Towards the nanoscale: influence of scaling on the electronic transport and small-signal behaviour of MOSFETs

Abstract

In this work, the influence of downscaling bulk MOSFETs below the 100 nm range on their static and dynamic behaviour is analysed by means of a particle-based Monte Carlo simulator. Internal transport conditions are investigated throughout the extensive information provided by numerical simulations (electric fields, concentration, velocity and energy of carriers, energy bands, etc), and a physical interpretation is given to the dynamic behaviour observed. Results show that even when the most favourable downscaling conditions are considered (that is, following the constant field scaling rules), significant two-dimensional electrostatic effects, together with reduced gate control, lead to the degradation of important figures of merit such as gate-to-source capacitance, transconductance or maximum oscillation frequency. Conventional MOSFET geometries are therefore near to a limit when reaching gate lengths of 50 nm, and the use of alternative solutions is necessary in order to maintain the proper electrostatic behaviour of a ‘well-tempered’ transistor.

Monte Carlo Study of Dopant-Segregated Schottky Barrier SoI MOSFETs: Enhancement of the RF Performance

“…The variation of τ with L dop is strongly minimized by the presence of the doped layer regardless of its width (not shown in the graphs). The values of τ are clearly below the values obtained for a conventional bulk MOSFET [32] and are also lower that the previously shown average transit time of the carriers in the channel.…”

“…SSEC circuit considered [29] are obtained from the admittance ones, given by the Fourier analysis of the transient response of the current, as shown in [32]. More details about the EMC device simulator employed can be found elsewhere [29], [33].…”

Electron mobility in quasi-ballistic Si MOSFETs

“…The problem of the electric conductivity in ballistic and quasi-ballistic transistors triggers a considerable effort devoted to formulation and analysis of theoretical models [2][3][4][5], numerical solutions by Monte Carlo simulations [6][7][8][9][10][11] or the Green function method [12]. On the other hand, an experimental approach that can be applied to investigate the ballistic motion in the case of Si MOSFETs is based on a comparison of measured drain current with the theoretical ballistic limit that enables estimation of the transmission coefficient [13,14].…”