Front End-of-Line (FEOL) front side and back side defect investigations revealed a previously unknown back side defect mechanism that may negatively affected die sort yields. Using the AMAT SEMVision TM and Compass TM tools, the KLA-Tencor AIT TM and SP1 BSIM TM tools, and the JEOL SEM TM a detailed FEOL front side and back side defect partition showed that several defect mechanisms were operating in the FEOL and a previously unknown back side defect mechanism was newly identified. These new defects were large gouge/scratch type defects greater than 100 um and were found, prior to processing in our facility, on every incoming silicon wafer from several silicon substrate suppliers. The new back side defect data enabled the Si suppliers to identify the root cause to be a marginal furnace anneal process and marginal boat configuration at their various manufacturing sites. This FEOL back side defect characterization revealed a previously unknown defect mechanism that affected every production starting Si wafer from those suppliers and corrective actions are in place at each supplier sites to reduce and eliminate them.