Characterization, Optimization, and Fabrication of Phase Change Material Germanium Telluride Based Miniaturized DC–67 GHz RF Switches

This paper presents the characterization, optimization, and fabrication of phase change material (PCM) germanium telluride (GeTe) based RF switches investigating the materials' aspect and design parameters of the switches and their impact on the RF performance. Surface properties of GeTe thin films are investigated through atomic force microscopy (AFM), scanning electron microscopy (SEM), and cross-wafer resistance mapping measurements. Optimized GeTe thin films exhibit over five orders of resistance change. Various GeTe switch design constraints are studied via cross sectioning of the fabricated device using a focused ion beam (FIB)-SEM. Current-carrying capacity and resistance of microheaters are extracted using electrical characterization. The RF performance of the PCM switches is optimized using diverse design parameters and characterization of PCM thin films. A six-layer microfabrication process is presented for monolithically integrating RF circuits with PCM switches. Methods to reduce parasitic elements in PCM switches are discussed. The RF performance of the optimized PCM based switch is simulated and measured demonstrating better than 0.4 dB of insertion loss and a return loss better than 20 dB from dc to 67 GHz.