Abstract: The faults are described using a fault description which comprises data which have been determined using failure modes and effects analysis. The fault description is extended by information regarding the dependency of possible faults and the frequency of occurrence of said faults. The extended fault description is used to ascertain, for a prescribed fault event, the fault tree and the frequency of occurrence of the fault event.

Abstract: A computer-implemented method for identifying a best tool from a plurality of tools that perform a same operation in a semiconductor fabrication line that includes the steps of determining a first median yield for each of the plurality of tools within a first time interval, weighting the first median yield based on a total number of wafers processed by each of the plurality of tools within the first time interval, determining a second median yield for the semiconductor fabrication line over the first time interval, obtaining a weighted yield difference for each of the plurality of tools relative to the second median yield, and outputting the weighted yield difference for each of the plurality of tools.