Study on chemical-mechanical polishing of low dielectric constant polyimide thin films

In this study the polyimide CMP was explored for its feasibility on the IMD planarization applications. Polishing polyimide was carried out before its final curing, and the removal rates were found to be strongly dependent upon the imidization degree of polyimide and the hydroxyl activity in the slurry. TMAH, tetra-methyl-ammonium hydroxide, added into the slurry is not only a strong base, but also a wetting agent to improve the surface wettability on the hydrophobic polyimide surface. The surface damages, such as roughness and scratches, moisture uptake and mobile ions contamination of the polished polyimide were characterized for their influence on the insulating properties, like dielectric constant, leakage current, electrical breakdown. It was demonstrated that directly polyimide CMP would not deteriorate the dielectric properties.