Deuterium passivation of interface traps in MOS devices

The mechanism for deuterium passivation of interface traps in MOS devices is studied. Normal channel hot electron (CHE) stress was performed on hydrogen-passivated devices to locally desorb hydrogen from the interface at the drain region. The stressed devices were annealed in deuterium at 400 degreesC, resulting in a full recovery of device characteristics. These devices were then subjected to CHE stress again in two modes. Some of them were stressed in the normal mode while others were stressed in the reverse mode in which the source and drain were interchanged. Compared with hydrogenated devices, these deuterated devices under the normal stress exhibit a significant reduction in interface trap generation and threshold voltage shift. In contrast, insignificant reliability improvement was observed for the reverse stress case. The asymmetric degradation behaviors on these deuterated devices suggest that the effectiveness of implementing deuterium to improve device reliability is limited by its replacement of pre-existing hydrogen at the oxide/silicon interface.