Film forming method, film forming apparatus, and storage medium

A film forming apparatus which forms a thin film formed of a metal oxide on a substrate by alternately supplying a raw material gas formed of an organic material containing a metal and an oxidation gas for oxidizing the organic material to the substrate a plurality of times, within a reaction vessel under a vacuum atmosphere, the film forming apparatus comprising:

• a vacuum-exhaust mechanism configured to exhaust an interior of the reaction vessel through an exhaust path;
• a moisture detection part configured to detect a moisture concentration in a gas flowing in the exhaust path;
• a substitution gas supply part configured to supply a substitution gas for substituting an internal atmosphere of the reaction vessel into the reaction vessel;
• and
• a control part configured to output a control signal for executing a step of supplying the raw material gas into the reaction vessel, a step of substituting the internal atmosphere of the reaction vessel with the substitution gas and then supplying the oxidation gas into the reaction vessel subsequent to the step of supplying the raw material gas, and an atmosphere substitution step including a step of supplying the substitution gas into the reaction vessel consecutively, and further output a control signal for comparing the moisture concentration detected by the moisture detection part with a set value after initiation of the step of supplying the oxidation gas and before starting the step of supplying the raw material gas, and when the moisture concentration exceeds the set value, for increasing a substitution operation of the atmosphere substitution step.