ELECTRICAL-IMPEDANCE TOMOGRAPHY APPLIED TO SEMICONDUCTOR WAFER CHARACTERIZATION

A new method is described for determining the distribution of resistiv ity of semiconductor wafers and thin conducting films. It uses periphe ral electrodes to inject small direct currents into the wafer or film and to measure the resultant potential differences, from which the dis tribution of resistivity is calculated. The usable area of the wafer i s not degraded and, because the wafer is scanned electrically, the met hod is much faster than conventional methods. Results obtained on sili con wafers and conducting films are presented, which demonstrate the s ensitivity and reproducibility of the method.