Silicon-Based Integration Technology for Terahertz Systems

Abstract

Low-loss integration technologies are essential for the design of high-frequency systems and components. Conventional PCB methods, such as metallic transmission lines, become challenging to employ in the Terahertz (THz) region due to significant ohmic and radiation losses. This thesis aims to design, fabricate, and test THz systems using a promising all-silicon multi-band integration technology: Effective Medium-Suspended Silicon Waveguide (EM-SSW). The technology utilizes high-resistivity silicon (HR-Si) and photonic crystal-like effective medium structures to construct waveguides with high-modal confinement. Additionally, suspending the waveguide’s core minimizes substrate-modal interaction, enabling multi-band high-performance up to the THz range. To assess the practical performance of the proposed technology, our research investigates two systems: D-band and Y-band frequency up-converted sources. These devices are implemented using cascaded tripler blocks that leverage the non-linearity of GaAs Schottky diode chips to generate harmonic output power. The chips are mounted on the silicon wafer using an embedded-chip ultra-short wire bonding packaging technique within the high-precision three-mask process of the proposed integration technology. The system components, i.e., filters, matching circuits, transitions, and combiners, are designed using the proposed allsilicon technology and are hybrid integrated with the active chips to build the operational THz system. The excitation method uses contactless silicon probes made in-lab for onwafer probing of the devices. A novel self-contained THz probe is effectively designed and fabricated to overcome assembly challenges at high frequencies. Two different THz probe designs are used to characterize the source prototypes at D-band and Y-band. Based on the simulations and measured data, the passive components exhibited high performance with the proposed integration technology and were effectively employed to build the prototype of the THz source. Upon excitation with a V-band input signal at the first stage, the generated power at D-band reached −1 dBm. Consequently, novel designs incorporating two combined signal branches were fabricated to adequately drive the second tripler stage with sufficient input power, resulting in an approximate Y-band power level of −18 dBm at a frequency of 0.5 THz.