How to Improve Accuracy of Wafer-Level Calibration at mm-Wave and sub-mm-Wave Frequencies
Wafer-level S-parameter measurement at mm-wave and sub-mm-wave frequencies plays a crucial role in the model development and IC design verification and debug of advanced semiconductor technologies. Accurate calibration of the entire wafer-level measurement system to the RF probe tip end or to the intrinsic device terminals is a critical success factor for extracting trustable device model parameters and characterizing true performance of a RF IC. Challenges of obtaining accurate, reproducible and trustable results drastically increase with the frequency: methods and practices that have been working well, tend to fail or to yield results which are difficult to interpret. This presentation will discuss specifics of S-parameter measurement and calibration techniques at wafer-level. Special attention will be paid to how to choose the right calibration method for particular measurement application needs. Definition of the calibration reference plane and the measurement reference impedance of a calibrated system will be reviewed as well. Finally, the potential sources of calibration residual errors and common misconceptions will be analysed. Practical examples will be given on how to minimize the impact of such errors on the measurement accuracy of a calibrated probe system.