Search query: PMUT

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abstract: This paper presents an analog front end transceiver for an ultrasound imaging system based on a high voltage (HV) transmitter, a low noise front end amplifier (RX) and a complementary metal oxide semiconductor, aluminum nitride, piezoelectric micromachined ultrasonic transducer (CMOS AlN PMUT) The system was designed using the 0.13 mm Silterra CMOS process and the MEMS on CMOS platform, which allowed for the implementation of an AlN PMUT on top of the CMOS integrated circuit. The HV transmitter drives a column of six 80 mm square PMUTs excited with 32 V in order to generate enough acoustic pressure at a 2.1 mm axial distance. On the reception side, another six 80 mm square PMUT columns convert the received echo into an electric charge that is amplified by the receiver front end amplifier. A comparative analysis between a voltage front end amplifier (VA) based on capacitive integration and a charge sensitive front end amplifier (CSA) is presented. Electrical and acoustic experiments successfully demonstrated the functionality of the designed low power analog front end circuitry, which outperformed a state of the art front end application specific integrated circuit (ASIC) in terms of power consumption, noise performance, and area.
author_names: Ivan Zamora

Eyglis Ledesma

Arantxa Uranga

Nuria Barniol
title: Miniaturized 0.13 mm CMOS Front End Analog for AlN PMUT Arrays
venue: Sensors
year: 2020

abstract: This article presents a fully integrated ultrasound system based on a single piezoelectric micromachined ultrasonic transducer (PMUT) monolithically fabricated with a <inline formula> <tex math notation="LaTeX"$0.13~\mu \text{m} /tex math>/inline formula> complementary metal oxide semiconductor (CMOS) process analog front end circuitry. The PMUT consists of an aluminum nitride, AlN, squared device with <inline formula> <tex math notation="LaTeX"$80~\mu \text{m} /tex math>/inline formula> side that resonates at 2.4 MHz in liquid environment. The monolithic integration of the PMUT with the CMOS circuitry allows a reduction of the parasitic capacitance, a reduction of the electronic noise contribution and a clear improvement in the Signal to Noise ratio (SNR 27 dB better) compared to a non integrated equivalent system. A pulse echo experiment with the single PMUT on CMOS for transmitting and sensing simultaneously is demonstrated, ensuring a 17.3 dB SNR, higher than the minimal necessary for accurate fingerprint images, paving the way towards a pixel sized imaging system with no need of multiple simultaneous PMUTs transmitters. Consuming only 0.3 mW and getting an input referred noise of 3.26 mPa/<inline formula> <tex math notation="LaTeX"\surd /tex math>/inline formula>Hz at 2.4 MHz, the proposed pulse echo system achieves a competitive noise efficient factor in comparison with the state of the art.
author_names: Ivan Zamora

Eyglis Ledesma

Arantxa Uranga

Nuria Barniol
title: Monolithic Single PMUT on CMOS Ultrasound System With +17 dB SNR for Imaging Applications
venue: IEEE Access
year: 2020

abstract: Microelectromechanical system (MEMS) based mass sensors are proposed as potential candidates for highly sensitive chemical and gas detection applications owing to their miniaturized structure, low power consumption, and ease of integration with readout circuits. This paper presents a new approach in developing micromachined mass sensors based on capacitive and piezoelectric transducer configurations for use in low concentration level gas detection in a complex environment. These micromachined sensors operate based on a shift in their center resonant frequencies. This shift is caused by a change in the sensor's effective mass when exposed to the target gas molecules, which is then correlated to the gas concentration level. In this work, capacitive and piezoelectric based micromachined sensors are investigated and their principle of operation, device structures and configurations, critical design parameters and their candidate fabrication techniques are discussed in detail.
author_names: Haleh Nazemi

Jenitha Antony Balasingam

Siddharth Swaminathan

Kenson Ambrose

Muhammad Umair Nathani

Tara Ahmadi

Yameema Babu Lopez

Arezoo Emadi
title: Mass Sensors Based on Capacitive and Piezoelectric Micromachined Ultrasonic Transducers CMUT and PMUT
venue: Sensors
year: 2020

abstract: In this work, a waterproof tent plate piezoelectric micromachined ultrasonic transducer (PMUT) with enhanced performance as actuator and sensor in comparison with standard clamped PMUT is presented. The squared AlN PMUT has four linear holes that are sealed by the passive layer allowing to increase the movement and giving the capability to work in liquid environment. The dimension of the holes was optimized to increase the PMUT displacement at least twice in relation with the regular clamped device. The acoustic performance of the PMUT was simulated in COMSOL Multiphysics and the results were experimentally verified under liquid operation. The experimental transmitting sensitivity, 3.9 kPa/V, as well as the sensor sensitivity, 13.4 V/MPa, provide a 2x factor improvement in contrast with the clamped PMUT with competitive values. Additionally, the presented tent plate PMUT provides advantages in relation with the area, cost, power consumption and imaging quality thanks to the capability to be monolithically integrated over CMOS substrates.
author_names: Eyglis Ledesma

Ivan Zamora

Arantxa Uranga

Nuria Barniol
title: Tent Plate AlN PMUT With a Piston Like Shape Under Liquid Operation
venue: IEEE Sensors Journal
year: 2020

abstract: In this paper, we present the design, fabrication, and characterization of a compact <inline formula> <tex math notation="LaTeX"$4\times 4$ /tex math>/inline formula> piezoelectric micromachined ultrasonic transducer (pMUT) array and its application to photoacoustic imaging. The uniqueness of this pMUT array is the integration of a <inline formula> <tex math notation="LaTeX"$4~\mu \text{m} /tex math>/inline formula> thick ceramic PZT, having significantly higher piezoelectric coefficient and lower stress than sol gel or sputtered PZT. The fabricated pMUT array has a small chip size of only <inline formula> <tex math notation="LaTeX"$1.8\times1.6$ /tex math>/inline formula> mm<sup>2</sup> with each pMUT element having a diameter of <inline formula> <tex math notation="LaTeX"$210~\mu \text{m} /tex math>/inline formula> The fabricated device was characterized with electrical impedance measurement and acoustic sensing test. Photoacoustic imaging has also been successfully demonstrated on an agar phantom with a pencil lead embedded using the fabricated pMUT array. [2020 0087]
author_names: Haoran Wang

Zhenfang Chen

Hao Yang

Huabei Jiang

Huikai Xie
title: A Ceramic PZT Based PMUT Array for Endoscopic Photoacoustic Imaging
venue: Journal of Microelectromechanical Systems
year: 2020

abstract: This paper presents the design and fabrication method to render a silicon on insulator (SOI) based pMUT array bendable. The proposed method can be applied to silicon based pMUT arrays with different acoustical specifications. A bendable array based on the proposed method is highly conformal to the target structure. The bendable structure is made out of several silicon islands containing a pMUT array and are connected to each other by silicon springs. The silicon springs are realized by deep reactive ion etching (DRIE) that was also used to create the pMUT membranes. The fabrication process requires one additional photomask step compared to a process that realizes only pMUTs. Since the pMUT arrays are fabricated on silicon islands with the thickness of the entire SOI wafer, therefore their performance is not compromised. As a case study, a bendable array was designed and fabricated to be wrapped around a <inline formula> <tex math notation="LaTeX"$5\times 5\times 5$ /tex math>/inline formula> mm<sup>3</sup> 3D printed cube. Therefore, each bendable array has 6 islands with a dimension of <inline formula> <tex math notation="LaTeX"$3\times 3$ /tex math>/inline formula> mm<sup>2</sup> including <inline formula> <tex math notation="LaTeX"$3\times 3$ /tex math>/inline formula> pMUT array, of which each pMUT has a diameter of 410 <inline formula> <tex math notation="LaTeX"\mu \text{m} /tex math>/inline formula> and a thickness of 6 <inline formula> <tex math notation="LaTeX"\mu \text{m} /tex math>/inline formula> with a 1 <inline formula> <tex math notation="LaTeX"\mu \text{m} /tex math>/inline formula> Lead Zirconate Titanate (PZT) layer as the piezoelectric material. The silicon springs in between each island have a spring constant of 2.3 (N/m) in their folding direction. This compliant structure enables a 90deg bending with a bending radius of 1 mm. The pMUT elements in the array resulted in a displacement response of 2.1 <inline formula> <tex math notation="LaTeX"\mu \text{m} /tex math>/inline formula>/V and a Q factor of 104 at 426 kHz, when all arrays were excited all together. [2019 0224]
author_names: Sina Sadeghpour

Bram Lips

Michael Kraft

Robert Puers
title: Bendable Piezoelectric Micromachined Ultrasound Transducer (PMUT) Arrays Based on Silicon On Insulator (SOI) Technology
venue: Journal of Microelectromechanical Systems
year: 2020

abstract: A compact single cell piezoelectric micromachined ultrasound transducer (PMUT) with dual electrodes is designed, fabricated, and used to measure the density of a fluid mixture mimicking the range of human blood density variation. The sensor's novelty lies in its compactness enabled by on device sensing and actuation due to the dual electrodes. The active material used here is thin film PZT which is protected from the fluid environment with an appropriate coating. The results obtained show a linear response of the sensor output over the density range of interest with no appreciable degradation in the signal due to immersion in a fluid. The sensitivity of the sensor is 191 Hz/Kg/m3. These single cell PMUTs are, therefore, potential candidates for fluid density monitoring in industrial or biomedical applications.
author_names: Kaustav Roy

Avinandan Mandal

Anuj Ashok

Harshvardhan Gupta

Vijayendra Shastri

Rudra Pratap
title: A Single Cell PMUT as a Bio Fluid Density Sensor
venue: 2020 IEEE International Ultrasonics Symposium (IUS)
year: 2020

abstract: This work presents a new type of piezoelectric micromachined ultrasonic transducer (PMUT) based on a bi stable MEMS membrane structure with integrated aluminum nitride (AlN) actuators. By switching the membrane between both stable ground states, large, design dependent membrane center displacements in the range of $10~\mu \text{m} can be achieved, which result in sound pressure levels of up to 96.8 dB in the ultrasonic range at frequencies between 30 and 60 kHz at a distance of 10.5 mm. This bi stable operation mode can be triggered by moderate voltage levels of up to 40 V, which is not uncommon for PMUT devices. The usage of AlN compared to the more commonly utilized lead zirconate titanates (PZT) significantly simplifies the device integration process and ensures CMOS compatibility. A comprehensive comparison with similar devices in literature shows that despite the lower piezoelectric coefficients of AlN compared to PZT, this bi stable actuation approach features exceptionally high stroke levels with a correspondingly high overall sound pressure level. [2020 0104]
author_names: Michael Schneider

M Dorfmeister

Philipp Moll

Manfred Kaltenbacher

Ulrich Schmid
title: Bi Stable Aluminum Nitride Based Piezoelectric Micromachined Ultrasonic Transducer (PMUT)
venue: Journal of Microelectromechanical Systems
year: 2020

abstract: This work presents theoretical analysis and finite element simulations of a novel piezoelectric micromachined ultrasonic transducer (pMUT) design. A pMUT with free boundary condition is introduced for the first time and compared with conventional pMUTs of fixed boundary. For the same transducer dimensions, the proposed design has more than 2.5x electromechanical coupling coefficient compared to that from traditional clamped boundary design due to increased mechanical capacitance by the free edge. The cavity underneath the disc behaves as an acoustic resonator. By matching the frequencies of mechanical and acoustical resonances, the fractional bandwidth of the free boundary pMUT has 13x more fractional bandwidth compared to that of the fixed boundary design. In addition, the internal stresses created during microfabrication are expected to be released with the free edges. These results indicate that free pMUTs have the potential for high performance ultrasonic transducer applications.
author_names: Sedat Pala

Liwei Lin
title: Piezoelectric Micromachined Ultrasonic Transducers (pMUT) with Free Boundary
venue: 2020 IEEE International Ultrasonics Symposium (IUS)
year: 2020

abstract: This paper proposed impact of geometrical dimension for circular shaped aluminum nitride (AIN) based piezoelectric micromachined ultrasonic transducer (PMUT) for achieving best operating performance. The PMUT is focusing on 25 35 MHz frequency for biomedical application. Thus, this paper investigates the minimum geometrical dimension of PMUT with limitation of CMOS compatible process by using finite element analysis (FEA) ONSCALE software. This paper proposed comparative study that focused on AlN thickness and substrate diameter for PMUT in order to determine better design for better PMUT performance. Finite element analysis (FEA) of ONSCALE software was used for numerical analysis simulation. The simulation was carried out for AlN thickness and substrate diameter for impact study on PMUT performance with CMOS limitation. The PMUT displacement performances and frequencies for different AIN thickness and substrate diameter are analyzed. Firstly, the PMUT performance is analyzed for AlN thickness when the substrate diameter and cavity height are fixed. Secondly, the PMUT performance is analyzed for substrate diameter when the AlN thickness and cavity height are fixed. In this work, for frequency 25 35 MHz, the maximum PMUT displacement is achieved at AlN thickness \mathbf{1.1} \mu\mathbf{m} substrate diameter \mathbf{22.5} \mu\mathbf{m} and cavity height \mathbf{3.0} \mu\mathbf{m} The substrate diameter has no impact for PMUT displacement when the AlN thickness and cavity height is fixed. This work provides helpful information for designing PMUT for better performance of displacement.
author_names: Muhammad Naim Haron

Mohamad Adzhar Md Zawawi

Mohamed Fauzi Packeer

Asrulnizam Bin Abd Manaf
title: Geometrical dimension impact for performance of CMOS based circular shape aluminum nitride (AlN) piezoelectric micromachined ultrasonic transducer (PMUT)
venue: 2020 4th IEEE Electron Devices Technology Manufacturing Conference (EDTM)
year: 2020