亚100 nm应变Si/SiGe nMOSFET阈值电压二维解析模型

本文基于二维泊松方程,建立了适用于亚100 nm应变Si/SiGe nMOSFET的阈值电压理论模型.为了保证该模型的准确性,同时考虑了器件尺寸减小所导致的物理效应,如短沟道效应,量子化效应等.通过将模型的计算结果与二维器件模拟器ISE的仿真结果进行对比分析,证明了本文提出的模型的正确性.最后,还讨论了亚100 nm器件中常规工艺对阈值电压的影响.该模型为亚100 nm小尺寸应变Si器件的分析设计提供了一定的参考. 关键词： 亚100nm 应变Si/SiGe nMOSFET 二维表面势 阈值电压     

The effect of substrate doping on the flatband and threshold voltages of a strained-Si pMOSFET

The effect of substrate doping on the flatband and threshold voltages of a strained-Si/SiGe p metal-oxide semiconductor field-effect transistor(pMOSFET) has been studied.By physically deriving the models of the flatband and threshold voltages,which have been validated by numerical simulation and experimental data,the shift in the plateau from the inversion region to the accumulation region as the substrate doping increases has been explained.The proposed model can provide a valuable reference to the designers of strained-Si devices and has been implemented in software for extracting the parameters of a strained-Si MOSFET.     

Effect of substrate doping on the flatband and threshold voltages of strained-Si pMOSFET

The effect of substrate doping on the flatband and threshold voltages of strained-Si/SiGe p metal-oxide semiconductor field-effect transistor (pMOSFET) has been studied. By physically deriving the models of the flatband and threshold voltages, which have been validated by numerical simulation and experimental data, the shift in the plateau from the inversion region to the accumulation region as the substrate doping increases has been explained. The proposed model can provide valuable reference to the designers of strained-Si devices and has been implemented in software for extracting the parameters of strained-Si MOSFET.     

Short channel effect improved strained-Si:C-source/drain PMOSFETs

The suppression of short channel effect in strained-Si surface channel PMOSFET with carbon incorporation on relaxed SiGe buffers is demonstrated. The lateral diffusion of boron from source/drain into the channels is retarded by a reduction of interstitial formation due to carbon incorporation in the strained-Si layer. It is necessary to avoid the high temperature (>900 °C) process for SiC precipitations as trap centers which are observed by atomic force microscope and X-ray diffraction. An incorporated carbon in the source/drain is not only being stressor but also improves short channel effect for extremely shallow junctions, and makes it possible to have high speed devices.     

应变Si NMOS积累区电容特性研究

积累区MOS电容线性度高且不受频率限制, 具有反型区MOS电容不可比拟的优势. 本文在研究应变Si NMOS电容C-V特性中台阶效应形成机理的基础上, 通过求解电荷分布, 建立了应变Si/SiGe NMOS积累区电容模型, 并与实验结果进行了对比, 验证了模型的正确性. 最后, 基于该模型, 研究了锗组分、应变层厚度、掺杂浓度等参数对台阶效应的影响, 为应变Si器件的制造提供了重要的指导作用. 本模型已成功用于硅基应变器件模型参数提取软件中, 为器件仿真奠定了理论基础. 关键词： 应变Si NMOS 积累区电容 台阶效应 电荷分布     

Growth of High Quality Strained-Si on Ultra-Thin SiGe-on-Insulator Substrate

Ultra-thin and near-fully relaxed SiCe substrate is fabricated using a modified Ce condensation technique, and then a 25-nm-thiek biaxially tensile strained-Si with a low rms roughness is epitaxially deposited on a SiGe- on-Insulator （SGOI） substrate by ultra high vacuum chemical vapor deposition （UHVCVD）. High-Resolution cross-sectional transmission electron microscope （HR-XTEM） observations reveal that the strained-Si/SiGe layer is dislocation-free and the atoms at the interface are well aligned. Furthermore, secondary ion mass spectrometry （SIMS） results show a sharp interface between layers and a uniform distribution of Ge in the SiCe layer. One percent in-plane tensile strain in the strained-Si layer is confirmed by ultraviolet （UV） Raman spectra, and the stress maintained even after a 30-s rapid thermal annealing （RTA） process at 1000℃. According to those results, devices based on strained-Si are expected to have a better performance than the conventional ones.     

Strained-Si with carbon incorporation for MOSFET source/drain engineering

The carbon incorporation in strained-Si source/drain of MOSFET is demonstrated. The methylsilane (CH₃SiH₃) is chosen as the carbon precursor to make high percentage of substitutional carbon, and less defects by interstitials and vacancies. The large D_it at oxide/strained-Si:C interface degrades the expected carrier mobility enhancement, but improvement is observed after forming gas annealing. The strained-Si source/drain with carbon incorporation is not only being stressor but also lower R_s, and make a potential candidate for future high-speed ballistic devices beyond 10 nm technology node.     

Two-dimensional models of threshold voltage and subthreshold current for symmetrical double-material double-gate strained Si MOSFETs

The two-dimensional models for symmetrical double-material double-gate(DM-DG) strained Si(s-Si) metal–oxide semiconductor field effect transistors(MOSFETs) are presented. The surface potential and the surface electric field expressions have been obtained by solving Poisson's equation. The models of threshold voltage and subthreshold current are obtained based on the surface potential expression. The surface potential and the surface electric field are compared with those of single-material double-gate(SM-DG) MOSFETs. The effects of different device parameters on the threshold voltage and the subthreshold current are demonstrated. The analytical models give deep insight into the device parameters design. The analytical results obtained from the proposed models show good matching with the simulation results using DESSIS.     

Exactly solvable models: The road towards a rigorous treatment of phase transitions in finite systems

The exact analytical solutions of a variety of statistical models recently obtained for finite systems are thoroughly discussed. Among them are a constrained version of the statistical multifragmentation model, the Gas of Bags Model, and the Hills and Dales Model of surface partition. The finite volume analytical solutions of these models were obtained by a novel powerful mathematical method, the Laplace-Fourier transform. Thus, the Laplace-Fourier transform allows one to study the nuclear matter equation of state, the equation of state of hadronic matter and quark gluon plasma, and the surface entropy of large clusters on the same footing. A complete analysis of the isobaric partition singularities of these models is done for finite systems. The developed formalism allows us, for the first time, to exactly define the finite volume analogs of gaseous, liquid, and mixed phases of these models from the first principles of statistical mechanics, and to demonstrate the pitfalls of earlier works. The found solutions may be used for building up a new theoretical apparatus to rigorously study phase transitions in finite systems. The strategic directions of future research opened by these exact results are also discussed. The text was submitted by the author in English.     

应变Si NMOSFET阈值电压集约物理模型

本文采用渐变沟道近似和准二维分析的方法, 通过求解泊松方程, 建立了应变Si NMOSFET阈值电压集约物理模型. 模型同时研究了短沟道, 窄沟道, 非均匀掺杂, 漏致势垒降低等物理效应对阈值电压的影响. 采用参数提取软件提取了阈值电压相关参数, 通过将模型的计算结果和实验结果进行对比分析, 验证了本文提出的模型的正确性. 该模型为应变Si超大规模集成电路的分析和设计提供了重要的参考. 关键词： 应变Si NMOSFET 阈值电压 集约物理模型     

Hydrodynamical model for bulk and surface plasmons in cylindrical wires

In this paper, we study the electrostatic surface and volume modes of a cylindrical wire using the hydrodynamical model of plasmon excitation, which allows an analytical study of dispersion effects. We solve the hydrodynamical equations for a cylindrical wire geometry, obtaining new analytical expressions for the bulk and surface modes. New dispersion relations are obtained for each type of mode and numerical solutions are given. We analyze in detail the characteristics of the solutions and their differences with previous treatments based on non-dispersive models. These differences become important for wires of small radii, particularly in the range of few nanometers.     

Analytical models of lateral power devices with arbitrary vertical doping profiles in the drift region

By solving the 2D Poisson's equation, analytical models are proposed to calculate the surface potential and electric field distributions of lateral power devices with arbitrary vertical doping profiles. The vertical and the lateral breakdown voltages are formulized to quantify the breakdown characteristic in completely-depleted and partially-depleted cases. A new reduced surface field (RESURF) criterion which can be used in various drift doping profiles is further derived for obtaining the optimal trade-off between the breakdown voltage and the on-resistance. Based on these models and the numerical simulation, the electric field modulation mechanism and the breakdown characteristics of lateral power devices are investigated in detail for the uniform, linear, Gaussian, and some discrete doping profiles along the vertical direction in the drift region. Then, the mentioned vertical doping profiles of these devices with the same geometric parameters are optimized, and the results show that the optimal breakdown voltages and the effective drift doping concentrations of these devices are identical, which are equal to those of the uniform-doped device, respectively. The analytical results of these proposed models are in good agreement with the numerical results and the previous experimental results, confirming the validity of the models presented here.     

应变Si/Si1-xGex n型金属氧化物半导体场效应晶体管反型层中的电子迁移率模型

为了描述生长在弛豫Si_1-xGe_x层上应变Si n型金属氧化物半导体场效应晶体管(nMOSFETs)反型层中电子迁移率的增强机理,提出了一种新型的、基于物理的电子迁移率模型.该模型不仅能够反映声学声子散射迁移率、表面粗糙度散射迁移率与垂直于半导体-绝缘体界面的电场强度之间的依赖关系,而且也能解释不同的锗组分对两种散射机理的抑制情况从而引起电子迁移率增强的机理.该模型数学表达式简单,可以模拟任意锗组分下的迁移率.通过数值分析验证得出,该 关键词： 应变Si/SiGe 电子迁移率 反型层 模型     

Performance and analytical modelling of halo-doped surrounding gate MOSFETs

Halo structure is added to sub-100 nm surrounding-gate metal-oxide-semiconductor fieldeffect-transistors （MOS- FETs） to suppress short channel effect. This paper develops the analytical surface potential and threshold voltage models based on the solution of Poisson＇s equation in fully depleted condition for symmetric halo-doped cylindrical surrounding gate MOSFETs. The performance of the halo-doped device is studied and the validity of the analytical models is verified by comparing the analytical results with the simulated data by three dimensional numerical device simulator Davinci. It shows that the halo doping profile exhibits better performance in suppressing threshold voltage roll-off and drain-induced barrier lowering, and increasing carrier transport efficiency. The derived analytical models are in good agreement with Davinci.     

混合电解质溶液中考虑介电饱和度的表面电位评估原理

基于非线性泊松-玻尔兹曼方程，推导了混合电解质溶液中考虑介电饱和度的表面电位的解析表达式. 近似解析解和精确数值解计算出的表面电位在很大范围的电荷密度和离子强度条件下均具有很好的一致性. 当表面电荷密度大于0.30 C/m^{2 时，介电饱和度对表面电位的影响变得尤为重要；当表面电荷密度小于0.30 C/m2时，可忽略介电饱和度的影响，即基于经典泊松-玻尔兹曼方程可获得有效的表面电位解析模型. 因此，0.3 C/m2可作为是否考虑介电饱和度的颗粒临界表面电荷密度值. 在低表面电荷密度时，考虑介质饱和度的表面电位解析模型可自然回归到经典泊松-玻尔兹曼理论的结果，得到的表面电位可以正确地预测一价和二价反离子之间的吸附选择性.}     

非对称HALO掺杂栅交叠轻掺杂漏围栅MOSFET的解析模型

为抑制短沟道效应和热载流子效应, 提出了一种非对称HALO掺杂栅交叠轻掺杂漏围栅MOSFET新结构. 通过在圆柱坐标系中精确求解三段连续的泊松方程, 推导出新结构的沟道静电势、阈值电压以及亚阈值电流的解析模型. 结果表明, 新结构可有效抑制短沟道效应和热载流子效应, 并具有较小的关态电流. 此外, 分析还表明栅交叠区的掺杂浓度对器件的亚阈值电流几乎没有影响, 而栅电极功函数对亚阈值电流的影响较大. 解析模型结果和三维数值仿真工具ISE所得结果高度符合.     

Dual-Material Surrounding-Gate Metal-Oxide-Semiconductor Field Effect Transistors with Asymmetric Halo

Asymmetrical halo and dual-material gate structure are used in the sub-100 nm surrounding-gate metal oxidesemiconductor field effect transistor （MOSFET） to improve the performance. Using three-region parabolic potential distribution and universal boundary condition, analytical surface potential and threshold voltage models of the novel MOSFET are developed based on the solution of Poisson＇s equation. The performance of the MOS- FET is examined by the analytical models and the 3D numerical device simulator Davinci. It is shown that the novel MOSFET can suppress short channel effect and improve carrier transport efficiency. The derived analytical models agree well with Davinci.     

Unsteady analytical solutions of the spherical shallow water equations

A new class of unsteady analytical solutions of the spherical shallow water equations (SSWE) is presented. Analytical solutions of the SSWE are fundamental for the validation of barotropic atmospheric models. To date, only steady-state analytical solutions are known from the literature. The unsteady analytical solutions of the SSWE are derived by applying the transformation method to the transition from a fixed cartesian to a rotating coordinate system. Fundamental examples of the new unsteady analytical solutions are presented for specific wind profiles. With the presented unsteady analytical solutions one can provide a measure of the numerical convergence in the case of a temporally evolving system. An application to the atmospheric model PLASMA shows the benefit of unsteady analytical solutions for the quantification of convergence properties.     

Analytical modeling and simulation of subthreshold characteristics of back-gated SSGOI and SSOI MOSFETs: A comparative study

The Silicon–Germanium-on-Insulator (SGOI) and Silicon-on-Insulator (SOI) based MOS structures are spearheading the strained-Si technology. The present work compares the subthreshold characteristics of two short-channel back-gated (BG) strained-Si-on-SGOI (SSGOI) and BG strained-Si-on-Insulator (SSOI) MOSFETs, and provides some solutions to overcome the degradation in subthreshold characteristics with the unrelenting downscaling of the devices. Subthreshold behaviors of the MOS structures are based on surface potential model which is determined by solving the 2D Poisson's equation with suitable boundary conditions by evanescent mode analysis for both of the MOS structures. The closed form expressions for threshold voltage, subthreshold current and subthreshold swing have been derived for symmetrical as well as independent gate operation (IGO). In addition, the Electrostatic integrity (EI) factors for SSOI and SSGOI MOS structures have been estimated and compared with Double-Gate (DG) MOSFET. The numerical simulation results, obtained by ATLAS?, a 2D device simulator from Silvaco, have been used to assess the validity of the models.     

转动圆柱和圆锥的激光距离多普勒像分析模型

提出了一个新的转动圆柱和圆锥的激光距离多普勒像分析模型.该模型能分析圆柱和圆锥的几何参量、表面材料、姿态和脉冲宽度对这两种目标的距离多普勒像的影响,并能退化到平面波下的圆柱和圆锥的多普勒谱分析模型.数值分析了几何参量、表面材料、姿态和脉冲宽度对距离多普勒像的影响.理论和测量相结合,这个分析模型能用来进行圆柱和圆锥参量的识别.这个分析模型的解析表达式对于多普勒速度计和激光雷达应用有着重要的意义. 关键词： 光散射 双向反射分布函数 距离多普勒 目标识别