Parasitic Probe Effects in Measurements of Coplanar Waveguides with Narrow Ground Width

On-wafer measurements contain a large variety of parasitic effects degrading the accuracy of multiline Thru-Reflect Line (mTRL) calibration. These effects are caused by internal and external disturbances such as probe effects, multimode propagation, crosstalk between adjacent structures and radiation effects. While a lot of investigations have been performed for the most common coplanar waveguides (CPW) with nominal ground width, CPW with too narrow ground width have not been investigated thoroughly. This paper demonstrates how the probe effects deteriorate the mTRL-calibrated S-parameters for CPW structures with narrow ground width.