Showing papers by "Kevin D. Leedy published in 2004"

Selecting metal alloy electric contact materials for MEMS switches

Abstract: This paper presents a method for selecting metal alloys as the electric contact materials for microelectromechanical systems (MEMS) metal contact switches. This procedure consists of reviewing macro-switch lessons learned, utilizing equilibrium binary alloy phase diagrams, obtaining thin film material properties and, based on a suitable model, predicting contact resistance performance. After determining a candidate alloy material, MEMS switches were designed, fabricated and tested to validate the alloy selection methodology. Minimum average contact resistance values of 1.17 and 1.87 Ω were measured for micro-switches with gold (Au) and gold–platinum (Au–(6.3%)Pt) alloy electric contacts, respectively. In addition, 'hot-switched' life cycle test results of 1.02 × 108 and 2.70 × 108 cycles were collected for micro-switches with Au and Au–(6.3%)Pt contacts, respectively. These results indicate increased wear with a small increase in contact resistance for MEMS switches with metal alloy electric contacts.

MEMS RF switch integrated process

Abstract: A capacitance coupled, transmission line-fed, radio frequency MEMS switch and its fabrication process using photoresist and other low temperature processing steps are described. The achieved switch is disposed in a low cost dielectric housing free of undesired electrical effects on the switch and on the transmission line(s) coupling the switch to an electrical circuit. The dielectric housing is provided with an array of sealable apertures useful for wet, but hydrofluoric acid-free, removal of switch fabrication employed materials and also useful during processing for controlling the operating atmosphere surrounding the switch—e.g. at a pressure above the high vacuum level for enhanced switch damping during operation. Alternative arrangements for sealing an array of dielectric housing apertures are included. Processing details including plan and profile drawing views, specific equipment and materials identifications, temperatures and times are also disclosed.

Atomic layer deposition of Al/sub 2/O/sub 3//ZnO nano-scale films for gold RF MEMS

Abstract: Atomic layer deposition (ALD) was used to create an Al/sub 2/O/sub 3//ZnO thin film for gold capacitive RF MEMS switches. These films exhibited a widely tunable range of physical properties, allowing the creation of a material capable of dissipating trapped charges and maximizing the on-capacitance of the switch. Predicted pull-down voltages of the ALD-coated switches underestimated the experimental findings due to residual stresses in the ALD film and annealing of the gold during the ALD deposition. Switch cycles to failure were measured using a 10 dBm, 10 GHz, CW signal with a bipolar actuation voltage of 25-55 V. Preliminary testing showed lifetimes of 400 million cycles using 50/50 ALD Al/sub 2/O/sub 3//ZnO films, with ultimate failure due to moisture-induced stiction and particulate contamination, not dielectric charging. The insertion loss and isolation for the switches was typically 25 dBm, respectively, over a 10-25 GHz frequency range.