Weibull slope and voltage acceleration of ultra-thin (1.1–1.45 nm EOT) oxynitrides

The reliability of ultra-thin silicon oxynitride gate dielectrics was investigated in terms of the Weibull slope of the <f>tbd</f> distributions, and the voltage acceleration factor. High field <f>tBD</f> statistics were extrapolated using a worst-case linear fit, to the low field region. The samples showed low voltage acceleration, which degrades reliability, but this is overcome by high Weibull slopes (<f>β</f>), which improve reliability. The high <f>β</f> values were investigated by monitoring the change in <f>β</f> as gate current increased during CVS. We saw the Weibull slope change from &ap;1 at low current to 2 at high current, indicating that breakdown results from 2-trap conduction. Charge pumping measurements showed that the trap generation rate at the SiON/Si interface, where most of the Nitrogen resides was very low. Thus it was concluded that there is a much higher trap generation rate in the bulk than at the interface and this is responsible for the values of <f>β</f>. [Copyright &y& Elsevier]