Process Development of GaAs Based RF MEMS Switch

P.Suryanarayana, A.A.Naik, Ch.Sridar, V.S.N. Murthy, J.Ravikiran, M.Renju, Sandeep, S.D. Prasad,

A.V.S.K. Rao, A.Mangatayaru*, S.K. Koul**, and R.Muralidharan.

GAETEC, Vignyana Kancha, Hyderabad-69, MMIC Group, SSPL, DELHI, *RCI, Vignyana Kancha Post, Hyderabad-500068, **IIT, DELHI; psn_nlg@yahoo.com; 91-40-24589206

Keywords: RF MEMS, Sacrificial Layer, Stress in metal beam, On/Off capacitance

ABSTRACT

Processes for realizing GaAs based RF MEMS are described in detail. Polyimide, OIR 17 PR and polymethylglutarimide (PMGI) were used as sacrificial layers. SEM investigations were carried out on MEMS structures. The Beam profiles were mapped with Optical Profilometer(OP). The OP data were correlated with SEM data. PMGI is found to have good process compatibility and is easy to remove. Metals like Au, Ti/Au, Au/Ti/Au and NiCr/Au were studied as beam metal. E-beam deposited 8000 oA Au metal beams and optimized Ti/Au stack exhibited good beam structures. For a 1000 oA field nitride, electrical C-V data of various RF MEMS gave OFF capacitance of around 0.2pf and ON capacitance of up to 2 pf which is dependent on beam metal width. The switching voltage of Meander structure is lower than the plane or perforated beams.. RF measurements were carried out up to 40 GHz. In some structures RF measurements show less than 0.4 dB insertion loss and more than 25dB isolation.

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