Device CAD in the '90s: at the crossroads

Various issues concerning technology computer-aided design (TCAD), including fundamental research, practical issues of user friendliness, experimental verification, and framework initiatives are discussed. The focus is on device CAD, in which there is a continuing shift of emphasis from basic issues of device physics and engineering to questions of manufacturability and technology scalability. The automation of input, computational mesh, and electrical biasing information generation in TCAD systems is described. The visualization and interpretation of simulated results, the advent of new computer hardware, and the use of statistical simulations in TCAD technology are discussed. It is argued that while technology experts are willing to tolerate awkwardness in a TCAD system, new users of TCAD, such as circuit designers and manufacturing engineers, demand automation, robustness, and reliability as standard features     

Efficient analytical formulation and sensitivity analysis of neuro-space mapping for nonlinear microwave device modeling

A new computer-aided design (CAD) method for automated enhancement of nonlinear device models is presented, advancing the concept of Neuro-space mapping (Neuro-SM). It is a systematic computational method to address the situation where an existing device model cannot fit new device data well. By modifying the current and voltage relationships in the model, Neuro-SM produces a new model exceeding the accuracy limit of the existing model. In this paper, a novel analytical formulation of Neuro-SM is proposed to achieve the same accuracy as the basic formulation of Neuro-SM (known as circuit-based Neuro-SM) with much higher computational efficiency. Through our derivations, the mapping between the existing (coarse) model and the overall Neuro-SM model is analytically achieved for dc, small-signal, and large-signal simulation and sensitivity analysis. The proposed analytical formulation is a significant advance over the circuit-based Neuro-SM, due to the elimination of extra circuit equations needed in the circuit-based formulation. A two-phase training algorithm utilizing gradient optimization is also developed for fast training of the analytical Neuro-SM models. Application examples on modeling heterojunction bipolar transistor (HBT), metal-semiconductor-field-effect transistor (MESFET), and high-electron mobility transmistor (HEMT) devices and the use of Neuro-SM models in harmonic balance simulations demonstrate that the analytical Neuro-SM is an efficient approach for modeling various types of microwave devices. It is useful for systematic and automated update of nonlinear device model library for existing circuit simulators.     

Rare-earth-enabled universal solders for microelectromechanical systems and optical packaging

In packaging of microelectromechanical systems (MEMS), optical, and electronic devices, there is a need to directly bond a wide variety of inorganic materials, such as oxides, nitrides, and semiconductors. Such applications involve hermetic-sealing components, three-dimensional MEMS assembly components as well as active semiconductor or optical components, dielectric layers, diffusion barriers, waveguides, and heat sinks. These materials are known to be very difficult to wet and bond with low melting-point solders. New Sn-Ag- or Au-Sn-based universal solders doped with a small amount of rare-earth (RE) elements have been developed, which now allow direct and powerful bonding onto the surfaces of various MEMS, optical, or electronic device materials. The microstructure, interface properties, and mechanical behavior of the bonds as well as the potential packaging applications of these new solder materials for MEMS and optical fiber devices are described. Various packaging-related structural, thermal, or electrical issues in MEMS are also discussed.     

Microelectromechanical systems

The evolution and maturity of microelectromechanical systems (MEMS) in the coming years will be driven less by captive fabrication facilities and process development and more by innovative, aggressive electromechanical systems design. MEMS is poised to take full advantage of advances in information technology and couple them to advances in other disciplines to drive a fundamentally new approach to electromechanical system design and fabrication. By merging sensing and actuation with computation, MEMS will not only invest existing systems with enhanced capabilities and reliability but also will make possible radically new devices and systems designs that will exploit the miniaturization, multiplicity, and microelectronics of MEMS. For the first time, approaches akin to VLSI electronics can be taken to usher in an equally exciting and productive era of VLSI electromechanics     

MEMS器件VHDL-AMS宏模型

随着MEMS集成度的提高,迫切需要有相应的CAD工具进行系统级的设计与模拟,由于MEMS器件的工作原理包含了多种能量的耦合,宏模型的建立成了系统级设计的“瓶颈”。模拟硬件描述语言(如VHDL-AMS)提供了一种有效的方法,即建立起表示MEMS器件动态特性的常微分方程和代数方程(DAE),然后对其描述,形成相应的库单元,利用现有电路分析软件进行系统级模拟。本文介绍了MEMS器件VHDL描述的过程,并给出了横向谐振器描述的例子。     

用于MEMS器件芯片级封装的金-硅键合技术研究

MEMS器件大都含有可动的硅结构 ,在器件加工过程中 ,特别是在封装过程中极易受损 ,大大影响器件的成品率。如果能在MEMS器件可动结构完成以后 ,加上一层封盖保护 ,可以显著提高器件的成品率和可靠性。本文提出了一种用于MEMS芯片封盖保护的金 硅键合新结构 ,实验证明此方法简单实用 ,效果良好。该技术与器件制造工艺兼容 ,键合温度低 ,有足够的键合强度 ,不损坏器件结构 ,实现了MEMS器件的芯片级封装。我们已经将此技术成功地应用于射流陀螺的制造工艺中     

Coupled package-device modeling for microelectromechanical systems

Microelectromechanical systems (MEMS), by their nature as sensors and actuators, require application specific packaging. The package is the near environment of the MEMS device and hence has a direct effect on its thermal behavior, mechanical effects, environmental compatibility and contamination. Therefore, understanding the influence of the packaging on MEMS device performance is critical to a successfully coupled package-device co-design. Here, an automated package-device interaction simulator has been developed. The simulator uses separate finite element method models for both the package and the device analysis and ties the simulations together through parametric behavioral package models. This technique allows the generation of package model libraries and supports the co-design of application specific packaging and MEMS devices. In the current implementation, thermomechanical package models have been implemented. Experimental verification of the technique is demonstrated by the comparison of simulation results to the measured package strain data. Although MEMS device-package interactions are not the only systems that could benefit from this method, they are a significant application area, focused on here.     

Measurement-based large-signal diode modeling system for circuitand device design

A novel relaxation-time large-signal table-based diode model for circuit simulation is presented. A fully automated system which characterizes the device and generates the tabular data file used by the model is also presented. Excellent agreement between simulated and measured fundamental and second through fourth harmonic power levels is demonstrated for a MODFET diode up to frequencies of 48 GHz. The results presented show that this diode model and its associated automated data acquisition and model generator systems yield accurate simulations of diode devices from diverse technologies over a wide variety of biases, frequencies, and input signal amplitudes. This makes the measurement-based modeling system a valid CAD (computer-aided design) tool for automated diode characterization and for large- and small-signal analysis and design of circuits and systems where such devices are key components     

MEMS工艺集成化设计及其可视化

针对目前MEMS设计复杂 ,直观性差等问题 ,提出了工艺集成化设计和可视化的可行性解决方案 ,对其中的关键技术进行了研究 ,并基于所提出的方案研究了工艺设计的集成化和可视化的实现技术。首先对MEMS表面加工工艺进行了详细的分析 ,采用面向过程的方法建立了表面工艺过程的统一模型。基于这一模型 ,研究了MEMS工艺设计的集成化技术 ,实现了工艺设计中各种信息的集成化 ,并设计开发了工艺设计的集成化软件环境。最后 ,对工艺设计中的二维版图的三维重构算法进行了详细的研究 ,通过SolilWorksAPI接口的开发 ,在SolilWorks的环境下实现了工艺过程的三维可视化     

The use of computer aids in IC technology evolution

Computer-aided analysis of integrated circuit devices has played a critical role for more than three decades of technology evolution. In the 1950s and early 1960s simulation was used extensively to characterize the operating principles of both bipolar and MOS devices. Bipolar effects such as base-width modulation and base pushout were characterized as well as MOS phenomena including gradual channel and channel-length modulation effects. During the late 1960s and throughout the 1970s simulation provided critical insight in the scaling of devices leading to the advent of very large scale integration (VLSI). Starting in the mid-1970s the modeling of fabrication technology became an important adjunct to device analysis. The need to control threshold and subthreshold behavior of scaled devices played a significant role in this synergistic coupling. Now in the mid-1980s the role of both device and process analysis have each come to new plateaus of both performance and utility. The scaling of submicrometer channel-length MOS devices poses a new set of constraints and challenges. This paper traces the evolution of computer-aided analysis over the past three decades. Unique aspects of the device physics and the role of device and process analysis at each phase of development will be presented. The progression from device conception towards stabilizing the technologies for large-scale product are presented. Problems of submicrometer technology including both production issues as well as new physical requirements for both process and device modeling will be dealt with, including the opportunity presented with the rapid advances in computer technology and the seemingly inevitable computational bottleneck posed by the growing needs for three-dimensional simulation.     

Applications of MEMS in surgery

In the past few decades, microelectromechanical systems (MEMS) have found themselves being adopted into a wide variety of fields and disciplines. Recently there has been an increased interest in the use of MEMS for surgical applications. MEMS technology has the potential to not only improve the functionality of existing surgical devices, but also add new capabilities, which allow surgeons to develop new techniques and perform entirely new procedures. MEMS can improve surgical outcomes, lower risk, and help control costs by providing the surgeon with real-time feedback on the operation. This paper discusses the challenges MEMS face in the medical device market along with current applications and future directions for the technology.     

微机电系统计算机辅助设计的研究

微机电系统(MEMS)的计算机辅助设计(CAD)是MEMS实现商品化的重要基础。文章介绍了MEMSCAD的概况和技术特点，提出了一种MEMSCAD的典型体系结构和MEMS建摸与模拟的层次，重点研究了微机电系统中的耦合场分析和宏模型与系统级模拟等关键问题。     

Computer-aided design: limitations in automating design anddrafting

The impact of CAD (computer-aided design) on employment and skill is examined. First, the relationship between the adoption of mechanical CAD systems and employment of drafters in the aerospace and automobile industries is assessed. Contrary to many employment projections, drafting employment in these industries increased with increases in the adoption of CAD systems. Second, the effects of design automation and skill transformation capacities of electronic CAD systems on printed circuit board designers are evaluated. Third, the limits to automation of design are explored, suggesting that there are trade-offs between automation of the design process and innovation in product design. The logical limits of software, flaws in programming, and the dynamic nature of product markets are evaluated as factors limiting automation     

VLSI: linking design and manufacturing

A set of computer-aided design (CAD) tools that predict the effects of various manufacturing steps along with the chip's internal dimensions is described. Called the Process Engineer's Workbench, the system predicts the chip's characteristics, their statistical distribution, and the manufacturing yield likely from any one fabrication process. The tools are even sensitive to the small random variations that increase in significance as devices shrink in size. Workbench can be used to compare its programs' predictions and those of other software tools with actual measurements of devices and processes. Some existing CAD tools are reviewed to highlight the Workbench's advantages, and the features of the latter are examined. Written in C language for a Digital Equipment VAXstation, Workbench was designed to be portable and runs on several other popular workstations. It contains two basic libraries, namely, one of device models, the other of process step models     

Applications of Microelectromechanical Systems in Industrial Processes and Services

This paper presents a review of the current and future applications of microelectromechanical systems (MEMS) in the industrial sector. A historical perspective of the origin and development of MEMS is presented, as well as the traditional and innovative fabrication techniques. The process flow of computer-aided design and simulation is also discussed. After that, several of the most important applications of microsystems in the manufacturing and production sectors are enumerated and described. Two case examples are discussed in depth: gyroscopes for the measurement of angular movement, where the basic laws are provided, and a thorough review of existing devices is presented; and particle production devices for the generation of micrometer-sized droplets, where the two most common techniques are compared, along with the challenges that remain open. Finally, some conclusions and perspectives for the future are presented and discussed.     

CAD systems for VLSI in Japan

With the advent of the VLSI era, computer-aided design (CAD) is increasing its importance, and much effort is now being expended on CAD by many IC manufacturers and laboratories in Japan. This paper reviews the historical aspect of the CAD systems developed in this field, and describes the current status of VLSI CAD systems and technologies, from device to system levels, in Japan. The CAD development activities for IC's were initiated in the late 1960's. At present, VLSI CAD systems and related CAD technologies in Japan seem to be in the adolescent stage-partly capable of practical use and partly still in the immature state.     

MEMS器件封装的低温玻璃浆料键合工艺研究

玻璃浆料是一种常用于MEMS器件封装的密封材料.系统研究了MEMS器件在低温下使用玻璃浆料键合硅和玻璃的过程.与大多数MEMS器件采用的玻璃浆料相比(烧结温度400℃以上),此工艺(烧结温度350℃)在键合完成后所形成的封装结构同样具有较高的剪切强度(封装器件剪切强度大于360 kPa),同时具有较好的气密性(合格率达到93.3%),漏率测试结果符合相关标准.结果表明,在保证MEMS器件封装剪切强度和气密性的同时,降低键合温度条件是可以实现的.     

Computer-aided design: a case of strategy in implementing a newtechnology

In this case study the introduction of computer-aided design (CAD) in an engineering company was analyzed. The process of change as well as repercussions of the new technology on work organization and communication patterns within the company were studied. The designers has received the new technology favorably and were even impatient about the pace of change. As the development of the system was limited to a small group close to the design management, the introduction had less than desirable effects on the work situation of the designers and on the cooperation with other functions that was envisaged in the planned CAD/CAM step. The study confirms that CAD, as such, will have little effect on a bureaucratic organization unless such a change is included as an explicit objective. For a full utilization of any new technology a joint forum for outlining a strategy is needed     

基于MEMS共面波导腔的带阻滤波器的设计

应用计算机辅助设计了一种基于共面波导结构的MEMS带阻滤波器.研究了微尺度电磁学、力学、温度等效应.利用ANSOF的HFSS软件模拟分析了滤波器的损耗参数,并应用ANSYS软件分析复合结构的热应力分布,得出了阻带中心频率在18GHz的MEMS带阻滤波器件,提供了一些有意义的理论分析及应用.