Highly conformal deposition of pure Co films by MOCVD using Co₂(CO)₈as a precursor

Highly conformal Co thin films were deposited on Si O2 trenches with an aspect ratio of 13 by metallorganic chemical vapor deposition (MOCVD) using Co2 (CO)8 as a precursor in a low-temperature regime of 50-70°C where the growth rate was 3.5-7.0 nmmin. Lowering the pressure of the process reduces the number of collisions in the gas phase and, thus, widens the temperature regime in which the surface reaction controls the growth rate. A processing pressure of 26.7 Pa (0.2 Torr) allows for conformal deposition only at 50°C, whereas deposition at a reduced pressure of 4.0 Pa (0.03 Torr) widens the temperature regime (50-70°C) in which excellent conformality can be obtained. The conformal Co thin film, produced at 50°C and 4.0 Pa, showed a resistivity of 10-12 μ cm and contained 1.0 atom % oxygen and less than 1.0 atom % carbon. After annealing this film at 600°C, its resistivity was reduced to 6 μ cm, which is close to the bulk resistivity (5.7 μ cm) of Co. Therefore, this low-temperature process, which allows for the excellent conformal deposition of pure Co films, can be utilized to produce silicided contacts for advanced devices which require a low contact resistance and good electrical performance.