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A hybrid multi-cluster tool is composed of both dual and single-arm robotic tools. Since their behavior is different, it is very challenging to coordinate their activities in such a tool and to schedule it optimally. This work aims at finding such a schedule for a treelike hybrid multi-cluster tool whose bottleneck tool is assumed to be process-bound. Resource-oriented Petri nets are extended to model...
High-mix and low-volume wafer fabrication leads to more and more lot switches in cluster tools. Practitioners must thus deal with more transient processes during such switches, including start-up and close-down. To obtain higher throughput, it is critical to shorten these processes. Much effort has been put into the steady state modeling and scheduling of cluster tools and some for start up processes...
Based on the systems of simple sequential processes with resources (S3PR) model, the existing methods involve prohibitive computation to synthesize a deadlock prevention controller for automated manufacturing systems (AMS). To reduce the computation, this work studies this problem by using a resource-oriented Petri net (ROPN) model. By revealing the relationship between bad markings and structural...
It has been shown that, for dual-arm cluster tools with wafer revisiting, a swap strategy may not be optimal. To improve the performance of such a system, a Petri net model is developed in this work. Based on it, dynamical behavior of the wafer production process is analyzed. Then, two new scheduling methods called 2-wafer cyclic schedules are presented. Cycle time analysis shows that, under some...
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...
For time-constrained cluster tool in semiconductor manufacturing, activity time variation can make an originally feasible schedule infeasible. With bounded activity time variation considered, this paper addresses their real-time scheduling issues and conducts their schedulability analysis. With Petri net (PN) model and a real-time control policy, this paper derives closed form schedulability conditions...
This paper conducts a study for scheduling single-arm cluster tools with typical wafer revisiting pattern (mi, mi+1)k where i means the ith-step and mi and mi+1 mean 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,...
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