A. Chillico¹, D. Vitali¹, W. Samek², O. Bengtsson¹

Published in:

International Workshop on Integrated Nonlinear Microwave and Millimetre-Wave Circuits (INMMIC 2025), Torino, Italy, Apr. 10-11, ISBN 979-8-3315-1960-5 (2025).

Abstract:

This paper describes an autonomous on-wafer S- parameter and DC measurement system for radio frequency (RF) power transistors with an adaptive probing algorithm. The Devices Under Test (DUTs) are measured in the small signal domain up to 40 GHz. DC and RF features are extracted, together with their derived uncertainties. The DUTs are contacted with an improved adaptive probing method, enabling a precise touch-down of the probes on the structures’ pads. To show the capabilities of the system, Gallium Nitride (GaN) High Electron Mobility Transistors (HEMTs) on a GaN on SiC wafer were measured, together with their respective de-embedding structures. The system enables the statistical evaluation of the HEMTs’ features mapped as the spread in performance over the wafer which is here exemplified by presenting their extracted threshold voltage (V_th), the transient frequency (f_T) and the maximum oscillation frequency (f_MAX). The uncertainty in the V_th is on average 30 mV in the central shots. The novel adaptive probing algorithm reduces the skating precision and accuracy error from 3 μm to 1 μm and is shown to improve the uncertainty of the extracted f_T and f_MAX by around 70%.

Index Terms:

HEMTs, measurement uncertainty, microwave measurement, on-wafer measurements, S-parameters

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