Method of obtaining output flow rate of flow rate controller and method of processing workpiece

A method of obtaining an output flow rate of a gas supply unit,

• wherein the gas supply unit includes
• a first pipe connected to a gas source,
• a flow rate controller provided downstream of the first pipe, and
• a second pipe provided downstream of the flow rate controller,
• wherein the flow rate controller includes an orifice, a first gas line located on an upstream side of the orifice and connected to the first pipe, and a second gas line located on a downstream side of the orifice and connected to the second pipe,
• wherein a first valve capable of adjusting a pressure in the second pipe is provided downstream of the second pipe, and
• wherein a tank is provided downstream of the first valve,
• the method comprising:
• outputting gas from the flow rate controller at an adjusted flow rate that is adjusted according to a designated set flow rate, in a state where the first valve is opened;
• depressurizing the second pipe so that a pressure of the first gas line becomes twice or more the pressure of the second gas line;
• obtaining a first output flow rate of the flow rate controller by using a pressure value and a temperature value in the tank;
• adjusting the first valve so that the pressure in the second pipe is a target pressure value, in a state where the outputting of the gas from the flow rate controller is continued, the target pressure value being set such that the pressure of the first gas line is less than twice the target pressure value;
• and
• obtaining a second output flow rate of the flow rate controller by using a pressure value and a temperature value in the tank, after the pressure in the second pipe is set to the target pressure value.