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

Abstract

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 CO 2 drying, laser irradiation repair, and an octadecyltrichlorosilane (OTS) deposition process. The cantilevers were heated from room temperature to 300 °C 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 CO 2 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 °C. 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.