The Relay Coach - Implications

Next, the Relay Coach looks further at the other lots that were processed on the Wet Etch4 tool group, to understand why these lots may have been processed instead of Lot #2101. The chart below shows a pareto of lot moves on the Wet Etch4 tool group by priority class. All four of the lots (all 94 wafers) had priority class 1, the same priority class as Lot #2101.

The Relay Coach next views a list of which lots were in queue when Lot #2101 arrived. The chart below shows the six lots in queue for Wet Etch4, immediately after Lot #2101 arrived (a seventh lot was in process on Wet Etch4#2. The Relay Coach verifies that all four of the lots that were processed on Wet Etch4 tools were already in queue or in process when Lot #2101 arrived.

Conclusions and Recommendations

The Relay Coach has thus verified that priority class rules were followed on the Wet Etch4 tool group. When Lot #2101 arrived, there were four other lots already in queue that had the same priority, and these lots were processed prior to Lot #2101. The Relay Coach concludes that the appropriate dispatch rules were followed on the Wet Etch4 tools, but that Lot #2101 had to wait five hours to be processed because one of the two Wet Etch4 tools was taken up by engineering time. Recommendations that the Relay Coach might make in this situation include:

Reducing dedication on the Wet Etch tools (so that instead of a group of two tools, hot lots would require one of a larger number of tools).

Reducing engineering on the Wet Etch4 tools, perhaps by arranging for the engineering to be done on other Wet Etch tools.

If Lot #2101 is in fact more critical than the other lots that were processed on the Wet Etch4 tool, then the situation calls for some sort of super-expediting procedure (see below).

For a description of a procedure for super-expediting lots, see the paper: M. Hillis and J. K. Robinson, “Super-Expediting in a 0.18 Micron Wafer Fab,” Proceedings of the 2002 Modeling and Analysis for Semiconductor Manufacturing Conference (MASM 2002). Tempe, AZ, April 10-12, 2002. (Abstract).

Return to the main cycle time management styles page.