An Improved CMUT Structure Enabling Release and Collapse of the Plate in the Same Tx/Rx Cycle for Dual-Frequency Acoustic Angiography

Mahmud, Marzana Mantasha; Wu, Xun; Sanders, Jean L.; Biliroglu, Ali Onder; Adelegan, Oluwafemi J.; Newsome, Isabel G.; Yamaner, F. Yalcın; Dayton, Paul A.; Oralkan, Ömer

doi:10.1109/tuffc.2020.3001221

Cited by 17 publications

(12 citation statements)

References 44 publications

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“…Similar to other works 5 , 19 , 23 , we performed calculations accounting for diffraction and attenuation to determine the pressure on the transducer surface. Additional information regarding these calculations is available in Suppl.…”

Section: Resultsmentioning

confidence: 99%

“…Additional information regarding these calculations is available in Suppl. 3 5 , 19 , 21 , 23 , 33 – 35 . For each rectangular CMUT architecture, the surface pressure transmitted per AC volt applied (transmit efficiency) is given as a function of bias voltage in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…This approach further addresses charging by reducing the opportunities for charge to become trapped within the dielectric post, albeit at the expense of a reduced active area within each CMUT cell. This architectural modification has been incorporated into an ensemble of circular membranes by Mahmud et al 19 using anodic bonding with a borosilicate glass substrate, and hexagonal membranes by Machida et al 20 using a sacrificial release process.…”

Section: Introductionmentioning

confidence: 99%

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Outperforming piezoelectric ultrasonics with high-reliability single-membrane CMUT array elements

et al. 2022

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It has long been hypothesized that capacitive micromachined ultrasound transducers (CMUTs) could potentially outperform piezoelectric technologies. However, challenges with dielectric charging, operational hysteresis, and transmit sensitivity have stood as obstacles to these performance outcomes. In this paper, we introduce key architectural features to enable high-reliability CMUTs with enhanced performance. Typically, a CMUT element in an array is designed with an ensemble of smaller membranes oscillating together to transmit or detect ultrasound waves. However, this approach can lead to unreliable behavior and suboptimal transmit performance if these smaller membranes oscillate out of phase or collapse at different voltages. In this work, we designed CMUT array elements composed of a single long rectangular membrane, with the aim of improving the output pressure and electromechanical efficiency. We compare the performance of three different modifications of this architecture: traditional contiguous dielectric, isolated isolation post (IIP), and insulated electrode-post (EP) CMUTs. EPs were designed to improve performance while also imparting robustness to charging and minimization of hysteresis. To fabricate these devices, a wafer-bonding process was developed with near-100% bonding yield. EP CMUT elements achieved electromechanical efficiency values as high as 0.95, higher than values reported with either piezoelectric transducers or previous CMUT architectures. Moreover, all investigated CMUT architectures exhibited transmit efficiency 2–3 times greater than published CMUT or piezoelectric transducer elements in the 1.5–2.0 MHz range. The EP and IIP CMUTs demonstrated considerable charging robustness, demonstrating minimal charging over 500,000 collapse-snap-back actuation cycles while also mitigating hysteresis. Our proposed approach offers significant promise for future ultrasonic applications.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Outperforming piezoelectric ultrasonics with high-reliability single-membrane CMUT array elements

et al. 2022

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“…Although microbubble-based ultrasound imaging usually requires the use of low frequencies ranging from 1 to 10 MHz, in recent years, many researchers have explored high-frequency applications (>10 MHz). High-frequency imaging using contrast agents is advantageous as this imaging approach can be used to solve the problem of increased attenuation following improved echogenicity and yields more optimized resolution than low-frequency imaging [21] , [22] , [23] , [24] , [25] . Furthermore, a sharp high-frequency ultrasound beam can deliver genes and drugs to local regions with high precision.…”

Section: Introductionmentioning

confidence: 99%

Collapse pressure measurement of single hollow glass microsphere using single-beam acoustic tweezer

Yoo

Kim

Lim

et al. 2022

Ultrasonics Sonochemistry

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“…As an alternative to traditional piezoelectric type transducer, CMUT has the advantages of better impedance matching with wider bandwidth, larger acceptance angle, flexibility in fabricating large and complex array configurations and better integration with CMOS circuits [14,15,1]. It can be applied in many areas like gas sensing [11], anemometer [13], sonar system [4], biological tissue imaging [9,7], neural stimulating [10] and fingerprint imaging system [2].…”

Section: Introductionmentioning

confidence: 99%

Fabrication of CMUTs using sacrificial release process with ashing assisted polysilicon release

Kin

Liu

et al. 2022

International Conference on Biomedical and Intelligent Systems (IC-BIS 2022)

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Capacitive Micromachined Ultrasonic Transducer (CMUT) is a type of ultrasonic transducer that can be applied in many fields like chemical and mechanical sensing, physical imaging, and bio-imaging. Sacrificial layer release is one of the fabrication methods and cavity releasing is the key part of this method. The stress of the sacrificial material is one of the causes making membranes break in this procedure. The previous studies had a phospho-silicide-glass (PSG) layer deposited between polysilicon sacrificial layer and silicon nitride membrane with LPCVD partially solved the problem. However, its processing temperature is relatively high, which makes it not compatible with CMOS integrated circuits (ICs). This work fabricated CMUTs in the sacrificial layer release process, with polysilicon as the main sacrificial layer. Utilizing chemical reaction of polysilicon in ashing process, a thin oxide was formed between the sacrificial layer and membrane while removing the remaining photoresist with ashing. The result showed that it could also help produce large membranes with a lower processing temperature, which can be more compatible with CMOS ICs. After fabrication, the impedance of an element with 100 μm diameter cells was measured to be several hundred ohms in air with 30 V bias voltage and the resonance frequency was 4.7 MHz.

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An Improved CMUT Structure Enabling Release and Collapse of the Plate in the Same Tx/Rx Cycle for Dual-Frequency Acoustic Angiography

Cited by 17 publications

References 44 publications

Outperforming piezoelectric ultrasonics with high-reliability single-membrane CMUT array elements

Outperforming piezoelectric ultrasonics with high-reliability single-membrane CMUT array elements

Collapse pressure measurement of single hollow glass microsphere using single-beam acoustic tweezer

Fabrication of CMUTs using sacrificial release process with ashing assisted polysilicon release

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