Free-Form Simulation of Sequential Etching and Surface Characterization for 3-D MEMS Fabrication

A new diffusion-based simulation model of isotropic wet etching and free-form surface characterization method for 3-D free-form microelectromechanical systems (MEMS) fabrication is presented in this paper. To simulate the etching process, a diffusion-based model solved by the finite-element method (FEM) has been developed, allowing extraction of more accurate etch-front data at discrete time steps. In the developed method, free-form MEMS objects are modeled as B-spline functions with material concentration. Finite elements are generated by discretization in the parametric domain of the free-form object and mapping back to the Euclidean space. Points on the etch front are extracted using a Z-map method. The extracted point data are characterized to obtain a B-spline representation of the etch-front surface. Examples from the isotropic etching simulation of 2-D and 3-D objects with both regular and free-form geometry are presented. The developed method allows the simulation of 3-D objects with free-form input and free-form mask opening and facilitates the simulation of sequential etching of free-form objects with irregular mask openings. This paper also discusses applications of the developed method in MEMS process planning that can be realized by taking advantage of the better control of geometry that it provides in MEMS fabrication.     

Accurate Simulation of RF MEMS VCO performance including phase noise

A new coupled circuit and electrostatic/mechanical simulator (COSMO) is presented for the design of low phase noise radio frequency (RF) microelectromechanical systems (MEMS) voltage-controlled oscillators (VCOs). The numerical solution of device level equations is used to accurately compute the capacitance of a MEMS capacitor. This coupled with a circuit simulator facilitates the simulation of circuits incorporating MEMS capacitors. In addition, the noise from the MEMS capacitor is combined with a nonlinear circuit-level noise analysis to determine the phase noise of RF MEMS VCO. Simulations of two different MEMS VCO architectures show good agreement with experimentally observed behavior.     

Computer-aided generation of nonlinear reduced-order dynamicmacromodels. I. Non-stress-stiffened case

Reduced-order dynamic macromodels are an effective way to capture device behavior for rapid circuit and system simulation. In this paper, we report the successful implementation of a methodology for automatically generating reduced-order nonlinear dynamic macromodels from three-dimensional (3-D) physical simulations for the conservative-energy-domain behavior of electrostatically actuated microelectromechanical systems (MEMS) devices. These models are created with a syntax that is directly usable in circuit- and system-level simulators for complete MEMS system design. This method has been applied to several examples of electrostatically actuated microstructures: a suspended clamped beam, with and without residual stress, using both symmetric and asymmetric positions of the actuation electrode, and an elastically supported plate with an eccentric electrode and unequal springs, producing tilting when actuated. When compared to 3-D simulations, this method proves to be accurate for non-stress-stiffened motions, displacements for which the gradient of the strain energy due to bending is much larger than the corresponding gradient of the strain energy due to stretching of the neutral surface. In typical MEMS structures, this corresponds to displacements less than the element thickness, At larger displacements, the method must be modified to account for stress stiffening, which is the subject of part two of this paper     

Design and optimization of RF ICs with embedded linear macromodels of multiport MEMS devices

In this paper, we demonstrate efficient modeling approach for simulation, analysis, design, and optimization of multiport radio frequency microelectromechanical systems (RF MEMS) resonating structures embedded in RF circuits. An in‐house finite element method (FEM) solver is utilized to develop accurate and efficient macromodels that capture all the essential characteristics of the device. Using the datasets generated from the FEM simulations, the artificial neural network models are trained for two‐way mapping between the physical input and electrical output parameters. Realized model is implemented in a circuit simulator, enabling a simple yet accurate circuit simulator compatible modeling and optimization procedure instead of memory and time demanding FEM analysis. The derivation of dynamic macromodels with preserved electromechanical behavior of the multiport resonating structures is also presented. Capabilities of the proposed approach are demonstrated with several examples featuring capacitively actuated MEMS resonating structures: a clamped–clamped beam, a free–free beam, and a coupled clamped–clamped beam. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

A UML-based object-oriented approach for design and simulation of a drug delivery system

Given complexity of the design and manufacturing processes of microelectromechanical system (MEMS) products, we present a unified modeling language (UML) based design approach for multi-domain products or systems like MEMS to designing and evaluating possible solutions at the early design stage to shorten their development time. Specifically, the proposed approach is used to model and analyze a novel drug delivery system combining MEMS devices and integrated circuit (IC) units. This drug delivery system aims to be used for safer and more effective therapy of the diabetics. Two design models about the whole drug delivery system and its micropump subsystem are established using UML diagrams; in particular a composition diagram with components and ports describes the topology of the system. Through design and simulation on the micropump subsystem, it is found that the variations of geometrical dimension and excitation voltage affect the characterization of the micropump. The simulation results demonstrate and validate the proposed approach, and can be used as a significant reference for the designer to design the optimal micropump.     

3D-feature-based structure design for silicon fabrication of micro devices

To make MEMS structure design in a more intuitive way, and to support the “function to 3D shape to mask” design flow, a 3D feature based structure design framework and its corresponding key enabling techniques are presented on the basis of inverse design processes and top-down design methodologies. Driven by space mapping among function and structure, the feature model and its parameters are restricted with the bond graph represented simulation model, which is constructed with functional components in simulation library at the system-level. Conforming design rules, the hierarchic feature information model is established and finally can be cascaded down to a group of 3D feature nodes, which are all silicon fabrication oriented and defined on the top of CSG/B-rep 3D solid models. Surrounding this feature information model, the 2D mask deducing and fabrication parameters extraction at the fabrication-level can be performed for manufacturability checking, design/fabrication conflict feedback and fabrication process sequence generation. Taking a micro gap-closing actuator as an example, the structure design process is demonstrated in terms of this 3D feature modeling methodology.     

基于仿真的电路板级故障诊断测试方法

针对某雷达定时器板的电路特点,提出了一种基于仿真的电路板级故障诊断测试方法。首先,利用pspice对被测电路进行功能模型建模和故障模型建模,根据功能模型构建电路仿真原理图进行功能仿真,进而利用故障模型做故障注入进行故障仿真,仿真结束获取功能仿真和故障仿真数据,通过小波分析的方法提取仿真数据的特征,包括能量分布特征提取、极值特征提取和熵特征提取,并做测试节点优化删除冗余数据,最后通过概念格的方法对特征数据做训练,生成应用于被测对象的故障诊断模型。通过获取的故障诊断模型对诊断数据进行故障推理,验证了测试方法的可行性。     

Chip-level integration of RF MEMS on-chip inductors using UV-LIGA technique

This paper presents a chip-level integration of radio-frequency (RF) microelectromechanical systems (MEMS) air-suspended circular spiral on-chip inductors onto MOSIS RF circuit chips of LNA and VCO using a multi-layer UV-LIGA technique including SU-8 UV lithography and copper electroplating. A high frequency simulation package, HFSS, was used to determine the layout of MEMS on-chip inductors with inductance values close to the target inductance values required for the RF circuit chips within the range of 10%. All MEMS on-chip inductors were successfully fabricated using a contrast enhancement method for 50 μm air suspension without any physical deformations. High frequency measurement and modeling of the integrated inductors revealed relatively high quality factors over 10 and self-resonant frequencies more than 15 GHz for a 1.44 nH source inductor and a 3.14 nH drain inductor on low resistivity silicon substrates (0.014 Ω cm). The post-IC integration of RF MEMS on-chip inductors onto RF circuit chips at a chip scale using a multi-layer UV-LIGA technique along with high frequency measurement and modeling demonstrated in this work will open up new avenues with the wider integration feasibility of MEMS on-chip inductors in RF applications for cost-effective prototype applications in small laboratories and businesses.     

基于晶体管级参数提取的后仿真

介绍了时钟电路芯片的功能,给出了Star-RCXT(RC参数提取工具)的晶体管级参数提取及后仿真流程,详细描述了一些基于晶体管级参数提取的版图后仿真设计经验,给出了设计的前、后仿真的输出对比结果.     

CARAMEL: Contamination And Reliability Analysis ofMicroElectromechanical Layout

CARAMEL (Contamination And Reliability Analysis of MicroElectromechanical Layout) is a CAD tool for MEMS fault model generation. It is based on the integrated circuit contamination analysis tool CODEF and is capable of analyzing the impact of contamination particles on the behavior of microelectromechanical systems. CARAMEL's simulation output indicates that a wide range of defective structures are possible due to the presence of particulate contaminations. Moreover, electromechanical simulations of CARAMEL's mesh representations of defective layout has revealed that a wide variety of misbehaviors are associated with these defects. Several thousand contamination simulations were performed using CARAMEL on the surface micromachined comb-drive resonator. The results generated by CARAMEL identifies the comb drive as the most defect prone region of the microresonator and the deposition of the first structural layer as the most vulnerable processing step     

An investigation into the electrostatic force representation for electrically actuated microelectromechanical systems

The ever-increasing demand for microelectromechanical systems (MEMS) in modern electronics has reinforced the need for extremely accurate analytical and reduced-order models to aid in the design of MEMS devices. Many MEMS designs consist of cantilever beams with a tip mass attached at the free end to act as a courter electrode for electrical actuation. One critical modeling aspect of electrically actuated MEMS is the electrostatic force that drives these systems. The two most used representations in the literature approximate the electrostatic force between two electrodes as a point force. In this work, the effects of the representation of the electrostatic force for electrically actuated microelectromechanical systems are investigated. The system under investigation is composed of a beam with an electrode attached to its end. The distributed force, rigid body, and point mass electrostatic force representations are modeled, studied, and their output results are compared qualitatively. Static and frequency analyses are carried out to investigate the influences of the electrostatic force representation on the static pull-in, fundamental natural frequency, and mode shape of the system. A nonlinear distributed-parameter model is then developed in order to determine and characterize the response of electrically actuated systems when considering various representation of the electrostatic forces. The results show that the size of the electrode may strongly affect the natural frequencies and static pull-in when the point mass, rigid body, and plate representations are considered. From nonlinear analysis, it is also proven that the representation may affect the hardening behavior of the system and its dynamic pull-in. This modeling and analysis give guidelines about the usefulness of the electrostatic force representations and possible erroneous assumptions that can be made which may result in inaccurate design and optimal performance detection for electrostatically actuated systems.

     

One MEMS design tool with maximal six design flows

This paper presents one MEMS design tool with a total six of design flows, which makes it possible that the MEMS designers choose the most suitable design flow for their specific devices. The design tool is divided into three levels and interconnected by six interfaces. The three levels are the lumped-element model based system level, finite element analysis based device level and process level, which cover nearly all modeling and simulation functions for MEMS design. The six interfaces are proposed to automatically transmit the design data between every two levels, thus the maximal six design flows could be realized. The interfaces take the netlist, solid model and layout as the data inlet and outlet for the system, device and process level respectively. The realization of these interfaces are presented and verified by design examples, which also proves that enough flexibility in the design flow can really increase the design efficiency.     

Design and process considerations for fabricating RF MEMS switches on printed circuit boards

Design considerations and process development for fabricating radio frequency microelectromechanical systems (RF MEMS) switches on microwave laminate printed circuit boards (PCBs) are presented in details in this work. Two key processes, high-density inductively coupled plasma chemical vapor deposition (HDICP CVD) for low-temperature silicon nitride deposition, and compressive molding planarization (COMP) have been developed for fabricating RF MEMS switches on PCB. The effects of process conditions of HDICP CVD on low-temperature nitride film are fully characterized for its use in RF MEMS switches on PCB. Not only can COMP planarize the surface of the photoresist for lithographic patterning over topologically complex surfaces, but also simultaneously create a membrane relief pattern on the surface of a MEMS structure. Several membrane-type capacitive switches have been fabricated showing excellent RF performance and dynamic responses similar to those on semiconductor substrates. This technology promises the potential of enabling further monolithic integration of switches with other RF components, such as antennas, microwave monolithic integrated circuits (MMICs), phase shifters, tunable filters, and transmission lines on the same PCBs reducing the losses due to impedance mismatching from components/system assembly and simplifies the design of the whole RF system. [1416].     

Novel analog pulse‐width‐modulated 15‐μm SiGe micromirrors

Abstract— A novel six‐electrode SiGe micromirror pixel enabling analog pulse‐width modulation (PWM) in display applications is presented. Instead of utilizing bitplanes, arbitrary duty cycles can be realized, resulting in an analog gray‐level distribution. This eliminates the posterization (contouring) effect that is typical for digital micromirrors. Moreover, the pixel design does not require the incorporation of electronic comparators and the gamma compensation can be processed externally. Two out of the six electrodes are used as landing electrodes. The other four attracting electrodes are driven by two anti‐phase saw‐tooth signals and two fixed analog voltage signals. By applying this signal scheme, the duty cycle of the mirror is modulated in an analog manner. Test vehicles were manufactured where SiGe is the microelectromechanical systems (MEMS) material. The use of SiGe as a structural layer is advantageous to build MEMS since the CMOS and MEMS layers can be deposited in a monolithic manner. Measurements using a Laser Doppier Vibrometer (LDV) have confirmed the feasibility of analog PWM for 15‐μm SiGe micromirrors.     

集成印制电路板设计系统IPBDS

本文描述一个在微型计算机上实现的集成印制电路板设计系统IPBDS.在IPBDS的研制过程中,采用了支持分层设计的并行系统结构,将各种用于设计输入、设计检验和布图设计等CAD工具集中由一个设计数据库进行统一的组织和管理,实现了电路设计的一次性输入存储,供多个CAD工具共同使用,避免了各工具间复杂和重复的数据转换,减少了存储的冗余,保证了数据的一致性和设计的完整性,为印制电路板设计提供了一个集成和有效的环境.     

Multi-level and multi-objective design optimisation of a MEMS bandpass filter

Microelectromechanical system (MEMS) design is often complex, containing multiple disciplines but also conflicting objectives. Designers are often faced with the problem of balancing what objectives to focus upon and how to incorporate modeling and simulation tools across multiple levels of abstraction in the design optimization process. In particular due to the computational expense of some of these simulation methods there are restrictions on how much optimization can occur. In this paper we aim to demonstrate the application of multi-objective and multi-level design optimisation strategies to a MEMS bandpass filter. This provides for designers the ability to evolve solutions that can match multiple objectives. In order to address the problem of a computationally expensive design process a novel multi-level evaluation strategy is developed. In addition a new approach for bandpass filter modeling and optimization is presented based up the electrical equivalent circuit method. In order to demonstrate this approach a comparison is made to previous attempts to design similar bandpass filters. Results are comparable in design but at a significant reduction in functional evaluations, needing only 10,000 functional evaluations in comparison to 2.6 million with the previous work.     

Three-dimensional electromagnetic simulation of electronic circuits of general shape

A general purpose CAD tool, the IE3D electromagnetic simulator is presented in this article. The simulator is based on an integral equation, a method-of-moment formulation for a full-wave solution of three-dimensional (3D) arbitrarily shaped structures in microwave and millimeter-wave integrated circuits (MMIC), high temperature superconductor (HTS) circuits, microstrip antennas, RF printed circuit boards (PCB), and high speed digital circuit packaging. The primary solution of the simulator is the current distribution on a metallic structure in an environment of multilayered substrates on infinitely extended ground plane. The circuit parameters of the structure in either S-parameter form or RLC-SPICE equivalent circuit form is extracted from the solved current distribution. The simulator consists of an MS-Windows-based layout editor, a schematic editor, an electromagnetic simulator, and a post processor. The simulator can perform stand-alone electromagnetic simulation and optimization and mixed electromagnetic and nodal analysis. Simulation results for structures in various high frequency and high speed domains are presented and compared to measured results. © 1994 John Wiley & Sons, Inc.     

MEMS可编程光栅动态驱动电路的研制

MEMS可编程光栅的工作性能很大程度依赖于驱动电路的性能。本文根据MEMS可编程光栅的工作特点及结构参数,提取出光栅的等效电容值,并采用集成高压运放研制出一种新型的MEMS可编程光栅的动态驱动电路。为了避免自激振荡的发生,电路中采用了频率补偿和并联反馈电容的方法,有效提高了电路的稳定性。实际电路经过测试,其动态性能与PSPICE10仿真的结果非常吻合。该动态驱动电路具有高的电压输出范围(0~180V),较高的频率响应(10kHz),大范围容性负载能力(1~1000pF),完全能够满足MEMS可编程光栅动态复杂控制的需要。     

Electronically probed measurements of MEMS geometries

Measurement of microelectromechanical systems (MEMS) geometry is critical for device design and simulation, material property extraction, and post-fabrication trimming. In this paper electrostatically driven laterally resonant comb-drive test structures with prescribed changes in spring width are used to ascertain systematic variations in process offsets (edge biases) and sidewall angles. The technique is both in situ and nondestructive. An analytical model for the resonant frequency, tuned with three-dimensional (3-D) simulations using MEMCAD, includes effects of a distributed mass, residual stress, and compliant supports. The model is corroborated by 3-D numerical simulations to validate the extraction approach. Fits of this model to experimental data determine the offset and sidewall angle of polysilicon devices fabricated by the Multi-User MEMS Processes of the Microelectronics Center of North Carolina, Research Triangle Park, NC     

MEMS的设计方法与系统模拟

随着MEMS产业重点从单个的MEMS器件向MEMS系统产品的转移 ,MEMS系统级模拟变得日益重要 .文中主要介绍了MEMS系统的一些结构化、标准化的设计方法以及MEMS系统建模与模拟的分级 ,重点阐述了MEMS器件级与系统级模拟之间的桥梁———宏模型的建立及系统级模拟的实现。最后介绍了微加速度计系统模拟的一个例子