Heuristic simulated annealing approach for diffusion scheduling in a semiconductor Fab

This paper presents an efficient algorithm for diffusion scheduling in a semiconductor fab. The diffusion area commonly creates long queue time in the entire process flow. Due to the complex constraints, such as parallel batching and time windows, and large solution space, it is difficult to find a feasible schedule in a timely manner. A greedy randomized procedure forms the batches. A heuristic method is introduced to handle the time window constraints. Two important properties of the problem are identified and applied to improve the quality of the solution. Simulated annealing is used as a local search procedure. Compared with the real schedule in the fab, the proposed algorithm can increase the effective moves significantly without violating queue time constraints.