Strategy for Using Run to Run Control in a High Product Mix Environment

摘要

Run to Run Control works best when there is a lot of recent data that relates directly to new lots. High product mixrnfabrication facilities (fabs) do not provide this data. This is especially true of the photolithography area where everyrnproduct is run with a different recipe and reticle at the same process step. In these fabs, it is possible to group productsrnthat run using the same process flow (series of process steps) or technology and feedback from information from onernproduct to the processing of another. This grouping strategy should involve a multi-tiered approach in which the firstrnattempt to derive run to run settings should be done using data from the same product and equipment only. If there isrnnot enough data to accurately derive settings from this data, then some sort of minimal product grouping should bernattempted. If there still is not enough data, then the system should further expand the group of data that it uses tornderive the run to run settings. This cycle of loosening the criteria and recalculating can continue as many times asrnrequired but suffers from diminishing returns. This strategy has been successfully employed in an environment withrnover 200 different product. In this case, the run to run strategy iterated the gather data and calculate cycle three times.rnThe first time it always used product specific data but the second and third cycles where configurable by device andrnprocess step. The options included continuing with device specific information or using one of a group of over 18rngroups or one of a group of over 10 processes flows. These process flows include flows for CMOS semiconductors,rnbipolar semiconductors, Bi-CMOS semiconductors, and MEMS products. Even with such a large variation of product,rnthe run to run control system has realized great success in capacity improvement, process control, cycle time, andrnrework reduction.