Completion Time Analysis for Automated Manufacturing Systems with Parallel Processing Modules

This paper analyzes the completion time of automated manufacturing systems, especially a dual-armed cluster tool, equipped with parallel processing modules (PMs). Cluster tools, which consist of multiple PMs, a transport robot, and loadlocks where wafer lots are loaded and unloaded, perform semiconductor manufacturing processes, such as lithography, etching, deposition, and testing. Wafer lots are transported by overhead hoist transports (OHTs) between tools or stockers where wafer lots are stored. To reduce the idle time of OHTs or cluster tools, it is essential to estimate the time when all wafers of a lot finish processing in a tool. Hence, we derive closed-form expressions for the completion time of wafer lots, especially in dual-armed cluster tools with parallel PMs to reflect real circumstances of fabs. We finally show that the formulas derived can be used even when there are small processing time variations with numerical experiments.