Self-Aligned Deposition Process for Ultrathin Electroless Barriers and Copper Films on Low-k Dielectric Films

A self-aligned, integrated plating technique based on plasma physics and colloidal-related chemistry is proposed to fabricate patterns of ultrathin (≤20 nm) Co-based barriers and copper films in a selective manner on dielectric (HOSP™ and SiO₂) films using electroless plating. High-resolution X-ray absorption spectroscopy, transmission electron microscopy, and atomic force microscopy reveal that, once properly pretreated by a gaseous plasma (O₂ or H₂/N₂) and hydrogen peroxide (H₂O₂) in a basic aqueous solution, the dielectric films can adsorb highly populated metallic (Ni) precipitates of sizes approximately from 2 to 4 nm to catalyze the deposition of electroless Co-based barriers. Finally, the capability of this technique to fabricate "self-aligned" patterns of barrier and copper is demonstrated and the importance of the plasma pretreatment and hydrogen peroxide (in SC-1 solution) is discussed.