Abstract
In this study, functional reliability of MOS transistors with oxide thickness ranging from 3.3 nm down to 1.2 nm is investigated in detail. In contrast with most reliability tests which focus on oxide reliability, various mechanisms resulting in transistor performance degradation are examined, while the on-state drain conduction current and off-state drain leakage current are the two most decisive device parameters that dominates MOS transistor functional reliability in the ultra-thin oxide regime. The degradation of off-state drain leakage current is caused by lately observed oxide soft-breakdown within the gate-to-drain overlap area, and its dominance tends to grow with scaling oxide thickness. Through experimental data analyses and theoretical calculations, we verified the dependences of device lifetime on oxide electric field, failure rate and device dimension. On the basis of physical mechanisms and models, we propose a methodology for MOS transistor functional reliability evaluation and a correlated unified functional reliability model which may contribute to the microelectronics technology development in the near future.