Design and Fabrication of High-performance Capacitive Micro Accelerometers PDF Download
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Author: Fatemeh Edalatfar
Publisher:
ISBN:
Category :
Languages : en
Pages : 125
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Book Description
This thesis presents the development of capacitive high-performance accelerometers for sonar wave detection. Two different designs of in-plane and out-of-plane accelerometers are developed, micro-fabricated, and experimentally tested.The out-of-plane accelerometer is designed based on a continuous membrane suspension element. In comparison to beam-type suspension elements, the new design provides uniform displacement of the proof mass, lower cross-axis sensitivity, and lower stress concentration in suspension elements which could result in higher yield in the fabrication process. The out-of-plane accelerometer is fabricated using a novel microfabrication method which facilitates developing continuous membrane type suspension elements and full wafer thick proof mass for accelerometers. The designed accelerometer is fabricated on a silicon-on-insulator wafer with an 8 μm device layer, 1.5 μm buried-oxide layer, and 500 μm handle wafer. The developed accelerometer is proven to have resonance frequency of 5.2 kHz, sensitivity of ~0.9 pF/g, mechanical noise equivalent acceleration of less than 450 ng/√Hz, and an open loop dynamic range of higher than 130 dB while operating at atmospheric pressure.The in-plane single-axis accelerometer is designed based on a proposed mode-tuned modified structure. In this modified structure, the proof mass is substituted with a moving frame which also provides the area for increasing the number of sensing electrodes. This substitution contributes to widening the bandwidth of the accelerometer by locating the anchors and elastic elements both inside and outside of the moving frame. The designed accelerometer is fabricated on a silicon-on-insulator wafer with a 100μm device layer and high aspect ratio capacitive gaps of ~2 μm. The sensitivity of the accelerometer is measured as ~0.7 pF/g with the total noise equivalent acceleration of less than 500 ng/√Hz in the flat band region of the bandwidth. The resonance frequency of the devices is 4.2 kHz while maintaining a linearity of better than 0.7%. The open loop dynamic range of the accelerometer, while operating at atmospheric pressure, is higher than 135 dB, and the cross-axis sensitivity is less than -30 dB.
Author: Fatemeh Edalatfar
Publisher:
ISBN:
Category :
Languages : en
Pages : 125
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Book Description
This thesis presents the development of capacitive high-performance accelerometers for sonar wave detection. Two different designs of in-plane and out-of-plane accelerometers are developed, micro-fabricated, and experimentally tested.The out-of-plane accelerometer is designed based on a continuous membrane suspension element. In comparison to beam-type suspension elements, the new design provides uniform displacement of the proof mass, lower cross-axis sensitivity, and lower stress concentration in suspension elements which could result in higher yield in the fabrication process. The out-of-plane accelerometer is fabricated using a novel microfabrication method which facilitates developing continuous membrane type suspension elements and full wafer thick proof mass for accelerometers. The designed accelerometer is fabricated on a silicon-on-insulator wafer with an 8 μm device layer, 1.5 μm buried-oxide layer, and 500 μm handle wafer. The developed accelerometer is proven to have resonance frequency of 5.2 kHz, sensitivity of ~0.9 pF/g, mechanical noise equivalent acceleration of less than 450 ng/√Hz, and an open loop dynamic range of higher than 130 dB while operating at atmospheric pressure.The in-plane single-axis accelerometer is designed based on a proposed mode-tuned modified structure. In this modified structure, the proof mass is substituted with a moving frame which also provides the area for increasing the number of sensing electrodes. This substitution contributes to widening the bandwidth of the accelerometer by locating the anchors and elastic elements both inside and outside of the moving frame. The designed accelerometer is fabricated on a silicon-on-insulator wafer with a 100μm device layer and high aspect ratio capacitive gaps of ~2 μm. The sensitivity of the accelerometer is measured as ~0.7 pF/g with the total noise equivalent acceleration of less than 500 ng/√Hz in the flat band region of the bandwidth. The resonance frequency of the devices is 4.2 kHz while maintaining a linearity of better than 0.7%. The open loop dynamic range of the accelerometer, while operating at atmospheric pressure, is higher than 135 dB, and the cross-axis sensitivity is less than -30 dB.
Author: Arvind Sanjiva Salian
Publisher:
ISBN:
Category :
Languages : en
Pages : 406
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Author: Hamed Farahani
Publisher:
ISBN: 9780494527009
Category :
Languages : en
Pages : 352
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Book Description
This thesis reports the design and fabrication of MEMS based capacitive accelerometers for detection of defective equipment in automotive applications using PolyMUMPs fabrication technology. A design was developed denoting further improvements in accelerometer topologies based on the SOIMUMPs fabrication process. This research obtained accelerometers with sensitivities of 521 fF/mum and 0% cross-axis sensitivities. A prototype with 5 fF/mum sensitivity, 2.05% nonlinearity and an estimated effective bandwidth of 1.858 kHz for 1% response error with mechanical resolutions of 19.3 mug/√Hz was developed. A new approach to accelerometers configuration analysis is introduced, and future design based on this approach was developed to detect accelerations less than +/-25.9 mg with mechanical resolution of 3.45 mug for 1 kHz bandwidth and a readout circuitry of minimum accuracy of +/-4 fF. This work focuses on developing high performance accelerometers and exploring MEMS technology with contributions made to obtain higher performance devices from the fabrication processes.
Author: Mahmoud Rasras
Publisher: MDPI
ISBN: 3038974145
Category : Technology & Engineering
Languages : en
Pages : 252
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Book Description
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.
Author: Md Sohel Mahmood
Publisher:
ISBN:
Category : Accelerometers
Languages : en
Pages : 156
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Book Description
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.
Author: Navid Yazdi
Publisher:
ISBN:
Category : Accelerometers
Languages : en
Pages : 320
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Author: Ahmad Alfaifi
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
"This thesis proposes a methodology to optimize the design of capacitive accelerometers. This is achieved through a systematic improvement procedure of the closing-gaps accelerometers design. This is used to find the optimum electrode dimensions that would result in the highest sensitivity, within a specified area. The method is verified through the simulation and fabrication of different variations of two designs, then comparing the results with the expected values from analytical optimization methods. The prototypes are fabricated in a commercial process, which imposed limitations on the sizes of the possible accelerometer designs. A survey of prior published works shows the importance of the optimization technique suggested here to increase the performance of these types of sensors, when no fabrication restrictions exist.The thesis also introduces a novel low cross-sensitivity dual-axis capacitive accelerometer design. The device is fabricated in a silicon-on-insulator (SOI) process and its fabrication is finalized by an in-house release step. The device measures 1 mm × 1 mm, with four (4) proof masses that are able to sense accelerations in the X- and Y-axes independently. Two commercial capacitance-to-digital converters are used to read the outputs of both axes of the device in a system in package implementation. The fabricated device exhibits a sensitivity of 16.83 fF/g, while keeping the measured cross-sensitivity to less than 1 % throughout the ±4 g linear range. The rotational motion and Z accelerations have no impact on the device X and Y readings, thanks to the device's particular geometry and differential nature.In addition, the thesis presents a novel design of a 3D high-sensitivity lateral capacitive accelerometer. The accelerometer design utilizes the whole area of the sensor for both the sensing and proof masses, which cancels the tradeoff needed in conventional 2D designs. The design model of the accelerometer is developed to target the highest possible performance. A Z-shaped innovative design of the supporting beams is developed to limit the vertical displacement within the used submicron gap. The accelerometer measures 500 × 500 [mu]m2 and achieves 58 fF/g sensitivity in a ±4 g range in an open-loop system. Suggestions are provided to decrease the 1.4 mg noise floor of the device.Finally, the thesis describes a 3D surface micromachining platform process for above-IC integration. This method uses non-conductive materials with attractive mechanical properties to fabricate micro-electromechanical systems (MEMS) devices. The fixed structures are created using a polyimide layer, while the moving structures are built using silicon nitride (SiN). A 240-nm thin parylene-N polymer layer is used as a sacrificial layer to largely define the capacitive gaps and enable dry release. The photolithography steps are limited to four, in order to ensure a simple and low-cost process. The process has a thermal budget of 300 °C, which should be safe for processing above CMOS integrated circuits. While the used materials provide good results, this process is not limited to these specific materials, and others can be used if needed." --
Author: Henry Baltes
Publisher: John Wiley & Sons
ISBN: 3527616934
Category : Technology & Engineering
Languages : en
Pages : 612
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Book Description
Microstructures, electronics, nanotechnology - these vast fields of research are growing together as the size gap narrows and many different materials are combined. Current research, engineering sucesses and newly commercialized products hint at the immense innovative potentials and future applications that open up once mankind controls shape and function from the atomic level right up to the visible world without any gaps. Sensor systems, microreactors, nanostructures, nanomachines, functional surfaces, integrated optics, displays, communications technology, biochips, human/machine interfaces, prosthetics, miniaturized medical and surgery equipment and many more opportunities are being explored. This new series, Advanced Micro and Nano Systems, provides cutting-edge reviews from top authors on technologies, devices and advanced systems from the micro and nano worlds.
Author: Ashok Kumar Pandey
Publisher: Springer Nature
ISBN: 3031203534
Category : Technology & Engineering
Languages : en
Pages : 379
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Book Description
This book brings together investigations which combine theoretical and experimental results related to such systems as flexure hinges and compliant mechanisms for precision applications, the non-linear analytical modeling of compliant mechanisms, mechanical systems using compliance as a bipedal robot and reconfigurable tensegrity systems and micro-electro-mechanical systems (MEMS) as energy efficient micro-robots, microscale force compensation, magnetoelectric micro-sensors, acoustical actuators and the wafer bonding as a key technology for the MEMS fabrication. The volume gathers the contributions presented at the 6th Conference on Microactuators, Microsensors and Micromechanisms (MAMM), held in Hyderabad, India in December 2022. The aim of the conference was to provide a special opportunity for a know-how exchange and collaboration in various disciplines concerning systems pertaining to micro-technology. The conference was organized under the patronage of IFToMM (International Federation for the Promotion of Mechanism and Machine Science).
Author: Ankesh Todi
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
In this thesis, a high-frequency resonant accelerometer is presented. This novel sensor was designed to operate in 10’s of MHz frequency range utilizing an out-of-plane capacitive mechanism for acceleration sensing. The sensor is comprised of a 2-port RF MEMS piezoelectric resonator, operating at 27MHz, and a Capacitive Mass-spring structure. One of the resonator ports is electrically connected to the variable capacitor in the mass-spring structure. The acceleration is measured utilizing a piezoelectric stiffening mechanism, where a change in the termination impedance of a piezoelectric resonant body would result in a shift in the resonance frequency of the resonator. The acceleration is extracted from the frequency-modulated output signal of the resonator. The sensors were fabricated on a silicon-on-insulator wafer coated with a thin film of sputtered aluminum nitride as the piezoelectric transducer. Initial test results show a ~600Hz shift in resonance frequency in response to ±1g of acceleration (~300Hz/g sensitivity).
