On the distribution of the FET threshold voltage shifts due to individual charged gate oxide defects

Abstract

The factors contributing to the FET threshold voltage shift Δνth caused by charging of an individual trap, such as during Random Telegraph Noise (RTN), are discussed by analyzing device-calibrated simulation data. The Δνth distribution is observed to be a convolution of i) the position of the trap along the channel, randomized by ii) the random dopant distribution (RDD) responsible for percolative transport in the FET channel. In our TCAD simulation data the RDD component is observed to be roughly log-normally distributed. “Meta-simulations” varying this log-normal component are able to qualitatively reproduce a range of observed Δνth distribution shapes. In longer devices and/or in devices with high channel doping (or otherwise highly randomized channel potentials), the Δνth distribution tends toward log-normal. In the other, more relevant cases, the exponential Δνth distribution appears to be an acceptable approximation.