An efficient adaptive dispatching method for semiconductor wafer fabrication facility

Abstract

To cope with uncertainty in semiconductor wafer fabrication facilities (fabs), scheduling methods are required to produce quick real-time responses. They should be well tuned to track the changes of a production environment to obtain good operational performance. This paper presents an efficient adaptive dispatching method (ADM) with parameters determined dynamically by real-time state information of fabs. ADM is composed of a dispatching rule considering both batch and non-batch processing machines to obtain improved fab-wide performance, several feature selection methods to determine key scheduling-related real-time state information, and a linear regression model to find the relations between the weighting parameters of the dispatching rule and the determined real-time state information. A real fab simulation model is used to demonstrate the proposed method. The simulation results show that ADM is adaptive to changing environment with better performance than a number of commonly used rules (such as FIFO, EDD, CR, LPT, LS, SRPT, and SPT) and an adaptive dispatching rule that considers only real-time ratio of hot jobs to the number of all jobs in a fab and the ratio of jobs with one third of photo steps left to the number of all jobs.