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Micromachined Ultrasound-Based Proximity Sensors presents a packaged ultrasound microsystem for object detection and distance metering based on micromachined silicon transducer elements. It describes the characterization, optimization and the long-term stability of silicon membrane resonators as well as appropriate packaging for ultrasound microsystems.
Micromachined Ultrasound-Based Proximity Sensors describes a cost-effective approach to the realization of a micro electro mechanical system (MEMS). The micromachined silicon transducer elements were fabricated using industrial IC technology combined with standard silicon micromachining techniques. Additionally, this approach allows the cointegration of the driving and read-out circuitry. To ensure the industrial applicability of the fabricated transducer elements intensive long-term stability and reliability tests were performed under various environmental conditions such as high temperature and humidity.
Great effort was undertaken to investigate the packaging and housing of the ultrasound system, which mainly determine the success or failure of an industrial microsystem. A low-stress mounting of the transducer element minimizes thermomechanical stress influences. The developed housing not only protects the silicon chip but also improves the acoustic performance of the transducer elements.
The developed ultrasound proximity sensor system can determine object distances up to 10 cm with an accuracy of better than 0.8 mm.
Micromachined Ultrasound-Based Proximity Sensors will be of interest to MEMS researchers as well as those involved in solid-state sensor development.
List of contents
1 Introduction.- 1.1 State of the Art of Ultrasound Proximity Sensors.- 1.2 Scope of this Thesis.- 1.3 Silicon Microsensors.- 1.4 Summary of Practical Results.- 2 Design Considerations For Silicon Resonators.- 2.1 Resonant Behavior of Microstructures.- 2.2 Excitation and Detection Principles.- 2.3 Sound Generation.- 3 Resonator Fabrication.- 3.1 Post IC-Fabrication.- 3.2 Silicon N-Well and Epi Membranes.- 4 Resonator Characterization.- 4.1 Membrane Characteristics.- 4.2 Mode Shapes of Membrane Resonator.- 4.3 Generation of Ultrasound.- 4.4 Sound Pressure Optimization of Resonator.- 4.5 Comparison between N-Well and Epi Membranes.- 4.6 Long Term Stability.- 5 Packaging of Transducers.- 5.1 Packaging Demands.- 5.2 Mounting of Transducers.- 5.3 Sound Emission from Front Side of Membrane.- 5.4 Sound Emission from Rear Side of Membrane.- 6 Ultrasound Barrier.- 6.1 Operation Principle.- 6.2 Packaged Prototype.- 7 Proximity Sensor.- 7.1 Amplitude Measurement with Two Transducers.- 7.2 Amplitude Measurement with One Transducer.- 7.3 Phase Measurement.- 7.4 Comparison between the Different Measurement Methods.- 8 Conclusion and Outlook.- 8.1 Conclusion.- 8.2 Outlook.
About the author
Oliver Brand is Professor of Bioengineering and Microelectronics/Microsystems at Georgia Institute of Technology, Atlanta, USA. He received his diploma degree in Physics from Technical University Karlsruhe, Germany, in 1990, and his PhD from ETH Zurich, Switzerland, in 1994. Between 1995 and 2002, he held research and teaching positions at the Georgia Institute of Technology (1995-1997) and ETH Zurich (1997-2002). Oliver Brand's research interest is in the areas of CMOS-based micro- and nanosystems, MEMS fabrication technologies, and microsystem packaging.
Summary
Micromachined Ultrasound-Based Proximity Sensors presents a packaged ultrasound microsystem for object detection and distance metering based on micromachined silicon transducer elements. The micromachined silicon transducer elements were fabricated using industrial IC technology combined with standard silicon micromachining techniques.
