Physical/electromagnetic analysis of multifinger MOSFETs with SB‐SP combined methods

The frequency‐domain spectral balance technique has been demonstrated to be a viable alternative to the mixed‐domain Harmonic Balance technique. It has already been applied to the space‐domain polynomial expansion of the physical quantities inside the semiconductor, for the solution of steady‐state nonlinear differential equations, for the physical analysis of high‐frequency semiconductor devices. In this article it is coupled to a commercial electromagnetic solver, for the combined physical and electromagnetic analysis of multifinger MOSFET devices in linear and nonlinear regime. This method allows a fast and effective CAD analysis both in DC and RF periodic regime for very high frequencies. A quasi‐2D hydrodynamic formulation is used for a 0.35 μm gate length with a total 30 μm periphery, three finger MOSFET device; results are compared with those of a standard physical time‐domain, a harmonic balance and a spectral balance analysis for comparison of numerical efficiency. Moreover, comparison of S‐parameters with a commercial CAD tool with a compact model for circuit analysis is also given. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010.     

The development of a comprehensive computer program for the study of solid–solid atomic interfaces

This paper describes the construction of a comprehensive computer program to model the structure of the silicon–silicon dioxide (Si–SiO₂) boundary layer of semiconductor devices by combining experimental data from an X-ray storage ring with graphical simulations on a multiprocessor distributed net (or a multiprocessor supercomputer). The term ‘comprehensive’ refers to the program's planned ability to incorporate all stages necessary to translate 2D X-ray spectra to the final 3D atomic image with little or no human intervention. If successful, our efforts will provide materials scientists, engineers, and manufacturers of integrated circuits with an additional tool for understanding interfacial chemistry and thereby suggest new ways to improve the chemical and electronic behavior of their devices.     

Guest Editors' Introduction: DFM Drives Changes in Design Flow

Design for manufacturability (DFM) has thus far been the focus of extensive study in the semiconductor industry. Although deep-submicron processes enable the manufacture of area-efficient, high-performance chips, navigating the nanometer landscape presents enormous manufacturability challenges.     

半导体器件动力模型的有限元法仿真与分析

该文采用有限元方法对动力模型进行了数值仿真。首先推导出模型方程，然后根据将要采用的数值方法提出了新的变量替换关系和无量纲化参数，再讨论了一般器件的边界条件，最后对具有亚微米级的GaAs MESFET进行了数值仿真，数值结果表明在一定的条件下，电子的流动具有跨音速特征。     

Current-based testing for deep-submicron VLSIs

Current-based testing for deep-submicron VLSIs is important because of transistor sensitivity to defects as technology scales. However, unabated increases in leakage current in CMOS devices can make this testing very difficult. This article offers several solutions to this challenging problem     

Evaluation of a nested-grid implementation for 3D finite-difference semi-implicit hydrodynamic models

This work evaluates the implementation of a nested Cartesian grid in a 3D semi-implicit hydrodynamic model with synthetic and real examples. The outer model provides all the values needed by the governing equations of the nesting (inner) subdomain at the boundary (including tangential velocities). A 3D flux relaxation scheme is applied to prevent mass and energy drift. The influence of tangential velocities in the solution is evaluated, showing a substantial reduction on the results' quality when they are considered negligible and lateral circulation exists. The inner/outer coupling implemented achieves a simulation time equal to the inner execution time and allows a transfer step equal to the inner time-step, removing time interpolation errors. This coupling makes feasible the 3D relaxation implemented. A dramatic improvement in memory requirements and simulation time is achieved, that allows the use of low-cost low-power consumption platforms in the simulations.     

基于非结构网格的Gas-Kinetic方法

为解决带有复杂几何边界条件的高速流体计算问题,提出基于非结构网格的Gas-Kinetic方法.对于二维非结构网格,以三角形网格作为计算单元,形成在该网格控制单元中物理量导数求解的新方法.通过物理量导数得到在控制体积元边界上的通量,然后用每个计算时间步中求出的边界通量和控制体积元中的物理量,求出下一计算时间步所需的新物理量,依次进行计算直到计算结果收敛为止.采用NACA0012翼型进行数值计算验证,结果表明该方法简单高效,适用于低速和高速流体的计算.     

Quantum hydrodynamic simulation of discrete-dopant fluctuated physical quantities in nanoscale FinFET

Impact of the discrete dopants on device performance is crucial in determining the behavior of nanoscale semiconductor devices. Atomistic quantum mechanical device simulation for studying the effect of discrete dopants on device's physical quantities is urgent. This work explores the physics of discrete-dopant-induced characteristic fluctuations in 16-nm fin-typed field effect transistor (FinFET) devices. Discrete dopants are statistically positioned in the three-dimensional channel region to examine associated carrier's characteristic, concurrently capturing “dopant concentration variation” and “dopant position fluctuation”. An experimentally validated quantum hydrodynamic device simulation was conducted to investigate the potential profile and threshold voltage fluctuations of the 16-nm FinFET. Results of this study provide further insight into the problem of fluctuation and the mechanism of immunity against fluctuation in 16-nm devices.     

Using a periodic square wave test signal to detect crosstalk faults

Built-in self test (BIST) scheme simplifies the detection of crosstalk faults in deep-submicron VLSI circuits in the boundary scan environment. The scheme tests for crosstalk faults with a periodic square wave test signal under applied random patterns generated by a linear feedback shift register (LFSR), which is transconfigured from the embedded circuit's boundary scan cells. The scheme simplifies test generation and test application while obviating the fault occurrence timing issue. Experimental results show that coverage for the induced-glitch type of crosstalk fault for large benchmark circuits can easily exceed 90%.     

基于集成众核的3D蒙特卡罗半导体器件模拟器

3D蒙特卡罗器件模拟计算量大,计算量随网格与粒子数增加而急剧增加。通过分析3D蒙卡模拟加速热点和进一步可并行性,研究有效电势方法的集成众核并行方案;研究粒子自由飞行、统计模拟信息、计算表面粗糙散射等热点并行方案,最终实现基于CPU/MIC的三级并行3D蒙特卡罗器件模拟软件。实验结果显示,三级并行比单级并行获得更好的性能;当提高模拟精度时,相比单级并行,三级并行蒙特卡罗模拟加速比增加。     

Normal vector and winding number in 2D digital images with their application for hole detection

Differentiating hole from component is an important issue in digital topology. In a recent paper, Lee, Poston, and Rosenfeld proposed a method to distinguish external and internal boundaries in 2D and 3D images relying on the property of normal vector and winding number. The method uses a smoothing function to replace digital lattice for calculating normal vector on image boundary. In this paper, we show that normal vector and winding number can be defined directly in 2D digital images and used for hole detection without resorting to any smoothing operation. We analyze first the discontinuity of Freeman codes of contour and prove its properties. We define then outward normal vector in 2D images and demonstrate also its discontinuity properties. The difficulty of counting the transition of normal vector in a given direction is analyzed and a solution is proposed. Based on the theoretic properties of edge code and normal vector, we propound the first algorithm to count the transitions of normal vector in a given direction, and consequently holes and external contours can be distinguished easily. We further define winding number directly in digital images, show its properties, and propose a second algorithm implementing the idea of winding number which is conceptually simpler and easier than the first one. A proof of correctness of our both algorithms is given and computation results are presented.     

Local absorbent boundary condition for non-linear hyperbolic problems with unknown Riemann invariants

Generally, in problems where the Riemann invariants (RI) are known (e.g. the flow in a shallow rectangular channel, the isentropic gas flow equations), the imposition of non-reflective boundary conditions is straightforward. In problems where Riemann invariants are unknown (e.g. the flow in non-rectangular channels, the stratified 2D shallow water flows) it is possible to impose that kind of conditions analyzing the projection of the Jacobians of advective flux functions onto normal directions of fictitious surfaces or boundaries. In this paper a general methodology for developing absorbing boundary conditions for non-linear hyperbolic advective–diffusive equations with unknown Riemann invariants is presented. The advantage of the method is that it is very easy to implement in a finite element code and is based on computing the advective flux functions (and their Jacobian projections), and then, imposing non-linear constraints via Lagrange multipliers. The application of the dynamic absorbing boundary conditions to typical wave propagation problems with unknown Riemann invariants, like non-linear Saint-Venant system of conservation laws for non-rectangular and non-prismatic 1D channels and stratified 1D/2D shallow water equations, is presented. Also, the new absorbent/dynamic condition can handle automatically the change of Jacobians structure when the flow regime changes from subcritical to supercritical and viceversa, or when recirculating zones are present in regions near fictitious walls.     

Design automation in MEDEA: present and future

The semiconductor industry has been growing at an unprecedented level since its start in the early 1960s. Capitalizing on the outstanding properties of silicon and its stable oxide permitted the introduction of the CMOS industry, the leading semiconductor industry process. However, the average 15% to 16% annual growth in semiconductor sales has also presented tremendous problems of huge investments in manufacturing. Mandatory now is a rapid return of investment through advanced products (in the latest available processes) that have high added value at the system level. Sometimes the system is the product itself, which raises thoughts of new ways to design these complex systems on a single chip that mixes several functionalities. This article explores a future European evolution of design automation, discussing the present status of Europe's lack of local industrial developments as well as its tremendous knowledge reservoir. Earlier MEDEA activities paved the road to new design solutions and gave European companies the chance to influence US developments, as is evidenced by frequent technology partnerships with US software vendors. Recently, we have seen a significant increase in European start-ups in advanced design automation domains (hardware-software codesign, intellectual property reuse, deep-submicron effects)     

融合对象性和视觉显著度的单目图像2D转3D

受对象性测度和视觉显著度的启发,提出一种适用于单目图像2D转3D的对象窗深度中心环绕分布假设,给出融合对象性测度和视觉显著度的单目图像深度估计算法。首先计算图像的视觉显著度并将其映射成深度;其次在图像上随机采样若干个窗,并计算这些窗的对象性测度;再次,定义一个能量函数用于度量深度和对象性测度对彼此的影响程度,并通过迭代优化的方法改进深度和对象性测度的估计结果;最后,根据深度信息进行3D视频合成。实验结果表明,融入对象性测度信息后,显著改进了基于视觉显著度2D转3D的深度估计质量,保证了估计深度在对象边界处的不连续过渡和其他区域的平滑过渡。     

Rethinking deep-submicron circuit design

Interconnect delay need not increase as CMOS process geometries shrink, and current IC design methods should suffice for modules of up to 50,000 gates. Beyond that, designers must focus on a new concept - global interconnect design. We consider the effects of both devices and interconnect, and our analysis shows that interconnect delay actually decreases for deep-submicron (DSM) processes in a modular design approach. The physical explanations of these DSM effects shed insight into this and other potential impacts on future high-performance ASIC designs     

A node-centric indirect boundary element method: three-dimensional displacement discontinuities

An indirect boundary element formulation based on unknown physical values, defined only at the nodes (vertices) of a boundary discretization of a linear elastic continuum, is introduced. As an adaptation of this general framework, a linear displacement discontinuity density distribution using a flat triangular boundary discretization is considered. A unified element integration methodology based on the continuation principle is introduced to handle regular as well as near-singular and singular integrals. The boundary functions that form the basis of the integration methodology are derived and tabulated in the appendix for linear displacement discontinuity densities. The integration of the boundary functions is performed numerically using an adaptive algorithm which ensures a specified numerical accuracy. The applications include verification examples which have closed-form analytical solutions as well as practical problems arising in rock engineering. The node-centric displacement discontinuity method is shown to be numerically efficient and robust for such problems.     

Analytical solution of coupled stress-flow-transport processes in a single rock fracture

A closed-form solution is presented for modeling the coupled stress-flow-transport processes along a single fracture embedded in a porous rock matrix. Necessary assumptions were made to simplify the subject into a two-dimensional (2D) problem, considering the changes of fracture aperture and matrix porosity under various stress conditions. The cubic law was assumed to be valid for the fluid flow in the fracture, with an impermeable rock matrix. For transport mechanisms, advective transport along the fracture, longitudinal hydrodynamic dispersion in the flow direction, and the matrix diffusion were considered in three different transport models under constant concentration or constant flux (Danckwerts') inlet boundary conditions. This analytical solution can be used as a constitutive model, or as an example for validation of similar constitutive models, for modeling the coupled hydro-mechanical-chemical (HMC) processes in fracture networks of crystalline rocks. The influences of stress/deformation processes on different transport mechanisms in a single fracture under different inlet boundary conditions were studied for the first time. The results show that changes of fracture, as controlled by a combination of normal closure and shear dilatancy, have a significant influence on the solute concentration distribution both along the fracture and in the rock matrix, as well as on the solute residence/breakthrough time, especially when shear-induced dilatancy occurs. Under compressions, the decreasing matrix porosity slightly increases the solute concentration along the fracture and in the rock matrix.     

Harmonic solution of semiconductor transport equations for microwave and millimetre-wave device modelling

The hydrodynamic transport equations for charges in a semiconductor have been solved for a periodic excitation by means of a harmonic approach, in order to model microwave and millimetre-wave active devices. The solution is based on the expansion of physical variables in a Fourier series in the time domain, and on discretisation in the space domain. A waveform-balance technique in the TD is used to solve the nonlinear equations system. This approach allows for a longer time step with respect to standard TD solutions for most cases of interest, greatly reducing simulation time by at least two orders of magnitude in typical cases. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14: 36–48, 2004.     

Electrohydrodynamic modeling of microdroplet transient dynamics in electrocapillary-based digital microfluidic devices

In this article, a multiphysics approach is used to develop a model for microdroplet motion and dynamics in contemporary electrocapillary-based digital microfluidic systems. Electrostatic and hydrodynamic pressure effects are combined to calculate the driving and opposing forces as well as the moving boundary of the microdroplet. The proposed methodology accurately predicts the microdroplet electrohydrodynamics which is crucial for the design, control and fabrication of such devices. The results obtained from the model are in excellent agreement with expected trends and experimental results.