Comparing resonant cavity and on-wafer measurements of the complex permittivity of fused silica to 110 GHz

Researchers rely on resonant cavity and on-wafer measurements of complex permittivity for millimeter-wave circuit design and simulations. Resonant cavity measurements are more accurate but only measure discrete (often single) frequencies. On-wafer measurements are less accurate but offer broadband measurements over huge frequency ranges. Here, we compare resonant cavity and on-wafer complex permittivity measurements of the same fused silica wafer. We quantify the uncertainty of each method and the agreement between methods. Careful wafer design lets us cut coupons for resonant cavity measurements and chips for on-wafer measurements from a single wafer. Comparing and correlating these measurements gives us broadband complex permittivity (on-wafer) anchored with much smaller uncertainties at discrete frequencies (resonant cavities). In addition to the frequency-dependent properties of fused silica, this study provides insight into the overall measurement science surrounding millimeter-wave materials.