Scheduling Transient Period of Cluster Tools to Reach a Steady Schedule
<Speaker: 김우진 박사과정, 이태억 교수님 연구실>
Date & Time: 11월 28일(화), 4:00pm~
Title: Scheduling Transient Period of Cluster Tools to Reach a Steady Schedule
When wafers are fabricated in cluster tools, a wafer may wait within a chamber after being processed there. Such wafer delays are detrimental to the wafer quality due to residual gases and heat inside the chamber. Thus, there arise significant wafer quality issues when a tool is in a transient state in which the wafer delays fluctuate severely. Therefore, it is desirable to maintain the tool operational schedule steady as possible. However, it may not be possible for a tool to be in steady states after a random disruptive event such as a chamber breakdown or robot operational failure. As a result, we face an important scheduling issue to minimize the duration of a tool being in transient states. In this paper, we develop a method of scheduling cluster tools after a random disruptive event, in order to make the tool reach a steady state efficiently. To do this, we model the behavior of a cluster tool using Petri nets, and examine their linear system matrices based on max-plus algebra. We then verify which initial states, given after the disruptive event, could automatically reach a steady state. In addition, when a given initial state cannot reach a steady state automatically, we propose a timing control method to make such tool state efficiently enter a desirable steady state. Finally, we present computational examples to show how the time duration of transient states can be minimized.
Place : 2504, edu3.0 강의실