Local field effect on charge-capture/emission dynamics.

ABSTRACT

Charge-capture/emission is ubiquitous in electron devices. Its dynamics often play critical roles in device operation and reliability. Treatment of this basic process is found in many text books and is considered well understood. As in many electron device models, the individuality of immobile charge is commonly replaced with the average quantity of charge density. This has worked remarkably well when large numbers of individual charges (ensemble) are involved. As device geometries become very small, the ensemble "averaging" becomes far less accurate. In this work, the charge-capture/emission dynamic of Metal-Oxide-Semiconductor-Field-Effect-Transistor (MOSFET) is re-examined with full consideration of individual charges and the local field in their immediate vicinity. A dramatic modification of the local band diagram resulted, forcing a drastic change in emission mechanism. The implication is that many well-understood phenomena involving charge capture/emission will need to be reconsidered. As an example, this new picture is applied to the random telegraph noise (RTN) phenomenon. When the screening of a trapped charge by a polar medium such as SiO2 is quantitatively accounted for in this local field picture, a new physically sound RTN emission mechanism emerges. Similarly, the dynamics of post-stress recovery of Negative-Bias-Instability of p-channel MOSFET can be more rationally explained.