Improving preventive maintenance scheduling in semiconductor fabrication facilities

The complexity of modern semiconductor manufacturing processes and the need for realistic considerations when modelling their short term availability and reliability make it very difficult to use analytic methods. In this paper, we review the process of preventive maintenance planning and shop level maintenance scheduling in semiconductor fabrication facilities (fabs). We show that the use of Monte Carlo continuous time simulation modelling to improve preventive maintenance scheduling allows the assessment of alternative scheduling policies that could be implemented dynamically on the shop floor. Using a simulation model, we compare and discuss the benefits of different scheduling policies on the status of current manufacturing tools and several operating conditions of the wafers production flow. To do so, we estimate measures of performance by treating simulation results as a series of realistic experiments and using statistical inference to identify reasonable confidence intervals.