Due to the high investment costs in semiconductor manufacturing facilities (wafer fabs), it is crucial to ensure high utilisation rates of tools. And, by performing the right qualifications of process types (recipes) on them, tools can be used more efficiently. Hence, effective qualification management (QM) is a key factor for wafer fabs. In this article, QM for wafer fabs is first defined and discussed. Then, flexibility measures are proposed, which help to compare flexibility for different qualification settings of workshops, and to support decisions on which qualifications to perform. Different examples illustrating the flexibility measures are discussed. This article concludes with some research perspectives.