Compensating Differences Between Measurement and Calibation Wafer in Probe Tip Calibrations - Deembedding of Line Parameters

Differences in probe-tip-to-line geometry and substrate permittivity between measurement and calibration wafer deteriorate measurement accuracy. A technique is presented which characterises the discontinuities near the probe-tip based on the measurement of two lines with different length. Unlike previous methods, the equivalent elements representing the discontinuity are extracted at each frequency point together with the propagation constant and the characteristic impedance of the line. The method has been tested by characterising the differences between coplanar lines on an Alumina calibration and a GaAs measurement substrate. In most cases, a frequency-independent shunt capacitance to ground was found to be the dominating parasitic.