Non-contact differential-mode on-wafer device characterization in the mmW and THz bands

We present a novel on-wafer metrology technique for characterization of differential Millimeter-wave and Terahertz Monolithic Integrated Circuits (MMIC and TMICs) using a contact-free setting that relies on quasi-optical coupling of test signals onto the device on chip. Due to their advantages over single-ended topologies, differential circuits are typically preferred, particularly for superior noise performance. However, lack of characterization equipment at sub-mmW frequencies severely inhibits the proliferation of differential MMIC and TMICs. Currently, balun-integrated wafer contacting probes are most commonly used for mixed mode S-parameter measurements. Nevertheless, these probes are commercially available only up to 110 GHz with prototypes proposed up to 140 GHz. In this paper, initial validation of novel, non-contact, differential-mode on-wafer probes is presented with validations for the 220-325 GHz.