Three-port RF characterization of MOS transistors

Abstract

This paper presents the complete RF characterization of a MOSFET in terms of its 3-port admittance network parameters up to the cut-off frequency. The effect of the non-ideal short presented by the GPG (Ground Power Ground) probe - used at the third port for 2-port RF measurements - on characterized data is discussed. An algorithm is developed to de-embed the non-ideal short by (i) characterizing the GPG probe, (ii) representing the transistor by its general equivalent circuit whose components are extracted from the measured y-parameter data in three different configurations, and, (iii) reconstructing the 3-port parameters after removing the GPG probe impedance from the network. The validity of the method is demonstrated by the close agreement between diagonal elements of the 3-port admittance matrix obtained from two different configurations. Without probe de-embedding, the disagreement is over 70% at higher frequencies in some of the parameters. From the accurate de-embedded admittance parameters, the measured 3-port capacitance coefficients for the MOS transistor at different frequencies and biases are reported for the first time. Interestingly, it is observed that the non-quasi-static channel conduction manifests as the increasing difference in the magnitudes of Gsg (trans-conductance in Common Drain configuration) and Gdg (trams-conductance in Common Source configuration) with frequency.