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High quality factor RF MEMS tunable capacitor

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Abstract

This paper presents the design of a tunable capacitor that integrates two vertical comb-drive tunable capacitors and a parallel plate tunable capacitor. The parallel plate tunable capacitor is in the middle of the comb-drive tunable capacitors. The vertical comb-drive part has sets of fixed and moving fingers while the parallel plate has fixed and moving plates. The capacitor is fabricated using the MetalMUMPs microfabrication process, which has only one thick structural layer i.e. metal (20 μm nickel and 0.5 μm gold). The nickel of the metal layer is subject to residual stress gradients along its thickness. After release of the metal layer, the stress gradients bend the curve-up beams to raise the moving fingers and the moving plate of the capacitor above the substrate and the fixed plate. Hence, one structural layer (i.e. the metal) is used to form the moving and the fixed comb fingers without requiring two structural layers. Vertical comb-driven tunable capacitors offer high capacitance density when a large number of fingers with narrow gap are used. Therefore, high capacitance ratio and high quality factors can be achieved by using vertical comb-drives with in a relatively small device area compared to lateral comb-drives. The parallel plate driving part increases the displacement and capacitance ratio while reducing the actuation voltage required for driving the capacitor. The quality factor and tuning ratio of the fabricated tunable capacitor are 118.5 and 101% at 0.8 GHz; respectively at a driving voltage of 100 V. Based on the experimental results of the fabricated tunable capacitor, an optimized design is presented for both high tuning ratio and high quality factor. The tuning ratio of the optimized capacitor is found to be 143.1% at a “pull-in” displacement of 9.5 µm and a “pull-in” voltage of 90 V. The quality factors of the optimized capacitor are 520 at 0 V and 363.5 at 90 V, respectively at 0.8 GHz. The tunable capacitor achieves a displacement of more than one-half of the gap between the parallel plates without “pull-in” effect.

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References

  • A Coupled Electromechanical Simulator CoventorWare ™, 2010, Cary NC, Coventor Inc. http://www.coventor.com/products/coventorware/

  • Auciello O, Saha S, Kaufman DY, Streiffer SK, Fan W, Kabius B, Im J, Baumann P (2004) Science and technology of high dielectric constant thin films and materials integration for application to high frequency devices. J Electroceram 12(1/2):119–131

    Article  Google Scholar 

  • Ayguavives T, Tombak A, Maria J-P, Stauf GT, Ragaglia C, Roeder J, Mortazawi A, Kingon AI (2000) Physical properties of (Ba, Sr)TiO3 thin films used for integrated capacitors in microwave applications. Proc IEEE ISAF 1:365–368

    Google Scholar 

  • Bakri-Kassem M, Mansour RR (2004) Two movable-plate nitride-loaded MEMS variable capacitor. IEEE Trans Microw Theory Tech 52(3):831–837

    Article  Google Scholar 

  • Borwick RL et al (2003a) A high Q, large tuning MEMS capacitor for RF Filter systems. Sens Actuators A103:33–41

    Article  Google Scholar 

  • Borwick RL et al (2003b) Variable MEMS capacitors implemented into RF filter systems. IEEE Trans Microw Theory Technol 51:315–319

    Article  Google Scholar 

  • Cowen A, Mahadevan R, Johnson S, Hardy B (2002) Metal-MUMPs Design Handbook, Revision 3.0, MEMSCAP Inc. http://www.memscap.com/mumps/documents/MetalMUMPs.DR.2.2.pdf. Accessed 01 June 2011

  • Dec A, Suyama K (1998) RF Micromachined varactors with wide tuning range. In: IEEE Radio Frequency Integrated Circuits (RFIC) Symposium, 1998 7–9 June, pp 309–312

  • Ehmke J, Brank J, Malczewski A, Pillans B, Eshelman S, Yao J, Goldsmith C (2000) RF MEMS devices: a brave new world for RF technology. In: IEEE Emerging Technologies Symposium 2000

  • Grichener A, Rebeiz GM (2010) High-reliability RF-MEMS switched capacitors with digital and analog tuning characteristics. IEEE Trans Microw Theory Techn 58 (10), Article. No. 5575376, pp 2692–2701

  • Grichener A, Mercier D, Rebeiz GM (2006) High-power, high-reliability, high-Q switched RF MEMS capacitors. In: International Microwave Symposium Digest, pp 31–34

  • Hailu Z (2014) Novel RF MEMS Tunable Capacitors, Ph.D. thesis

  • Hailu Z, He S, Mrad RB (2014) A novel vertical comb-drive electrostatic actuator using a one layer process. J Micromech Microeng 24 (11):115016, pp 1–11

  • Hailu Z, He S, Mrad RB (2016) Hybrid Micro electrostatic actuator. Microsyst Technol 22:319–327

    Article  Google Scholar 

  • He S, Chang JS, Li L, Ho H (2009) Characterization of Young’s modulus and residual stress gradient of MetalMUMPs electroplated nickel film. Sens Actuators 154(1):149–156

    Article  Google Scholar 

  • Hoivik N, Michalicek MA, Lee YC, Gupta KC, Bright VM (2001) Digitally controllable variable high-Q MEMS capacitor for RF applications. In: IEEE MTT-S International Microwave Symposium Digest, Phoenix, AZ, May 2001, pp 2115–2118

  • Ionis GV, Dec A, Suyaman K (2002) Differential multi-finger MEMS tunable capacitors for RF Integrated Circuits. In: IEEE MTT-S International Microwave Symposium Digest, vol 1, pp 345–348

  • Jakoby R, Scheele P, Muller S, Weil C (2004) Nonlinear dielectrics for tunable microwave components. In: Proc. IEEE Int. Conf. Microw., Radar Wireless Commun., May 2004, vol 2, pp 369–378

  • Jung S et al (2001) Micromachined frequency variable impedance tuners using resonant unit cells. In: IEEE MTT-S International Microwave Symposium Digest, Phoenix, AZ, May 2001, pp 333–336

  • Lee H, Yoon YJ, Choi D-H, Yoon J-B (2008) High-Q, tunable gap MEMS variable capacitor actuated with an electrically floating plate. In: Proc. IEEE Int. Conf. Micro Electro Mech. Syst., pp 180–183

  • Mahameed R, El-Tanani MA, Rebeiz GM (2010) A zipper RF MEMS tunable capacitor with interdigitated RF and actuation electrodes. J Micromech Microeng 20(3):035014

    Article  Google Scholar 

  • Nguyen HD, Hah D, Patterson PR, Chao R, Piyawattanametha W, Lau EK, Wu MCM (2004) Angular vertical comb-driven tunable capacitor with high-tuning capabilities. J Microelectromech Syst 13(3):406–413

    Article  Google Scholar 

  • Pervez NK, Hansen PJ, York R (2004) Optimization of high tunability BST thin films grown by RF magnetron sputtering. In: Proc. IEEE UFFC50th Anniversary Conf., Aug. 2004, pp. 278–280

  • Pozar DM (2005) Microwave engineering, 4th edn. Wiley and Sons Inc, New York

    Google Scholar 

  • Rais-Zadeh M, Ayazi F (2007) High-Q tunable silver capacitors for RFIC’s. In: Topical Meeting on Silicon Monolithic Integrated Circuits in RF Systems, 2007, vol no., pp 169–172, 10–12 January 2007

  • Rebeiz GM (2003) RF MEMS—theory, design, and technology. Wiley and Sons Inc, New York

    Google Scholar 

  • Rebeiz GM et al (2009) Tuning into RF MEMS, IEEE Microwave magazine, October 2009, pp 55–72

  • Rijks et al (2004) MEMS Tunable Capacitors and Switches for RF Applications. In: Proceedings of 24th International Conference on Microelectronics, 16–19 May 2004, Serbia and Montenegro, pp 49–56

  • Schafranek R, Giere A, Balogh AG, Enza T, Zheng Y, Scheele P, Jakoby R, Klein A (2009) Influence of sputter deposition parameters on the properties of tunable barium strontium titanate thin films for microwave applications. J Eur Ceram Soc 29(8):1433–1442

    Article  Google Scholar 

  • Seok S, Choi W, Chun K (2002) A Novel linearly tunable MEMS variable capacitor. J Micromech Microeng 12:82–86

    Article  Google Scholar 

  • Sze SM, Ng KK (2005) Physics of semiconductor devices, 3rd edn. Wiley-Interscience, New York

    Google Scholar 

  • Vicki Chen L-Y, Forse R, Chase D, York RA (2004) Analogue tunable matching network using integrated thin-film BST capacitors. In: Proc.IEEE MTT-S Int. Microw. Symp. Exhib., June 2004, vol 1, pp 261–264

  • Vorobiev A, Rundqvist P, Khamchane K, Gevorgian S (2005) Microwave loss mechanisms in Ba0.25Sr0.75TiO 3 films. Mater Sci Eng B Solid State Mater Adv Technol 118(1–3):214–218

    Article  Google Scholar 

  • Yao JJ (2000) RF MEMS from a device perspective. J Micromech Microeng Struct Devices Syst IO Part 4:R9–R38

    Article  Google Scholar 

  • Yoon JB, Nguyen CTC (2000) A high-Q tunable micromechanical capacitor with movable dielectric for RF applications. In: Technical Digest, IEEE Int. Electron Devices Meeting, San Francisco, California, Dec. 11–13, pp 489–492

  • Young DJ, Boser BE (1997) A micro-machined based RF low-noise voltage-controlled oscillator. In: Proceedings of the IEEE 1997 Custom Integrated Circuits Conference, June 1996, pp 431–434

  • Zou J et al (2000) Development of wide tuning range MEMS tunable capacitor for wireless communication systems. In: Technical Digest, International Electron Devices Meeting, San Francisco, CA, USA, pp 403–406

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Acknowledgements

The author would like to thank the Canadian Microsystems Inc. for fabricating and testing the micro-chips. The work presented in this paper is solely based on the thesis work of the author.

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  1. Mechanical and Industrial Engineering, Ryerson University, Toronto, ON, Canada

    Zewdu Hailu

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  1. Zewdu Hailu
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Correspondence to Zewdu Hailu.

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Hailu, Z. High quality factor RF MEMS tunable capacitor. Microsyst Technol 23, 3719–3730 (2017). https://doi.org/10.1007/s00542-016-3181-z

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  • DOI: https://doi.org/10.1007/s00542-016-3181-z

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