Development of a state-dependent dispatch rule using theory of constraints in near-real-world wafer fabrication

Multiple response optimization in a fully automated FAB: an integrated tool and vehicle dispatching strategy∗

“…Two tool-related state variables are identified, according to the Theory of Constraint scheduling principle (Tyan et al, 2002), which indicates that processing tools are the constraints resources of a wafer fab. The first state variable, tool utilization ðu t Þ; is measured by the ratio of accumulated processing time to total operating time in any given time interval.…”

“…In 1994, Leachman (1994) and Uzsoy, Lee, and Martin-Vega (1994) reviewed scheduling practices across semiconductor industries. Later studies (Hung & Chen, 1998;Mittler & Schoemig, 1999;Sturm, Frauenhoffer, Dorner, Kirschnhofer, & Reisinger, 1999;Tyan, Chen, & Wang, 2002) applied simulations to analyze the effects of combining a set of dispatching rules. These studies indicated that there was no optimal dispatching rule for any given application, and suggested that the selection of a dispatching rule was dependent on performance objectives.…”

“…Whereas most dispatching studies are concerned with a single performance measure with a reduced fab model, Tyan et al (2002) proposed a state-dependent dispatching methodology that combines multiple tool-dispatching rules into a single tool-dispatching rule with the objective of optimizing multiple performance measures simultaneously. This study extends their proposed state-dependent dispatching approach by including vehicle dispatching in an integrated dispatching rule.…”

“…A two level 1/4 fractional factorial design (Montgomery, 2001) was used to investigate the main effects and identify the most favorable dispatching combination. The selection of the dispatching rule sets was based on the study of Tyan et al (2002). The performance measure of each experiment was based on the average batch mean that was collected from the simulation output statistics.…”

TOC'S Five-Step Cycle: An Approach to Instant Results and Cultural Change

“…Tyan et al [36] suggest that the principles of TOC are effective tools for continuous improvement of a process. From the satisfactory results, the continued use of this tool is already shaping a new culture at the factory, allowing gains in productivity and profit, as can be seen in Figure 8.…”