Characterization and Deembedding of Negative Series Inductance in On-Wafer Measurements of Thin-Film All-Oxide Varactors

A fast dielectric characterization method is on-wafer probing of circular, capacitive test structures. However, this was found to be accurate only for limited frequencies in the megahertz range. At higher frequencies, the measured impedance data deviate from the expected characteristic. The effective capacitance shows a negative slope, although it should increase up to infinity at electrical resonance. This prevents from extracting accurate material data at RF frequencies. The modeling of this phenomenon as an appealing negative series inductance is presented, as well as the robustness of its compensation. The resulting wide-frequency fitting additionally enables the characterization of the bottom electrode material. This compensation is applied to measurements of the recently presented all-oxide varactor based on the conducting oxide SrMoO 3 (SMO). Previously, only independent conductivity measurements for nonintegrated SMO thin films were available. This compensation now allows for a valid confirmation of the low expected resistivity $45~\mu \Omega \text {cm}$ of integrated thin films.