Abstract
An important step in the MEMS switch fabrication is the formation of a suspended micron-sized beam. Typically, the beam is made of gold due to its high electrical conductivity and chemical inertness. However, the fabrication process is complicated by poor suitability of Au for chemical etching and deformation of the beam under residual mechanical stress. An additional disadvantage is a high price of gold. Aluminium and its alloys are considered as a promising alternative. In this work, the magnetron-sputtered Al 99.99%, Al–1% Si and Al–1.5% Ti are tested as structural materials for a MEMS switch. We fabricate 1 μm thick beams and investigate surface morphology, electrical resistivity and mechanical properties. Single-layer films of Al 99.99% and Al–1% Si have coarse-grained microstructure with the root-mean-square roughness higher than 50 nm. The multi-step deposition reduces this value to 15 nm without significant deterioration of the resistivity and Young’s modulus. However, multilayer films of Al 99.99% have interlayer voids, which may degrade the switch reliability. Al–1.5% Ti provides much smoother and fine-grained film with plain sidewalls, which results in a higher quality factor of the beams. But this alloy has three times higher electrical resistivity than pure Al. Therefore, fabrication of the beam and transmission line from Al–1.5% Ti will increase insertion loss of the switch. A four-layer film of Al–1% Si is more preferable, since it also has fine microstructure and does not contain interlayer voids, but is close to pure aluminium in terms of resistivity.
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Bansal D, Bajpai A, Kumar P, Kaur M, Kumar A, Chandran A, Rangra K (2017) Low voltage driven RF MEMS capacitive switch using reinforcement for reduced buckling. J Micromech Microeng 27:024001. https://doi.org/10.1088/1361-6439/aa4ea1
Barron LW, Neidrich J, Kurinec SK (2007) Optical, electrical, and structural properties of sputtered aluminum alloy thin films with copper, titanium and chromium additions. Thin Solid Films 515:3363–3372. https://doi.org/10.1016/j.tsf.2006.09.030
Blom FR, Bouwstra S, Elwenspoek M, Fluitman JHJ (1992) Dependence of the quality factor of micromachined silicon beam resonators on pressure and geometry. J Vac Sci Technol B 10:19–26. https://doi.org/10.1116/1.586300
Boisen A, Dohn S, Keller SS, Schmid S, Tenje M (2011) Cantilever-like micromechanical sensors. Rep Prog Phys 74:036101. https://doi.org/10.1088/0034-4885/74/3/036101
Carty E, Fitzgerald P, McDaid P, Stenson B, Goggin R (2016) Development of a DC to K-band ultra long on-life RF MEMS switch with integrated driver circuitry. In: 2016 46th European microwave conference (EuMC). https://doi.org/10.1109/EuMC.2016.7824608
Dai C-L, Chen Y-L (2007) Modeling and manufacturing of micromechanical RF switch with inductors. Sensors 7:2660–2670. https://doi.org/10.3390/s7112670
Daneshmand M, Mansour RR (2011) RF MEMS satellite switch matrices. IEEE Microw Mag 12:92–109. https://doi.org/10.1109/MMM.2011.941417
Dirks AG, Tien T, Towner JM (1986) AlTi and AlTiSi thin alloy films. J Appl Phys 59:2010–2014. https://doi.org/10.1063/1.336381
Dutta S, Imran M, Pandey A, Saha T, Yadav I, Pal R, Jain KK, Chatterjee R (2014) Estimation of bending of micromachined gold cantilever due to residual stress. J Mater Sci Mater Electron 25:382–389. https://doi.org/10.1007/s10854-013-1598-z
Eisenmenger-Sittner C (2001) Surface evolution of polycrystalline Al films deposited on amorphous substrates at elevated temperatures. J Appl Phys 89:6085–6091. https://doi.org/10.1063/1.1368864
Flinn PA, Gardner DS, Nix WD (1987) Measurement and interpretation of stress in aluminum-based metallization as a function of thermal history. IEEE Trans Electron Devices 34:689–699. https://doi.org/10.1109/T-ED.1987.22981
Green TA (2014) Gold etching for microfabrication. Gold Bull 47:205–216. https://doi.org/10.1007/s13404-014-0143-z
Guo FM, Zhu ZQ, Long YF, Wang WM, Zhu SZ, Lai ZS, Li N, Yang GQ, Lu W (2003) Study on low voltage actuated MEMS rf capacitive switches. Sens Actuators A 108:128–133. https://doi.org/10.1016/S0924-4247(03)00372-8
Gupta A, Barron L, Brainin M, Lee J-B (2014) Reduction of out-of-plane warpage in surface micromachined beams using corrugation. J Micromech Microeng 24:065023. https://doi.org/10.1088/0960-1317/24/6/065023
Hao Z, Erbil A, Ayazi F (2003) An analytical model for support loss in micromachined beam resonators with in-plane flexural vibrations. Sens Actuators A 109:156–164. https://doi.org/10.1016/j.sna.2003.09.037
Heredia J, Ribó M, Pradell L, Wipf ST, Göritz A, Wietstruck M, Wipf C, Kaynak M (2019) A 125-143-GHz frequency-reconfigurable BiCMOS compact LNA using a single RF-MEMS switch. IEEE Microw Compon Lett 29:339–341. https://doi.org/10.1109/LMWC.2019.2906595
Hodge TC, Bidstrup-Allen SA, Kohl PA (1997) Stresses in thin film metallization. IEEE Trans Compon Packag Manuf Technol A 20:241–250. https://doi.org/10.1109/95.588580
Kal S, Bagolini A, Margesin B, Zen M (2006) Stress and resistivity analysis of electrodeposited gold films for MEMS application. Microelectron J 37:1329–1334. https://doi.org/10.1016/j.mejo.2006.07.006
Kim D-K, Heiland B, Nix WD, Arzt E, Deal MD, Plummer JD (2000) Microstructure of thermal hillocks on blanket Al thin films. Thin Solid Films 371:278–282. https://doi.org/10.1016/S0040-6090(00)00971-8
Lee H-J, Cornella G, Bravman JC (2000) Stress relaxation of free-standing aluminum beams for microelectromechanical systems applications. Appl Phys Lett 76:3415–3417. https://doi.org/10.1063/1.126664
Lide DR (2009) CRC handbook of chemistry and physics, 90th edn. CRC Press/Taylor and Francis, Boca Raton
Lifshitz R, Roukes ML (2000) Thermoelastic damping in micro- and nanomechanical systems. Phys Rev B 61:5600–5609. https://doi.org/10.1103/PhysRevB.61.5600
Lita AE, Sanchez JE Jr (1999) Characterization of surface structure in sputtered Al films: correlation to microstructure evolution. J Appl Phys 85:876–882. https://doi.org/10.1063/1.369206
Ma L-Y, Soin N, Daut MHM, Hatta SFWM (2019) Comprehensive study on RF-MEMS switches used for 5G scenario. IEEE Access 7:107506–107522. https://doi.org/10.1109/ACCESS.2019.2932800
Maciel J, Majumder S, Lampen J, Guthy C (2012) Rugged and reliable ohmic MEMS switches. In: 2012 IEEE/MTT-S international microwave symposium digest. https://doi.org/10.1109/MWSYM.2012.6258368
Olefjord I, Nylund A (1994) Surface analysis of oxidized aluminium. 2. Oxidation of aluminium in dry and humid atmosphere studied by ESCA, SEM, SAM and EDX. Surf Interface Anal 21:290–297. https://doi.org/10.1002/sia.740210505
Park J-H, Myung MS, Kim Y-J (2008) Tensile and high cycle fatigue test of Al–3% Ti thin films. Sens Actuators A 147:561–569. https://doi.org/10.1016/j.sna.2008.06.003
Patel CD, Rebeiz GM (2011) RF MEMS metal-contact switches with mN-contact and restoring forces and low process sensitivity. IEEE Trans Microw Theory Technol 59:1230–1237. https://doi.org/10.1109/TMTT.2010.2097693
Rao KR, Kumar PA, Guha K, Sailaja BVS, Vineetha KV, Baishnab KL, Sravani KG (2018) Design and simulation of fixed-fixed flexure type RF MEMS switch for reconfigurable antenna. Microsyst Technol. https://doi.org/10.1007/s00542-018-3983-2
Rebeiz GM (2003) RF MEMS: theory, design, and technology. Wiley, New Jersey
Reines I, Pillans B, Rebeiz GM (2011) Thin-film aluminum RF MEMS switched capacitors with stress tolerance and temperature stability. J Microelectromech Syst 20:193–203. https://doi.org/10.1109/JMEMS.2010.2090505
Sambles JR (1983) The resistivity of thin metal films—some critical remarks. Thin Solid Films 106:321–331. https://doi.org/10.1016/0040-6090(83)90344-9
Shaffir E, Riess I, Kaplan WD (2009) The mechanism of initial de-wetting and detachment of thin Au films on YSZ. Acta Mater 57:248–256. https://doi.org/10.1016/j.actamat.2008.09.004
Shekhar S, Vinoy KJ, Ananthasuresh GK (2018) Low-voltage high-reliability MEMS switch for millimeter wave 5G applications. J Micromech Microeng 28:075012. https://doi.org/10.1088/1361-6439/aaba3e
Toghan A, Khodari M, Steinbach F, Imbihl R (2011) Microstructure of thin film platinum electrodes on yttrium stabilized zirconia prepared by sputter deposition. Thin Solid Films 519:8139–8143. https://doi.org/10.1016/j.tsf.2011.06.018
Uvarov IV, Kupriyanov AN (2018) Stiction-protected MEMS switch with low actuation voltage. Microsyst Technol 25:3243–3251. https://doi.org/10.1007/s00542-018-4188-4
Uvarov IV, Naumov VV, Amirov II (2012) Resonance properties of multilayer metallic nanocantilevers. Proc SPIE 8700:87000S-1. https://doi.org/10.1117/12.2016751
van Gils M, Bielen J, McDonald G (2007) Evaluation of creep in RF MEMS devices. In: 2007 international conference on thermal, mechanical and multi-physics simulation experiments in microelectronics and micro-systems (EuroSime 2007). https://doi.org/10.1109/ESIME.2007.360033
Verger A, Pothier A, Guines C, Crunteanu A, Blondy P, Orlianges J-C, Dhennin J, Broue A, Courtade F, Vendier O (2010) Sub-hundred nanosecond electrostatic actuated RF MEMS switched capacitors. J Micromech Microeng 20:064011. https://doi.org/10.1088/0960-1317/20/6/064011
Wipf C, Sorge R, Göritz A, Wipf ST, Scheit A, Kissinger D, Kaynak M (2018) High voltage LDMOS inverter for on-chip RF-MEMS actuation. In: 2018 IEEE 18th topical meeting on silicon monolithic integrated circuits in RF systems (SiRF). https://doi.org/10.1109/SIRF.2018.8304226
Xu Y, Tian Y, Zhang B, Duan J, Yan L (2018) A novel RF MEMS switch on frequency reconfigurable antenna application. Microsyst Technol 24:3833–3841. https://doi.org/10.1007/s00542-018-3863-9
Yang JJ, Zhu HL, Wan Q, Yang YY, Liao JL, Liu N, Wang LM (2015) Suppression of surface roughening kinetics of homogenously multilayered W films. J Appl Phys 118:175301. https://doi.org/10.1063/1.4935136
Yasumura KY, Stowe TD, Chow EM, Pfafman T, Kenny TW, Stipe BC, Rugar D (2000) Quality factors in micron- and submicron-thick cantilevers. J Microelectromech Syst 9:117–125. https://doi.org/10.1109/84.825786
Ye H (2003) An overview of the development of Al–Si alloy based material for engine applications. J Mater Eng Perform 12:288–297. https://doi.org/10.1361/105994903770343132
Zareie H, Rebeiz GM (2014) Compact high-power SPST and SP4T RF MEMS metal-contact switches. IEEE Trans Microw Theory Technol 62:297–305. https://doi.org/10.1109/TMTT.2013.2296749
Zhou W, Sheng W, Cui J, Han Y, Ma X, Zhang R (2019) SR-Crossbar topology for large-scale RF MEMS switch matrices. IET Microw Antennas Propag 13:231–238. https://doi.org/10.1049/iet-map.2018.5317
Acknowledgements
This work was supported by Program No. 0066-2019-0002 of the Ministry of Science and Higher Education of Russia for Valiev Institute of Physics and Technology of RAS and performed using the equipment of Facilities Sharing Centre “Diagnostics of Micro- and Nanostructures”.
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Uvarov, I.V., Selyukov, R.V. & Naumov, V.V. Testing of aluminium and its alloys as structural materials for a MEMS switch. Microsyst Technol 26, 1971–1980 (2020). https://doi.org/10.1007/s00542-020-04748-2
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DOI: https://doi.org/10.1007/s00542-020-04748-2