In semiconductor wafer fabrication, time constraints between process steps in furnace and wet etch make it difficult to achieve cycle time targets and maximize machine utilization. For capacity planning, it is difficult to estimate the impact of these time constraints on the machine capacity. Infineon Technologies Dresden has conducted a study using discrete event simulation, to investigate the actual situation in the factory and to identify recommendations to eliminate or to reduce the impart of time constraints. The work in this paper yields a two-day reduction in total cycle time after implementation of findings in the factory.