Low-loss contact pad with tuned impedance for operation at millimeter wave frequencies

In this paper an on-chip pad structure with minimized losses and matched impedance is presented. The pads use a metal ground-shield thereunder to minimize the influence from a lossy silicon substrate. A shunt transmission line stub is used to resonate the pad capacitance, thereby providing a matched impedance into a 50 Ω on-chip transmission line. A second-tier calibration technique was used to extract their 2-port S-parameter characteristic. The measured performance is compared with simulations of standard pad structures up to 65 GHz.