Login

Members

TOUNSI Farès

Mr TOUNSI Farès
Assistant Professor

Department of Electrical Engineering
ISIM Monastir
Monastir University
 
Address: Sakiet Eddaier 3011 Sfax Tunisia
Phone:
Fax:
email:
CV:

Fares Tounsi, received the B.Sc.’01 and M.Sc.’03 degrees from National Engineering School of Sfax (ENIS) in Tunisia, and the Ph.D.’10 in Micro and Nano-electronics from Grenoble Institute of Technology (INPG), France. He is currently an Assistant Professor in the Institut Superieur d’Informatique et de Mathematiques de Monastir (ISIMM), Tunisia. Currently, he is working on the design, modeling and simulation of new CMOS compatible micromachined sensors. Specifically, he is interested in novel designs of microphones, accelerometers and RF switches. In addition, he is now focusing on the field of nanotransducers, evaluation of new materials/ structures for MEMS and advanced microsystems.



TOUNSI Farès

Publication


Mezghani B., Haboura K., Tounsi F., Smaoui S., El-Borgi S., Choura S. and Masmoudi M.

Theoretical and Numerical modeling of a CMOS micromachined acoustic sensor , In Proceedings of International Conference on Design and Test of Integrated Systems in Nanoscale Technology, September 5-7, Tunisia, 441-444 (IEEE – DTIS 2006). , 2006-09-07
[Abstract]
Abstract
In this paper, we present theoretical and numerical modeling done on a new structure of CMOS micromachined inductive microphone. Its mode of operation is based on the variation of the mutual inductance between an external fixed inductor and an internal suspended inductor. This internal inductor is designed on a 1.4x1.4mm2 suspended membrane. The displacement of the suspended membrane with two different attachment structures, the I-shaped and the L-shaped beams, is studied. Using a theoretical mechanical modeling, we get displacement values of 13.11µm and 68.82 µm, for the I-shaped and L-shaped beam design, respectively. With a numerical FEM analysis, using the Ansys software, displacement values of 12.7µm and 63.5 µm were found for the I-shaped and L-shaped beam design, respectively. Using the analogy between acoustic, mechanical and electrical domains, the dynamic behavior of the L-shaped beam design sensor is studied and a corner frequency around 200 kHz is found. This value is also found when applying analytical dynamics principles to determine the equations of motion for the suspended membrane. A FEM analysis, using the Ansys software, is conducted in order to validate this theoretical model.

B. Mezghani, F. Tounsi, S. Smaoui and M. Masmoudi

Mechanical Noise Modeling of a new Micromachined Acoustic Sensor , CD-ROM International Multi-Conference on Systems, Signals & Devices, March 19-22, Tunisia (IEEE – SSD 2007). , 2007-03-23
[Abstract]
Abstract
In this paper, we present mechanical-thermal noise calculation and modeling for a new CMOS micromachined acoustic sensor. This new inductive microphone has a suspended moving membrane attached to the substrate with 4 attachment arms. Two different attachment structures are studied. The membrane has a 1.4x1.4mm2 surface and a total mass of 22.4 µg. The natural frequency of the suspended membrane is found for the two different attachment structures, the I-shaped and the L-shaped beams. Using a theoretical mechanical modeling, we get natural frequency values of 263 kHz and 115 kHz, for the I-shaped and L-shaped beam design, respectively. With a numerical FEM analysis, we get natural frequency values of 238 kHz and 154 kHz. Average natural frequency values of 250 kHz and 134 kHz are used. Thermal noise contribution of the two different attachment types is investigated. In addition, damping factor and noise level are evaluated for different membrane mass values. It is found that the thermal noise contribution is about the same for the I-shaped and L-shaped beam designs. The same conclusion is drawn when the mass of the membrane is changed.

B. Mezghani, F. Tounsi and M. Masmoudi

Mechanical-Thermal Noise Characterization of a new Micromachined Acoustic Sensor , In Proceedings of SPIE Fluctuations and Noise, Noise and Fluctuations in Circuits, devices and Materials, Vol. 6600, 660015, Florence, Italy (SPIE – FN 2007). , 2007-04-06
[Abstract]
Abstract
A new integrated CMOS micromachined inductive microphone is studied and characterized for mechanical-thermal noise. This acoustic sensor has one suspended membrane attached to the substrate with 4 arms, the I-beam or L-beam shaped attachments. This membrane has 1.4x1.4mm2 active area, 22µg mass and its natural frequency is found to be around 250 kHz, for the I-beam and 134 kHz, for the L-beam attachment. We give a brief explanation of the superiority of this new design over conventional acoustic sensors. Then, some experimental points are discussed and solutions are given. This sensor is analyzed for mechanical-thermal noise by applying a new developed analysis based on mass and natural frequency. Our system damping factor is found to be 5x10-2 N.s.m-1, which gives a fluctuating force spectral density of 2.88x10-11 N.Hz-1/2. This corresponds to an A-weighted sound level of about 39 dB(A) SPL. A SNR value of 55 dB is found for an incident pressure of 1 Pa on the suspended membrane. The relationship between the SNR and the mechanical and geometrical characteristics of the suspended membrane is also investigated. Finally, our sensor mechanical noise displacement is evaluated, around 10-15 m.Hz-1/2, and plotted for the two attachment types.

B. Mezghani, A. Brahim, F. Tounsi, A.A. Rekik, M. Masmoudi and P. Nouet

From 2D to 3D FEM simulations of a CMOS MEMS convective accelerometer , International Conference on Microelectronics, December 2011, Hammamet, Tunisia (IEEE – ICM 2011). , 2011-12-23
[Abstract]
Abstract
In this paper, we present 3D FEM simulations of a CMOS MEMS convective accelerometer. Differences between 3D and previously published 2D simulations are also discussed. We describe sensor architecture and we present a sensor model that is used for 3D FEM simulations. The prototype has a heater-cavity border distance of 350µm. We show the details of the sensitivity evaluation along the sensitive axis. It is found that the maximum sensitivity location is at a distance of 125µm from the heater center. So, the detector should be placed closer to the heater than the mid distance. It is shown that this is closely related to the smaller size of isotherms obtained in 3D simulations.

B. Mezghani, F. Tounsi, A.A. Rekik, F. Mailly, M. Masmoudi and P. Nouet

Efficiency modeling of a CMOS MEMS convective accelerometer , International Conference on Design and Technology of Integrated Systems in Nanoscale era, May 2012, Guammarth, Tunisia, (IEEE – DTIS 2012). , 2012-03-23
[Abstract]
Abstract
This paper reports efficiency modeling using 3D FEM simulation of a convective accelerometer obtained by FSBM of a die fabricated using standard CMOS technology. In such sensors, best sensitivity is obtained by placing temperature detectors where air temperature is the most sensitive to acceleration. This will obviously depends on 3D effects. In a previous work, a behavioral model of the sensor including only 2D effects was developed. This work investigates 3D effects which give the opportunity to better predict not only sensor sensitivity but also power dissipation. Experimental sensitivity values and 3D FEM ones are verified for two different sensors and two different heater temperatures. For a prototype having a heater-cavity border distance of 340µm and a heater length of 230µm, maximum sensitivity point is obtained for detectors localized at a distance of 125µm from heater center. Using this 3D geometry in FEM simulations, we show that electrical power decreases more rapidly than sensitivity when heater length is reduced. Moreover, when detectors are shortened, the sensitivity will be quite higher with an optimal value obtained for a detector implemented on one third of the side bridge.

B. Mezghani, F. Tounsi, H. Yaich and M. Masmoudi

Conductive Behavior Modeling of Dual-axis CMOS MEMS Convective Accelerometers Using 3D FEM and Spherical Model , International Multi-Conference on Systems, Signals & Devices, March 2013, Hammamet, Tunisia (IEEE – SSD 2013). , 2013-03-22
[Abstract]
Abstract
This paper presents heat conduction modeling of dual axis micromachined convective accelerometers. Results from FEM simulation are used to develop an analytical model of heat conduction main parameters. Two variables are used in FEM simulations: heater temperature and cavity depth. The latter parameter has a large impact on the overall conductive behavior of thermal accelerometers since it fixes the volume where the heat bubble can expand. Simulation results are used in a derived spherical model to develop an analytical expression of outer isotherm equivalent radius. The hot bubble radius and form are closely related to sensor geometry parameters and temperature. Two distinct equivalent radius modeling are studied and are used to express both heater heat transfer coefficient and common mode. These physically-based derived expressions govern the overall sensor conductive behavior. It is also shown that these derived expressions are still valid for different sensor design geometries.

B. Mezghani, F. Tounsi and M. Masmoudi

Sensitivity Modeling of dual-axis CMOS MEMS Convective Accelerometers using FEM and Spherical Model , Symposium on Design, Test, Integration and Packaging of MEMS/MOEMS, April 2013, Barcelona, Spain (DTIP 2013). , 2013-04-19
[Abstract]
Abstract
This paper presents sensitivity behavior study and optimization of dual axis CMOS MEMS convective accelerometers using both analytical and FEM techniques. In a first part, newly developed accelerometer 3D model is used in FEM simulations. Using different sizes for micromachined and square cover shapes, it is found that sensitivity readings and its maximum position in cavity are affected by both cover size and shape. In addition, micromachined bottom cavity, with half width of 300µm, is found to produce sensitivity saturation starting at a depth of 200µ for both cover shapes. The used cover size is that offering maximum sensitivity readings. From computed heating efficiency values, it is concluded that dual axis accelerometers are more power efficient than single axis ones. In the second part, we present Hardee’s spherical model and investigate its possible application on the dual axis accelerometer. It is concluded that inner and outer isotherms deformation should be modeled by including sensor geometry parameters in governing equations.

Mezghani B., Tounsi F., Smaoui S., Haboura K., El-Borgi S., Choura S. and Masmoudi M.

Modelling and Simulation of a new Micromachined Acoustic Sensor , TRENDS IN APPLIED SCIENCES RESEARCH, Academic Journals Inc., USA 1 (5), 456-466. , 2006-10-16
[Abstract]
Abstract
In this paper, we present modelling and simulation results of a new micromachined acoustic sensor. Equation derivation of the variable mutual inductance is summarized. Two attachment structures of the suspended membrane, the I-shaped and L-shaped beams, are modelled and simulated. Using a theoretical mechanical modelling, we get displacement values of 13.11µm and 68.82 µm, for the I-shaped and L-shaped beam design, respectively. With a numerical FEM design, displacement values of 12.7µm and 63.5 µm were found for the I-shaped and L-shaped beam design, respectively. Using the analogy between acoustic, mechanical and electrical domains, the dynamic behaviour of the microphone is modelled, then simulated and a corner frequency around 200 kHz is found. This same value is found when applying analytical dynamics principles to determine the equations of motion for the suspended membrane. A FEM analysis is conducted in order to validate this theoretical model. This sensor is analyzed for mechanical-thermal noise by modelling the suspended membrane with its mass-spring oscillator diagram. The damping factor is found to be 4x10-2 N s m-1, which gives a fluctuating force spectral density of 2.57x10-11 N Hz-1/2 and an A-weighted sound level of about 38 dB(A) SPL.

B. Mezghani, F. Tounsi and M. Masmoudi

Static behavior analytical and numerical analysis of micromachined thermal accelerometers , TRANSACTIONS ON SYSTEMS, SIGNALS & DEVICES (TSSD), ISSUES ON SENSORS, CIRCUITS & INSTRUMENTATION SYSTEMS, SHAKER-VERLAG GMBH, 9 (4), 1-21. , 2013-09-16
[Abstract]
Abstract
This paper presents static behavior analytical study of micromachined convective accelerometers. This includes both heat conduction and convection behavior study and modeling. A mixed modeling technique has been used to derive general expressions governing heat conduction and convection of MEMS thermal accelerometers. This technique is based on the use of results from FEM simulations to develop an analytical model where all derived expressions are as a function of biasing temperatures and key design geometry parameters. For conduction behavior analysis, two variables are being used in FEM simulations: heater temperature and micromachined cavity depth. The latter parameter has a large impact on the overall conductive behavior of thermal accelerometers since it fixes the volume where the heat bubble can expand. In addition, heater temperature is considered to be the only parameter that fixes heat distribution in the cavity. This modeling has led to the derivation of expressions for both heater heat transfer coefficient and common mode temperature. These physically-based derived expressions govern the overall sensor conductive behavior. Concerning heat convection behavior, cavity width parameter has been added as a third variable. Using simulation data points, fitting technique has been used to develop an analytical expression of differential temperature, proportional to sensitivity, as a function of the above design and temperature parameters. This study helps to predict sensor performance at an early design stage and more importantly for different sensor design geometries and temperatures.

B. Mezghani, F. Tounsi, and M. Masmoudi

Dual-axis CMOS MEMS Convective Accelero-meters sensitivity modeling using FEM and spherical model , 15th Conference in Design, Test, Integration & Packaging of MEMS/MOEMS, DTIP'13, 16-18 April, 2013, Barcelona, Spain. , 2013-04-16
[Abstract]
Abstract

B. Mezghani, F. Tounsi and M. Masmoudi

Development of an accurate heat conduction model for micromachined convective accelerometers , MICROSYSTEM TECHNOLOGIES, SPRINGER, http://dx.doi.org/10.1007/s00542-014-2079-x, 21 (2), 345-353. , 2015-01-05
[Abstract]
Abstract
This paper presents detailed development of a heat conduction model adapted for micromachined convective accelerometers. Fitting expressions obtained from FEM data are used in derived spherical model expressions to come up with an accurate analytical model of heat conduction main parameters: common mode temperature and heat transfer coefficient. Two variables have been used in FEM analysis: applied heater temperature and micromachined cavity depth. The latter parameter has a large impact on the overall conductive behavior of thermal accelerometers since it fixes the volume where produced heat bubble can expand. In addition, this depth is one of the two main reasons behind the produced isotherms deformation. Isotherm bending is also due to the high aspect ratio in heater width and height imposed by the technology. Since the produced hot bubble form is closely related to sensor design and heater temperature, then spheres deformation modeling has been used to derive conduction model equations. Two distinct equivalent radius modeling are studied and are used to express conduction behavior in analytical expressions. For comparison, Hardee’s conduction solution is given and it has found that our solution gives a more accurate reading of common mode temperature. Therefore, Hardee’s solution has to be revised if it is to be used for convective accelerometers. It is also shown that derived expressions are still valid for various sensor designs and that conductive behavior of thermal accelerometers can be predicted in an early stage and for all possible design geometries and biasing temperatures.

B. Mezghani, F. Tounsi, A.A. Rekik, F. Mailly, M. Masmoudi and P. Nouet

Sensitivity and power modeling of CMOS MEMS single axis convective accelerometers , Elsevier Microelectronics Journal, Vol. 44, Issue 12, Dec 2013, pp 1092–1098. , 2013-12-12
[Abstract]
Abstract
In this paper,we present 3D finite element modeling and simulation of a CMOS/MEMS single axis convective accelerometer. We describe the sensor architecture and present a sensor geometry model to be used in 3D FEM simulations. Differences between 3D and previously published 2D simulation sare discussed. This work investigates 3D effects which give the opportunity to better predict not only sensor sensitivity but also power dissipation.Experimental sensitivity values and 3D FEM ones are compared for two different sensor geometries and two different heater temperatures.For a prototype having a heater- cavity border distance of 340 mm and a heater length of 230 mm, maximum sensitivity point is obtained for detectors localize data distance of 125 mm from heater center.This distance should be moved to 90 mm if a 50 mm heater length issued. So, detectors should be placed closer to the heater than the usually used mid-distance. Moreover, optimal detectors location shifts closer to the heater as heater length shrinks. We also show that if heater length is reduced by 80% (from 230 to 50 mm), then both electrical power and sensitivity decrease by 63% and 55%,respectively. So, best efficiency is obtained for shorter heaters. In addition, detector's length decrease is found to have a significant effect on sensitivity, with an increase of 58% and 87% using heater lengths of 230 mm and 50 mm, respectively. Here, detector's length decreased from the total side bridge length to a fraction of this length equals to 2.5%.Optimal length is obtained when detectors are implemented on the same side bridge fraction as that used to implement the heater on the central bridge.

B. Mezghani, F. Tounsi and M. Masmoudi

Convection Behavior Analysis of CMOS MEMS Thermal Accelerometers Using FEM and Hardee's Model , Springer Journal of Analog Integrated Circuits and Signal Processing, Vol. 78, Issue 2, Feb 2014, pp 301-311. , 0000-00-00
[Abstract]
Abstract
This paper presents convection behavior investigation of CMOS MEMS convective accelerometers using both analytical and FEM techniques. In a first part, a newly developed accelerometer 3D model is used in FEM simulations to model convection behavior as a function of design geometry and temperature. Using various sizes of two different cover shapes, sensitivity reading and its maximum position in cavity are found to be largely affected by both cover size and shape. In addition, a sensor with cavity width of 600 lm produces sensitivity saturation starting at a cavity depth of 200 lm, for both cover shapes. Using FEM data and curve fitting, differential temperature is claimed to be linearly linked to the effective heater temperature to the power of 1.7. Using the same cavity design and from computed heating efficiency values, we found that a 60 lm width heater offers the best efficiency. This cavity and heater designs give an optimal detector position of 120 lm from heater center along the sensitive axis. Moreover, dual axis accelerometers are found to be more power efficient than single axis ones. In the second part, we present Hardee’s spherical model and investigate its possible application on convective accelerometers. It is shown that inner and outer isotherms deformation, caused by accelerometer design and convection process, should be modeled by including sensor geometry parameters in the derived governing equations. Moreover, Hardee’s biasing temperature relation has to be revised if it is to be used for convective accelerometers.