Fast-response silicon flow sensor with an on-chip fluid temperature sensing element

A new silicon flow sensor with a robust thermal isolation structure has been developed. The thermal isolation structure is mainly made of a 20-µm-thick oxidized porous silicon membrane. This thermal isolation structure makes it possible for the sensor to have a fast-response characteristic and an on-chip fluid temperature sensing element design. The sensor can be used in liquid flow as well as gas flow. Its operation is based on heat transfer from the heated sensor to a moving fluid. It has two platinum thin-film resistors, a heating element, and a fluid temperature sensing element on the chip. The sensing element is thermally isolated from the heating element. The external circuit of the sensor maintains a constant temperature difference between the heating element and the fluid. The sensor chip characteristics were evaluated theoretically by heat transfer analysis during the chip design. Measurements were made for oil flow velocity of 0-30 cm/s and air flow velocity of 0-14 m/s. Response time was below 100 ms, and a compensated output for fluid temperature change was obtained.     

MEMS热式风速风向传感器输出性能优化研究

环境测温二极管在工作时受传感器芯片热场影响,常引发MEMS热式风速风向传感器加热电压-风速曲线异常。将其更换为外置测温二极管,并调整其与传感器芯片距离,成功解决了输出曲线异常现象。并在此基础上,优化芯片及外置测温二极管的封装方案,消除了热场的相互干扰和不必要的热损耗,同时保证了外置测温二极管与空气的良好接触。风场测试结果表明,传感器的加热电压-风速曲线变得平滑,且重复性好,风速和风向的测量误差分别在±4%和±4°以内,系统的上电稳定时间大幅缩短至15 s左右。     

A high-performance thermal module for computer packaging

A thermal module was designed to transfer heat efficiently from high power dissipation chips to a liquid coolant via forced convection. Turbulent and laminar flow regimes were investigated. Channel geometries for deep channels (1000 μm deep, and used for turbulent flow), and shallow channels (100 μm deep, and used for laminar flow) were optimized for high heat transfer coefficient, ease of fabrication, and better structural rigidity of the module. A 4″ x 4″ module, made out of Cu, was tested using a 4″ Si “thermal” wafer as a heat generating source as well as a temperature sensor. Wafer scale integration and high energy ion implantation were employed to obtain nine l x l cm heat sources, and temperature sensing diodes embedded within the thermal wafer. For the deep channel design, the maximum device temperature rise on the module was 18° C for a power dissipation of 42 W/chip, and a flow rate of 126 cc/sec. For the shallow channel design, the temperature rise was 19° C for a flow rate of 19 cc/sec, and a power dissipation level of 42 W/chip. With all nine chips on the thermal module powered to 42 W/chip, the maximum chip to chip temperature variations were found to be 2 and 8° C for deep and shallow channel designs, respectively.     

新型恒温式集成温度传感器

<正> 一、引言 把敏感元件与信号处理电路集成在一起,实现传感器的集成化,是目前传感器发展的一个重要方向。它不仅可提高传感器的信噪比,还可以提高传感器的性能和接口灵活性。对于集成温度传感器,由于芯片上的信号处理电路与敏感元件必须一起工作在被测环境温度中,这样环境温度的变化会影响传感器中信号处理电路的性能,从而影响整个集成传感器的性能。本文提出一种工作在恒定芯片温度的新型集成温度传感器,其中的信号处理电路不受环境温度的影响,而且还具有传统温度传感器所没有的优点。     

A single-chip fingerprint sensor and identifier

A chip architecture that integrates a fingerprint sensor and an identifier in a single chip is proposed. The fingerprint identifier is formed by an array of pixels, and each pixel contains a sensing element and a processing element. The sensing element senses capacitances formed by a finger surface to capture a fingerprint image. An identification is performed by the pixel-parallel processing of the pixels. The sensing element is built above the processing element in each pixel. The chip architecture realizes a wide-area sensor without a large increase of chip size and ensures high sensor sensitivity while maintaining a high image density. The sensing element is covered with a hard film to prevent physical and chemical degradation and surrounded by a ground wall to shield it. The wall is also exposed on the chip surface to protect against damage by electrostatic discharges from the finger contacting the chip. A 15×15 mm² single-chip fingerprint sensor/identifier LSI was fabricated using 0.5-μm standard CMOS with the sensor process. The sensor area is 10.1×13.5 mm². The sensing and identification time is 102 ms with power consumption of 8.8 mW at 3.3 V. Five hundred tests confirmed a stranger-rejection rate of the chip of more than 99% and a user-rejection rate of less than 1%     

An ultraminiature CMOS pressure sensor for a multiplexedcardiovascular catheter

A multiplexed ultraminiature pressure sensor designed for use in a cardiovascular catheter is described. The sensor operates from only two loads, which are shared by two sensors per catheter. The sensing chip is 350 μm wide by 1.4 mm long by 100 μm thick. CMOS readout circuitry at the sensing site converts applied pressure to a frequency variation in the supply current, which is detected at the end of the catheter by a microprocessor-controlled interface. The nominal pressure sensitivity is 2 kHz/fF about a zero-pressure output frequency of 2.7 MHz. This on-site circuitry contains two reference capacitors which allow external compensation for nonlinearity and temperature sensitivity and has an idle-state power dissipation of less than 50 μW. With the transducer sealed at ambient pressure, the device can resolve pressure variations of about 3 mmHg, while vacuum-sealed devices do considerably better and should permit <2 mmHg resolution in practical systems     

一种内嵌喷嘴差压式FBG流量传感器

针对传统液压系统流量测量中存在的传感器体积 较大、测量精度不高等问题,研究并设计一 种内嵌喷嘴差压式光纤 Bragg 光栅(FBG ) 流量传感器。在分析 FBG 及差压式流量测量原理的基础上, 选用标准喷嘴作为节流元件,通过将 FBG 沿径向粘贴于圆形平面膜片上,敏感被测流体经过喷嘴节流口 后在两侧所产生的压力差。推导了 FBG 中心波长偏移与被测流体流量变化之间存在的数学关 系,并通 过试验平台测量了传感器的静压特性以及动态流量特性。测试结果表明,传感器中 FBG 平面膜片的静压力 差压灵敏度为 0.712nm/MPa ,而差压式 FBG 流量传感器的灵敏度为 0.067L/s 。本文传感器具有测量精度高、 体积较小和环境适应能力强等优点,且易于实现传感复用并构成准分布式检测网络。     

A remote pressure sensor with digital signal interface

A high performance pressure sensor circuit is described with a digital signal interface for accurate remote sensing of pressure. The signal conditioning circuitry converts sensor resistance variation into a digital signal. Automatic offset error correction prevents long term and temperature drift effects on overall performance. The digitized signal is detected remotely over two wires by means of optical or ferrite coupling. The same two wires were used for power supply delivery. Floating operation allows good performance in a noisy environment. Test results have shown less than 0-25 psi/°C input equivalent pressure error in a temperature range of – 25°C to +75°C. The non-linearity was less than 0-2% in a dynamic pressure range of 500/1 at room temperature.     

环境温度对气流式水平姿态传感器灵敏度的影响

采用有限元方法,计算了不同温度下倾斜10°时敏感元件内的温度场和流场,分析和验证了环境温度对气流式水平姿态传感器灵敏度的影响机理。结果表明:随着环境温度的增加,传感器灵敏度降低;反之,随着环境温度的下降,传感器灵敏度提高;倾斜10°时,传感器的灵敏度温度系数为0.55mV/℃。     

Piezoelectric Sensors Operating at Very High Temperatures and in Extreme Environments Made of Flexible Ultrawide-Bandgap Single-Crystalline AlN Thin Films

Extreme environments are often faced in energy, transportation, aerospace, and defense applications and pose a technical challenge in sensing. Piezoelectric sensor based on single-crystalline AlN transducers is developed to address this challenge. The pressure sensor shows high sensitivities of 0.4–0.5 mV per psi up to 900 °C and output voltages from 73.3 to 143.2 mV for input gas pressure range of 50 to 200 psi at 800 °C. The sensitivity and output voltage also exhibit the dependence on temperature due to two origins. A decrease in elastic modulus (Young's modulus) of the diaphragm slightly enhances the sensitivity and the generation of free carriers degrades the voltage output beyond 800 °C, which also matches with theoretical estimation. The performance characteristics of the sensor are also compared with polycrystalline AlN and single-crystalline GaN thin films to investigate the importance of single crystallinity on the piezoelectric effect and bandgap energy-related free carrier generation in piezoelectric devices for high-temperature operation. The operation of the sensor at 900 °C is amongst the highest for pressure sensors and the inherent properties of AlN including chemical and thermal stability and radiation resistance indicate this approach offers a new solution for sensing in extreme environments.     

Tin oxide nanosensors for highly sensitive toxic gas detection and their 3D system integration

We present nanosensors based on ultrathin SnO₂ films, which are very sensitive to the highly toxic gases SO₂ and H₂S. The SnO₂-sensing films are fabricated by a spray pyrolysis process on Si substrates with a thickness of 50 nm. The sensor resistance is decreased in the presence of the toxic gases. Exposure to 50 ppm SO₂ leads to a sensor resistance drop of ∼40% whereas a H₂S gas concentration of only 2.5 ppm decreases the resistance by ∼85%, which demonstrates the extraordinary sensitivity of the nanosensors. With respect to further system integration a CMOS technology based micro-hotplate containing heating element and sensing layer has been simulated. Preliminary results show that the micro-hotplates can provide operating temperatures of 400 °C with a power consumption of less than 5 mW. A concept for 3D system integration of the nanosensor chip and a CMOS chip based on Through-Silicon-Via (TSV) technology is proposed as potential roadmap towards smart nanosensor systems for daily life applications.     

A batch-fabricated silicon capacitive pressure transducer with low temperature sensitivity

A batch-fabricated solid-state capacitive pressure transducer has been developed using silicon integrated-circuit technology. The fabricated devices exhibit a dynamic range of 350 mmHg and a pressure sensitivity of about 1100 ppm/mmHg. The temperature coefficient of zero-pressure offset is about +50 ppm/°C (less than 0.05 mmHg/°C) and the temperature coefficient of pressure sensitivity over the -20 to +50°C temperature span is about +275 ppm/°C (less than 0.04 mmHg/°C) when the device is used with an open or vacuum-sealed reference cavity. These temperature coefficients are substantially lower than those of previously reported monolithic devices and are low enough that expensive temperature trims can be eliminated for many applications.     

Fiber-Optic Instrument for Temperature Measurement

A practical fiber-optic measurement instrument for temperature was constructed consisting of a small sensor responding to optical absorption change in a semiconductor, and a unique signal processing system with two different-wavelength light emitting diodes (LED's). The fiber-optic sensor with a semiconductor chip is quite small, very sensitive, highly reliable, and easy to manufacture at low cost. The most outstanding feature of this system is that it is free from optical-stray-loss. The accuracy of about +-1° and the response time of about 2 s were obtained in the temperature range from -10° C to 300°C.     

Micro FET pressure sensor manufactured using CMOS-MEMS technique

The fabrication of a micro field effect transistor (FET) pressure sensor using the commercial 0.35 μm complementary metal oxide semiconductor (CMOS) process and a post-process has been investigated. The pressure sensor is composed of 16 sensing cells in parallel, and each sensing cell includes a suspended membrane and an NMOS. The suspended membrane is the movable gate of the NMOS. The pressure sensor needs a post-process to obtain the suspended membrane after the CMOS process. The post-process employs etchants to etch the sacrificial layers to release the suspended membrane, and then a low-pressure chemical vapor deposition (LPCVD) parylene is used to seal the etching holes in the pressure sensor. The pressure sensor produces a change in current when applying a pressure to the sensing cells. Experimental results show that the pressure sensor has a sensitivity of 0.022 μA/kPa in the pressure range of 0–500 kPa.     

集成硅微机械光压力传感器

介绍了一种新颖的集成硅微机械光压力传感器的结构、工作原理、制造工艺和实验结果。该传感器是利用半导体集成电路微细加工技术和各向异性腐蚀相结合的方法，将传输、获取信息的光波导，敏感弹性硅膜和光电探测器集成在一块三维硅基片上得到的。它具有灵敏度高、抗干扰能力强、自身无需电源、防爆、成本低和可靠性高等优点。     

基于色敏元件的光位移传感器高动态解调研究

介绍了波长编码型光学位移传感器的输出光的特点及目前利用光谱仪进行解调的制约因素,分析了色敏元件的工作原理及色敏元件对传感器输出窄带光进行解调的可行性,设计了色敏解调线路并对行程±60 mm的光位移传感器进行了测试验证,测得色敏解调方案对传感器的测试精度可以达到±0.37％F.S,且可以达到600 Hz以上的高动态解调.     

Dual Mode Strain–Temperature Sensor with High Stimuli Discriminability and Resolution for Smart Wearables

Strain and temperature are important physiological parameters for health monitoring, providing access to the respiration state, movement of joints, and inflammation processes. The challenge for smart wearables is to unambiguously discriminate strain and temperature using a single sensor element assuring a high degree of sensor integration. Here, a dual-mode sensor with two electrodes and tubular mechanically heterogeneous structure enabling simultaneous sensing of strain and temperature without cross-talk is reported. The sensor structure consists of a thermocouple coiled around an elastic strain-to-magnetic induction conversion unit, revealing a giant magnetoelastic effect, and accommodating a magnetic amorphous wire. The thermocouple provides access to temperature and its coil structure allows to measure impedance changes caused by the applied strain. The dual-mode sensor also exhibits interference-free temperature sensing performance with high coefficient of 54.49 µV °C⁻¹, low strain and temperature detection limits of 0.05% and 0.1 °C, respectively. The use of these sensors in smart textiles to monitor continuously breathing, body movement, body temperature, and ambient temperature is demonstrated. The developed multifunctional wearable sensor is needed for applications in early disease prevention, health monitoring, and interactive electronics as well as for smart prosthetics and intelligent soft robotics.     

High-sensitivity photonic crystal fiber sensor based on surface plasmon resonance

In this paper, we propose a photonic crystal fiber (PCF) sensor based on the surface plasmonic resonance (SPR) effect for simultaneous temperature and refractive index (RI) measurement. The coupling characteristics and sensing performance of the sensor are analyzed using the full vector finite element method (FEM). The sensor provides two channels for independent measurement of RI and temperature. When operating independently, channel I supports y-polarized light with a sensitivity of up to 7 000 nm/RIU for detecting RI, while channel II supports x-polarized light with a sensitivity of up to 16 nm/°C for detecting temperature. Additionally, we investigate the influence of gold layer thickness on the sensing performance to optimize the sensor.     

基于新型DCA封装的陶瓷风速风向传感器

An advanced direct chip attaching packaged two-dimensional ceramic thermal wind sensor is studied. The thermal wind sensor chip is fabricated by metal lift-off processes on the ceramic substrate. An advanced direct chip attaching （DCA） packaging is adopted and this new packaged method simplifies the processes of packaging further. Simulations of the advanced DCA packaged sensor based on computational fluid dynamics （CFD） model show the sensor can detect wind speed and direction effectively. The wind tunnel testing results show the advanced DCA packaged sensor can detect the wind direction from 0° to 360° and wind speed from 0 to 20 m/s with the error less than 0.5 m/s. The nonlinear fitting based least square method in Matlab is used to analyze the performance of the sensor.     

Fabrication of catheter-tip and sidewall miniature pressure sensors

Silicon-diaphragm miniature pressure sensors, which use the piezoresistive effect, were developed for biomedical applications. We fabricated two types of sensors; that is, a catheter-tip (1.2-mm outside diameter, 0.17 mm thick) and a sidewall (1.4 × 3.45 × 0.22 mm) sensor, both having a thin circular diaphragm. Their diaphragms, 10 µm in thickness and 0.55 mm in diameter, were formed by an electrochemical etching method. Since the stability of pressure sensors is the most important requirement for precise pressure measurements, attractive approaches have been investigated to improve stability. The major instabilities of the present miniature pressure sensors are electrical drifts caused by leakage currents and thermal disturbances related to packaging stress. A shield and a guard plate can prevent the device from leakage currents. A thick supporting rim structure of the sensor and mounting on a stainless steel support with elastic material contribute to eliminate the packaging stress. For the purpose of easy lead attachment to the catheter-tip sensor, we use a unique structure having deep contact holes in deposited thick polysilicon layer (0.05 mm thick). Experimental results are as follows: Initial drift after power up was improved to about one tenth. Thermal disturbances, as temperature zero shift, thermal transient response, and temperature cycle hysteresis were greatly reduced. Low-temperature zero shift of 0.2 mmHg/°C was obtained using a simple temperature compensation method. Long-term drift was 0.6 mmHg/day. The catheter of 1.8-mm outer diameter having two sidewall sensors has been satisfactorily used for the study of urodynamics.