Reliability of microelectromechanical systems (MEMS)

Reliability is a key parameter for the eventual prevalence of microelectromechanical systems (MEMS) as either sub-components or as standalone products. Traditionally, micromachined components have been made by separating the micromachined chip design and fabrication processes from the packaging and reliability issues. This "evolutionary" partitioning of microsystems has led to long incubation times for the commercial success of MEMS based products. Packaging involves bringing together (i) multitude of design geometries of the various constituent parts, (ii) interfacing diverse materials, (iii) providing required input/output connections and (iv) optimization of all of these for performance, cost and reliability. On the other hand, reliability depends on (i) the mutual compatibility of the various parts with respect to the desired functionality, and (ii) the designs and materials from the standpoint of long-term repeatability and performance accuracy. Reliability testing provides techniques for compensation, and an understanding of the catastrophic failure mechanisms in microsystems. It is imperative that the successful design and realization of microsystems or MEMS products must include all levels of packaging and reliability issues from the onset of the project. Although, such a holistic top-down approach poses formidable technical challenges, the problem can be simplified by using the rapidly evolving MEMS infrastructure in the areas of materials, fabrication and design. This paper will discuss, overall MEMS reliability issues and present results on reliability testing of micromachined capacitive pressure sensors for high vacuum and biomedical applications currently being commercialized at Integrated Sensing Systems Inc.