Reliability assessment of electrostatically driven MEMS devices: based on a pulse-induced charging technique

摘要

The charging mechanism of electrostatically driven MEMS devices was investigated. This paper shows experimental results of (i) electrostatic discharge (ESD) experiments, (ii) charging mechanism modelling and (iii) Kelvin probe force microscopy tests. It highlighted dielectric failure signature occurred under ESD events and allowed understanding of the underlying breakdown mechanism. A further study of the charging effect in conditions below the breakdown was carried out. A new approach to explore trapping phenomena that take place in thin dielectric used for electrostatic actuation is reported. Indeed a pulse-induced charging (PIC) test procedure aimed at reliability assessment of electrostatically actuated MEMS devices is presented. Based on this method, a procedure for carrying out stress testing was defined and successfully demonstrated on capacitive MEMS switches. In this case, high-voltage pulses were applied as stimulus and the parameter V_(capamin), which is directly related to the charging of the insulator layer, was monitored. The PIC stress test results were correlated with conventional cycling stress ones. Finally, temperature-dependent measurements, ranging from 300 up to 355 K, were reported in order to validate the thermal-activated behaviour of the test structures. According to an Arrhenius model, the given reference material showed an activation energy of around 0.77 eV.