CMOS Monolithic Metal–Oxide Gas Sensor Microsystems

This paper presents two mixed-signal monolithic gas sensor microsystems fabricated in standard 0.8-$muhbox m$CMOS technology combined with post-CMOS micromachining to form the microhotplates. The on-chip microhotplates provide very high temperatures (between 200$^circ$C and 400$^circ$C), which are necessary for the normal operation of metal–oxide sensing layers. The first microsystem has a single-ended architecture comprising a microhotplate (diameter of 300$muhbox m$) and a digital proportional-integral-derivative (PID) microhotplate temperature controller. The second microsystem has a fully-differential architecture comprising an array of three microhotplates (diameter of 100$muhbox m$) and three digital PID microhotplate temperature controllers (one controller per microhotplate). The on-chip digital PID temperature controllers can accurately adjust the microhotplate temperatures up to 400$^circ$C with a resolution of 2$^circ$C. Further, both microsystems feature on-chip logarithmic converters for the readout of the metal–oxide resistors (which cover a measurement range between 1$hbox kOmega$and 10$hbox MOmega$), 10-bit A/D converters, anti-aliasing filters, 10-bit D/A converters,$I ^2 C$serial interfaces, and bulk-chip temperature sensors. Carbon monoxide (CO) concentrations in the sub-parts-per-million (ppm) range are detectable, and a resolution of 0.2 ppm CO has been achieved.     

A Linear Variable Differential Capacitive Transducer for Sensing Planar Angles

A linear variable differential capacitive transducer for the measurement of planar angles (from 0deg to 360deg) is presented in this paper. The sensor part of the transducer is made of parallel plates of standard and easy-to-fabricate shapes, and the signal-conditioning electronics are realized, employing a couple of simple relaxation oscillators. The output of the transducer is only dictated by a pair of dc reference voltages, and hence, high accuracy and linearity over the entire range (from 0deg to 360deg) are easily obtained by the use of precision dc reference voltages. Detailed analysis indicates that the sensitivity of the transducer is minimal for variations in different parameters. Experimental results obtained on a prototype transducer that has been built and tested establish the efficacy of the proposed transducer. The worst-case error of the prototype transducer is found to be less than 0.1%.     

Optimum Form of Capacitive Transducer for Displacement Measurement

A comb-shaped capacitive transducer for displacement measurement is used as a manufacturing machine controller, a step-and-repeat camera, and an electrical micrometer. In this transducer one of the comb-shaped electrodes is fixed and the other is moved parallel to it. For an accurate measurement it is desirable to increase the difference between the maximum and the minimum values of the capacitance. It has been reported that putting dielectric protective layers on the surfaces of the electrodes effectively increases that difference. To find the optimum form of the transducer, a simulation based on the finite-element method is introduced, and the simulation is experimentally verified. To achieve the optimum form, the distance between the electrode must be made as narrow as possible, and the width of the tooth should be 20 ~ 30 percent of one pitch. The effect of dielectrics put in the capacitor is also discussed.     

与CMOS兼容的MEMS气压传感器工艺实现与性能分析

采用CMOS标准工艺,同时采用三种典型MEMS后处理关键工艺,重点通过对牺牲层释放工艺进行研究,制作实现了一种新型CMOS兼容的电容式气压传感器．在该传感器结构中,作为牺牲层的是在CMOS工艺中形成的掺硼氧化硅．通过释放使电容上电极悬空从而感应气压变化．释放过程采用氢氟酸HF、氯化铵、甘油和水的混合溶液．由于释放孔大小和释放孔间距的设计十分关键,通过实验验证优化了4μm×4μm的释放孔更适用于此传感器结构,并对此结构进行了性能分析与实验测试．结果表明,该气压传感器结构合理,工艺成功,重点解决了MEMS后处理中的牺牲层释放工艺与CMOS标准工艺的兼容问题,为利用CMOS标准工艺进行MEMS传感器的研制做出了有益的尝试．     

A High-Temperature Highly Sensitive Capacitive Pressure-Pulsation Sensor

The construction and characteristics of the sensor and a method of measuring low levels of pressure pulsations are described.     

A Time-to-First-Spike CMOS Image Sensor

A time-to-first-spike (TTFS) imager was designed such that each pixel outputs a single digital pulse whose timing encodes pixel illumination. For still image applications, this time representation provides a tremendous increase in dynamic range, similar to that of other existing time-based imagers. However, a major advantage of the TTFS imager is that this wide dynamic range can be achieved even for 30 frames/s video applications. A prototype 32times32 TTFS image sensor was fabricated in AMI 0.5 mum CMOS technology. The prototype chip demonstrates a 104 dB dynamic range (limited by the optical equipment), 42 V/electron conversion gain, 1.25 nA/cm² dark current, and 3.1 mW power consumption at 30 frames/s.     

A 1.2-V CMOS $RC$ Oscillator for Capacitive and Resistive Sensor Applications

An accurate self-adjusting CMOS $RC$ oscillator for capacitive and resistive sensor applications has been designed and manufactured. The oscillator operates with supply voltages from 1.2 to 3 V and achieves an internal accuracy of $pm$ 0.7% with a temperature range from $-20 ^{circ}hbox{C}$ to 60 $^{circ}hbox{C}$. The $RC$ oscillator was fabricated in a 0.35- $muhbox{m}$ standard n-well CMOS process with threshold voltages of 0.5 and $-$0.65 V. Its design and operation are described, and results of measurements performed on the fabricated chips are presented.      

压阻变换压力传感器的性能预测模型

热、压环境下压阻变换压力传感器的性能可以通过有限元方法预测．这里研究了简化的1／8模型，模型考虑了二氧化硅和氮化硅生成过程及堆阳极键合和胶粘结合过程．结果发现有限元预测结果和实验数据具有可比性．范例研究表明，硼硅堆导致产生一定的非线性，但它隔离了硬环氧树脂的非线性．在包装过程中最好使用柔性环氧黏合或软黏胶性结合．黏合材料的黏弹性和黏塑性将会导致传感器输出的滞后和漂移误差．然而，在相对稳定的环境下。软黏合剂对传感器的影响可以忽略．此外，详细的设计和过程信息有助于提高模型的适用性．     

Capacitive Sensor Interface for an Electrostatically Levitated Micromotor

This paper presents the design and performance of a capacitive sensor interface dedicated to a microelectromechanical systems (MEMS) micromotor electrically levitated in five DOFs. The position and orientation of the rotor are detected by measuring differential rotor-electrode capacitances with a set of capacitance-to-voltage converters (CVCs). The sensor contains multiplexed electrodes for both capacitive sensing and force feedback, and a set of common electrodes for carrier exciting with an aim to eliminate ohmic connection with the levitated rotor. The proposed interface circuit is based on a symmetrical structure containing two half ac bridges, more robust against parasitic capacitances, capable of detecting capacitance changes with frequency higher than 10 kHz, and able to decouple multiaxis position signals of a levitated rotor. An electronic equivalent model of the sensing circuit has been developed and used to analyze the sensor performance. The major nonidealities and their effects on the accuracy of the position sensing are discussed. The performance of the sensing circuit was experimentally investigated on a prototype interface circuit. The experimental results confirm the principles of operation and the performance of the interface for the multiaxis levitated devices using capacitive position sensors.     

Charge-Based Capacitive Sensor Array for CMOS-Based Laboratory-on-Chip Applications

In this paper, we present a capacitive sensor array for highly integrated lab-on-chip (LoC) applications using the charge-based capacitance measurement method (CBCM). The core-CBCM sensor chip is designed and implemented in 0.18 micron CMOS process featuring an array of capacitive sensors; an offset cancellation module and a low complexity analog-to-digital converter (ADC). This sensor chip is incorporated with a microfluidic channel using direct-write fabrication process. We demonstrate the testing results using chemical solvents with known dielectric constants in order to show the viability of the proposed sensor chip for LoCs.     

A Differential Capacitive Torque Sensor With Optimal Kinematic Linearity

This paper presents a new design for a torque sensor based on a differential capacitive technology. An arc-radial mechanism is adopted to achieve high rotary/radial motion linearity. Kinematic model of this assembly is derived via vector loop equations. A nonlinearity index is formulated and practical kinematic constraints are imposed. Results show that very high kinematic linearity could be achieved by this new device     

MEMS电容传感器小电容的测量

本文首先介绍了一种MEMS电容式微硅加速度计的结构和等效电路,阐述了开关电容放大器的工作原理和输出电压与电容的关系,重点讨论了用开关电容技术测量微硅加速度计小电容的方法.     

调相型容栅传感器传输函数的误差分析

本文讨论了容栅传感器传输函数对示值误差的表达,分析了传输解调函数的不同组合对误差的影响,并对不同的解调函数在一个空间周期内求得了相等的最大误差。     

用于非接触测量的光学传感器

本文介绍了一种用于批量零件进行公差带测量的传感器．由一个双光束投射系统将具有互补色的光带投射到被测零件表面，通过显微系统接收后，由视场中光带的颜色即可判定该被测零件是否合格，并可判定被测件尺寸的超差方向。由于该传感器采用的是光学非接触测量法，所以适用于橡胶、塑料以及软金属的测量．     

一种可控测量力的大量程激光干涉位移传感器

利用音圈电机控制测量过程中测量力的方法,提出了一种可控测量力的激光干涉位移传感器,介绍了传感器的结构及其测量原理.通过对测杆的受力情况进行分析可知,改变音圈电机的驱动电流可以很好地控制触针作用于样品表面测量力大小.分析测杆的运动模型,得出测杆转动会带来水平测量误差,提出了相应的误差补偿方法.使用该传感器对倾斜放置的样品进行了测量,结果表明,该传感器在大量程范围内能实现高精度的表面形貌测量,并有效的控制测量力,减小对测量表面的划伤.     

测量系统小波与神经网络联合去噪研究

本文将神经网络的非线性阈值单元和训练方法引入小波去噪中 ,提出了一种具有阈值自学习能力的小波与神经网络联合去噪方法。这一方法的去噪阈值能够根据训练信号进行学习 ,有利于针对实际系统寻找较优的去噪阈值 ,适用于对确定系统的测量信号进行去噪。文中给出了相应的训练算法并对该方法的有效性进行了检验。     

Plasmonic Color Filters for CMOS Image Sensor Applications

We report on the optical properties of plasmonic hole arrays as they apply to requirements for plasmonic color filters designed for state-of-the-art Si CMOS image sensors. The hole arrays are composed of hexagonally packed subwavelength sized holes on a 150 nm Al film designed to operate at the primary colors of red, green, and blue. Hole array plasmonic filters show peak transmission in the 40-50% range for large (>5 × 5 μm(2)) size filters and maintain their filtering function for pixel sizes as small as ～1 × 1 μm(2), albeit at a cost in transmission efficiency. Hole array filters are found to robust with respect to spatial crosstalk between pixel within our detection limit and preserve their filtering function in arrays containing random defects. Analysis of hole array filter transmittance and crosstalk suggests that nearest neighbor hole-hole interactions rather than long-range interactions play the dominant role in the transmission properties of plasmonic hole array filters. We verify this via a simple nearest neighbor model that correctly predicts the hole array transmission efficiency as a function of the number of holes.