Wafer Probing Issues at Millimeter Wave Frequencies

With increased wafer probing activity at millimeter wave frequencies, and the maturing of wafer probing technology itself, new issues have arisen. Many of these issues involve phenomena which, although present at lower frequencies, do not cause significant perturbation at measured data below 40 GHz. At higher frequencies wafer probe systems begin to experience the effects of phenomena such as surface waves and sensitivity to the RF properties of the surface below the device under test. This paper presents measured data showing the presence of surface waves and how they interact with wafer probes and coplanar waveguide transmission lines. Methods for minimizing these interactions are explored and quantified. Finally, the impact of surface wave effects on wafer calibrations are addressed.