Calibration and Measurement Considerations for Deriving Accurate Temperature Dependent Equivalent Circuits

The demand for more physically meaningful device models has resulted in improved ECP (Equivalent Circuit Parameter) extraction techniques, such as those employing cold-FET, pinched-FET, hot-FET S-parameter measurements. These techniques are now being extended to develop temperature and bias dependent device models. Recent advances in thermal probing equipment have dramatically reduced the cost of obtaining temperature dependent S-parameter data, making thermal device modeling more practical. However, the extreme range in temperatures of interest, -65 °C to 200 °C, has increased the complexity of the calibration and measurement issues. Unfortunately, these issues are most often ignored. A discussion of the thermal probing measurement environment, critical calibration considerations, and key measurement issues is presented. Automated on-wafer S-parameter measurements of both MESFET and PHEMT devices are used to demonstrate the effect of improper system calibration on extracted temperature dependent equivalent circuits.