Effects of the inversion layer centroid on MOSFET behavior (original) (raw)
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Effects of the inversion-layer centroid on the performance of double-gate MOSFETs
IEEE Transactions on Electron Devices, 2000
The role of the inversion-layer centroid in a double-gate metal-oxide-semiconductor field-effect-transistor (DGMOSFET) has been investigated. The expression obtained for the inversion charge is similar to that found in conventional MOSFET's, with the inversion-charge centroid playing an identical role. The quantitative value of this magnitude has been analyzed in volume-inversion transistors and compared with the value obtained in conventional MOSFETs. The minority-carrier distribution has been found to be even closer to the interfaces in volume-inversion transistors with very thin films, and therefore, some of the advantages assumed for these devices are ungrounded. Finally, the overall advantages and disadvantages of double-gate MOSFET's over their conventional counterparts are discussed.
IEEE Transactions on Electron Devices, 2000
The influence of MOSFET channel material and channel structure on the inversion layer capacitance is examined. It is well known that the inversion layer capacitance depends strongly on the bandstructure of the channel, but we show that it also depends very strongly on the structure of the channel (e.g., bulk vs. ultrathin body, and the thickness of the body). These results provide some general insights into the channel material and structure tradeoffs that control the inversion layer capacitance-an increasingly important consideration as electrical oxide thicknesses continue to decrease and as new channel materials are considered.
Analytical Modeling of Metal Oxide Semiconductor Inversion-Layer Capacitance
Japanese Journal of Applied Physics, 1999
Electron wavefunctions confined in a logarithmic potential well formed in the inversion layer of a metal oxide semiconductor field-effect transistor (MOSFET) are given on the basis of generalized Airy functions. The charge centroid of electrons in the inversion layer has been calculated to derive the quantum mechanical inversion-layer capacitance by taking into account higher subband states. It is shown that the present analytical model can quantitatively explain the experimentally observed inversionlayer capacitance.
IEEE Transactions on Electron Devices, 2008
A semiempirical model was developed for calculating the inversion charge of cylindrical surrounding gate transistors (SGTs), including quantum effects. To achieve this goal, we used a simulator that self-consistently solves the 2-D Poisson and Schrödinger equations in a cross section of the SGT. By means of the proposed models, we correctly reproduced the simulation data for a wide range of the device radius and gate voltage values. Both the inversion charge and the centroid models consist of simple mathematical equations within an explicit calculation scheme suitable for use in circuit simulators.
IEEE Transactions on Electron Devices, 2007
An empirical expression is developed for the inversion layer centroid and the polysilicon-gate depletion region thickness for bulk MOSFETs with different crystallographic orientations. In particular, results for the most commonly used wafer orientations, i.e., (100), (110), and (111), are given. These expressions are used to accurately model the inversion charge (Q inv ) and the gate-to-channel capacitance (C gc ) of MOSFETs with gate oxides of nanometric thickness (t ox < 1 nm) and different surface orientations. The Poisson and Schrödinger equations are self-consistently solved for different values of silicon and polysilicon doping concentrations in these devices. Our results show important reductions of both Q inv and C gc because of the polysilicon depletion effect and the displacement of the inversion charge centroid from the interface to the silicon bulk as a consequence of quantum effects. These effects are very noticeable for gate-oxide thicknesses of around 1 nm and must be taken into account in the development of accurate MOSFET models. We show that this task can be performed by means of a corrected gate-oxide thickness, which includes both the effect of the inversion layer centroid Z I and the polydepletion region thickness Z D . To do this, we have developed an accurate model for Z I as a function of the inversion charge concentration, the depletion charge concentration, and the silicon doping concentration for the (100), (110), and (111) wafer orientations. The in-plane channel directions have been swept for each wafer orientation in order to study the validity of the model in depth. Similarly, we provide an expression for Z D as a function of the polydoping concentration. The gate-to-channel capacitance is also carefully and extensively analyzed. An analytical model for C gc is provided and tested for different values of oxide thickness, polysilicon doping, substrate doping, and gate voltage.
An Inversion-Charge Analytical Model for Square Gate-All-Around MOSFETs
IEEE Transactions on Electron Devices, 2000
A new approach to the analytical solution of the 2-D Poisson equation including the inversion-charge density in undoped square gate-all-around metal-oxide-semiconductor fieldeffect transistors has been developed. We have obtained functions with different degrees of complexity to calculate the electric potential in the devices under study. The results obtained are compared with the data simulated by solving the Poisson equation numerically. A good fit is achieved both for the electric potential and the inversion charge, which are calculated by means of Gauss's law.
Comparison of Three Quantum Correction Models for the Charge Density in MOS Inversion Layers
Journal of Computational Electronics, 2002
In order to obtain high density integration for MOS devices, it is necessary to reduce the gate oxide thickness and increase the substrate doping concentration. This results in a narrow and deep potential well in which electrons are confined at the semiconductor-insulator interface and it becomes necessary to take quantum mechanical (QM) effects into consideration. In this study, we compare
INVERSION TRANSITION REGION OF MOSFETS
A new technique is offered as an alternative to extract the threshold voltage of MOSFETs. It defines the threshold at the transition from subthreshold -to-strong inversion operation. Besides its stronger physical foundation, the method provides greater noise and measurement error immunity than conventional methods because, instead of the differentiation operations required by those methods, it is based on an auxiliary operator that involves integration of the drain current as a function of gate voltage. Threshold voltage values extracted using this method from synthetic and real long and short channel MOSFETs match very well those extracted by conventional methods.
Strained-Si on Si Ge MOSFET Inversion Layer Centroid Modeling
2001
An accurate model for the inversion charge centroid of strained-Si on Si Ge metal-oxide semiconductor field effect transistors (MOSFETs) has been developed including the dependencies on the germanium mole fraction, the doping concentration, and the width of the strained-Si layer. We have also obtained a good estimation of the inversion charge. The inclusion of quantum effects in classical simulators by means of a corrected gate-oxide width can be easily performed making use of this new model. Index Terms—Inversion layers, MOSFETs, SiGe, simulation.
Inversion Charge Quantization Model for Double Gate MOSFETs
Nanoscience &Nanotechnology-Asia, 2018
In this article we have developed an analytical model for Double gate Metal Oxide Semiconductor Field Effect Transistor (DG MOSFET) including Quantum effects. The Schrodinger-Poisson's equation is used to develop the analytical Quantum model using Variational method. A mathematical expression for charge centroid is obtained and then an inversion charge model was developed with quantum mechanical effects by means of oxide capacitance for different channel thickness and gate oxide thickness.