On-wafer photoconductive sampling of MMICs

A practical technique for the on-wafer characterization of the high-frequency response of a MMIC was developed, using photoconductive (PC) sampling. It provides S-parameter measurement with broadband, high sensitivity, and accurate calibration. In addition, due to its inherent broadband signal generation on the wafer, high-frequency information of the circuits can be extracted merely by using DC probes. Starting from a hybrid testing configuration, the compatibility of PC switch fabrication with the MMIC production process is demonstrated. In this phase, 40-dB dynamic range in the S-parameter measurement was achieved. The success motivated the monolithic integration of the PC switches onto the MMIC. Efforts were made to reduce the size of the optical test structure. Good agreement between a conventional network analyzer measurement and two optical testing results has been achieved, showing that built-in optical test structures can be designed to have comparable overall size with existing CPW test structures. The S-parameter characterization of a nonlinear transmission line is demonstrated