Reducing Environmentally Induced Defects While Maintaining Productivity

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.