基于负温度系数的多晶硅电阻电热激励/压阻检测微桥谐振器的新型红外探测器（英文）

报道了一种基于负电阻温度系数的多晶硅电阻电热激励/压阻检测SiO 2/Si3N4/SixNy微桥谐振器的新型红外探测器.微桥谐振器吸收的红外辐射引起微桥温度升高,激励电阻和检测电桥的阻值减小,使得恒定激励电压作用下激励电阻的静态功率和惠斯登电桥的焦耳热增加,等效于增加了辐射在微桥谐振器上的红外辐射.初步的实验证实了该方案的可行性.     

微桥电阻的辐射特性研究

随着微机械加工技术的发展,电阻阵列成为一种最具发展潜力的动态红外景象产生器。在半实物（HWIL）仿真系统中,它被用来对红外摄像机、导弹寻的器以及各种红外探测系统的实时性能进行测试和评估。电阻阵列采用电阻元作为其微辐射元,当电流流过时。电阻元产生热量进而产生红外辐射。通过控制流过每个电阻元的电流就可以控制电阻的温度,从而达到显示红外图像的目的。介绍了利用表面微机械加工技术研制的电阻阵列基本组成单元——微桥电阻的辐射特性．主要包括：微桥电阻介质膜红外光谱辐射率、等效黑体辐射温度以及温度分辨率等,并通过分析得出该微桥电阻具有低功耗、高等效黑体辐射温度的特点。能够满足中波和长波红外目标模拟的需要。     

共振吸收在微桥电阻阵列中的应用

红外武器系统的快速发展, 对红外仿真系统提出了更高的要求。微桥电阻阵列作为红外仿真系统的核心器件, 其性能的提高对红外仿真系统的发展至关重要。微桥电阻是利用电阻加热微辐射元来产生红外辐射的, 根据微桥电阻的工作原理可知, 提高微桥电阻阵列单元辐射效率是微桥电阻性能提高的关键技术之一。利用以Al 为反射层电阻、空气为中间介质层和TiNx 为吸收层电阻组成的谐振腔结构可以明显提高所需波段的红外辐射效率, 从而提高微桥电阻的性能。共振吸收结构为微桥电阻阵列的进一步低功耗、大面阵化提供了有效的设计和制作途径。     

共振吸收在微桥电阻阵列中的应用

红外武器系统的快速发展,对红外仿真系统提出了更高的要求。微桥电阻阵列作为红外仿真系统的核心器件,其性能的提高对红外仿真系统的发展至关重要。微桥电阻是利用电阻加热微辐射元来产生红外辐射的,根据微桥电阻的工作原理可知,提高微桥电阻阵列单元辐射效率是微桥电阻性能提高的关键技术之一。利用以Al为反射层电阻、空气为中间介质层和TiNx为吸收层电阻组成的谐振腔结构可以明显提高所需波段的红外辐射效率．从而提高微桥电阻的性能。共振吸收结构为微桥电阻阵列的进一步低功耗、大面阵化提供了有效的设计和制作途径。     

红外微辐射元的研制

利用表面微机械加工技术，研制出微桥结构红外微辐射元．该辐射元是电阻阵列动态红外景象产生器的基本组成单元．辐射元可以产生等效黑体辐射温度为300～500K的红外辐射，能够满足中波、长波红外半实物仿真的需求．     

电热激励微悬臂梁谐振器输出电压影响因素研究

制作了电热激励硅 /二氧化硅双层微悬臂梁谐振器。对影响谐振器输出电压的因素研究结果表明 :减小梁宽度、硅层厚度、环境气压和温度 ,可增大微悬臂梁谐振器输出电压 ;输出电压随激励功率增加而增大 ;谐振器输出电压与谐振器根部压敏电桥电源电压成正比。最后论述了提高谐振器输出电压的可行途径     

电阻阵列辐射输出特性评估

电阻阵列是一种出射式动态红外场景投射器件,它通过控制流经电阻元的电流使电阻发热产生红外辐射,达到成像目的.由于非均匀性校正等需求,需要使用红外成像探测器测试单个电阻元的辐射特性.由于输入电流和输出红外辐射之间复杂的非线性关系,电阻阵列的辐射输出特性主要通过测试数据拟合来获取.基于典型的光学系统配置,给出了电阻元辐射亮度与探测器辐射照度之间的关系式,分析了光轴上及轴外电阻元辐射亮度的测试方法;通过对硅桥和悬浮薄膜电阻阵列电阻元的分析,给出了实际温度与等效黑体温度之间的对应关系,对电阻阵列辐射输出特性的测试具有一定的理论参考价值.     

薄膜转移工艺制备的128×128规模高架桥式电阻阵

采用新的薄膜转移工艺,成功制备了128×128规模的高架桥式电阻阵。电阻阵的单元尺寸为50μm×50μm,占空比50%。初步测试了该高架桥电阻阵的两个基本指标,微桥的热时间常数和最高等效黑体温度,并对该电阻阵进行了成像实验。采用电学法测试单个微桥的时间常数τ约为4.5 ms,可在100Hz下工作。将整个面阵点亮,在8~12μm波段最高等效黑体温度达到250℃,推测在3~5μm波段最高等效黑体温度超过300±20℃。将整个器件全部点亮并驱动到最高温度时,器件的最大功率为30 W。该电阻阵可成功实现驱动显示成像。测试结果表明该高架桥式电阻阵初步满足红外景象产生器的要求。     

多晶硅压力传感器灵敏温度系数自补偿技术研究

介绍了硅压力传感器的灵敏温度系数补偿原理,给出了一种在宽温度范围内采用二次补偿灵敏度温度系数的方法,实现了宽范围较高的补偿精度.具体方案是把压阻式惠斯登电桥与温度传感器、可微调多晶硅电阻集成在一个芯片上,通过优化多晶硅电阻的掺杂浓度和改变激励源的温度特性,从而实现对多晶硅压力传感器灵敏温度系数的二次补偿作用.经补偿,传感器的灵敏温度系数小于-1.5×10-4/℃,该方法的补偿温度范围为20℃～ 150℃,通用性强.     

电阻阵列动态红外景像产生器

基于微机械加工技术发展起来的电阻阵列是动态红外景像产生器的一种。它可在半实物（HWIL）仿真系统中用来对红外摄像机、导弹寻的器以及各种红外探测系统的实时性能进行测试和评估。电阻阵列是以电阻元件为微辐射元,当电流流过时,电阻元产生热量,从而产生红外辐射。通过控制流过每个电阻元的电流就可以控制每个电阻的温度,从而达到显示红外图像的目的。电阻阵列具有其他红外景像产生器所不具有的特点,低功耗、大温度范围、高分辨率、高占空比等,适合于各种红外目标的模拟。文另介绍了其基本原理、发展现状、关键技术及发展动态等,给出了一些器件的典型参数。     

Bridge configurations in piezoresistive two-axis accelerometers

In piezoresistive two-axis accelerometers with two proof masses suspended by cantilever beams, there are generally many ways to configure the Wheatstone bridges. The configurations are different both with respect to functionality and performance. The main distinction is between bridges that contain resistors belonging to both proof masses, and the one bridge that doesn’t. We compare the different bridge configurations by analytical calculations of bridge non-linearity, robustness towards manufacturing variations and electronic noise. We consider accelerometers where the ratio between the sensitivity to acceleration normal and parallel to the chip plane vary over a wide range. For numerical examples we use representative values for p-type silicon. The performance of the configuration with one bridge connected to each proof mass is superior to those that combine resistors belonging to different proof masses.     

High-temperature storage and thermal cycling studies of thick filmand wirewound resistors

The operating ambient temperature for underhood automotive and aerospace applications is increasing. This work was undertaken to evaluate the suitability of thick film and wirewound resistors for distributed aircraft control systems in a 200°C-225°C operating environment. High temperature stability testing of power wirewound and thick film resistors is reported. Dale power wirewound 1 Ω, 100 Ω, and 10 kΩ resistors with power ratings of 5 W and 25 W were tested. The TCR of the 100 Ω, and 10 kΩ resistors was very small, however, the 1 Ω resistor varied by 5% over the temperature range from 25°C to 300°C. Stability with long term storage (10000 h) at 300°C was measured for the wirewound resistors unpowered and powered at 20% of rated power. With the exception of the 10 kΩ/25W resistor, the change in resistance was less than 4%. Wirewound resistors were also thermal cycled 1000 times over a temperature range from -55°C to 225°C with only one failure due to a broken internal connection. Three 900 Series thick film resistor pastes from Heraeus-Cermalloy were studied: 100 Ω/sq., 1 kΩ/sq., 10 kΩ/sq. The temperature coefficient of resistance (TCR) was measured from 27°C to 500°C in 50°C increments. The change in resistance was <±6% up to 300°C. A 2 × 2 matrix of variables was included in the 300°C storage test: untrimmed resistors, resistors trimmed up 50% in value, unpowered, and powered at 1/8 W. Palladium/Silver was the initial termination choice for these 300°C studies, but silver migration under electrical bias lead to electrical shorts between conductor traces on the substrates with powered resistors. Gold terminated thick film resistors were used for powered storage testing at 300°C. The change in resistance after 10000 h at 300°C was < 3% for all test combinations     

Emitter ballasting resistor design for, and current handlingcapability of AlGaAs/GaAs power heterojunction bipolar transistors

A systematic investigation of the emitter ballasting resistor for power heterojunction bipolar transistors (HBTs) is presented. The current handling capability of power HBTs is found to improve with ballasting resistance. An equation for the optimal ballasting resistance is presented, where the effects of thermal conductivity of the substrate material and the temperature coefficient of the ballasting resistor are taken into account. Current levels of 400 to 800 mA/mm of emitter periphery at case temperatures of 25 to -80°C for power AlGaAs/GaAs HBTs have been obtained using an on-chip lightly doped GaAs emitter ballasting resistor. Device temperature has been measured using both an infrared microradiometer and temperature-sensitive electrical parameters. Steady-state and transient thermal modeling are also performed. Although the measured temperature is spatially nonuniform, the modeling results show that such nonuniformities would occur for a uniform current distribution, as would be expected for an HBT with emitter ballasting resistors     

Bridges I have crossed

The Wheatstone bridge was still in use when I received my Ph.D. in physics in the early 1960s. I researched the thermal conductivity of superconducting thin films at Rutgers University in New Jersey using standard 1/10 W Allen-Bradley carbon resistors as thermometers and measured their resistance with a Wheatstone bridge built from top-of-the line components. Since then, I have moved from experimental physics to the study of apparatus used in physics in the late 19th and early 20th centuries. During this time, the construction of high-precision electrical measurement equipment was raised to an art in the United States by companies such as Leeds & Northrup (L&N) of Philadelphia and General Radio Co. of Cambridge, Massachusetts. In this paper I will discuss some favorite pieces of apparatus in my own collection based on bridge circuits.     

DC-18GHz微波功率薄膜电阻器的设计及制作

设计并仿真了频率范围为DC-18GHz,功率负载为20W的微波功率薄膜电阻器,根据仿真结果,采用反应磁控溅射法制备了TaN微波功率薄膜电阻器。仿真结果表明,所设计的薄膜电阻器在DC-18GHz频率范围内,电压驻波比均小于1.2,加载20W微波功率时,薄膜电阻器表面的最高温度为108℃。实验结果表明,所制备的TaN薄膜电阻器在DC-18GHz频率范围内,电压驻波比小于1.25;加载20W直流功率96小时,电阻器的阻值变化小于2%,表面最高温度为105℃;在25-125℃温度范围内电阻器的温度电阻系数为-40ppm/℃。     

Polysilicon resistor trimming by laser link making

A technique for laser trimming of polysilicon resistors has been developed. In this scheme an undoped polysilicon film is patterned lithographically, and then photoresist patterns are used to prevent doping of certain narrow areas of each resistor during the impurity implant; thus, the protected areas remain insulating after wafer processing. Subsequent laser scanning of the undoped regions can produce precise reductions in resistance by lateral diffusion of dopant impurities. Trimming can be accomplished by changing either the laser power or the position. Q-switched Nd:YAG (1.06-μm wavelength) and second-harmonic (0.53-μm wavelength) radiations have produced successful results. The process was applied to passivated resistors with negligible (perhaps zero) post-trim drift, and the temperature coefficients of resistivity (TCRs) of trimmed resistors can be matched to the TCRs of untrimmed resistors in the same film     

A Chopper Stabilized Biasing Circuit Suitable for Cascaded Wheatstone-Bridge-Like Sensors

Many sensitive devices are based on Wheatstone bridge structures or can be modeled as Wheatstone bridges like Hall effect magnetic sensors. These sensors require a biasing circuit, and many solutions were proposed. However, up to now, none of them gives the opportunity to cascade several sensors, while such a cascade can help in improving the signal-to-noise-ratio (SNR) or in removing some parasitic effects through the direct summing/subtraction of sensing/parasitic effects. The circuit this paper presents is based on an operational transconductance amplifier with$n$output stages, and allows to cascade$n$Wheatstone-bridge-like sensors. It is shown that the maximal number of bridges which can be efficiently cascaded is limited by the output resistance of the output stages. Nevertheless, this number remains sufficient in practical cases, easily up to$n=10$. To remove the$1/f$noise coming from the output stages, a chopper stabilization is used. We also establish formulas which allow quick hand calculation of the main parameters of the circuit. A prototype where 10 Hall effect sensors are cascaded is presented as well as experimental results.     

Characterization of highly doped n- and p-type 6H-SiCpiezoresistors

Highly doped (~2×10¹⁹ cm^-3) n- and p-type 6H-SiC strain sensing mesa resistors configured in Wheatstone bridge integrated beam transducers were investigated to characterize the piezoresistive and electrical properties. Longitudinal and transverse gauge factors, temperature dependence of resistance, gauge factor (GF), and bridge output voltage were evaluated. For the n-type net doping level of 2×10¹⁹ cm^-3 the bridge gauge factor was found to be 15 at room temperature and 8 at 250°C. For this doping level, a TCR of -0.24%/°C and -0.74%/°C at 100°C was obtained for the n- and p-type, respectively. At 250°C, the TCR was -0.14%/°C and -0.34%/°C, respectively. In both types, for the given doping level, impurity scattering is implied to be the dominant scattering mechanism. The results from this investigation further strengthen the viability of 6H-SiC as a piezoresistive pressure sensor for high-temperature applications     

MEMS压阻式三轴加速度传感器的双路循环电桥检测法

A cycle bridge detection method, which uses a piezoresistive triaxial accelerometer, has been described innovatively. This method just uses eight resistors to form a cycle detection bridge, which can detect the signal of the three directions for real time. It breaks the law of the ordinary independent Wheatstone bridge detection method, which uses at least 12 resistors and each four resistors connected as a Wheatstone bridge to detect the output signal from a specific direction. In order to verify the feasibility of this method, the modeling and simulating of the sensor structure have been conducted by ANSYS, then the dual cycle bridge detection method and independent Wheatstone bridge detection method are compared, the result shows that the former method can improve the sensitivity of the sensor effectively. The sensitivity of the x, y-axis used in the former method is two times that of the sensor used in the latter method, and the sensitivity of the z-axis is four times. At the same time, it can also reduce the cross-axis coupling degree of the sensor used in the dual cycle bridge detection method. In addition, a signal amplifier circuit and adder circuit have been provided, Finally, the test result of the ＂eight-beams/mass＂ triaxial accelerometer, which is based on the dual cycle bridge detection method and the related circuits, have been provided. The results of the test and the theoretical analysis are consistent, on the whole.     

Quantitative Analysis of Resistance Tolerance of Polymer Thick Film Printed Resistors

Low cost methodologies of resistor fabrications are needed for cost effective embedding of resistors into polymeric substrates. Polymer thick film resistors (PTFRs) are low temperature processable, low cost resistors with a wide resistivity range. The electrical resistance variation of these resistors is in the range of around plusmn20% after deposition and trimming procedure is employed to tune the resistances to meet specifications. This adds to the cost and complicates the fabrication process when the resistors are embedded. In this study, the influences of PTFRs geometries on the resistance tolerances were investigated. Results indicated that the resistance accuracy of stencil printed resistors was markedly higher than that of the screen-printed resistors. The screen-printed resistor edge geometries were observed to be rough. Finite element method analyses revealed that the resistance tolerances were associated with edge roughness. Remedies to reduced variations were proposed and the relationship between resistance tolerances and aperture orientations was also outlined