A novel approach to scheduling of single-arm cluster tools with wafer revisiting
Naiqi Wu, Feng Chu, Chengbin Chu, MengChu Zhou · 2009
This paper conducts a study for scheduling single-arm cluster tools with typical wafer revisiting pattern (mi, mi+1)kwhere i means the ith-step and miand mi+1mean the corresponding quantity of the modules in i and i+1-th steps, and k the number of visiting times. With a Petri net (PN) model, it is shown that, mi=mi+1=1, the optimal schedule for the revisiting process is deterministic and unique, and the minimal cycle time can be calculated by an analytical expression. It is also shown that, when mi= 1 and mi+1= 2 or mi= 2 and mi+1= 1, the optimal one-wafer cyclic schedule for the revisiting process can be obtained in k deterministic schedules by comparing their cycle times. Based on the scheduling and cycle time analysis of a revisiting process, a novel method is presented to schedule the overall system by treating the revisiting process as a macro step.