Technology that upsets the social order — a paradigm shift in assigning lots to tools in a wafer fabricator — the transition from rules to optimization

Historically the dominant decision technology to make dispatch decisions was ¿rules¿ which involves the following basic computational mechanisms: merge, select, sort, and if/then/else in a decision tree. Although rules do a reasonable job they fundamentally lack a robust ability to: (a) look across time, (b) look across tools at a tool set, (c) create an anticipated sequence of events at a tool set over some time horizon, (d) establish a formal metric and (f) search alternatives. However, standard wisdom was the rapid pace of change and short time interval between dispatch decisions precluded the use of optimization to build dispatch applications. Although this barrier was legitimate in the 1980s and most of the 1990s based on limitations in hardware and software (algorithms); the real barrier today is cultural; not technical. From 2004-2007, IBM and ILOG jointly worked to deploy the ILOG optimization product FPO to key tools sets in IBM¿s 300 mm fab resulting in substantial improvements in performance and significantly reduced overhead to adapt to changing circumstances. This paper will cover the fundamentals of the paradigm shift.