A 220GHz wafer probe tip with reduced stray fields

A 220 GHz ground-signal-ground wafer probe is described with significantly reduced stray fields near the tip. The upper frequency limit in mm-wave wafer probes is constrained by the size of the probe tip area and stray fields. Measurements of the near-field tip area using a modulated scatterer instrument are presented. A new reduced dimension self-shielding tip design is shown with measured 140 GHz to 220 GHz S-parameter data. Measurements of 0 to 40 GHz crosstalk between pair of tips shows a 10 dB improvement over the present state-of-the-art.