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Testing and calibration constitute a significant part of the overall manufacturing cost of microelectromechanical system (MEMS) devices. Developing a low-cost testing and calibration scheme applicable at the user side that ensures the continuous reliability and accuracy is a crucial need. The main purpose of testing is to eliminate defective devices and to verify the qualifications of a product is met. The calibration process for capacitive MEMS devices, for the most part, entails the determination of the mechanical sensitivity. In this work, a physical-stimulus-free built-in-self-test (BIST) integrated circuit (IC) design characterizing the sensitivity of capacitive MEMS accelerometers is presented. The BIST circuity can extract the amplitude and phase response of the acceleration sensor's mechanics under electrical excitation within 0.55% of error with respect to its mechanical sensitivity under the physical stimulus. Sensitivity characterization is performed using a low computation complexity multivariate linear regression model. The BIST circuitry maximizes the use of existing analog and mixed-signal readout signal chain and the host processor core, without the need for computationally expensive Fast Fourier Transform (FFT)-based approaches. The BIST IC is designed and fabricated using the 0.18-μm CMOS technology. The sensor analog front-end and BIST circuitry are integrated with a three-axis, low-g capacitive MEMS accelerometer in a single hermetically sealed package. The BIST circuitry occupies 0.3 mm2 with a total readout IC area of 1.0 mm2 and consumes 8.9 mW during self-test operation.
The work presented in this dissertation describes the design, fabrication and characterization of a Micro Electro Mechanical System (MEMS) capacitive accelerometer on a flexible substrate. To facilitate the bending of the accelerometers and make them mountable on a curved surface, polyimide was used as a flexible substrate. Considering its high glass transition temperature and low thermal expansion coefficient, PI5878G was chosen as the underlying flexible substrate. Three different sizes of accelerometers were designed in CoventorWare® software which utilizes Finite Element Method (FEM) to numerically perform various analyses. Capacitance simulation under acceleration, modal analysis, stress and pull-in study were performed in CoventorWare®. A double layer UV-LIGA technique was deployed to electroplate the proof mass for increased sensitivity. The proof mass of the accelerometers was perforated to lower the damping force as well as to facilitate the ashing process of the underlying sacrificial layer. Three different sizes of accelerometers were fabricated and subsequently characterized. The largest accelerometer demonstrated a sensitivity of 187 fF/g at its resonant frequency of 800 Hz. It also showed excellent noise performance with a signal to noise ratio (SNR) of 100:1. The accelerometers were also placed on curved surfaces having radii of 3.8 cm, 2.5 cm and 2.0 cm for flexibility analysis. The sensitivity of the largest device was obtained to be 168 fF/g on a curved surface of 2.0 cm radius. The radii of robotic index and thumb fingertips are 1.0 cm and 3.5 cm, respectively. Therefore, these accelerometers are fully compatible with robotics as well as prosthetics. The accelerometers were later encapsulated by Kapton® superstrate in vacuum environment. Kapton® is a polyimide film which possesses similar glass transition temperature and thermal expansion coefficient to that of the underlying substrate PI5878G. The thickness of the superstrate was optimized to place the intermediate accelerometer on a plane of zero stress. The Kapton® films were pre-etched before bonding to the device wafer, thus avoiding spin-coating a photoresist layer at high rpm and possibly damaging the already released micro-accelerometers in the device wafer. The packaged accelerometers were characterized in the same way the open accelerometers were characterized on both flat and curved surfaces. After encapsulation, the sensitivity of the largest accelerometer on a flat and a curved surface with 2.0 cm radius were obtained to be 195 fF/g and 174 fF/f, respectively. All three accelerometers demonstrated outstanding noise performance after vacuum packaging with an SNR of 100:1. Further analysis showed that the contribution from the readout circuitry is the most dominant noise component followed by the Brownian noise of the accelerometers. The developed stresses in different layers of the accelerometers upon bending the substrates were analyzed. The stresses in all cases were below the yield strength of the respective layer materials. AlN cantilevers as tactile sensors were also fabricated and characterized on a flexible substrate. Ti was utilized as the bottom and the top electrode for its smaller lattice mismatch to AlN compared to Pt and Al. The piezoelectric layer of AlN was annealed after sputtering which resulted in excellent crystalline orientation. The XRD peak corresponding to AlN (002) plane was obtained at 36.54o. The fabricated AlN cantilevers were capable of sensing pressures from 100 kPa to 850 kPa which includes soft touching of human index finger and grasping of an object. The sensitivities of the cantilevers were between 1.90 × 10-4 V/kPa and 2.04 × 10-4 V/kPa. The stresses inside the AlN and Ti layer, developed upon full bending, were below the yield strength of the respective layer materials.
Micro-electro-mechanical system (MEMS) devices are widely used for inertia, pressure, and ultrasound sensing applications. Research on integrated MEMS technology has undergone extensive development driven by the requirements of a compact footprint, low cost, and increased functionality. Accelerometers are among the most widely used sensors implemented in MEMS technology. MEMS accelerometers are showing a growing presence in almost all industries ranging from automotive to medical. A traditional MEMS accelerometer employs a proof mass suspended to springs, which displaces in response to an external acceleration. A single proof mass can be used for one- or multi-axis sensing. A variety of transduction mechanisms have been used to detect the displacement. They include capacitive, piezoelectric, thermal, tunneling, and optical mechanisms. Capacitive accelerometers are widely used due to their DC measurement interface, thermal stability, reliability, and low cost. However, they are sensitive to electromagnetic field interferences and have poor performance for high-end applications (e.g., precise attitude control for the satellite). Over the past three decades, steady progress has been made in the area of optical accelerometers for high-performance and high-sensitivity applications but several challenges are still to be tackled by researchers and engineers to fully realize opto-mechanical accelerometers, such as chip-scale integration, scaling, low bandwidth, etc. This Special Issue on "MEMS Accelerometers" seeks to highlight research papers, short communications, and review articles that focus on: Novel designs, fabrication platforms, characterization, optimization, and modeling of MEMS accelerometers. Alternative transduction techniques with special emphasis on opto-mechanical sensing. Novel applications employing MEMS accelerometers for consumer electronics, industries, medicine, entertainment, navigation, etc. Multi-physics design tools and methodologies, including MEMS-electronics co-design. Novel accelerometer technologies and 9DoF IMU integration. Multi-accelerometer platforms and their data fusion.
Micro Electro Mechanical Systems (MEMS) have an extensive use in different areas of technology. Inertial sensors (accelerometers and gyroscopes) are one of the most widely used devices fabricated using MEMS technology. MEMS accelerometers play an important role in different application areas such as automotive, inertial navigation, guidance, industry, space applications etc. because of low cost, small size, low power, and high reliability. This book presents a detailed SIMULINK model for a conventional capacitive sigma-delta accelerometer system consisting of a MEMS accelerometer, closed-loop readout electronics, and signal processing units (e.g. decimation filters). By using this model, it is possible to estimate the performance of the full accelerometer system including individual noise components, operation range, open loop sensitivity, scale factor, etc. The developed model has been verified through test results using a capacitive MEMS accelerometer, full-custom designed readout electronics, and signal processing unit implemented on a FPGA.
Micro-Electro Mechanical System (MEMS) is the micro-scale technology applying on various fields. Traditional testing strategy of MEMS requires physical stimulus, which leads to high cost specified equipment. Also there are a large number of wafer-level measurements for MEMS. A method of estimation calibration coefficient only by electrical stimulus based wafer level measurements is included in the thesis. Moreover, a statistical technique is introduced that can reduce the number of wafer level measurements, meanwhile obtaining an accurate estimate of unmeasured parameters. To improve estimation accuracy, outlier analysis is the effective technique and merged in the test flow. Besides, an algorithm for optimizing test set is included, also providing numerical estimated prediction error.
Inertial navigation is widely used for the guidance of aircraft, missiles ships and land vehicles, as well as in a number of novel applications such as surveying underground pipelines in drilling operations. This book discusses the physical principles of inertial navigation, the associated growth of errors and their compensation. It draws current technological developments, provides an indication of potential future trends and covers a broad range of applications. New chapters on MEMS (microelectromechanical systems) technology and inertial system applications are included.
The application of Micro Electro Mechanical Systems (MEMS) in the biomedical field is leading to a new generation of medical devices. MEMS for biomedical applications reviews the wealth of recent research on fabrication technologies and applications of this exciting technology.The book is divided into four parts: Part one introduces the fundamentals of MEMS for biomedical applications, exploring the microfabrication of polymers and reviewing sensor and actuator mechanisms. Part two describes applications of MEMS for biomedical sensing and diagnostic applications. MEMS for in vivo sensing and electrical impedance spectroscopy are investigated, along with ultrasonic transducers, and lab-on-chip devices. MEMS for tissue engineering and clinical applications are the focus of part three, which considers cell culture and tissue scaffolding devices, BioMEMS for drug delivery and minimally invasive medical procedures. Finally, part four reviews emerging biomedical applications of MEMS, from implantable neuroprobes and ocular implants to cellular microinjection and hybrid MEMS.With its distinguished editors and international team of expert contributors, MEMS for biomedical applications provides an authoritative review for scientists and manufacturers involved in the design and development of medical devices as well as clinicians using this important technology. Reviews the wealth of recent research on fabrication technologies and applications of Micro Electro Mechanical Systems (MEMS) in the biomedical field Introduces the fundamentals of MEMS for biomedical applications, exploring the microfabrication of polymers and reviewing sensor and actuator mechanisms Considers MEMS for biomedical sensing and diagnostic applications, along with MEMS for in vivo sensing and electrical impedance spectroscopy
Seven years have passed since the publication of the previous edition of this book. During that time, sensor technologies have made a remarkable leap forward. The sensitivity of the sensors became higher, the dimensions became smaller, the sel- tivity became better, and the prices became lower. What have not changed are the fundamental principles of the sensor design. They are still governed by the laws of Nature. Arguably one of the greatest geniuses who ever lived, Leonardo Da Vinci, had his own peculiar way of praying. He was saying, “Oh Lord, thanks for Thou do not violate your own laws. ” It is comforting indeed that the laws of Nature do not change as time goes by; it is just our appreciation of them that is being re?ned. Thus, this new edition examines the same good old laws of Nature that are employed in the designs of various sensors. This has not changed much since the previous edition. Yet, the sections that describe the practical designs are revised substantially. Recent ideas and developments have been added, and less important and nonessential designs were dropped. Probably the most dramatic recent progress in the sensor technologies relates to wide use of MEMS and MEOMS (micro-electro-mechanical systems and micro-electro-opto-mechanical systems). These are examined in this new edition with greater detail. This book is about devices commonly called sensors. The invention of a - croprocessor has brought highly sophisticated instruments into our everyday lives.