Transient processes analysis for single-arm cluster tools with different structures

Abstract

Numerous studies of cluster tool operations in steady state have been published in the field of wafer manufacturing. However, as wafer batch sizes decrease, more transient processes are generated such that tools should switch from processing one wafer to another wafer and the transient processes should be completed as quickly as possible. Besides, constraints on wafer residence time are pivotal and indispensable to practical wafer manufacturing processes. The generalized backward strategy is suitable to solve the transient scheduling problem with time constraints. So in this paper we discuss the transient process scheduling of single-arm cluster tools with two different structures, independent process modules and parallel chambers. Main procedures are the development of Petri Net models, the proposition of control policies and shcedulability conditions, the derivation of linear programming. Examples with specified activity time units explain activity sequences and the corresponding time sequences. Index Terms—Single-arm cluster tools, transient process, Petri Net, process module, parallel chamber, scheduling.