Uncooled multimirror broad-band infrared microbolometers

A new generation of microbolometers were designed, fabricated and tested for the NASA CERES (Clouds and the Earth's Radiant Energy System) instrument to measure the radiation flux at the Earth's surface and the radiant energy now within the atmosphere. These detectors are designed to measure the earth radiances in three spectral channels consisting of a short wave channel of 0.3 to 5 /spl mu/m, a wide-band channel of 0.3 to 100 /spl mu/m and a window channel from 8 to 12 /spl mu/m each housing a 1.5 mm x 1.5 mm microbolometers or alternatively 400 /spl mu/m x 400 mm microbolometers in a 1 /spl times/ 4 array of detectors in each of the three wavelength bands, thus yielding a total of 12 channels. The microbolometers were fabricated by radio frequency (RF) magnetron sputtering at ambient temperature, using polyimide sacrificial layers and standard micromachining techniques. A semiconducting YBaCuO thermometer was employed. A double micromirror structure with multiple resonance cavities was designed to achieve a relatively uniform absorption from 0.3 to 100 /spl mu/m wavelength. Surface micromachining techniques in conjunction with a polyimide sacrificial layer were utilized to create a gap underneath the detector and the Si/sub 3/N/sub 4/ bridge layer. The temperature coefficient of resistance was measured to be -2.8%/K. The voltage responsivities were over 10/sup 3/ V/W, detectivities above 10/sup 8/ cm Hz/sup 1/2//W, noise equivalent power less than 4 /spl times/ 10/sup -10/W/Hz/sup 1/2/ and thermal time constant less than 15 ms.     

IR uncooled bolometers based on amorphous Ge/sub x/Si/sub 1-x/O/sub y/ on silicon micromachined structures

In this work, we present the fabrication of bulk micromachined microbolometers made of amorphous germanium-silicon-oxygen compounds (Ge/sub x/Si/sub 1-x/O/sub y/) grown by reactive sputtering of a Ge/sub 0.85/Si/sub 0.15/ target. We describe the complete procedure for fabricating thermally isolated microbolometers consisting of Ge/sub x/Si/sub 1-x/O/sub y/ sensing films deposited on sputtered silicon dioxide membranes suspended over a silicon substrate. The electrical properties of the sensitive material are set by controlling the deposition parameters of the sputtering technique. Under optimum deposition conditions, Ge/sub x/Si/sub 1-x/O/sub y/ layers with moderate electrical resistivity and thermal coefficient at room temperature as high as -4.2% /spl middot/ K/sup -1/ can be obtained. Isolated structures measured at atmospheric pressure in air have a thermal conductance of 3 /spl times/ 10/sup -6/ W /spl middot/ K/sup -1/ and a thermal capacitance of 6/spl middot/10/sup -9/ W /spl middot/ s /spl middot/ K/sup -1/, yielding a response time of 1.8 ms. Bolometers with an IR responsivity of 380 V /spl middot/ W/sup -1/ and a NEDT of 3.85 K at 100 nA bias current are obtained. The use of sputtered films allows designing a fully low-temperature fabrication process, wholly compatible with silicon integrated circuit technologies.     

High-Q single crystal silicon HARPSS capacitive beam resonators with self-aligned sub-100-nm transduction gaps

This paper reports on the fabrication and characterization of high-quality factor (Q) single crystal silicon (SCS) in-plane capacitive beam resonators with sub-100 nm to submicron transduction gaps using the HARPSS process. The resonating element is made of single crystal silicon while the drive and sense electrodes are made of trench-refilled polysilicon, yielding an all-silicon capacitive microresonator. The fabricated SCS resonators are 20-40 /spl mu/m thick and have self-aligned capacitive gaps. Vertical gaps as small as 80 nm in between 20 /spl mu/m thick silicon structures have been demonstrated in this work. A large number of clamped-free and clamped-clamped beam resonators were fabricated. Quality factors as high as 177000 for a 19 kHz clamped-free beam and 74000 for an 80 kHz clamped-clamped beam were measured under 1 mtorr vacuum. Clamped-clamped beam resonators were operated at their higher resonance modes (up to the fifth mode); a resonance frequency of 12 MHz was observed for the fifth mode of a clamped-clamped beam with the fundamental mode frequency of 0.91 MHz. Electrostatic tuning characteristics of the resonators have been measured and compared to the theoretical values. The measured Q values of the clamped-clamped beam resonators are within 20% of the fundamental thermoelastic damping limits (Q/sub TED/) obtained from finite element analysis.     

Polymer-based cantilevers with integrated electrodes

An innovative release method of polymer cantilevers with embedded integrated metal electrodes is presented. The fabrication is based on the lithographic patterning of the electrode layout on a wafer surface, covered by two layers of SU-8 polymer: a 10-/spl mu/m-thick photo-structured layer for the cantilever, and a 200-/spl mu/m-thick layer for the chip body. The releasing method is based on dry etching of a 2-/spl mu/m-thick sacrificial polysilicon layer. Devices with complex electrode layout embedded in free-standing 500-/spl mu/m-long and 100-/spl mu/m-wide SU-8 cantilever were fabricated and tested. We have optimized major fabrication steps such as the optimization of the SU-8 chip geometry for reduced residual stress and for enhanced underetching, and by defining multiple metal layers [titanium (Ti), aluminum (Al), bismuth (Bi)] for improved adhesion between metallic electrodes and polymer. The process was validated for a miniature 2/spl times/2 /spl mu/m/sup 2/ Hall-sensor integrated at the apex of a polymer microcantilever for scanning magnetic field sensing. The cantilever has a spring constant of /spl cong/1 N/m and a resonance frequency of /spl cong/17 kHz. Galvanometric characterization of the Hall sensor showed an input/output resistance of 200/spl Omega/, a device sensitivity of 0.05 V/AT and a minimum detectable magnetic flux density of 9 /spl mu/T/Hz/sup 1/2/ at frequencies above 1 kHz at room temperature. Quantitative magnetic field measurements of a microcoil were performed. The generic method allows for a stable integration of electrodes into polymers MEMS and it can readily be used for other types of microsensors where conducting metal electrodes are integrated in cantilevers for advanced scanning probe sensing applications.     

An in-plane high-sensitivity, low-noise micro-g silicon accelerometer with CMOS readout circuitry

A high-sensitivity, low-noise in-plane (lateral) capacitive silicon microaccelerometer utilizing a combined surface and bulk micromachining technology is reported. The accelerometer utilizes a 0.5-mm-thick, 2.4/spl times/1.0 mm/sup 2/ proof-mass and high aspect-ratio vertical polysilicon sensing electrodes fabricated using a trench refill process. The electrodes are separated from the proof-mass by a 1.1-/spl mu/m sensing gap formed using a sacrificial oxide layer. The measured device sensitivity is 5.6 pF/g. A CMOS readout circuit utilizing a switched-capacitor front-end /spl Sigma/-/spl Delta/ modulator operating at 1 MHz with chopper stabilization and correlated double sampling technique, can resolve a capacitance of 10 aF over a dynamic range of 120 dB in a 1 Hz BW. The measured input referred noise floor of the accelerometer-CMOS interface circuit is 1.6/spl mu/g//spl radic/Hz in atmosphere.     

A monolithic three-axis micro-g micromachined silicon capacitive accelerometer

A monolithic three-axis micro-g resolution silicon capacitive accelerometer system utilizing a combined surface and bulk micromachining technology is demonstrated. The accelerometer system consists of three individual single-axis accelerometers fabricated in a single substrate using a common fabrication process. All three devices have 475-/spl mu/m-thick silicon proof-mass, large area polysilicon sense/drive electrodes, and small sensing gap (<1.5 /spl mu/m) formed by a2004 sacrificial oxide layer. The fabricated accelerometer is 7/spl times/9 mm/sup 2/ in size, has 100 Hz bandwidth, >/spl sim/5 pF/g measured sensitivity and calculated sub-/spl mu/g//spl radic/Hz mechanical noise floor for all three axes. The total measured noise floor of the hybrid accelerometer assembled with a CMOS interface circuit is 1.60 /spl mu/g//spl radic/Hz (>1.5 kHz) and 1.08 /spl mu/g//spl radic/Hz (>600 Hz) for in-plane and out-of-plane devices, respectively.     

调相谱检测技术下谐振式光纤陀螺实验研究

谐振式光纤陀螺(R-FOG)是新一代光学传感器的代表.提出一种基于调相谱检测技术的R-FOG开环系统.作为核心敏感部件的谐振腔是由长度为5.5 m的保偏光纤和耦合系数为20%的保偏耦合器组成.谐振腔直径为0.1 m.根据测试其谐振曲线,得到该谐振腔的自由谱宽、半高全宽、清晰度以及谐振深度分别为35.7 MHz、2.21 MHz、16.2和0.95.由上述谐振腔参数计算得到该系统的极限灵敏度为4×10-7rad/s.利用声光调制器在R-FOG顺时针和逆时针光路中引入不同的频率差,用于等效陀螺转动引起的Sagnac频差,得到了陀螺的模拟开环响应曲线.根据得到的等效输出响应曲线,计算出该系统的动态范围可达 13.5 rad/s到-13.5 rad/s.由开环响应曲线中得到系统的检测灵敏度为0.03 rad/s;采取措施克服系统中的噪声源,可以进一步提高系统的检测灵敏度.     

基于机载光电成像系统光学铰链离轴的伺服抗扰算法设计

在小型化机载光电成像系统中,光学铰链与伺服框架轴非正交的离轴设计,给光轴指向控制及卸载飞机扰动的稳定控制带来了一定的困难。为了解决这一问题,系统控制回路采取半捷联设计,通过使用经微分处理后的伺服框架角信号,与叠加了经抗扰算法处理的飞机载体三轴角速度信号共同作为稳定回路的期望值,再进行匹配滤波。对比采用陀螺信号反馈的直接稳定控制回路具有相似的稳定精度。     

Post-CMOS-Compatible Aluminum Nitride Resonant MEMS Accelerometers

This paper describes the development of aluminum nitride (AlN) resonant accelerometers that can be integrated directly over foundry CMOS circuitry. Acceleration is measured by a change in resonant frequency of AlN double-ended tuning-fork (DETF) resonators. The DETF resonators and an attached proof mass are composed of a 1- $muhbox{m}$ -thick piezoelectric AlN layer. Utilizing piezoelectric coupling for the resonator drive and sense, DETFs at 890 kHz have been realized with quality factors $(Q)$ of 5090 and a maximum power handling of 1 $muhbox{W}$. The linear drive of the piezoelectric coupling reduces upconversion of $1/f$ amplifier noise into $1/f^{3}$ phase noise close to the oscillator carrier. This results in lower oscillator phase noise, $-$96 dBc/Hz at 100-Hz offset from the carrier, and improved sensor resolution when the DETF resonators are oscillated by the readout electronics. Attached to a 110-ng proof mass, the accelerometer microsystem has a measured sensitivity of 3.4 Hz/G and a resolution of 0.9 $hbox{mG}/surdhbox{Hz}$ from 10 to 200 Hz, where the accelerometer bandwidth is limited by the measurement setup. Theoretical calculations predict an upper limit on the accelerometer bandwidth of 1.4 kHz.$hfill$ [2008-0190]      

The wonham filter with random parameters: rate of convergence and error bounds

Let /spl alpha/(t) be a finite-state continuous-time Markov chain with generator Q=(q/sup ij/)/spl isin/R/sup m/spl times/m/ and state space M={z/sup i/,...,z/sup m/}, where z/sup 1/ for i/sub /spl middot//spl middot//spl middot//spl middot//m are distinct real numbers. When the state-space and the generator are known a priori, the best estimator of /spl alpha/(t) (in terms of mean square error) under noisy observation is the classical Wonham filter. This note addresses the estimation issue when values of the state-space or values of the generator are unknown a priori. In each case, we propose a (suboptimal) filter and prove its convergence to the desired Wonham filter under simple conditions. Moreover, we obtain the rate of convergence using both the mean square and the higher moment error bounds.     

Electrostatic microresonators from doped hydrogenated amorphous and nanocrystalline silicon thin films

This paper reports on the fabrication and characterization of flexural electrostatic microresonators based on doped thin-film hydrogenated amorphous and nanocrystalline silicon processed at temperatures below 110/spl deg/C using surface micromachining on glass substrates. The microelectromechanical structures are bridges made of either phosphorus-doped hydrogenated amorphous silicon (n/sup +/-a-Si:H) deposited by plasma-enhanced chemical vapor deposition (PECVD) or boron-doped hydrogenated nanocrystalline silicon (p/sup +/-nc-Si:H) deposited by hot-wire chemical vapor deposition (HWCVD). The microbridges, which are suspended over an aluminum (Al) gate electrode, are electrostatically actuated and the mechanical resonance is detected in vacuum using an optical detection method. The resonance frequency and energy dissipation mechanisms involved in thin-film silicon based microresonators are studied as a function of the geometrical dimensions of the structures. Resonance frequencies up to 36 MHz are observed and a Young's modulus of 147 GPa is extracted for n/sup +/-a-Si:H, and of 165 GPa for the p/sup +/-nc-Si:H films. Quality factors as high as 5000 and 2000 are observed for the n/sup +/-a-Si:H and p/sup +/-nc-Si:H resonators, respectively, and are limited by surface losses. The effect on the resonance frequency and quality factor of depositing a metal layer on the thin-film silicon structural layer is studied.     

A water-immersible 2-axis scanning mirror microsystem for ultrasound andha photoacoustic microscopic imaging applications

Fast scanning is highly desired for both ultrasound and photoacoustic microscopic imaging, whereas the liquid environment required for acoustic propagation limits the usage of traditional microelectromechanical systems (MEMS) scanning mirrors. Here, a new water-immersible scanning mirror microsystem has been designed, fabricated and tested. To achieve reliable underwater scanning, flexible polymer torsion hinges fabricated by laser micromachining were used to support the reflective silicon mirror plate. Two efficient electromagnetic microactuators consisting of compact RF choke inductors and high-strength neodymium magnet disc were constructed to drive the silicon mirror plate around a fast axis and a slow axis. The performance of this water-immersible scanning mirror microsystem in both air and water were tested using the laser tracing method. For the fast axis, the resonance frequency reached 224 Hz in air and 164 Hz in water, respectively. The scanning angles in both air and water under ±16 V DC driving were ±12°. The scanning angles in air and water under ±10 V AC driving (at the resonance frequencies) were ±13.6° and ±10°. For the slow axis, the resonance frequency reached 55 Hz in air and 38 Hz in water, respectively. The scanning angles in both air and water under ±10 V DC driving were ±6.5°. The scanning angles in air and water under ±10 V AC driving (at the resonance frequencies) were ±8.5° and ±6°. The feasibility of using such a water-immersible scanning mirror microsystem for scanning ultrasound microscopic imaging has been demonstrated with a 25-MHz ultrasound pulse/echo system and a target consisting of three optical fibers.     

谐振式光纤陀螺环路锁频技术研究

谐振式光纤陀螺(Resonator Fiber Optic Gyro,R-FOG)是基于Sagnac效应产生的谐振频率差来测量旋转角速率的一种新型光学传感器.对基于调相谱检测技术R-FOG系统中的环路频率锁定技术进行了研究.通过对系统光学回路和处理电路部分分别进行建模,利用反馈控制系统理论,分析了整个环路的传递函数,得到了整个环路起主导作用的简化模型.利用该简化模型,在一定的光学回路参数条件下,得到了处理电路的最佳锁定参数,并进一步在实验中得到验证.     

三轴光纤陀螺测控装置

光纤陀螺测控装备主要是检测陀螺的性能指标,保障陀螺的精确度和稳定性.论文介绍了一套三轴光纤陀螺测控装置,采用美国NI公司生产的计数器卡和多功能数据采集卡以及研华公司的工控机搭建硬件平台,采用LabVIEW编程语言实现软件部分的测试功能.三轴光纤陀螺测控装置通过主控计算机对三轴转台的运动模式进行控制,给被测三轴光纤陀螺提供所需的电源和时钟信号,同时对产品27V供电电压和电流进行实时监测和保护,并对产品的六路输入、输出信号进行隔离、调理,通过设定的测试程序自动采集并存储,然后对测试数据进行建模和计算,获得被测产品的各项性能参数.从而实现了三轴光纤陀螺的性能指标测试,具有良好的可视化人机交互界面.     

Output regulation of periodic signals for DPS: an infinite-dimensional signal Generator

In this note, we consider output regulation and disturbance rejection of periodic signals via state feedback in the setting of exponentially stabilizable linear infinite-dimensional systems. We show that if an infinite-dimensional exogenous system is generating periodic reference signals, solvability of the state feedback regulation problem is equivalent to solvability of the so called equations. This result allows us to consider asymptotic tracking of periodic reference signals which only have absolutely summable Fourier coefficients, while in related existing work the reference signals are confined to be infinitely smooth. We also discuss solution of the regulator equations and construct the actual feedback law to achieve output regulation in the single-input-single-output (SISO) case: The output regulation problem is solvable if the transfer function of the stabilized plant does not have zeros at the frequencies i/spl omega//sub n/ of the periodic reference signals and if the sequence ([CR(i/spl omega//sub n/, A+BK)B]/sup -1/ /spl times/(Q/spl phi//sub n/-CR(i/spl omega//sub n/, A+BK)P/spl phi//sub n/)) /sub n/spl isin/z//spl isin/l/sup n2/. A one-dimensional heat equation is used as an illustrative example.     

谐振式光纤陀螺偏振波动噪声的温度特性

光纤环形谐振腔环境温度变化带来的偏振波动噪声是影响谐振式光纤陀螺检测精度的主要光学噪声源之一,通过控制谐振腔温度,可以使偏振波动噪声得到有效抑制.为了抑制偏振波动噪声,减小R-FOG精度受FRR温度变化的影响,从理论上分析了谐振腔温度变化对谐振曲线、解调曲线的影响;针对不同温度下光纤环的谐振特性、解调曲线特性、陀螺零偏及零偏稳定性开展了实验,并对实验结果进行了分析.结果表明,谐振腔的工作温度为27.00℃时,两本征偏振态相距最远,总谐振曲线关于谐振频率点对称,谐振频率点检测误差可以忽略;陀螺零偏稳定性近似等于谐振腔温度为25.50℃时的1/100,在150 s的采样时间内达到0.07°/s,陀螺检测精度得到很大提高.     

A micromechanical flow sensor for microfluidic applications

We fabricated a microfluidic flow meter and measured its response to fluid flow in a microfluidic channel. The flow meter consisted of a micromechanical plate, coupled to a laser deflection system to measure the deflection of the plate during fluid flow. The 100 /spl mu/m square plate was clamped on three sides and elevated 3 /spl mu/m above the bottom surface of the channel. The response of the flow meter was measured for flow rates, ranging from 2.1 to 41.7 /spl mu/L/min. Several fluids, with dynamic viscosities ranging from 0.8 to 4.5/spl times/10/sup -3/ N/m, were flowed through the channels. Flow was established in the microfluidic channel by means of a syringe pump, and the angular deflection of the plate monitored. The response of the plate to flow of a fluid with a viscosity of 4.5/spl times/10/sup -3/ N/m was linear for all flow rates, while the plate responded linearly to flow rates less than 4.2 /spl mu/L/min of solutions with lower dynamic viscosities. The sensitivity of the deflection of the plate to fluid flow was 12.5/spl plusmn/0.2 /spl mu/rad/(/spl mu/L/min), for a fluid with a viscosity of 4.5/spl times/10/sup -3/ N/m. The encapsulated plate provided local flow information along the length of a microfluidic channel.     

光电加速度传感器非对称3×3解调系统SOPC设计

介绍了集成光学芯片、光纤质量块简谐振子和可编程片上系统(SOPC)混合集成光学加速度计的设计方法.采用基于3×3耦合器的干涉系统进行光相位的调制.研究了在非对称情况下的解调算法,从而解决了由于非对称性造成解调结果失真的问题.应用SOPC技术设计和实现数字信号处理系统,实现信号处理与数据传输的并行工作,实验证明该系统可以实时、线性地跟踪到加速度信号.实际测量灵敏度为4.62 V/gn,工作频带为1-1 066 Hz.     

Micromachined Acoustic Resonant Mass Sensor

This paper describes a highly sensitive, film bulk acoustic resonator (FBAR) mass sensor (built on a micromachined silicon-nitride diaphragm with a piezoelectric thin film and Al electrodes) that can operate in vapor and liquid. The sensitivity of the device to mass change on its surface has been investigated by having various thicknesses of silicon-nitride support layer and also of Al layer. The sensor is measured to have a mass sensitivity of 726 cm$^2$/g, which is about 50 times that of a typical quartz crystal microbalance (QCM). In vapor, the sensor (operating at around 1 GHz and having a relatively high quality (Q) factor of 200–300) shows a minimum detectable frequency shift of about 400 Hz, which corresponds to a mass change of$10^-9$g/cm$^2$on the sensor surface, comparable with that detectable by a QCM. In liquid, though the Q usually drops more than an order of magnitude, we obtain a Q of 40 at 2 GHz by using a second harmonic resonance of the resonator. And with the Q, a minimum 5 ppm resonant frequency shift can be detected, which corresponds to$10^- 8$g/cm$^2$change on the sensor surface.hfillhbox[1374]     

基于数字信号处理的干涉型光纤传感器检测系统的研究与设计

本文基于数字信号处理技术,对干涉型光纤传感器数字检测系统进行研究与设计.分析了合成外差解调算法的基本原理,描述了检测系统的整体构架.重点讨论了采用DSP Builder技术对解调部分的设计,实现解调算法的数字信号处理和智能化数据传输接口并行工作,使系统实时、线性地跟踪到被测信号.通过实验测试,该解调系统的工作频带约为10 Hz～1kHz,具有较好的抗干扰性.