RF noise simulation for submicron MOSFET's based on hydrodynamic model

Abstract

As the cut-off frequency of CMOS technology improves, RF designs are increasingly taking advantage of CMOS technology due to the promise of integrating whole systems on a single chip. Although accurate MOSFET noise modeling is indispensable for low noise design, the noise behavior in short channel MOSFETs is not yet well understood. This problem is particularly acute in state-of-the-art MOSFET technologies because of various second-order effects caused by complex processing such as new drain structures, gate overlap effects, nonuniform substrate doping profiles, etc. Therefore, the capability to exploit multi-dimensional device simulation to extract these physical dependencies of noise is highly attractive. Recently several studies have reported MOSFET noise simulation results based on IFM (impedance field method) and the DD (drift-diffusion) model (Donati et al, 1998). However, in contrast to single transport models like DD, higher order moments such as those captured by the HD (hydrodynamic) formulation are needed for noise modeling. Nevertheless, the HD model in two-dimensional noise simulation involves four times larger matrices and to date has not been used for noise analysis. In this paper, a mixed approach of one-dimensional active transmission line modeling and two-dimensional HD device simulation is used. The active transmission line analogy greatly saves computation time while the local information from the device simulator retains simulation accuracy. Noise simulation validity and errors are also discussed.