Low-temperature co-fired ceramic (LTCC) enables development and testing of critical elements on microsystem boards as well as nonmicroelectronic meso-scale applications. We describe silicon-based microelectromechanical systems packaging and LTCC meso-scale applications. Microfluidic interposers permit rapid testing of varied silicon designs. The application of LTCC to micro-high-performance liquid chromatography (m-HPLC) demonstrates performance advantages at very high pressures. At intermediate pressures, a ceramic thermal cell lyser has lysed bacteria spores without damaging the proteins. The stability and sensitivity of LTCC/chemiresistor smart channels are comparable to the performance of silicon-based chemiresistors. A variant of the use of sacrificial volume materials has created channels, suspended thick films, cavities, and techniques for pressure and flow sensing. We report on inductors, diaphragms, cantilevers, antennae, switch structures, and thermal sensors suspended in air. The development of ''functional-as-released'' moving parts has resulted in wheels, impellers, tethered plates, and related new LTCC mechanical roles for actuation and sensing. High-temperature metal-to-LTCC joining has been developed with metal thin films for the strong, hermetic interfaces necessary for pins, leads, and tubes.

Contact resistance measurements are reported for radio frequency microelectromechanical system switches operating in an ultrahigh vacuum system equipped with in situ oxygen plasma cleaning capabilities. Ru-based contacts were prepared by means of standard sputtering techniques, sputtering followed by postdeposition oxidation, ͑surface RuO 2 ͒ or reactive sputtering in the presence of oxygen ͑bulk RuO 2 ͒. In situ oxygen plasma cleaning lowered the resistance of Ru contacts by two or more orders of magnitude but not lower than Au contacts, irrespective of whether the Au contacts were cleaned. The time dependence of the resistance was fit to power law extrapolations to infer contact creep properties and resistance values at t = ϱ. Time-dependent creep properties of mixed Au-Ru contacts were observed to be similar to those of Au-Au contacts, while the absolute value of the resistance of such contacts was more comparable to Ru-Ru contacts. Prior to, and for short oxygen plasma exposure times, bulk RuO 2 resistance values exhibited much larger variations than values measured for surface RuO 2 . For O 2 plasma exposure times exceeding about 5 min, the bulk and surface RuO 2 resistance values converged, at both t = 0 and t = ϱ, with the t = ϱ values falling within experimental error of theoretical values predicted for ideal surfaces. The data strongly support prior reports in the surface science literature of oxygen plasma induced thickening of oxide layers present on Ru surfaces. In addition, they demonstrate that vacuum alone is insufficient to remove contaminants from the contact surfaces and/or prevent such contaminants from reforming after oxygen plasma exposure.

We present improvements in RF microelectromechanical switch design and fabrication that demonstrated improved lifetimes in cycled switches. First, implementation of RuO 2 -Au contact metallurgy into an existing design showed improved switch lifetime over switches with Pt-Au, Ir-Au, and Au-Au contacts. Second, the switch design was changed to reduce impact upon switch closure, and the fabrication process was changed to avoid the use of polymer sacrificial materials while including the RuO 2 -Au contact metallurgy. Switches with the new design were cycled to 10 billion cycles with a resistance less than 4 Ω, an insertion loss of 0.4 dB, and an isolation of 28.0 dB at 10 GHz. We propose that the catalytic behavior of the RuO 2 film prevents or delays the failure of the switches due to accumulation of carbon at the contacts. Additionally, the reduced impact upon closure prevented significant contact evolution during cycling.

Abstract-A switched Ku-band filter bank has been developed using two single-pole triple-throw (SP3T) microelectromechanical systems (MEMS) switching networks, and three fixed three-pole end-coupled bandpass filters. A tuning range of 17.7% from 14.9 to 17.8 GHz was achieved with a fractional bandwidth of 7.7 2.9%, and mid-band insertion loss ranging from 1.7 to 2.0 dB.

-A three-pole tunable end-coupled filter from 6 to 10 GHz was developed with a broad 35% tuning range. This tuning range was realized by switching distributed loading structures with radio frequency microelectromechanical systems (RF MEMS) capacitive switches. By tuning the coupling capacitors as well as the loading capacitors, the filter achieved a constant fractional bandwidth of 15±0.3 % and an insertion loss ranging from 3.3 dB to 3.8 dB over the entire band. Digital switching ensured good thermal stability, and microstrip transmission lines provided lower insertion loss than with coplanar waveguide. Future improvements are expected to decrease the insertion loss to below 2.1 dB.