A highly simple failure detection method for electrostatic microactuators: application to automatic testing and accelerated lifetime estimation

Reliability and testability are two important factors for the development of batch fabrication of microelectromechanical systems (MEMS) or mixed MEMS/IC applications. In that frame, an easy-to-implement electrical method of detection of failures is presented in this paper, valid for every kind of electrostatic microactuators showing pull-in behavior, with great expectation value in the case of arrayed MEMS. The method relies on the detection of a pull-in current peak at very low frequency. An experimental setup is described and results are shown obtained with prototypes of electrostatic microactuators with parallel capacitances created by deep reactive ion etching on silicon-on-insulator wafers. This method is really suitable for automation and application to on-line testing during mass production and reliability studies. The functional schematic of a test circuitry is proposed for implementation in an industrial tester or for built-in self-test purposes. Then, in order to illustrate the benefits of this method for reliability studies, it is used in conjunction with high voltage testing for accelerated lifetime measurements. A time gain factor of 20 is achieved with above-mentioned test structures.