Characterization of gate oxide degradation mechanisms in trench-gated power MOSFETS using the charge-pumping technique

The high-electric-field stress reliability of trench-gated power MOSFETS has been characterized using high-resolution scanning electron microscopy, transistor parameter, and charge-pumping measurements. Degradation due to electrical stress was observed to be in the form of positive charge accumulation at the drain edge of the channel. This results in an effective shortening of the electrical channel length. Oxide thinning at the trench corners together with sidewall roughness caused by the trench etch are suggested as the mechanisms responsible for this observation. Design approaches to alleviate this effect are demonstrated.