A method for reducing metal contamination performed after dry cleaning of a process chamber used for a film deposition process and before starting the film deposition process is provided. In the method, a temperature in the process chamber is changed from a first temperature during the dry cleaning to a film deposition temperature. Hydrogen and oxygen are activated in the vacuum chamber while supplying hydrogen and oxygen into the process chamber. An inside of the process chamber is coated by performing the film deposition process without a substrate in the process chamber after the step of activating hydrogen and oxygen.