Mutual interference in calibration line configurations

When using multiline TRL calibrations for correcting on-wafer measurements, the accuracy of the result depends crucially on the consistency of the calibration set. For example, each line standard used in the calibration process must allow unambiguous measurements, i.e., the only difference between the various transmission-line elements should be line length. To this end, the pad structure for the probes, the probe mechanical contact properties and the environment including other structures, wafer or chip boundary and backside structures (metallization, chuck material) should be the same for each element. If this condition is not fulfilled, errors in the multiline TRL calibration process occur. This paper discusses the resulting deviations and presents some first rules for a proper layout of the calibration standards.