OPTIMIZATION OF LIFTER OPERATIONS FOR INTER-LINE TRANSFERS IN SEMICONDUCTOR MANUFACTURING FACILITIES

As semiconductor processes continue to be complex and the number of production steps is increased, a single floor line often comes to have not enough capacity to cover such production. Therefore, in recent years, multiple floors or multiple lines have been combined into a single Fab and this increases inter-floor (or inter-line) delivery. This increase in inter-floor delivery leads to a bottleneck, causing significant production loss. In this paper, we proposed operation policies of inter-floor delivery such as virtual ports, alternative storage, and shelf extraction procedure. In addition, the operational policy was examined through simulation experiments that can maximize the efficiency of inter-floor delivery. It has been found that having two or three virtual ports is the most efficient and activating the alternative storage option has the advantage of increasing the availability of the in-port. This paper focused on the actual problem that occurred in practice, and the results of this study can contribute to improving the efficiency of lifter operations in material handling of semiconductor lines.