Review for Scheduling Algorithms on a Fab Manufacturing System with Special Characteristics Called As Re-Entrant Flows

Scheduling is very important issue in manufacturing systems such as large-scale complex manufacturing system. Especially, in semiconductor manufacturing system, the complexity of scheduling is very high since there are various constraints such as re-entrant flows, limited waiting time, equipment dedication and so on. There are many researches for scheduling algorithms or dispatching rules on the semiconductor manufacturing systems, however, there are few researches for the scheduling algorithms considering the above special characteristics such as re-entrant flows of lots, limited waiting time of lots, equipment dedication for operations of photolithography and so on. In this paper, we focus on and review the previous scheduling algorithms or dispatching rules for the re-entrant flowshops of various types in a semiconductor manufacturing system, and suggest the needed future research areas for the scheduling problems with special constraints in a semiconductor manufacturing system.

Introduction:-

In order to survive in today’s business environment, which can be characterized by frequent technological changes, uncertain demands, and short life cycles of products [1], it is necessary to achieve high system performances in terms of throughput rate and service level by implementing efficient and effective planning and scheduling methods [2]. Particularly, in electronics industry, such operational decision are very important, since product variety and complexity of manufacturing process as well as capital expenses have increased due to the high degree of automation and versatility [3]. In fact, many traditional industries, such as textile and mirror industries, have manufacturing systems that can be regarded as re-entrant flowshops [4]. In addition, the re-entrant flowshops can be found in the electronics manufacturing systems like those for PCB (printed circuit board), TFT-LCD (thin film transistor liquid crystal display) and semiconductor manufacturing [2]. In this paper, we review the related existing researches for reentrant flowshop scheduling problems. Re-entrant flowshop can be considered as an extended form of flowshop, that is, re-entrant flowshop has a flow line like flowshop but there are reentrant flows [2]. In a typical flowshop, jobs are composed of m (number of machines) operations at most and each job visits each machine one time. However, in re-entrant flowshops, jobs should visit machines multiple times. In other words, jobs should go through multiple passes (L) of serial manufacturing processes. In the m-machine (m≥2) re-entrant flowshop, each job should be processed L (≥2) times on each machine, that is, one time or multiple times and hence each job is composed of Lm operations. Figure 1 shows a schematic view of a re-entrant flowshop.