1. A method of processing a plurality W of semiconductor wafers, the method comprising: sequentially performing n (first to n-th) process steps on the plurality W of wafers, wherein the order of processing the W wafers is different in each of at least P of the n process steps, wherein n, P and W are real numbers, and P is equal to or less than n; determining the values of a first characteristic parameter for each of the W wafers; establishing for each one of the n (first to n-th) process steps a first data set that relates the first characteristic parameter values of the W wafers to the wafer processing order corresponding to each one process step; calculating a conversion relation for each of the n (first to n-th) process steps by performing a Fourier transform on the corresponding one of the n (first to n-th) first data sets; and using each one of the first to n-th conversion relations for detecting a pattern in at least one of the n (first to n-th) first data sets.