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TABLE V MICROPHONE CHARACTERISTICS Characteristics Value Resonant frequency 10 kHz Open circuit sensitivity -35 dB.V/Pa SNR 68 dB Fig. 9. Simulated spectral density of the output noise voltage. IV. MICROPHONE FABRICATION The fabrication of the microphone is based on the AMS 0.35 µm CMOS back-end process that encompass a passivation layer, four metal layers, three via layers and several silicon dioxide layers. The metal layers used for the microphone is M4 for the diaphragm and M2 for the fixed electrode. The silicon dioxide layer between M4 and M2 is a sacrificial layer which is removed by HF vapor etching. Fig. 10 shows the microphone before etching. Fig. 10. Microphone fabricated with the AMS 0.35 µm CMOS process before etching. V. CONCLUSIONS In this paper, we have proposed a simple model of a MEMS capacitive microphone to estimate its characteristics for audio applications. This lumped-parameters reduced model can still be improved, but it is useful for initial estimations. The structure of the microphone has been fabricated with a standard CMOS process (AMS 0.35 µm). A sacrificial etch of the silicon dioxide layers will be done in the near future to obtain the working microphone. If successful, it will be possible to integrate on the same chip the MEMS capacitive microphone and the electronic circuit. 11-13 May 2011, Aix-en-Provence, France REFERENCES [1] Ristic, L., “CMOS technology: a base for micromachining”, Microelectronics Journal, Vol. 20, No. 1-2, 1989, pp. 153-169. [2] Parameswaran, M., Baltes, H. P., Ristic, L., Dhaded, A. C., and Robinson, A. M. “A new approach for the fabrication of micromechanical structures”, Sensors and Actuators A, Vol. 19, No. 3, 1989, pp. 289-307. [3] Rufer, L., Domingues, C., Mir S., Petrini, V., Jeannot, J.-C., Delobelle, P., “A CMOS compatible ultrasonic transducer fabricated with deep reactive ion etching”, IEEE Journal of Microelectromechanical Systems, Vol. 15, No. 6, 2006, pp. 1766-1776. [4] Maillya, F., Giani, A., Bonnota, R., Temple-Boyerb, P., Pascal- Delannoya, F., Foucarana, A. and Boyer, A., “Anemometer with hot platinum thin film”, Sensors and Actuators A, Vol. 94, No. 1-2, October 2001, pp. 32- 38. [5] Fouladi, S., Bakri-Kassem, M., Mansour, R.R., “An Integrated Tunable Band-Pass Filter Using MEMS Parallel-Plate Variable Capacitors Implemented with 0.35 μm CMOS Technology”, IEEE/MTT-S International Microwave Symposium, 2007, pp. 505-508, 3-8 June 2007. [6] Dai, C. L., “A maskless wet etching silicon dioxide post CMOS process and its application”, Microelectronic Engineering, Vol. 83, 2006, pp. 2543- 2550. [7] Ganji, B.A., Majlis, B.Y;, “Design and fabrication of a new MEMS capacitive microphone using perforated diaphragm”, Sensors and Actuators A, Vol. 149, 2009, pp. 29-37. [8] Rabinovich, V. L., Gupta, R. K. and Senturia, S. D., “The effect of Release-Etch Holes on the Electromechanical Behavior of MEMS structures”, International Conference on International Solid State Sensors and Actuators Conference, Vol. 2, June 1997, pp. 1125-1128. [9] Sharpe, W. N. Jr., Vaidyanathan, R., Yuan, B., Bao, G.. and Edwards, R. L., “Effect of etch holes on the mechanical properties of polysilicon” Journal of Vacuum Science & Technology B (Microelectronics and Nanometer Structures), Vol. 15, Sep 1997, pp. 1599-1603. [10] Bao, M., Yang, H., “Squeeze film air damping in MEMS”, Sensors and Actuators, Vol. 136, 2007, pp. 3-27. [11] Veijola, T., “Compact model for a MEM perforation cell with viscous, spring and inertial forces”, Microfluid Nanofluid, 2009, Vol.6, pp. 203-219. [12] Mohite, S. S., Kesari, H., Sonti, V. R., and Pratap, R., “Analytical solutions for the stiffness and damping coefficients of squeeze films in MEMS devices with perforated backplates”, Journal of Micromechanics and Microengineering, Vol. 15, 2005, pp. 2083-2092. [13] Mohite, S. S., Venkata, R., Sonti, V. R. and Pratap, R., “A compact Squeeze-Film Model Including Inertia, Compressibility, and Rarefaction Effects for perforated 3-D MEMS Structures”, Journal of Microelectromechanical systems, Vol. 17, No. 3, June 2008, pp. 709-723. [14] Homentcovschi, D. and Miles, R. N., “Analitycal model for viscous damping and the spring force for perforated planar microstructures acting at both audible and ultrasonic frequencies”, Journal of the Acoustical Society of America, Vol. 124, July 2008, pp. 175-181. [15] Bendali, A., Labedan, R., Dominique, F., Nerguizian, V., “Hole effects on RF MEMS Parallel Diaphragms Capacitors”, Canadian Conference on Electrical and Computer Engineering 2006, May 2006, pp. 2140-2143. ©<strong>EDA</strong> <strong>Publishing</strong>/DTIP 2011 314 ISBN:978-2-35500-013-3
11-13 May 2011, Aix-en-Provence, France A Novel Integrated Solution for the Control and Diagnosis of Electrostatic MEMS Switches Carlo Trigona, Norbert Dumas, Laurent Latorre and Pascal Nouet LIRMM, University Montpellier II / CNRS 161 rue Ada - 34095 Montpellier Cedex 5, France Abstract- The aim of this paper is to present a novel integrated solution for the control and diagnosis of electrostatic MEMS switches. A custom multi-channel integrated circuit (ASIC) has been designed and fabricated adopting a standard High- Voltage (HV) CMOS technology with a maximum operating voltage of 50V. Each channel is composed of a HV driver to actuate electrostatic switches and a diagnosis element to monitor the movement of the beam. This control circuit is particularly interesting for systems based on a large array of MEMS switches with a certain level of redundancy or fault tolerance, an active reflect array antenna in our case. The diagnosis principle has been modeled, simulated and an experimental campaign validates the principle with real actuators. I. INTRODUCTION During the past decade, RF Micro Electro Mechanical Systems (RF-MEMS) have been reported in several areas of engineering and science. The fabrication of MEMS for RF integrated circuits has seen a rapid rate of expansion within a broad range of applications such as: resonators [1], tunable filters [2], radar sensors [3] array, reconfigurable antennas [4] and RF switches [5]. In particular, reflect array antennas based on phase shifters to tune the reflecting angle of a wave have attracted particular interest for applications such as communication satellite. Main advantages are their small size, high performance, reduced power consumption and lightness. Such communication systems are composed of thousands of RF switches embedded into a single panel and electrostatically actuated, although magnetic, thermal or even gas-based forces are alternative solutions to move micromachined structures. Due to the large number of control signals (one for each actuators), control architecture must be embedded in the panel. Basically, the adoption of a distributed network of ASIC devices presents several advantages such as small overall dimension, integration with the phase-shift panel, short distance from the RF switch to the control driver and reduced interconnection complexity within the panel. Due to the high number of RF switches, the phase-shift panel implements a certain degree of redundancy (i.e. achieving the same phase shift with various combination of switches) [6]. Fault-tolerance can then be easily implemented by monitoring the state of each RF MEMS, detecting non-working MEMS and configuring the panel accordingly. Several diagnostic approaches have been considered: optical monitoring [7], electromagnetic [8], resistive [9], or capacitive sensing [10]. These approaches imply complex diagnosis principles, additive sensing elements and/or parasitic-capacitance dependent solutions. The presented approach allows on-line testing of MEMS switches and exhibits several attractive features: • fully integrated within the driver, • active during each pull-in and pull-off events, • tolerant to large parasitic capacitances. The two last points are the real innovation of this driver compared to previously proposed drivers by the same authors [11]. The diagnosis circuitry can cope with large parasitic capacitances and can also detect the MEMS switch-off. This paper first reports the working principle of the proposed smart driver with a particular emphasis on diagnosis. Design and simulation are reported in a second section while experimental results finally demonstrate that we can detect both pull-in and pull-off events of the actuated beam thus demonstrating the suitability of the proposed solution. II. WORKING PRINCIPLE The diagnosis principle has been derived from an external test solution proposed in [12]. Here, we propose to associate an integrated diagnosis unit to each control channel. It is then composed with a control unit itself and an add-on circuitry for diagnosis (Figure 1). n = 10 n∙I act VDDA Diagnostic unit VDDA n∙I act I discharge C ramp Diag1 Diag2 VDD_HV I1 V th1 I2 V th2 I charge R1 C int V ref Buffer OUT Control unit IN I act R s MEMS C act Fig. 1. Schematic diagram of a control channel with embedded diagnosis. C p 315
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COLLECTION OF PAPERS PRESENTED AT T
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III
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Table of Contents Wednesday 11 May
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PANEL DISCUSSION TEXTILE MICROSYSTE
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SPECIAL SESSION OF BIO-MEMS/NEMS a
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suspended membrane can be pulled to
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that detectors may measure the diff
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2) Cavity width effect To verify th
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Fig.9. Capacitive sensor output, Va
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The fabrication of optical Cap-Wafe
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Y X Fig. 1. Scanning electron mic
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etween x 2 to L (remember that x 2
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piezoelectric displacement transduc
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A. Continuous domain Starting from
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700 11-13 May 2011, Aix-en-Provenc
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o o o o o o o o Check applicability
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C. Identification Results The ident
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teen wire segments of a coil, as in
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As the metallization is too reflect
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B. Implemented die overview A die c
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IN CLK OUT Fig. 16. Probe setup for
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adhesive material with 30μm thickn
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B. Dynamics of Energy Flows For a l
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80˚C. Additionally, we looked into
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fibers which define the electric co
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Figure 15. Key board input system.
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ρ = h 2∆α∆T + + E 1h 3 1 +E 2
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In recent years, the pipe flow moni
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inches silicon wafers which have th
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samples tested in different vacuum
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l c 11-13 May 2011, Aix-en-Provence
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Vp (V) 3,5 3,0 2,5 2,0 1,5 1,0 0,5
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II. MATHEMATICAL MODEL AND NUMERICA
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fluids travel along a curved channe
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measured mixing indices are depicte
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length, which enables them to focus
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however, a rotation for coincidence
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excludes the nature of the fixed bo
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value of every active channel. Ther
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electrocardiogram. • The heart be
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Fig. 8 Concept of the in-home perso
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found that the early-stage diagnosi
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Power monitoring data detected by w
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device consisted of a bimorph canti
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operation, the pressure inside the
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coefficient compatible with the mic
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Variable Description Value Crab-leg
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focusing increased both as the stre
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Time of diffusion (hr) 1200 1000 80
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Chip Magnet Light source Hot plate
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above, they would move to upward an
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This phenomenon is now reaching the
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The VerilogA block code is : 11-13
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Author Index Abi-Saab D. 81 Aimez V
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Nussbaum Dominic 273 O’Hara T. 35
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