Compensating Probe Misplacements in On-Wafer S-Parameters Measurements

Abstract

As the maximum frequency of electronics is rising, on-wafer measurements play an important role in modeling of integrated devices. Most of the time, due to the lack of measurement accuracy beyond 110 GHz, such models are usually extracted at frequencies much below their working frequencies and are subsequently extrapolated. The validity of such models is then mostly verified after fabrication of the complete chip, with a simple pass and fail test. This is stating the necessity of enhancing measurement results by any means possible, i.e., to reduce the overall uncertainty in such measurements. It is widely accepted that one of the main sources of uncertainty in such measurements is probe contact repeatability, since it is difficult to reach position accuracy below a few micrometers. We are presenting in this article a method to model the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S$ </tex-math></inline-formula> -parameter variation with probe position on the pads, which can then be used to either estimate contact repeatability uncertainty or further enhance measurement results. The approach is validated based on the measurements performed at 500 GHz.