Cleaning method, method of manufacturing semiconductor device, and substrate processing apparatus

A cleaning method, comprising:

• removing a deposit adhering to an inside of a process container by supplying a cleaning gas into the process container after performing a process of forming a film on a substrate in the process container,
• wherein the removing the deposit includes repeatedly performing a cycle including:
• a first process of supplying the cleaning gas into the process container until a predetermined first pressure is reached in the process container;
• a second process of stopping the supplying the cleaning gas and exhausting the cleaning gas and a reaction product generated by the cleaning gas remaining in the process container;
• and
• a third process of cooling an exhaust pipe connected to the process container, while maintaining a pressure inside the process container at a second pressure, which is lower than the predetermined first pressure,
• wherein, for each cycle, a temperature of the exhaust pipe is detected,
• wherein, for each cycle, a duration of the third process is determined based on the detected temperature in a manner that:
• if the detected temperature is higher than a second temperature that is higher than a first temperature, the duration is extended until the temperature of the exhaust pipe becomes equal to or lower than the first temperature;
• and
• if the detected temperature is not higher than the second temperature, the duration is set to a predetermined time, and
• wherein the first process includes an operation of exhausting the cleaning gas to maintain the predetermined first pressure while continuing to supply the cleaning gas.