Single-pole-four-throw switch using high-aspect-ratio lateral switches

Introduction: Multi-throw switches are widely used in microwave circuits for switch matrices and true-time-delay phase shifting applications. Traditionally, the multi-throw switch uses GaAs MESFETs and pin diodes to perform its switching function. It exhibits good performances at low frequencies, but deteriorates in the high frequency range beyond 1 GHz [1]. On the other hand, the monolithic microwave integrated circuit (MMIC) multi-throw switches require matching network and bias network, which leads to heat generation and other distortions [2]. Recently, microelectromechanical system (MEMS) based switches and phase shifters have been identified as a promising technology with high potential in the existing radio frequency (RF) architectures to reduce weight, cost, size and power dissipation. Until now, very few multi-throw MEMS switches that employ surface micromachining fabrication process have been reported in the literature [3, 4]. However, the metal sticking problem remains a challenging task for reliability and stability of multi-throw MEMS switches fabricated by surface micromachining process. In this Letter, a DC to 6 GHz SP4T switch using deep reactive ion etching (DRIE) micromachined lateral metal-contact series switches is studied. It is formed on the quasi-finite ground coplanar waveguide (FGCPW) transmission lines and actuated by electrostatic force. The mechanical structure of the switch consists of a high-aspect-ratio single-crystal silicon microstructure, which is wrapped around by aluminium (Al) and fabricated by DRIE micromachining technology on a silicon-on-insulator (SOI) wafer.