as low-power Physical Unclonable Functions and True Random Number Generators.