Stress analysis in new improved differential vertical comb capacitive micro accelerometer using SOI technology

Microsystem Technologies - Recently a new improved differential vertical comb type capacitive accelerometer using silicon on insulator (SOI) technology reported having better performance than...     

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.     

Angular vertical comb actuators assembled on-chip using in-plane electrothermal actuators and latching mechanisms

We have designed, fabricated and tested self-aligned angular vertical comb-drive (AVC) actuators by on-chip assembly using in-plane electrothermal actuators and latching mechanisms. The on-chip assembly process is carried out by engaging latching mechanism connected to the torsion bars through the off-centered thinned down silicon beams. When the latching mechanism is fully engaged, the assembled AVC actuator forms permanent initial tilt angle by the retraction force of electrothermal actuators. The AVC actuators and latching mechanisms are fabricated on a silicon-on-insulator (SOI) wafer using three photomasks and three times of deep etch steps. The maximum optical scan angle of 30.7° is achieved at 4.56 kHz under the sinusoidal driving voltage of 0–80 V applied to the AVC actuator. After the reliability test performed by operating the actuator for 1.6 × 10⁸ cycles at its resonance, the measured optical scan angle variation and resonant frequency change were within 1.1% and 8 Hz, respectively, and the robustness of the latched mechanism was ensured.     

叉指式加速度计的一种仿真法分析

微电子机械系统的快速发展对其建模仿真也提出了较高要求。首先介绍了一种微电子机械系统原理级描述仿真方法,它基于成熟的微机械元件库,提供微器件的原理级描述,使得仿真更简单、更高效,但目前其适用范围有限。然后介绍了用这种方法分析叉指式微电容加速度计的结果。     

四相敏感元件测量三轴力的传感方法研究

三轴力传感器技术正在成为近年来的研究热点。研究一种利用四相敏感元件来测量三轴力的传感方法,并为三轴力的计算找到了一个通用的计算模型。通过对几种典型的基于力信号、电信号和光信号原理的三轴力传感器的实验结果进行分析,验证了利用四相敏感元件测量三轴力的可行性和可靠性。期望该方法能够对其他三轴力传感器的设计提供有益的帮助。     

A low voltage vertical comb RF MEMS switch

Design and simulations of a novel RF MEMS switch is reported as a solution to many RF wireless applications. A new comb structure for RF MEMS switch is proposed for low voltage and high frequency operations. Isolation degree and actuation voltage, both improved by the new structure. The mechanical and electromagnetic simulation results show better performance for this new switch compared to parallel plate switch. The simulation is done by the intellisuit and HFSS softwares. The Simulation results show that the actuation voltage is decreased by 13% and the linearity of the switch displacement with respect to the actuation voltage is improved by 22% compared to the parallel plate structure. The HFSS simulation results indicate an insertion loss better than 0.33 dB at 50 GHz and isolation greater than 13.4 dB at 50 GHz.     

基于三轴加速度计的桥涵防碰撞报警装置的设计

设计了一种基于三轴加速度计ADXL345的桥涵防碰撞报警装置,它能够及时检测桥涵限高门架的碰撞及倾斜情况,并将碰撞信息发送至远程监控端。将装置安装在限高门架上,一旦碰撞加速度超过系统设定阈值,加速度计产生中断信号,微控制器联网报警。由于装置安装环境的特殊性,系统必须是一个无源系统。电能依靠锂电池提供,为延长系统的使用周期,采用太阳能充电。为进一步减少系统能耗,对电源模块进行管理。电源模块的设计保证系统能稳定持久地运行。     

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.     

RETRACTED ARTICLE: A new structure and modeling of a three-axis MEMS capacitive accelerometer with high dynamic range and sensitivity

Microsystem Technologies - In this paper, a three-axis capacitor accelerator has been analyzed, modeled and optimized using micro-electromechanical systems technology. In the proposed structure,...     

三轴一体石英挠性加速度计标定数学建模与误差分析

为了提高加速度计标定精度,针对三轴一体石英挠性加速度计确定性误差特性和工程安装特点,基于笛卡尔空间坐标系之间的转换,推导加速度计坐标系与载体坐标系之间的转换矩阵,建立三种石英挠性加速度计线性标定数学模型.仿真和导航实验结果表明:三轴一体石英挠性加速度计标定数学模型误差引起捷联惯性导航系统速度误差、位置误差和姿态误差,且姿态误差和位置误差包含常值分量;所有误差均包含舒勒周期振荡和傅科周期振荡,傅科周期振荡调节舒勒周期振荡.     

Retraction Note: A new structure and modeling of a three-axis MEMS capacitive accelerometer with high dynamic range and sensitivity

Microsystem Technologies -     

加速度计标定用三轴摇摆台控制系统仿真与试验研究

针对加速度计测量对三轴摇摆台高精度要求,提出一种对其控制进行系统联合仿真的方法,并给出试验结果。在给出摇摆台数学模型的基础上,设计了摇摆台位置—速度—电流反馈的三环控制结构,并给出了利用ADAMS和Matlab协同仿真的控制结构图。仿真和试验结果表明：转台的转矩幅值波动小,位置信号的跟踪性能完全满足指标要求,可以实现加速度计的精确标定。     

A miniature in-plane piezoresistive MEMS accelerometer for detection of slider off-track motion in hard disk drives

A miniature in-plane pizoresistive MEMS accelerometer was designed, fabricated and characterized for detection of slider off-track motion in hard disk drives. The structure of the accelerometer consists of a central supporting beam and two stress-magnifying sensing beams. Under geometric constraints imposed by the trailing side of a pico slider, the accelerometer design was optimized to achieve approximately pure axial deformation in the sensing beams and a maximum sensitivity with a specified natural frequency of 300 kHz. Fabricated on a silicon-on-insulator (SOI) wafer, the accelerometer with a half Wheatstone bridge was wirebonded to external pads and interfaced with an amplifier circuit on a printed circuit board (PCB). The noise level, sensitivity, nonlinearity were characterized with vibration testing on a shaker. The miniature accelerometer (1 × 0.3 × 0.3 mm³) with a weight of only 0.2 mg offers a much higher resonant frequency with a comparable sensitivity compared with those in previous work.     

A self-aligned fabrication method of dual comb drive using multilayers SOI process for optical MEMS applications

A novel method for fabricating a self-aligned electrostatic dual comb drive using a multi-layer SOI process is developed. The present method utilizes four aligned masks, greatly simplify the existing SOI-MEMS fabrication methods in manufacturing optical MEMS devices. Here, the actuating structure consists of fixed combs and moving combs that are composed of single crystal silicon, nitride and polysilicon. One mask is used to provide a deep etching to etch polysilicon, nitride and single crystal silicon respectively. The nitride separates polysilicon and single crystal silicon and provides an additional dielectric for the purpose of producing bi- directional motion upon applying electrostatic forces. A dual comb drive actuator with optical structures was fabricated with the developed process. The actuator is capable of motion 250 nm downward and 480 nm upward with 30 V applied voltage at 4 kHz frequency. The dynamic characteristics of the first and the second resonant frequency of the dual comb-drive actuator are 10.5 kHz and 23 kHz respectively. Experimental results indicated that the measured data agreed well with simulation results using the ANSOFT Maxwell^® 2D field simulator, ANSYS^® and Coventor Ware^®.     

A new MEMS based variable capacitor using electrostatic vertical comb drive actuator and auxiliary cantilever beams

We have proposed a new wide tunable MEMS variable capacitor. In the proposed structure, an electrostatic vertical comb drive actuator is used to extend the tuning range. Moreover, the auxiliary cantilever-beams are used in the electrostatic comb drive actuator to delay the front sticking (Pull in) and increase the tunability. The effect of lateral gap distance between the fingers in the capacitance tunability is investigated. Not only a full review of electrostatic actuator portion is done but also the electric fields related to lateral gap changes are simulated by COMSOL software and its results are compared with theoretical results as well. The structure is calculated using MATLAB software. To verify, the calculated results are compared with simulated results using Intellisuite software. According to calculation and simulation results the achieved tuning range is 285%.

     

Surface- and bulk- micromachined two-dimensional scanner driven by angular vertical comb actuators

In this paper, we present the design, fabrication, and measurements of a two-dimensional (2-D) optical scanner with electrostatic angular vertical comb (AVC) actuators. The scanner is realized by combining a foundry-based surface-micromachining process (Multi-User MEMS Processes-MUMPs) with a three-mask deep-reactive ion-etching (DRIE) postfabrication process. The surface-micromachining provides versatile mechanical design and electrical interconnect while the bulk micromachining offers high-aspect ratio structures leading to flat mirrors and high-force, large-displacement actuators. The scanner achieves dc mechanical scanning ranges of /spl plusmn/6.2/spl deg/ (at 55 Vdc) and /spl plusmn/4.1/spl deg/ (at 50 Vdc) for the inner and outer gimbals, respectively. The resonant frequencies are 315 and 144 Hz for the inner and the outer axes, respectively. The 1-mm-diameter mirror has a radius of curvature of over 50 cm. [1454].     

A CMOS-MEMS mirror with curled-hinge comb drives

A micromirror achieves up to /spl plusmn/4.7/spl deg/ angular displacement with 18 Vdc by a comb-drive design that uses vertical angled offset of the comb fingers. Structures are made from a combination of CMOS interconnect layers and a thick underlying silicon layer. Electrical isolation of the silicon fingers is realized with a slight silicon undercut etch, which disconnects sufficiently narrow pieces of silicon under the CMOS microstructures. The 1 mm by 1 mm micromirror is made of an approximately 40 /spl mu/m-thick single-crystal silicon plate coated with aluminum from the CMOS interconnect stack. The mirror has a peak-to-peak curling of 0.5 /spl mu/m. Fabrication starts with a conventional CMOS process followed by dry-etch micromachining steps. There is no need for wafer bonding and accurate front-to-backside alignment. Such capability has potential applications in biomedical imaging, optical switches, optical scanners, interferometric systems, and vibratory gyroscopes.     

串联电极阵列压电传感技术自动检测病原体

以串联电极阵列压电石英晶体（SPQC）传感器为基础构建了一台8通道微生物自动检测仪。电极插入培养基检测溶液电导的变化。池常数k=0．05m,使用中性、低电导的氨基酸培养基（AaB）,电导控制灵敏度区间为550-600μs。利用拟合-微分的方法简单准确地得到频率检测时间（FDT）。对普通的金黄色葡萄球菌（S．aureus）和痢疾杆菌（S．dysenteriae）进行自动检测,结果表明：FDT和样品中细菌浓度呈线性关系（R〉0．99）,检测范围为10-10^6CFU·mL^-1。该方法准确度与国标的平板记数法相当（置信区间为95％）,但重现性更好,更稳定,灵敏度更高。     

Drop-on-demand printed microfluidics device with sensing electrodes using silver and PDMS reactive inks

For this work, a cure-in-place polydimethylsiloxane (PDMS) reactive ink was developed and its utility demonstrated by printing a complete microfluidic mixer with integrated electrodes to measure fluid conductivity, concentration, and mixing completeness. First, a parameter-space investigation was conducted to generate a set of PDMS inks and printing parameters compatible with drop-on-demand (DOD) printing constraints. Next, a microfluidic mixer was fabricated using DOD-printed silver reactive inks, PDMS reactive inks, and a low-temperature polyethylene glycol fugitive ink. Lastly, the device was calibrated and tested using NaCl solutions with concentrations ranging from 0.01 to 1.0 M to show that electrolyte concentration and mixing completeness can be accurately measured. Overall, this work demonstrates a set of reactive inks and processes to fabricate sophisticated microfluidic devices using low-cost inks and DOD printing techniques.