Temperature dependence for in-use stiction of polycrystalline silicon MEMS cantilevers

Adhesion during operation, referred to as in-use stiction, shortens the useful lifetimes and reliability of microelectromechanical systems (MEMS). In this paper, operational reliability tests were performed to investigate the effect of temperature on in-use stiction for surface-micromachined, polycrystalline silicon MEMS cantilevers subject to three release techniques: supercritical CO2 drying, laser irradiation repair, and an octadecyltrichlorosilane (OTS) deposition process. The cantilevers were heated from room temperature to 300degreesC and then returned to room temperature. The cantilevers were electrostatically actuated at specific temperatures between 22 and 300 C during the heating and cooling stages, and their sticking probabilities determined. The failure probability results exhibit a slight variation with temperature for microcantilevers released using the supercritical CO2 dry and laser irradiation repair. However, in-use stiction of microcantilevers coated with OTS is strongly dependent on temperature. The incidence of in-use stiction was highest during the heating stage, reduced during the cooling stage, and decreased further when the samples were reheated to 300 degreesC. The results indicate that thermal annealing of OTS coated structures in air decreases in-use stiction failures. Surface characterization of OTS coated samples was conducted using contact angle goniometry, atomic force microscopy, and X-ray photoelectron spectroscopy. (C) 2004 Published by Elsevier B.V.