Validity of Room-temperature Calibration for On-wafer Measurements up to 220 GHz, 125 °C, and 48 h

At-temperature calibration is not only inconvenient, but also complicated by the temperature dependence of impedance standards. This paper examines the validity of a room-temperature calibration for on-wafer measurements from 70 kHz to 220 GHz, from 25°C to 125°C, and up to 48 h. The results indicate that the room-temperature calibration is applicable up to 125°C provided errors up to 0.5 dB in magnitude and 5° in phase are tolerable. Consistent with previous reports up to 110 GHz, the present errors are mainly caused by the time-dependent system drift instead of the temperature dependence of impedance standards. For unknown reasons, the system proven to be stable at room temperature drifts significantly at elevated temperatures. This makes elevated-temperature measurements challenging because presently it takes approximately three hours for the system to stabilize at a new temperature. Therefore, in the near future, efforts should be concentrated on stabilizing the system faster rather than correcting for the temperature dependence of impedance standards.