The high price tags of exposure tools have made the cost of lithography a concern since the advent of projection lithography, and lithography costs may ultimately limit patterning capability, more so than technical feasibility. While there will always be a market for electronics where price is secondary to performance, the large personal computer and portable phone markets have proven to be extremely elastic. To meet the demands of the consumer, lithography will need to be cost effective, in addition to providing technical capability. Lithography costs have several components. These include:
1. Capital equipment costs, throughput, and utilization
2. Consumables, such as photochemicals
4. Rework and yield
These factors can be considered in various degrees of sophistication. A detailed cost-of-ownership model was generated by SEMATECH, and an enhanced version of this model is commercially available. In this chapter, the basic components of such cost-of-ownership models are introduced and discussed.
Lithography tools are often the most expensive in the wafer fab. Even when they are not, the fact that lithography is required for patterning many layers in IC manufacturing processes, while most other tools are used for only a few steps, means that a large number of lithography tools are needed for each wafer fab, resulting in high total costs for lithography equipment.
Wafer steppers are the most expensive pieces of equipment in the lithography tool set. Their prices have increased by an average of 17% per year since they were introduced in the late 1970s, to the point where the prices for leading-edge step-and-scan systems now exceed $50M (Figs. 11.1 and 11.2).