Monte Carlo analysis of dynamic and noise performance of submicron MOSFETs at RF and microwave frequencies
In this paper, an ensemble 2D bipolar Monte Carlo simulator is employed for the study of static characteristics, high-frequency response and noise behaviour in a 0.3 µm gate-length n-MOSFET in common source configuration. Short-channel effects, such as velocity overshoot in the pinch-off region, together with the appearance of hot electrons at the drain end of the channel are observed in the static characteristics. Admittance parameters and the small-signal equivalent circuit have been calculated in order to characterize the dynamic response of the device. The use of a bipolar simulator allows one to study the dynamics of both types of carriers simultaneously. While the static results are dominated by the electron transport, the contribution of holes mainly affects the drain-substrate capacitive coupling. The noise behaviour of the simulated MOSFET is also studied (up to 40 GHz) by means of different parameters, such as the spectral densities of the current fluctuations at the drain and gate terminals (and their cross-correlation), normalized α, β and C parameters and NFmin . In the saturation regime, due to the presence of hot carriers, an increase in drain and gate noise with respect to the long-channel prediction has been found. Moreover, a stronger correlation between drain and gate noise is observed, especially at low drain current. Induced gate noise is found to play a crucial role in the determination of NFmin at high drain currents.