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UFSOI Silicon-On-Insulator MOSFET Models

Introduction to User's Guide: UFSOI Model Description

SOISPICE-5.0 (an enhanced version of Spice2) contains the versions of the process/physics-based UFSOI MOSFET models that were released in January 2000. (Later versions are released only in the UFSOI/API/Spice3 program.) The models are charge-based with five terminals, and have a floating-body option. The model for the fully depleted (FD) device properly accounts for the charge coupling between the front and back gates, and includes a two-dimensional analysis of the electrostatic potential in the SOI film and underlying BOX for subthreshold-region operation. The model assumes that the film is strongly FD, except in and near the accumulation region where it accounts for the majority-carrier charge, and hence dynamic floating-body effects. The non-fully depleted (NFD, which in later releases is evolved to UFPDB) device model properly accounts for DC as well as dynamic floating-body effects defined by capacitive coupling and carrier recombination/generation. Both models include an optional quasi-2D accounting for the (coupled) parasitic BJT (current and charge), which can be driven in the floating-body mode by transient body charging current and/or generation current, including that due to impact ionization which is characterized by a non-local, carrier temperature-dependent model for the ionization rate integrated across the channel(s), (optional) LDD, and drain. The charge modeling has been recently upgraded; all terminal charges (including MOS and bipolar components) and their derivatives are continuous for all bias conditions. Substrate depletion charge under the source and drain regions, which becomes important when the BOX is scaled, is included as components of source, drain, and back-gate charge. Temperature dependence for both models is also implemented, without the need for any additional parameters, as is physics-based noise modeling for AC simulation, which accounts for thermal noise from the channel and parasitic series resistances, shot noise at the source and drain junctions, and flicker noise in the channel. The temperature-dependence modeling is the basis for a self-heating option, which uses special iterate control for the local device temperature node that yields good convergence even for large circuits.

Because of the process basis of the models, parameter evaluation can be based in part on device structure, and hence can be done unequivocally, avoiding self-heating and pulsing (floating-body) problems in the needed data acquisition. Both the FD and NFD models have been extensively exercised and refined in DC, transient, and AC device and circuit simulations. The User's Guide describes the use of the UFSOI models in SOISPICE-5.0, and includes citations of papers and reports that detail the physical modeling. The Guide is written as a supplement to the original "SPICE Version 2G User's Guide" from the University of California, Berkeley.

The executable file (soispice5.0) can be downloaded by clicking "Download Software". The tar file to be downloaded includes simulation examples, postscript files of the User's Guide and a report on process-based UFSOI parameter evaluation, and the University of Florida (and UCB) COPYRIGHT statement.

Last updated on July 2, 2002.