The Piezojunction Effect in Silicon, its Consequences and Applications for Integrated Circuits and Sensors

This thesis describes an investigation of the piezojunction effect in silicon. The aim of this investigation is twofold. First, to propose some techniques to reduce the mechanical-stress-induced inaccuracy and long-term instability of many analogue circuits such as bandgap references and monolithic temperature transducers. Second, to apply the piezojunction effect to new mechanical sensor structures. The piezojunction effect changes the bipolar-transistor saturation current. This stress-induced change is mainly caused by the change in the conductivity of the minority-charge carriers. The piezojunction effect can be modeled by a polynomial approximation with a set of experimental constants, which are called the piezojunction coefficients. The magnitude of the piezojunction effect is determined according to the stress orientation and main carrier-flow direction through the bipolar-transistor base, both related to the silicon crystal axis. It has been found that the piezojunction effect hardly depends on the current density, as far the transistor is not operated in the high-injection level. Therefore, the voltage which is proportional to absolute temperature voltage VPTAT is much less stress sensitive than the base-emitter voltage VBE. The knowledge of the piezo-effects on device level has been used to predict and suggest methods to reduce their negative influence on the performance of important basic analogue circuits such as translinear circuits, temperature transducers and bandgap voltage references. A new stress-sensing element based on the piezojunction effect has been designed and tested. This stress-sensing element consists of two orthogonal L-PNP transistor pairs operated as a current mirror, which maximises the piezojunction effect and reduces the temperature cross-sensitivity. It has been verified that the linearity, gauge factor and temperature coefficient of the gauge factor are approximately the same as those of the sensors based on the piezoresistive effect. The predictable temperature-dependent base-emitter voltage can be used to compensate for the temperature coefficient of the gauge factor. For further reduction of the sensor area, a single lateral transistor with four split collectors has been designed to implement a stress-sensing device. In conclusion, it appears that the piezojunction effect is very suited to be used for low-power and miniaturised mechanical-stress sensors

Embedded system to evaluate the passenger comfort in public transportation based on dynamical vehicle behavior with user's feedback

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)This paper shows the development of a system (Hardware, Firmware and Software) focused to assess the dynamic motion factors that affect the comfort in public transportation systems. The data is collected, on-board processed and transported using the public transportation system vehicles as mobile smart sensors. Therefore, the acceleration measurement using a tri-axial accelerometer, the position detection using Global Positioning System (GPS) and the appropriate algorithms allow the system to detect rude driver styles and defects on the pavement. The firmware is composed by two algorithms. The first one is based on the detection of acceleration and Jerk magnitudes out of the comfort range, which is called Jerk-Acceleration Threshold Detection (JATD). An algorithm to compute the Jerk with comparable results to prior researches is proposed in this paper. The second algorithm, called Comfort Index with Acceleration Threshold Detection (CI-ATD), is based on the detection of acceleration values out of comfort range and the average ride comfort. The average ride comfort is supported by the recommendation of the international standard ISO2631-1. The comfort range or threshold values can be set using the user's perception. A software developed in LabVIEW (TM) interface, visualizes discomfort event in online maps for geographic location of each event. Also, the software implements road unevenness detection, which is based on the collected data analysis. The system was successful tested in a conventional bus line on its daily ride, the results reveals that most of the events are due to vertical acceleration disturbances. Also, a preliminary test indicates higher sensibility for vertical than longitudinal or transversal accelerations. (C) 2013 Elsevier Ltd. All rights reserved.47442451Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)CNPq [480864/2011-0

The Piezojunction Effect in Silicon. Consequences and Applications for Integrated Circuits and Sensors

This thesis describes an investigation of the piezojunction effect in silicon. The aim of this investigation is twofold. First, to propose some techniques to reduce the mechanical-stress-induced inaccuracy and long-term instability of many analogue circuits such as bandgap references and monolithic temperature transducers. Second, to apply the piezojunction effect to new mechanical sensor structures. The piezojunction effect changes the bipolar-transistor saturation current. This stress-induced change is mainly caused by the change in the conductivity of the minority-charge carriers. The piezojunction effect can be modeled by a polynomial approximation with a set of experimental constants, which are called the piezojunction coefficients. The magnitude of the piezojunction effect is determined according to the stress orientation and main carrier-flow direction through the bipolar-transistor base, both related to the silicon crystal axis. It has been found that the piezojunction effect hardly depends on the current density, as far the transistor is not operated in the high-injection level. Therefore, the voltage which is proportional to absolute temperature voltage VPTAT is much less stress sensitive than the base-emitter voltage VBE. The knowledge of the piezo-effects on device level has been used to predict and suggest methods to reduce their negative influence on the performance of important basic analogue circuits such as translinear circuits, temperature transducers and bandgap voltage references. A new stress-sensing element based on the piezojunction effect has been designed and tested. This stress-sensing element consists of two orthogonal L-PNP transistor pairs operated as a current mirror, which maximises the piezojunction effect and reduces the temperature cross-sensitivity. It has been verified that the linearity, gauge factor and temperature coefficient of the gauge factor are approximately the same as those of the sensors based on the piezoresistive effect. The predictable temperature-dependent base-emitter voltage can be used to compensate for the temperature coefficient of the gauge factor. For further reduction of the sensor area, a single lateral transistor with four split collectors has been designed to implement a stress-sensing device. In conclusion, it appears that the piezojunction effect is very suited to be used for low-power and miniaturised mechanical-stress sensors.Information Systems and Technolog

Simulation And Fabrication Of A Magnetic Actuator For Pumping Fluids In Microchannels

Microfluidic devices depend on the miniaturization of some components such as sensors, actuators and reactors to enable its applications and expand the possibilities. In this context, we fabricated an actuator capable of pumping fluids through microchannels and ensure the portability of the microfluidic device. The actuator uses the magnetic field generated by a coil to move a neodymium magnet over a PDMS diaphragm. Thus, the pressure variation within the microchannel and its geometry "nozzle-diffuser" causes the fluid to move preferentially in one direction. Finally, the influence of the diaphragm geometry and the electromagnetic force were analyzed to improve the efficiency of the actuator.Yih, T.C., Mei, C., Hammad, B., Modeling and characterization of a nanoliter drug-delivery MEMS micropump with circular bossed membrane (2005) Nanomedicine: Nanotechnology, Biology, and Medicine, 1 (2), p. 164Xia, N., Hunt, T.P., Mayers, B.T., Alsberg, E., Whitesides, G.M., Westervelt, R.M., Ingber, D.E., Combined microfluidic-micromagnetic separation of living cells in continuous flow (2006) Biomedical Microdevices, 8, pp. 299-308Fournier-Wirth, C., Coste, J., Nanotechnologies for pathogen detection: Future alternatives? (2010) Biologicals, 38, pp. 9-13Wang, Y.H., Tsai, Y.W., Tsai, C.H., Lee, C.Y., Fu, L.M., Design and analysis of impedance pumps utilizing electromagnetic actuation (2010) Sensors, 10 (4), pp. 4040-4052Ivnitski, D., Abdel-Hamid, I., Atanasov, P., Wilkins, E., Biosensors for detection of pathogenic bacteria (1999) Biosensors and Bioelectronics, 14, pp. 599-624Ibrahim, M.S.B., Mahat, M.M.B., CFD analysis of electromagnetic based valveless pump (2012) Procedia Engineering, 41, pp. 1524-1532Lee, C.Y., Chang, H.T., Wen, C.Y., A MEMS-based valveless impedance pump utilizing electromagnetic actuation (2008) Journal of Micromechanics and Microengineering, 18 (3), pp. 2-3Dau, V.T., Dinh, T.X., Tanaka, K., Sugiyama, S., Study on geometry of valveless-micropump (2009) 2009 IEEE/ASME International Conference: Advanced Intelligent Mechatronics, Singapore: IEEE Xplore, p. 308Chang, H.T., Lee, C.Y., Wem, C.Y., Hong, B.S., Theoretical analysis and optimization of electromagnetic actuation in a valveless microimpedance pump (2007) Microelectronics Journal, 38 (6-7), pp. 791-799Lee, C.Y., Chen, Z.H., Valveless impedance micropump with integrated magnetic diaphragm (2010) Biomed Microdevices, 12 (2), pp. 197-205Yufeng, S., Wenyuan, C., Feng, C., Weiping, Z., Electromagnetically actuated micropump with two flexible diaphragms (2006) The International Journal of Advanced Manufacturing Technology, 30 (3-4), p. 216Yen, L.C., Hsien, T.C., Lung, C.C., Hsiung, T.C., Nan, W.Y., Ming, F.L., Numerical simulation of electromagnetic actuator for impedance pumping (2011) Key Engineering Materials, 483, pp. 305-310Chang, H.T., Lee, C.Y., Wen, C.Y., Design and modelling of electromagnetic actuator in mems-based valveless impedance pump (2007) Microsystem Technologies, 13 (11-12), pp. 1615-1622Ribeiro, L.E.B., Piazzetta, M.H., Costa, J.S., Gobbi, A.L., Fruett, F., Fabrication and characterization of an impedance micro-bridge for lab-on-a-chip (2010) ECS Transactions, 31 (1), pp. 155-163Yang, H., Tsai, T., Hu, C., Portable valve-less peristaltic micropump design and fabrication (2008) DTIP of MEMS & MOEMS, pp. 273-278Zhang, Z., Zhao, P., Xiao, G., Benjamin, W.R., Xu, C., Sealing SU-8 microfluidic channels using PDMS (2011) Biomicrofluidics, 5 (4

Offset Reduction In A Multiple-terminal Hall Plate Using Current Spinning

The present work analyzes a four-terminal Hall-plate device to determine the main sources of error and explain how current-spinning technique can be used to effectively reduce offset and noise. Based on this analysis, an improved magnetic sensor is designed using an eight terminal octagonal Hall plate and a chopped-based control circuit to implement the current-spinning technique. Since Hall plates are complete compatible with the CMOS manufacturing process, a monolithic chip which contains the sensor, switches, digital control and bias circuit were fabricated using a 0.6 μm commercial CMOS process. These devices are used to test the offset cancellation methodology and compare if there are advantages related to the device orientation or switching sequence. Experimental results show a residual offset of 0.25 mT, a 99% reduction compared with the original offset level measured at Hall plate.Gridchin, A.V., The four-terminal silicon piezotransducer: History and future (2004) 5th Annual International Siberian Workshop and Tutorial on Electron Devices and Materials, pp. 21-23Popovic, R.S., (2010) Hall Effect Devices, Second Edition, , Series in Sensors. Taylor and FrancisBilotti, A., Monreal, G., Vig, R., Monolithic magnetic hall sensor using dynamic quadrature offset cancellation (1997) IEEE Journal of Solid-State Circuits, 32, pp. 829-836Munter, P.J.A., A low offset spinning-current hall plate (1990) Sensors and Actuators, A21, pp. 743-746Ramirez, J., Fruett, F., Octagonal geometry hall plate designed for the PiezoHall effect measurement (2013) 28th Symposium on Microelectronics Technology and Devices-SBMICROCoraucci, G., Finardi, M., Fruett, F., A multi-terminal pressure sensor with enhanced sensitivity (2009) 5th International Conference on Solid-State Sensors, Actuators and Microsystems-TransducersKanda, Y., Migitaka, M., Effect of mechanical stress on the offset voltage of hall devices in Si IC (1976) Phys. Status Solidi, 35, pp. 115-118Munter, P.J.A., Electronic circuitry for a smart spinningcurrent Hall plate with low offset (1991) Sensors and Actuators, A27Udo, A., Limits of offset cancellation by the principle of spinning current Hall probe (2004) Proceedings of IEEE, 24, pp. 1117-1120Bellekom, S., Sarro, L., Offset reduction of Hall plates in three different crystal planes (1997) Solid State Sensors and Actuators, 1997. TRANSDUCERS '97 Chicago., 1997 International Conference on, 1, pp. 233-236. , Jun

Octagonal Geometry Hall Plate Designed For The Piezohall Effect Measurement

Hall Effect transducers are the most popular kind of magnetic sensor; however, the offset voltage and drift of their characteristic have limited their usability. The main source of variation is the remaining mechanical stress in the crystalline silicon structure, related to the piezoresistive effect of the semiconductor materials, which can influence the offset and also the sensitivity of the device. This work is going to introduce an eight terminal hall plate fabricated using a commercial CMOS process, which can be used to study the different effects in the hall sensor in the main crystallographic directions. We also applied an offset reduction based in current spinning technique using the 8 terminals device and an on-chip control circuit. Finally, we show the design of the Hall plate over a silicon membrane which is suitable to measure the cross side effect between both hall and piezoeffect, which is called PiezoHall effect. © 2013 IEEE.ACM SIGDA,IEEE,IEEE Circuits and Systems Society (CAS),SBU,Sociedade Brasileira de Computacao (SBC)Chien, C.L., Westgate, C.R., The Hall effect and its applications (1980) NATO ASI Series: Series B, Physics, , Plenum PressPopovic, R., Randjelovic, Z., Manic, D., Integrated hall-effect magnetic sensors (2001) Sensors and Actuators, 91, pp. 46-50Popovic, R.S., Hall effect devices, second edition (2010) Series in Sensors. Taylor and FrancisBilotti, A., Monreal, G., Vig, R., Monolithic magnetic hall sensor using dynamic quadrature offset cancellation (1997) IEEE Journal of Solid-State Circuits, 32, pp. 829-836Munter, P.J.A., A low offset spinning-current hall plate (1990) Sensors and Actuators, A21, pp. 743-746Gridchin, V.A., Pirogova, R.A., Numerical simulation of multiterminal silicon piezoelements (1998) Sensors and Actuators, 65, pp. 5-9Creemer, J.F., Fruett, F., Meijer, G.C.M., French, P.J., The piezojunction effect in silicon sensors and circuits and its relation to piezoresistance (2001) IEEE Sensors Journal, 1, pp. 98-108Coraucci, G., Fruett, F., A theoretical study of a novel multi-terminal pressure sensor based on the transversal piezoresistive effect (2007) The Electrochemical Society, Inc. ECS Transactions, 9, pp. 561-569Kanda, Y., Migitaka, M., Effect of mechanical stress on the offset voltage of hall devices in si ic (1976) Phys. Status Solidi, 35, pp. 115-118Udo, A., Limits of offset cancellation by the principle of spinning current hall probe (2004) Proceedings of IEEE, 24, pp. 1117-1120Coraucci, G., Finardi, M., Fruett, F., A multi-terminal pressure sensor with enhanced sensitivity (2009) 5th International Conference on Solid-State Sensors, Actuators and Microsystems-Transducer