Defense Tech Briefs - Life Tests of a Microwave MEMS Capacitive Switch

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Life Tests of a Microwave MEMS Capacitive Switch

Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio

Aug 01 2007

Page 2 of 2

Figure 2. Characteristic Potentials measured at intervals during life tests showed small drifts but no significant deterioration of performance.

The switch insulator was made from a 0.28-μm-thick SiO₂ layer sputtered onto the lower electrode, but this layer was not continuous: instead, it was patterned into a series of hexagonal posts about 4 μm wide at an 8-μm pitch. As a result, the proportion of switch area occupied by air as the dielectric exceeded that occupied by SiO₂ as the dielectric. This patterning of the switch insulator undesirably reduced the on-state capacitance but desirably reduced the contact area accessible to dielectric charging. Trading away some of the on-state capacitance to reduce dielectric charging could, potentially, be a way of increasing operational lifetimes of switches like this one.

In the tests, the switch was actuated by a trapezoidal waveform at a repetition rate of 60 kHz for a total time of 476 hours, amounting to slightly more than 100 billion switch cycles. Quantities measured in these tests included (1) detector output potentials indicative of on- and off-state capacitances and (2) pull-in and release potentials, both which showed small drifts in switch characteristics (see Figure 2). The drifts in detector output potentials were not considered to represent significant deterioration of performance. The drifts in pull-in and release potentials were interpreted as being partly attributable to dielectric charging.

This work was done by C. L. Goldsmith and D. I. Forehand of MEMtronics Corp., and Z. Peng and J. C. M. Hwang of Lehigh University for the Air Force Research Laboratory. For more information, download the Technical Support Package (free white paper) at www.defensetechbriefs.com/tsp under the Electronics/Computers category. AFRL-0031

This Brief includes a Technical Support Package (TSP).

Life Tests of a Microwave MEMS Capacitive Switch (reference AFRL-0031) is currently available for download from the TSP library.

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