Priority-based tool capacity allocation in the foundry fab

A virtual unit, tool group, is used to represent the group of tools in semiconductor foundry. Hence, a tool may belong to several tool groups because it may be handle several kinds of recipes. The coupling relation between the tools and the tool groups is a complex many-to-many relation. The paper aims to decide the tool-dispatching rule in tool capacity allocation. The term, "priority-based", is two-fold. One is to prioritize the lots in the fab, the other is to prioritize the tools in the correlated tool groups. The priority-based algorithm is used to estimate the tool utilization, bottleneck, tool-sharing in the tool groups, throughput of the tool groups and WIP (work in process) in a specific day. The proposed algorithm is applied to a real foundry fab and the results show that maximum fuzzy candidative ratio is better than other rules. Besides, a demonstration shows that the supervisor can find the bottleneck tools by the proposed algorithm and release the bottleneck by adding the right tools.