Subthreshold Behavior Model Research Articles

A New Effective-Conducting-Path-Driven Subthreshold Behavior Model for Junctionless Dual-Material Omega-Gate Nano-MOSFETs

In this paper, a generalized analytical subthreshold behavior model for junctionless omega-gate (JLΩG) MOSFETs combining dual-material gate (DMG) is built. Through the effective conducting path effects (ECPEs), we propose a new concept of off-center ratio (δ) dominating the effective scaling length to derive our model based on the effective conducting central potential (Φ eff,C ), obtained by quasi-3D potential method. It provides a more accurate expression of scaling equation for JLΩGFETs and leads to an improved subthreshold behavior prediction. Accounting for these renewed potential and current models, we utilize dual materials to achieve better immunity to short channel effects. The proposed modeling can be extensively applied to other multiple-gate (MG) nano-transistors as well.

A Quasi-3-D Scaling Length Model for Trapezoidal FinFET and Its Application to Subthreshold Behavior Analysis

Based on the equivalent channel width and equivalent number of gates, a quasi-3-D scaling length model for the trapezoidal FinFET (TzFinFET) is developed. By accounting for the coupling effects between equivalent double-gate FET and single-gate FET, the scaling length of TzFinFET can be accurately predicted. Besides Fin height, top Fin width, and gate oxide, the scaling length is also sensitive to the inclination angle induced by the process technology. By applying this derived scaling length to the TzFinFET, the subthreshold behavior model including threshold voltage and subthreshold swing can be achieved. Both threshold voltage roll-off and subthreshold swing roll-up can be well controlled by the scaling factor in accordance with the scaling theory. According to the scaling factor, the acceptable minimum channel length that allows the maximum subthreshold degradation can be uniquely determined. The variability of subthreshold characteristics with the process parameter is also taken into account in this paper.

A New Short-Channel-Effect-Degraded Subthrehold Behavior Model for Double-Fin Multi-Channel FETs (DFMcFETs)

On the basis of the quasi-three-dimensional scaling equation and minimum bottom-central potential, a new short-channel-effect-degraded subthreshold behavior model for double-Fin multichannel FET (DFMcFET) is presented. It is shown that the deep trench of the DFMcFET is superior to the shallow one in respect of suppressing short-channel effects (SCEs) and reducing the threshold voltage roll-off and subthreshold roll-up. Meanwhile, the wide trench and thin gate oxide are required to resist SCEs and reduce the subthreshold behavior degradation as the channel length is further decreased. In comparison to the counterpart of conventional FinFET, DFMcFET not only provides the more conducting channel, but also enhances the immunity to SCEs due to its shorter scaling length. Besides, both threshold voltage roll-off Δ V TH and subthreshold swing roll-up ΔSS can be well controlled by the scaling theory. The allowable minimum channel length can be uniquely determined according to the criterion of the scaling factor. With its computational efficiency and simple form, the model can be easily used for the circuit application of the DFMcFET.

Erratum to: A new two-dimensional analytical subthreshold behavior model for submicron Triple Material Gate (TM) GaN MESFET

Erratum to: A new two-dimensional analytical subthreshold behavior model for submicron Triple Material Gate (TM) GaN MESFET

A new two-dimensional analytical subthreshold behavior model for submicron Triple Material Gate (TM) GaN MESFET

A new two-dimensional (2D) analytical model for a Triple Material Gate (TM) GaN MESFET has been proposed and modeled to suppress the short channel effects and improve the subthreshold behavior. The analytical model is based on a two-dimensional analysis of the channel potential, threshold voltage and subthreshold swing factor for TM GaN MESFET is developed. The aim of this work is to demonstrate the improved subthreshold electrical performances exhibited by TM GaN MESFET over dual material gate and conventional single material gate MESFET. The results so obtained are verified and validated by the good agreement found with the 2D numerical simulations using the ATLAS device simulation software. The models developed in this paper will be very helpful to understand the device behavior in subthreshold regime for future circuit applications.

A two-dimensional analytical subthreshold behavior model for junctionless dual-material cylindrical surrounding-gate MOSFETs

A two-dimensional analytical subthreshold behavior model for junctionless dual-material cylindrical surrounding-gate (JLDMCSG) metal-oxide-semiconductor field-effect transistors (MOSFETs) is proposed. It is derived by solving the two-dimensional Poisson's equation in two continuous cylindrical regions with any simplifying assumption. Using this analytical model, the subthreshold characteristics of JLDMCSG MOSFETs are investigated in terms of channel electrostatic potential, horizontal electric field, and subthreshold current. Compared to junctionless single-material cylindrical surrounding-gate MOSFETs, JLDMCSG MOSFETs can effectively suppress short-channel effects and simultaneously improve carrier transport efficiency. It is found that the subthreshold current of JLDMCSG MOSFETs can be significantly reduced by adopting both a thin oxide and thin silicon channel. The accuracy of the analytical model is verified by its good agreement with the three-dimensional numerical simulator ISE TCAD.

A 2D Transconductance and Sub-threshold behavior model for triple material surrounding gate (TMSG) MOSFETs

A 2D analytical model for transconductance, Sub-threshold current and Sub-threshold swing for Triple Material Surrounding Gate MOSFET (TMSG) is presented in this paper. Based on the solution of two dimensional Poisson equation, the physics based model of sub-threshold current of the device is derived. The model also includes the effect of gate oxide thickness and silicon thickness on the sub-threshold swing characteristics. Transconductance to drain current ratio of the triple material surrounding gate is calculated since it is a better criterion to access the performance of the device. The effectiveness of TMSG design was scrutinized by comparing with other triple material and dual material gate structures. Moreover the effect of technology parameter variations is also studied and proposed. This proposed model offers basic guidance for design of TMSG MOSFETs. The results of the analytical model are compared with the MEDICI simulation results thus providing validity of the proposed model.

An analytical two dimensional subthreshold behavior model to study the nanoscale GCGS DG Si MOSFET including interfacial trap effects

In order to pursue the miniaturization process as predicted by Moor’s law and go beyond actual reached lengths, more condensed efforts should be focused not only on looking for higher mobility materials but also on improving existing topologies of nanocircuit digital devices, which are the corner stone of currently used information storage supports. Therefore, the aim of this paper is to provide a quantitative analysis about the efficiency of our proposed structure Graded Channel Gate Stack Double Gate on Si MOSFET (GCGS DG Si MOSFET) in remedying the short channel and hot carrier degradation effects. The analysis is carried out by using an analytical 2-D subthreshold behavior model consolidated with numerical simulations (SILVACO), where the proposed structure shows an improvement and immunity against the hot carriers in terms of threshold voltage and swing factor. Moreover, the developed analytical models including the device immunity effect are compared with those of the conventional DG MOSFET, where a significant enhanced performance is predicted for the case of our proposed design. Consequently, it can be reasonably claimed that the (GCGS) DG Si MOSFET structure can alleviate the short channel and hot carrier degradation effects and further improves the device reliability for the nanoelectronic digital applications.

A new two-dimensional subthreshold behavior model for the short-channel asymmetrical dual-material double-gate (ADMDG) MOSFET’s

Based on the exact solution of two-dimensional Poisson’s equation, a novel subthreshold behavior model comprising channel potential, subthreshold swing, and threshold voltage for the short-channel asymmetrical dual-material double-gate (ADMDG) MOSFET’s have been developed. The model is verified by its simulation results that agree well with those of the two-dimensional numerical simulator. Besides offering the physical insight into device physics, the model provides the basic designing guidance for the ADMDG MOSFET’s.

A new compact subthreshold behavior model for dual-material surrounding gate (DMSG) MOSFETs

On the basis of exact resultant solution of two-dimensional Poisson equation, a new compact subthreshold behavior model comprising two-dimensional potential, threshold voltage, subthreshold current and subthreshold swing for the dual-material surrounding gate (DMSG) MOSFETs is successfully developed. The model shows its validity by a good agreement with the simulated results from published device simulation software MEDICI. Besides offering the physical insight into device physics, the model provides the basic designing guidance for the DMSG MOSFETs.

A new two-dimensional analytical subthreshold behavior model for short-channel tri-material gate-stack SOI MOSFET’s

On the basis of the exact solution of the two-dimensional Poisson equation, a new analytical subthreshold behavior model consisting of the two-dimensional potential, threshold voltage, and subthreshold current for the short-channel tri-material gate-stack SOI MOSFET’s is developed. The model is verified by its good agreement with the numerical simulation of the device simulator MEDICI. The model not only offers physical insight into the device physics but also provides guidance for the basic design of the device.

A New Analytical Subthreshold Behavior Model for Single-Halo, Dual-Material Gate Silicon-on-Insulator Metal Oxide Semiconductor Field Effect Transistor

On the basis of the exact solution of the two-dimensional Poisson equation, a new analytical subthreshold behavior model consisting of the two-dimensional potential, threshold voltage, and subthreshold current for the single-halo, dual-material gate (SHDMG) silicon-on-insulator (SOI) metal oxide semiconductor field effect transistor (MOSFET) is developed. The model is verified by the good agreement with a numerical simulation using the device simulator MEDICI. The model not only offers a physical insight into device physics but is also an efficient device model for the circuit simulation.

A two-dimensional analytical subthreshold behavior model for short-channel AlGaAs/GaAs HFETs

Based on the minimum heteroface potential through an evanescent-mode analysis of two-dimensional potential distribution, the comprehensive and accurate expressions for the short-channel threshold voltage and subthreshold swing for self-aligned gated AlGaAs/GaAs HFETs are developed. It is found that the 2-D electron gas is strongly affected by the DIBL effect which will significantly influence the subthreshold behavior of the AlGaAs/GaAs HFETs. Besides the doping density, the thickness of the spacer and doped body can aggressively affect the short-channel subthreshold behavior comprising threshold voltage shift and subthreshold swing degradation. This model not only gives physical insights into the short-channel effects in HFETs but also offers basic designing guideline for the small-geometry AlGaAs/GaAs HFETs.

An analytical (classical) subthreshold behavior model for symmetrical fully‐depleted SOI double‐gate MOSFET's

Two dimensional device‐physics‐based analytical models are developed for subthreshold behavior in fully‐depleted SOI double‐gate MOSFET's. An analytical solution of Poisson's 2‐D equation is employed to establish the design equation for the subthreshold behavior in the fully‐depleted SOI double‐gate MOSFET's. The concept of effective conducting path explains the silicon film thickness (tsi ), front and back oxide thickness (tox ) and doping density (NA ) unified dependence of subthreshold swing (S). Furthermore, along with the effective conducting path, the minimum channel potential is used to precisely predict the threshold voltage roll‐off of the SOI double‐gate MOSFET's. This analytical model not only gives physical insight into the fully‐depleted SOI double‐gate MOSFET's device physics, but also provides basic designing guidelines for fully‐depleted double‐gate MOSFET's.