Capacitive humidity sensor using a polyimide sensing film

Laconte, J.; Wilmart, V.; Raskin, J.-P.; Flandre, Denis

doi:10.1109/dtip.2003.1287041

Cited by 15 publications

(22 citation statements)

References 8 publications

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“…Within the 'more than Moore' trend, which aims at enhancing the capabilities of current microelectronics devices [1], polymers are increasingly used in the semiconductor industry as enabling materials for building or for the active layer in microsystems [2], with specific applications in molding [3][4][5], microfluidics [6] and sensing applications [7]. a low residual stress level of around 2 MPa in a 10 μm thick film, and a Young's modulus of about 8.5 GPa, see e.g.…”

Section: Introductionmentioning

confidence: 99%

“…the PI-2600 Series from HD Microsystems TM . Applications involve humidity sensing devices [7,[9][10][11] or pressure sensors [12][13][14], as well as a sacrificial layer for RF-MEMS switches [15][16][17]. PI can also act as a thermal insulating layer to prevent heat leakage to the substrate in nano-and microsystems thanks to a thermal conductivity of about 0.3 W m −1 K −1 [18].…”

Section: Introductionmentioning

confidence: 99%

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Poling Field Dependence of Longitudinal and Transverse Wave Velocities, Young's Modulus, and Poisson's Ratio in Piezoelectric Ceramics

Ogawa¹,

Ishii²,

Matsumoto³

et al. 2012

Jpn. J. Appl. Phys.

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The interest of using polyimide as a sacrificial and anchoring layer is demonstrated for post-processing surface micromachining and for the incorporation of metallic nanowires into microsystems. In addition to properties like a high planarization factor, a good resistance to most non-oxidizing acids and bases, and CMOS compatibility, polyimide can also be used as a mold for nanostructures after ion track-etching. Moreover, specific polyimide grades, such as PI-2611 from HD Microsystems TM , involve a thermal expansion coefficient similar to silicon and low internal stress. The process developed in this study permits higher gaps compared to the state-of-the-art, limits stiction problems with the substrate and is adapted to various top-layer materials. Most metals, semiconductors or ceramics will not be affected by the oxygen plasma required for polyimide etching. Released structures with vertical gaps from one to several tens of μm have been obtained, possibly using multiple layers of polyimide. Furthermore, patterned freestanding nanowires have been synthesized with diameters from 20 to 60 nm and up to 3 μm in length. These results have been applied to the fabrication of two specific devices: a generic nanomechanical testing lab-on-chip platform and a miniaturized ionization sensor.(Some figures may appear in colour only in the online journal) Polyimide (PI) is often selected for its high planarization factor, CMOS compatibility, tolerance to most chemical products used in microfabrication, and chemical resistance up to high temperatures. Moreover, depending on its formulation, PI can be spin-coated with thicknesses as high as several tens of μm and as low as 200 nm by diluting the precursor solution in its solvant [8]. A large range of possible gaps is thus allowed between a top movable clamped-clamped membrane or beam and a fixed bottom electrode lying on the substrate. New formulations of PI show additional interesting properties such as a thermal expansion coefficient similar to silicon (Si),

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Poling Field Dependence of Longitudinal and Transverse Wave Velocities, Young's Modulus, and Poisson's Ratio in Piezoelectric Ceramics

Ogawa¹,

Ishii²,

Matsumoto³

et al. 2012

Jpn. J. Appl. Phys.

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“…The thin soldermask layer protects the electrodes from shorting in the presence of liquid water while allowing the fringing fields to extend into the sensing environment. This is a significantly different architecture than used in other similar sensing structures, such as flexible humidity sensors, where the electrode coating absorbs water vapor from the surrounding air in proportion to the relative humidity and correspondingly increases the sensor capacitance [2]. The manufactured sensors were 83.82 mm long and 26.67 mm wide.…”

Section: Fringing Field Sensors In Flexible Pcb Technologymentioning

confidence: 99%

“…In particular, this type of sensor has been used in sensing the presence of water, present in either vapor (humidity) [2], liquid (moisture) [3], or solid (ice) [4] form. Additionally, this type of sensor has been used to measure the moisture content of objects and materials, such as soil [5], paper pulp [6], grain [7], wood [8], and animal hides [9].…”

Section: Introductionmentioning

confidence: 99%

“…However, other applications benefit from sensor implementations on flexible substrates where it is advantageous to conformally mount the sensor or sensor array directly onto a nonplanar surface [2,15]. Rigid printed circuit board technology has recently been demonstrated as a suitable technology for implementing low-cost, physically large capacitive fringing field sensors for applications involving moisture measurement [3,5].…”

Section: Introductionmentioning

confidence: 99%

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Capacitive Fringing Field Moisture Sensors Implemented in Flexible Printed Circuit Board Technology

Dean¹,

Hamilton²,

Baginski³

2014

Journal of Microelectronics and Electronic Packaging

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AbstractÀCapacitive fringing field sensors are often used in applications where moisture is detected, since the dielectric constant of liquid water is approximately 80 times greater than the dielectric constant of air. Most of these sensors, however, are realized using rigid substrates. Some applications would benefit from using a flexible capacitive fringing field sensor that could be conformally mounted on a nonplanar surface. Flexible printed circuit board technology is a mature commercially available process for manufacturing flexible electronics. This same technology can also be used to realize flexible fringing field moisture sensors where the patterned Cu foil is used for the electrodes and the soldermask coating electrically insulates the electrodes from being electrically shorted by moisture in the detection environment. Sensors were designed and characterized through flat and bending tests in air and in water. The tests demonstrated that bending a sensor over a radius of curvature as small as 13.7 mm had no measurable impact on sensor performance in air or in water. The sensors achieved a 3:1 increase in capacitance when immersed in water compared with in air.

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Off-Chip/On-Foil Passive and Active Components

Elsobky

2022

Ultra-Thin Sensors and Data Conversion Techniques for Hybrid System-in-Foil

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Capacitive humidity sensor using a polyimide sensing film

Cited by 15 publications

References 8 publications

Poling Field Dependence of Longitudinal and Transverse Wave Velocities, Young's Modulus, and Poisson's Ratio in Piezoelectric Ceramics

Poling Field Dependence of Longitudinal and Transverse Wave Velocities, Young's Modulus, and Poisson's Ratio in Piezoelectric Ceramics

Capacitive Fringing Field Moisture Sensors Implemented in Flexible Printed Circuit Board Technology

Off-Chip/On-Foil Passive and Active Components

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