Wangzuo Shangguan

Surface-Potential Solution for Generic Undoped MOSFETs With Two Gates

We present a rigorously derived analytical Poisson solution for undoped semiconductors and apply the general solution to generic MOSFETs with two gates, unifying different types such as silicon-on-insulator (SOI) and symmetric and asymmetric double gate (s-DG and a-DG) structures. The Newton-Raphson method is used to solve surface-potential equations resulting from the application of boundary conditions to the general Poisson solution, with an initial guess that is very close to the exact solution. The universal initial guess can be used as an approximate explicit solution for fast evaluation, while the iterative solution can be used for benchmark tests. The results demonstrate the unification of surface-potential solutions having an accuracy of 10-15 V for SOI, a-DG, and s-DG MOSFETs, which are achieved within two to six iterations. Furthermore, the explicit solution yields less than 3.5% error for back-to-front-gate oxide thickness ratios larger than 25

Single-piece polycrystalline silicon accumulation/depletion/inversion model with implicit/explicit surface-potential solutions

A single-piece analytical equation for the surface potential at the polycrystalline-silicon (poly-Si) gate of a metal-oxide-semiconductor field-effect transistor is presented, which accounts for the poly-accumulation, poly-depletion, and poly-inversion effects. It is shown that the model accurately describes the physical behavior of the surface potentials, gate charge, and capacitance, with smooth transitions, which has been verified with iterative, explicit, and numerical solutions. The proposed model can be used in implicit or explicit surface-potential-based formulations.

Extraction of physical parameters of strained silicon MOSFETs from C-V measurement

This paper presents a methodology for extraction of the physical parameters of strained-silicon MOSFET from one capacitance-voltage (C-V) measurement based on physics-based compact model and conventional C-V characterization techniques. The extracted physical parameters (such as strained-silicon layer thickness and doping as well as conduction band offset) are used to create a numerical (Medici) device structure, from which the simulated C-V data is compared with the measured data as well as that from the compact model (Xsim), which validates the extraction technique. The proposed approach provides a simple yet physical means to probe into strained-silicon MOSFFET structures useful for characterize and model these devices, which are emerged as promising candidates for the enhancement and extension to conventional bulk-Si CMOS technology.

Compact gate-current model based on transfer-matrix method

We present a compact gate-current model based on the scattering matrix method for metal-oxide-semiconductor devices. The analytical integration of the tunneling current over the incident energy is simplified by making use of the single tunneling energy approximation, and the model error is further reduced by introducing different effective conduction band edges for the supply function and for the transmission coefficient function. Results calculated by the proposed model agree with the experimental data with satisfactory accuracy.

General analytical poisson solution for undoped generic two-gated metal-oxide-semiconductor field-effect transistors

We present a general analytical solution to the Poisson equation for undoped semi-conductors. This general Poisson solution is then applied to generic dual-gate metal-oxide- semiconductor field-effect transistors (MOSFETs), unifying different types including silicon-on-insulator, and symmetric and asymmetric double-gate MOSFETs. Newton-Raphson (NR) algorithm is called to solve the resulting surface-potential equation. An exact solution is proposed making the NR algorithm computationally very efficient. While the universal initial guess can be used as an approximate solution for fast evaluation, the iterative results by NR algorithm are useful for benchmark tests.

Effect of surface bond-order loss on the dc conductance of a metallic nanosolid

With the miniaturization of a solid device, quantum and interface effects become dominant not only in the static properties but also in the transport dynamics in the solid. Here we examine the dc conductance of a nanosolid by introducing the depression of the intra-atomic trapping potential in the surface skin [Sun, Phys. Rev. B 69, 045105 (2004)] as a perturbation to the conventional “quantum well” for tunneling electrons. It is derived that downshifts of the dc conductance peaks (that is, the incident energies for resonant tunneling) happens in an oscillatory way, depending on the strength of the perturbation. Besides, the downshifts of the peak positions due to the trapping potential well depression decrease as the size of the nanosolid is increased.

Effect of surface bond-order loss on the electronic thermal conductivity of metallic polycrystalline films

The effect of surface bond-order loss on the electronic thermal conductivity of metallic polycrystalline films is examined using Boltzmann transport theory. A modification of the grain boundary potential barrier has been made by adding depressed potential wells of intra-atomic trapping [C. Q. Sun, Phys. Rev. B 69, 045105 (2004)] to both sides of the grain boundaries. Electron scattering by film surfaces is also considered to follow the line of Fuchs’ convention. Results show that the thermal conductivity of the films is sensitive to the film thickness, mean grain size, and Fermi energy. In particular, thermal conductivity increases significantly with the depth of the atomic trapping due to the bond-order loss induced surface bond contraction and associated bond strength gain.

Xsim: unified regional approach to compact modeling for next generation CMOS

This paper describes the approaches in the development of Xsim, a unified regional threshold-voltage-based model for deep-submicron MOSFETs. In comparison to popular surface-potential-based models, our approach has the advantages of correlation to technology data, minimum data and one-iteration extraction, single-piece charge models from accumulation to strong inversion with extendibilily to poly-depletion and strained-Si, as well as selectable accuracy with the same parameter set.