Cycle time reduction via machine-to-operation qualification

In the utopian factory every machine in a workstation would be qualified to perform every operation supported by that workstation (e.g., able to run every associated photolithography layer of the semiconductor wafer fabrication process). In real world factories this is unlikely to be either practical or even feasible. As a consequence, one of the more vexing problems involved in determination of factory configuration and operation is that of deciding which operations are to be run on what machine, so as to optimise overall factory performance. In this paper the decision of the allocation of machine-to-operation qualifications in a semiconductor wafer fabrication photolithography workstation is employed to illustrate this problem. Factory performance, as achieved by both conventional and optimal means, is compared via simulations of a model of a semiconductor wafer fabrication facility. The improvement, in factory performance–and estimated cost savings–was found to be substantial.