Studies of cobalt thin films deposited by sputtering and MOCVD

Cobalt films were deposited on a Si wafer at substrate temperatures ranging from 50 to 200 °C by metal-organic chemical vapor deposition (MOCVD) using Co2(CO)8 as a precursor. As-deposited MOCVD Co films contained low impurity contents and were obtained as a microcrystalline structure compared to sputtered Co films. After annealing at 400 °C, the resistivity of a 100 nm thick MOCVD Co film decreased to about 6 μΩ cm. This was similar to the resistivity of bulk Co and lower than that of a sputtered Co film. The decrease in resistivity coincides with grain growth in the Co film. In addition, annealing at 300 °C produced a stronger (0 0 2) fiber texture in the MOCVD Co film compared to a sputtered Co film. Grain growth appears to be coupled to the strong (0 0 2) texture evolution, possibly indicating that surface energy minimization can be a driving force for grain growth in MOCVD Co films. Formation of Co oxide inhibited grain growth and led to a high resistivity of the sputtered Co films. CoSi2 was formed in MOCVD Co films whereas Co2Si was formed in the sputtered Co films after annealing at 700 °C.