Failure analysis of surface-micromachined microengines

Microelectronic failure analysis (FA) has been an integral part of the development of state-of-the-art integrated circuits. FA of MicroElectroMechanical Systems (MEMS) is moving from its infancy to assume an important role in the successful design, fabrication, performance and reliability analysis for this new technology. In previous work, we focused on the application of several techniques developed for integrated circuit analysis to an earlier version of a surface micromachined microengine fabricated at Sandia. Recently, we have identified important new failure modes in binary counters that incorporate a newer design of the microengine, using a subset of integrated circuit failure analysis techniques including optical microscopy, focused ion beam (FIB) techniques, atomic force microscopy (AFM), and scanning electron microscopy (SEM). The primary failure mode we have identified is directly related to visible wear on bearing surfaces. In this paper, we describe in detail the characteristics of the failure modes in binary counters. We also compare the failure characteristics with those of an earlier version of the microengine.