This paper presents use of the simple cantilever beam as a Clamped free MEMS resonator, it’s design, Eigen frequency and electrostatic analysis. This resonator requires 4V DC voltage and has a quality factor of 1302.5
DOI: 10.17762/ijritcc2321-8169.150611

, Ms .Vijaya V .Gomase, Prof. Mr. Vipin S. Bhure

English

International Journal on Recent and Innovation Trends in Computing and Communication

International Journal on Recent and Innovation Trends in Computing and Communication                                                   ISSN: 2321-8169 Volume: 3 Issue: 6                                                                                                                                                                        4072 - 4074 ______________________________________________________________________________________________  4072 IJRITCC | June 2015, Available @ http://www.ijritcc.org                                                                 _______________________________________________________________________________________  Design & Analysis of Clamped Free MEMS Resonator   Ms .Vijaya V .Gomase Electronics & Communication                                                                                                      Engineering GHRAET, Nagpur University (RTMNU)  Nagpur, India shilpa.gomase@rediffmail.com                                                                                         Prof. Mr. Vipin S. Bhure Electronics & Communication                                                                                                      Engineering  GHRAET, Nagpur University (RTMNU)  Nagpur, India vipin.bhure@raisoni.net Abstract— This paper presents use of the simple cantilever beam as a Clamped free MEMS resonator, it’s design, Eigen frequency and electrostatic analysis. This resonator requires 4V DC voltage and has a quality factor of 1302.5  Keywords-  MEMS, Clamped free resonator, Eigen frequency __________________________________________________*****_________________________________________________  I. INTRODUCTION MEMS are a micro electro mechanical system. They have been developed since the 1970s. In the last decade Micro-Electromechanical System (MEMS) devices have experienced a tremendous development in various fields of the Information and Communication Technologies (ICT). Especially the recent trends towards the interaction between integrated circuits (IC) components and external environment pushed for the design of innovative devices and technologies able to couple electrical properties with several different physical domains. In particular MEMS devices exploit a miniaturized movable structure whose movement or position can interact with electrostatic, thermal, magnetic, fluidics, electromagnetic signals.[2] MEMS resonator has ability to replace quartz crystal resonator, SAW filter. They provide a promising alternative to traditional electronic components especially for RF devices (e.g. mixers, tunable capacitors, inductors, switches, oscillators) [3]. The device which provides oscillations within a particular frequency band known as resonator.  II. BASIC CLAMPED FREE BEAM RESONATOR STRUCTURE  Figure 1.  Clamped Free Beam Resonator. [3] III. OPERATION OF RESONATOR Fig. 2 shows the configuration of Clamped free beam resonator, Fig. 3 and Table I shows the design model and design parameters of MEMS poly-silicon resonator. The principle of operation of MEMS resonator based upon a two electrode in which the moving and fixed part forms two electrodes of capacitors. Anchor is used to fixed resonators one end.By applying DC voltage to the anchor and an AC voltage    to the excitation electrode, the microstructure being driven into resonance. The DC voltage is used to generate the electrostatic force this will bend the beam but it will vibrate only if this force vibrates and this can be done using AC voltage.   Figure 2.  Electrical setup for Clamped-Free beam resonator. [3]   Figure 3.  Design Model             International Journal on Recent and Innovation Trends in Computing and Communication                                                   ISSN: 2321-8169 Volume: 3 Issue: 6                                                                                                                                                                        4072 - 4074 ______________________________________________________________________________________________  4073 IJRITCC | June 2015, Available @ http://www.ijritcc.org                                                                 _______________________________________________________________________________________ TABLE I.   DESIGN PARAMETERS OF MEMS POLYSILICON RESONATOR Input Parameter Value Unit Beam length, L 15 µm Beam width, W 1 µm Beam thickness, t 1 µm Anchor length 2 µm Anchor width 5 µm Anchor thickness 1 µm Electrode to resonator gap 0.3 µm Driving, Sensing Electrode length  1.4 µm Driving, Sensing Electrode width 4 µm Driving, Sensing Electrode thickness 1 µm  Fig. 3 and Table I shows the design model of clamped free beam resonator and design parameters of MEMS poly-silicon resonator. As the motional resistance has power handling capability, minimum electrode to resonator gap is required to get reduced equivalent motional resistance and reduced anchor losses, but there is a limit on reducing the gap between electrode and resonator as it decides the maximum displacement amplitude. For high resonance frequency the mass of resonator required is less, but In Fig. 3 design model the mass is applied at the end of cantilever beam for efficient transduction, as reduction in resonance frequency is negligible. By using driving (input) and sensing (output) electrode a mask is applied on cantilever beam.  TABLE II.  MATERIAL PROPERTIES OF POLY-SILICON  TABLE III.  MATERIAL PROPERTIES OF AIR  IV. EIGEN FREQUENCY ANALYSIS  Eigen Frequency: The term resonator is most often used for a homogeneous object in which vibrations travel as waves at an approximately constant velocity bouncing back & forth between the sides of the resonator. The resonator can have millions of resonant frequencies, although only a few may be used in practical resonators. The resonant frequencies of resonators called normal modes are equally spaced multiples [harmonics] of a lowest frequency called the fundamental frequency.   Where, F-Frequency βnl- Arbitrary Constant     E-Young Modulus I- Inertia ρ –Density A-Area of beam L-Length of beam TABLE IV.  VALUE OF (ΒNL)² Beam  Configuration (βnl)² Fundamental (βnl)² Second mode (βnl)² Third mode Cantilever 3.52 22.0 61.7 TABLE V.  FREQUENCIES OF DIFFERENT MODE  Frequency     Analytical      Simulation Fundamental 5.96 MHZ 5.46MHZ          2nd Mode            37MHZ            34MHZ          3rd Mode 101 MHZ     93.48MHZ  V. ELECTROSTATIC (AC ANALYSIS) A.  Resonance Frequency Frequency at which the response amplitude is a relative maximum known as resonant frequency. Resonance occurs when a system is able to store & easily transfer energy between two or more different storage modes. However there are some losses from cycle to cycle called ‘damping’. When damping is small the resonant frequency is approximately equal to natural frequency of the system, which is a frequency of unforced  Vibration.                           λ=LLc Where, λ- Damping coefficient Lc- Length of beam overlapped by electrode L-Length of beam  B. Pull-in voltage Since the beam vibrates either in vertical and lateral displacement, it may touch the electrode or substrate when it reaches the maximum DC voltage. In this work, we are interested in the lateral movement of the beam during International Journal on Recent and Innovation Trends in Computing and Communication                                                   ISSN: 2321-8169 Volume: 3 Issue: 6                                                                                                                                                                        4072 - 4074 ______________________________________________________________________________________________  4074 IJRITCC | June 2015, Available @ http://www.ijritcc.org                                                                 _______________________________________________________________________________________ vibration. The pull-in voltage is as when the lateral movement of beam reaches beyond the gap distance of 0.3μm. This indicates that the beam is already touching the electrode [3].   Where, Vp- Pull in voltage k- Stiff constant d- Electrode to resonator gap Aeff- Effective electrode area  0-Absolute permittivity of air C. DC Supply Voltage (Vin)   Where, Vin- DC voltage F-Force of actuation  d-Electrode to resonator gap Є-Relative permittivity Є0-Absolute permittivity Aeff- Effective area of beam       As depicted in Fig.4 Clamped free beam shows the first mode resonance frequency at 5.46 MHZ and the displacement at 4.40nm.   VI. CONCLUSION  The Clamped free beam was found to have a resonance frequency of 5.46 MHz. This was built using poly-silicon. The required DC voltage is 4V. This resonator can be used as a band-pass filter in RF-transceiver.   REFERENCES [1] G.K. Ananthasuresh, K.J.Vinoy, S.Gopalakrishnan, K.N. Bhat, V.K.Atre ”Micro and Smart Systems”Copyright 2010 by Wiley india Pvt.Ltd.    [2] Dr. Benno Margesin, PhD Dissertation “Novel Design Solutions for High Reliability RF MEMS Switches” Francesco Solazzi, April 2010 [3] A. Zainuddin, Jamilah Karim, A. Nordin,M. Pandian, Sheroz K.“Design and Simulation of Clamped-Clamped and Clamped-Free Resonators”[©2013 IEEE 5th Asia Symposium on Quality Electronic Design] [4] Joydeep Basu, Tarun Kanti Bhattacharyya “Microelectromechanical Resonators for Radio Frequency Communication Applications”, Review Paper Microsystem Technologies, Oct 2011, vol. 17(10–11), pp. 1557–1580, and is available at springerlink © Springer-Verlag 2011. [5] Yongmei Zhao, lin Ningt, Guosheng Sunl, Xingfang Liu, Liang Wang , Gang Ji, Lei Wang, Wanshun Zhao “Simulation and fabrication of the SiC-based clamped-clamped filter” ©2008 IEEE [6] Deepak Kumar,A.Vimala Juliet “Design, Electrostatic and Eigen Frequency Analysis of Fixed-Fixed Beam MEMS Resonator”IOSR-JECE Apr2013.  [7] Thesis Joanna Kiljan,“Embedded Charge for Microswitch Applications”  Department of  Microelectronics Engineering, College of Engineering Rochester Institute of Technology, Rochester NEW YORK December,    2004 [8] Abhijeet V. Kshirsagar, S.P.DuttaGupta, S.A.Gangal, “Design of MEMS Cantilever-Hand Calculation’ Sensors and Transducers-Journal,Vol.91,Issue 4,April 2008,pp 55-69 [9] Ming-Huang Li, Wen- Chien Chen,Sheng-Shian Li ‘Mechanically Coupled CMOS-MEMS Free-Free Beam Resonator Arrays With Enhanced Power Handling Capability”2012 IEEE     Figure 4.  Total displacement and resonance frequency result for Clamped free beam with 4V DC voltage     Applied VDC  Value  Calculated VDC Value 4V 3.82V 

Design & Analysis of Clamped Free MEMS Resonator

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Design & Analysis of Clamped Free MEMS Resonator

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International Journal on Recent and Innovation Trends in Computing and Communication