An optimal scheduling technique for dual-arm cluster tools with buffer modules

In a cluster tool where process modules have residency constraints, an optimal schedule may need to buffer the partially processed wafers. In previous approaches, one of the active resources (i.e. the transport module) was used as a temporary buffer. In this approach we try to use a resource that is usually available in cluster tools and is only used for tool maintenance reasons. This passive module that we refer to as buffer module, can hold the partially processed wafers, and free the transport module (TM). Our experiment shows that in 57% of the cases, because the TM can perform other actions while the wafer is buffered in the buffer module, a schedule with better throughput was found