Low-Density Fan-Out Heterogeneous Integration of MEMS Tunable Capacitor and RF SOI Switch

Using Low-Density Fan-Out (LDFO) packaging technology, a radio frequency (RF) microelectromechanical systems (MEMS) tunable capacitor array composed of electrostatically actuated beams on 180nm high-voltage CMOS silicon was heterogeneously integrated with a single-pole four-terminal (SP4T) RF switch on 180nm CMOS silicon-on-insulator (SOI). The primary objective of this study was to determine the manufacturability of this System-in-Package (SiP) design, which is proven at time zero through survival of the MEMS device based on acceptable MEMS performance metrics. In addition, the RF SOI switch provides high-voltage electrostatic discharge (ESD) protection for the MEMS device. Capacitive MEMS structures are particularly sensitive to unpredictable electrostatic charging scenarios, such as handling after package assembly and printed circuit board (PCB) surface mount processing. Consequently, resistance to dielectric breakdown by means of robust ESD protection is a very desirable quality. Integrating the RF switch in close proximity with the MEMS device not only enables the ability to withstand charging scenarios in excess of 1kV (human body model), it mitigates the impact of parasitics on RF performance by minimizing interconnect lengths and complexity.