In semiconductor manufacturing, we expect the cause of defects to be process or tool related. However, at the 90 nm technology node and beyond we find that defects can be caused by issues related to the wafers' environment, such as processing of other wafers in the same tool or in the same carrier, or by seemingly innocuous actions. We pay special attention to the role of the mini-environment, which is deemed essential to achieving low particle counts for advanced technology nodes. We show defects that are caused by the environment, and some which are specifically related to the use of the mini-environment. We discuss several ways to reduce the sensitivity to environmental factors. Process and tool changes are found that eliminate yield detractors. We also present a workaround that has helped reduce the impact of queue time restrictions on cycle time.

Nitrogen purge of wafer carriers is driving defect density reduction at critical process steps. We discuss several examples of defect creation related to the environment of the semiconductor wafer and how nitrogen purge of carriers improves defect density. We have applied nitrogen purge at the gate formation, SiGe epitaxy and silicide formation process steps and we report experimental split data from in line inspection and the result at electrical test. From the impact of the nitrogen purge we can draw conclusions about the nature of defect formation. The impact on volume manufacturing is demonstrated. Index Terms-Semiconductor processing, contamination, nitrogen purge. Raymond van Roijen (M'13) received the B.S. degree in physics from the

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