Lidia Dobrescu

The suspended-gate MOSFET (SG-MOSFET): a modeling outlook for the design of RF MEMS switches and tunable capacitors

This paper reports on the modeling and key design aspects of an innovative MEMS device: the suspended-gate MOSFET (SG-MOSFET). Based on the coupled-electromechanical equations describing the suspended gate actuation, we present the investigation of the pull-in voltages and of the capacitance switching and tuning ranges for RF applications. A quasi-analytical model is developed for the gate-to-substrate capacitance of the SG-MOSFET and then, validated by numerical simulation. A SPICE macromodel using a polynomial voltage-controlled source is validated for the DC simulation of the SG-MOSFET. Guide lines for the low-voltage design of an SG-MOSFET RF switch are detailed.

From Ψ-MOSFET with silicon on oxide to Ψ-MOSFET with silicon carbide on nitride

The Ψ-MOSFET is a device used in SOI electrical characterization. The aim of this paper was to establish a comparison between these transistors made in four variants: (1) with silicon film on buried oxide; (2) with silicon carbide film on buried oxide; (3) with silicon film on buried nitride; and (4) with silicon carbide film on buried nitride. ATLAS software simulated these structures. Besides this virtual experiment, a more complex model for the flat-band voltage is provided.

A designing roule for a pressure sensor with PZT layer

In the pressure sensors domain, the SOI structures bring some advantages: electrical insulation, high temperature sensors, an excellent etch stop layer (buried oxide), compatibility with microelectronic technology, lowering in thermal noise. The goal of this paper is to highlight a pressure sensor based on a coupling between piezoelectric effect in PZT and an /spl Psi/-MOSFET. The analytical models, that will be presented, stand for a useful tool at a first iteration of the sensor designing.

Alternative methods of parameters extraction based on the Pseudo-MOS technique

The pseudo-MOS transistor is a dedicated device for in situ electrical characterization of the SOI wafers. In this paper were extracted some parameters for a 200nm Si-film manufactured in SIMOX technique. In this scope, experimental Curves I/sub D/-V/sub G/, I/sub D/-V/sub D/ in inversion and accumulation were used, This work presents an alternative method for the threshold and fiat-band voltages extraction, using the Non-linear Electrical Conduction Theorem.

The influence of buried insulator type and film thickness on threshold voltage of a partially and fully depleted SOI-MOSFET

Nowadays SOI technologies represent a milestone in the fabrication of devices and integrated systems on thin films. The analytical models for the threshold voltage are useful for many SOI devices. Our analysis has focused on partially and fully depleted films, achieved on insulators like oxide, nitride or oxinitride. This paper gives a simple and accurate estimation of the threshold voltage. The results were in a good agreement both with PISCES numerical simulations and with experimental data.

MOS saturation model based on channel resistance

Actual MOS transistors models only use empirical models for the variation of the drain current in saturation. This is due to the bidimensional character of the MOS transistor channel. Gradual approximation can no longer be used for the whole transistor analysis due to the channel length modulation. But the gradual approximation still stands for the effective channel length of the transistor. And this gives a good hint to where an analytical model for saturation could have its roots. This paper proposes to present one such analytical model based on experimental data and on a determined constant channel resistance ratio.

A New Class of S-Type Current Controlled Nonlinear Negative Resistances

The paper presents a new method for generating S-type nonlinear current controlled negative resistances. The presented method can be used to obtain a large number of nonlinear resistances. We apply the method for a negative resistance device, using bipolar transistors, described by theoretical characteristics and performances and we compare the results with the theoretical specifications

Modeling the suspended gate MOSFET used as voltage programmable switch

This paper is a new approach to investigate and model the behaviour of the SGMOSFET with an external force applied on the mobile gate. Mechanical influences on the device threshold voltage V/sub T/ are presented together with the advantages and the limitations of this operating regime of the SGMOSFET.

Image force effect on forward characteristic of a rectifier metal-semiconductor contact

The image force effect is appreciated, especially, for the reverse regime of the rectifier metal-semiconductor contact, causing a weak dependence of the saturation current on the applied voltage. Applying this concept to the forward bias, at high values of currents, the ideality factor has an important increase. Combining this effect with the effect of the series resistance, which is important in the same range of currents, an important depreciation of the rectifier properties is observed.

The threshold voltage model of a SOI-MOSFET on films with Gaussian profile

The analytical models for electric field and potential distributions are useful for a lot of SOI devices, like SOI-MOSFET, SOI-BJT, three-dimensional device, SOI sensors and the others. For example, they are necessary for establish the inversion or accumulation conditions for front and back interfaces. The paper refers to a one-dimensional analysis, both for partially and fully depleted devices on films with nonuniform doping. The goal of this paper is to obtain an accurate model for the field and the potential distribution in the SOI structures with Gaussian doping concentration of impurities in the film. The results have been used for threshold voltage deduction, but they represent a reference point in developing of new models for SOI-devices fabricated on Gaussian profile films. In the fully depleted films case, the depletion of the silicon substrate for gate voltages that entirely depleted the film was considered. The results were compared with PISCES numerical simulations and were in good agreement.