Defects caused by Sources other than Processing

We provide two examples of defects that caused real yield degradation on wafers, where the defects were not created during processing of the wafers. One is a case of a common non-process step unexpectedly causing a defect. The second is related to queue time, and shows that even in a modern highly controlled environment not all risks are always fully accounted for. We describe the mechanism behind the defects and provide specific solutions to the issues found. We also comment on the conditions that are most likely to make wafers susceptible to these defects and some guidelines that follow from these observations.