New insights into threshold voltage shifts for ultrathin gate oxides MOSFETs

摘要

Threshold voltage (V/sub th/) shifts of p- and n-channel MOSFETs during stress are analyzed from both experiments and simulation. The result of the analysis showed that the V/sub th/ shift is mainly induced by the carrier channel mobility degradation. This result can explain the polarity dependence of V/sub th/ shifts in p- and n-channel MOSFETs. Besides, it suggested that the commonly accepted idea that V/sub th/ shifts are due to Coulombic charge generation in the oxide affecting the surface potential is not accurate. It also suggested that the proposed oxide degradation mechanisms, based on V/sub th/ shifts measured using I/sub d/-V/sub g/, may not be accurate.