Test Modification for Reduced Volumes of Fail Data

Abstract

As part of a yield improvement process, fail data is collected from faulty units. Several approaches exist for reducing the tester time and the volume of fail data that needs to be collected based on the observation that a subset of the fail data is sufficient for accurate defect diagnosis. This article addresses the volume of fail data by considering the test set that is used for collecting fail data. It observes that certain faults from a set of target faults produce significantly larger numbers of faulty output values (and therefore significantly larger volumes of fail data) than other faults under a given test set. Based on this observation, it describes a procedure for modifying the test set to reduce the maximum number of faulty output values that a target fault produces. When defects are considered in a simulation experiment, and a defect diagnosis procedure is applied to the fail data that they produce, two effects are observed: the maximum and average numbers of faulty output values per defect are reduced significantly with the modified test set, and the quality of diagnosis is similar or even improved with the modified test set.