On the effect of interface traps on the carrier distribution function during hot-carrier degradation

We study the effect of interface states, generated during hot-carrier stress, on the carrier energy distribution functions (DFs) and check whether this effect perturbs the results of our hot-carrier degradation model. These studies are performed using SiON nMOSFETs with a gate length of 65 nm as exemplary devices. We carry out simulations with different values of the spatially uniform interface state density (N
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) as well as with a coordinate dependent N
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evaluated for real stress conditions. In both cases, the effect of N
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on carrier distribution functions appears to be strong. As for the degradation characteristics, we show that N
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profiles computed with perturbed distribution functions can be substantially different from those obtained with non-perturbed DFs, especially at long stress times. The same trend is visible also for changes in the linear drain current. Additional simulations performed for operating conditions with and without the effect of N
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show that if this effect is not taken into account, this leads to severe underestimation of the device life-time.