Research On Hot Lots Scheduling Of Semiconductor Wafer Fab

In semiconductor industry, hot lots are often introduced into manufacturingsystem. The hot lots in semiconductor wafer fab systems are well known tosignificantly affect the cycle time and impact the work in process of regular lots, dueto the high priority at all stages of processing. However, there is only few studies forhot lots analysis, most of them only give simulation investigations. In real plants, themethodology of hot lots scheduling is based on experiences. Research on hot lots isvery important for the production management in semiconductor manufacturingdomain.This paper describes computational experiments followed by discussion on theimpact of hot lots. Some schedule and release policy of hot lots are presented later,and finally a discussion on the application of hot lots in optimizing control is given.The achievements of this dissertation include:1. To present some computational experiments on hot lots, and analyze the resultof the simulation.2. A formal definition of "hot grade" is given, and a modified ranking(MR) schedulingpolicy is presented which has global influence on all kinds of product.3. To present a dynamic bottle neck identification algorithm: EDBI. The simulation prove theefficiency of the algorithm.4. Based on the theory of constrains(TOC) and theory of stability, this paper present a TOCbased release policy to control the release process of hot lots.5. A multi-Agent system is established to handle the scheduling of hot lots.6. Some further discussion on the scheduling of batch device is given, using the concept ofhot grade and MR policy.