Parameters extraction of submicron thin film microstrip lines at broadband mm-wave frequencies

Aluminum thin film microstrip lines (TFML) with conductor thickness down to submicron scale are fabricated and characterized up to 60 GHz. The characteristic impedance (Zc) and the propagation constant (γ) of the microstrip line are extracted from measured S-parameters. An equivalent-circuit model is proposed based on transmission line theory, and RLCG circuit elements are generated from closed-form formulas. The theoretical and measured values are compared. It is demonstrated that the accuracy of the characteristic impedance determination can be improved dramatically if the effect of line and pad discontinuity is taken into account, allowing a more accurate prediction for the intrinsic electrical properties of the line over a wide range of frequencies.