Abstract
Diffusion barrier properties of electrochemically deposited Ni, Co, and Ni-Co alloys were examined in the Ni(Co)/Cu binary system and the Au/Ni/Cu ternary system. Ni and Co were electrodeposited from sulfate or sulfamate (Ni) solutions in the presence of boric acid, at pH 3.30, Electroless Ni and Co deposited either from sulfate or sulfamate solution using sodium hypophosphite or dimethylamine borane as the reducing agent. Electroless gold was deposited from cyanide solutions using potassium borohydride as the reducing agent. The deposits were annealed at 400°C for 14 h in a forming gas atmosphere (10% H2, 90% N2). Auger electron spectroscopy and electron probe analysis were used to assess the extent of interdiffusion as a result of the heat-treatment. Only electrolessly deposited 1000 A thick Ni, Co, and Ni-Co alloys have barrier properties for Cu diffusion. For Co(P) 1000 A thick barriers, annealed for 14 h, the amount of the interdiffused copper into Co(P) was less than 1 atomic percent. Thicker barriers of Ni(P), Ni(B), and Co(B) are required for the same degree of Cu diffusion. Ni(P) thin films deposited from nickel sulfamate solutions are better diffusion barriers than those deposited under the same experimental conditions, from nickel sulfate solutions. Electrochemically deposited barriers were compared with Ni, Co, and Cr barriers produced by evaporation. The differences between the diffusion barrier properties of Ni(P) deposited from the sulfamate and the sulfate solutions were interpreted in term of microstructural data and grain growth mechanism. © 1994, The Electrochemical Society, Inc. All rights reserved.