Substrate processing method and substrate processing apparatus

A substrate processing apparatus comprising:

• a processing container configured to process a substrate;
• a gas supply configured to supply a gas into the processing container;
• an exhaust port including an exhaust pipe configured to exhaust a gas from an inside of the processing container;
• a gas analyzer provided in a bypass pipe that bypasses the exhaust pipe and configured to analyze the gas passing through the exhaust pipe that connects the processing container and the exhaust port;
• and
• a controller configured to control an overall operation of the substrate processing apparatus,
• wherein the controller is configured to:
• perform a processing with a processing gas in the processing container by supplying the processing gas into the processing container;
• purge the processing gas in the processing container by supplying a purge gas into the processing container;
• analyze the processing gas passing through the bypass pipe from the exhaust pipe by the gas analyzer during the purging the processing gas, thereby measuring a concentration of the processing gas passing through the bypass pipe;
• and
• determine a condition of the purging the processing gas based on a result of measuring the concentration of the processing gas,
• wherein when the controller determines the condition, a purge time during which the purging is performed is determined based on a time frame in which the concentration of the processing gas measured during the purging by the gas analyzer continuously decreases to fall below a preset reference value, and
• the purge time is determined by adding a predetermined time to a time from when a supply of the processing gas stops to when the analysis value of the processing gas falls below the preset reference value.