Applications and processing of SiGe and SiGe:C for high-speed HBT devices

The continued growth of high-speed-digital data transmission and wireless communications technology has motivated increased integration levels for ICs serving these markets. Further, the increasing use of portable wireless communications tools requiring long battery lifetimes necessitates low power consumption by the semiconductor devices within these tools. The SiGe and SiGe:C materials systems provide solutions to both of these market needs in that they are fully monolithically integratible with Si BiCMOS technology. Also, the use of SiGe or SiGe:C HBTs for the high-frequency bipolar elements in the BiCMOS circuits results in greatly decreased power consumption when compared to Si BJT devices.Either a DFT (graded Ge content across the base) or a true HBT (constant Ge content across the base) bipolar transistor can be fabricated using SiGe or SiGe:C. Historically, the graded profile has been favored in the industry since the average Ge content in the pseudomorphic base is less than that of a true HBT and, therefore, the DFT is tolerant of higher thermal budget processing after deposition of the base. The inclusion of small amounts of C (e.g. <0.5%) in SiGe is effective in suppressing the diffusion of B such that very narrow extremely heavily doped base regions can be built. Thus the f_T and f_max of a SiGe:C HBT/DFT are capable of being much higher than that of a SiGe HBT/DFT.The growth of the base region can be accomplished by either nonselective mixed deposition or by selective epitaxy. The nonselective process has the advantage of reduced complexity, higher deposition rate and, therefore, higher productivity than the selective epitaxy process. The selective epi process, however, requires fewer changes to an existing fabrication sequence in order to accommodate SiGe or SiGe:C HBT/DFT devices into the BiCMOS circuit.     

四甲基氢氧化铵在MEMS中的应用

通过各向异性腐蚀硅杯实验,研究了四甲基氢氧化铵（TMAH）腐蚀液的特性,包括硅（100）面腐蚀速率与溶液浓度、温度的关系,不同腐蚀条件下硅杯的表面状况,并确定了制作硅杯的最佳工艺条件。通过测试硅杯结构多晶硅压力传感器的输出特性,证明了TMAH确实是一种性能优良的各向异性腐蚀剂。     

Integration of MOSFETs with SiGe dots as stressor material

The potentials of using silicon-germanium dots as stressor material in MOSFETs are evaluated with respect to integration in today’s production processes. Work is reviewed that has lead to the fabrication of the first experimental n-channel MOSFETs on SiGe dots, referred to as DotFETs, in a low-complexity, custom-made low-temperature process where the dot is preserved during the entire device processing. The SiGe dots were grown in large regular arrays in a Stranski-Krastanow (S-K) mode and used to induce biaxial tensile strain in a silicon capping-layer. The DotFETs are processed with the main gate-segment above the strained Si layer on a single dot. To prevent intermixing of the Si/SiGe/Si structure, the processing temperature is kept below 400 °C by using excimer-laser annealing to activate the source/drain implants that are self-aligned to a metal gate. The crystallinity of the structure is preserved throughout the processing and, compared to reference devices, an average increase in drain current up to 22.5% is obtained. The experimental results are substantiated by extensive simulations and modeling of the strain levels in capped dots and the corresponding mobility enhancement achievable with DotFETs. The concept of SiGe dots overgrown with a Si layer is also considered for use as a starting structure for silicon-on-nothing (SON) technology where the dot should be removed after the formation of the gate-stack and the strain for mobility enhancement should be preserved (and possibly increased) via the other device layers.     

激光在MEMS键合技术中的应用

键合技术已经广泛地应用于微电子机械系统(MEMS)领域,但传统的键合技术由于其缺点,限制了其应用范围,而激光以其独特的优势在键合技术中得到了人们的重视.文章介绍了激光在键合技术中的应用及其原理,以及今后发展的方向.     

脉冲激光MEMS加工技术

阐述了脉冲激光微加工技术及其在微机电系统 (MEMS)加工中的应用。脉冲激光微加工技术能够制作出三维微型结构并具有微米 /亚微米加工精度 ,且适用于多种材料 ,与传统的微细加工技术如光刻、刻蚀、体硅和面硅加工技术等相比具有其独到之处。进一步阐述了基于激光烧蚀的脉冲激光直接微加工技术、激光 LIGA技术、激光辅助沉积与刻蚀技术以及MEMS的激光辅助操控及装配技术     

The separation of generation lifetimes of Si and SiGe using capacitance-transient measurements on MOS capacitors formed by plasma anodisation of Si:Si0.9Ge0.1:Si substrates

A simple technique leading to the measurement of minority carrier lifetimes of UHV compatible LPCVD Si and SiGe by C–t depth profiling of Metal:Oxide:Si:SiGe:Si structures is reported. A high quality gate oxide is realised by low temperature (<100°C) plasma anodisation thereby reducing any oxidation effects on the underlying epitaxial layer quality. Capacitance response times were observed for an impurity concentration of 2.5×10¹⁷ cm⁻³, giving rise to generation lifetimes of the Si and Si_0.9Ge_0.1 of >0.55 and 2.6 μs respectively, reflective of very high quality epitaxial semiconductor material.     

脉冲激光微加工技术在MEMS中的应用

介绍了脉冲激光微加工技术及其在微机电系统(MEMS)加工中的应用。脉冲激光微加工技术能够制作出三维微型结构并具有微米／亚微米加工精度，且适用于多种材料，与传统的微细加工技术(光刻、刻蚀、体硅和面硅加工技术等)相比具有其独到之处。阐述了基于激光烧蚀的脉冲激光直接微加工技术、激光-LIGA技术、激光辅助沉积与刻蚀技术以及MEMS的激光辅助操控及装配技术。     

基于非晶锗热电阻的柔性MEMS流速传感器的设计与仿真

针对铂等常用金属热敏材料电阻温度系数(TCR)不高,导致热式MEMS流速传感器宽量程测量时功耗高的问题,设计了 一种基于非晶锗(a-Ge)薄膜热电阻的低功耗、宽量程柔性MEMS流速传感器.非晶锗热电阻材料具有较高的TCR系数(约为-0.02/K)和室温电阻率(5Ω·m),传感器在较低的工作温差和功耗下可获得宽量程的流速测量.阐述了该柔性MEMS流速传感器的设计结构、工作原理、3D有限元建模和热-流场仿真结果.利用聚酰亚胺衬底空腔膜上的四个非晶锗热电阻同时作为自加热热源和测温元件.四个非晶锗热电阻组成一个惠斯通电桥,同时结合热损失和热温差原理来实现宽量程流速测量和测向.仿真结果表明,惠斯通电桥采用恒电流供电只需120μA,使得非晶锗热阻的工作温度与环境温度之间的温差不高于6 K,就可对0～50 m/s范围内的流速进行测量,且功耗在1.368 mW以内.该柔性流速传感器易于采用MEMS技术批量制造,可贴于曲面应用,非常适于物联网等低功耗流速传感领域.     

The HARPSS process for fabrication of precision MEMS inertial sensors

The high aspect-ratio combined poly- and single-crystal silicon micromachining technology (HARPSS) and its application to fabrication of precision MEMS inertial sensors are presented. HARPSS is a single wafer, all silicon, front-side release process which is capable of producing 10–100's of microns thick, electrically isolated, 3-D poly- and single-crystalline silicon microstructures with various size air-gaps ranging from sub-micron to tens of microns. High aspect-ratio (>50:1) polysilicon structures are created by refilling 100's of microns deep trenches with polysilicon deposited over a sacrificial oxide layer. This technology provides features required for precision micromachined inertial sensors. The all-silicon feature of this technology improves long term stability and temperature sensitivity while fabrication of large area, vertical electrodes with sub-micron gap spacing will increase the sensitivity by orders of magnitude.     

MEMS划片技术的现状与技术革新

MEMS独特的结构和特性,给划片工艺带来了巨大的挑战.介绍了传统砂轮划片技术在MEMS芯片生产中的局限性,指出了隐形激光划片技术的优越性,综述了激光划片技术在MEMS划片中的应用,对几种较成熟的先进激光划片技术进行了比较,对各自的工作原理、特点、工序作了重点阐述,并对MEMS划片技术的发展前景作了展望.     

用于MEMS的硅湿法深槽刻蚀技术研究

针对用于MEMS的硅湿法深槽刻蚀技术,对KOH腐蚀液的配方、掩蔽技术等关键技术进行了研究,获得了优化的KOH腐蚀条件;利用该技术,成功地刻蚀出深度高达315μm、保护区域完好的深槽。为硅基MEMS体加工获得微机械结构提供了一个好方法。     

X波段MEMS膜开关的阻抗分析模型

射频微机械(RF MEMS)开关由于其优越的高频特性在微波和毫米波电路中表现出巨大的应用前景.但是目前对微机械开关的研究主要都集中在开关梁的结构设计和力学分析上,对开关的电磁特性的研究,尤其是开关高频阻抗匹配分析的研究与验证比较少.本文在高频传输线研究的基础上,推导出微机械开关的“开态”阻抗匹配模型,并利用HFSS软件对开关的高频特性进行模拟.其结果有助于设计高性能的RF MEMS开关.     

一种用于微拉伸系统的MEMS弹簧设计与制作

针对微拉伸测试系统支撑梁因塑性变形带来的误差,采用UV-LIGA技术制备出S型支撑弹簧来代替刚性梁,这样即可测量大变形薄膜的力学性能.实验结果表明,用UV-LIGA工艺制备的Ni金属S形弹簧具有良好的均匀性,在较大的变形范围内有很好的线弹性.     

Silicon periodic nano-structures obtained by laser exposure of nano-wires

Silicon nano-wires were fabricated using thin Silicon on Insulator (SOI) wafers and a combination of anisotropic wet etching by Tetra-Methyl Ammonium Hydroxide (TMAH) and Local Oxidation of Silicon (LOCOS). These nano-wires were submitted to laser exposure using gas immersion laser doping (GILD). The result was the formation of either periodic nano-structures or silicon balls. Since the process uses very short laser pulses, it involves rapid melting and solidification of silicon. Hence, the observed periodicity is ascribed to Rayleigh instability, which involves surface tension effects in melted silicon.     

适用于MEMS动态测量的显微激光多普勒技术

介绍了一种利用激光多普勒(LD)技术和显微技术结合的微机电系统(MEMS)器件动态特性测量技术,所搭建的系统测量光斑直径小于1um,测量频率0～20MHz,平面外运动分辨率0．1nm,精度5nm,不确定度1nm描述了利用该系统对TMT(test motion target)器件的振动特性进行的测量实验,并对实验结果进行了分析,测得器件的共振频率为271Hz,最大振幅为0．246482566mm。     

EMC材料特性对MEMS加速度计封装可靠性的影响

采用有限元法分析了EMC(环氧模塑封材料)材料特性对MEMS(微电子机械系统)加速度计封装可靠性的影响.使用有限元软件ANSYS分别模拟了加速度计的输出电压、悬臂梁的挠度以及加速度计芯片的等效应力在温度循环载荷下的变化情况.结果发现,EMC的材料模式不同,MEMS加速度计的性能有明显差异.在使用EMC温度相关弹性模式和...     

替代晶振：解读SiTime全硅MEMS技术

电子系统设计高度集成和小体积化趋势要求时钟产品向小体积,薄型化方向发展,但在此过程中,传统石英或压电陶瓷材料的时钟产品受制于物理特性,其可靠性、精度和高性能之间的平衡很难保持,传统材料的易碎性,在厚度小于0.8mm时其抗冲击、震动能力都大受影响,使得传统材料的薄型化产品面临着高成本及低良率的问题。     

Embedded benzocyclobutene in silicon: An integrated fabrication process for electrical and thermal isolation in MEMS

This paper reports a novel fabrication process to develop planarized isolated islands of benzocyclobutene (BCB) polymer embedded in a silicon substrate. Embedded BCB in silicon (EBiS) can be used as an alternative to silicon dioxide in fabrication of electrostatic micromotors, microgenerators, and other microelectromechanical devices. EBiS takes advantage of the low dielectric constant and thermal conductivity of BCB polymers to develop electrical and thermal isolation integrated in silicon. The process involves conventional microfabrication techniques such as photolithography, deep reactive ion etching, and chemical mechanical planarization (CMP). We have characterized CMP of BCB polymers in detail since CMP is a key step in EBiS process. Atomic force microscopy (AFM) and elipsometry of blanket BCB films before and after CMP show that higher polishing down force pressure and speed lead to higher removal rate at the expense of higher surface roughness, non-uniformity, and scratch density. This is expected since BCB is a softer material compared to inorganic films such as silicon dioxide. We have observed that as the cure temperature of BCB increases beyond 200 °C, the CMP removal rate decreases drastically. The results from optical microscopy, scanning electron microscopy, and optical profilometry show excellent planarized surfaces on the EBiS islands. An average step height reduction of more than 95% was achieved after two BCB deposition and three CMP steps.     

One and two port piezoelectric higher order contour-mode MEMS resonators for mechanical signal processing

This paper reports on the design, fabrication and testing of novel one and two port piezoelectric higher order contour-mode MEMS resonators that can be employed in RF wireless communications as frequency reference elements or arranged in arrays to form banks of multi-frequency filters. The paper offers a comparison of one and two port resonant devices exhibiting frequencies approximately ranging from 200 to 800 MHz, quality factor of few thousands (1000–2500) and motional resistances ranging from 25 to 1000 Ω. Fundamental advantages and limitations of each solution are discussed. The reported experimental results focus on the response of a higher order one port resonator under different environmental conditions and a new class of two port contour resonators for narrow band filtering applications. Furthermore, an overview of novel frequency synthesis schemes that can be enabled by these contour-mode resonators is briefly presented.