A cluster tool is an integrated manufacturing system consisting of process, transport, and cassette modules, mechanically linked together. The factors which stimulate an increased use of clustered tools in recent years include improved yield and throughput, reduced contamination, better utilization of the floor space, and reduced human intervention.
Because of high throughput requirements, cluster tools perform a number of activities concurrently, for example, different wafers are processed in different chambers at the same time, and also the robotic transporter can be moving to a position required by the next step. Petri nets are formal models developed specifically for representation of concurrent activities and for their coordination, i.e., for ordering specific actions or for performing actions simultaneously by more than one component of a system.
Traditionally, performance of cluster tools was analyzed by using timing diagrams representing typical sequences of events, and deriving performance formulas from a critical path that determined the cyclic behavior of a tool; such an approach is highly dependent on the analyzed cluster tool and its properties, and becomes quite complicated for cluster tools which are complex. The objective of this research is to use timed Petri nets to modeling and evaluation of a large variety of cluster tools, including single-blade and dual-blade ones, tools with multiple loadlocks, redundant chambers, chamber revisiting and multiple robots.
Specific projects in this area inlcude:
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Copyright by W.M. Zuberek. All rights reserved.
Revised: 2003.01.15 : :1315