이태억 교수

We introduce places with negative holding times and tokens with negative token counts into a timed event graph in order to model and analyze time window constraints. We extend the enabling and firing rules for such an extended event graph named a negative event graph (NEG). We develop necessary and sufficient conditions based on the circuits for which the NEG is live, that is, an infinite sequence of feasible firing epochs exist for each transition. We prove that the minimum cycle time is the sa

Cluster tools, which combine several single-wafer processing modules with wafer handling robots in a closed environment, have been increasingly used for most wafer fabrication processes. We review tool architectures, operational issues, and scheduling requirements. We then explain recent progress in tool science and engineering for scheduling and control of cluster tools.

Cluster tools, which combine several single-wafer processing modules with wafer handling robots in a closed environment, have been increasingly used for most wafer fabrication processes. We review tool architectures, operational issues, and scheduling requirements. We then explain recent progress in tool science and engineering for scheduling and control of cluster tools.

This paper discusses the periodic job shop scheduling problem, a problem where an identical mixture of items, called a minimal part set (MPS), is repetitively produced. The performance and behavior of schedules are discussed. Two basic performance measures, cycle time and makespan, are shown to be closely related. The minimum cycle time is identified as a circuit measure in a directed graph. We establish that there exists a class of schedules that minimizes cycle time and repeats an identical ti

A wet station performs a cleaning process in semiconductor manufacturing. It consists of several processing baths and multiple wafer-handling robots. It simultaneously processes multiple wafer types with different processing sequences. Robot collisions and deadlocks should be prevented. There are also strict no-wait time constraints where, after a wafer is cleaned in a chemical bath, it should immediately be removed from the bath and rinsed at a water bath. We examine the scheduling problem when

As the design of integrated circuits has become increasingly complicated and dense, serious wafer quality problems are observed in modern wafer fabrication facilities. Therefore, in cluster tools of leading fabs process chambers are periodically cleaned in order to eliminate residual chemicals and impurities that can damage the wafer quality. A chamber cleaning operation is mainly applied to tools in which a wafer delay has a crucial impact on the wafer quality, and hence the need of wafer delay