Cycle time reduction at Motorola's ACT fab

This paper deals with the application of theory of constraints (TOC) and simulation to fab cycle time reduction at Motorola's Advanced Custom Technologies (ACT) fab. The cycle time crossfunctional team with the goal of transferring technology rapidly, keeping in mind customer satisfaction, underwent training in the basic theory of constraints, performed benchmarking, developed custom cycle time reports and developed techniques to measure theoretical cycle time and used multiples of theoretical cycle time as a basis to compare the performance of the wafer fab's actual cycle time (this metric is used in addition to the other fab metrics like, Turns/WIP for measuring the fab performance). Since ACT is a development fab, provision was made in the study, to include varied product mix, reentrant flows, optimized WIP, a typical hold in the process, etc. Engineering judgments coupled with simulation techniques were used to identify the constraints and these constraints were classified as physical and procedural and were treated accordingly by the team. The team evaluated each constraints and devised solutions based on TOC to reduce the fab cycle time.