A Practical Two-Phase Approach to Scheduling of Photolithography Production

The introduction of real-time dispatching (RTD) to semiconductor manufacturing has greatly improved productivities for the last two decades. Recently, researchers have revealed that data available and complexity of the algorithms to the dispatcher are limited-in effect the dispatcher has tunnel vision, dutifully rank ordering the lots in the queue, but oblivious to what is happening around it, which leads to the poor results compared to other modern optimization-based approaches. However, the author admits that most semiconductor manufacturing companies are still using RTD not only as a last-minute loading-check, but also as a scheduling logic-hub. Here comes a business need of improving the brainpower of RTD by using the optimization technologies. In this paper, we propose an integration of RTD with linear programming technique in photolithography area by using two-stage modeling. The transportation model at the first stage finds the least-cost means of assigning jobs to reticles and machines. Then, the sequencing module provides an expository sequencing decision by inheriting the same dispatching business rules. The experimental study demonstrates the proposed method can reduce the count of reticle delivery by 40.5% in a low-mix fab instances.