The impact of longitudinal nonuniform fin-thickness on quasi-ballistic transport in FinFETs

The impact of fin-thickness nonuniformities on carrier transport in FinFETs is analyzed with a quasi-ballistic transport model based on the multi-subband Monte Carlo technique. Silicon channels featuring thickness constrictions or enlargements show subband energy variations due to the changes in vertical quantization along the fin. We found that the impact on the on-current is larger when the nonuniformities are located close to the virtual source of the device. Furthermore, the sensitivity of on-current to thickness nonuniformity is essentially the same when considering different crystal orientations. Comparison with drift-diffusion simulations reveals quantitative and qualitative differences in the predicted drain current trends of these nanoscale, quasi-ballistic MOS devices.