Film forming method and film forming apparatus

A film forming method comprising:

• forming a film of a reaction product on a substrate in a processing container by alternately and repeatedly supplying, into the processing container, a raw material gas serving as a film formation raw material and a reaction gas that reacts with the raw material gas to produce the reaction product;
• purging an atmosphere in the processing container by supplying a purge gas into the processing container during each purge period between a first period in which one of the raw material gas and the reaction gas is supplied into the processing container and a subsequent second period in which the other of the raw material gas and the reaction gas is supplied into the processing container;
• and
• producing the reaction product on the substrate by supplying the other of the raw material gas and the reaction gas into the processing container during the second period following the first period, in a state where the one of the raw material gas and the reaction gas supplied into the processing container during the first period remains physically adsorbed onto the substrate, wherein the producing the reaction product is included in the forming the film.

A film forming apparatus comprising:

• a processing container configured to accommodate a substrate;
• a film formation gas supply configured to alternately and repeatedly supply, into the processing container, a raw material gas serving as a film formation raw material and a reaction gas that reacts with the raw material gas to produce a reaction product, in order to form a film of the reaction product on the substrate;
• a purge gas supply configured to supply, into the processing container, a purge gas, which purges an atmosphere in the processing container, during each purge period between a first period in which one of the raw material gas and the reaction gas is supplied into the processing container and a subsequent second period in which the other of the raw material gas and the reaction gas is supplied into the processing container;
• an exhaust path configured to exhaust an interior of the processing container;
• a valve provided in the exhaust path and configured to increase an exhaust amount from the processing container as an opening degree of the valve increases;
• and
• a controller configured to output a control signal such that the opening degree of the valve is set to a first opening degree until a midpoint of one of the first period and the second period, and is set to a second opening degree greater than the first opening degree from the midpoint to and during the subsequent purge period.