Fully-depleted SOI MOSFETs Research Articles

Comparison of SOI versus bulk performancesof CMOS micropower single-stage OTAs

The performances of micropower single-stage CMOS OTAs implemented in SOI or bulk technologies are compared. The improvements resulting from the superior device characteristics of fully-depleted SOI MOSFETs are discussed. Experimental verifications support the theoretical predictions.

SPICE model and parameters for fully-depleted SOI MOSFET's including self-heating

A simple methodology to accurately extract constant temperature model parameters from static measurements of fully-depleted SOI MOSFET current-voltage characteristics is demonstrated. Self-heating is included in an existing physically-based, short-channel bulk MOSFET model, PCIM, by allowing the temperature to change linearly with power dissipation at each bias point. Only a simple modification of the channel bulk charge in PCIM is necessary to adapt it for SOI. The temperature dependence of the physical parameters (mobility, flatband voltage, and saturation velocity) are also fitted and included in the model. Excellent fit to experimental fully-depleted SOI data is shown over a large range of bias conditions and channel lengths. Once the static SOI data is fitted, the constant temperature model parameters appropriate for circuit simulation are easily extracted.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Simulation of the transient characteristics of partially- and fully-depleted SOI MOSFETs

We present a numerical technique which employs a local-in-time initial guess for the transient simulation of SOI MOSFETs. Specifically, the goal of this work is to compute the transient drain current which exhibits overshoot. A critical factor in such computations is the choice of the initial guess at each time point after the gate ramp. Our numerical simulations have shown that the use of the previous time point solution as an initial guess in the Gummel iterations fails to predict the decay in the drain current from its maximum overshoot value. This difficulty is circumvented when the steady-state solution is used as a local-in-time initial guess. We use the diagonally implicit Runge-Kutta method for the time domain discretization. A fixed-point iteration technique is employed for the space domain iterations. To demonstrate the usefulness of the local-in-time method, numerical results of the transient drain current for various device parameters, such as the silicon film doping, silicon film thickness and back-gate bias are presented.

SOI MOSFET effective channel mobility

The standard bulk MOSFET definition for effective electric field is modified for SOI devices to account for nonzero electric field at the back oxide interface. The effective channel mobility in fully-depleted n-channel SOI MOSFET's is shown to be independent of applied backgate bias when the modified E/sub eff/ definition is used. The effective channel mobility as a function of E/sub eff/ is also shown to be independent of film thickness for fully-depleted devices. >