Chemical mechanical planarization of advanced package substrate by controlling selectivity of copper to polymer

Chemical mechanical planarization (CMP) was applied on an advanced package substrate by removing unnecessary polymer on a copper pillar since this could not be achieved through etching. Highly concentrated, non-spherical colloidal silica was used as slurry abrasive to improve the removal rate of the polymer, which is inert against chemical attack. When the polymer and copper were simultaneously polished at the end point, the selectivity of both materials was controlled by the slurry chemicals, which include an oxidizer, a complexing agent, and a corrosion inhibitor. Finally, optimum chemical components with 0.5, 1 and 0.5 wt% of hydrogen peroxide, glycine, and benzotriazole, respectively, were achieved, resulting in a step height of less than 25 nm.