Title :
Petri Net-Based Scheduling of Single-Arm Cluster Tools With Reentrant Atomic Layer Deposition Processes
Author :
Wu, NaiQi ; Chu, Feng ; Chu, Chengbin ; Zhou, MengChu
Author_Institution :
Dept. of Ind. Eng., Guangdong Univ. of Technol., Guangzhou, China
Abstract :
For some wafer fabrication processes in cluster tools, e.g., atomic layer deposition (ALD), wafer revisiting is required. Typically, in such processes, wafers need to visit two consecutive processing steps several times. Such a revisiting process can be denoted as (mi, mi + 1)h, where i means the ith-step and mi and mi + 1 mean the corresponding quantity of the processing modules in i and (i+1)th steps, and h the number of visiting times. This paper conducts a study for scheduling single-arm cluster tools with such a wafer revisiting process. The system is modeled by Petri nets (PNs) to guarantee the feasibility of robot activities. Based on the model, a deadlock avoidance policy is presented. With the control policy, cycle time analysis for the revisiting process is made. With the fact that wafer processing times are much longer than robot movement times in cluster tools, it is shown that, when mi = mi + 1 = 1, i.e., each step has only one processing module, the optimal one-wafer cyclic schedule 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 can be obtained by finding h deterministic schedules and the one with the least cycle time. A novel analytical method is finally presented to schedule the overall system containing such reentrant wafer flow. This represents a significant advance in single-arm cluster equipment automation.
Keywords :
Petri nets; atomic layer deposition; cluster tools; industrial robots; modules; optimisation; scheduling; semiconductor device manufacture; wafer level packaging; Petri net-based scheduling; cycle time analysis; deadlock avoidance policy; optimal one-wafer cyclic schedule; reentrant atomic layer deposition process; reentrant wafer flow; robot activity; semiconductor fabrication; single-arm cluster equipment automation; single-arm cluster tool; wafer fabrication process; wafer revisiting; Atomic layer deposition; Automation; Educational programs; Fabrication; Job shop scheduling; Manufacturing processes; Partial response channels; Petri nets; Robots; Semiconductor device modeling; Cluster tools; Petri nets (PNs); optimization; scheduling; semiconductor fabrication;
Journal_Title :
Automation Science and Engineering, IEEE Transactions on
DOI :
10.1109/TASE.2010.2046736