Design of SiGe Nano-Electromechanical relays for logic applications

This paper presents a design approach for Nano-ElectroMechanical Structures (NEMS) relays taking Casimir or van der Waals forces into account for the static and dynamic modeling of the devices. The goal is to design these structures using the Poly Silicon Germanium process, with several fabrication constraints on the gap, the structure thickness and the critical dimensions. The design approach starts with an analytical study taking the general expression for adhesion forces into account. Considering the van der Waals forces, finite element simulations performed on a simple cantilever confirm these analytical results. More complex structures are then designed, such as cantilevers with larger plates and torsion actuators, in order to increase the performance of the devices and to avoid permanent stiction. Inverters as well as NAND gates are designed and optimized to reach CMOS-equivalent specifications and finally a ring oscillator based on the new inverter and NAND gate is proposed.