Model Description

The Agilent Root MOSFET model applies to MOS devices the same database modeling principles as those used in the Root FET model. This three-terminal model can be applied to vertical, LD, and power MOS devices, where substrate effects do not need to be a part of the model. It can be used for both NMOS and PMOS devices. As with the Root FET model, the Root MOS model is generated from small-signal S-parameters measured at numerous bias points over the entire operating current-voltage (IV) plane.

Based on current and power dissipation device compliances you provide in software, the data acquisition system calculates the safe operating range for the device. Within this region, the model takes data adaptively at multiple bias points, depending on the specific nonlinearities of the device. Measurements are densely spaced in the most nonlinear regions, such as at the knees of the IV curves and the onset of breakdown, and less densely spaced in linear regions.

The data set of internodal nonlinear current and charge components at each bias point is then mathematically generated and stored. The model is thus generated without the usual need for simulation and optimization as required by all previous empirical models. The Root MOS model may thus capture nonlinear device behavior for any MOSFET device for which measured data can be taken but for which there are no good physical or empirical models.

The data acquisition system sets the DC bias levels and controls the system hardware to take the DC and S-parameter measurements, based on your inputs. The model generator processes the measured data and generates the lookup tables required by a circuit simulator. It produces data files that are directly readable by the Agilent RF and Microwave Design System (MDS). Both IC-CAP and MDS can be run simultaneously in the X Windows environment. During a simulation, the tabular state-function data from the generated Agilent Root MOS model is interpolated using multidimensional spline functions to emulate the terminal characteristics of the device.

The model includes a link to the MNS microwave nonlinear simulator, to allow verification of the model in IC-CAP.