Abstract
Radio frequency micro electro-mechanical systems (RF MEMS) vertical cantilever variable capacitors fabricated using deep X-ray lithography and electroplating are presented. Polymethylmethacrylate (PMMA) layers of 100 μm and 150 μm have been patterned and electroplated with 70 μm and 100 μm thick nickel. A 3 μm thick titanium layer was used as plating base as well as etch time-controlled sacrificial layer for the release of the cantilever beam. The parallel plate layout includes narrow gaps and cantilever beams with an aspect ratio in nickel of up to 60 for 1 mm long features. Auxiliary structures support the beams and gaps during the processing. Room temperature electroplating significantly reduces the risk of deformations compared to the standard process temperature of 52°C. The capacitors operate in the 1–5 GHz range, and demonstrate good RF performance, with quality factors on the order of 170 at 1 GHz for a 1 pF capacitance.
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Achenbach S, Pantenburg FJ, Mohr J (2000) Optimization of the process conditions for the fabrication of microstructures by ultra deep X-ray lithography (UDXRL). Forschungszentrum Karlsruhe, FZKA 6576, Karlsruhe
Aigeldinger G, Ceremuga JT, Krenz KD (2004) In-situ metrology of swelling effects on critical dimensions in LIGA PMMA molds. In: Proceedings ASPE 2004 annual meeting, Orlando
Borwick III RL, Stupar PA, DeNatale J, Anderson R, Tsai C, Garrett K, Erlandson R (2003) A high Q, large tuning range MEMS capacitor for RF filter systems. Sens Actuators A Phys 103:33–41
Dec A, Suyama K (1998) Micromachined electro-mechanically tunable capacitors and their applications to RF IC’s. IEEE Trans Microw Theory Tech 46:2587–2596
Dussopt L, Rebeiz GM (2002) High-Q millimeter-wave MEMS varactors: extended tuning range and discrete-position designs. In: IEEE MTT-S international microwave symposium digest, pp 1205–1208
Feng Z, Zhang H, Gupta KC, Zhang W, Bright VM, Lee YC (2001) MEMS-based series and shunt variable capacitors for microwave and millimeter-wave frequencies. Sens Actuators A Phys 91:256–265
Haluzan DT (2004) Microwave LIGA-MEMS variable capacitors. MSc Thesis, University of Saskatchewan
Haluzan DT, Klymyshyn DM (2004) High-Q LIGA-MEMS vertical cantilever variable capacitors for upper microwave frequencies. Microw Opt Technol Lett 42:507–511
Jou J, Liu C, Schutt-Aine J (2001) Development of a wide tuning range two-parallel-plate tunable capacitor for integrated wireless communication systems. Int J RF Microw Comput Aided Design 11:322–329
Richards RJ, De Los Santos HJ (2001) MEMS for RF/μWave wireless applic.: the next wave. Microwave J 44:20–41
Ruzzu A, Matthis B (2002) Swelling of PMMA-structures in aqueous solutions and room temperature Ni-electroforming. Microsyst Technol 8(2–3):116 – 119
Yao J, Park S, DeNatale J (1998) High tuning ratio MEMS based tunable capacitors for RF communications applications. In: Solid state sensor and actuator workshop, Hilton Head, pp 124–127
Young DJ, Boser BE (1996) A micromachined variable capacitor for monolithic low-noise VCOs. In: Solid state sensor and actuator workshop, Hilton Head, pp 86–89
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Achenbach, S., Klymyshyn, D., Haluzan, D. et al. Fabrication of RF MEMS variable capacitors by deep X-ray lithography and electroplating. Microsyst Technol 13, 343–347 (2007). https://doi.org/10.1007/s00542-006-0213-0
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DOI: https://doi.org/10.1007/s00542-006-0213-0