Wafer Edge Process Integration and Defect Inspection with the Immersion Lithography Process

Abstract

The study aims at the wafer edge engineering with defect reduction and the corresponding inline inspection methodology. The BARC (bottom anti-reflective coating) step of the immersion lithography in the front-end-of-the-line (FEOL) process was found that would lead to metal film peeling defects at the very later process in middle-end-of-the-line (MEOL). In this work, the wafer-edge inspection tool was used to scan the BARC profile in the wafer edge, including the front-side, apex and the back-side edges and which presents an effective inline routine monitor for EBR (edge bead removal) control of the BARC. The silicon residues were found after the etch process and caused by the bad edge BARC profile at wafer edge. The intrinsic stress of the Ti/N metal film would lead to the delamination and peel off from the wafer-edge silicon residue with poor adhesion. After cycles of experiments, an innovative bevel etching step with oxygen-based gas was added to tailoring the wafer edge profile after active area (AA) lithography, and the peeling defect dramatically trended down to zero.