Compact model for long-channel cylindrical surrounding-gate MOSFETs valid from low to high doping concentrations (original) (raw)
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Solid-State Electronics, 2009
This paper presents a charge-based compact model for predicting the current-voltage and capacitancevoltage characteristics of heavily doped long-channel cylindrical surrounding-gate (SRG) MOSFETs. Starting from Poisson's equation with fixed charge and inversion charge terms, a closed-form equation of inversion charge is obtained with the full-depletion approximation. Substituting this inversion charge expression into Pao-Sah's dual integral, a drain current expression with concise form is derived. Based on the Ward-Dutton linear-charge-partition method and the current continuity principle, all trans-capacitances are obtained analytically. The developed model is valid in all operation regions from the subthreshold to strong inversion and from the linear to the saturation region without any smooth function. The model predictions have been extensively compared with 3D numerical simulations and a good agreement is observed in most of the operation regions with a wide range of geometrical parameters.
International Journal of Circuits, Systems and Signal Processing, 2021
In this paper, we propose an analytical drain-current model for long-channel junctionless (JL) cylindrical surrounding-gate MOSFET (SRG MOSFET). It is based on surface-potential solutions obtained from Poisson’s equation using some approximations and separate conditions. Furthermore, analytical compact expressions of the drain-current have been derived for deep depletion, partial depletion, and accumulation mode. The confrontation of the model with TCAD simulation results, performed with Silvaco Software, proves the validity and the accuracy of the developed model
Microelectronics Journal, 2001
The present analysis proposes a 2D analytical model of SGT/CGT MOSFET for potential distribution, short channel threshold voltage and current voltage characteristics. The model takes into account the effect of source/drain resistance, ®eld-dependent mobility, velocity saturation and drain-induced barrier lowering (DIBL) effect. Advantages of SGT/CGT MOSFET over conventional planar structures are analyzed in detail and the results obtained are veri®ed with simulated data. q where q is the electron charge, N a the silicon ®lm doping and 1 Si the dielectric permittivity of silicon.
Modeling of Built-In Potential Variations of Cylindrical Surrounding Gate (CSG) MOSFETs
International Journal of VLSI Design & Communication Systems, 2012
Due to aggressive scaling of MOSFETs the parasitic fringing field plays a major role in deciding its characteristics. These fringing fields are now not negligible and should be taken into account for deriving the MOSFET models. Due to this fringing field effect there are some charges induced in the source/drain extension regions which will change the potential barrier at the source-channel from its theoretical nominal values. In this paper an attempt has been made to model variation of built-in potential variation for a cylindrical surrounding gate MOSFET. The model has been verified to be working in good agreement with the variations of gate length and channel radius.
Microelectronics Journal, 2016
The scaling of the solid-state devices are reaching its limit and it enhances the significant short channel effects. To overcome these problems, the surrounding-gate MOSFET is emerging as a promising structure and is a replacement of traditional MOSFETs. In this research work, authors have analyzed the performance of various parameters for the cylindrical surrounding-gate MOSFET using surface potential based approach and further transformation of variable technique to find the solution of the same differential equation. However, the modeling of terminal charge and trans-capacitance are also presented which is used for the circuit simulation. The influence of Gaussian doping (in vertical direction across the radius of the device) has been analyzed and solution of the surface-potential is derived based on the taylor series expansion.
Journal of Applied Physics, 2011
In this paper we extend a compact surrounding-gate MOSFET model to include the hydrodynamic transport and quantum mechanical effects, and we show that it can reproduce the results of 3D numerical simulations using advanced transport models. A template device representative for the cylindrical surrounding-gate MOSFET was used to validate the model. The final compact model includes mobility degradation, drain-induced barrier lowering, velocity overshoot, and quantum effects. Comparison between the compact model and the advanced transport modeling approaches shows good agreement within the practical range of drain voltages.
Microelectronics Reliability, 2012
The paper presents a simulation study of Nanoscale Cylindrical Surrounding Gate (SRG) MOSFET with localised interface charges. The objective of the present work is to study the performance degradation due to hot carrier induced/radiation induced/stress induced damage in the form of localised/fixed charges at the semiconductor/oxide interface of the device. Impact of fixed charges has been studied on the characteristics such as drain current, transconductance and its higher order terms, device efficiency and linearity FOMs. Effect of nature and extension of interface fixed charges has been discussed in detail through extensive simulation. Circuit reliability issues of the device are discussed in terms of DC bias point degradation.
An explicit solution for long-channel surrounding-gate (SRG) MOSFETs is presented from intrinsic to heavily doped body including the effects of interface traps and quantum effects. The solution is based on the core SRGMOSFETs model of Unified Charge Control Model (UCCM) for heavily doped condition. The UCCM model of highly doped SRGMOSFETs is derived to obtain the exact equivalent expression as in undoped case. Taking the advantage of the undoped explicit charge-based expression, the asymptotic limits for below threshold and above threshold have been redefined to include the effect of trap states for heavily doped case. After solving the asymptotic limits, an explicit mobile charge expression is obtained which include the trap state effects. The explicit mobile charge model shows very good agreement with respect to numerical simulation over practical terminal voltages, doping concentration, geometry effects, and trap state effects due to the fixed oxide charges and interface traps. Then, the drain current is obtained using the Pao–Sah's dual integral, which is expressed as a function of inversion charge densities at the source/drain ends. The drain current agreed well with implicit solution and numerical simulation for all regions of operation without employing any empirical parameters. In addition, the quantum effects are included based on quantum corrected model. The threshold voltage shift due to quantum confinement is incorporated to the classical model and the effective gate capacitance is recalculated due to series connected quantum capacitance. Comparison with previous explicit model has been conducted to verify the competency of the proposed model with doping concentration of 1 × 10 19 cm −3 as the proposed model has better advantages in terms of its simplicity and accuracy at higher doping concentration.
—A charge-based compact model of the long-channel cylindrical surrounding-floating gate (S-FG) MOSFETs for memory cell application is presented. The compact model is based on an accurate extraction of floating gate potential using charge balance model and solving the mobile charge density at the source and drain ends using the unified charge control model (UCCM). The drain-current relation is obtained from Pao-Sah's dual integral, which is expressed as a function of inversion charge at the source and drain end. The compact model for the floating gate potential and its transfer characteristics have been extensively verified with numerical simulations at various bias potentials and floating gate charges in all operating regions.