Design and fabrication of SU-8 CMUT arrays through grayscale lithography

Ge, Chang Chun; Cretu, Edmond

doi:10.1016/j.sna.2018.08.006

Cited by 9 publications

(2 citation statements)

References 20 publications

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“…As the fabrication process is relatively uniform, it is possible to integrate arrays with a high element density, small element size, MUT arrays, and external circuits in a chip for packaging. Currently, capacitive micromachined ultrasonic transducers (CMUTs) and piezoelectric micromachined ultrasonic transducers are being studied by an increasing number of research groups [10,11,12,13]. The deflection of the flexural mode of the piezoelectric micromachined ultrasonic transducer (PMUT) mainly depends on the lateral strain of its piezoelectric film while an AC voltage is applied [14,15,16].…”

Section: Introductionmentioning

confidence: 99%

Piezoelectric Micromachined Ultrasonic Transducers with a Cost-Effective Bottom-Up Fabrication Scheme for Millimeter-Scale Range Finding

Feng

Liu

2019

Sensors

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This study proposes a novel piezoelectric micromachined ultrasonic transducer (PMUT), fabricated on a metal foil. Using a bottom-up, cost-effective micromachining technique, the PMUTs made of electrodes, a piezoelectric film, or electrode-sandwiched structures with versatile patterns were implemented on a large-area foil thinner rather than regular paper. The proposed microfabrication facilitated the PMUT to be able to generate ultrasonic waves with fundamental and harmonic resonances. The fourth-order resonances of the fabricated PMUT functionally operated at an ultrasonic spectrum of approximately 30 kHz as an ultrasonic emitter. The developed PMUT was paired with a microelectromechanical system (MEMS) microphone module for range-finding applications in the range of several tens of millimeters. A signal-processing scheme was developed to extract the representative pattern from the acquired signals that were emitted and received. The pattern enabled finding the distance between the PMUT and the microphone using time-of-flight and strength-variation technology. The developed PMUT-microphone pair demonstrated its range-finding performance, displaying an error of less than 0.7% using the time-of-flight method.

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Section: Introductionmentioning

confidence: 99%

Piezoelectric Micromachined Ultrasonic Transducers with a Cost-Effective Bottom-Up Fabrication Scheme for Millimeter-Scale Range Finding

Feng

Liu

2019

Sensors

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“…When the SU-8 surface micromachining in Figure 1 is used to fabricate out-of-plane polymeric electrostatic MEMS structures, the use of sacrificial layers often generates an increased process complexity. To address this problem, the authors have previously developed and experimentally validated fabrication flows for out-of-plane SU-8 MEMS structures, based on grayscale lithography techniques, on both rigid substrates and flexible ones [20][21][22]. The developed methods do not use any sacrificial layers during the fabrication, removing four steps from traditional SU-8 surface micromachining for out-of-plane MEMS structures.…”

Section: Introductionmentioning

confidence: 99%

A Simple and Robust Fabrication Process for SU-8 In-Plane MEMS Structures

Cretu

2020

Micromachines

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In this paper, a simple fabrication process for SU-8 in-plane micro electro-mechanical systems (MEMS) structures, called "border-bulk micromachining", is introduced. It aims to enhance the potential of SU-8 MEMS structures for applications such as low-cost/disposable microsystems and wearable MEMS. The fabrication process is robust and uses only four processing steps to fabricate SU-8 in-plane MEMS structures, simplifying the fabrication flow in comparison with other reported attempts. The whole fabrication process has been implemented on copper-polyimide composites. A new processing method enables the direct, laser-based micromachining of polyimide in a practical way, bringing in extra processing safety and simplicity. After forming the polymeric in-plane MEMS structures through SU-8 lithography, a copper wet etching masked by the SU-8 structure layers is carried out. After the wet etching, fabricated in-plane MEMS structures are suspended within an open window on the substrate, similar to the final status of in-plane MEMS devices made from industrial silicon micromachining methods (such as SOIMUMPS). The last step of the fabrication flow is a magnetron sputtering of aluminum. The border-bulk micromachining process has been experimentally evaluated through the fabrication and the characterization of simple in-plane electrically actuated MEMS test structures. The characterization results of these simple test structures have verified the following process qualities: controllability, reproducibility, predictability and general robustness.Micromachines 2020, 11, 317 2 of 16 process to form microstructures, with its simplicity leading to a low fabrication cost, while SU-8 has better mechanical properties and chemical stability, in comparison with other photoresists [3,4]. For the fabrication of both out-of-plane and in-plane SU-8 electrostatic MEMS structures, the most commonly used fabrication flow is layer-by-layer surface micromachining [5][6][7][8][9][10][11][12]. The generic schematic of a layer-by-layer SU-8 micromachining process is illustrated in Figure 1.Micromachines 2020, 11, x 2 of 17The fabrication cost, speed and process simplicity are vital to polymeric MEMS structures and their applications. This explains why SU-8 series negative photoresist has been advantageous and popular as structural layers for polymeric MEMS devices. Such processes require only a single lithography process to form microstructures, with its simplicity leading to a low fabrication cost, while SU-8 has better mechanical properties and chemical stability, in comparison with other photoresists [3,4]. For the fabrication of both out-of-plane and in-plane SU-8 electrostatic MEMS structures, the most commonly used fabrication flow is layer-by-layer surface micromachining [5][6][7][8][9][10][11][12]. The generic schematic of a layer-by-layer SU-8 micromachining process is illustrated in Figure 1.

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Bionic MEMS for Touching and Hearing Sensations: Recent Progress, Challenges, and Solutions

Cretu

2022

J Bionic Eng

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Design and fabrication of SU-8 CMUT arrays through grayscale lithography

Cited by 9 publications

References 20 publications

Piezoelectric Micromachined Ultrasonic Transducers with a Cost-Effective Bottom-Up Fabrication Scheme for Millimeter-Scale Range Finding

Piezoelectric Micromachined Ultrasonic Transducers with a Cost-Effective Bottom-Up Fabrication Scheme for Millimeter-Scale Range Finding

A Simple and Robust Fabrication Process for SU-8 In-Plane MEMS Structures

Bionic MEMS for Touching and Hearing Sensations: Recent Progress, Challenges, and Solutions

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