Compact model for short and ultra thin symmetric double gate

Abstract

In this paper we propose a new model based on an analytical model for undoped symmetric double gate MOSFETs introduced by Chenming Hu et al. The proposed model targets to include the quantum confinement and the most important short channel effects. The new model results were compared with a device simulator results to validate the proposed modifications. The proposed model introduces low fitting error reaches t01 % for ultra thin and short channel double gate transistors.index terms-Compact model, double gate, short channel effects, quantum confinement

Analytical Compact Model for Lightly Doped Nanoscale Ultrathin-Body and Box SOI MOSFETs With Back-Gate Control

“…Based on the drift-diffusion transport, the drain current at any point y in the channel is given by [14] I ds = W μC oxf V th q i dV y dy (10) where μ is the electron mobility, W is the gate width, and L is the gate length. With including the carrier saturation velocity effect, the mobility can be approximated as follows [26]:…”

“…We note that (17) constitutes the basic structure of compact drain-current models like Berkeley Short-channel IGFET Model (BSIM) [26], [28]. The effective mobility μ eff degradation due to the vertical gate field is expressed in terms of the charge at the source side q s as [29] μ eff = μ o 1 + θ 1 V th q s + θ 2 (V th q s ) 2 (18) where μ o is the low-field mobility, and θ 1 and θ 2 are the mobility attenuation factors of the first and second order, which can be extracted from the experimental data at low drain voltage using a modified Y-function method [30].…”

“…Due to this splitting, the lowest energy band rises and the carriers need more energy to occupy it, resulting in an increase in the threshold voltage. For compact modeling, the quantum confinement effect has been considered in the model with decreasing the semiconductor work function ϕ s by the minimum energy of the lowest conduction subband to a new work function φ snew [26]. Thus, the shift in V tf due to quantum confinement is included in the model considering the work function difference as [26] φ = φ m − φ snew (23) where φ m is the gate metal work function.…”

“…For compact modeling, the quantum confinement effect has been considered in the model with decreasing the semiconductor work function ϕ s by the minimum energy of the lowest conduction subband to a new work function φ snew [26]. Thus, the shift in V tf due to quantum confinement is included in the model considering the work function difference as [26] φ = φ m − φ snew (23) where φ m is the gate metal work function. The shift in the threshold voltage due to the quantum confinement is V tf = 0.085 + 2.178/t 2 Si proposed in Berkeley Short-channel IGFET Model-Independent Multi-Gate [14], where t Si is expressed in nanometer.…”

“…The shift in the threshold voltage due to the quantum confinement is V tf = 0.085 + 2.178/t 2 Si proposed in Berkeley Short-channel IGFET Model-Independent Multi-Gate [14], where t Si is expressed in nanometer. Thus, for t Si = 7 nm, the contribution of quantum confinement in φ is ∼0.129 V. The application of compact models in ultrathin symmetric common DG and asymmetricindependent DG MOSFETs demonstrates that the threshold voltage shift due to structural confinement is sufficient to predict, with good accuracy, the current-voltage characteristics, without considering the quantum degradation of the gate capacitance [14], [26].…”