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3602 KiB

Open AccessArticle

A CMOS MEMS Humidity Sensor Enhanced by a Capacitive Coupling Structure

by Jian-Qiu Huang, Baoye Li and Wenhao Chen

Micromachines 2016, 7(5), 74; https://doi.org/10.3390/mi7050074 - 26 Apr 2016

Cited by 16 | Viewed by 7464

Abstract

A capacitive coupling structure is developed to improve the performances of a capacitive complementary metal oxide semiconductor (CMOS) microelectromechanical system (MEMS) humidity sensor. The humidity sensor was fabricated by a post-CMOS process. Silver nanowires were dispersed onto the top of a conventional interdigitated [...] Read more.

A capacitive coupling structure is developed to improve the performances of a capacitive complementary metal oxide semiconductor (CMOS) microelectromechanical system (MEMS) humidity sensor. The humidity sensor was fabricated by a post-CMOS process. Silver nanowires were dispersed onto the top of a conventional interdigitated capacitive structure to form a coupling electrode. Unlike a conventional structure, a thinner sensitive layer was employed to increase the coupling capacitance which dominated the sensitive capacitance of the humidity sensor. Not only static properties but also dynamic properties were found to be better with the aid of coupling capacitance. At 25 °C, the sensitive capacitance was 11.3 pF, the sensitivity of the sensor was measured to be 32.8 fF/%RH and the hysteresis was measured to be 1.0 %RH. Both a low temperature coefficient and a fast response (10 s)/recovery time (17 s) were obtained. Full article

(This article belongs to the Special Issue CMOS-MEMS Sensors and Devices)

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5258 KiB

Open AccessArticle

Fabrication and Measurement of a Suspended Nanochannel Microbridge Resonator Monolithically Integrated with CMOS Readout Circuitry

by Gabriel Vidal-Álvarez, Eloi Marigó, Francesc Torres and Núria Barniol

Micromachines 2016, 7(3), 40; https://doi.org/10.3390/mi7030040 - 2 Mar 2016

Cited by 6 | Viewed by 5616

Abstract

We present the fabrication and characterization of a suspended microbridge resonator with an embedded nanochannel. The suspended microbridge resonator is electrostatically actuated, capacitively sensed, and monolithically integrated with complementary metal-oxide-semiconductor (CMOS) readout circuitry. The device is fabricated using the back end of line [...] Read more.

We present the fabrication and characterization of a suspended microbridge resonator with an embedded nanochannel. The suspended microbridge resonator is electrostatically actuated, capacitively sensed, and monolithically integrated with complementary metal-oxide-semiconductor (CMOS) readout circuitry. The device is fabricated using the back end of line (BEOL) layers of the AMS 0.35 μm commercial CMOS technology, interconnecting two metal layers with a contact layer. The fabricated device has a 6 fL capacity and has one of the smallest embedded channels so far. It is able to attain a mass sensitivity of 25 ag/Hz using a fully integrable electrical transduction. Full article

(This article belongs to the Special Issue CMOS-MEMS Sensors and Devices)

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3655 KiB

Open AccessArticle

CMOS-NEMS Copper Switches Monolithically Integrated Using a 65 nm CMOS Technology

by Jose Luis Muñoz-Gamarra, Arantxa Uranga and Nuria Barniol

Micromachines 2016, 7(2), 30; https://doi.org/10.3390/mi7020030 - 15 Feb 2016

Cited by 14 | Viewed by 6224

Abstract

This work demonstrates the feasibility to obtain copper nanoelectromechanical (NEMS) relays using a commercial complementary metal oxide semiconductor (CMOS) technology (ST 65 nm) following an intra CMOS-MEMS approach. We report experimental demonstration of contact-mode nano-electromechanical switches obtaining low operating voltage (5.5 V), good [...] Read more.

This work demonstrates the feasibility to obtain copper nanoelectromechanical (NEMS) relays using a commercial complementary metal oxide semiconductor (CMOS) technology (ST 65 nm) following an intra CMOS-MEMS approach. We report experimental demonstration of contact-mode nano-electromechanical switches obtaining low operating voltage (5.5 V), good I_ON/I_OFF (10³) ratio, abrupt subthreshold swing (4.3 mV/decade) and minimum dimensions (3.50 μm × 100 nm × 180 nm, and gap of 100 nm). With these dimensions, the operable Cell area of the switch will be 3.5 μm (length) × 0.2 μm (100 nm width + 100 nm gap) = 0.7 μm² which is the smallest reported one using a top-down fabrication approach. Full article

(This article belongs to the Special Issue CMOS-MEMS Sensors and Devices)

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10702 KiB

Open AccessArticle

Fabrication of a Micromachined Capacitive Switch Using the CMOS-MEMS Technology

by Cheng-Yang Lin, Cheng-Chih Hsu and Ching-Liang Dai

Micromachines 2015, 6(11), 1645-1654; https://doi.org/10.3390/mi6111447 - 2 Nov 2015

Cited by 15 | Viewed by 7017

Abstract

The study investigates the design and fabrication of a micromachined radio frequency (RF) capacitive switch using the complementary metal oxide semiconductor-microelectromechanical system (CMOS-MEMS) technology. The structure of the micromachined switch is composed of a membrane, eight springs, four inductors, and coplanar waveguide (CPW) [...] Read more.

The study investigates the design and fabrication of a micromachined radio frequency (RF) capacitive switch using the complementary metal oxide semiconductor-microelectromechanical system (CMOS-MEMS) technology. The structure of the micromachined switch is composed of a membrane, eight springs, four inductors, and coplanar waveguide (CPW) lines. In order to reduce the actuation voltage of the switch, the springs are designed as low stiffness. The finite element method (FEM) software CoventorWare is used to simulate the actuation voltage and displacement of the switch. The micromachined switch needs a post-CMOS process to release the springs and membrane. A wet etching is employed to etch the sacrificial silicon dioxide layer, and to release the membrane and springs of the switch. Experiments show that the pull-in voltage of the switch is 12 V. The switch has an insertion loss of 0.8 dB at 36 GHz and an isolation of 19 dB at 36 GHz. Full article

(This article belongs to the Special Issue CMOS-MEMS Sensors and Devices)

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4465 KiB

Open AccessArticle

The Fringe-Capacitance of Etching Holes for CMOS-MEMS

by Yi-Ta Wang, Yuh-Chung Hu, Wen-Chang Chu and Pei-Zen Chang

Micromachines 2015, 6(11), 1617-1628; https://doi.org/10.3390/mi6111445 - 28 Oct 2015

Cited by 8 | Viewed by 12417

Abstract

Movable suspended microstructures are the common feature of sensors or devices in the fields of Complementary-Metal-Oxide-Semiconductors and Micro-Electro-Mechanical Systems which are usually abbreviated as CMOS-MEMS. To suspend the microstructures, it is commonly to etch the sacrificial layer under the microstructure layer. For large-area [...] Read more.

Movable suspended microstructures are the common feature of sensors or devices in the fields of Complementary-Metal-Oxide-Semiconductors and Micro-Electro-Mechanical Systems which are usually abbreviated as CMOS-MEMS. To suspend the microstructures, it is commonly to etch the sacrificial layer under the microstructure layer. For large-area microstructures, it is necessary to design a large number of etching holes on the microstructure to enhance the etchant uniformly and rapidly permeate into the sacrificial layer. This paper aims at evaluating the fringe capacitance caused by etching holes on microstructures and developing empirical formulas. The formula of capacitance compensation term is derived by curve-fitting on the simulation results by the commercial software ANSYS. Compared with the ANSYS simulation, the deviation of the present formula is within ±5%. The application to determine the capacitance of an electrostatic micro-beam with etching holes is demonstrated in a microstructure experiment, which agrees very well with the experimental data, and the maximum deviation is within ±8%. The present formula is with simple form, wide application range, high accuracy, and easy to use. It is expected to provide the micro-device designers to estimate the capacitance of microstructures with etching holes and predominate in the device characteristics. Full article

(This article belongs to the Special Issue CMOS-MEMS Sensors and Devices)

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3594 KiB

Open AccessArticle

Multifunctional Platform with CMOS-Compatible Tungsten Microhotplate for Pirani, Temperature, and Gas Sensor

by Jiaqi Wang and Jun Yu

Micromachines 2015, 6(11), 1597-1605; https://doi.org/10.3390/mi6111443 - 28 Oct 2015

Cited by 7 | Viewed by 6516

Abstract

A multifunctional platform based on the microhotplate was developed for applications including a Pirani vacuum gauge, temperature, and gas sensor. It consisted of a tungsten microhotplate and an on-chip operational amplifier. The platform was fabricated in a standard complementary metal oxide semiconductor (CMOS) [...] Read more.

A multifunctional platform based on the microhotplate was developed for applications including a Pirani vacuum gauge, temperature, and gas sensor. It consisted of a tungsten microhotplate and an on-chip operational amplifier. The platform was fabricated in a standard complementary metal oxide semiconductor (CMOS) process. A tungsten plug in standard CMOS process was specially designed as the serpentine resistor for the microhotplate, acting as both heater and thermister. With the sacrificial layer technology, the microhotplate was suspended over the silicon substrate with a 340 nm gap. The on-chip operational amplifier provided a bias current for the microhotplate. This platform has been used to develop different kinds of sensors. The first one was a Pirani vacuum gauge ranging from 1^-1 to 10⁵ Pa. The second one was a temperature sensor ranging from -20 to 70 °C. The third one was a thermal-conductivity gas sensor, which could distinguish gases with different thermal conductivities in constant gas pressure and environment temperature. In the fourth application, with extra fabrication processes including the deposition of gas-sensitive film, the platform was used as a metal-oxide gas sensor for the detection of gas concentration. Full article

(This article belongs to the Special Issue CMOS-MEMS Sensors and Devices)

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5281 KiB

Open AccessArticle

A Surface Micromachined CMOS MEMS Humidity Sensor

by Jian-Qiu Huang, Fei Li, Min Zhao and Kai Wang

Micromachines 2015, 6(10), 1569-1576; https://doi.org/10.3390/mi6101440 - 16 Oct 2015

Cited by 15 | Viewed by 6542

Abstract

This paper reports a CMOS MEMS (complementary metal oxide semiconductor micro electromechanical system) piezoresistive humidity sensor fabricated by a surface micromachining process. Both pre-CMOS and post-CMOS technologies were used to fabricate the piezoresistive humidity sensor. Compared with a bulk micromachined humidity sensor, the [...] Read more.

This paper reports a CMOS MEMS (complementary metal oxide semiconductor micro electromechanical system) piezoresistive humidity sensor fabricated by a surface micromachining process. Both pre-CMOS and post-CMOS technologies were used to fabricate the piezoresistive humidity sensor. Compared with a bulk micromachined humidity sensor, the machining precision and the sizes of the surface micromachined humidity sensor were both improved. The package and test systems of the sensor were designed. According to the test results, the sensitivity of the sensor was 7 mV/%RH (relative humidity) and the linearity of the sensor was 1.9% at 20 °C. Both the sensitivity and linearity were not sensitive to the temperature but the curve of the output voltage shifted with the temperature. The hysteresis of the humidity sensor decreased from 3.2% RH to 1.9% RH as the temperature increased from 10 to 40 °C. The recovery time of the sensor was 85 s at room temperature (25 °C). Full article

(This article belongs to the Special Issue CMOS-MEMS Sensors and Devices)

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13449 KiB

Open AccessArticle

Manufacturing and Characterization of a Thermoelectric Energy Harvester Using the CMOS-MEMS Technology

by Shih-Wen Peng, Po-Jen Shih and Ching-Liang Dai

Micromachines 2015, 6(10), 1560-1568; https://doi.org/10.3390/mi6101439 - 16 Oct 2015

Cited by 33 | Viewed by 5702

Abstract

The fabrication and characterization of a thermoelectric energy harvester using the complementary metal oxide semiconductor (CMOS)-microelectromechanical system (MEMS) technology were presented. The thermoelectric energy harvester is composed of eight circular energy harvesting cells, and each cell consists of 25 thermocouples in series. The [...] Read more.

The fabrication and characterization of a thermoelectric energy harvester using the complementary metal oxide semiconductor (CMOS)-microelectromechanical system (MEMS) technology were presented. The thermoelectric energy harvester is composed of eight circular energy harvesting cells, and each cell consists of 25 thermocouples in series. The thermocouples are made of p-type and n-type polysilicons. The output power of the energy harvester relies on the number of the thermocouples. In order to enhance the output power, the energy harvester increases the thermocouple number per area. The energy harvester requires a post-CMOS process to etch the sacrificial silicon dioxide layer and the silicon substrate to release the suspended structures of hot part. The experimental results show that the energy harvester has an output voltage per area of 0.178 mV·mm⁻²·K⁻¹ and a power factor of 1.47 × 10⁻³ pW·mm⁻²·K⁻². Full article

(This article belongs to the Special Issue CMOS-MEMS Sensors and Devices)

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Review

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4719 KiB

Open AccessReview

CMOS MEMS Fabrication Technologies and Devices

by Hongwei Qu

Micromachines 2016, 7(1), 14; https://doi.org/10.3390/mi7010014 - 21 Jan 2016

Cited by 100 | Viewed by 21244

Abstract

This paper reviews CMOS (complementary metal-oxide-semiconductor) MEMS (micro-electro-mechanical systems) fabrication technologies and enabled micro devices of various sensors and actuators. The technologies are classified based on the sequence of the fabrication of CMOS circuitry and MEMS elements, while SOI (silicon-on-insulator) CMOS MEMS are [...] Read more.

This paper reviews CMOS (complementary metal-oxide-semiconductor) MEMS (micro-electro-mechanical systems) fabrication technologies and enabled micro devices of various sensors and actuators. The technologies are classified based on the sequence of the fabrication of CMOS circuitry and MEMS elements, while SOI (silicon-on-insulator) CMOS MEMS are introduced separately. Introduction of associated devices follows the description of the respective CMOS MEMS technologies. Due to the vast array of CMOS MEMS devices, this review focuses only on the most typical MEMS sensors and actuators including pressure sensors, inertial sensors, frequency reference devices and actuators utilizing different physics effects and the fabrication processes introduced. Moreover, the incorporation of MEMS and CMOS is limited to monolithic integration, meaning wafer-bonding-based stacking and other integration approaches, despite their advantages, are excluded from the discussion. Both competitive industrial products and state-of-the-art research results on CMOS MEMS are covered. Full article

(This article belongs to the Special Issue CMOS-MEMS Sensors and Devices)

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2173 KiB

Open AccessReview

Nanoelectromechanical Switches for Low-Power Digital Computing

by Alexis Peschot, Chuang Qian and Tsu-Jae King Liu

Micromachines 2015, 6(8), 1046-1065; https://doi.org/10.3390/mi6081046 - 10 Aug 2015

Cited by 66 | Viewed by 11936

Abstract

The need for more energy-efficient solid-state switches beyond complementary metal-oxide-semiconductor (CMOS) transistors has become a major concern as the power consumption of electronic integrated circuits (ICs) steadily increases with technology scaling. Nano-Electro-Mechanical (NEM) relays control current flow by nanometer-scale motion to make or [...] Read more.

The need for more energy-efficient solid-state switches beyond complementary metal-oxide-semiconductor (CMOS) transistors has become a major concern as the power consumption of electronic integrated circuits (ICs) steadily increases with technology scaling. Nano-Electro-Mechanical (NEM) relays control current flow by nanometer-scale motion to make or break physical contact between electrodes, and offer advantages over transistors for low-power digital logic applications: virtually zero leakage current for negligible static power consumption; the ability to operate with very small voltage signals for low dynamic power consumption; and robustness against harsh environments such as extreme temperatures. Therefore, NEM logic switches (relays) have been investigated by several research groups during the past decade. Circuit simulations calibrated to experimental data indicate that scaled relay technology can overcome the energy-efficiency limit of CMOS technology. This paper reviews recent progress toward this goal, providing an overview of the different relay designs and experimental results achieved by various research groups, as well as of relay-based IC design principles. Remaining challenges for realizing the promise of nano-mechanical computing, and ongoing efforts to address these, are discussed. Full article

(This article belongs to the Special Issue CMOS-MEMS Sensors and Devices)

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