Via-adjusted microstrip launch for sub-terahertz wafer probing

A new design for a microstrip launch is proposed to improve the measurement repeatability at sub-THz frequencies. Performance improvement is achieved by adjusting the ground vias´ position to the rear of the launch by which it becomes less sensitive to probe-tip placement compared to conventional launches using microstrip or co-planer waveguides. The investigation was done using HFSS, 3-D finite-element-method based electromagnetic simulation software, with tight convergence criteria to meet the required tolerances. The proposed design can be applied to other RF interfaces that required high repeatability such as pads for wire-bonds and footprints for surface-mount components, without increasing cost or compromising RF performance.