Richard E. Strawser

Microswitches with sputtered Au, AuPd,Au-on-AuPt, and AuPtCu alloy electric contacts

This paper is the first to report on a new analytic model for predicting microcontact resistance and the design, fabrication, and testing of microelectromechanical systems (MEMS) metal contact switches with sputtered bimetallic (i.e., gold (Au)-on-Au-platinum (Pt), (Au-on-Au-(6.3at%)Pt)), binary alloy (i.e., Au-palladium (Pd), (Au-(3.7at%)Pd)), and ternary alloy (i.e., Au-Pt-copper (Cu), (Au-(5.0at%)Pt-(0.5at%)Cu)) electric contacts. The microswitches with bimetallic and binary alloy contacts resulted in contact resistance values between 1-2Omega. Preliminary reliability testing indicates a 3times increase in switching lifetime when compared to microswitches with sputtered Au electric contacts. The ternary alloy exhibited approximately a 6times increase in switch lifetime with contact resistance values ranging from approximately 0.2-1.8Omega

A Latching Capacitive RF MEMS Switch in a Thin Film Package

A latching capacitive RF MEMS switch has been successfully designed, fabricated and tested. The switch uses a long thin metal cantilever which is electrostatically held to an upper electrode at the free end and to a lower electrode at the beam root end forming an S-shaped actuator. The upper electrode sits on top of a thin dielectric shell which also serves as part of the package for the device. Slight dielectric charging holds the cantilever in either the on-state or off-state between switching pulses. In the latched states with no bias, insertion loss is 0.2 dB at 10 GHz and isolation is >20 dB in a narrow band around 10 GHz. Repeatable switching has been demonstrated for actuation voltages below 20 V. Hot-switched power handling has been tested up to 6 W at 10 GHz without failure

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

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 <0.35 dB and > 25 dBm, respectively, over a 10-25 GHz frequency range.