Voltage-splitting technique for reliability evaluation of off-state mode of MOSFETs in ultrathin gate oxides

A simple and practical new methodology is proposed for reliability evaluation of off-state mode in ultrathin oxides. By applying a negative voltage on the gate while the drain region is biased at the operating voltage; the so-called voltage-splitting technique (VST), we successfully resolve the difficulty associated with the unrealistic high drain-bias stress otherwise required, which leads to the excessive damage to oxide integrity in the overlap region. In comparison with a high drain-bias stress, the time-dependent dielectric breakdown measurements using VST show the well-behaved breakdown distribution and correlate with the measured device characteristics. In addition, this methodology may provide a possible method to extrapolate stress data to operational voltage for realistic off-state reliability projection.