Modeling Aspects of Sub-100-nm MOSFETs for ULSI-Device Applications

Ultrathin oxides (1-3 nm) are foreseen to be used as gate dielectric in complementary-MOS technology during the next ten years. Nevertheless, they require new approaches in modeling and characterization due to the onset of quantum effects. Predicting device characteristics including quantum effects requires solving of Schroumldinger's equation together with Poisson's equation. In this paper, Poisson's equation is solved in two dimensions (2-D) over the entire device using Green's function approach, while Schroumldinger's equation is decoupled using triangular-potential-well approximation. The carrier density thus obtained is included in the space-charge density of Poisson's equation to obtain quantum-carrier confinement effects in the modeling of sub-100-nm MOSFETs. The framework also consists of the effects of source/drain-junction curvature and depth, short-channel effects, and drain-induced barrier-lowering effect. The 2-D potential profiles thus obtained with above said effects form the basis for an estimation of threshold voltage. Using this potential distribution, the transfer characteristics of the device are also evaluated. The method presented is comprehensive in the treatment, as it neither requires self-consistent numerical modeling nor it contain any empirical or fitting expression/parameter to provide formulation for quantized-carrier effect in the inversion layer of MOSFETs. The results obtained show good agreement with available results in the literature and with simulated results, thus proving the validity of our model