Piezoelectric Micromachined Ultrasound Transducers (pMUTs)

Slides:



Advertisements
Similar presentations
MICROELECTROMECHANICAL SYSTEMS ( MEMS )
Advertisements

Bi-laminar Multilayer Benders or Bimorphs Prepared By: Brad Crook ECE 5320 Mechatronics Assignment #1.
Chapter 9 Capacitors.
Foundations of Medical Ultrasonic Imaging
2005 년 1 학기 논문세미나 Fabrication of Sonic Sensors Using PZT Thin Film on Si Diaphragm and Cantilever S. Murakami 1, K. Inoue 1, Y. Suzuki 1, S. Takamatst.
Design and Simulation of a MEMS Piezoelectric Micropump Alarbi Elhashmi, Salah Al-Zghoul, Advisor: Prof. Xingguo Xiong Department of Biomedical Engineering,
Lecture 21 QCM and Ellipsometry
Piezoelectricity Medical Physics Notes: Ultrasound.
Volume I Companion Presentation Frank R. Miele Pegasus Lectures, Inc.
MEMS Gyroscope with Electrostatic Comb Actuation and Differential Capacitance Sensing Haifeng Dong, Zheng Yao, Advisor: Xingguo Xiong Department of Electrical.
ECE/ChE 4752: Microelectronics Processing Laboratory
Variable Capacitance Transducers The Capacitance of a two plate capacitor is given by A – Overlapping Area x – Gap width k – Dielectric constant Permitivity.
INTEGRATED CIRCUITS Dr. Esam Yosry Lec. #6.
Figure 7 Design and Simulation of a MEMS Thermal Actuated Micropump Shiang-Yu Lin, Huaning Zhao, Advisor Prof. Xingguo Xiong Department of Biomedical Engineering,
Chang Liu MASS UIUC Micromachined Piezoelectric Devices Chang Liu Micro Actuators, Sensors, Systems Group University of Illinois at Urbana-Champaign.
Ultrasound Imaging Atam Dhawan.
Applications: Angular Rate Sensors (cont’d)
Processing and Characterization of Piezoelectric Materials into MicroElectroMechanical Systems Weiqiang Wang.
ELEKTRONIKOS ĮTAISAI 2009 VGTU EF 1 Acoustic Waves Acoustic wave: A longitudinal wave that (a) consists of a sequence.
K L University 1 By G.SUNITA DEPARTMENT OF PHYSICS.
1. NameRoll No Athar Baig10EL40 Muhammad Faheem10EL38 Tassawar Javed10EL44 Tayyaba Abbas10EL09 Sadia Imtiaz10EL37 2.
Ultrasonic Testing This technique is used for the detection of internal surface (particularly distant surface) defects in sound conducting.
GENERATING AND DETECTING OF ULTRASOUND
MEMs Fabrication Alek Mintz 22 April 2015 Abstract
RF MEMS devices Prof. Dr. Wajiha Shah. OUTLINE  Use of RF MEMS devices in wireless and satellite communication system. 1. MEMS variable capacitor (tuning.
MEMS Fabrication and Applications Brought to you by: Jack Link & Aaron Schiller Date delivered on: Friday the third of May, 2013 ABSTRACT: Taking a brief.
Surface micromachining
Bulk Micromachining of Silicon for MEMS
Smart Materials in System Sensing and Control Dr. M. Sunar Mechanical Engineering Department King Fahd University of Petroleum & Minerals.
ES 176/276 – Section # 2 – 09/19/2011 Brief Overview from Section #1 MEMS = MicroElectroMechanical Systems Micron-scale devices which transduce an environmental.
Slide # 1 Velocity sensor Specifications for electromagnetic velocity sensor Velocity sensors can utilize the same principles of displacement sensor, and.
Some Applications of Ferroelectric Ceramics 1.Capacitors 2. Ferroelectric Thin Films 2.1 Ferroelectric Memories 2.2 Electro-Optic Applications Thin.
Piezoelectric Equations and Constants
Figure 17.1: Evolution from MEMS to NEMS to molecular structures. Nanostructures may have a total mass of only a few femtograms. In the nanomechanical.
Sarah Gillies Ultrasound Sarah Gillies
1 M. Chitteboyina, D. Butler and Z. Celik-Butler, Nanotechnology Research and Teaching Facility University of Texas at Arlington
Slide # Basic principles The effect is explained by the displacement of ions in crystals that have a nonsymmetrical unit cell When the crystal is compressed,
Ultrasound Physics Reflections & Attenuation ‘97.
EE 4BD4 Lecture 16 Piezoelectric Transducers and Application 1.
Surface Acoustics Wave Sensors. Outline Introduction Piezoelectricity effect Fabrication of acoustic waves devices Wave propagation modes Bulk Wave sensor.
Piezoelectric Effect  Sound waves striking a PZ material produce an electrical signal  Can be used to detect sound (and echoes)!
Ultrasound Learning Objectives: Describe the properties of ultrasound;
Basic theory of sound, piezomaterials and vibrations.
 Ultrasound waves are longitudinal with high frequencies ( ≈ > 20,000 Hz, though medical Ultrasound is between 1 to 15 MHz.)  When an ultrasound reaches.
(Chapters 29 & 30; good to refresh 20 & 21, too)
Study & Design of Micro-strip Patch Antenna
Chapter 9 CAPACITOR.
Sound in medicine Lect.10.
Objective Functions for Optimizing Resonant Mass Sensor Performance
Reflections & Attenuation
Prof. Sajid Naeem (DOES – PC)
Ultrasound.
Single-element transducers properties
Variable Capacitance Transducers
(Pressure measurement under harsh environments)
Ultrasound.
Introduction What is a transducer? A device which converts energy in one form to another. Transducer Active Passive Generates its own electrical voltage.
Unit-2.
Characterisation of the back-etched stack
Binary Resonant Wings Joe Evans, Naomi Montross, Gerald Salazar
Process flow part 2 Develop a basic-level process flow for creating a simple MEMS device State and explain the principles involved in attaining good mask.
Working Principle and Structural Design Conclusions and Further Work
Memscap - A publicly traded MEMS company
ECE699 – 004 Sensor Device Technology
MicroElectroMechanical Systems
(2) Incorporation of IC Technology Example 18: Integration of Air-Gap-Capacitor Pressure Sensor and Digital readout (I) Structure It consists of a top.
SILICON MICROMACHINING
BONDING The construction of any complicated mechanical device requires not only the machining of individual components but also the assembly of components.
Binary Resonant Wings Joe Evans, Naomi Montross, Gerald Salazar
Sound Waves and Ultrasound
Presentation transcript:

Piezoelectric Micromachined Ultrasound Transducers (pMUTs) Muhammet İpekçi 505612003 Electrical Electronics Engineering

Piezoelectric effect The piezoelectric effect describes the ability of materials to develop electric displacement as a result of an applied mechanical stress The crystal expands and contracts with a returning sound wave causing an electrical voltage to be emitted Returning sound wave are converted into electrical signals

Inverse Piezoelectric Effect The property of certain crystals to expand or strain when positive or negative electrical current is applied Voltage applied to opposite sides of the crystal cause it to expand; polarity is reversed (AC current) causing the crystal to strain Constant change from expansion to strain, strain to expansion, results in mechanical waves (sound) being produced Thus, the electrical signal is converted into a sound wave

Piezoelectric sound theory Piezoelectric ceramic buzzer simple structure in which piezoceramic element is sticked to vibration plate When alternating voltage is applied to piezoceramic element, the element expands or shrinks diametrically This characteristic is utilized to make vibration plated bend to generate sounds.

Ultrasound Ultrasound is an oscillating sound pressure wave with a frequency greater than the upper limit of the human hearing range. Human hearing range 20-20.000 Hertz Ultrasound devices frequencies from 20 kHz up to several gigahertz

Ultrasound Principle of an active sonar Ultrasound image of a fetus

What is pMUT ? Micromachined ultrasound transducers have allowed feasibility for mobile applications of ultrasound devices imaging range-finding or other through a decrease in volume, weight, and power consumption. Technological developments for integrated circuit fabrication have allowed further miniaturization and fabrication of 2D and 3D arrays.

pMUTs Structure Among the available ferroelectric materials PZT lead zirconate titanate, Pb(ZrxTi1−x)O3 is the most popular due to; its superior dielectric constant, piezoelectric constants, thermal stability.

pMUTs Structure Piezoceramic thick films based on lead zirconate titanate (PZT) are of great interest for cost-effective fabrication of integrated sensors and actuators for MEMS (Micro Electro Mechanical Systems) and high frequency ultrasonic transducers.

pMUTs Design A detailed design of pMUT showing various layers on top of the Si membrane.

pMUTs Design Each element consists of a silicon membrane, an active PZT film The SiO2 layer, on top of the silicon membrane Ti/Pt electrode to the wafer surface at the bottom Ti/Pt layer is added on top of the SiO2 as a bottom electrode PZT, in optimized multiple layers, is then spin-coated on the bottom electrode Finally, a top gold electrode having a predetermined pattern, is deposited on the PZT film and the film poled in the thickness direction

Fabrication of pMUTs pMUT fabrication involves building a silicon membrane with electroded PZT layers on top Silicon wafers (p-type 1 0 0, 395–405 m) were wet oxidized at 1050 ◦C to grow a 500 nm thick oxide The oxide layer was removed from one side of the wafer using a buffered oxide etch (BOE). Borosilicate glass that forms on the surface 1125 ◦C for 1 h. Standard photolithography techniques were used to create an oxide mask on the backside of the wafer The wafers were then etched with the anisotropic silicon etchant ethylenediamine pyrocatechol (EDP) Schematic flow chart of silicon membrane fabrication.

Fabrication of pMUTs PZT thin films are then deposited via spin coating of the PZT sol. Top electrodes were deposited by sputtering 10 nm of TiW and 200 nm of Au. These films were then patterned using standard photolithography techniques to create a top electrode with leads off the membrane The PZT film was also patterned to expose the bottom electrode using a HCl:HF:H2O etchant. Schematic flow chart for the fabrication of the PZT-driven membrane from a micromachined substrate.

Fabrication of pMUTs Cross-sectional secondary electron beam microscopy picture of 2-μm-thick PZT 52/48 thin film The micromachined bridge of a suspended membrane with the etched Pt/PZT/Pt sandwich

Performance of pMUTs Schematic of pMUT flexure with associated representations of input sine wave signal, ferroelectric hysteresis loop (indicating domain switching), and mechanical displacement as a function of input voltage. Points A and A’ refer to 0 V applied, points B and D refer to the coercive voltage, and points C and E refer to maximum applied voltage.

Performance parameters The frequency at which the transducer is the most efficient as a transmitter of sound is also the frequency at which it is most sensitive as a receiver of sound. This frequency is called the natural or resonant frequency of the transducer. The range of frequencies in the emitted ultrasound wave is called the bandwidth and is defined to be the full width of the frequency distribution at half maximum (FWHM).

Performance parameters The resonance frequency of the device is directly determined by analyzing its time response under free vibration after a pulse excitation has been applied, while the bandwidth is estimated from the frequency response of the normal velocity of a central point on the membrane. The resonance frequency of the transducer is governed by the thickness of the PZT. The fundamental resonance mode exists when the thickness of the PZT is equal to half the wavelength.

Performance parameters Membrane width is an important design parameter as it strongly affects the membrane stiffness and, hence, the device resonance frequency, acoustic impedance, bandwidth, and coupling coefficient

Performance parameters

Performance parameters

Performance parameters thicker crystal – lower frequency thinner crystal – higher frequency crystal thickness = ½  for the frequency higher propagation speed – higher frequency slower propagation speed – lower frequency Typical propagation speeds of 4-6 mm/s Frequency (MHz) = crystal’s propagation speed (mm/s) 2 x thickness (mm)

5x5 2D pMUT array in air Surface displacement mode shapes of a 200μm pMUT element in air at showing different modes of operation.

5x5 2D pMUT array in Water Surface displacement mode shapes of a 200μm pMUT element in water at showing different modes of operation.

Applications of pMUTs Medical applications For medical imaging purposes, the ultrasound transducers would be included on a probe tip. A device would be required to have a high frequency to insure clear images of such subject matter as veins and small tumors.

Applications of pMUTs Criminal applications A second possible use for the device is for biometric fingerprint identification. A micromachined ultrasound transducer could supply a small, portable, and highly accurate fingerprint scanner that can not only image dermal, but also subdermal layers of the finger

References F . Akasheh, T. Myers, J. D. Fraser, S. Bose, and A. Bandyopadhyay, “Development of piezoelectric micromachined ultrasonic transducers,” Sens. Actuators A, vol. 111, pp. 275–287, 2004. P. Muralt, N. Ledermann, J. Baborowski, A. Barzegar, S. Gentil, B.Belgacem, S. Petitgrand, A. Bosseboeuf, and N. Seter, “Piezoelectric micromachined ultrasonic transducers based on PZT thin films” David E. Dausch, Senior Member, IEEE, John B. Castellucci, Derrick R. Chou, Student Member, IEEE, and Olaf T. von Ramm “Theory and Operation of 2-D Array Piezoelectric Micromachined Ultrasound Transducers“ Piezoelectric Micromachined Ultrasound Transducers for Medical Imaging by Derrick R. Chou

Comments and Questions?