Thermal and mechanical analysis of micromachined gas sensors

Puigcorbé, J.; Vogel, Dietmar; Michel, B.; Vilà, A.; Gràcia, I.; Cané, C.; Morante, J.R.

doi:10.1088/0960-1317/13/5/304

Cited by 111 publications

(69 citation statements)

References 19 publications

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“…44. The linear behavior along the bridges changes into a parabolic one across the MHP, and have been observed in prior publications 60,64 . The maximum temperature, temperature profile, and gradient are affected by the bridge width.…”

Section: Resultssupporting

confidence: 65%

Novel High Temperature Materials for In-Situ Sensing Devices

Solzbacher¹,

Virkar²,

Rieth³

et al. 2009

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Abstract:The overriding goal of this project was to develop gas sensor materials and systems compatible with operation at temperatures from 500 to 700 °C. Gas sensors operating at these temperatures would be compatible with placement in fossil-energy exhaust streams close to the combustion chamber, and therefore have advantages for process regulation, and feedback for emissions controls. The three thrusts of our work included investigating thin film gas sensor materials based on metal oxide materials and electroceramic materials, and also development of microhotplate devices to support the gas sensing films. The metal oxide materials NiO, In 2 O 3 , and Ga 2 O 3 were investigated for their sensitivity to H 2 , NO x , and CO 2 , respectively, at high temperatures (T > 500 °C), where the sensing properties of these materials have received little attention. New ground was broken in achieving excellent gas sensor responses (>10) for temperatures up to 600 °C for NiO and In 2 O 3 materials. The gas sensitivity of these materials was decreasing as temperatures increased above 500 °C, which indicates that achieving strong sensitivities with these materials at very high temperatures (T ! 650 °C) will be a further challenge. The sensitivity, selectivity, stability, and reliability of these materials were investigated across a wide range of deposition conditions, temperatures, film thickness, as using surface active promoter materials.We also proposed to study the electroceramic materials BaZr (1-x) Y x O (3-x/2) and BaCe (2-x) Ca x S (4-x/2) for their ability to detect H 2 O and H 2 S, respectively. This report focuses on the properties and gas sensing characteristics of BaZr (1-x) Y x O (3-x/2) (Y-doped BaZrO 3 ), as significant difficulties were encounter in generating BaCe (2-x) Ca x S (4-x/2) sensors. Significant new results were achieved for Y-doped BaZrO 3 , including sensitivities of more than 60 atm -1 for H 2 O vapor at 400 °C. These results were achieved despite significant difficulties with a strong Ba deficiency in the deposited films, and difficulties with stress in the targets and films. Ultimately, these films achieved good sensitivity, selectivity, and reliability in our gas sensing tests.The final thrust of our project was to develop microhotpates. We proposed the use of SiC thin films for the heater of the microhotplate, but despite extensive efforts we were not able to secure a reliable source of SiC. An alternative microhotplate architecture using SiO 2 and Si 3 N 4 suspended membrane structures, and a polysilicon heater were developed, which could be fabricate at commercial MEMs foundries. These microhotplates were fabricated at Microtechnology Services Frankfurt (MSF) in Germany. The fabricated heaters were able to achieve temperatures > 600 °C using ~ 0.25 W, and when combined with In 2 O 3 films demonstrated sensor systems with sensor responses up to 50 for 25 ppm NO x , and time constants of less than 10 s. I. Executive SummaryThe most important goals of this project was to extend the performa...

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Section: Resultssupporting

confidence: 65%

Novel High Temperature Materials for In-Situ Sensing Devices

Solzbacher¹,

Virkar²,

Rieth³

et al. 2009

View full text Add to dashboard Cite

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“…This is likely due to the reaction with the passivation layer and the oxidation/reoxidation cycles taking place during the fabrication process. According to Puigcorbé et al, 11 Ti from the adhesion layer and N from the Si 3 N 4 passive layer probably migrate into the Pt film, reaching the Pt surface and modifying the heater electrical resistivity. Additionally, the intrinsic and thermal stresses of the Ti/Pt layer led to formation of hillocks on the heater surface, which has previously been observed for annealing temperatures above 650°C.…”

Section: Methodsmentioning

confidence: 99%

Planar Thermoelectric Microgenerators Based on Silicon Nanowires

Dávila

Tarancón

Kendig

et al. 2011

Journal of Elec Materi

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Silicon nanowires have been implemented in microfabricated structures to develop planar thermoelectric microgenerators (lTEGs) monolithically integrated in silicon to convert heat flow from thermal gradients naturally present in the environment into electrical energy. The compatibility of typical microfabrication technologies and the vapor-liquid-solid (VLS) mechanism employed for silicon nanowire growth has been evaluated. Low-thermal-mass suspended structures have been designed, simulated, and microfabricated on silicon-on-insulator substrates to passively generate thermal gradients and operate as microgenerators using silicon nanowires as thermoelectric material. Both electrical measurements to evaluate the connectivity of the nanowires and thermoreflectance imaging to determine the heat transfer along the device have been employed.

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“…Due to poor stability showed by polysilicon heaters formerly used in micro hotplates when operated at temperatures higher than 500°C (Puigcorbé et al 2003), a doped bulk crystalline silicon slab has been chosen for the realization of the radiating elements. Recent investigations (Spannhake et al 2006) have demonstrated high temperature realizations of silicon micro hot-plates using direct Joule heating of the SOI layer to attain temperatures close to 1,000°C.…”

Section: Device Fabricationmentioning

confidence: 99%

A MEMS-based thermal infrared emitter for an integrated NDIR spectrometer

et al. 2012

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A novel micromachined thermal infrared emitter using a heavily boron doped silicon slab as radiating element is presented. The fabrication process has been designed to allow the integration of such infrared emitters with an array of thermopile infrared detectors, with the aim of achieving an integrated non-dispersive infrared microspectrometer. A first set of infrared emitters with a common size for the doped silicon radiating slab (1,100 9 300 9 8 lm 3 ) has been successfully fabricated and characterized. The working temperature of the Jouleheated radiating slabs has been controlled by means of DC and pulsed electrical signals, achieving temperatures well beyond 700°C. The thermal time constant measured in pulsed operation, around 50 ms, is adequate to enable the direct electrical modulation of the emitted radiation up to a frequency of 5 Hz while maintaining the full modulation depth. The temperature distribution in the radiating elements has been analyzed using two different thermal imaging methods.

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Thermal and mechanical analysis of micromachined gas sensors

Cited by 111 publications

References 19 publications

Novel High Temperature Materials for In-Situ Sensing Devices

Novel High Temperature Materials for In-Situ Sensing Devices

Planar Thermoelectric Microgenerators Based on Silicon Nanowires

A MEMS-based thermal infrared emitter for an integrated NDIR spectrometer

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