The measurement of wait time in non-productive process of process units — Chieh-yuan Tiao

Ever since 2007, time waste became an industry-wide topic. In 2011 [ITRS] - roadmap, waste reduction was introduced as an important topic for the requirement of future manufacturing. WTW (wait time waste) then became a formal project in ISMI. Fundamental definition and methodology was developed to systematically measure time consumption and expose time waste for a product during its factory life cycle.The ISMI developed WTW method mainly focus on wafer-based factory data collection, which convert continuous tool events along specific wafer into independent record for each wafer (Fig.1). However, certain non-productive activities (wafer-less clean, pre/post process chamber condition, ... ) which processed without wafer are frequently occurred in factory´s daily operation. Without taking these non-productive process into consideration, miscalculation of wait time waste is expected. And in certain worse case, a conflict of measurement may take place in tools with unique non-productive process. By introducing an optimized wafer categorizing and time element definition methodology, the non-productive process can successfully be identified and measured. That will improve the accuracy of the calculation/estimation in time waste as well as material waste between productive and non-production ratio, and eliminate the possibility of conflict generating.generating.