is currently the most common way to measure MEMS performance, but the development of in-process wafer-level testing will be necessary for low-cost manufacturing. Wafer-level testing of MEMS presents special challenges that are often product dependent. Nevertheless, generic test-structures that indicate basic mechanical properties of MEMS materials at the wafer-level should be developed and characterized. As more and more industries, universities, and other research groups enter the MEMS field, it is also becoming increasingly important to provide accepted standards that can be used for comparison.

Conclusion. Packaging, which has traditionally attracted little interest compared to device and process development, represents a critical stumbling block to the development and manufacture of commercial and military MEMS. The imbalance between the ease with which batch-fabricated MEMS can be produced and the difficulty and cost of packaging them limits the speed with which new MEMS can be introduced into the market. Alleviating the difficulties of packaging will require a better understanding of (1) the effects of internal friction, Coulomb friction, and wear at solid-solid interfaces and (2) the influence of interfaces on performance and reliability. Test and characterization methods and metrologies are general requirements for continued MEMS development and manufacturing advances. Finally, expanding the small knowledge base in this field and disseminating advances aggressively could have a profound influence on the rapid growth of MEMS.

Recommendation. Research and development should be pursued on (1) MEMS interfaces with operating environments, (2) MEMS packaging, and (3) MEMS assembly into useful engineering systems. The goal should be to define, insofar as possible, generic, modular approaches and methodologies and to extend batch-processing techniques into the various back-end steps of production.

Recommendation. Surface and interface studies should be pursued to address questions associated with contact forces, stiction, friction, corrosion, wear, lubrication, electrical effects, and microstructural interactions at solid, liquid, and gaseous interfaces. Engineering design and manufacturing solutions to these problems should also be pursued.

Recommendation. Standard test methods, characterization methods, and test devices that are suitable over the full range of materials and processes for MEMS should be developed and disseminated. Ideally, metrology structures will be physically small, simply designed, easily replicated, and conveniently and definitively interrogated. MEMS engineering standards should be similar to those already established for materials and devices in conventional sizes by organizations such as NIST, ASTM, and IEEE.

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