Download or read book Fabrication of Capacitive Micromachined Ultrasonic Transducers Based on Adhesive Wafer Bonding written by Zhenhao Li and published by . This book was released on 2017 with total page 107 pages. Available in PDF, EPUB and Kindle. Book excerpt: Capacitive micromachined ultrasonic transducers (CMUTs) can be used for medical imaging, non-destructive testing or medical treatment applications. It can also be used as gravimetric sensors for gas sensing or immersion bio-sensing. Although various CMUT fabrication methods have been reported, there are still many challenges to address. Conventional fabrication methods can be categorized as either surface micromachining or the wafer bonding method. These methods have design trade-offs and limitations associated with process complexity, structural parameter optimization and wafer materials selection. For example, surface micromachining approaches can suffer from complicated fabrication processes. In addition, structural parameters cannot be fully optimized due to feasibility concerns during fabrication. In contrast, the development of wafer bonding techniques enabled CMUTs to be fabricated in a straightforward way and structural parameters can be easily optimized when compared with a surface micromachining approach. However, the yield of the traditional wafer bonded CMUTs is very sensitive to contaminations and the surface quality at the bonding interface. Although the difficulties of the wafer bonding process are not always reported, they definitely exist for every researcher who wants to fabricate their own CMUTs. As a result, this dissertation work aims to develop a CMUT fabrication process with fewer fabrication constraints, low-cost and low process temperature for CMOS integration. The developed CMUT fabrication processes reported in the thesis applied photosensitive polymer adhesive for wafer bonding in order to make a process with good tolerance to contaminations and defects on the wafer surface, present a wide range of material selection at the bonding interface and require low process temperature (less than 250°C). These features can benefit CMUT fabrication with increased yield better design flexibility and lower cost. Having maximum process temperature of 250°C, the developed processes can also be CMOS compatible. Furthermore, a novel CMUT structure, which can only be achieved by the reported technique, was developed showing more than doubled ultrasound receive sensitivity when compared with conventional CMUT structures. The fabrication processes were developed systematically and the details of process development will be presented in this thesis.

Download or read book The Design Fabrication and Characterization of Capacitive Micromachined Ultrasonic Transducers for Imaging Applications written by Andrew Stephan Logan and published by . This book was released on 2010 with total page 155 pages. Available in PDF, EPUB and Kindle. Book excerpt: Capacitive micromachined ultrasonic transducers (CMUTs) have proven themselves to be excellent candidates for medical ultrasonic imaging applications. The use of semiconductor fabrication techniques facilitates the fabrication of high quality arrays of uniform cells and elements, broad acoustic bandwidth, the potential to integrate the transducers with the necessary electronics, and the opportunity to exploit the benefits of batch fabrication. In this thesis, the design, fabrication and testing of one- and two-dimensional CMUT arrays using a novel wafer bonding process whereby the membrane and the insulation layer are both silicon nitride is reported. A user-grown insulating membrane layer avoids the need for expensive SOI wafers, permits optimization of the electrode size, and allows more freedom in selecting the membrane thickness, while also enjoying the benefits of wafer bonding fabrication. Using a row-column addressing scheme for an NxN two-dimensional array permits three-dimensional imaging with a large reduction in the complexity of the array when compared to a conventional 2D array with connections to all N2 elements. Only 2N connections are required and the image acquisition rate has the potential to be greatly increased. A simplification of the device at the imaging end will facilitate the integration of a three-dimensional imaging CMUT array into either an endoscope or catheter which is the ultimate purpose of this research project. To date, many sizes of transducers which operate at different frequencies have been successfully fabricated. Initial characterization in terms of resonant frequency and, transmission and reception in immersion has been performed on most of the device types. Extensive characterization has been performed with a linear 32 element array transducer and a 32x32 element row-column transducer. Two- and three-dimensional phased array imaging has been demonstrated.

Download or read book Capacitive Micromachined Ultrasonic Transducers with Substrate embedded Springs written by Byung Chul Lee and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: After the first capacitive micromachined ultrasonic transducer (CMUT) was invented in 1994, it became one of the candidate technologies to advance the state-of-the-art of medical ultrasound imaging. Benefiting from its fabrication technique based on the semiconductor industry, CMUT technology has broadened the medical and therapeutic applications such as real-time volumetric ultrasound imaging, catheter-based forward-looking intravascular ultrasound (IVUS), photoacoustic imaging, high-intensity focused ultrasound (HIFU) and so on. In spite of many advantages, however, CMUT technology has been criticized with its relatively low transmit sensitivity (~10 kPa/V) or low average volume displacement efficiency (0.1 nm/V) as well as large drive and bias voltage requirements (in a range of a few hundreds of volts). In order to resolve these issues and open up new potential of clinical applications, this dissertation describes the design, fabrication, and system implementation of CMUTs with substrate-embedded springs, so-called post-CMUT (PCMUT). Since PCMUT structure resembles an ideal piston transducer, the improvements in performance mainly stem from the higher average displacement of the top plate for a given gap height. The overview of the first generation PCMUT is introduced and two main issues in simulation and fabrication aspects of the first generation PCMUT is discussed. To further improve the PCMUT device, a 3D finite element analysis (FEA) model of the PCMUT is demonstrated to predict the performance of the first generation PCMUT. In addition, the design guideline of the second generation PCMUT is proposed for achieving the maximum fractional bandwidth (100 %) as well as with the highest transmit sensitivity (~28 kPa/V). The second generation PCMUT is fabricated by using three combination MEMS processes: usage of two silicon-on-insulator (SOI) wafers, wafer bonding process, and wafer polishing process. The second generation PCMUT achieves high transmit sensitivity (~21 kPa/V) or large average volume displacement efficiency (1.1 nm/V) with a low bias voltage (55 V). Compared to a commercial piezoelectric transducer, the second generation PCMUT improves 2.75 times of the maximum output pressure and 5.25 times of the average volume displacement efficiency with respect to the same voltage. After fabrication and performance characterization of the second generation PCMUT, this dissertation demonstrates the feasibility of PCMUT to use it in medical imaging system by integrating PCMUT with a custom-built integrated circuit (IC). Photoacoustic imaging is also presented for one of its application examples.

Download or read book Interface Engineering of Capacitive Micromachined Ultrasonic Transducers for Medical Applications written by Der-Song Lin and published by Stanford University. This book was released on 2011 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt: Capacitive micromachined ultrasonic transducers (CMUTs), have been widely studied in academia and industry over the last decade. CMUTs provide many benefits over traditional piezoelectric transducers including improvement in performance through wide bandwidth, and ease of electronics integration, with the potential to batch fabricate very large 2D arrays with low-cost and high-yield. Though many aspects of CMUT technology have been studied over the years, packaging the CMUT into a fully practical system has not been thoroughly explored. Two important interfaces of packaging that this thesis explores are device encapsulation (the interface between CMUTs and patients) and full electronic integration of large scale 2D arrays (the interface between CMUTs and electronics). In the first part of the work, I investigate the requirements for the CMUT encapsulation. For medical usage, encapsulation is needed to electrically insulate the device, mechanically protect the device, and maintain transducer performance, especially the access of the ultrasound energy. While hermetic sealing can protect many other MEMS devices, CMUTs require mechanical interaction to a fluid, which makes fulfilling the previous criterion very challenging. The proposed solution is to use a viscoelastic material with the glass-transition-temperature lower than room temperature, such as Polydimethylsiloxane (PDMS), to preserve the CMUT static and dynamic performance. Experimental implementation of the encapsulated imaging CMUT arrays shows the device performance was maintained; 95 % of efficiency, 85% of the maximum output pressure, and 91% of the fractional bandwidth (FBW) can be preserved. A viscoelastic finite element model was also developed and shows the performance effects of the coating can be accurately predicted. Four designs, providing acoustic crosstalk suppression, flexible substrate, lens focusing, and blood flow monitoring using PDMS layer were also demonstrated. The second part of the work, presents contributions towards the electronic integration and packaging of large-area 2-D arrays. A very large 2D array is appealing for it can enable advanced novel imaging applications, such as a reconfigurable array, and a compression plate for breast cancer screening. With these goals in mind, I developed the first large-scale fully populated and integrated 2D CMUTs array with 32 by 192 elements. In this study, I demonstrate a flexible and reliable integration approach by successfully combining a simple UBM preparation technique and a CMUTs-interposer-ASICs sandwich design. The results show high shear strength of the UBM (26.5 g), 100% yield of the interconnections, and excellent CMUT resonance uniformity ([lowercase Sigma] = 0.02 MHz). As demonstrated, this allows for a large-scale assembly of a tile-able array by using an interposer. Interface engineering is crucial towards the development of CMUTs into a practical ultrasound system. With the advances in encapsulation technique with a viscoelastic polymer and the combination of the UBM technique to the TSV fabrication for electronics integration, a fully integrated CMUT system can be realized.

Download or read book Capacitive Micromachined Ultrasonic Transducers CMUTs Built with Wafer bonding Technology written by Yongli Huang and published by . This book was released on 2005 with total page 256 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Capacitive Micromachined Ultrasonic Transducers CMUTs for Therapeutic Applications written by Hyo-Seon Yoon and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: High-intensity focused ultrasound (HIFU) is a noninvasive method to treat a variety of diseases. Most of the HIFU machines in clinic typically consist of a piezoelectric transducer array and an imaging system for temperature monitoring and anatomical location guidance. One of the limitations of piezoelectric transducers is self-heating, which requires cooling systems to protect both transducers and patients. Capacitive micromachined ultrasonic transducers (CMUTs) are another type of transducers fabricated with silicon micromachining. CMUTs are promising candidates as therapeutic transducers, as they experience a lot less self-heating compared to piezoelectric transducers. This dissertation mainly focuses on describing the design, simulation, fabrication, characterization, and experimental results of CMUTs for HIFU applications. Single-element transducers are fabricated using local oxidation of silicon (LOCOS)-wafer-bonding process. The measurement part compares the self-heating of a PZT and a CMUT, and discusses the charging issue of CMUTs. Geometric focusing using multiple single-element CMUTs is also demonstrated. The fabrication of 1-D CMUT arrays to enhance the output pressure for HIFU applications is discussed. Higher output pressure of a CMUT cell can be achieved by adding one extra fabrication step to the existing fabrication process. Two-dimensional transducer arrays are required for electronic focusing and beam steering. An 8-channel continuous wave (CW) excitation system is developed to drive a 2-D CMUT array. This 8-channel system minimizes the system complexity without significant loss of focusing capability, compared to a full system with hundreds to thousands of channels. The first successful 2-D CMUT array fabricated using the thick-buried-oxide (BOX) process is presented. The breakdown issue of the insulation layer observed in the test stage is investigated as well. Another type of 2-D CMUT array fabricated using the sacrificial-release process is also tested for HIFU applications. Using the 8-channel CW excitation system, the 2-D CMUT array has proven to be able to produce enough output pressure for thermal ablation. This dissertation presents the result of ex-vivo experiments, which created thermal lesions on bovine tissue using a CMUT array for the first time.

Download or read book Analytical Modeling and Simulation of Capacitive Micromachined Ultrasonic Transducer written by Duy Le Nguyen and published by . This book was released on 2020 with total page 108 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents the design characterization, modeling and microfabrication of cMUTs. Four cMUTs arrays are designed with different array geometries, membranes’ dimensions as well as number of cMUT cells in an array. cMUTs are first analytically modeled and then simulated using finite element method (FEM) analysis to compare the numerical analysis results. The analytical cMUTs modeling is characterized for spring constant, resonant frequency and pull-in voltage. COMSOL Multiphysics 4.3b is use for simulation the profound insight of cMUTs’ behavior such as: resonant frequencies, pull-in voltage, membrane’s deflection and implied spring constant. This thesis also lays out the detail fabrication process flow of cMUTs. They are promised to be fabricated using mature of semiconductor processes which include photolithography, metal deposition and selective etching. In this thesis, in order to define the cMUT’s membrane, we will use direct wafer bonding technique with both chemical and O2 plasma surface activation processes to decrease the process temperature to as low as 4000C. In this thesis, the fabrication of cMUTs is proposed at low process temperature, providing compatibility with CMOS integration.

Download or read book Handbook of Silicon Based MEMS Materials and Technologies written by Markku Tilli and published by Elsevier. This book was released on 2020-04-17 with total page 1028 pages. Available in PDF, EPUB and Kindle. Book excerpt: Handbook of Silicon Based MEMS Materials and Technologies, Third Edition is a comprehensive guide to MEMS materials, technologies, and manufacturing with a particular emphasis on silicon as the most important starting material used in MEMS. The book explains the fundamentals, properties (mechanical, electrostatic, optical, etc.), materials selection, preparation, modeling, manufacturing, processing, system integration, measurement, and materials characterization techniques of MEMS structures. The third edition of this book provides an important up-to-date overview of the current and emerging technologies in MEMS making it a key reference for MEMS professionals, engineers, and researchers alike, and at the same time an essential education material for undergraduate and graduate students. Provides comprehensive overview of leading-edge MEMS manufacturing technologies through the supply chain from silicon ingot growth to device fabrication and integration with sensor/actuator controlling circuits Explains the properties, manufacturing, processing, measuring and modeling methods of MEMS structures Reviews the current and future options for hermetic encapsulation and introduces how to utilize wafer level packaging and 3D integration technologies for package cost reduction and performance improvements Geared towards practical applications presenting several modern MEMS devices including inertial sensors, microphones, pressure sensors and micromirrors

Download or read book Fabrication of PZT based Piezoelectric Micromachined Ultrasonic Transducers written by James Vincent Gigliotti and published by . This book was released on 2013 with total page 209 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Capacitive Micromachined Ultrasonic Transducers written by Dilruba Zaman Jeba and published by . This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Capacitive micromachined ultrasonic transducers (CMUTs) have been developed as an alternative to piezoelectric transducers for ultrasonic imaging in non-destructive testing applications. These CMUTs offer substantial advantages over their piezoelectric counterparts, which include a highly miniaturized system, easy integration with electronic control circuitry, a wider bandwidth, and a higher sensitivity. In this thesis, the design, fabrication and characterization of several single and array CMUT devices are reported. Many sizes of CMUTs, aiming to operate at different resonant frequencies, were fabricated using a PolyMUMPs sacrificial technique. An analytical and finite element model was used to further understanding of the physical behaviour of the transducer. The basic functionality of the CMUT devices was investigated through capacitance and electrical impedance measurements. These devices showed greater change in the capacitance and impedance data while operating close to their collapse voltages. This higher change in both capacitance and impedance is a result of a larger membrane displacement. The acoustic output power is directly related to the magnitude of the membrane's displacement. The transducers performance thus can be enhanced by operating close to their collapse voltage and obtained higher sensitivity. The optical characterization, performed on the single devices and on the 1-D arrays, provided a better understanding of the membrane vibration modes and displacement profiles at different resonant frequency modes. Acoustic measurements were performed to demonstrate the transmission capability of the CMUTs. The generated acoustic signals were detected using a commercial detector. These acoustic experiments demonstrated that these CMUTs can potentially be used as ultrasonic transducers alternative to piezoelectric transducers.

Download or read book Fabrication of a Capacitance Micromachined Ultrasonic Transducers CMUTs by Using Polymer Material written by Yi-Hsiang Su and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book All silicon Micromachined Acoustic Ejector Arrays for Micro Propulsion and Flow Control written by Tsung-Kuan Allen Chou and published by . This book was released on 2001 with total page 414 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Micromachined Ultrasonic Transducers written by and published by . This book was released on 1997 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Microfabricated ultrasonic transducers have been generated which operate in both liquids and gases. Air coupled through transmission of aluminum was observed for the first time using a pair of 2.3 MHz transducers. The dynamic range of the transducers was 110 dB, and the received signal had an SNR of 30 dB. Air coupled through transmission of steel and glass has also been observed. A theoretical model for the transducers has been refined and agrees well with experimental results. A robust microfabrication process has been developed and was used to generate air transducers which resonate from 2 to 12 MHz, as well as immersion transducers that operate in water from 1 to 20 MHz with a 60 dB dynamic range. Optimized immersion and air transducers have been designed and a dynamic range above 110 dB is anticipated. This development effort finds applications in hydrophones, medical ultrasound, nondestructive evaluation, ranging, flow metering, and scanning tip force sensing and lithography.

Download or read book 3D and Circuit Integration of MEMS written by Masayoshi Esashi and published by John Wiley & Sons. This book was released on 2021-03-16 with total page 528 pages. Available in PDF, EPUB and Kindle. Book excerpt: Explore heterogeneous circuit integration and the packaging needed for practical applications of microsystems MEMS and system integration are important building blocks for the “More-Than-Moore” paradigm described in the International Technology Roadmap for Semiconductors. And, in 3D and Circuit Integration of MEMS, distinguished editor Dr. Masayoshi Esashi delivers a comprehensive and systematic exploration of the technologies for microsystem packaging and heterogeneous integration. The book focuses on the silicon MEMS that have been used extensively and the technologies surrounding system integration. You’ll learn about topics as varied as bulk micromachining, surface micromachining, CMOS-MEMS, wafer interconnection, wafer bonding, and sealing. Highly relevant for researchers involved in microsystem technologies, the book is also ideal for anyone working in the microsystems industry. It demonstrates the key technologies that will assist researchers and professionals deal with current and future application bottlenecks. Readers will also benefit from the inclusion of: A thorough introduction to enhanced bulk micromachining on MIS process, including pressure sensor fabrication and the extension of MIS process for various advanced MEMS devices An exploration of epitaxial poly Si surface micromachining, including process condition of epi-poly Si, and MEMS devices using epi-poly Si Practical discussions of Poly SiGe surface micromachining, including SiGe deposition and LP CVD polycrystalline SiGe A concise treatment of heterogeneously integrated aluminum nitride MEMS resonators and filters Perfect for materials scientists, electronics engineers, and electrical and mechanical engineers, 3D and Circuit Integration of MEMS will also earn a place in the libraries of semiconductor physicists seeking a one-stop reference for circuit integration and the practical application of microsystems.

Download or read book Electromechanical Transducers and Wave Filters written by Warren Perry Mason and published by . This book was released on 1942 with total page 442 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Advances in Manufacturing Technology XXXII written by P. Thorvald and published by IOS Press. This book was released on 2018-08-29 with total page 558 pages. Available in PDF, EPUB and Kindle. Book excerpt: The urgent need to keep pace with the accelerating globalization of manufacturing in the 21st century has produced rapid advancements in technology, research and innovation. This book presents the proceedings of the 16th International Conference on Manufacturing Research incorporating the 33nd National Conference on Manufacturing Research (ICMR 2018), held in Skövde, Sweden, in September 2018. The aim of the conference is to create a friendly and inclusive environment, bringing together researchers, academics and industrialists with practical and theoretical knowledge to share and discuss emerging trends and new challenges. The book is divided into 12 parts, covering areas such as the manufacturing process; robots; product design and development; smart manufacturing; and lean, among others. Covering both cutting-edge research and recent industrial applications, the book will appeal to all those with an interest in recent advances in manufacturing technology.

Download or read book Mems Packaging written by Yung-cheng Lee and published by World Scientific. This book was released on 2018-01-03 with total page 363 pages. Available in PDF, EPUB and Kindle. Book excerpt: MEMS sensors and actuators are enabling components for smartphones, AR/VR, and wearable electronics. MEMS packaging is recognized as one of the most critical activities to design and manufacture reliable MEMS. A unique challenge to MEMS packaging is how to protect moving MEMS devices during manufacturing and operation. With the introduction of wafer level capping and encapsulation processes, this barrier is removed successfully. In addition, MEMS devices should be integrated with their electronic chips with the smallest footprint possible. As a result, 3D packaging is applied to connect the devices vertically for the most effective integration. Such 3D packaging also paves the way for further heterogenous integration of MEMS devices, electronics, and other functional devices.This book consists of chapters written by leaders developing products in a MEMS industrial setting and faculty members conducting research in an academic setting. After an introduction chapter, the practical issues are covered: through-silicon vias (TSVs), vertical interconnects, wafer level packaging, motion sensor-to-CMOS bonding, and use of printed circuit board technology to fabricate MEMS. These chapters are written by leaders developing MEMS products. Then, fundamental issues are discussed, topics including encapsulation of MEMS, heterogenous integration, microfluidics, solder bonding, localized sealing, microsprings, and reliability.