Barrier Lowering and Backscattering Extraction in Short-Channel MOSFETs

Abstract

In this paper, we propose a fully experimental method to extract the barrier lowering in short-channel saturated MOSFETs using the Lundstrom backscattering transport model in one-subband approximation and carrier degeneracy. The knowledge of barrier lowering at the operative bias point in the inversion regime is of fundamental importance in device scaling. At the same time, we also obtain an estimate of the backscattering ratio and the saturation inversion charge. With respect to previously reported works on extraction of transport parameters based on the Lundstrom model, our extraction method is fully consistent with it, whereas other methods make a number of approximations in the calculation of the saturation inversion charge, which are inconsistent with the model. The proposed experimental extraction method has been validated and applied to results from device simulation and measurements on short-channel poly-Si/SiON gate nMOSFETs with gate lengths down to 70 nm. Moreover, we propose an extension of the backscattering model to the case of 2-D geometries (e.g., bulk MOSFETs). We found that, in this case, backscattering is governed by the carrier transport in a few nanometers close to the silicon/oxide interface and that the value of the backscattering ratio obtained with a 1-D approach can be significantly different from the real 2-D value.