Development of Single-Ended and Balun Integrated Probes for THz Applications

A number of new devices and components are being developed in the terahertz spectrum for applications such as radio astronomy, medical and surveillance imaging. However, these development efforts are hampered by difficulties in the characterization processes. Typically, terahertz modules fabricated on semiconductor material need to be diced into individual chips, and assembled to a precision micromachined block for test. This time-consuming and arduous characterization process adds to the complexity and cost. The on-wafer probe solves these problems by providing a tool to characterize the terahertz DUT on-wafer, in large volumes and with higher precision.
In this dissertation, a new fabrication technology is first developed to fabricate a single-ended probe with GSG probe tips. The improved fabrication processes have been used to realize on-wafer probes up to 1.1 THz, which is the first reported THz probe in the community. Further tests on these probes demonstrate that they can maintain electrical repeatability over long term usage.
In the second part of this work, a prototype balun integrated probe at W-band is developed to enable on-wafer characterization for differential circuits. Detailed design considerations, as well as test results, are shown in this work. Just as with the GSG probes, the GSGSG design has the potential to be scaled to higher frequencies. The balun integrated probe can be used to provide a convenient way to characterize the emerging differential MMIC devices with better accuracy and lower cost.