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Fabrication and Characterization of a CMOS-MEMS Humidity Sensor.

Dennis JO, Ahmed AY, Khir MH - Sensors (Basel) (2015)

Bottom Line: The output voltage is found to be linear from 0.585 mV to 3.250 mV as the humidity increased from 35% RH to 60% RH, with sensitivity of 0.107 mV/% RH; and again linear from 3.250 mV to 30.580 mV as the humidity level increases from 60% RH to 95% RH, with higher sensitivity of 0.781 mV/% RH.On the other hand, the sensitivity of the humidity sensor increases linearly from 0.102 mV/% RH to 0.501 mV/% RH with increase in the temperature from 40 °C to 80 °C and a maximum hysteresis of 0.87% RH is found at a relative humidity of 80%.Finally, the CMOS-MEMS humidity sensor showed comparable response, recovery, and repeatability of measurements in three cycles as compared to a standard sensor that directly measures humidity in % RH.

View Article: PubMed Central - PubMed

Affiliation: Department of Fundamental and Applied Sciences, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, Perak Darul Ridzuan 32610, Malaysia. johndennis@petronas.com.my.

ABSTRACT
This paper reports on the fabrication and characterization of a Complementary Metal Oxide Semiconductor-Microelectromechanical System (CMOS-MEMS) device with embedded microheater operated at relatively elevated temperatures (40 °C to 80 °C) for the purpose of relative humidity measurement. The sensing principle is based on the change in amplitude of the device due to adsorption or desorption of humidity on the active material layer of titanium dioxide (TiO2) nanoparticles deposited on the moving plate, which results in changes in the mass of the device. The sensor has been designed and fabricated through a standard 0.35 µm CMOS process technology and post-CMOS micromachining technique has been successfully implemented to release the MEMS structures. The sensor is operated in the dynamic mode using electrothermal actuation and the output signal measured using a piezoresistive (PZR) sensor connected in a Wheatstone bridge circuit. The output voltage of the humidity sensor increases from 0.585 mV to 30.580 mV as the humidity increases from 35% RH to 95% RH. The output voltage is found to be linear from 0.585 mV to 3.250 mV as the humidity increased from 35% RH to 60% RH, with sensitivity of 0.107 mV/% RH; and again linear from 3.250 mV to 30.580 mV as the humidity level increases from 60% RH to 95% RH, with higher sensitivity of 0.781 mV/% RH. On the other hand, the sensitivity of the humidity sensor increases linearly from 0.102 mV/% RH to 0.501 mV/% RH with increase in the temperature from 40 °C to 80 °C and a maximum hysteresis of 0.87% RH is found at a relative humidity of 80%. The sensitivity is also frequency dependent, increasing from 0.500 mV/% RH at 2 Hz to reach a maximum value of 1.634 mV/% RH at a frequency of 12 Hz, then decreasing to 1.110 mV/% RH at a frequency of 20 Hz. Finally, the CMOS-MEMS humidity sensor showed comparable response, recovery, and repeatability of measurements in three cycles as compared to a standard sensor that directly measures humidity in % RH.

No MeSH data available.


(a) Schematic of electrothermal actuation method and piezoresistive sensing; (b) A magnified view of PZRLR; (c) Wheatstone bridge circuit for measurement of the output signal.
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sensors-15-16674-f003: (a) Schematic of electrothermal actuation method and piezoresistive sensing; (b) A magnified view of PZRLR; (c) Wheatstone bridge circuit for measurement of the output signal.

Mentions: The CMOS-MEMS device is operated in the dynamic mode using electrothermal actuation by applying an AC-current through the embedded microheater as shown in Figure 3a to produce oscillations of the plate in the out-of-plan z direction. These vibrations produce stress at the anchor points of the four supporting beams and this stress changes the resistance of the PZRs, which can be measured using a Wheatstone bridge circuit. In the initial experimental setup on which the results of this paper are based, a single longitudinal PZRLR (where the subscript LR stands for the lower right hand side of the device) is connected to three external resistors, R1, R2, and R3 of the same values as those of the PZR to construct a Wheatstone bridge circuit configuration. One of the three external resistors, R3, is a variable resistor to adjust the Wheatstone bridge circuit. Figure 3b shows a magnified view of the PZRLR, while Figure 3c shows the Wheatstone bridge circuit configuration to convert changes in the resistance of the PZRLR to voltage output Vout and is biased using a DC voltage input Vin of 3 V.


Fabrication and Characterization of a CMOS-MEMS Humidity Sensor.

Dennis JO, Ahmed AY, Khir MH - Sensors (Basel) (2015)

(a) Schematic of electrothermal actuation method and piezoresistive sensing; (b) A magnified view of PZRLR; (c) Wheatstone bridge circuit for measurement of the output signal.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4541900&req=5

sensors-15-16674-f003: (a) Schematic of electrothermal actuation method and piezoresistive sensing; (b) A magnified view of PZRLR; (c) Wheatstone bridge circuit for measurement of the output signal.
Mentions: The CMOS-MEMS device is operated in the dynamic mode using electrothermal actuation by applying an AC-current through the embedded microheater as shown in Figure 3a to produce oscillations of the plate in the out-of-plan z direction. These vibrations produce stress at the anchor points of the four supporting beams and this stress changes the resistance of the PZRs, which can be measured using a Wheatstone bridge circuit. In the initial experimental setup on which the results of this paper are based, a single longitudinal PZRLR (where the subscript LR stands for the lower right hand side of the device) is connected to three external resistors, R1, R2, and R3 of the same values as those of the PZR to construct a Wheatstone bridge circuit configuration. One of the three external resistors, R3, is a variable resistor to adjust the Wheatstone bridge circuit. Figure 3b shows a magnified view of the PZRLR, while Figure 3c shows the Wheatstone bridge circuit configuration to convert changes in the resistance of the PZRLR to voltage output Vout and is biased using a DC voltage input Vin of 3 V.

Bottom Line: The output voltage is found to be linear from 0.585 mV to 3.250 mV as the humidity increased from 35% RH to 60% RH, with sensitivity of 0.107 mV/% RH; and again linear from 3.250 mV to 30.580 mV as the humidity level increases from 60% RH to 95% RH, with higher sensitivity of 0.781 mV/% RH.On the other hand, the sensitivity of the humidity sensor increases linearly from 0.102 mV/% RH to 0.501 mV/% RH with increase in the temperature from 40 °C to 80 °C and a maximum hysteresis of 0.87% RH is found at a relative humidity of 80%.Finally, the CMOS-MEMS humidity sensor showed comparable response, recovery, and repeatability of measurements in three cycles as compared to a standard sensor that directly measures humidity in % RH.

View Article: PubMed Central - PubMed

Affiliation: Department of Fundamental and Applied Sciences, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, Perak Darul Ridzuan 32610, Malaysia. johndennis@petronas.com.my.

ABSTRACT
This paper reports on the fabrication and characterization of a Complementary Metal Oxide Semiconductor-Microelectromechanical System (CMOS-MEMS) device with embedded microheater operated at relatively elevated temperatures (40 °C to 80 °C) for the purpose of relative humidity measurement. The sensing principle is based on the change in amplitude of the device due to adsorption or desorption of humidity on the active material layer of titanium dioxide (TiO2) nanoparticles deposited on the moving plate, which results in changes in the mass of the device. The sensor has been designed and fabricated through a standard 0.35 µm CMOS process technology and post-CMOS micromachining technique has been successfully implemented to release the MEMS structures. The sensor is operated in the dynamic mode using electrothermal actuation and the output signal measured using a piezoresistive (PZR) sensor connected in a Wheatstone bridge circuit. The output voltage of the humidity sensor increases from 0.585 mV to 30.580 mV as the humidity increases from 35% RH to 95% RH. The output voltage is found to be linear from 0.585 mV to 3.250 mV as the humidity increased from 35% RH to 60% RH, with sensitivity of 0.107 mV/% RH; and again linear from 3.250 mV to 30.580 mV as the humidity level increases from 60% RH to 95% RH, with higher sensitivity of 0.781 mV/% RH. On the other hand, the sensitivity of the humidity sensor increases linearly from 0.102 mV/% RH to 0.501 mV/% RH with increase in the temperature from 40 °C to 80 °C and a maximum hysteresis of 0.87% RH is found at a relative humidity of 80%. The sensitivity is also frequency dependent, increasing from 0.500 mV/% RH at 2 Hz to reach a maximum value of 1.634 mV/% RH at a frequency of 12 Hz, then decreasing to 1.110 mV/% RH at a frequency of 20 Hz. Finally, the CMOS-MEMS humidity sensor showed comparable response, recovery, and repeatability of measurements in three cycles as compared to a standard sensor that directly measures humidity in % RH.

No MeSH data available.