A technique for improving the accuracy of wafer probe measurements

Since microwave wafer probe standards are very small physically, it has been assumed that their nonideal characteristics are correspondingly small. This assumption is not completely true and, if the standards are not properly verified, the system is not calibrated to the probe tips, producing measurement errors. A technique is developed to increase the accuracy of these measurements by identifying the calibration standards as imperfect. This procedure minimizes deviations from the linear magnitude and phase values of a one-port measurement system by using a fourth standard whose characteristics are assumed known. After the iterative program converges, values for the standards are calculated. The stub response is then determined and demonstrates a linear variation with frequency. This result verifies the method, calibration standards, and measurement accuracy of the system.<>