A method for increasing deposition rates of metal layers from metal-carbonyl precursors by mixing a vapor of the metal-carbonyl precursor with CO gas. The method includes providing a substrate in a process chamber of a deposition system, forming a process gas containing a metal-carbonyl precursor vapor and a CO gas, and exposing the substrate to the process gas to deposit a metal layer on the substrate by a thermal chemical vapor deposition process.
A CVD method for forming a metal film on a substrate by using a metal carbonyl gas includes a preparing step for setting a vacuum chamber at a vacuum pressure and heating the substrate in the vacuum chamber to a first temperature where the metal carbonyl gas is decomposed. Also included are a supplying step for supplying the metal carbonyl gas into the vacuum chamber while exhausting the vacuum chamber with a first vacuum pumping speed and a removing step for removing a decomposed gas of the metal carbonyl gas by stopping supplying of the metal carbonyl gas and quickly exhausting the vacuum chamber with a second vacuum pumping speed sufficiently higher than the first vacuum pumping speed. The supplying step and the removing step can be repeatedly as desired.