Errors in Projecting Gate Dielectric Reliability From Fowler–Nordheim Stress to Direct-Tunneling Operation

The extrapolation of gate dielectric reliability of devices that are stressed in the Fowler-Nordheim (F-N) tunneling regime but operate in the direct-tunneling (D-T) region is analyzed using the time-dependent dielectric-breakdown power law model. Due to the differences in the slopes of the gate current versus voltage characteristics between F-N and D-T, the widely established practice of directly extrapolating the time to breakdown from stress to operating conditions is, in general, not rigorously correct. Reliability projections across a wide voltage space can have significant errors, and the operating voltage that a technology can safely sustain may be overestimated.