多晶SiC梳齿驱动器的模态分析

碳化硅以其优异的电学、机械和化学性能成为极端条件下MEMS器件应用的首选材料。梳齿驱动器的固有频率是MEMS器件结构设计中的一个重要参数。采用有限元分析方法,对多晶SiC梳齿驱动器进行了模态分析,得到了前六个模态的固有频率,并与相同结构的硅基梳齿驱动器的固有频率进行了比较,计算结果与理论预言十分吻合。     

SiC薄膜材料在MEMS中应用的研究进展

SiC材料具有极为优良的物理化学性能，以SiC材料替代传统Si材料制成的SiC微电子机械系统(MEMS)，克服了Si MEMS本身性能的局限性，可满足在高温、高腐蚀等极端条件下的应用。文章综述了近几年SiC薄膜在MEMS中应用的研究进展，详细讨论了薄膜的性能、主要制备方法及微机械加工技术在SiC MEMS的应用。最后，分别举例说明SiC薄膜材料在MEMS中作为保护层和结构层应用的研究现状。     

MEMS器件中的铁电材料

铁电材料在微电子技术、光电子技术和集成光学等多个领域中具有极为重要的应用价值。本文简要介绍了铁电材料及其在MEMS器件方面的应用情况。     

立方相SiC MEMS器件研究进展

主要介绍了近年来国内外出现的有市场推广潜力的立方相碳化硅(3C-SiC)MEMS器件,详细描述了其中一些典型器件的基本结构、加工工艺及初步测试结果,并指出了要想提高器件的可靠性,需要获得低残余应力、低应力梯度的薄膜材料,应当采用合适的刻蚀方法,还需保证金属与碳化硅欧姆接触的稳定性,同时高温引线键合与封装工艺亦不能忽视。随着材料生长和加工成本的不断降低,3C-SiC基MEMS器件将会逐步走向商品化。     

基于谐振原理的RF MEMS滤波器的研制

采用与IC工艺兼容的硅表面MEMS加工技术,以碳化硅材料作为结构材料,研制出一种新型的基于谐振原理工作的RF MEMS滤波器。详细介绍了器件的工作原理、制备方法、测试技术和结果,并对测试结果做出分析。该RF MEMS滤波器由弹性耦合梁连接两个结构尺寸和谐振频率完全相同的MEMS双端固支梁谐振器构成,MEMS谐振器的结构决定了滤波器的中心频率,弹性耦合梁的刚度决定了滤波器的带宽。在大气环境下测试器件的频响特性,得到中心工作频率为41.5MHz,带宽为3.5MHz,品质因数Q为11.8。     

氧化锆／碳化硅复合材料制备与性能研究

碳化硅耐火材料具有优良的高温力学性能,耐磨损性好,热稳定性佳、热膨胀系数小,热导率大以及耐化学腐蚀等优良的性能,但碳化硅耐火材料高温抗氧化性差限制了其在耐火材料领域的应用。本文以碳化硅为基体材料,氧化锆为表层涂覆材料,添加其他微量氧化物为烧结助剂,通过干压成型方式在1500～1600℃范围内制备五层复合共烧结梯度材料。通过对材料显微结构和热学性能的测定分析,制备出表面光滑平整、层间结合紧密,具有良好的化学稳定性,能耗低的五层复合材料。     

碳化硅光学表面数控抛光工艺参数的优化与选择

随着空间应用技术和激光技术的迅猛发展,对光学系统提出了更高的要求;碳化硅材料以其一系列优秀的物理性质,成为一种特别具有应用前景的反射镜材料;碳化硅反射镜光学表面的光学加工研究也在国内外广泛开展。对碳化硅光学表面的抛光机理进行简要讨论;对实验方法、步骤和条件进行了介绍;定性地对碳化硅材料的抛光过程进行了讨论;通过大量的工艺实验和理论分析了对抛光盘转数、磨料粒度、抛光盘材料、抛光盘压力、抛光盘转速、抛光液酸碱度等工艺参数对碳化硅光学表面抛光效果的影响进行了讨论,并对工艺参数进行了优化和选择。     

柔性MEMS衬底材料及其在传感器上的应用

概述了MEMS器件衬底材料的功用及分类(刚性材料和柔性材料)。根据其使用柔性衬底材料的不同,将其分为有机聚合物材料(聚酰亚胺、硅橡胶、聚对苯二甲酸乙二醇酯和聚对二甲苯、硅树脂)和金属及陶瓷材料(不锈钢和氧化铝)。重点阐述了材料的特性,并结合国内外专家学者的研究,例举了其在MEMS传感器方面的应用,分析了它们的特点及优越性。指出在MEMS器件衬底材料领域,对柔性材料和新型Si基材料的研究与开发是未来研究工作的重点和热点。     

MEMS超级电容器研究进展

基于微机电系统(Micro-electro-mechanical systems,MEMS)技术的微型超级电容器是一种以微纳米结构形式实现储能的微型能量存储器件,具有高比容量、高储能密度和高抗过载能力等特点,在MEMS微电源系统、引信系统以及物联网等技术领域具有广泛的应用前景。分析了超级电容器的基本原理和种类,系统综述了MEMS超级电容器的国内外研究现状,重点讨论了基于MEMS加工技术的超级电容器制造方法和优势,从材料、结构设计、加工工艺方面分析了MEMS超级电容器存在的技术瓶颈问题,并展望了其未来的发展趋势和应用需求。     

基于碳化硅的高温压力传感器芯片在国内的研究进展

<正>碳化硅材料凭借其具有一定的压阻效应、较大的带隙、较强的抗腐蚀性能等优点,在压力传感器领域有不错的应用前景,可广泛应用于高温、强辐射、强腐蚀等硅材料无法胜任的极端恶劣的环境中。本文以国内碳化硅高温压力传感器的研究现状为背景,简单介绍几种不同结构类型的碳化硅高温压力传感器。     

Silicon carbide MEMS for harsh environments

Silicon carbide (SiC) is a promising material for the development of high-temperature solid-state electronics and transducers, owing to its excellent electrical, mechanical, and chemical properties. This paper is a review of silicon carbide for microelectromechanical systems (SiC MEMS). Current efforts in developing SiC MEMS to extend the silicon-based MEMS technology to applications in harsh environments are discussed. A summary is presented of the material properties that make SiC an attractive material for use in such environments. Challenges faced in the development of processing techniques are also outlined. Last, a review of the current stare of SiC MEMS devices and issues facing future progress are presented     

A 1-MHz hard-switched silicon carbide DC-DC converter

Silicon Carbide (SiC) is a wide bandgap semiconductor material that offers performance improvements over Si for power semiconductors with accompanying benefits for power electronics applications that use these semiconductors. The wide bandgap of SiC results in higher junction forward voltage drops, so SiC is best suited for majority carrier devices such as field effect transistors (FETs) and Schottky diodes. The wide bandgap of SiC results in it having a high breakdown electric field, which in turn results in lower resistivity and narrower drift regions in power devices. This dramatically lowers the resistance of the drift region and means that SiC devices with substantially less area than their corresponding Si devices can be used. The lower device area reduces the capacitance of the devices enabling higher frequency operation. Here, the results from a 1-MHz hard-switched dc-dc converter employing SiC JFETs and Schottky diodes will be presented. This converter was designed to convert 270Vdc to 42Vdc such as may be needed in future electric cars. The results provide the performance obtained at 1MHz and demonstrate the feasibility of a hard-switched dc-dc converter operating at this frequency.     

MEMS technology integrated in the CMOS back end

The Nanomech? MEMS technology platform which implements arrays of MEMS devices embedded inside the CMOS back end is described. The key advantages of this integration approach are described in terms of achieving a reliable MEMS technology process within competitive cost requirements, without any need for dedicated process, material and packaging development. The choice of materials is also providing a strong and reliable technology for harsh environment applications where cost is also a key. Data is shown providing a broad picture of the Nanomech? technology and its potentials for applications.     

Pressureless Bonding Using Sputtered Ag Thin Films

To improve the performance and reliability of power electronic devices, particularly those built around next-generation wide-bandgap semiconductors such as SiC and GaN, the bonding method used for packaging must change from soldering to solderless technology. Because traditional solders are problematic in the harsh operating conditions expected for emerging high-temperature power devices, we propose a new bonding method in this paper, namely a pressureless, low-temperature bonding process in air, using abnormal grain growth on sputtered Ag thin films to realize extremely high temperature resistance. To investigate the mechanisms of this bonding process, we characterized the microstructural changes in the Ag films over various bonding temperatures and times. We measured the bonding properties of the specimens by a die-shear strength test, as well as by x-ray diffraction measurements of the residual stress in the Ag films to show how the microstructural developments were essential to the bonding technology. Sound bonds with high die strength can be achieved only with abnormal grain growth at optimum bonding temperature and time. Pressureless bonding allows for production of reliable high-temperature power devices for a wide variety of industrial, energy, and environmental applications.     

SiC电力电子器件研究现状及新进展

由于硅材料本身的限制,传统硅电力电子器件性能已经接近其极限,碳化硅(SiC)器件的高功率、高效率、耐高温、抗辐照等优势逐渐突显,成为电力电子器件一个新的发展方向.综述了SiC材料、SiC电力电子器件、SiC模块及关键工艺的研究现状,重点从材料、器件结构、制备工艺等方面阐述了SiC二极管、金属氧化物半导体场效应晶体管(MOSFET)、结晶型场效应晶体管(JFET)、双极结型晶体管(BJT)、绝缘栅双极晶体管(IGBT)及模块的研究进展.概述了SiC材料、SiC电力电子器件及模块的商品化情况,最后对SiC材料及器件的发展趋势进行了展望.     

Microelectromechanical systems and system-on-chip connectivity

The interconnection of microelectromechanical systems (MEMS) and other devices to a system-on-chip (SoC) implementation is described. MEMS technology can be used to fabricate both application specific devices and the associated micropackaging system that will allow for the integration of devices or circuits, made with non-compatible technologies, with a SoC environment. In the primary example presented, MEMS technology has been used to develop an acoustical array sensor for a hearing instrument application and also to provide a custom micropackaging solution suitable for in-the-ear canal implantation. A MEMS based modular micropackaging solution consisting of MEMS socket submodules and an insertable/removable microbus card has been developed to provide the necessary packaging and connectivity requirements. The modular socket concept can also be used for many other purposes, such as temporarily connecting a CMOS die to a SoC implementation of a die tester using MEMS based cantilevered bridge-type microspring contacts to provide connectivity to the die under test.     

Advances in pulsed-laser-deposited AIN thin films for high-temperature capping, device passivation, and piezoelectric-based RF MEMS/NEMS resonator applications

In this paper we report recent advances in pulsed-laser-deposited AIN thin films for high-temperature capping of SiC, passivation of SiC-based devices, and fabrication of a piezoelectric MEMS/NEMS resonator on Pt-metallized SiO₂/Si. The AlN films grown using the reactive laser ablation technique were found to be highly stoichiometric, dense with an optical band gap of 6.2 eV, and with a surface smoothness of less than 1 nm. A low-temperature buffer-layer approach was used to reduce the lattice and thermal mismatch strains. The dependence of the quality of AlN thin films and its characteristics as a function of processing parameters are discussed. Due to high crystallinity, near-perfect stoichiometry, and high packing density, pulsed-laser-deposited AlN thin films show a tendency to withstand high temperatures up to 1600°C, and which enables it to be used as an anneal capping layer for SiC wafers for removing ion-implantation damage and dopant activation. The laser-deposited AlN thin films show conformal coverage on SiC-based devices and exhibit an electrical break-down strength of 1.66 MV/cm up to 350°C when used as an insulator in Ni/AlN/SiC metal-insulator-semiconductor (MIS) devices. Pulsed laser deposition (PLD) AlN films grown on Pt/SiO₂/Si (100) substrates for radio-frequency microelectrical and mechanical systems and nanoelectrical and mechanical systems (MEMS and NEMS) demonstrated resonators having high Q values ranging from 8,000 to 17,000 in the frequency range of 2.5–0.45 MHz. AlN thin films were characterized by x-ray diffraction, Rutherford backscattering spectrometry (in normal and oxygen resonance mode), atomic force microscopy, ultraviolet (UV)-visible spectroscopy, and scanning electron microscopy. Applications exploiting characteristics of high bandgap, high bond strength, excellent piezoelectric characteristics, extremely high chemical inertness, high electrical resistivity, high breakdown strength, and high thermal stability of the pulsed-laser-deposited thin films have been discussed in the context of emerging developments of SiC power devices, for high-temperature electronics, and for radio frequency (RF) MEMS.     

Thermal modeling and measurement of AlGaN-GaN HFETs built on sapphire and SiC substrates

We present thermal modeling and measurement results of AlGaN-GaN heterojunction field effect transistors fabricated on sapphire and SiC substrates, respectively. The device structures are identical except for the substrate material used to grow the AlGaN-GaN heterostructure. One objective is to study the effect of substrate material on the thermal and electrical performance of the resulting devices. To compute the temperature profiles, in-house PAMICE code developed for a three-dimensional structure was used. To measure the temperatures on the chip surface, nematic liquid crystal thermography was used. This technique is nondestructive and can be performed in realtime during device operation. It has submicrometer spatial resolution and /spl plusmn/1/spl deg/C temperature accuracy. The measured temperatures agree well with the calculated ones. The relationship between the measured temperature and power is almost linear for both types of devices. The junction-to-case thermal resistance of the device fabricated on sapphire substrate is 4.4 times that of the device built on SiC substrate.