A technique for directly plotting the doping profile of semiconductor wafers (“8-shaped way”)

A new technique for directly plotting the doping profile of a semiconductor wafer is described. The peculiarities of this technique are a double passing (with a frequency conversion) of a test signal through the sample and the use of an autoregulated voltage source. The present technique has certain advantages as compared with previous ones especially for small measured capacitances (1 pF or less). Both “high frequency” and “low frequency” N(x) values may be obtained by using this technique.