International Journal of Biosensors & Bioelectronics
This paper presents the performance and reliability testing of microelectromechanical systems (MEMS) switches by using a micro-force sensor which was originally designed/used to conduct mechanical testing of biological cells. MEMS switches are key components for radio frequency (RF) applications due to their extremely low power consumption and small geometries over conventional technologies. However, unstable electrical contact resistance severely degrades the performance and reliability of such micro-switches. Therefore, our focus is to improve the performance and reliability of “cold” switched micro-contacts by using novel contact materials and engineered micro-contact surfaces. The contact metallurgies considered in this work are “similar” thin film combinations of Au, and composite Au/CNT. The non-engineered switch consists of a metallic hemispherical bump and a planar sheet as upper and lower contacts, respectively. On the other hand, the engineered switches have 2D pyramid structure in lower contacts while having a hemispherical bump at upper contact. Hemisphere on planar, Au-Au, contact pairs resulted in initial contact resistance (RC) values of ~0.1Ω (FC=200µN) that linearly increased to ~1.0Ω after ~10×106 cycles and then failed open (~10.0Ω) at ~20×106 switching cycles. The Au-Au/CNT composite, hemisphere on planar contact pair showed similar RC performance with extended reliability (~40×106 switching cycles) when the composite film was integrated into the lower planar contacted. Upper hemisphere on the 2D pyramid, Au-Au, contact pairs resulted in initial RC values of ~0.9Ω (FC=200µN) that linearly decreased to ~0.5Ω at >10×106 cycles (not failed). This work suggests that the combination of engineered lower contacts and composite materials can significantly improve the performance and reliability of micro-switches.