Effect of Azole-Free Inhibitors on Cu Dissolution in H2O2 and Non-H2O2 Based Wet Etching Solutions during Hard Mask Removal

In this work, the Cu etching behavior was investigated at an elevated temperature of 55°C with different formulated wet etching solutions, either with or without hydrogen peroxide (H 2 O 2 ) , to analyze their effectiveness on the Cu surface dissolution, wetting characteristics, and surface morphology during the metal hard mask stripping in the advanced BEOL process. Four azole-free corrosion inhibitors were selected and evaluated while BTA was considered as the standard reference. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) results showed that all azole-free inhibitors exhibited comparable or lower levels of copper dissolution relative to the reference formulation containing benzotriazole (BTA) and H 2 O 2 . Among these, Chem A showed the lowest copper dissolution. Field Emission Scanning Electron Microscopy (FE-SEM) further confirmed Chem A's superior performance by revealing a clean copper surface with no detectable organic residue and improved surface morphology. These combined results establish Chem A as the most effective azole-free corrosion inhibitor tested under the given conditions.