Storage prioritization by redistributing wafer lot transfers to enhance real-world fab throughput

Although efforts to improve the productivity of semiconductor fabs have mostly focused on processing machine scheduling, recent productivity drops due to insufficient automated material handling system (AMHS) resources have made the efficient control of AMHS a major issue in improving overall productivity. This study introduces a storage prioritization procedure (SPP) for the effective allocation of work-in-process (WIP) to storage devices is applied to a real-world 300 mm fab. The proposed SPP utilizes a minimum-cost flow-based model to generate priority lists of storage devices for wafer lot transfers after determining the push or pull strategy for each machine group. Experimental studies are conducted according to four simulation scenarios that demonstrate the superior performance of the SPP. The field application results verify the SPP performance in the real-world fab. The productivity improvement due to the SPP is estimated to be tens of million dollars during the two months of the study period.