Accelerating aging failures in MEMS devices

Abstract

The feasibility of using temperature and humidity to age vapor-deposited SAM-coated electrostatic-actuated MEMS devices with contacting surfaces was determined. Failures were dependent on both temperature and humidity. The trend indicated longer life at both lower temperatures and lower humidity levels. Using cantilever beams, measurements reveal degradation of the VSAM (vapor-deposited self assembled monolayer) surface coating when stressed at 300/spl deg/C with controlled humidity environments of 500 and 2000 ppmv. In particular, we have seen the surface adhesion change for these beams stressed at 300/spl deg/C for time intervals of 10, 24, 50, 100, and 200 hours. However, there is no measurable change after 2 hours. The higher humidity case promotes the same surface adhesion change in a factor of ten less time. The complex MEMS devices tested followed the same trends as the beam test structures. We definitely observe a failure of the MEMS devices due to the environment with most failures occurring at 300/spl deg/C and some failures at 200/spl deg/C. These failures are due to an adhesion site in the hub of the load gear where the typical gap is 0.3 /spl mu/m.