Approximation of the Cycle Time of Cluster Tools in Semiconductor Manufacturing

In today's 300mm wafer fabrication facilities, large parts of the lot processing are performed in cluster tools. Cluster tools are machines where a number of process chambers are attached to a main frame containing a transport robot. In contrast to traditional single process tools it is possible to load cluster tools with more than one lot, even with lots from different products. As a consequence, the cycle time of a lot depends considerably on the lot type that is processed in parallel. Thus, the complexity of production planning and shop floor control is increased. The exact cycle time can usually only be assessed by simulation. To avoid time-consuming simulation runs we present several approaches on how to approximate the tool cycle time of lots.