Staffing analysis tool for operator-machine-lot interference in semiconductor manufacturing

This paper describes the concepts underlying a new staffing tool, which evaluates staffing requirements, plan future shift sizes, perform sensitivity analysis, and locate and measure improvement opportunities in terms of worker operations. The model is based on M/M/S/K queuing theory to analyze the operator-machine-lot (OML) interference especially in semiconductor manufacturing processes. Unlike classical approaches, in which the machines are treated as customers, here wafer lots are taken as the designated customers to be serviced. A comparison of a simulation, OML, and a traditional M/M/S/K model (where the machines are modeled as customers) shows that OML model yields much closer results to the simulation than the traditional M/M/S/K model. Furthermore, from the computational point of view OML is more efficient than the simulation model which can be very time consuming especially in the complex semiconductor manufacturing environment. Thus, OML model is a superior alternative to the classical interference modeling and facilitates staffing recommendations that improve overall equipment effectiveness (GEE) and therefore productivity.