Gas supply apparatus and gas supply method

A gas supply apparatus for forming a film by sequentially supplying a source gas, a substitution gas, and a reaction gas to a substrate in a processing chamber under a vacuum atmosphere for a plurality of cycles, wherein the substitution gas substitutes an atmosphere, and the reaction gas reacts with the source gas and generates a reaction product on the substrate, the apparatus comprising:

• a source gas flow passage configured to supply the source gas into the processing chamber, a source gas supply control device being installed in the source gas flow passage;
• a reaction gas flow passage installed independently of the source gas flow passage, and configured to supply the reaction gas into the processing chamber, a reaction gas supply control device being installed in the reaction gas flow passage;
• a first carrier gas flow passage and a second carrier gas flow passage connected to the source gas flow passage and the reaction gas flow passage, respectively, and configured to supply a carrier gas, a carrier gas supply control device being installed in each of the first carrier gas flow passage and the second carrier gas flow passage, and a valve being installed in a downstream side of each of the first carrier gas flow passage and the second carrier gas flow passage;
• a substitution gas flow passage configured to supply the substitution gas into the processing chamber through a supply control device, the supply control device being different from the carrier gas supply control devices which are installed in the first carrier gas flow passage and the second carrier gas flow passage, and also being different from the source gas supply control device and the reaction gas supply control device;
• a substitution gas storage part installed in the substitution gas flow passage, and configured to store only the substitution gas;
• a valve installed in the substitution gas flow passage, and installed in a downstream side of the substitution gas storage part;
• and
• a control unit configured to control opening and closing of the valves such that after the substitution gas is stored in the substitution gas storage part to increase an internal pressure of the substitution gas storage part, the substitution gas is supplied into the processing chamber from the substitution gas storage part,
• wherein a first orifice and a second orifice are installed in a downstream side of the valve of the first carrier gas flow passage and a downstream side of the valve of the second carrier gas flow passage, respectively,
• wherein a diameter of the downstream side of the valve of the first carrier gas flow passage and a diameter of the downstream side of the valve of the second carrier gas flow passage are smaller than a diameter of an upstream side of the valve of the first carrier gas flow passage and a diameter of an upstream side of the valve of the second carrier gas flow passage, respectively, and are smaller than a diameter of the substitution gas flow passage;
• and
• wherein a time period during which the carrier gas is supplied into the processing chamber and a time period during which the substitution gas is supplied into the processing chamber overlap with each other.