Failure analysis system of semiconductor memory device

摘要

In failure analysis method of a semiconductor memory device, an absolute value of a position difference between two fail bits of a two-dimensional bit map is calculated while a histogram corresponding to the absolute value of the position difference is updated. The bit map indicates a map of fail bits and each fail bit corresponds to a fail memory cell. The above calculation is repeated to all combinations of two of the fail bits in the bit map. Then, an expectation function value is calculated for each of values from the histograms and the number of the fail bits. Finally, whether the fail bits has regularity or irregularity for each value is determined based on the calculated expectation function value for the value.