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Optical Micro-Electro-Mechanical Systems (Optical MEMS, or MOEMS) comprise a disruptive technology whose application to telecommunications networks is transforming the horizon for lightwave systems. The influences of materials systems, processing subtleties, and reliability requirements on design flexibility, functionality and commercialization of MOEMS are complex. A tight inter-dependent feedback loop between Component/ Subsystem/ System Design, Fabrication, Packaging, Manufacturing and Reliability is described as a strategy for building reliability into emerging MOEMS products while accelerating their development into commercial offerings.

While considerable press has been given to characterization of mechanical properties of MicroElectroMechanical Systems (MEMS) as related to reliability, environmental robustness, and lifetimes studies, characterization of electrical properties of MEMS have not been widely published. In this paper we present an examination of electrical properties (surface and substrate leakage currents, sheet resistance, substrate contact resistance and interlayer contact resistances) of polysilicon thin films used in surface micromachined MEMS test structures. Environmental and electrical overstress conditions that affect leakage have been studied. Two test structures have been used to independently study surface and substrate leakage currents at different levels of humidity (0% to 80% RH) and applied voltage (100 to 150 volts). Both static and lifetime studies have been conducted. Significant differences in surface and substrate leakage lifetime characteristics are observed, suggesting different failure mechanisms for these two important electrical phenomena in MEMS reliability.

We present a full factorial study of the effect of relative humidity and voltage on the oxidation of surface-micromachined poly-silicon wiring and electrodes. Our system consists of 500 nm thick poly-Si wires and electrodes insulated from the substrate wafer by 600 nm of Si-rch SixNy, fabricated using a surface-micromachinging process. In dry ambients, oxidation or damage to the bottom poly-Si layer (the Poly0 layer) in MicroElectroMechanical Systems (MEMS) devices occurs so slowly that little can be learned in a timely manner, even when stressing the electrodes at electric fields close to dielectric breakdown. We observe however that in ambient with elevated relative humidity the Poly0 wires and electrodes anodically oxidize within a short period of time when operated at moderately large voltages. Only the most positively biased poly-Si structures oxidize, and we describe the anodic oxidation and association volume expansion as a function of a number of accelerating factors including relative humidity and voltage. A threshold is observed in relative humidity bot not in voltage.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.