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Recent trends in the semiconductor industry indicate the need to explore alternatives to batch-wafer manufacturing. One proposed alternative is a micro-factory based on cluster tools. This paper presents an analysis of the effect of redundant chamhers and chamber revisitation process sequences on the throughput in an individual cluster tool. Theoretical models which quantify the time required to process a lot of wafers in a cluster tool are developed for these situations. The differences between scheduling algorithms which use the load-lock as a queue and those that do not are also explored. Finally, the models developed in the work are integrated into a model which bounds the minimum theoretical turn-around-time which can be achieved in a cluster based fab.

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Abstruct-The practical development and implementation of rapid thermal processes will significantly influence the semiconductor fabrication industry. With the capability to perform heat cycles quickly and with low thermal budgets, rapid thermal processors have the potential to supplant conventional thermal systems in the years to come. Currently, rapid thermal processors are unable to match the thermal process uniformity produced in conventional convective-based systems. Using a thermal model to approximate the heating characteristics of silicon wafers, it is possible to determine the effects of time-varying intensity profiles on a wafer during a rapid thermal process. Interpretation of this model shows idealized intensity profiles can maintain thermal uniformity at steady-state temperatures. During thermal transients a dynamic continuously changing profile is required to maintain thermal uniformity. As a predictive tool, this analysis can be used to determine and evaluate dynamic uniformity producing intensity profiles before thermal transients occur within a process. This approach can reduce the accumulation of error during high temperature steps not only by providing thermal uniformity at steady states, but by reducing the initial nonuniformities produced by transitions. This paper will review the wafer model, show the results of an idealized profile for steady-state and transient temperatures, and explain the dynamic profiles required for continuous uniformity.