Publications

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Ceramic interconnect technology has been adapted to new structures. In particular, the ability to customize processing order and material choices in Low Temperature Cofired Ceramic (LTCC) has enabled new features to be constructed, which address needs in MEMS packaging as well as other novel structures. Unique shapes in LTCC permit the simplification of complete systems, as in the case of a miniature ion mobility spectrometer (IMS). In this case, a rolled tube has been employed to provide hermetic external contacts to electrodes and structures internal to the tube. Integral windows in LTCC have been fabricated for use in both lids and circuits where either a short term need for observation or a long-term need for functionality exists. These windows are fabricated without adhesive, are fully compatible with LTCC processing, and remain optically clear. Both vented and encapsulated functional volumes have been fabricated using a sacrificial material technique. These hold promise for self-assembly of systems, as well as complex internal structures in cavities, micro fluidic and optical channels, and multilevel integration techniques. Separation of the burnout and firing cycles has permitted custom internal environments to be established. Existing commercial High Temperature Cofired Ceramic (HTCC) and LTCC systems can also be rendered to have improved properties. A rapid prototyping technique for patterned HTCC packages has permitted prototypes to be realized in a few days, and has further applications to micro fluidics, heat pipes, and MEMS, among others. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under contract DE-AC04-94AL85000.

The burgeoning new technology of Micro-Electro-Mechanical Systems (MEMS) shows great promise in the weapons arena. We can now conceive of micro-gyros, micro-surety systems, and micro-navigators that are extremely small and inexpensive. Do we want to use this new technology in critical applications such as nuclear weapons? This question drove us to understand the reliability and failure mechanisms of silicon surface-micromachined MEMS. Development of a testing infrastructure was a crucial step to perform reliability experiments on MEMS devices and will be reported here. In addition, reliability test structures have been designed and characterized. Many experiments were performed to investigate failure modes and specifically those in different environments (humidity, temperature, shock, vibration, and storage). A predictive reliability model for wear of rubbing surfaces in microengines was developed. The root causes of failure for operating and non-operating MEMS are discussed. The major failure mechanism for operating MEMS was wear of the polysilicon rubbing surfaces. Reliability design rules for future MEMS devices are established.

Micro-Electrical Mechanical Systems (MEMS) is an emerging technology with demonstrated potential for a wide range of applications including sensors and actuators for medical, industrial, consumer, military, automotive and instrumentation products. Failure analysis (FA) of MEMS is critically needed for the successful design, fabrication, performance analysis and reliability assurance of this new technology. Many devices have been examined using techniques developed for integrated circuit analysis, including optical inspection, scanning laser microscopy (SLM), scanning electron microscopy (SEM), focused ion beam (FIB) techniques, atomic force microscopy (AFM), infrared (lR) microscopy, light emission (LE) microscopy, acoustic microscopy and acoustic emission analysis. For example, the FIB was used to microsection microengines that developed poor performance characteristics. Subsequent SEM analysis clearly demonstrated the absence of wear on gear, hub, and pin joint bearing surfaces, contrary to expectations. Another example involved the use of infrared microscopy for thermal analysis of operating microengines. Hot spots were located, which did not involve the gear or hub, but indicated contact between comb structures which drive microengines. Voltage contrast imaging proved useful on static and operating MEMS in both the SEM and the FIB and identified electrostatic clamping as a potentially significant contributor to failure mechanisms in microengines. This work describes MEMS devices, FA techniques, failure modes, and examples of FA of MEMS.