The MZ Capacitance Measurement Method: A Method of Achieving High Accuracy Direct Wafer-level Capacitance Measurements by Taking Multiple Test System Capacitance Measurements at Different Wafer to Probe Separations
Original Publication Date: 2002-Jan-23
Included in the Prior Art Database: 2002-Jan-23
Wafer-level capacitance measurement results often contain significant amounts of error. Even when proper measurement system setup has been performed, differences in measured values between test systems on the order of a few hundred femto-Farads are commonly seen. Proper measurement system setup in this context includes proper frequency, network model selection, bias, and pin connections, and subtraction of parasitic test system capacitance. This document identifies the primary reason for these differences as a Z-dependent parasitic test system capacitance. Specifically, system capacitance measured with probes separated from the wafer is not the same as system capacitance with probes in contact. The Z-dependence of system capacitance is also a strong function of probe card. The MZ capacitance measurement method is presented, which takes system capacitance measurements at different wafer to probe separations and extrapolates to determine the system capacitance at contact. Using this method, measurement offsets between test systems can be reduced significantly.