Comparison of Three Quantum Correction Models for the Charge Density in MOS Inversion Layers (original) (raw)
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IEEE Electron Device Letters, 2000
This letter reports for the first time, accurately extracted experimental data for the threshold voltage shift (1V T ) due to quantum mechanical (QM) effects in hole inversion layers in MOS devices. Additional experimental results are presented for QM effects in electron inversion layers. Compared to classical calculations, which ignore QM effects, these effects are found to cause a significant increase in the threshold voltage (100 mV) in MOSFET devices with oxide thicknesses and doping levels anticipated for technologies with gate lengths 0.25m. 1V T has been determined from experimental devices with doping levels ranging from 5 2 10 15 -1 2 10 18 /cm 3 , and recently developed theoretical models are found to agree well with the results. In addition, an innovative technique using a two-dimensional (2-D) device simulator in conjunction with the experimental capacitance-voltage (C-V ) characteristics has been developed in order to more accurately extract various physical parameters of the MOS structure.
Quantum-mechanical modeling of accumulation layers in MOS structure
IEEE Transactions on Electron Devices, 1992
An original method is used for the quantum-mechanical modeling of n-type silicon accumulation layers. Contrarily to previous methods, which were only valid near 4.2 K, our approach is valid up to room temperature and beyond. The obtained self-consistent results are compared with those of the standard classical model for the accumulation layer, and the differences between them are found to be relevant for the modeling of important device applications. In particular, it is shown that the semiconductor voltage drop and the oxide barrier height for Fowler-Nordheim (F-N) tunnel injection are largely modified by the quantization of the accumulation layer. The dependences of these two magnitudes (accumulation voltage drop and effective F-N barrier height) on oxide electric field and substrate doping are reported. Experimental F-N current-voltage characteristics of production-quality ( 100 ) -Si(n) / Si02/poly-Si(n+) MOS capacitors are used to validate the presented quantum results and to show that the standard classical model is not adequate even if the barrier height is considered as a fitting parameter. Finally, approximate analytical expressions giving the semiconductor voltage drop and the effective F-N barrier height as a function of oxide field and substrate doping are derived for ( 100 } and ( 111 ) n-type silicon at 77 and 300 K. These analytical expressions allow to introduce the effects of the quantization of accumulation layers into even very simple device simulators.
IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems, 1989
A mobility curve for electrons in MOSFET's inversion charge layer is determined from measured drain current of transistors produced by a wide range of MOS technologies. A comparison between this mobility curve and previously published results shows that a truly universal mobility curve does not exist and only "local" universal mobility curves can be expected, i.e., unique mobility curves which are valid over a finite range of MOS technologies and/or over a particular set of fabrication facilities. However, its basic characteristics of being technology independent over a wide range of process variation point out the potential of using such a local universal mobility curve as a powerful basis for developing predictive device modeling tools. This potential is demonstrated for an analytical MOSFET model and a twodimensional device simulator where the mobility models have the general characteristics of experiment based local universal mobility curves.
Solid-State Electronics, 2004
A new surface-potential-based MOSFET model that independently accounts for the quantum mechanical effects (QME) in the accumulation and inversion regions is proposed. The quantum modeling of the accumulation layer relies on the triangular potential well approximation whereas the variational approach to the solution of the Schr€ odinger and Poisson equations is used for the inversion layer. Using no additional parameter, our quantum relationships offer simple expressions in terms of process parameters and bias. The resulting model is fully dependent on all terminal voltages and gives an accurate description of the surface potential and its derivatives in all regions of operation, from accumulation to inversion. The results of this compact model are compared with both self-consistent solutions of Schr€ odinger and Poisson equations, and experimental data. An excellent agreement is found for both I-V and C-V characteristics.
Effects of the inversion layer centroid on MOSFET behavior
IEEE Transactions on Electron Devices, 1997
The effects of the average inversion-layer penetration, which are termed the inversion-layer centroid, on the inversion-charge density and the gate-to-channel capacitance have been analyzed. The quantum model has been used, and a variety of data have been obtained by self-consistently solving the Poisson and Schrödinger equations. An empirical expression for the centroid position that is valid for a wide range of electrical and technological variables has been obtained and has been applied to accurately model the inversion-layer density and capacitance.
Efficient MultiDimensional Simulation of Quantum Confinement Effects in Advanced MOS Devices
2004
We investigate the density-gradient (DG) transport model for efficient multi-dimensional sim- ulation of quantum confinement effects in advanced MOS devices. The formulation of the DG model is described as a quantum correction to the classical drift-diffusion model. Quantum con- finement effects are shown to be significant in sub-100nm MOSFETs. In thin-oxide MOS capaci- tors, quantum effects may reduce gate capacitance by 25% or more. As a result, the inclusion of quantum effects in simulations dramatically improves the match between C-V simulations and measurements for oxide thickness down to 2 nm. Significant quantum corrections also occur in the I-V characteristics of short-channel (30 to 100 nm) n-MOSFETs, with current drive reduced by up to 70%. This effect is shown to result from reduced inversion charge due to quantum con- finement of electrons in the channel. Also, subthreshold slope is degraded by 15 to 20 mV/decade with the inclusion of quantum effects via the density-grad...
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.
Modeling of quantum effects for ultrathin oxide MOS structures with an effective potential
IEEE Transactions On Nanotechnology, 2002
In this paper, the effectiveness of the effective potential (EP) method for modeling quantum effects in ultrathin oxide MOS structures is investigated. The inversion-layer charge density and MOS capacitance in one-dimensional MOS structures are simulated with various substrate doping profiles and gate bias voltages. The effective mass is used as an adjusting parameter to compare results of the EP model with that of the Schrödinger-Poisson solution. The variation of this optimum parameter for various doping profiles at different gate voltages is investigated. The overestimated average inverse charge depth by the EP method is quantified and its reason explained. The EP model is a good practical simulation tool for modeling quantum effects but more work needs to be done to improve its accuracy near the interface.
IEEE Transactions on Electron Devices, 1996
Successful scaling of MOS device feature size requires thinner gate oxides and higher levels of channel doping in order to simultaneously satisfy the need for high drive currents and minimal short-channel effects. However, in deep submicron (50.25 pm gate length) technology, the combination of the extremely thin gate oxides (tax 5 10 nm) and high channel doping levels results in transverse electric fields at the Si/SiOz interface that are sufficiently large, eve= near threshold, to quantize electron motion perpendicular to the interface. This phenomenon is well known and begins to have an observable impact on room temperature deep submicron MOS device performance when compared to the traditional classical predictions which do not take into account these quantum mechanical effects. Thus, for accurate and efficient device simulations, these effects must be properly accounted for in today's widely used moment-based device simulators. This paper describes the development and implementation into PISCES of a new computationally efficient three-subband model that predicts both the quantum mechanical effects in electron inversion layers and the electron distribution within the inversion layer. In addition, a model recently proposed by van Dort et al. has been implemented in PISCES. By comparison with self-consistent calculations and previously published experimental data, these two different approaches for modeling the electron inversion layer quantization are shown to be adequate in order to both accurately and efficiently simulate many of the effects of quantization on the electrical characteristics of N-channel MOS transistors.
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.