Characteristics of Cu films prepared using a magnetron sputter type negative ion source (MSNIS)

Cu films have been deposited at room temperature using a magnetron sputter type negative ion source (MSNIS) at various conditions. By the principle of operation, the negative ion production probability is the function of the Cs flow rate in MSNIS. A set of films were deposited at different Cs flow rates and compared with normal-magnetron-sputtered films. The long-throw method was combined to MSNIS to increase the directionality and the negative ion arrival ratio. The film properties such as resistivity, surface roughness, film structure and step coverage on high-aspect ratio trench samples were obtained and analyzed using SEM, SIMS and AFM methods. The results showed that the resistivity of the film improved toward the theoretical values from 2.3 μΩ cm to 1.8 μΩ cm for the 100 nm thickness films. AFM scan of the film showed surface roughness was improved using MSNIS by ion bombarding effect. Depth profiling SIMS result showed Cs level resided in the film was less than 1 × 1019 atom/cm3. As an application, Cu seed layer deposition on trench structure was investigated. Cross-sectional SEM was employed to see the step coverage of the film. The biasing effect was investigated. The different biasing conditions resulted as the clearly different coverage mode.