Project Abstract:
The problem of scheduling semiconductor wafer fabrication facilities
(wafer fab) has been considered to be one of the most important
scheduling problems. Of particular interest is the presence of batch
processing machines (BPMs) within the wafer fab such as oxidation
furnaces. A batch processing machine is defined as a piece of
equipment that has capacity greater than one. Due to their long
processing times and ability to act as a situational bottleneck, the
manner in which BPMs are scheduled can have a very strong
influence on system performance. However, little work has been
done on scheduling BPMs in the context of it being part of an
entire wafer fab system; majority of research on scheduling wafer
fabs ignore the presence of BPMs. Although the problem of
scheduling BPMs has attracted greater attention from researchers,
majority have considered truncated systems involving BPMs; these
generally come in the form of heuristics. This heterogeneity between
the existing literature regarding scheduling wafer fabs, and
scheduling BPMs, is a critical gap in the existing literature that this
project proposes to address. It is anticipated that explicitly modeling
the potential impact of BPMs on the quality of a particular schedule
for a wafer fab will lead to the development of a feasible scheduling
algorithm that improves upon industry’s current best practices.
Prior to determining the potential impact of the BPM on a complex
manufacturing system is, an analytical characterization of the BPM
in the presence of other serial processors is required, for several
reasons. By analyzing the phenomena associated with scheduling
a small system with a BPM, a deeper understanding of the
relationships between the BPM and its upstream and downstream
processors can be obtained. Such an understanding would then
allow for the formulation of policies that can control serial processors
with overall improvement of the scheduling quality for the
entire system in mind. This is a marked departure from previous
look-ahead methods. This shift in scheduling philosophy, from a
reactive to a proactive approach, is expected to yield significant
improvement in schedule quality over previous look ahead methods. |