The fab is almost always better off financially if it can find and fix the defect inline instead of at the end of line.
Defect inspection tools can be expensive. But regardless of the cost of the inspection tool needed to find a defect, the fab is almost always better off financially if it can find and fix that defect inline versus at the end of line (e.g., electrical test and failure analysis). Here, we are referring to the term defect in a general sense—the same concepts also apply to metrology measurements.
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