Overhead intrabay automation and microstocking. A virtual fab case study

As the need for higher efficiencies in semiconductor manufacturing intensifies, the importance of effective intrabay automation increases. Direct delivery overhead zero foot print intrabay automation, coupled with microstocking of WIP will be a means to maximize the throughput of fully automated fabs. Microstocking can be practically implemented in the following four ways. The first instance of microstocking is found on a process tool that has more than one Input/Output (I/O) port. Another form of microstocking is the internal tool buffer commonly found on vertical furnaces and wet processing benches. A third manifestation of microstocking is the OEM supplied small capacity WIP stocker, that is mounted directly to the front of a process tool. Overhead Zero Foot Print microstocking is the fourth choice, which uses ceiling mounted shelves integrated directly below the overhead intrabay vehicle systems. This paper is the result of investigating these automation concepts using discrete event simulation modeling. The fat, process system model is integrated with the automation system to yield insight into the effectiveness of microstocking and overhead automation. The industry generally agrees that 300 mm fabs will be highly automated; this case study explores some of the issues facing those who implement intrabay automation.