MEMS-based microheaters integrated gas sensors (original) (raw)
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Design of the optimum microheater for smart MEMS gas sensor
Conventional Metal Oxide gas sensors commonly used for sensing inflammable hydrocarbon gases and other toxic gases. However, they suffer from the two limitations, viz. (a) their relatively high operating temperature (≥300° c) and (b) large power dissipation (≥1 Watt). Micromachined silicon based metal oxide gas sensors are being developed to overcome these limitations.The main part of power consumption in a micro-machined gas sensor consists of various thermal losses like conduction through bulk silicon substrate, convection in air from all exposed surfaces and radiation. The thermal characteristics of micro-machined metal oxide based gas sensors have to be optimized with respect to low power consumption, well controlled temperature distribution over the sensing layer and fast transient response. However microheater for the MEMS metal oxide gas sensors have not yet been optimized. In this paper we have developed a methodology (software) for designing and optimizing microheater for MEMS based gas sensor. Using this software we can estimate power requirement for achieving a particular temperature as well as the temperature distribution over the active layer.
Sensors and Actuators B: Chemical, 1996
The stable and low-power heating characteristics of a microheater are very important for the micro gas sensor. Membrane-type gas sensors have been fabricated by silicon IC technology. Steady-state thermal analysis by the finite-element method is performed to optimize the thermal properties of the gas sensor. From the analysis, the desirable size of the microheater for low power consumption is determined. The heating properties of fabricated poly-Si and Pt microheaters have been tested. The sensing characteristics of the packaged microsensor are also examined.
MEMS based Integrated Gas Sensor for NO2 and NH3
Numerous toxic and hazardous gases are used in various industrial applications. An exposure to these gases even in trace level can be lethal or it may lead to various chronic respiratory problems including shortness of breath, coughing and fluid in the lungs. Hence, detection of these gases is of utmost significance. This paper presents the design, fabrication and the characterization of a gas sensor using MEMS technologies. The device design is supported by Joule heating simulations. A Platinum micro-heater is integrated in the metal oxide based gas sensors, to achieve an operating temperature up to 343C. A Sensor temperature of 250C is achieved at 68mW, and 300C at 86mW power. SnO2 (sputtered) thin film is used as the sensing film and has been characterized for two gases, namely NO2 and NH3. Platinum is also used for making Inter Digitated Electrodes (IDE) with a spacing of ~30µm. A very significant response of approximately 159 (ΔR/R) at 150C for NO2, and 5.44 (ΔR/R) at 250C for ...
Sensors & Transducers, 2016
This paper presents a simple method to fabricate a vertical closed membrane structured gas sensor on silicon substrate using micromachining technology for methanol detection at lower concentration. An undoped tin dioxide thin film is deposited by DC magnetron sputtering technique on a pair of gold interdigitated microelectrodes of dimension 820 µm ´ 925 µm. A meander shaped platinum micro heater of dimension 1025 µm ´ 1000 µm is incorporated to provide optimum operating temperature (about 350 0C) for sensing operation. Energy dispersive X-ray spectroscopy is done to confirm the chemical composition of the sensor. Temperature coefficient of resistance of the inbuilt micro heater is found to be 0.0941 /0C. The sensor resistance shows significant change when micro heater voltage is varied from 1.5 V-3 V. I-V analysis of the sensor is carried out at 25 0C, 50 0C and 75 0C, and shifts in current through the sensor at different temperatures are observed. I-V characterization is also carri...
Chemosensors
The design of the heater plays a decisive role in the energy consumption, sensitivity, and speed of chemical sensors. The paper analyzes various options for the topology of meander-type platinum heaters in chemical sensors fabricated on thin dielectric membranes using MEMS-silicon technology. Comprehensive studies of the heater’s current–voltage characteristics have been carried out, heating rates have been measured at various currents, experimental temperature characteristics for various meander topologies have been obtained, heater options have been determined, and optimal heat transfer processes are ensured at a low power consumption of about 20–25 mW. Sensors with an optimal heater topology based on a double dielectric membrane were fabricated according to the described technological process, and sensory responses to 0.5 vol.% CH4 and 0.2% C3H8 were studied. The obtained results showed good results and confirmed the need to choose the optimal heater topology when designing senso...
Microheaters for Copper Oxide-Based Gas Sensors
2020
This paper describes two procedures developed for obtaining microheaters for copper oxide-based gas sensors. Different types of substrates (glass, SiO<sub>2</sub>/Si and ceramic) are investigated, as well as different configurations of geometric parameters for meandering heating elements. It is shown that microheaters made on glass, ceramic and SiO<sub>2</sub>/Si substrates can survive up to a temperature of ~400 °C, which allows their integration for applications in gas sensing devices to maintain necessary operating temperature.
Thermal and gas-sensing properties of planar-type micro gas sensor
Sensors and Actuators B: Chemical, 2000
A new planar-type micro gas sensor in which a gas-sensing layer was surrounded by a platinum heater horizontally on the same plane of a diaphragm was proposed to fit well to forming the gas-sensing layer by wet processes like spin-coating. The planar-type sensor simply fabricated by using only three masks for the photolithography processes shows very uniform temperature distribution over sensing layer and the device attached with a spin-coated thin layer of metal oxide of SnO , In O or WO showed a reasonable sensing 2 2 3 3 performance to gases at 3008C. q 2000 Elsevier Science S.A. All rights reserved.
Design and Simulation of Double-spiral Shape Micro-heater for Gas Sensing Applications
International Frequency Sensor Association Publishing, 2011
The paper presents the design and simulation of double spiral shape micro-heater using ANSYS 10.0 and MATLAB, which requires 12.5 mW-78.3 mW powers to create the temperature 181 °C-1002 °C for gas sensing applications. The results obtained from ANSYS simulation were verified using MATLAB Tool. A platinum-based bulk micro-machined hotplate of size 500 m × 500 m has been designed for fabrication as a multi-layer structure on a silicon substrate with thermal silicon dioxide as the supporting membrane, followed by LPCVD (Low pressure chemical vapor deposition) silicon nitride film. Gas sensing film (SnO 2 ) will be deposited on the interdigitated Pt electrodes formed on the PECVD oxide layer. The temperature uniformity of microhotplate (as it is essential for better sensing mechanism) based on double spiral heater has been reported in this paper. To estimate the resistance of the Pt heater, a 2000 Aº thick platinum film has been deposited by sputtering on silicon and its sheet resistance has been measured as 2.5 Ohm/□. We have used this value to calculate the resistance of Pt resistor, which was found 319 Ohm.