Electrochemically deposited ruthenium seed layer followed by copper electrochemical plating

Electrochemical deposition of ruthenium as a seed layer was investigated on Ti and TiN as barrier layers for Cu interconnects. The aqueous electrolyte, the N-bridged complex of ruthenium(IV) nitrosyl chloride (RuNC), for ruthenium electrochemical deposition was formed in situ. Electrochemical deposition of copper on the Ru seeded barrier layers was also demonstrated. The chemicals for the acid-bath ruthenium electrochemical deposition were ruthenium(III) chloride hydrate (RuCl₃ṡ3H₂O), hydrochloric acid (HCl), sulfamic acid (NH₂SO₃H), and polyethylene glycol. The chemicals for the acid-bath copper electrochemical deposition were copper(II) sulfate hydrate (CuSO₄ṡ5H₂O), sulfuric acid (H ₂SO₄), and polyethylene glycol. Results were analyzed by field-emission scanning electron microscopy, atomic force microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Rutherford backscattering spectrometry. The Ru thin layer with equiaxial grains <10 nm on blanket Ti substrates were obtained by electrochemical deposition. Electrochemical Cu trench fill was successful on patterned TiN 130 nm 2.5 aspect ratio trenches with Ru as a seed layer.