An Advanced Calibration Method for Probe Leakage Correction in On-Wafer Test Systems

Abstract

This article presents an advanced calibration method for solving the error terms due to probe-probe leakage in an on-wafer test system. A new 12-term error model for the on-wafer test system including vector network analyzer (VNA), frequency extenders, cables/waveguides, probes, probe contact pads and probe-probe leakage is introduced. A two-step calibration process and an algorithm with four on-chip calibration standards including one undefined Thru, two pairs of undefined symmetrical Reflects such as Open-Open and Short-Short pairs, and a pair of known Match loads has been developed. In addition, an improved circuit model for the Match load is proposed for enhanced accuracy. The calibration method has been tested on a mismatched attenuator for the frequency range between 0.2 and 110 GHz, and the results are compared with numerical simulation and existing calibration methods. It is shown that the attenuator’s <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert S_{11}\vert $ </tex-math></inline-formula> is more consecutive and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert S_{21}\vert $ </tex-math></inline-formula> has been improved by up-to 1.7 dB. It is evident that the proposed calibration method has a simpler calibration process and less stringent requirements on calibration standards which are key for on-wafer system calibration at millimeter-wave and terahertz frequencies. More importantly, the new calibration method is more suitable for measurements in which DUTs have variable lengths.