Work-in-process control in a continuous-flow manufacturing line

During the past year, IBM's semiconductor manufacturing facility in Essex Junction, Vermont, has made a transition from business as usual to continuous-flow manufacturing (CFM). This transition made the traditional tools used for line control ineffective and required new and more creative ways of managing work in process (WIP). This facility manufactures high-volume logic and numerous chips with multiple part numbers. There are many technologies which share tools and processes. The authors describe the system developed to control WIP in such a facility. During the last two years, cycle times have decreased, and wafer final test yields have improved. Outs per operator have more than doubled as a result of productivity improvements. Customer weekly and monthly serviceability for both volume and part-number mix has improved significantly. The number of late lots in the line has decreased as a result of CFM and WIP control actions