Building a Wafer Fab Lot Scheduling Knowledge-Based System

摘要

Lot scheduling plays a very important role in semiconductor wafer Fab. According to the up-to-date market situation, a good Lot scheduling mechanism can help wafer Fab to meet constraints and allocate reasonable resources to gain higher profit. The complexity comes from various process flows, dynamic manufacturing environment and variant market requirement. In order to increase average performance, in the most wafer Fabs, the Lot scheduling human expert (Production Controller) utilizes her/his knowledge and experience to do the Lot scheduling. However, it's difficult to train a comprehensive Lot scheduling human expert who must have enough industry experience and real Fab practice through a couple of years. In addition, different Lot scheduling know-how is required in different wafer Fab. How to share and re-use the existing knowledge becomes a major issue in this domain. Therefore, we propose a suite of Lot Scheduling Knowledge-Based System (LS-KBS). We first define a logic-oriented XML-based knowledge representation for knowledge sharing and graphic expression, and then design a visualized knowledge acquisition tool (Logic Map Builder) to elicit the Lot scheduling logics (Logic Map). Three phases are included in our LS-KBS. Firstly, Meta-Knowledge Acquisition Phase is for acquiring the sequence of important knowledge components. Secondly, Knowledge Acquisition Phase is designed to elicit Lot scheduling Logic Map. Finally, Lot Scheduling Phase is developed for knowledge inference by DRAMA to receive relevant facts and generate Lot scheduling result. From the evaluation and the feedback of human expert, we assure that the system not only has the capability to utilize Lot scheduling knowledge as a human expert, but also can be used as a Lot scheduling tutoring system.