Cryogenic Vacuum On-Wafer Probe Svstem

We describe the the design of a novel cryogenic vacuum on-wafer probe system. Detailed descriptions of the measurement system, and the effect of calibration temperature on the measurement accuracy are given. We demonstrate the feasibility of making routine high frequency variable temperature measurements from 40 K to 300 K for long durations with a simple open cycle liquid nitrogen and liquid helium cooling systems. Cryogenic microwave measurements have been performed on advanced heterostructure bipolar transistors, pseudomorphic InGaAs/GaAs field-effect transistors, and high temperature superconducting thin film transmission lines. By characterizing state of the art high frequency transistors at cryogenic temperatures we not only explore the ultimate operation of these devices but also carry out comprehensive studies of the effects of parasitic elements, gate lengths, device structure and materials to determine fundamental transport properties. In addition, temperature dependant models are being developed for both bipolar and field-effect transistors.