Characterization of Stiction Accrual in a MEMS

Stiction remains one of the chief reliability concerns for microelectromechanical systems (MEMS) devices. In this paper, we quantify and analyze the rate of accrual of stiction in a standard MEMS device under a set of controlled temperature and humidity splits. An accelerated aging system was employed to more rapidly induce stiction in the MEMS. Optical characterization techniques were used to study the progression of stiction. The stiction accrual was quantified in terms of stiction equivalent energy, which provides compensation for mechanical fatigue in the devices due to long periods of operation. The fastest accrual of stiction was seen in the 90degC, 80% relative humidity (RH) split with approximately 80% of the MEMS elements failing within 4.4 times 10⁹ cycles (10 h) with 2.7 times 10^-14 Joules of stiction equivalent energy while the 60degC, 20% RH showed the least stiction accrual rate with less than 2% failure for 2.26 times 10¹² cycles (1500 h). In general, the stiction was seen to increase with an increase in humidity while mechanical fatigue showed an increase with an increase in temperature. Atomic force microscopy topography imaging was used to assess physical wear at the contacting areas. The results revealed that there were not any discernable changes in the surface profile due to long periods of actuation.