Investigating the root cause of WAC Vt fliers and Control plan for RF FEM : Yield Enhancement

We investigated and resolved the problem of WAC (wafer acceptable criteria) FET threshold voltage (Vt) fliers in a 130nm technology. Our investigation shows that failed Vt sites on the test maps are due to the incomplete resist removal at boron well implant level (P2 level). Test maps showed strong correlation with subsequent photo defect inspection (PDI) steps. PDI inspections show resist residue...