Combination bottlenecks in full automated fab and its countermeasures

In a full-automated bay, there are cases that the bay cannot work with enough throughputs even though both production machines and AMHS(Automated Material Handling System) has enough capacities. This bottleneck results from a combination of production machines and AMHS. We call the phenomena "Combination bottleneck". First, this paper describes the concept of "combination bottleneck" by using simple bay model. Then it shows an example of combination bottleneck that is observed in more realistic simulation model. This model includes stockers, OHT (Overhead Hoist Transport) system and production machines. Finally, this paper discusses some countermeasures to remove this bottleneck.