Surface-Micromachined CMUT Using Low-Temperature Deposited Silicon Carbide Membranes for Above-IC Integration

Zhang, Qing; Cicek, Paul-Vahé; Allidina, Karim; Nabki, Frédéric; El-Gamal, M.N.

doi:10.1109/jmems.2013.2281304

Cited by 35 publications

(9 citation statements)

References 32 publications

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“…In addition, the difference between the measured resonant frequency and the theoretical resonant frequency is only about 1%. This value is smaller than that of the CMUTs achieved in [ 23 ], which has a difference of about 6% between these two values. Thirdly, the electrical insertion loss ( S 21 ) is about −24 dB, which is better than that of −42 dB presented in [ 24 ].…”

Section: Device Characterizationscontrasting

confidence: 56%

Fabrication and Characterization of Capacitive Micromachined Ultrasonic Transducers with Low-Temperature Wafer Direct Bonding

Wang

Jin

2016

Micromachines

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This paper presents a fabrication method of capacitive micromachined ultrasonic transducers (CMUTs) by wafer direct bonding, which utilizes both the wet chemical and O2 plasma activation processes to decrease the bonding temperature to 400 °C. Two key surface properties, the contact angle and surface roughness, are studied in relation to the activation processes, respectively. By optimizing the surface activation parameters, a surface roughness of 0.274 nm and a contact angle of 0° are achieved. The infrared images and static deflection of devices are assessed to prove the good bonding effect. CMUTs having silicon membranes with a radius of 60 μm and a thickness of 2 μm are fabricated. Device properties have been characterized by electrical and acoustic measurements to verify their functionality and thus to validate this low-temperature process. A resonant frequency of 2.06 MHz is obtained by the frequency response measurements. The electrical insertion loss and acoustic signal have been evaluated. This study demonstrates that the CMUT devices can be fabricated by low-temperature wafer direct bonding, which makes it possible to integrate them directly on top of integrated circuit (IC) substrates.

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Section: Device Characterizationscontrasting

confidence: 56%

Fabrication and Characterization of Capacitive Micromachined Ultrasonic Transducers with Low-Temperature Wafer Direct Bonding

Wang

Jin

2016

Micromachines

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“…A proposed third readout mechanism was introduced in [13], where the structure's head movement is measured capacitively. Capacitive MEMS sensors and actuators prove efficient in many sensing applications such as inertial, ultrasonic, and magnetic sensors [14][15][16]. Additionally, capacitive sensors do not exhibit Johnson and 1/ f noise, which are associated with resistive microbolometers [2].…”

Section: Introductionmentioning

confidence: 99%

Dual-Level Capacitive Micromachined Uncooled Thermal Detector

Tawfik

Allidina²,

Nabki

et al. 2019

Sensors

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This paper presents a novel dual-level capacitive microcantilever-based thermal detector that is implemented in the commercial surface micromachined PolyMUMPs technology. The proposed design is implemented side-by-side with four different single-level designs to enable a design-to-design performance comparison. The dual-level design exhibits a rate of capacitance change per degree Celsius that is over three times higher than that of the single-level designs and has a base capacitance that is more than twice as large. These improvements are achieved because the dual-level architecture allows a 100% electrode-to-detector area, while single-level designs are shown to suffer from an inherent trade-off between sensitivity and base capacitance. In single-level designs, either the number of the bimorph beams or the capacitance electrode can be increased for a given sensor area. The former is needed for a longer effective length of the bimorph for higher thermomechanical sensitivity (i.e., larger tilting angels per degree Celsius), while the latter is desired to relax the read-out integrated-circuits requirements. This thermomechanical response-to-initial capacitance trade-off is mitigated by the dual-level design, which dedicates one structural layer to serve as the upper electrode of the detector, while the other layer contains as many bimorph beams as desired, independently of the former’s area.

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“…MEMS sensors or actuators are either micromachined on top or as part of silicon substrates which are typically referred to as surface (e.g., [ 2 ]) and bulk micromachining (e.g., [ 3 ]), respectively. The former allows a monolithic implementation of MEMS sensors and actuators on top of complementary metal oxide semiconductor (CMOS) substrates in which the read-out and driving integrated circuits (ICs) are implemented [ 4 ]. This is desired for saving system footprint in a large number of applications, such as portable devices.…”

Section: Introductionmentioning

confidence: 99%

Hard-Baked Photoresist as a Sacrificial Layer for Sub-180 °C Surface Micromachining Processes

Tawfik

Elsayed²,

Nabki

et al. 2018

Micromachines

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This letter proposes a method for utilizing a positive photoresist, Shipley 1805, as a sacrificial layer for sub-180 °C fabrication process flows. In the proposed process, the sacrificial layer is etched at the end to release the structures using a relatively fast wet-etching technique employing resist remover and a critical point dryer (CPD). This technique allows high etching selectivity over a large number of materials, including silicon-based structural materials such as silicon-carbide, metals such as titanium and aluminum, and cured polymers. This selectivity, as well as the low processing thermal budget, introduces more flexibility in material selection for monolithic integration above complementary metal oxide semiconductor (CMOS) as well as flexible substrates.

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Surface-Micromachined CMUT Using Low-Temperature Deposited Silicon Carbide Membranes for Above-IC Integration

Cited by 35 publications

References 32 publications

Fabrication and Characterization of Capacitive Micromachined Ultrasonic Transducers with Low-Temperature Wafer Direct Bonding

Fabrication and Characterization of Capacitive Micromachined Ultrasonic Transducers with Low-Temperature Wafer Direct Bonding

Dual-Level Capacitive Micromachined Uncooled Thermal Detector

Hard-Baked Photoresist as a Sacrificial Layer for Sub-180 °C Surface Micromachining Processes

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