Characterizing the Worst-Case Wafer Delay in a Cluster Tool Operated in a K-Cyclic Schedule

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Cluster tools are widely used manufacturing equipment in semiconductor manufacturing systems and consist of several process chambers, loadlock modules, and a wafer transport robot. The operation of the cluster tool relies on decision making about the robot operations. Generally, a robot iteratively determines its next task according to a given task sequence. This tool schedule is called a cyclic schedule. If the same timing pattern repeats every K work cycles in a cyclic schedule, the schedule is called a K -cyclic schedule. In a cluster tool with a K -cyclic schedule, wafer delay, which is the time that a processed wafer is stored in the process chamber, becomes an important issue. In this study, we identify the worst-case wafer delay, which is the maximum value of wafer delay among all the K -cyclic schedules a cluster tool can have. To do this, we present timed event graph models for dual-armed and single-armed cluster tools and briefly explain the previous research on closed-form formulae of token delays in timed event graphs with K-cyclic schedules suggested by Lee et al. [1]. Finally, we propose a method for deriving a closed-form formula for the worst-case wafer delay in a cluster tool, which can be applied to arbitrary wafer flow patterns and time parameters.
Publisher
IEEE
Issue Date
2018-08
Language
English
Citation

2018 IEEE 14th International Conference on Automation Science and Engineering (CASE), pp.1562 - 1567

DOI
10.1109/coase.2018.8560521
URI
http://hdl.handle.net/10203/272740
Appears in Collection
IE-Conference Papers(학술회의논문)
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