Medium-term multi-plant capacity planning problems considering auxiliary tools for the semiconductor foundry

The foundry is an industry whose demand varies rapidly and whose manufacturing process is quite complicated. This paper explores issues on mid-term capacity planning in the foundry. First, issues on capacity planning of the foundry are categorized. Second, focusing on multi-site planning, an increment strategy for the number of auxiliary tools—“photo mask”—is proposed to increase the flexibility of production. The related decisions include how to allocate appropriately the forecast demands of products among multiple sites and how to decide on the production quantities of products in each site after receiving customer-confirmed orders. By constructing the mathematical programming model of capacity planning, the rates of capacity utilization and customer order fulfillment are found to be effectively enhanced by adding new masks to increase production flexibility. Furthermore, from the sensitivity analysis, the importance of customers is shown to influence significantly the amount of reserved capacity of customers. Increasing the number of certified factories is also an indirect way to increase capacity. For long life cycle products, the verification of products in multiple factories in order to increase capacity utilization rate effectively is suggested.