Abstract
Most of the wafer fabrication processes are chemical processes, and wafers are traditionally processed in batches for high throughput. One of the important innovations in semiconductor fabrication is the adoption of single-wafer processing by using cluster tools. Each cluster tool integrates several processing modules (PMs) within a closed environment such that the wafers are processed one by one in a cassette without leaving out of the tool. In cluster tool operations, wafer processing times and robot task times are rather deterministic and can be regarded as constant in the normal condition. For the effective operation of cluster tools, important efforts are made for modeling and performance analysis. In multi-cluster tools, one or more processing PMs are used as a buffer to link two single-cluster tools. Cluster tools in semiconductor fabrication adopt the single-wafer processing technique and represent one of the important innovations in the semiconductor industry.