Study for Realizing Effective Direct Tool-to-Tool Delivery

Direct tool-to-tool delivery is one of technical topics for excellent fab performance. Automatic material handling system (AMHS) vendors supply unified OHT systems that can provide direct tool-to-tool delivery routes. But providing such routes is not sufficient to realize direct deliveries. The purpose of our study is to identify remaining issues required to realize direct tool-to-tool delivery. Our conclusions are: (1) AMHS cannot realize direct tool-to-tool delivery by itself without any degradation of fab throughput, and (2) effective algorithms for lot scheduling/dispatching and variability reduction of tool process rate are required to realize it without such degradation