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Selective electroless metal deposition process was studied for its applications in integrated circuit fabrication. Compared to selective metal deposition by CVD process, such as the selective tungsten deposition process, the selective electroless deposition process is more attractive due to its simplicity as well as process flexibility. A variety of material such as Ni, Co, Pd, and Cu were studied for contact filling, via filling, and for conductor patterns. These materials were selectively deposited on a variety of surfaces such as silicon, silicide, A1-Si, through patterned CVD silicon dioxide, CVD silicon oxynitride, and photoresist. Although this process is still in its early stage of development, very promising results have already been achieved. The experimental conditions and results for selectively filled contact holes, via holes, and conductor patterns are described using actual examples.

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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. Eleetroless gold was deposited from cyanide solutions using potassium borohydride as the reducing agent. The deposits were annealed at 400~ for 14 h in a forming gas atmosphere (10% H2, 90% N2). Auger eiectron 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 microstruetural data and grain growth mechanism.