A study on the lot production management in a thin-film-transistor liquid-crystal display fab

Because of their higher processing priority, hot lots often interrupt the production of regular lots in a Thin-Film-Transistor Liquid-Crystal Display (TFT-LCD) fab. As a result, how to manage the production of hot lots so that their production demand can be met and their negative effects on regular lots minimized is a very important issue. In this paper, we identity three problems - the lot selection of interbay AGVs, the lot selection of intrabay machines, and the photo bay selection of lots - that can affect the production of hot lots and regular lots and propose methods for them. A fuzzy-based dynamic bidding (FBDB) method is proposed for the first two problems. The bidding functions in this FBDB method consider several attributes of the current system to obtain the true values of bids. An earliest possible time (EPT) method that also considers several attributes of the current system is proposed for the third problem. These two methods are compared with methods used by a Taiwanese TFT-LCD fab through computer simulations. The effects of hot lot ratios on the performance of these methods are also analyzed. Six performance measures are adopted to measure the throughput and tardiness performance of all lots, regular lots and hot lots. The simulation results show applying the FBDB and EPT methods to the three problems studied here can result in very good results in all performance measures.