Relaxation effects in NMOS transistors after hot-carrier stressing

Abstract

Aging studies on NMOS transistors with dry oxides at room temperature have revealed that the creation of interface traps and the trapping of positive charge in the oxide associated with hot-electron effects are not permanent, but can be reversed to some extent if the transistor drain is grounded and left for some time. The relaxation is a substantial fraction of the original degradation at low degradation values and suggests that there is an annealing of some of the traps created by stressing. This annealing follows first-order kinetics for both created interface traps and trapped oxide charge, and is characterized by relaxation times τ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</inf> of 600-900 s.