Substrate processing apparatus, substrate processing method, method of manufacturing semiconductor device and non-transitory computer-readable recording medium

A substrate processing apparatus comprising:

• a reaction tube in which a substrate is accommodated;
• a process gas supplier through which a process gas is supplied into the reaction tube;
• an exhauster through which the process gas is exhausted from the reaction tube;
• a first inert gas supply source configured to supply a first inert gas into the reaction tube;
• an exhaust gas process chamber connected to the exhauster and in which an exhausted process gas is subject to a process;
• a first inert gas supplier connected to the first inert gas supply source and configured to supply the first inert gas to the exhaust gas process chamber:
• a second inert gas supplier connected to a second inert gas supply source and configured to supply a second inert gas to the exhaust gas process chamber;
• an exhaust pipe through which a gas in the exhaust gas process chamber is exhausted;
• and
• a controller configured to control the first inert gas supplier and the second inert gas supplier such that the first inert gas is separately supplied to the exhaust gas process chamber and the reaction tube from the first inert gas supply source while the process gas is subject to the process in the exhaust gas process chamber and the second inert gas is supplied to the exhaust gas process chamber through the second inert gas supplier when the process in the exhaust gas process chamber is stopped, wherein the controller is further configured to calculate flow rate data of the second inert gas based on a flow rate of the process gas supplied through the process gas supplier,
• wherein the first inert gas supply source is connected to the reaction tube, and connected to the exhaust gas process chamber via the first inert gas supplier.