Micro thermal shear stress sensor based on vacuum anodic bonding and bulk-micromachining

Liang, Yi; Ou, Yi; Shi, Shali; Ma, Jin; Chen, Dapeng; Ye, Tianchun

doi:10.1088/1674-1056/17/6/031

Cited by 3 publications

(3 citation statements)

References 8 publications

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“…For example, a polysilicon heater with dimensions 150 µm × 3 µm × 0.25 µm and MHR = 1.33 had the sensitivity of 100 mV/Pa [67], whereas another polysilicon silicon heater having dimensions 80 µm × 2 µm × 0.3 µm and MHR = 3.12 has sensitivity of 1540 mV/Pa [76], despite the fact that the hot-film length in the latter case was almost half that of the former. Similarly, in another study [78], the thermal resistance of a titanium/platinum heater on silicon nitride membrane having MHR = 2 was 6.8 °C/mW, whereas our tungsten hot-film sensor FS3 (with MHR=2) on silicon oxide membrane achieved a thermal resistance 12 °C/mW, indicating a much better thermal isolation with silicon oxide membrane, which has lower thermal conductivity than silicon nitride. The reported thermal conductivity value of silicon oxide is 1.4 W/(m-K), whereas that for silicon nitride is 20 W/(m-K) [118], which in case of thin films may vary significantly depending upon the deposition parameters (e.g., thermal conductivity of a silicon nitride thin film is reported as 2.3 W/(m-K) [91], while that for silicon oxide thin film it is documented as 1.1 W/(m-K) [136]).…”

Section: Resultssupporting

confidence: 67%

“…Thermal performance of un-etched thermal flow sensors has also been evaluated in the past. For example, Liang et al [78] achieved a thermal resistance of 0.2 °C/mW for a titanium/platinum alloy strip of size 100 µm × 2 µm × 0.2 µm, directly fabricated on a silicon substrate. The thermal resistance in case of our FS1 sensor is comparatively higher, most likely, due to the fact that instead of silicon substrate a SOI substrate has been used, which has a very low thermal conductivity silicon oxide layer just underneath the hot-film.…”

Section: Resultsmentioning

confidence: 99%

“…A quick look at Table 3, Table 4 and Table 5 reveals that among ceramics, silicon nitride is the most widely used membrane material for thermal isolation of MEMS thermal flow sensors [22,25,26,33,39,59,60,63,64,65,67,68,69,70,71,72,73,75,76,77,78,79,80,81,85,86,89,127]. To further reduce the heat conduction, bi-layer membranes of silicon nitride and silicon oxides have also been reported [3,8,24,30,31,34,42,83,117].…”

Section: Introductionmentioning

confidence: 99%

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Sensitivity Enhancement of Silicon-on-Insulator CMOS MEMS Thermal Hot-Film Flow Sensors by Minimizing Membrane Conductive Heat Losses

Mehmood

Haneef

Ali

et al. 2019

Sensors

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Minimizing conductive heat losses in Micro-Electro-Mechanical-Systems (MEMS) thermal (hot-film) flow sensors is the key to minimize the sensors’ power consumption and maximize their sensitivity. Through a comprehensive review of literature on MEMS thermal (calorimetric, time of flight, hot-film/hot-film) flow sensors published during the last two decades, we establish that for curtailing conductive heat losses in the sensors, researchers have either used low thermal conductivity substrate materials or, as a more effective solution, created low thermal conductivity membranes under the heaters/hot-films. However, no systematic experimental study exists that investigates the effect of membrane shape, membrane size, heater/hot-film length and M e m b r a n e (size) to H e a t e r (hot-film length) Ratio (MHR) on sensors’ conductive heat losses. Therefore, in this paper we have provided experimental evidence of dependence of conductive heat losses in membrane based MEMS hot-film flow sensors on MHR by using eight MEMS hot-film flow sensors, fabricated in a 1 µm silicon-on-insulator (SOI) CMOS foundry, that are thermally isolated by square and circular membranes. Experimental results demonstrate that: (a) thermal resistance of both square and circular membrane hot-film sensors increases with increasing MHR, and (b) conduction losses in square membrane based hot-film flow sensors are lower than the sensors having circular membrane. The difference (or gain) in thermal resistance of square membrane hot-film flow sensors viz-a-viz the sensors on circular membrane, however, decreases with increasing MHR. At MHR = 2, this difference is 5.2%, which reduces to 3.0% and 2.6% at MHR = 3 and MHR = 4, respectively. The study establishes that for membrane based SOI CMOS MEMS hot-film sensors, the optimum MHR is 3.35 for square membranes and 3.30 for circular membranes, beyond which the gain in sensors’ thermal efficiency (thermal resistance) is not economical due to the associated sharp increase in the sensors’ (membrane) size, which makes sensors more expensive as well as fragile. This paper hence, provides a key guideline to MEMS researchers for designing the square and circular membranes-supported micro-machined thermal (hot-film) flow sensors that are thermally most-efficient, mechanically robust and economically viable.

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Section: Resultssupporting

confidence: 67%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Sensitivity Enhancement of Silicon-on-Insulator CMOS MEMS Thermal Hot-Film Flow Sensors by Minimizing Membrane Conductive Heat Losses

Mehmood

Haneef

Ali

et al. 2019

Sensors

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A Wafer-Level Sn-Rich Au—Sn Bonding Technique and Its Application in Surface Plasmon Resonance Sensors

Xu¹,

Lv²,

Wei³

et al. 2014

Chinese Phys. Lett.

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Sn-rich Au-Sn solder bonding is systematically investigated. High shear strength (64 MPa) and good hermeticity (a leak rate lower than 1 × 10 −7 torr•l/s) are obtained for Au-Sn solder with 54 wt% Sn bonded at 310 ∘ C. The AuSn2 phase with the highest Vickers-hardness among the four stable intermetallic compounds of the Au-Sn system makes a major contribution to the high bonding strength. This bonding technique has been successfully used to package the Surface Plasmon Resonance (SPR) sensors. The Sn-rich Au-Sn solder bonding provides a reliable, low-cost, low-temperature and wafer-level hermetic packaging solution for the micro-electromechanical system devices and has potential applications in high-end biomedical sensors.

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A novel method for sacrificial layer release in MEMS devices fabrication

Shi¹,

Chen²,

Jing³

et al. 2010

Chinese Phys. B

Self Cite

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During the forming process of the free-standing structure or the functional cavity when releasing the high aspect ratio sacrificial layer, such structures tend to stick to the substrate due to capillary force. This paper describes the application of pull-in length conception as design rules to a novel 'dimpled' method in releasing sacrificial layer. Based on the conception of pull-in length in adhering phenomenon, the fabrication and releasing sacrificial layer methods using micro bumps based on the silicon substrate were presented. According to the thermal isolation performances of one kind of micro electromechanical system device thermal shear stress sensor, the sacrificial layers were validated to be successfully released.

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Micro thermal shear stress sensor based on vacuum anodic bonding and bulk-micromachining

Cited by 3 publications

References 8 publications

Sensitivity Enhancement of Silicon-on-Insulator CMOS MEMS Thermal Hot-Film Flow Sensors by Minimizing Membrane Conductive Heat Losses

Sensitivity Enhancement of Silicon-on-Insulator CMOS MEMS Thermal Hot-Film Flow Sensors by Minimizing Membrane Conductive Heat Losses

A Wafer-Level Sn-Rich Au—Sn Bonding Technique and Its Application in Surface Plasmon Resonance Sensors

A novel method for sacrificial layer release in MEMS devices fabrication

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