Modeling and Scheduling Stepper Operations in the Photolithography Process in Wafer Fabrication

Increase in the use of computers and hi-tech gadgetry have boosted the semiconductor manufacturing industry tremendously over the past decade. At the same time, exponential rates of growth and innovation combined with cutthroat competition are putting tremendous pressure on the industry to improve manufacturing practices and reduce costs. With considerable existing work in the modeling, simulation and optimization of actual physicochemical operations, it has been estimated that major improvements in the productivity of semiconductor industry lay in the higher-level systems engineering research involving the planning, scheduling, and optimization of semiconductor manufacturing processes. However, the semiconductor industry is quite different from the more traditional manufacturing operations such as assembly lines or job shops. Features such as re-entrancy, resource constraints, and uncertainties make this industry a highly complex process system that is difficult to schedule.