Using Rotacaster in the Heuristic Preemptive Dispatching Method for Conveyor-Based Material Handling of 450 mm Wafer Fabrication

Semiconductor industry today is facing the transition from 300 to 450 mm wafer fabrication. However, the 450 mm wafers will pose challenges on handling and transport due to the increased size and weight. As the overhead hoist transport (OHT) system, which has been widely used in 300 mm wafer fabs, is likely to phase out, researchers have suggested using conveyor-based automated material handling systems (AMHSs) for 450 mm wafer fabrication. However, to best operate the AMHSs in a 450 mm wafer fab, effective dispatching methods that can best address the two critical problems: 1) traffic-jam and 2) lot prioritization, in the shop floor are required. In this research, we have proposed a heuristic preemptive dispatching method using Rotacaster (R-HPD) to operate the AMHS for 450 mm wafer fabrication. The R-HPD method includes some effective dispatching rules to control and dispatch wafer lots in the AMHS. Our simulation results showed that the R-HPD outperformed the differentiated preventive dispatching policy in terms of average lot delivery time (ALDT). The improvements of 49.8% and 61.9% of ALDTs for hot lots and normal lots were observed, respectively.