The nanogap pirani - a pressure sensor with superior linearity in atmospheric pressure range

Khosraviani, Kourosh; Leung, Albert M.

doi:10.1109/memsys.2008.4443802

Cited by 12 publications

(5 citation statements)

References 7 publications

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“…In our previous work [17], the sacrificial layer was a continuous film and the microbridge and the electrical connections (both ends of the microbridge) sat on top of it. The bridge remained anchored to the substrate after the release step due to the large geometry of the electrical connections compared to the microbridge width itself.…”

Section: Design and Fabricationmentioning

confidence: 99%

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The nanogap Pirani—a pressure sensor with superior linearity in an atmospheric pressure range

Khosraviani

Leung

2009

J. Micromech. Microeng.

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We have designed and fabricated a surface micromachined Pirani pressure sensor with an extremely narrow gap between its heater and heatsink (substrate) with superior output linearity in the atmospheric pressure range. The gap size of the device has been reduced to 50 nm by using a layer of PECVD amorphous silicon as a sacrificial layer and a xenon difluoride (XeF 2 ) gas phase etching technique. Such a narrow gap pushes the transition from molecular to continuum heat conduction to pressures beyond 200 kPa. The higher transition pressure increases the measurement range and sensitivity of the gauge in atmospheric pressures. The gas phase etching of the sacrificial layer eliminates stiction problems related to a wet etching process. The active area of the sensor is only a 6 × 50 μm 2 microbridge anchored to the substrate at both ends. An innovative fabrication technique was developed which resulted in a virtually flat microbridge with improved mechanical robustness. This process enabled us to have a very well-controlled gap between the microbridge and the substrate. The device was tested in a constant heater temperature mode with pressure ranges from 0.1 to 720 kPa. The heater power was only 3 mW at 101 kPa (atmospheric pressure), which increased to about 8 mW at 720 kPa. The output sensitivity and nonlinearity of the device were 0.55% per kPa at 101 kPa and ±13% of the output full scale, respectively.

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Section: Design and Fabricationmentioning

confidence: 99%

“…In [17], we presented a surface micromachined Pirani gauge which consisted of a heated microbridge on top of a 50 nm thick sputtered silicon sacrificial layer. The sacrificial layer was etched by xenon difluoride (XeF 2 ) gas that leaves the microbridge suspended over the substrate with no need for CPD.…”

Section: Introductionmentioning

confidence: 99%

The nanogap Pirani—a pressure sensor with superior linearity in an atmospheric pressure range

Khosraviani

Leung

2009

J. Micromech. Microeng.

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“…A large number of micromachined Pirani gauges have been developed so far [4,11,15,16,[18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] using a variety of processes and geometries. With respect to their geometry, however, they can be divided into two groups.…”

Section: Introductionmentioning

confidence: 99%

Tube-shaped Pirani gauge forin situhermeticity monitoring of SiN thin-film encapsulation

Santagata¹,

Creemer²,

Iervolino³

et al. 2012

J. Micromech. Microeng.

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Here the integration of a tube-shaped Pirani gauge with a SiN thin-film encapsulation process is presented. The tube geometry gives the sensor a very low detection limit with a small footprint, since the tube is buried under the silicon surface. The Pirani tube is very suitable for in situ evaluation of MEMS vacuum packaging. Moreover, since the Pirani gap is all around the tube and deep below the silicon surface, the deflection of the encapsulation shell is not a concern and wafer-level measurement of the device is possible. Pirani tubes with different lengths are encapsulated inside SiN micropackages in order to measure the resulting vacuum level achieved after the encapsulation step. The longest tube shows a detection limit of 0.1 Pa for a noise level of 50 μV and it has a footprint of only 0.006 mm 2 . The pressure inside the sealed micropackage was extracted to be 0.7 kPa. Furthermore, the pressure is monitored over time to evaluate the hermeticity of the packages. A leak rate of 8×10 −18 Pa m 3 s −1 was measured over four months time.

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“…The first MEMS Pirani-like vacuum sensors were proposed starting from the mid-eighties [6]. Since then, an impressive number of different designs have been proposed in the literature [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21], while commercial applications have begun to appear in last decade [22]. Exploitation of standard IC (integrated circuit) fabrication technologies, followed by micromachining steps (post-processing), to produce MEMS Pirani sensors has been proposed and demonstrated since the first pioneering works [6][7][8][9], resulting in a viable approach to reduce development and production costs and integrate the sensors on the same substrate as the readout electronic interfaces [9][10][11].…”

Section: Introductionmentioning

confidence: 99%

“…Miniaturization allowed improving also the typically very low sensitivity exhibited by traditional Pirani gauges at atmospheric pressure, since the shorter the air gap, the higher the pressure at which the sensitivity starts to drop. Gaps of a few microns are sufficient to obtain acceptable performances up to atmospheric pressure [8], while extension of the operating range up to even higher pressures can be obtained pushing some dimensions down to the nanometer region [20,21]. On the other hand, the lower end of the pressure operating range is determined by two main issues: noise and offset drift.…”

Section: Introductionmentioning

confidence: 99%

A CMOS compatible micro-Pirani vacuum sensor based on mutual heat transfer with 5-decade operating range and 0.3 Pa detection limit

Piotto

Cesta

Bruschi

2017

Sensors and Actuators A: Physical

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The nanogap pirani - a pressure sensor with superior linearity in atmospheric pressure range

Cited by 12 publications

References 7 publications

The nanogap Pirani—a pressure sensor with superior linearity in an atmospheric pressure range

The nanogap Pirani—a pressure sensor with superior linearity in an atmospheric pressure range

Tube-shaped Pirani gauge forin situhermeticity monitoring of SiN thin-film encapsulation

A CMOS compatible micro-Pirani vacuum sensor based on mutual heat transfer with 5-decade operating range and 0.3 Pa detection limit

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