Abstract In semiconductor industry, planer analysis is important in many applications such as Passive Voltage Contrast (PVC) and sample preparation for nanoprobing. In order to achieve successful results on the planer surface analysis, a proper delayering technique is critical. As the thickness of metal line, via of Back-End-of Line (BEOL) and contact layer are getting thinner in advanced nodes, we observed convention hand polishing is facing major challenge in endpointing at exactly targeted layer and specific Region of Interest (ROI). In addition, Cobalt process starting from 5nm node brings additional challenges. Cobalt tends to be oxidized easily which becomes not friendly for nanoprobing. The alternative solution to produce good planar surface is to use Plasma Focus Ion Beam (PFIB) technique with patented DX gas assisted. PFIB changes the convention FA workflow and has been proven that the new workflow improves the efficiency of planar failure analysis such as PVC and nanoprobing sample preparation.